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Urban Legacies and Soil Management Affect the Concentration and Speciation of Trace Metals in Los Angeles Community Garden Soils

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... These contaminants can remain stored in surface soils, be transported Editorial Responsibility: Kitae Baek to rivers, reservoirs, or coastal systems (e.g., Slotton and Reuter 1995;Chow et al. 1994;Schiff and Weisberg 1999), or eroded by wind generating potentially hazardous dust (Charlesworth et al. 2011;Mielke et al. 2010). Thus, accumulation and retention in soils can help prevent negative impacts to marine ecosystems (e.g., Katz and Kaplan 1981) and human health (e.g., Sabin et al. 2006;Hung et al. 2018), but could impact planted or native vegetation from overexposure through soil uptake (Page and Chang 1979;Adriano 2001;Clarke et al. 2015;Wang et al. 2015). ...
... However, soil concentrations at some sites exceeded interim final Ecological Soil Screening levels for mammals for Cd (0.36 mg/kg), Cr (34 mg/kg for Cr +3 ), Cu (49 mg/kg), Pb (56 mg/kg), and Zn (79 mg/kg). Soil Cd and As concentrations in our study were comparable to Cd (0.5-1.5 mg/kg) and As (2.5-17 mg/kg) soil concentrations observed in urban soils in Los Angeles observed by Clarke et al. (2015). However, our average Pb concentrations were lower than their observed concentrations which exceeded 200 mg/kg. ...
... However, our average Pb concentrations were lower than their observed concentrations which exceeded 200 mg/kg. This is to be expected as their sampling locations were near the urban center of Los Angeles and have longer historical land-uses before 1940 (Clarke et al. 2015). Only six of our fifty-four sites had Pb concentrations exceeding the 200 mg/kg concentration and were distributed across Los Angeles, San Bernardino, and Orange Counties as opposed to aggregated in a specific area. ...
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Purpose Southern California is a mega-metropolitan area with abundant air pollution, complex geology, and diverse Mediterranean ecosystems. The objective of this study was to evaluate trace metal and metalloids (TMMs) (As, Cd, Co, Cr Cu, Ni, Pb, U, V, Zn) in soils and foliage of peri-urban areas and explore potential effects from human-development, ecosystems, and geologic material. Materials and methods Foliage of dominant native vegetation, soil samples (0–20 cm), saprolite, and unweathered rock samples were collected across fifty-four sampling sites in foothills spanning coastal Los Angeles and Orange counties to inland San Bernardino and Riverside counties. Results and discussion Soil As, Cd, Cu, and Pb concentrations were regionally elevated, but not as elevated as point-source polluted sites elsewhere. Soil Cd, Cr, Cu, Pb, and Zn concentrations were above EPA Ecological Soil Screening Levels. Further, enrichment factors (EF) normalized to Ti concentrations in bedrock suggest minor to moderate As, Cd, Cr, Cu, Pb, and V accumulation in soils. Our foliar TMM concentrations and bioaccumulation factors (BAF) (foliar and soil ratio) indicate no bioaccumulation and limited effects across geologic, development intensity, and ecosystems groups. Conclusions Sedimentary-derived soils affected soil TMMs, but likely not through inheritance of TMMs but by promoting clay and organic matter availability. Proximity to higher development intensity resulted in As, Cd, Cr, Cu, and Pb accumulation in peri-urban soils. Foliar TMM concentrations and BAFs suggest geologic materials, human development, and ecosystem properties were not important factors and TMMs were likely controlled by plant uptake or ecophysiology.
... b Ecological processes within terrestrial, aquatic, and atmospheric settings contribute to health through both biometerological and ecohydrological interactions riskscapes can suddenly transform into acute and highly localized risks, for example health risks following urban flooding (Ahern et al. 2005). Some risks are strongly influenced by historical legacies and may persist for decades, such as soil contamination (Clarke et al. 2015), while others become more prominent during discrete events, such as heat waves (Li and Bou-Zeid 2013). In some cases hazards emerge from undetectable levels to epidemics through rapid organismal population growth rates, such as with some vector borne diseases (Johnson et al. 2015). ...
... Drivers of ecological contributions to health vulnerability comprise the nonhuman environment, active human management, and legacies of historical social conditions (Pickett et al. 2001). Environmental drivers, including climate, bedrock geology, and native biodiversity, have a prominent role in many ecological processes that affect health (Reiner et al. 2012;Clarke et al. 2015;Shiflett et al. 2017). Management activities resulting from human-induced modifications to environmental conditions, transport networks, and demographic characteristics of key species can also influence ecological processes (Johnson et al. 2015;Larsen 2015). ...
... Within any location, vegetation and soils may directly influence heat, diseases, and pollutant riskscapes by providing Fig. 3 Contrasting greenspaces in southern California, USA: unmanaged grassland (a), irrigated park (b), vacant lot (c), and community garden (d). The contribution to health among these contrasting systems may differ in response to vegetation and ecosystem characteristics vegetated cooling (Zhou et al. 2017), habitat for vector species (Hamilton et al. 2014), and opportunities for transforming or concentrating pollutants (Clarke et al. 2015), while at the same time providing benefits to well-being through greenspace exposure. Across a region, the overlapping and often independent landscape structure of individual hazards lead to a multifunctional landscape of health vulnerability. ...
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Context Ecological research, from organismal to global scales and spanning terrestrial, hydrologic, and atmospheric domains, can contribute more to reducing health vulnerabilities. At the same, ecological research directed to health vulnerabilities provides a problem-based unifying framework for urban ecologists. Objective Provide a framework for expanding ecological research to address human health vulnerabilities in cities. Methods I pose an urban ecology of human health framework that considers how the ecological contributions to health risks and benefits are driven by interacting influences of the environment, active management, and historical legacies in the context of ecological self-organization. The ecology of health framework is explored for contrasting examples including heat, vector borne diseases, pollution, and accessible greenspace both individually and in a multifunctional landscape perspective. Results Urban ecological processes affect human health vulnerability through contributions to multiple hazard and well-being pathways. The resulting multifunctional landscape of health vulnerability features prominent hotspots and regional injustices. A path forward to increase knowledge of the ecological contributions to health vulnerabilities includes increased participation in in interdisciplinary teams and applications of high resolution environmental sensing and modeling. Conclusions Research and management from a systems and landscape perspective of ecological processes is poised to help reduce urban health vulnerability and provide a better understanding of ecological dynamics in the Anthropocene.
... Cities are beginning to utilize their large organic waste streams by recycling them into low-Pb compost, which is a promising alternative source of high-quality growing material (City Soil, 2016;Fitzstevens et al., 2017;SF Rec & Parks, 2016). Soil management strategies like these can reduce risk of Pb exposure by lowering garden soil Pb concentrations below the neighborhood average (Clarke et al., 2015), but to truly practice safe and sustainable urban agriculture the garden Pb concentrations must be low enough to prevent negative health outcomes. ...
... The Pb health burden is ultimately governed by the fraction of Pb absorbed into the bloodstream, or bioavailable Pb, rather than total Pb in the soil. Since Pb bioavailability in urban soils can vary significantly (Zia et al., 2011), recent studies are framing soil exposure risk in terms of bioavailable Pb instead of the total soil Pb Clarke et al., 2015;Fitzstevens et al., 2017;Henry et al., 2015). We measure in vitro bioaccessible Pb, or the Pb that is soluble in simulated gastric fluid, as a time and resource efficient proxy for in vivo bioavailable Pb (Zia et al., 2011). ...
... Previous studies have shown that compost dilutes total soil Pb concentrations Clark et al., 2008;Clarke et al., 2015;Fitzstevens et al., 2017). Since total Pb is directly proportional to bioaccessible Pb and compost binds Pb more effectively than soil, compost application also reduces urban gardeners' exposure to bioaccessible Pb through dilution and limiting Pb solubility (Table 1). ...
Article
Chronic low-level lead exposure among low-income minority children is an urgent environmental justice issue. Addressing this ubiquitous urban public health crisis requires a new transdisciplinary paradigm. The primary goals of this work are to inform best practices for urban gardeners working in lead contaminated soils and to reimagine urban organic waste management schemes to produce compost, which when covering or mixed with urban soil, could minimize lead exposure. We investigate bulk and bioaccessible lead from five types of compost used in urban gardens in Boston, MA. We categorized them by feedstock and measured bulk elemental concentrations and physical characteristics. Our results show that different feedstocks exhibit unique geochemical fingerprints. While bulk lead concentrations in compost are a fraction of what is typical for urban soils, the bioaccessible lead fraction in compost is greater than the default parameters for the Integrated Exposure Uptake Biokinetic (IEUBK) model. The lack of geochemical differences across feedstocks for lead sorption to carbon indicates a similar sorption mechanism for all compost. This suggests that municipal compost would be suitable for capping lead contaminated urban soils. Risk assessment models should consider lead bioaccessibility, to prevent the underprediction of exposure risk, and should include compost along with soils as urban matrices. Based on the observed bioaccessibility in our compost samples, 170 mg/kg total lead in compost will yield the same bioaccessible lead as the IEUBK model predicts for the 400 mg/kg EPA soil lead benchmark. Local logistical challenges remain for interdisciplinary teams of city planners, exposure scientists, and urban agricultural communities to design organic waste collection practices to produce compost that will support urban agriculture and primary lead exposure prevention.
... Cities are beginning to utilize their large organic waste streams by recycling them into low-Pb compost, which is a promising alternative source of high quality growing material [City Soil, 2016;SF Rec & Parks, 2016;Fitzstevens et al., 2017]. Soil management strategies like these can reduce risk of Pb exposure by lowering garden soil Pb concentrations below the neighborhood average [Clarke et al., 2015], but to truly practice safe and sustainable urban agriculture the garden Pb concentrations must be low enough to prevent negative health outcomes. ...
... The Pb health burden is ultimately governed by the fraction of Pb absorbed into the bloodstream, or bioavailable Pb, rather than total Pb in the soil. Since Pb bioavailability in urban soils can vary significantly [Zia et al., 2011], recent studies are framing soil exposure risk in terms of bioavailable Pb instead of the total soil Pb Clarke et al., 2015;Henry et al., 2015;Fitzstevens et al., 2017]. We measure in-vitro bioaccessible Pb, or the Pb that is soluble in simulated gastric fluid, as a time and resource efficient proxy for invivo bioavailable Pb [Zia et al., 2011]. ...
... Previous studies have shown that compost dilutes total soil Pb concentrations [Clark et al., 2008;Attanayake et al., 2015;Clarke et al., 2015;Fitzstevens et al., 2017]. Since total Pb is directly proportional to bioaccessible Pb and compost binds Pb more effectively than soil, compost application also reduces urban gardeners' exposure to bioaccessible Pb through dilution and limiting Pb solubility (Table 1). ...
Article
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While the presence of legacy lead (Pb) in the urban soil is well documented, less is known about the bioaccessibility, transport, and exposure pathways of urban soil Pb. We study Pb bioaccessibility in Roxbury and Dorchester, MA urban gardens to assess exposure risk and identify remediation strategies, applicable locally and in urban gardens across the country. We work in partnership with The Food Project, which brings the goals and perspectives of local farmers to the center of the research process and enables efficient local application of results to reduce Pb exposure. We measure changes in Pb bioaccessibility as a function of growing material, grain size, and Pb source. In comparison to soils, compost has lower total Pb concentrations, has lower Pb solubility in gastric fluid, and limits fine particle resuspension. The mean bioaccessible Pb concentration of compost is 265 mg/kg, nearly an order of magnitude lower than that of soils, and compost contains 14% higher carbon content than soils, which may account for the observed 19% lower Pb bioaccessibility in compost. For all matrices (soil, raised bed fill, and compost) grain sizes <37 μm contain a disproportionate fraction of the total pool of bioaccessible Pb. Furthermore, the isotopic composition of Pb in the size fractions linked with resuspension and elevated BLLs is indicative of leaded gasoline and leaded paint even decades removed from the primary deposition of these sources.
... The United States Agency for Toxic Substances and Disease Registry (USATSDR) ranks certain metals (e.g., As, Pb, Cd, Cr) as priority pollutants for known health effects [1]. Polluted air can typically contain NO x , SO x , CO 2 , aerosols, particulate matter (PM 10 , PM 2.5 ), heavy ("trace") metals, and organic pollutants from sources of fossil fuel activities [2,3]. Some metals (e.g., Pb, Cd, Cr) are known to be hazardous because of bioaccumulation and long retention times in tissues of living organisms, including humans [2]. ...
... (2) Identify and quantify NO 3 − in lichen biomass. Objectives of this study were to identify transport related patterns for metals and NO 3 − enrichment (pollution) within the Las Vegas valley. ...
... First, a portion of each lichen (~1 g) was measured into a clean, disposable bottle, brought to volume (50 mL) with 95 • C deionized water (DI), capped, agitated for two hours and allowed to cool to room temperature. After agitation, samples were allowed to settle then filtered through a Whatman 42 ® filter paper and measured immediately for NO 3 − by ion-selective electrode (ISE). During the extraction procedure, bottles were capped immediately after the sample was measured into the bottle, DI water added, agitated, filtered and measured for NO 3 − immediately by the ISE after filtering to reduce erroneous measurements due to NO 3 − uptake during the procedure. ...
