Critical Reviews in Environmental Science and Technology

Published by Taylor & Francis
Online ISSN: 1064-3389
Publications
Article
Cadmium (Cd) is one of the most toxic and widely distributed pollutants in the environment. Cadmium contamination of soils has posed a serious threat to safe food production in many parts of the world. The authors present a comprehensive review of present status of phytoextraction technology for cleaning up Cd-contaminated soils, based primarily on the data resulting from both laboratory and field-scale studies that have been conducted to assess or improve the Cd phytoextraction potential of various plant species in the past decade. The encouraging results of field-scale studies have provided a fundamental basis to usher phytoextraction technology into practical use to remediate slightly to moderately Cd-contaminated soils in Europe and Asia, although this technology is not yet ready for widespread application. Chelators and microorganisms tested so far seem not to contribute to the applicability of Cd phytoextraction. The major challenges for the large-scale application of Cd phytoextraction are (a) how to further improve the efficiency of Cd phytoextraction, (b) how to cut the overall costs of Cd phytoextraction, and (c) how to get greater stakeholders' acceptance of Cd phytoextraction as a reliable option.
 
Article
Anaerobic treatments have been successfully employed for more than one hundred years to stabilize sewage sludge. The main aim of sludge anaerobic digestion is the degradation and destruction of organic matter, with consequent sludge stabilization and pathogen reduction. One of the advantages of the fermentative system over aerobic treatment is the production of biogas (i.e., an available source of energy), which in some cases can be exploited to satisfy part of the energy requirements of the treatment plant. Nevertheless, inadequate knowledge of the principles governing the process often prevents satisfactory digester management, and thus there is an evident need for reliable kinetic models in order to improve performance and optimize the control strategies. In the present review, an overview of the anaerobic digestion models proposed in the specialized literature is presented. Models are grouped according to the degree of substrate characterization and thus of complexity (in terms of number of equations and parameters). This criterion is practically equivalent to considering that a chronological order exists in their evolution. To make the model comparison easier to use, a representation in matrix form is also given. The potential and limits of available models are also discussed with a view to defining both fundamental research needs and critical aspects for practical application.
 
Article
Gold mining is attracting increasing attention in many countries of the world, although it has a major impact on the environment. Large quantities of hazardous chemicals such as mercury or sodium cyanide are consumed to recover gold from its ores. Therefore, this activity should be carefully regulated by means of global directives based on an up-to-date knowledge of ecotoxicity principles and modern environmental standards. This article summarizes the basic information on past and present environmental impacts of gold production. Novel methods, possibly with reduced environmental risks, are briefly mentioned. Global regulatory criteria for minimization of the ecological and human health risks in mining, production, and processing facilities are proposed. Articles from different scientific disciplines distilled from the experiences of actual gold mining operations are cited. The most recent information gathered during the last 10 years of discussions regarding gold prospecting and recovery in Turkey has been added to them. gold mining environmental impacts of gold mining amalgamation cyanide leach process wastes global directives for gold mining
 
Article
Starting from the sampling up to the time of analysis, the content of water sample can be altered due to the chemical, physical, and biological reactions it undergoes. This article deals with the processes occurring in the water samples during their storage and with reasons of their occurrence. Special attention has been paid to the chemical and physicochemical reactions as well as to microbiological and photochemical degradation of the component of the sample. Techniques for the water sample preservation are also reviewed. degradation preservation storage samples
 
Article
Solid wastes containing sulfate are an important source of pollution, which can create a lot of environmental problems, especially during disposal management at landfill sites. These solid wastes, such as construction and demolition (C&D) debris and phosphogypsum, cause odor problems and possible health impacts to landfill employees and surrounding residents. These wastes do not only contain high sulfate concentrations, but also contain toxic metals and radioactive compounds. Although these wastes can be reused as soil amendment or to make building materials, a concern has been raised by regulators regarding to the chemical characteristics of the material and the potential risks to human health and the environment. Therefore, use of these solid wastes has been banned in most countries. In addition, soils containing solid sulfate (gypsum), namely gypsiferous soils, have several problems during agricultural development. Reduction of the sulfate content of these solid wastes, soils and sediments by biological sulfate reduction is an option to overcome the previously mentioned problems. The authors review the topics necessary for developing biological sulfate removal technologies from these sulfate rich solid wastes as well as soils and sediment types (i.e., their contamination by sulfate minerals, solid sulfate as an electron acceptor for sulfate reducing bacteria, and sulfate reduction processes both in natural and in bioengineered reactor systems).
 
Hierarchy for Solid Waste Management 
Cross-sectional view of an aerobic bioreactor with aeration and leachate recirculation 
Article
Historically, municipal solid waste landfills have been designed and operated as disposal facilities with suboptimal degradation under anaerobic conditions, resulting in slow waste stabilization and generation of landfill gas rich in methane and high strength leachate. Recently, aerobic bioreactor landfilling is being promoted as a promising method that enhances waste stabilization while producing a relatively weaker leachate and no methane generation. The authors review transformation processes and benefits associated with aerobic bioreactor landfilling. Factors affecting the operation of aerobic bioreactor landfills were detailed and performance indicators were defined with technical and operational considerations. The article emphasizes conditions for economic viability of the technology and concludes with outlining existing gaps and future research needs to improve the understanding and performance of aerobic bioreactor landfilling.
 
Article
Biorecalcitrant organic pollutants pose a threat to the aquatic environment due to their several detrimental traits. A host of industries as well as municipal facilities are liable to discharge such pollutants. These pollutants cannot be effectively managed by conventional biological and/or physiochemical treatment methods. Advanced oxidation processes, based on very strongly oxidizing free radicals such as hydroxyl radicals, have been found to be effective in destroying these pollutants often leading to their mineralization. This paper attempts to summarize the present state and emerging trends in advanced oxidation based treatment techniques. Reaction chemistries, process conditions, treatment efficiencies, and material and energy inputs required have been discussed.
 