Article
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Hazardous substances (e.g., toxic elements, oxides of nitrogen, carbon and sulfur) are discharged to the environment by a number of natural and anthropogenic activities. Anthropogenic air pollution commonly contains trace elements derived from contaminants and additives released into the atmosphere during fossil fuel combustion (automobiles, power generation, etc.) as well as physical processes (e.g., metal refining, vehicle brake wear, and tire and pavement wear). Analysis of pollutant chemical concentrations in lichens collected across the Las Vegas Valley allows documentation of the distribution of air pollution in the Valley. Analyses of lichen biomass (Buellia dispersa), when compared to windrose diagrams, shows pathways of airborne pollutant transport across the Las Vegas Valley. The west and north sectors of the Las Vegas Valley contained the lowest target contaminates (e.g., Cr, Cu, Co, Pb, Ni) and the highest NO3 while the east and south sectors contained the highest levels of target contaminates and lowest NO3. Additionally, metals and NO3 detected in the east and south sectors of the valley indicate that air pollution generated in the valley is moving from the south to the north-northeast and across the valley, exiting on the north and south side of Frenchman Mountain.
... Urban agriculture can contribute to improving food security, reducing greenhouse gas emissions (by reducing food miles) and providing social benefits, with verges contributing through community programs or unofficial " guerrilla " gardening (Hunter and Brown, 2012; Adams and Hardman, 2013). These contributions are currently negligible in the UK, partly due to food safety concerns regarding contamination by pollutants (Clarke et al., 2015). This may be less of a risk than typically perceived (Brown et al., 2016). ...
... This may be less of a risk than typically perceived (Brown et al., 2016). Fruit and nuts harvested from street trees are likely to be safe for consumption (von Hoffen and S€ aumel, 2014) and, although food crops grown in road verge soils may exceed critical pollutant safety values (S€ aumel et al., 2012), cultivated urban soils show lower levels of contamination than uncultivated soils (Clarke et al., 2015) and the erection of barriers, either artificial or planted, can greatly reduce pollutant loads (S€ aumel et al., 2012 ). Local authorities have been encouraged to support local community " guerrilla " gardening (Adams and Hardman, 2013) due to their strong social benefits (Crane et al., 2012; Anderson, 2014) allowing people to engage with their local community, enhancing cultural ecosystem service provision. ...
Article
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Urban road verges can contain significant biodiversity, contribute to structural connectivity between other urban greenspaces, and due to their proximity to road traffic are well placed to provide ecosystem services. Using the UK as a case study we review and critically evaluate a broad range of evidence to assess how this considerable potential can be enhanced despite financial, contractual and public opinion constraints. Reduced mowing frequency and other alterations would enhance biodiversity, aesthetics and pollination services, whilst delivering costs savings and potentially being publically acceptable. Retaining mature trees and planting additional ones is favourable to residents and would enhance biodiversity, pollution and climate regulation, carbon storage, and stormwater management. Optimising these services requires improved selection of tree species, and creating a more diverse tree stock. Due to establishment costs additional tree planting and maintenance could benefit from payment for ecosystem service schemes. Verges could also provide areas for cultivation of biofuels and possibly food production. Maximising the contribution of verges to urban biodiversity and ecosystem services is economical and becoming an increasingly urgent priority as the road network expands and other urban greenspace is lost, requiring enhancement of existing greenspace to facilitate sustainable urban development.
... Higher relative concentrations of Pb and other trace elements in the DTES and Commercial Drive/Renfrew sectors are probably related to higher urban density and Port of Vancouver activities. For Pb concentrations in particular, high ship traffic (Burrard Inlet (Fig. 1) often hosts around a dozen anchored cargo ships), motor vehicle traffic (DTES was already one of the most populated neighbourhoods when leaded gasoline was in use: 1920s-1993 in Canada), old paint, proximity to railway yards, and other light industrial activities are all expected to contribute to higher amounts of Pb downtown 50 . Other trace metals associated with anthropogenic activities (including Ba, As, Cd, Cu, Ni and Zn) are found in generally higher concentrations in soils, aerosols and runoff water in areas of greater urban density [50][51][52][53][54][55] , accounting for the systematic trace element variations (that is, higher concentrations downtown) observed between sectors in GVRD honey. ...
... For Pb concentrations in particular, high ship traffic (Burrard Inlet (Fig. 1) often hosts around a dozen anchored cargo ships), motor vehicle traffic (DTES was already one of the most populated neighbourhoods when leaded gasoline was in use: 1920s-1993 in Canada), old paint, proximity to railway yards, and other light industrial activities are all expected to contribute to higher amounts of Pb downtown 50 . Other trace metals associated with anthropogenic activities (including Ba, As, Cd, Cu, Ni and Zn) are found in generally higher concentrations in soils, aerosols and runoff water in areas of greater urban density [50][51][52][53][54][55] , accounting for the systematic trace element variations (that is, higher concentrations downtown) observed between sectors in GVRD honey. Idling and slower vehicular traffic might account for elevated trace metal concentrations downtown, since Vancouver does not have a direct highway network to the downtown area. ...
Presentation
Rapid developments in the emerging field of urban geochemistry warrant the use of trace element and isotopic analyses on a number of key bioindicators to determine source apportionment, transport, and fate of (heavy) metal pollutants. Honey from the European honey bee (Apis mellifera) has long been used as a bioindicator to assess environmental exposure to inorganic and organic anthropogenic contaminants (e.g., heavy metals and pesticides) and continues to help elucidate small-scale pollutant distribution. Most recently, Pb isotopic analyses on digested honey samples from urban settings has proven to be a promising development in the use of honey as a bioindicator, aiding in Pb source apportionment. In collaboration with a local non-profit group of urban apiarists in Vancouver, BC (Hives for Humanity), we collected, digested, and analysed honey to investigate pollutants from varied zoning districts: urban, industrial, residential, and agricultural. Variations in trace element and Pb isotopic compositions of the honey reflect proximity to anthropogenic metal sources related to land use, such as shipping ports and heavy traffic. For regional context, we have extended the study to include local fish to assess the sources of metals in the food chain, and have found that tissue from local salmon has a Pb isotope composition similar to that of the downtown honey. The project was received with great interest in the general community, leading to a shift in the honey collection method toward a ‘citizen science’ approach. We have shared clean sampling protocol and supplies with collaborators around the world, and have gathered honey from other urban centres including Grenoble and Brussels. Applications of modern geochemical analytical techniques for new bioindicators like honey help open new pathways for effective environmental assessment. Multifaceted studies like ours demonstrate the value of interdisciplinary collaboration when addressing issues within geochemistry, urban ecology, community awareness, and public health.
... Weathering of building materials might effectively contribute to TE contamination of KG soils, especially with materials from buildings constructed before 1920 due to, for example, the uses of Pb-containing paints in the past (Ashrafzadeh et al., 2018;Kandic et al., 2019;Norra et al., 2001;Turnbull et al., 2019). Allotments and community gardens are often located in vacant lots where industries were dismantled and buildings destroyed (Chaney et al., 1984;Clarke et al., 2015;Warming et al., 2015). Metal-containing waste materials (e.g., electric cables, batteries, paint scraping) can be buried (Alloway, 2004;Yu et al., 2018) and TEs consequently released owing to oxidizing soil conditions. ...
... These ashes resulting from the burning of wood and other materials can indeed enhance the contamination of KG soils by Pb, Cr, As, Cu, Cr, Cd, and Zn (Alloway, 2004;Meuser, 2010). Trace element pollution through atmospheric depositions due to urbanization (e.g., road traffic, domestic and industrial heating, incinerators), and contaminated soil particles also contributes to a large extent to the TE input in KG soils (Clarke et al., 2015;Douay et al., 2008;Gupta et al., 2019;Kandic et al., 2019;Meuser, 2010;Szolnoki et al., 2013). ...
Article
Trace element contaminants in kitchen garden soils can contribute to human exposure through the consumption of homegrown vegetables. In urban areas, these soils can be contaminated to various degrees by trace element (TE). They are characterized by a great variability in their physicochemical parameters due to the high anthropization level, the wide variety and combination of disturbance sources, as well as the diversity of cultivation practices and the large range of contamination levels. Pollutants can be taken up by vegetables cultivated in these soils and be concentrated in their edible parts. In this review, the behavior of vegetables cultivated in contaminated kitchen gardens is assessed through six examples of the most widely cultivated vegetables (lettuce, tomato, bean, carrot, radish, potato). The role of soil parameters that could influence the uptake of As, Cd, Cr, Ni, Pb, and Zn by these vegetables is also discussed.
... This threshold value serves only as an "alert signal", above which a more detailed investigation is required (Baize 1997(Baize , 2000. However, as in France, no legislation determines limit values for soil metal pollution, contrary to some other countries like Hungary (Szolnoki et al. 2013) or the USA (EPA 2003;Mitchell et al. 2014;Clarke et al. 2015). Most of time, threshold levels used in France correspond to the Decree of 8 January 1998 (Arrêté 1998-06-03 art. 1 JORF 30 June 1998), concerning limit values of agricultural soil contents for the spreading of urban sludge which is often, although wrongly, used as a surrogate for soil pollution (Cortet et al., 2011). ...
... Our results indicate multiple contaminations, except for Co, Cr, and Ni, with different distribution patterns for each metal and for each city. Cadmium, Cu, Pb, and Zn concentrations tend to increase together in urban vegetable gardens, as shown in Los Angeles gardens (Clarke et al. 2015) and urban forests and lawns (Foti et al. 2017). These results agree with previous studies of soil contamination with various land uses (industrial, agriculture, urban or forest), which demonstrated contamination in increasing quantities: Cd > Cu > Pb > Zn (Thiry et al. 2002;Cambier et al. 2009). ...
Article
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PurposeUrban soil contamination by heavy metals is one of the foremost challenges for urban soil quality, especially in the urban agriculture context. Urban gardening is a common practice in many industrialized and developing countries. How sources of soil contamination relate to inputs and influence the heavy metal content in soils, however, is not established yet.Materials and methodsThis study aims to assess the potential of pesticide applications (such as Bordeaux mixture) on soil quality. A set of 104 allotment gardens was selected in three cities in France, and topsoil was sampled and analyzed.Results and discussionThe four most abundant metals in urban vegetable garden topsoils were Zn, Pb, Cu, and Cr. The past and/or present industrial and urban activities are not the only cause of the metal contamination in urban vegetable garden soils. Gardens, where pesticides such as the Bordeaux mixture are being used showed significantly higher total Cu values in soils (78 mg kg−1 compared with 49 mg kg−1 for untreated gardens).Conclusions Even though the risk of metal contamination through vegetable consumption is usually considered low, we clearly identified indicators of anthropogenic Cd, Cu, Pb, and Zn pollution due to pesticides inputs. This link was particularly strong between the use of Bordeaux mixture and increases Cu levels.
... Zhang et al. [7] identified that Cr, Cu, Zn, As, Cd and Pb in roadside soil 2 of 11 along the Qinghai-Tibet highway were related to traffic emission and their concentration decreased exponentially with the distance from the road. Relationship between the distance to the road and the concentrations of heavy metals in roadside soils has been the most widely studied [8,9]. It was recognized that roadside contamination in soils caused by traffic did not extend much more than 20 m away from the road [10]. ...
... Soil properties including pH and organic matter content, prevailing wind direction, vegetation cover, and traffic intensity, etc. are important factors impacting the accumulation of heavy metals in soils [9,10,19]. The study by Kocher et al. [22] showed that the pH in roadside soil would increase to neutral or even above neutral levels due to road abrasion. ...
Article
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Heavy metal contamination in roadside soil due to traffic emission has been recognized for a long time. However, seldom has been reported regarding identification of critical factors influencing the accumulation of heavy metals in urban roadside soils due to the frequent disturbances such as the repair of damaged roads and green belt maintanance. Heavy metals in the roadside soils of 45 roads in Xihu district, Hangzhou city were investigated. Results suggested the accumulation of Cu, Pb, Cd, Cr, and Zn in roadside soil was affected by human activity. However, only two sites had Pb and Zn excessing the standards for residential areas, respectively, according to Chinese Environmental Quality Standards for soils. The concentrations of Cu, Pb, Cd, and Zn were significantly and positively correlated to soil pH and organic matter. An insignificant correlation between the age of the roads or vegetation cover types and the concentration of heavy metals was found although they were reported closely relating to the accumulation of heavy metals in roadside soils of highways. The highest Pb, Cd, and Cr taking place in sites with heavy traffic and significant differences in the concentrations of Cu, Pb, Cd, and Zn among the different categories of roads suggested the contribution of traffic intensity. However, it was difficult to establish a quantitative relationship between traffic intensity and the concentrations of heavy metals in the roadside soil. It could be concluded that impaction of traffic emission on the accumulation of heavy metals in roadside soils in urban area was slight and soil properties such as pH and organic matters were critical factors influencing the retention of heavy metals in soils.
... However, studies also showed that Cr and Ni were attributed to the industrial and transportation sources (Nazzal et al., 2015;Liu et al., 2016b). Other trace metal emission sources include urban legacies, previous agricultural activities, and soil management also influenced soil trace metal accumulations (Clarke et al., 2015). Furthermore, the existing urban soil studies mainly focused on lands for recreational, sporting or economic activities, such as playgrounds, shopping plazas and sport facilities (Khan et al., 2016;Rozanski et al., 2018), residential areas, public parks (Nezat et al., 2017;Gu and Gao, 2018), brownfields (Qian et al., 2017), industrial lands (Wu et al., 2018), and roadsides (De Silva et al., 2016). ...
... Several environmental factors are believed to be responsible for elevated soil trace metal concentrations in an urban environment. These include trace metal deposition, retention and solubility at different scales (Fritsch et al., 2010;, climate, parent materials, human population activities (Liu et al., 2016c), soil physiochemical properties (Navarrete et al., 2017), landscape patterns (Li et al., 2017a), urban legacies (Nezat et al., 2017), previous agricultural activities and soil management (Clarke et al., 2015). The dominated factors affecting the soil contamination process vary greatly in both time and space Liu et al., 2016b;Navarrete et al., 2017). ...
... Higher relative concentrations of Pb and other trace elements in the DTES and Commercial Drive/Renfrew sectors are probably related to higher urban density and Port of Vancouver activities. For Pb concentrations in particular, high ship traffic (Burrard Inlet (Fig. 1) often hosts around a dozen anchored cargo ships), motor vehicle traffic (DTES was already one of the most populated neighbourhoods when leaded gasoline was in use: 1920s-1993 in Canada), old paint, proximity to railway yards, and other light industrial activities are all expected to contribute to higher amounts of Pb downtown 50 . Other trace metals associated with anthropogenic activities (including Ba, As, Cd, Cu, Ni and Zn) are found in generally higher concentrations in soils, aerosols and runoff water in areas of greater urban density [50][51][52][53][54][55] , accounting for the systematic trace element variations (that is, higher concentrations downtown) observed between sectors in GVRD honey. ...
... For Pb concentrations in particular, high ship traffic (Burrard Inlet (Fig. 1) often hosts around a dozen anchored cargo ships), motor vehicle traffic (DTES was already one of the most populated neighbourhoods when leaded gasoline was in use: 1920s-1993 in Canada), old paint, proximity to railway yards, and other light industrial activities are all expected to contribute to higher amounts of Pb downtown 50 . Other trace metals associated with anthropogenic activities (including Ba, As, Cd, Cu, Ni and Zn) are found in generally higher concentrations in soils, aerosols and runoff water in areas of greater urban density [50][51][52][53][54][55] , accounting for the systematic trace element variations (that is, higher concentrations downtown) observed between sectors in GVRD honey. Idling and slower vehicular traffic might account for elevated trace metal concentrations downtown, since Vancouver does not have a direct highway network to the downtown area. ...
Article
Full-text available
Urban geochemistry is an emerging field in which key scientific and societal challenges, including rapid urbanization and population growth, compel investigation of readily accessible biomonitors to determine the source, transport and fate of heavy metal pollutants in cities. Lead isotopic analyses of honey have recently proven its efficacy as a biomonitor for Pb source apportionment applications. We collected honey directly from hives in six geographical sectors in Vancouver, British Columbia (Canada) to investigate the presence of potential pollutants from varying zoning districts: urban, industrial, residential and agricultural. Systematic variations in trace element concentrations and Pb isotopic compositions of the honeys reflect proximity to anthropogenic land-use activities such as shipping ports and heavy traffic. Honey sampled from downtown hives, near the Port of Vancouver, shows elevated trace element concentrations compared with suburban and rural honey, and distinctly higher 208Pb/206Pb (that is, less radiogenic) compared with local environmental proxies (for example, oysters, Fraser River sediment and volcanic rocks), indicating possible input from Asian anthropogenic sources. This study presents the first Pb isotope data for North American honey, and supports the combined use of trace elements and Pb isotopic compositions in honey as a geochemical biomonitor. https://www.nature.com/articles/s41893-019-0243-0 https://science.ubc.ca/news/honey-bees-can-help-monitor-pollution-cities
... Like natural systems (Wolkovich et al., 2014;Zelnik et al., 2018), the temporal dimensions and dynamics of urban land are most likely to affect their intrinsic functioning, sustainability, and resilience (Ramalho and Hobbs, 2012). For instance, the signatures of urban and rural past can be found in the very soil where modern cities sit; silent legacies of previous land use and change (Clarke et al., 2015). Time represents an important, yet poorly understood, factor driving all urban events and their dynamics, dictating the pace and direction of change and ultimately affecting the ecology of future urban ecosystems. ...
... Among the existing evidence on the effects of urban time, legacies are perhaps the most commonly studied though not fully understood or identified. Legacies of former urban land use have been documented by measuring contamination of contemporary soil with pollutants since banned (Nassauer and Raskin, 2014;Clarke et al., 2015), as well as changes in soil physical and chemical properties, and ecosystem services (Raciti et al., 2011;Setälä et al., 2016;Ziter and Turner, 2018). Effects of former urban planning efforts dictate the structure of contemporary urban forests (Figure 6), as well the benefits they provide to residents (Boone et al., 2010). ...
Article
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Cities and towns are complex ecosystems with features that can vary dramatically in space and time. Our knowledge of the spatial structure of urban land and ecological systems is expanding. These systems have been investigated across spatial scales, urban to rural gradients, networks of urban macrosystems, and global megalopolises. However, the temporal dimensions of urban ecosystems – such as those related to ecological cycles and historical legacies – are far less understood and investigated. Here, we outline the main dimensions of time that can shape how events in urban ecosystems unfold, which we categorize as: (i) time flows and duration, (ii) synchrony, lags, and delays, (iii) trends and transitions, (iv) cycles and hysteresis, (v) legacies and priming, (vi) temporal hotspots and hot moments, and (vii) stochastic vs. deterministic processes affecting our ability to forecast the future of cities and the species that live in them. First, we demonstrate the roles of these understudied dimensions by discussing exemplary studies. We then propose key future research directions for investigating how processes over time may regulate the structure and functioning of urban land and biodiversity, as well as its effects on and implications for urban ecology. Our analysis and conceptual framework highlights that several temporal dimensions of urban ecosystems – like those related to temporal hotspots/moments and stochastic vs. deterministic processes – are understudied. This offers important research opportunities to further urban ecology and a comprehensive research agenda valuing the “ Urban Chronos ” – the change of urban ecosystems through time.
... Higher relative concentrations of Pb and other trace elements in the DTES and Commercial Drive/Renfrew sectors are probably related to higher urban density and Port of Vancouver activities. For Pb concentrations in particular, high ship traffic (Burrard Inlet (Fig. 1) often hosts around a dozen anchored cargo ships), motor vehicle traffic (DTES was already one of the most populated neighbourhoods when leaded gasoline was in use: 1920s-1993 in Canada), old paint, proximity to railway yards, and other light industrial activities are all expected to contribute to higher amounts of Pb downtown 50 . Other trace metals associated with anthropogenic activities (including Ba, As, Cd, Cu, Ni and Zn) are found in generally higher concentrations in soils, aerosols and runoff water in areas of greater urban density [50][51][52][53][54][55] , accounting for the systematic trace element variations (that is, higher concentrations downtown) observed between sectors in GVRD honey. ...
... For Pb concentrations in particular, high ship traffic (Burrard Inlet (Fig. 1) often hosts around a dozen anchored cargo ships), motor vehicle traffic (DTES was already one of the most populated neighbourhoods when leaded gasoline was in use: 1920s-1993 in Canada), old paint, proximity to railway yards, and other light industrial activities are all expected to contribute to higher amounts of Pb downtown 50 . Other trace metals associated with anthropogenic activities (including Ba, As, Cd, Cu, Ni and Zn) are found in generally higher concentrations in soils, aerosols and runoff water in areas of greater urban density [50][51][52][53][54][55] , accounting for the systematic trace element variations (that is, higher concentrations downtown) observed between sectors in GVRD honey. Idling and slower vehicular traffic might account for elevated trace metal concentrations downtown, since Vancouver does not have a direct highway network to the downtown area. ...
... Over the last decade, concerns over community garden contamination have gradually increased and a large number of studies have been carried out testing the levels of toxicants such as heavy metals in soil of plots. Much of this research has focused on urban gardens, because they have greater exposure to more contaminated dust in the environment or because they were previously used for purposes that led to its contamination with toxicants, what is known as brownfields, and then converted to community gardens [15,[58][59][60]. A Los Angeles survey of 12 different community gardens within the city supports concerns of contaminated soils in urban gardens [15]. ...
... Much of this research has focused on urban gardens, because they have greater exposure to more contaminated dust in the environment or because they were previously used for purposes that led to its contamination with toxicants, what is known as brownfields, and then converted to community gardens [15,[58][59][60]. A Los Angeles survey of 12 different community gardens within the city supports concerns of contaminated soils in urban gardens [15]. The study suggested that high concentrations of heavy metals such as lead (Pb), arsenic (As), and cadmium (Cd) are present in urban community gardens. ...
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Purpose of review: The purpose of this paper was to summarize current findings on community gardens relevant to three specific areas of interest as follows: (1) health benefits, (2) garden interventions in developing versus developed countries, and (3) the concerns and risks of community gardening. Recent findings: Community gardens are a reemerging phenomenon in many low- and high-income urban neighborhoods to address the common risk factors of modern lifestyle. Community gardens are not limited to developed countries. They also exist in developing low-income countries but usually serve a different purpose of food security. Despite their benefits, community gardens can become a source of environmental toxicants from the soil of mostly empty lands that might have been contaminated by toxicants in the past. Therefore, caution should be taken about gardening practices and the types of foods to be grown on such soil if there was evidence of contamination. We present community gardens as additional solutions to the epidemic of chronic diseases in low-income urban communities and how it can have a positive physical, mental and social impact among participants. On balance, the benefits of engaging in community gardens are likely to outweigh the potential risk that can be remedied. Quantitative population studies are needed to provide evidence of the benefits and health impacts versus potential harms from community gardens.
... As urban gardening becomes more popular, concerns have been raised in regard to soil safety particularly levels of lead and other trace metals (Finster et al., 2004;Mitchell et al., 2014;Bugdalski et al., 2014;Spliethoff et al., 2016). In particular, studies have indicated that concentration of trace metal is often associated with proximity to roads and high traffic areas (Clarke et al., 2015;Säumel et al., 2012). This concern presents another argument for integrating community gardens into public parks where park planting can function as barriers between crop beds and roads or areas with high automobile traffic. ...
Article
With rising interest in urban agriculture and urban food issues, community gardens have become an increasingly welcomed feature of urban landscapes. Reflecting this growing interest and demand, there has been a corresponding shift from temporary occupation of vacant sites to integration of community gardens into urban parks system. Such integration holds significant opportunities for community gardens to achieve stability, expand their overall footprint, and become a more integral part of the urban built environment. But as community gardens become a more accepted feature of public parks, what are some of the key issues and challenges of integration? How can community gardens thrive under a different spatial and institutional framework that governs public parks? Using Seattle as a case study where integration of community gardens into public parks has a long history as well as significant recent growth, this article examines lessons and challenges of such integration. Specifically, it identifies lessons including the clarity of roles and responsibilities of different agencies and the importance of collaboration and partnership as well as participatory site planning and design. It also points to perception of community gardens as private use and spatial and programming conflicts between gardening and other park uses as continued challenges.
... Moreover, the road dust containing trace elements could also deposit in the vegetable soils under the effect of heavy traffic (Werkenthin et al. 2014). Many researches have observed the negative relationship between trace element concentrations and the distance to road (Clarke et al. 2015;Wang et al. 2017a;Yan et al. 2013;Zhang et al. 2015). However, we did not find this relationship based on our data (Table S2). ...
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Trace element contamination in soils of vegetable fields can threat public health. Seven potential toxic elements (As, Cd, Cr, Cu, Ni, Pb, and Zn) in suburban vegetable soils of Chengdu city, Southwest China, in 2012 and 2016, were analyzed to identify their sources with the spatiotemporal variation and assess their contamination and health risk for residents. The results showed that the concentrations of soil elements did not increase significantly in 2016 compared with that in 2012, whereas their spatial distributions altered markedly. The hot spots of soil As, Cd, and Pb as well as Cu and Zn in 2016 revealed the anthropogenic sources including agricultural activities, industrial emissions, road dust with heavy traffic, and open burning of solid waste. The apparent spatial difference of anthropogenic elements was related to the layout of land use surrounding the vegetable field. The contamination of soil elements decreased in the order of Cd > As ≈ Zn > Cu ≈ Pb > Cr ≈ Ni in 2012 and Cd > Zn > As ≈ Cu ≈ Pb > Cr ≈ Ni in 2016, and the vegetable soils were slightly to moderately contaminated by these elements through integrated contamination index. The sites affected by the trace elements did not increase in 2016 than in 2012, whereas the sites with relatively high contamination increased markedly. The non-carcinogenic risk of trace elements was generally acceptable, and children showed higher health risk than adults. The As carcinogenic risk for children varied between 5.48 × 10−5 and 1.59 × 10−4 in 2012 and between 4.40 × 10−5 and 1.82 × 10−4 in 2016, and the sites above acceptable levels (> 10−4) reached 60.6% and 48.5% in 2012 and 2016, respectively. The health risk of As in the vegetable soils should be paid more attention due to its high toxicity.
... Crops grown through urban horticulture are, on the other side, especially exposed to pollution through air, soil or water, e.g. from historic contamination, current industrial activities and traffic. Clarke et al. (2015) confirmed the accumulation of trace elements in soils near roads. Accordingly, contaminants that accumulated in sinks can be taken up by plants and subsequently enter the food chain (Diamond andHodge 2007, Markert et al. 2011). ...
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Urban horticulture is gaining more and more attention in the context of sustainable food supply. Yet, cities are exposed to (former) industrial activities and traffic, responsible for emission of contaminants. Trace elements were monitored in soils located in the urban environment of Ghent (Belgium) and 84 samples of Lactuca satica L. lettuce grown on it. The effects of cultivation in soil versus trays, neighbouring traffic and washing of the lettuce before consumption were studied. The 0–30 cm top layer of soils appeared heterogenic in composition and enriched in Co, Cd, Ni and Pb within 10 m from the nearest road. Yet, no similar elevated concentrations could be found in the crops, except for As. Besides uptake from the roots, the presence of trace elements in the plants is also caused by the atmospheric deposition of airborne particulate matter on the leaf surface. Correlation analysis and principal component analysis (PCA) revealed that this latter transport pathway might particularly be the case for Pt, Pd and Rh. Concentrations of Cd did not exceed the 0.2 mg/kg (fresh weight) threshold for Cd in leafy vegetables set by the European Commission. Measurements to reduce the health risks include the washing of lettuce, which effectively reduced the number of samples trespassing the maximum Pb level of 0.3 mg/kg (fresh weight). Also, cultivation in trays resulted in a lower As content in the plants. Taking into account a vigilance on crop selection, cultivation substrate and proper washing before consumption are considered essential steps for safe domestic horticulture in urban environments.
... Human exposure to soil borne HMs can be limited by using soil conditioners that reduce HM bioavailability (Al Mamun et al., 2016;Clarke et al., 2015;Mitchell et al., 2014) or by selecting plants where the edible portions are unlikely to contain significant concentrations of HMs. Tree borne fruits are unlikely to have significant amounts of attached soil, as are fruits or vegetables that are peeled or contained within a capsule or pod. ...
Article
Numerous studies have shown that urban soils can contain elevated concentrations of heavy metals (HMs). Christchurch, New Zealand, is a relatively young city (150 years old) with a population of 390,000. Most soils in Christchurch are sub-urban, with food production in residential gardens a popular activity. Earthquakes in 2010 and 2011 have resulted in the re-zoning of 630 ha of Christchurch, with suggestions that some of this land could be used for community gardens. We aimed to determine the HM concentrations in a selection of suburban gardens in Christchurch as well as in soils identified as being at risk of HM contamination due to hazardous former land uses or nearby activities. Heavy metal concentrations in suburban Christchurch garden soils were higher than normal background soil concentrations. Some 46% of the urban garden samples had Pb concentrations higher than the residential land use national standard of 210 mg kg⁻¹, with the most contaminated soil containing 2615 mg kg⁻¹ Pb. Concentrations of As and Zn exceeded the residential land use national standards (20 mg kg⁻¹ As and 400 mg kg⁻¹ Zn) in 20% of the soils. Older neighbourhoods had significantly higher soil HM concentrations than younger neighbourhoods. Neighbourhoods developed pre-1950s had a mean Pb concentration of 282 mg kg⁻¹ in their garden soils. Soil HM concentrations should be key criteria when determining the future land use of former residential areas that have been demolished because of the earthquakes in 2010 and 2011. Redeveloping these areas as parklands or forests would result in less human HM exposure than agriculture or community gardens where food is produced and bare soil is exposed.
... In this study, as mentioned above, it was statistically confirmed that only Pb and Zn significantly differed in the analyzed areas, and also Pb concentration was significantly correlated with Zn which indicated a common source (r ¼ 0.775; p < 0.05). Until the late 1980s, the main source of Pb emission was antiknock additives in gasoline (Kabata-Pendias, 2011), and concentration in soils was correlated with distance from roads and traffic density (Clarke et al., 2015;Schwarz et al., 2012). This supports atmospheric deposition as the main source of pollutants in this study. ...
Among the threats to air, soil, and water posed by urbanization, heavy metals appear particularly hazardous. Playgrounds and sport facilities are unique urban places, widely used by children and youth. The aim of this research was to evaluate heavy metal pollution in urban soils, identify relationships among topsoil metal distributions, and assess related health risks in two Polish cities – Warsaw and Bydgoszcz. According to the Regulation of the Polish Minister of the Environment guidelines for total content of Pb, Cu, Zn, Ni, Cd and Co our study sites were classified as uncontaminated. Applied Geoaccumulation Index (Igeo; Müller, 1969) largely confirmed this classification, with only two of the investigated Warsaw areas “moderately polluted” with Pb. Generally, only Pb and Zn concentrations exceeded reference background levels for Polish soils. The highest concentrations of Pb and Zn were found in the city centers, the oldest areas where pollution risk is potentially the highest. Metal mobility and solubility were mainly correlated with total content, indicating potential risk from lead and zinc. At some sites in Warsaw, where mean Pb concentration was 87.25 mg kg-1 and Zn 207.25 mg kg-1, health risks from ingestion and inhalation seemed significant, particularly for children. In Bydgoszcz use of the studied playgrounds and sport facility areas did not pose a risk to human health. Finally, the study (especially in Warsaw) indicates the need for continued monitoring and suggests lowering permissible limits of these metals in soils, especially in recreational areas, may decrease childrens’ exposure risk to these pollutants.
... Lead-based paint is a possible lead soil source, especially for urban soils (Nezat et al., 2017). Lead may be actively added to soils through degradation of leaded paint on nearby painted surfaces (Clarke et al., 2015). Therefore, lead levels in soil may be related to the locality of painted buildings and their age, as older buildings are more likely to be coated with lead-based paint. ...
Article
Human exposure to lead (Pb) is a growing global public health concern. Elevated blood lead is thought to cause the mental retardation of >0.6 million children globally each year, and has recently been attributed to ~18% of all-cause mortality in the US. Due to the severe health risk, the international community, led by the United Nations Environment Programme (UNEP) and the World Health Organization (WHO), is actively supporting the global phase-out of lead-based paint by 2020. However, there are many significant hurdles on the way to achieving this goal. In light of the importance of the lead-based paint issue, and the urgency of achieving the 2020 phase-out goal, this review provides critical insights from the existing scientific literature on lead-based paint, and offers a comprehensive perspective on the overall issue. The global production and international trade of lead-based paints across Asia, Africa, Latin America, and Europe are critically discussed - revealing that lead-based paints are still widely used in many low and middle-income developing countries, and that the production and trade of lead-based paint is still wide-spread globally. In India, as well as many south-east Asian, African, Latin American and European countries, lead concentrations in paints often exceed 10,000 mg/kg. This will certainly pose a serious global threat to public health from surfaces painted with these products for many decades to come. The sources and pathways of exposure are further described to shed light on the associated health risk and socioeconomic costs. Finally, the review offers an overview of the potential intervention and abatement strategies for lead-based paints. In particular, it was found that there is a general lack of consensus on the definition of lead based paint; and, strengthening regulatory oversight, public awareness, and industry acceptance are vital in combating the global issue of lead based paint.
... This is a result of industrial and traffic emissions and other activities including moving construction materials, construction, manufacturing, fossil fuel combustion, and incinerator emissions (Alloway 2004;Biasioli et al. 2007;Bradley et al. 1994;Norm et al. 2001;Peltola and Aström 2003). Recently, much more research attention has been paid to urban community gardens (e.g., Bretzel et al. 2016;Brown et al. 2016;Clarke et al. 2015;McBride et al. 2014;Mitchell et al. 2014). In domestic gardens, practices and production are little known and totally unregulated, and uncertainty remains as to the exposure of populations to pollutants. ...
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Although growing vegetables in urban gardens has several benefits, some questions in relation with the safety of foods remain when the self-production is carried out on highly contaminated garden soils. To better assess the local population’s exposure to Cd and Pb induced by the past activities of a lead smelter, a participatory program was initiated in 115 private kitchen gardens located in northern France to assist gardeners in understanding their soil environment. The challenge included contributing to the database of urban garden soils with the collection of a large number of samples: 1525 crops grouped into 12 types (leaf, fruiting, root, stem and bulbous vegetables, tubers, cabbages, leguminous plants, celeriac, fresh herbs, fruits, and berries), 708 topsoils, and 52 samples of self-produced compost. The main results were as follows: (i) topsoils were strongly contaminated by Cd and Pb compared to regional reference values; (ii) great variability in physicochemical parameters and metal concentrations in topsoils; (iii) the highest concentrations of Cd and Pb for celeriac and fresh herbs and the lowest for fruits and fruiting vegetables; (iv) a high percentage of vegetables that did not comply with the European foodstuff legislation; and (v) most self-produced compost samples were strongly contaminated. This study aimed to raise awareness and generate functional recommendations to reduce human exposure and to provide useful data that could be considered in other environmental contexts.
... Most work on urban soil health has focused on heavy metals (Clark et al., 2008;Mitchell et al., 2014;Clarke et al., 2015) or organic contaminants (Cachada et al., 2012;Wang et al., 2013). In contrast, the results presented here show a broader view of both soil contaminant safety and soil nutrient and physical characteristics that are important to crop production. ...
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Urban agriculture is growing rapidly in the United States and can combat food deserts and insecurity in metropolitan areas. However, urban farm soils are challenged by legacies of contamination and degradation. Heavy metal contaminated soil, lack of nutrients, and poor soil physical characteristics have led urban farmers in Indianapolis to a novel strategy of layering wood chips on top of background soil to create a barrier between contaminated or low quality soil and healthy growing media. We examined the small group of farms that have begun using this strategy to test if these barriers were effective at preventing soil contamination and improving soil health. We sampled farm soils using either barrier strategies with new imported soil or farming in native soil. Growing bed and background soils were analyzed for heavy metals, soil nutrients, and soil physical characteristics. Though the novelty of the method limited sample size, barrier strategies appeared to be effective at separating contaminated background soils from growing beds. Farming with either barriers or in non-contaminated native urban soils increased soil nutrients and improved soil physical characteristics that support plant growth. In many growing beds, soil phosphorus was very high and posed a potential danger to local waterways. Though the number of sites is limited, these results indicate that barrier strategies are a potentially viable strategy to protect plants, farmers, and consumers from soil contaminants and that this barrier method should be examined in more depth for potential broader application in cities with legacies of soil contamination.
... Pb-based paint: Pb-based paint is a possible Pb soil source, especially for urban soils (Nezat, Hatch, & Uecker, 2017;Jacobs et al., 2002). Pb may migrate into soils through degradation of leaded paint on nearby surfaces (Clarke, Jenerette, & Bain, 2015). Therefore, Pb levels in soils can be related to the proximity to a painted building and the building's age due to the fact that paints used for older buildings are more likely to contain higher Pb contents (Han, Gao, Wei, Xu, & Gao, 2016) and higher reducible Pb fractions (Jiang, Xu, Jiang, & Li, 2012). ...
Article
Soil lead (Pb) pollution is wide spread in China. The Chinese government is taking ambitious actions to tackle the soil pollution issue, with the latest soil quality standards and the Soil Pollution Prevention and Remediation Law enacted in 2018. This study assesses the spatio-temporal distribution, pollution levels, major sources and health risks of Pb in surface soils in China in the past three decades (1990–2017). Traffic emissions (mainly leaded gasoline), mining, smelting, and e-waste recycling were main contributors to soil Pb pollution and pose a risk to food security and human health. The weighted arithmetic mean of Pb concentrations was 35.9 ± 0.21 mg/kg. Southern China suffered from severer soil Pb pollution with hotspots of the Pearl River Delta, Yangtze River Delta, Shaanxi and Hunan. The average soil Pb concentration increased marginally during 1990–2001 due to increased industrial and transportation activities; afterwards, it decreased by ∼30% during 2001–2013, reflecting the effectiveness of the ban on leaded gasoline in 2000. However, there was a slight increase in recent years. Therefore, it is critical to establish a comprehensive evaluation and monitoring system, strengthen pollution source control, properly manage the environmental and health risks at severely contaminated sites, and conduct green and sustainable remediation.
... Mark Laidlaw thanks RMIT University for providing his funding through the Vice Chancellors Table 4 Summary of global studies on residential soil Pb concentrations in urban community and residential gardens. Region # Sites Mean (mg/kg) Median (mg/kg) Range (mg/kg) Notes Reference North America USA e Baltimore, Maryland 422 354 100 1-10,900 residential gardens ( Chaney et al., 1984) USA e Chicago, Illinois 10 14335e449 community gardens ( Witzling et al., 2011) USA eDetroit, Michigan 1 15117e882 community garden ( Bugdalski et al., 2013) USA e Los Angeles, California 12 e18e1720 community gardens ( Clarke et al., 2015) USA e Boston, Massachusetts 141 950 800 80e3680 residential gardens ( Clark et al., 2008) USA-Washington, DC 13 129 e 16e869 community gardens ( Long, 2012) USA e New York City 904 600 355 3e8912 community and residential gardens ( Cheng et al., 2015) USA e New York City 508 (bed soil) 163 (bed soil) 173 (bed soil) 1531 (bed max) community gardens ( Spliethoff et al., 2016) 54 (non-bed soil) 334 (non-bed soil) 375 (non-bed soil) 2455 (non-bed max) Canada e Vancouver, British Columbia 1 219 e 110e234 community gardens ( Oka et al., 2014) Europe France-Nantes 1 313 107 28e5875 community gardens (Jean Soro et al., 2015) France-Nantes 29 61 e 19e229 community gardens ( Bechet et al., 2016) Lisbon, Portugal 18 66 e 23e245 community gardens ( Bechet et al., 2016) Spain-Madrid 6 99 e 15e598 community gardens ( Izquierdo et al., 2015) Australia Sydney, NSW 141 301 135 14e3080 residential gardens ( Rouillon et al., 2017a) Melbourne, VIC 13 102 38 17e578 community gardens This study (2018) Melbourne, VIC 136 204 104 <4-3341 residential gardens This study (2018) Postdoctoral Fellowship Scheme. ...
Article
Gardening and urban food production is an increasingly popular activity, which can improve physical and mental health and provide low cost nutritious food. However, the legacy of contamination from industrial and diffuse sources may have rendered surface soils in some urban gardens to have metals value in excess of recommended guidelines for agricultural production. The objective of this study was to establish the presence and spatial extent of soil metal contamination in Melbourne’s residential and inner city community gardens. A secondary objective was to assess whether soil lead (Pb) concentrations in residential vegetable gardens were associated with the age of the home or the presence or absence of paint. The results indicate that most samples in residential and community gardens were generally below the Australian residential guidelines for all tested metals except Pb. Mean soil Pb concentrations exceeded the Australian HIL-A residential guideline of 300 mg/kg in 8% of 13 community garden beds and 21% of the 136 residential vegetable gardens assessed. Mean and median soil Pb concentrations for residential vegetable gardens was 204 mg/kg and 104 mg/kg (range <5 to 3341 mg/kg), respectively. Mean and median soil Pb concentration for community vegetable garden beds was 102 mg/kg and 38 mg/kg (range = 17 to 578 mg/kg), respectively. Soil Pb concentrations were higher in homes with painted exteriors (p=0.004); generally increased with age of the home (p=0.000); and were higher beneath the household dripline than in vegetable garden beds (p=0.04). In certain circumstances, the data indicates that elevated soil Pb concentrations could present a potential health hazard in a portion of inner-city residential vegetable gardens in Melbourne.
... Clarke et al., 2015; 71 Mitchell et al., 2014;, and need monitoring(Meharg, 2016). Based on current trends, a similar outcome is 72 expected with TCEs in the future. ...
... Soils are the major sink for expended nutrients and heavy metals from both hydrological and atmospheric sources (Candeias et al., 2014;Aiman et al., 2016). Several studies have investigated the problem of persistent heavy metal contamination, including Cd in soil environment Clarke et al., 2015). In China alone, about 10 million ha of agricultural land has been contaminated by Cd toxicity, and *12 Mt of grains are polluted per year . ...
... In city agglomerations -even if there is no specific history of contamination (from chemical industry, smelters, disposal of municipal waste etc.) -significant pollution levels can be expected from increased fossil fuel combustion in heat and power plants, transportation trafficrelated activities, and fossil fuel consumption in households for cooking, water heating, and home heating. In this context, nonbiodegradable, environmentally accumulative metal(loid)s become a most critical human health risks (Clarke et al., 2015;Craul, 1999;Kabata-Pendias, 2011;Ottesen et al., 2008;Schwarz et al., 2012;Wong et al., 2006). Most of European, North American and Chinese urban soils are characterized by medium to high levels of metals, like Pb, Cd, Cu and Zn, which is the effect of the types of industrialization and urbanization history (Li et al., 2001;Luo et al., 2012b). ...
Article
In city agglomerations significant pollution results from fossil fuel combustion from heat and power plants, transportation, and boilers in households. In this context, pollution from recalcitrant, environmentally accumulative metal(loid)s can be a critical human health risk. In day-care centers, playgrounds, kindergartens, schools, and sport facility areas children may ingest significant quantities of potentially polluted soil and dust, increasing incidence of health disorders or diseases. The objective of this study was to assess the oral bioaccessibility and human health risk of As, Cd, Pb, Cr, Ni, Cu, and Zn from potentially polluted urban topsoils by applying gastrointestinal Unified Bioaccessibility Method (UBM) protocol. Total content of studied elements was relatively low and none of studied elements exceeded Polish legal limits for urban soils. According to the Enrichment Factor (EF), studied sites were characterized from minimal to significant degrees of soil pollution by analyzed metal(loid)s in the order: Pb > Zn > Cu > Cd > As > Ni > Cr. Concentrations of the metal(loid)s in bioaccessible phases were varied, and higher for gastric than gastrointestinal bioaccessibility. Metal(loid) bioaccessibility in soils of Bydgoszcz was highly correlated with total concentration. Almost no correlation was found between concentration of these phases and parameters like soil pH, texture, CaCO3, TOC, or CEC. A relationship did exist with landform where the lower positions had greater concentrations. These locations are those with the highest traffic density and operation of old coal heating systems leading to the highest deposition of airborne contaminants. Higher landscape positions are favored for new facilities in newer residential districts. Exposure and health risk from soil ingestion given normal ingestion scenario at any site investigated was very low. Non-carcinogenic and carcinogenic risk was identified only for soil pica behavior. Soil pica ingestion scenario might be considered for children with lapses of adult.
... The heavy metals entering the soil form different forms of heavy metals through the reactions of dissolution, adsorption, complexation, precipitation and coagulation [1~3] . The activities [4] , migration characteristics [5] , biotoxicity [6] and environmental effects [7] of these heavy metals are different. Schramel et al. [8] find that the residual copper content in unpolluted soil is 65%~85% and organic copper is 30%. ...
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The contents of As, Cr, Cu, Zn and Pb in soils of the central urban area of Nanjing Jiangbei New area are analyzed by interpolation analysis. The effects of pH value, soil texture and heavy metal species on the contents of heavy metals are studied. The results show that the contents of heavy metals in the study area are more than 1.5 to 6.3 times of the soil background value in Jiangsu Province. The content of heavy metal Cr is 31.92∼95.38 mg/kg, and some areas have already exceeded the control value of the second type of construction land in China, 78 mg/kg. The pH value is inversely proportional to the total heavy metal content, which indicates that it is more difficult to enrich heavy metal ions in alkaline environment. The soil texture in this area is dominated by sand grains, and the spatial distribution of sand grain content decreases from southwest to northeast. The clay content is positively correlated with the heavy metal content except Zn. The main forms of the five kinds of heavy metals in soil are residues, reaching 73.86%∼88.15%, and with the increase of heavy metals content in soil, the proportion of residual decreases.
... Clarke et al. (2015); Jean-Soro et al.(2015);Schwarz et al. (2012) Substrates of organic originPeatsResult from anaerobic decomposition of peat mosses under waterlogged conditions. Depending on conditions under which they were generated, peats possess superb physical, chemical and biological properties suitable for plant growth. ...
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Research and practice during the last 20 years has shown that urban agriculture can contribute to minimising the effects of climate change by, at the same time, improving the life quality in urban areas. In order to do so most effectively, land use and spatial planning are crucial so as to obtain and maintain a supportive green infrastructure and to secure citizens' healthy living conditions. As people today trend more towards living in green and sustainable city centres that can offer fresh and locally produced food, cities become again places for growing food. The scope of urban agriculture thereby is to establish food production sites within the city's sphere; f.e. through building-integrated agriculture including concepts such as aquaponics, indoor agriculture, vertical farming, rooftop production, edible walls, as well as through urban farms, edible landscapes, school gardens and community gardens. Embedded in changing urban food systems, the contribution of urban agriculture to creating sustainable and climate-friendly cities is pivotal as it has the capacity to integrate other resource streams such as water, waste and energy. This article describes some of the current aspects of the circular city debate where urban agriculture is pushing forward the development of material and resource cycling in cities.
... Evidence for increases in the concentration of potential toxic elements (e.g., Cd, Cr, Cu, Ni, Pb, Zn) in roadside soils has been reported for Australia [37], Russia [10], China [38], the USA [39], and many European countries [40]. The burning of fossil fuels, consumption of car tires, brake wear, and engine oil are the primary sources of these elements [41]. ...
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The phylloplane is an integrated part of green infrastructure which interacts with plant health. Taxonomic characterization of the phylloplane with the aim to link it to ecosystem functioning under anthropogenic pressure is not sufficient because only active microorganisms drive biochemical processes. Activity of the phylloplane remains largely overlooked. We aimed to study the interactions among the biological characteristics of the phylloplane: taxonomic diversity, functional diversity and activity, and the pollution grade. Leaves of Betula pendula were sampled in Moscow at increasing distances from the road. For determination of phylloplane activity and functional diversity, a MicroResp tool was utilized. Taxonomic diversity of the phylloplane was assessed with a combination of microorganism cultivation and molecular techniques. Increase of anthropogenic load resulted in higher microbial respiration and lower DNA amount, which could be viewed as relative inefficiency of phylloplane functioning in comparison to less contaminated areas. Taxonomic diversity declined with road vicinity, similar to the functional diversity pattern. The content of Zn in leaf dust better explained the variation in phylloplane activity and the amount of DNA. Functional diversity was linked to variation in nutrient content. The fraction of pathogenic fungi of the phylloplane was not correlated with any of the studied elements, while it was significantly high at the roadsides. The bacterial classes Gammaproteobacteria and Cytophagia, as well as the Dothideomycetes class of fungi, are exposed to the maximal effect of distance from the highway. This study demonstrated the sensitivity of the phylloplane to road vicinity, which combines the effects of contaminants (mainly Zn according to this study) and potential stressful air microclimatic conditions (e.g., low relative air humidity, high temperature, and UV level). Microbial activity and taxonomic diversity of the phylloplane could be considered as an additional tool for bioindication.
... Agricultural land often has increased levels of arsenic, lead, and cadmium due to application of fertilizers and now outlawed pesticides. In urban areas, major sources of lead contamination include lead-based paints, automotive emissions, and local industries such as smelters and manufacturing (Clarke, Jenerette, & Bain, 2015;Thornton, 2009). In addition, soil contamination can be increased due to contaminated water running through urban areas from other regions. ...
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Urban community gardens have increased in prevalence as a means to generate fresh fruits and vegetables, including in areas lacking access to healthy food options. However, urban soils may have high levels of toxic heavy metals, including lead and cadmium and the metalloid arsenic, which can lead to severe health risks. In this study, fruit and vegetable samples grown at an urban community garden in southeastern San Diego, the Ocean View Growing Grounds, were sampled repeatedly over a four‐year time period in order to measure potential contamination of toxic heavy metals and metalloids and to develop solutions for this problem. Metal nutrient, heavy metal, and metalloid concentrations were monitored in the leaf and fruit tissues of fruit trees over the sampling period. Several of the fruit trees showed uptake of lead in the leaf samples, with Black Mission fig measuring 0.843–1.531 mg/kg dry weight and Mexican Lime measuring 1.103–1.522 mg/kg dry weight over the sampling period. Vegetables that were grown directly in the ground at this community garden and surrounding areas showed arsenic, 0.80 + 0.073 mg/kg dry weight for Swiss chard, and lead, 0.84 ± 0.404 mg/kg dry weight for strawberries, in their edible tissues. The subsequent introduction of raised beds with uncontaminated soil is described, which eliminated any detectable heavy metal or metalloid contamination in these crops during the monitoring period. Recommendations for facilitating the monitoring of edible tissues and for reducing risk are discussed, including introduction of raised beds and collaborations with local universities and research groups.
... However, heavy metal concentrations accumulate rapidly in suburban soils because of long-term cultivation and rapid urbanization and industrialization (Ahmad et al., 2019;Hu et al., 2018;Li et al., 2017;Wu et al., 2018). Heavy metal pollution has been reported in the suburban soil of several cities worldwide, such as Los Angeles (Clarke et al., 2015), Cleveland, and Columbus in the United States (Sharma et al., 2015); Sheffield in England (Weber et al., 2019); Trieste in Italy (Giglio et al., 2017); Tokyo in Japan (Hossain et al., 2009); and Beijing and Shanghai (Bi et al., 2018) in China. These reports suggest that the concentration of heavy metals in suburban areas exceeds local natural background values and thus poses immense health risks to residents. ...
... Federal legislation banned lead in residential paint and in the pipes and solder used for drinking water in 1978 and 1986 respectively, (Levin et al., 2008;O'Connor et al., 2018) though older houses may pose a risk if mitigation efforts have not been performed. Lead in soil arises from pulverized paint as well as deposition of lead compounds from industrial facilities and exhaust from combustion of leaded gasoline (Clarke, Jenerette, & Bain, 2015;Mielke & Reagan, 1998;O'Connor et al., 2018). ...
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Introduction COVID-19 has disrupted outpatient pediatrics, postponing well child care to address immediate patient-safety concerns. Screening for lead toxicity is a critical component of this care. Furthermore, children may be at increased risk for lead exposure at home due to social restrictions. We present data on how COVID-19 restrictions have impacted lead screening in a primary care practice. Method Lead testing data on 658 children in an outpatient primary care practice in Connecticut were analyzed to determine the effect of COVID-19 restrictions on lead screening rates, levels, and deficiencies. Results Lead screening significantly decreased during peak restrictions, leading to increased screening deficiencies. Despite this decreased volume, screening lead levels increased during peak restrictions. Discussion These data show how COVID-19 restrictions have disrupted routine care and highlight the importance of continued lead screening in at-risk populations. The EMR can be leveraged to identify deficiencies to be targeted by Quality Improvement initiatives.
... The highest percentages that exist in Damietta and Kafr Saad districts may be attributed to the relatively high organic matter contents and the low soil pH.There is no correlation between DTPA-extractable Pb and clay content of the soils. On the other hand, a positive significant correlation was found between the available Pb and both of the organic matter content (r 2 = 0.82) and negative correlation with soil pH (r 2 = -0.76).Our results agree with [51,52], they reported that the levels of DTPA extractable metals related to the total content and other soil properties such as soil pH and organic matter content. ...
... From this point of view, they seemed to exert more indirect influences. Cu, Pb, and Zn have often been traffic-related in urban environments in previous studies [51][52][53]. However, with a slight difference, we found that industrial emissions determined the soil pollution with Cu while it was the soil properties for Pb. ...
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Natural and anthropogenic activities affect soil heavy metal pollution at different spatial scales. Quantifying the spatial variability of soil pollution and its driving forces at different scales is essential for pollution mitigation opportunities. This study applied a multivariate factorial kriging technique to investigate the spatial variability of soil heavy metal pollution and its relationship with environmental factors at multiple scales in a highly urbanized area of Guangzhou, South China. We collected 318 topsoil samples and used five types of environmental factors for the attribution analysis. By factorial kriging, we decomposed the total variance of soil pollution into a nugget effect, a short-range (3 km) variance and a long-range (12 km) variance. The distribution of patches with a high soil pollution level was scattered in the eastern and northwestern parts of the study domain at a short-range scale, while they were more clustered at a long-range scale. The correlations between the soil pollution and environmental factors were either enhanced or counteracted across the three distinct scales. The predictors of soil heavy metal pollution changed from the soil physiochemical properties to anthropogenic dominated factors with the studied scale increase. Our study results suggest that the soil physiochemical properties were a good proxy to soil pollution across the scales. Improving the soil physiochemical properties such as increasing the soil organic matter is essentially effective across scales while restoring vegetation around pollutant sources as a nature-based solution at a large scale would be beneficial for alleviating local soil pollution
... The highest percentages that exist in Damietta and Kafr Saad districts may be attributed to the relatively high organic matter contents and the low soil pH.There is no correlation between DTPA-extractable Pb and clay content of the soils. On the other hand, a positive significant correlation was found between the available Pb and both of the organic matter content (r 2 = 0.82) and negative correlation with soil pH (r 2 = -0.76).Our results agree with [51,52], they reported that the levels of DTPA extractable metals related to the total content and other soil properties such as soil pH and organic matter content. ...
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Grains of rice and wheat are important food as a cereal crop in Egypt as in the world. Recently, the lead (Pb) content of soils and plants increased as a result of different pollutant sources causing negative environmental impacts. Therefore, this study aimed to estimate the level of Pb in the soils, rice and wheat plants of Damietta governorate cultivated area and evaluate its impact on human health. Results shows that soil total Pb in the surface layer (26.7 ± 11.1 mg kg-1) are higher than the subsurface layers (1.27 ± 0.13-fold) due to its low mobility with soil depth. The DTPA extractable Pb in the surface layers (0.69 ± 0.50 mg kg-1) are also higher than subsurface (1.35 ± 0.42-fold) and represents a small fraction from total (2.39 ± 1.1%). Moreover, DTPA extractable Pb shows a significant positive correlation with total soils Pb (r2 = 0.73) and organic matter content (r2 = 0.82), on the other hand, a negative correlation with the soil pH (r2 = - 0.76). Rice grain Pb concentrations (0.09 ± 0.02 mg kg-1) is lower than straw (0.72 ± 0.12 mg kg-1), which represents 12.6% ± 1.70-fold. A significant correlation is found between rice grains and straw Pb content (r2 = 0.95) that also increasing soil DTPA extractable Pb rice straw (r2 = 0.91) and grains (r2 = 0.93). On the other hand, wheat grain Pb concentrations (0.08 ± 0.024 mg kg-1) is lower than straw (0.63 ± 0.19 mg kg-1), which represents 11.9% ± 1.74-fold. However, a significant correlation is found between wheat grain and straw Pb concentrations (r2 = 0.92) that also by increasing soil DTPA extractable Pb wheat straw (r2 = 0.82) and grains (r2 = 0.75). Rice and wheat grains Pb concentrations are lower than the permissible limits according to WHO/FAO and EU (0.20 mg kg-1) and no potential human health risk is concluded yet. Key words: Lead; rice (Oryza sativa L.); wheat (Triticum aestivum L.); grains; Egypt
... Data were collected in fluorescence mode using a Si (111) monochromator and a 4-element vortex silicon-drift detector with metal filters to reduce the impact of elastic scattering. Multiple scans (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) were recorded per sample to improve the signal-to-noise ratio. The IFEFFIT software package was used to perform data reduction, analysis and fitting [49]. ...
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Farmed urban soils often bear legacies of historic contamination from anthropogenic and industrial sources. Soils from seven community farms in Newark, New Jersey (NJ), USA, were analyzed to determine the concentration and speciation of lead (Pb) depending on garden location and cultivation status. Samples were evaluated using single-step 1 M nitric acid (HNO3) and Tessier sequential extractions in combination with X-ray absorption fine structure spectroscopy (XAFS) analysis. Single-step extractable Pb concentration ranged from 22 to 830 mg kg−1, with 21% of samples reporting concentrations of Pb > 400 mg kg−1, which is the NJ Department of Environmental Protection (NJDEP) limit for residential soils. Sequential extractions indicated lowest Pb concentrations in the exchangeable fraction (0–211 mg kg−1), with highest concentrations (0–3002 mg kg−1) in the oxidizable and reducible fractions. For samples with Pb > 400 mg kg−1, Pb distribution was mostly uniform in particle size fractions of <0.125–1 mm, with slightly higher Pb concentrations in the <0.125 mm fraction. XAFS analysis confirmed that Pb was predominantly associated with pyromorphite, iron–manganese oxides and organic matter. Overall results showed that lowest concentrations of Pb are detected in raised beds, whereas uncultivated native soil and parking lot samples had highest values of Pb. As most of the Pb is associated with reducible and oxidizable soil fractions, there is a lower risk of mobility and bioavailability. However, Pb exposure through ingestion and inhalation pathways is still of concern when directly handling the soil. With increasing interest in urban farming in cities across the USA, this study highlights the need for awareness of soil contaminants and the utility of coupled macroscopic and molecular-scale geochemical techniques to understand the distribution and speciation of soil Pb.
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Urban horticulture (UH) has been proposed as a solution to increase urban sustainability, but the potential risks to human health due to potentially elevated soil heavy metals and metalloids (HM) concentrations represent a major constraint for UH expansion. Here we provide the first UK-wide assessment of soil HM concentrations (total and bioavailable) in UH soils and the factors influencing their bioavailability to crops. Soils from 200 allotments across ten cities in the UK were collected and analysed for HM concentrations, black carbon (BC) and organic carbon (OC) concentrations, pH and texture. We found that although HM are widespread across UK UH soils, most concentrations fell below the respective UK soil screening values (C4SLs): 99 % Cr; 98 % As, Cd, Ni; 95 % Cu; 52 % Zn. However, 83 % of Pb concentrations exceeded C4SL, but only 3.5 % were above Pb national background concentration of 820 mg kg⁻¹. The bioavailable HM concentrations represent a small fraction (0.01–1.8 %) of the total concentrations even for those soils that exceeded C4SLs. There was a significant positive relationship between both total and bioavailable HM and soil BC and OC concentrations. This suggest that while contributing to the accumulation of HM concentrations in UH soils, BC and OC may also provide a biding surface for the bioavailable HM concentrations contributing to their immobilisation. These findings have implications for both management of the risk to human health associated with UH growing in urban soils and with management of UH soil. There is a clear need to understand the mechanisms driving soil-to-crop HM transfer in UH to improve potentially restrictive C4SL (e.g. Pb) especially as public demand for UH land is growing. In addition, the UH community would benefit from education programs promoting soil management practices that reduce the risk of HM exposure - particularly in those plots where C4SLs were exceeded.
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The investigation of the chemical composition, antioxidant and cytotoxic activities of the essential oil of Pulicaria vulgaris wild growing in Akmola region, Kazakhstan was the aim of the study. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC/MS). A total of 49 compounds were identified representing 86.4 % and the major components were patchoulane (37.4), buddledin C (13.9%), T-cadinol (4.7%), trans-sesquisabinene hydrate (4.1%), dyhydro--agarofuran (2.7%), (Z)-α-atlantone (1.8%) and corymbolone (1.2%). Six components were identified as unknown (2.6%). The antioxidant activity was evaluated by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and the essential oil demonstrated an average scavenging effect at 0.75 and 1 mg ml-1 concentrations compared with butylhydroxyanisole (BHA). The antiradical activity results of the P. vulgaris essential oil is published for the first time. Cytotoxic activity assay was studied against Artemia salina larvae and it can be concluded that the essential oil has a good lethal toxicity in all tested concentrations (10-1 mg ml-1). The authors attribute this result to the presence of the patchoulane as a major component, which is known for its activity against ovarian cancer cells.
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Urban agriculture has its history tied to the development of civilizations. Aiming to identify the benefits generated by the practice and its motivations, a literature review and later analysis of articles describing current experiences, management characteristics and organization aspects was carried out. In countries with a very high HDI, community gardens and the well-being of the population are prominent themes. Countries with high HDI focus on soil contamination and mitigation of pollution impacts, as countries with an average HDI has as main theme the sustainability of the practice. Finally, low HDI countries discuss their importance for food security. Regardless of the objectives that motivate urban agriculture and research in the area, is evidenced its contribution to the environmental, social and economic quality of cities.
Thesis
Urban agriculture (UA) is defined as the production of food crops or livestock within urban areas. Despite its popularity in the United States, research into UA systems suffers from a general underrepresentation of commercial urban systems. As a result, urban growers often have unique technological needs that are unmet by research and extension. I worked with a particularly ubiquitous group of urban growers, home gardeners, to better understand the current status of urban agricultural soils. Specifically, this study had three parts. First, I documented the current extent of research and knowledge related to urban agricultural soils in the United States (Chapter 1). Second, I noted the characteristics of residential-scale vegetable gardens in Corvallis and Portland, Oregon, to better understand current growing conditions and needs (Chapter 2). Third, I characterized the biological, physical, and chemical characteristics of these same gardens (Chapter 3). Finally, I conclude with potential directions for further research (Chapter 4). In Chapter 1, I reviewed the academic literature on urban soils and found research which directly analyzed urban agricultural soil to be lacking. Only 17 studies directly addressed the characteristics of urban agricultural soils in the United States. Heavy metals were the subject of the vast majority of these articles, with about half thestudies investigating chemical fertility parameters, and even fewer examining biological and physical qualities of agriculturally productive urban soils. Nearly all studies were conducted in residential sites, which potentially limits data-driven urban agricultural policies focused on commercial urban agriculture as a means to supplement locally grown foods. In order to better inform management recommendations, I recorded garden characteristics of trained urban food growers. In Chapter 2, I report on a survey of surveyed 27 residential food gardens (including two demonstration gardens) in two Pacific Northwest cities. All site managers were trained Oregon State University Extension Master Gardeners. I found 132 unique crops were tended across all gardens, and a variety of management approaches were used. The most noteworthy concern I noted from the site managers was a desire to reconcile the mechanics of crop rotation within a small production footprint. In Chapter 3, I examined the composition of urban garden soils from those same 27 sites in Corvallis and Portland, Oregon. In addition to recording the physical, biological, chemical fertility, and heavy metal parameters of urban garden soils, I tested for differences between garden sites based upon bed-type (e.g. raised beds versus in- ground beds). Raised beds were significantly different than in-ground beds for nearly one-third of the soil parameters recorded. Further, the mean soil fertility values across all sites were 2-8x above the recommended range for one-third of the parameters examined. I believe excessive applications of organic matter to be the source of this nutrient excess. Excessive organic matter, annually added to small garden spaces, likely promotes soil nutrient imbalances. However, the message many urban growers are given is that adding organic matter to soils is good. My data suggests that urban growers need more nuanced recommendations which account for the unique constraints of small garden spaces. Further, the recommendation to build raised beds to avoid contamination did not hold in this investigation. The matter seems more complicated, and I suggest greater scrutiny be applied to discover the source of contaminated soils in raised beds.In Chapter 4, I suggest how policy, training, laboratory procedures, and management goals can be adjusted in light of these findings. It seems that the excessive nutrient levels in raised beds is a waste of both economic and environmental resources, with the potential for nutrient leaching as well. I believe that a well-informed site manager can quickly alter the productive capacity of an urban soil. Researchers who wish to contribute to urban agriculture should search for alternative management options which confer the benefits of compost while balancing the varied nutrient content therein. This likely involves using alternative fertilizer sources as well as novel bulking agents which can build but not imbalance a newly productive soil.
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Urban environments are contaminated in many ways with persistent organic and inorganic pollutants as a result of anthropogenic activities, endangering human health and natural resources. The objective of the present study was to evaluate the soil contamination by cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) in 10 vegetable gardens of urban schools located near or on Botucatu sandstone outcrops of Guarani Aquifer in the urban areas of Lages, Santa Catarina, Brazil. In each garden, three soil samples at each position (in the soil immediately outside and the soil in the garden) were collected at a depth of 0-20 cm. The ISO 11466 method was used to extract the metals. Inductively coupled plasma optical emission spectrometry was used to quantify the elements and certified materials to evaluate the quantities (SRM 2709a - San Joaquin Soil - NIST). To evaluate the data, principal component analyses and cluster analyses were performed. The cluster analysis for the evaluated metals showed that the highest contents of elements were reported in three gardens. Values above the prevention value defined by resolution no. 420/2005 of the National Council for the Environment -Conselho Nacional do Meio Ambiente (CONAMA) - were reported for cobalt in one garden and copper in three gardens; thus, these areas were categorized as Class III areas. Principal component analysis explained 74.7% of the data and showed the enrichment of some elements within gardens.
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Concerns about motor vehicle emissions on human health are typically focused on aerial pollution and are regulated via controls on tailpipe emissions. However, vehicles also contribute heavy metal emissions through non-tailpipe pathways (e.g., brake wear, tire particulates). The metal pollutants produced via both tailpipe and non-tailpipe pathways pose threats to both human and ecosystem health long after they have settled from the atmosphere largely via contamination of soils and plants. In this study, we examined the effect of vehicular pollution on soils and plants in five paired sites in Gaviota, CA. In each site, we examined the effect of proximity to road on heavy metal concentrations (cadmium, nickel, lead, and zinc) in four of the most common roadside plant species—Melilotus indicus, Herschfeldia incana, Avena sativa, and Artemisia californica—as well as on soil metal concentrations. Then, to look at potential effects of road proximity and associated metal pollution on plants, we also examined the carbon and nitrogen ratios of all the plant samples. We found strong and significant effects of proximity to road on concentrations of all heavy metals in plants; plants in close proximity to roads had metal concentrations between 8 and 11 times higher than plants farther from roads. Plant C:N ratios also varied strongly among site types and were always higher in close proximity to roads as compared to farther off roads, potentially indicating broader effects of road proximity to plant ecology and leaf quality for consumers in the region.
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Although best management practices have been recommended by government agencies and non-profit organisations to reduce community gardeners’ potential exposure to soil contaminants such as lead, some gardeners do not perform these practices. Understanding gardeners’ beliefs and motivations is critical for effective promotion of safer gardening practices. This study, grounded in the Theory of Planned Behavior (TPB), employed five focus groups to investigate Atlanta community garden leaders’ perspectives concerning three gardening practices: composting, hygiene behaviours, and mulching. These general practices are also considered safe gardening practices in that they can reduce exposure to toxicants in urban gardens. Qualitative analysis identified advantages and disadvantages; supporters and non-supporters; and barriers and facilitators that might influence gardeners’ opinions regarding these behaviours. Gardeners expressed that more funding, volunteers, and training are needed to promote these behaviours. Gardeners noted that mulch and compost provided advantages such as improving soil quality, but a primary barrier was concern about contamination of source materials. Focus group participants did not directly associate composting and mulching with reduction of exposure to soil contaminants. Behavioural challenges related to hygiene included concerns about decreased exposure to salubrious bacteria, inadequate access to potable water, and limited availability of gloves and wipes. These study findings characterise factors that community garden stakeholders should consider when promoting safe gardening practices and interventions.
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The population growth, the expansion of the city and the increase of the automotive park of the canton Cuenca has caused a deterioration in air quality, which puts at risk the agricultural production in the nearby rural areas, the objective of the present study was to determine the concentration of Pb in the foliage of cabbage lettuces in the San Joaquín parish. Twelve lettuces of cabbage were planted in two beds that were located in open-pit and greenhouse conditions with a common substrate soil for the development of the plants, the substrate was characterized, the results showed that the content of lead in the foliage of the Lettuce came mostly from the air. At the time of harvest, foliage samples were sent for the analysis of the Pb content by the atomic absorption method, the lowest value corresponded to the greenhouse crop with an average of 0,066 mg / kg, while the open crop obtained value of 0,087 mg / kg, according to the independent T-test, there is no significant statistical difference, these values of lead concentration are below the limits established by the World Health Organization, which is considered that lettuces they are not contaminated with Pb associated with vehicles and fuels.
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Stand litter of some coniferous and deciduous plantations within the Botanical Garden of Moscow State University is studied. It is established that stand litter of destructive types develops under conditions of deciduous plantations, whereas it is fermentative and humified in coniferous plantations. The total reserves of stand litters range from 500–800 g/m² in deciduous plantations to 1000–5000 g/m² in coniferous plantations. It is shown that small-leaved plantations are characterized by high rates of cycling with a significant decrease in the coniferous ecosystems. It was shown for the first time that the overall decomposition rate of terrestrial litter increases substantially with an increase in the proportion of leaves in the litter, which is confirmed by the theory of “hot points” proposed in the scientific literature.
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Thoroughly updated and now in full color, the 15th edition of this market leading text brings the exciting field of soils to life. Explore this new edition to find: A comprehensive approach to soils with a focus on six major ecological roles of soil including growth of plants, climate change, recycling function, biodiversity, water, and soil properties and behavior. New full-color illustrations and the use of color throughout the text highlights the new and refined figures and illustrations to help make the study of soils more efficient, engaging, and relevant. Updated with the latest advances, concepts, and applications including hundreds of key references. New coverage of cutting edge soil science. Examples include coverage of the pedosphere concept, new insights into humus and soil carbon accumulation, subaqueous soils, soil effects on human health, principles and practice of organic farming, urban and human engineered soils, new understandings of the nitrogen cycle, water-saving irrigation techniques, hydraulic redistribution, soil food-web ecology, disease suppressive soils, soil microbial genomics, soil interactions with global climate change, digital soil maps, and many others Applications boxes and case study vignettes bring important soils topics to life. Examples include “Subaqueous Soils—Underwater Pedogenesis,” “Practical Applications of Unsaturated Water Flow in Contrasting Layers,” “Soil Microbiology in the Molecular Age,” and "Where have All the Humics Gone?” Calculations and practical numerical problems boxes help students explore and understand detailed calculations and practical numerical problems. Examples include “Calculating Lime Needs Based on pH Buffering,” “Leaching Requirement for Saline Soils,” "Toward a Global Soil Information System,” “Calculation of Nitrogen Mineralization,” and “Calculation of Percent Pore Space in Soils.”
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Applications of soil science will become increasingly important in urban ecosystems with anticipated population growth. Our overall objective was to address the issues involved in urban soil research. Specifically, the objectives were (i) to highlight past and current urban soil science research, (ii) to identity the need for special soil amendments and soil blends for urban landscape projects, and (iii) to encourage more soil scientists to address the research needs of rapidly expanding urban landscapes. Much of the early research with urban soils focused on identification and classification of anthropogenic influences. Those activities continue to be important, but there is an opportunity and need for soil scientists to expand their research activities into the area of highly modified and manufactured soils. Soil management in urban settings differs from natural and agricultural settings because the land units are smaller and the availability of soil amendments is much greater, thus the degree of modification is more intense. Organic and inorganic materials are abundantly used in urban landscapes as direct soil amendments or as ingredients in manufactured soils. These amendments can have a significant potential impact on soil and water resources in the urban environment. Soil scientists can make important contributions to urban soil science by developing good urban soil management practices, by evaluating the benefits and risks associated with soil amendments, and by developing soil blends for specialized urban applications such as parks, sports fields, plazas, and green roofs. The progression from a rural to an urban population effectively creates a variety of opportunities for soil scientists to conduct research, extension, and teaching activities with an ever-increasing urban focus.
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Context Urban community gardens are globally prevalent urban agricultural areas and have the potential to fulfill human needs in impoverished neighborhoods, such as food security and access to open space. Despite these benefits, little research has been conducted evaluating environmental and socioeconomic factors influencing community garden plant biodiversity and ecosystem services (ES). Objective Our study investigated the drivers of managed plant richness, abundance, and ES production in community gardens across Los Angeles County, CA from 2010 to 2012 at regional, garden, and plot scales. Methods Fourteen community gardens were visited in the summers of 2010–2012 for comprehensive species surveys across regional, garden, and plot scales. We compared biodiversity to household income, plot size, and gardener ethnicity. Results In total, 707 managed plant species were recorded in summer surveys over a 3-year period. Ornamental plant richness increased with neighborhood income, while edible and medicinal richness increased with size of garden plots. Gardener ethnicity also influenced the composition of managed species, especially edible species. Conclusions We explain these patterns through a hierarchy of needs framework; gardeners preferentially plant species progressively less connected to human need. Ornamental plant increases in high-income regions may be explained by their requirement for financial investment and maintenance time. Cultural and provisioning ES are important for immigrant populations, resulting in ethnically distinct crop assemblages. Finally, distinct species–area relationships imply high demand for food abundance and biodiversity. Our quantitative results indicate that community gardens contribute to a biologically diverse urban ecosystem and provide valued ecosystem services in food insecure regions.
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Lead (Pb) is one of the most common contaminants in urban soils. Gardening in contaminated soils can result in Pb transfer from soil to humans through vegetable consumption and unintentional direct soil ingestion. A field experiment was conducted in 2009 and 2010 in a community urban garden with a soil total Pb concentration of 60 to 300 mg kg-1. The objectives of this study were to evaluate soil–plant transfer of Pb, the effects of incorporation of a leaf compost as a means of reducing Pb concentrations in vegetables and the bioaccessibility of soil Pb, and the effects of vegetable cleaning techniques on the Pb concentrations in the edible portions of vegetables. The amount of compost added was 28 kg m-2. The tested plants were Swiss chard, tomato, sweet potato, and carrots. The vegetable cleaning techniques were kitchen cleaning, laboratory cleaning, and peeling. Compost addition diluted soil total Pb concentration by 29 to 52%. Lead concentrations of the edible portions of vegetables, except carrot, were below the maximum allowable limits of Pb established by the Food and Agriculture Organization and the World Health Organization. Swiss chard and tomatoes subjected to kitchen cleaning had higher Pb concentrations than laboratory-cleaned plants. Cleaning methods did not affect Pb concentrations in carrots. Bioaccessible Pb in the compost-added soils was 20 to 30% less than that of the no-compost soils; compost addition reduced the potential of transferring soil Pb to humans via vegetable consumption and direct soil ingestion. Thorough cleaning of vegetables further reduced the potential of transferring soil Pb to humans
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As urban agriculture grows in popularity, researchers are attempting to quantify its potential contribution to local food systems. We present the results of a vacant land inventory conducted in collaboration with the HOPE Collaborative, a multi-stakeholder, community-based initiative in Oakland, CA, USA. Vacant lots, open space, and underutilized parks with agricultural potential were identified using GIS and aerial imagery. Using visual interpretation, we identified 1201 ac (486.4 ha) of public land and 337 ac (136.4 ha) of private land that could potentially be used for vegetable production. Based on USDA loss-adjusted consumption data, we calculated the potential contribution of these sites to the city's current and recommended vegetable needs. Calculations were based on average yields under three different management practices: conventional at 10 tons/ac (22.4 Mg/ha); low-biointensive at 15 tons/ac (33.6 Mg/ha); and medium-biointensive at 25 tons/ac (56.0 Mg/ha). Four different land use scenarios were considered: (1) all identified sites (<30% slope); (2) optimal land (<30% slope excluding north-facing slopes); (3) a high land use scenario of 500 ac (202.3 ha); and (4) a low land use scenario of 100 ac (40.5 ha). We estimate that the most conservative scenario would contribute between 2.9 and 7.3% of Oakland's current consumption, depending on production methods, or 0.6–1.5% of recommended consumption. While an inventory is an important first step, determining how much vacant land should be committed to urban agriculture will ultimately depend on additional site assessment and negotiation of potentially conflicting stakeholder interests.
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As urban agriculture grows in popularity throughout North America, vacant lots, underutilized parks, and other open spaces are becoming prime targets for food production. In many post-industrial landscapes and in neighborhoods with a high density of old housing stock, the risk of lead (Pb) contamination at such sites is raising concerns. This paper evaluates the extent to which soil Pb contamination may be an obstacle to the expansion of urban agriculture in Oakland, California. Using a combination of soil sampling at 112 sites, GIS, “hot spot” analysis, and reconstructed land use histories, the research reveals that soil Pb concentrations are generally lower than federal screening levels of 400 ppm, but significantly higher in West Oakland, the city's oldest area and home to a predominantly low-income and African American population. Lead levels are significantly lower in the affluent, predominantly white Oakland hills. Spatial analysis at city- and neighborhood-scales reveals clusters of Pb contamination related to land use history. Site-scale analyses at 12 sites reveals a high level of variability (in some cases related to land use history) that must be taken into consideration when planning for urban agriculture.
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This review considers the relationships of Pb exposure from urban soils and dusts and from crops grown in urban gardens, and the potential consequences of the exposure.
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Cadmium is at the end of the 4d-transition series, it is relatively mobile and acutely toxic to almost all forms of life. In this review we present a summary of information describing cadmium's physical and chemical properties, its distribtion in crustal materials, and the processes, both natural and anthropogenic, that contribute to the metal's mobilization in the biosphere. The relatively high volatility of Cd metal, its large ionic radius, and its chemical speciation in aquatic systems makes Cd particularly susceptible to mobilization by anthropogenic and natural processes. The biogeochemical cycle of Cd is observed to be significantly altered by anthropogenic inputs, especially since the beginning of the industrial revolution drove increases in fossil fuel burning and non-ferrous metal extraction. Estimates of the flux of Cd to the atmosphere, its deposition and processing in soils and freshwater systems are presented. Finally, the basin scale distribution of dissolved Cd in the ocean, the ultimate receptacle of Cd, is interpreted in light of the chemical speciation and biogeochemical cycling of Cd in seawater. Paradoxically, Cd behaves as a nutrient in the ocean and its cycling and fate is intimately tied to uptake by photosynthetic microbes, their death, sinking and remineralization in the ocean interior. Proximate controls on the incorporation of Cd into biomass are discussed to explain the regional specificity of the relationship between dissolved Cd and the algal nutrient phosphate (PO[Formula: see text]) in oceanic surface waters and nutriclines. Understanding variability in the Cd/PO[Formula: see text] is of primary interest to paleoceanographers developing a proxy to probe the links between nutrient utilization in oceanic surface waters and atmospheric CO(2) levels. An ongoing international survey of trace elements and their isotopes in seawater will undoubtedly increase our understanding of the deposition, biogeochemical cycling and fate of this enigmatic, sometimes toxic, sometimes beneficial heavy metal.
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We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an assessment of whether such contamination represents a real risk to the city's inhabitants and therefore how this risk can be addressed.
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This article describes the magnitude of U.S. lead (Pb) additives in gasoline from 1927 to 1994 and estimated quantities of Pb dispersed by vehicle traffic in eight urbanized areas (UAs) of California from 1950 to 1982. The findings are the basis for predicting the health impact of Pb on children living in UA of California. Quantitative U.S. national data for 1927-1994 were from the U.S. Senate hearing of the 1984 Airborne Lead Reduction Act. Vehicle traffic data, fuel efficiency, percentage leaded gasoline, and quantities of Pb in gasoline were obtained for 1982 from public and corporate records to estimate vehicle Pb emissions for small to very large UAs of California. California fuel consumption records and yearly quantities of Pb additives per gallon were the basis for estimating the 1950-1982 dispersion of Pb in each UA. Lead additives were calculated by multiplying annual vehicle fuel used by average Pb per gallon. The proportion of Pb additive for each UA was calculated from vehicle miles traveled (VMT) driven in 1982 divided by miles per gallon fuel consumption times the ratio of leaded to unleaded fuel times Pb additive per gallon. U.S. Environmental Protection Agency calculations of the fates of Pb were used to estimate Pb aerosol dispersal in each UA. About 108 billion miles of travel in 1982 within 8 UAs accounts for 3200metric tons of Pb additives or approximately 60% total Pb additives in California. Between the 1950-1982 peak of Pb additives, about 258,000metric tons are accounted for out of the state 412,000metric tons total during the same time period. The estimates of the quantities of Pb dust that accumulated within various UAs in California assists with predicting the continuing influences of Pb on children's exposure. Mapping the soil Pb reservoir assists with establishing the priority for enhancing environments of children.
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In this study we estimated the number of housing units in the United States with lead-based paint and lead-based paint hazards. We included measurements of lead in intact and deteriorated paint, interior dust, and bare soil. A nationally representative, random sample of 831 housing units was evaluated in a survey between 1998 and 2000; the units and their occupants did not differ significantly from nationwide characteristics. Results indicate that 38 million housing units had lead-based paint, down from the 1990 estimate of 64 million. Twenty-four million had significant lead-based paint hazards. Of those with hazards, 1.2 million units housed low-income families (< 30,000 US dollars/year) with children under 6 years of age. Although 17% of government-supported, low-income housing had hazards, 35% of all low-income housing had hazards. For households with incomes greater than or equal to 30,000 US dollars/year, 19% had hazards. Fourteen percent of all houses had significantly deteriorated lead-based paint, and 16% and 7%, respectively, had dust lead and soil lead levels above current standards of the U.S. Department of Housing and Urban Development and the U.S. Environmental Protection Agency. The prevalence of lead-based paint and hazards increases with age of housing, but most painted surfaces, even in older housing, do not have lead-based paint. Between 2% and 25% of painted building components were coated with lead-based paint. Housing in the Northeast and Midwest had about twice the prevalence of hazards compared with housing in the South and West. The greatest risk occurs in older units with lead-based paint hazards that either will be or are currently occupied by families with children under 6 years of age and are low-income and/or are undergoing renovation or maintenance that disturbs lead-based paint. This study also confirms projections made in 2000 by the President's Task Force on Environmental Health Risks and Safety Risks to Children of the number of houses with lead-based paint hazards. Public- and private-sector resources should be directed to units posing the greatest risk if future lead poisoning is to be prevented.
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This study characterizes the elemental composition of street dust and soils in Avilés (N. Spain), a medium-size city of approximately eighty thousand inhabitants, where industrial activities and traffic strongly affect heavy metal distribution. A total of 112 samples of street dust were collected within a 7-km(2) area, encompassing residential and industrial sites (ferrous and non-ferrous plants). Elevated geometric mean concentrations of zinc (4,892 microg x g(-1)), cadmium (22.3 microg x g(-1)), and mercury (2.56 microg x g(-1)) in street dust were found in samples located near industrial areas. Two types of anthropic influence were distinguishable: the first and most important one is that related to metallurgical activity and transportation of raw materials for local industries. Secondly, exhaust emissions from traffic are an important source of lead concentration in areas with high vehicular density (geometric mean: 514 microg x g(-1)). The zinc content in the dust samples decreased with the distance from a zinc smelter located in the northern part of the city. The same trend was found for other elements in association with zinc in the raw materials used by the smelter, such as cadmium and mercury. A simultaneous research campaign of urban soils, that involved the collection of 40 samples from a 10-km(2) area, revealed geometric mean concentrations of 376 microg x g(-1) Zn, 2.16 microg x g(-1) Cd, 0.57 microg x g(-1) Hg, and 149 microg x g(-1) Pb, and distribution patterns almost identical to those found for street dust.
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To thoroughly investigate the metal contamination around chromated copper arsenate (CCA)/polyethylene glycol (PEG)-treated utility poles, a total of 189 soil samples obtained from different depths and distances near six treated poles in the Montreal area (Canada) were analyzed for Cu, Cr, and As content. Various soil physicochemical properties were also determined. Ground water samples collected below the poles were analyzed for metals and bioassays with Daphnia magna were conducted. Generally, sandy soils had lower contaminant levels than clayey and organic soils. Copper concentrations in soil were highest followed by As and Cr. The highest Cu (1460 +/- 677 mg kg(-1)), As (410 +/- 150 mg kg(-1)), and Cr (287 +/- 32 mg kg(-1)) concentrations were found at the ground line and immediately adjacent to the pole. Contaminant levels then decreased with distance, approaching background levels within 0.1 m from the pole for Cr and 0.5 m for Cu and As. Chromium and Cu levels generally approached background levels at a depth of 0.5 m. Average As content near the pole on all study sites was three to eight times higher than Quebec's Level C criterion (50 mg kg(-1)), although it dropped to 31 mg kg(-1) at 0.1 m. Results also showed that As persisted up to 1 m in soil depth (17-54 mg kg(-1)). Copper and Cr concentrations in ground water samples were always <1.000 mg L(-1) and <0.05 mg L(-1), respectively and Cr(VI) was <0.02 mg L(-1). One sample contained an As concentration >0.025 mg L(-1) but bioassays showed that, overall, ground water had a low ecotoxic potential.
Book
This book covers the general principles of the occurrence, analysis, soil chemical behaviour and soil-plant-animal aspects of heavy metals and metalloids, followed by more detailed coverage of 21 elements: antimony, arsenic, barium, cadmium, chromium, cobalt, copper, gold, lead, manganese, mercury, molybdenum, nickel, selenium, silver, thallium, tin, tungsten, uranium, vanadium and zinc. This third edition of the book has been completely rewritten by mainly new authors and is now divided into three sections: 1: Basic Principles 2: Key Heavy Metals and Metalloids 3: Other Heavy Metals and Metalloids of Potential Environmental Significance The scope has been widened with four new chapters in Section 1 dealing with toxicity in soil organisms, soil-plant relationships, heavy metals and metalloids as micronutrients for plants and/or animals, and the modelling of critical loads of heavy metals for use in risk assessment and environmental legislation. This book will be of great value to advanced undergraduate and postgraduate students, research scientists and professionals in environmental science, soil science, geochemistry, agronomy, environmental health and environmental engineering, including specialists responsible for the management and clean-up of contaminated land.
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In order to select appropriate amendments for cropping hyperaccumulator or normal plants on contaminated soils and establish the relationship between Cd sorption characteristics of soil amendments and their capacity to reduce Cd uptake by plants, batch sorption experiments with 11 different clay minerals and organic materials and a pot experiment with the same amendments were carried out. The pot experiment was conducted with Sedum alfredii and maize (Zea mays) in a co-cropping system. The results showed that the highest sorption amount was by montmorillonite at 40.82 mg/g, while mica was the lowest at only 1.83 mg/g. There was a significant negative correlation between the n value of Freundlich equation and Cd uptake by plants, and between the logarithm of the stability constant K of the Langmuir equation and plant uptake. Humic acids (HAs) and mushroom manure increased Cd uptake by S. alfredii, but not maize, thus they are suitable as soil amendments for the co-cropping S. alfredii and maize. The stability constant K in these cases was 0.14-0.16 L/mg and n values were 1.51-2.19. The alkaline zeolite and mica had the best fixation abilities and significantly decreased Cd uptake by the both plants, with K > or = 1.49 L/mg and n > or = 3.59.
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Urban gardens provide affordable fresh produce to communities with limited access to healthy food but may also increase exposure to lead (Pb) and other soil contaminants. Metals analysis of 564 soil samples from 54 New York City (NYC) community gardens found at least one sample exceeding health-based guidance values in 70% of gardens. However, most samples (78%) did not exceed guidance values, and medians were generally below those reported in NYC soil and other urban gardening studies. Barium (Ba) and Pb most frequently exceeded guidance values and along with cadmium (Cd) were strongly correlated with zinc (Zn), a commonly measured nutrient. Principal component analysis suggested that contaminants varied independently from organic matter and geogenic metals. Contaminants were associated with visible debris and a lack of raised beds; management practices (e.g., importing uncontaminated soil) have likely reduced metals concentrations. Continued exposure reduction efforts would benefit communities already burdened by environmental exposures.
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To determine the mobility of natural radionuclides in boreal forest soil, a five-step sequential extraction procedure was carried out on soil samples taken from various depths down to 3 m on Olkiluoto Island, Finland, where there are plans to construct a spent nuclear fuel disposal repository in the bedrock. The extracted fractions studied were exchangeable, acid-soluble, reducible, oxidizable and tightly bound. It was found that the extractability of most of the radionuclides studied was dependent on the sample grain size and depth. All the elements were concentrated in the smallest grain size samples (<0.063 mm). The extraction behaviour of Th, however, did not vary with sample depth, and only about 10% of the Th was extracted by the time of the final extraction step. Stable Pb and 210Pb, as well as Ba and Ra concentrations were strongly correlated in the extractions. Radium and Ba were leached more readily than the other elements; approximately 17% of the total Ra was found in the first fraction extracted, representing exchangeable ions. Uranium was more mobile in the topsoil horizons than in the lower horizons. In the topsoil samples, an average of 51% of the extractable U was leached in the second extraction step, representing the elements soluble in weak acids, whereas only 13% of the U in the subsoil samples was extracted in this step. This is probably due to changes in soil redox conditions lower down the soil profile. The extraction behaviour of Pb and Fe also suggests the presence of more reducing conditions in the deeper soil horizons, because the percentage of extractable Pb and Fe in the oxidizable fraction increased with sample depth.