Article
Advanced oxidation processes (AOPs) constitute important, promising, efficient, and environmental-friendly methods developed to principally remove persistent organic pollutants (POPs) from waters and wastewaters. Generally, AOPs are based on the in situ generation of a powerful oxidizing agent, such as hydroxyl radicals (•OH), obtained at a sufficient concentration to effectively decontaminate waters. This critical review presents a precise and overall description of the recent literature (period 1990–2012) concerning the main types of AOPs, based on chemical, photochemical, sonochemical, and electrochemical reactions. The principles, performances, advantages, drawbacks, and applications of these AOPs to the degradation and destruction of POPs in aquatic media and to the treatment of waters and waste waters have been reported and compared.
 
European emission standards for nitrogen oxides, hydrocarbons, and PM in diesel exhaust 
Hypothetical kinetic relationships between different biomarkers of exposure (Henderson et al., 1989).  
Exposure-response continuum showing the stages targeted by biomarker development (Manini et al., 2007). C Elsevier. Reproduced by permission of Elsevier. Permission to reuse must be obtained from the rightsholder.  
Article
The monitoring of human exposures to diesel exhaust continues to be a vexing problem for specialists seeking information on the potential health effects of this ubiquitous combustion product. Exposure biomarkers have yielded a potential solution to this problem by providing a direct measure of an individual's contact with key components in the exhaust stream. Spurred by the advent of new, highly sensitive, analytical methods capable of detecting substances at very low levels, there have been numerous attempts at identifying a stable and specific biomarker. Despite these new techniques, there is currently no foolproof method for unambiguously separating diesel exhaust exposures from those arising from other combustion sources. Diesel exhaust is a highly complex mixture of solid, liquid, and gaseous components whose exact composition can be affected by many variables, including engine technology, fuel composition, operating conditions, and photochemical aging. These factors together with those related to exposure methodology, epidemiological necessity, and regulatory reform can have a decided impact on the success or failure of future research aimed at identifying a suitable biomarker of exposure. The objective of this review is to examine existing information on exposure biomarkers for diesel exhaust and to identify those factors and trends that have had an impact on the successful identification of metrics for both occupational and community settings. The information will provide interested parties with a template for more thoroughly understanding those factors affecting diesel exhaust emissions and for identifying those substances and research approaches holding the greatest promise for future success.
 
Article
Pollution swapping occurs when a mitigation option introduced to reduce one pollutant results in an increase in a different pollutant. Although the concept of pollution swapping is widely understood, it has received little attention in research and policy design. This study investigated diffuse pollution mitigation options applied in combinable crop systems. They are cover crops, residue management, no-tillage, riparian buffer zones, contour grass strips, and constructed wetlands. A wide range of water and atmospheric pollutants were considered, including nitrogen, phosphorus, carbon, and sulfur. It is clear from this investigation that there is no single mitigation option that will reduce all pollutants.
 
Sources of airborne dust in animal houses
Initial infection region of microorganisms (Baskerville, 1981)
Common samplers for airborne microorganisms
Article
Large amounts of airborne microorganisms are emitted from livestock production. These emitted microorganisms may associate with dust, and are suspected to pose a risk of airborne infection to humans in vicinity and to animals on other farms. However, the extent to which airborne transmission may play a role in the epidemic, and how dust acts as a carrier of microorganisms in the transmission processes is unknown. The authors present the current knowledge of the entire process of airborne transmission of microorganisms—from suspension and transportation until deposition and infection—and their relation to dust. The sampling and the mitigation techniques of airborne microorganisms and dust in livestock production systems are introduced as well.
 
Article
Nitrate contamination of drinking water sources has become one of the most important water quality concerns across the United States. Nitrate presents unique water treatment challenges and small water systems are particularly affected by the high costs of addressing nitrate impacted supplies. The goal of this investigation was to provide an overview of nitrate treatment options, highlighting the most recent advances and elucidating costs and common problems in application. No single treatment option is ideal for all situations; new technologies continue to be investigated to effectively remove nitrate while limiting cost and maximizing sustainability.
 
A comparison of final sludge disposal locations in the United Kingdom, United States, and Japan as percentages of total sludge in surveys of water utilities. Adapted from Walsh (2009), UKWIR (1999), and Fujiwara (2011).  
Kinetic regions that occur as batch Donnan dialysis progresses. Adapted from Prakash and Sengupta (2004).  
Donnan equilibria-driven trivalent metal recovery across a cation-selective membrane . 1. Sweep-side acid protons move down their concentration gradient across the cationselective membrane, creating a charge imbalance across the membrane. 2. Acid counterions are rejected by the membrane, preventing them moving to correct the charge imbalance. 3. Trivalent metals move in the opposite direction to acid, neutralizing the transmembrane charge. 4. Organic material in the feed is rejected by the membrane due to its bulk and negative/neutral charge.  
Theorized electrodialysis recovery of trivalent coagulant metals. 1. Trivalent coagulant metals move from the acidified feed, towards the cathode, until their path is blocked by an anion-selective membrane. 2. Acid/coagulant counterions move from the acidified feed, towards the anode, until their path is blocked by a cation-selective membrane. 3. Despite having the correct charge, organic material in the feed is rejected by the membrane due to its bulk.  
Article
Conventional water treatment consumes large quantities of coagulant and produces even greater volumes of sludge. Coagulant recovery (CR) presents an opportunity to reduce both the sludge quantities and the costs they incur, by regenerating and purifying coagulant before reuse. Recovery and purification must satisfy stringent potable regulations for harmful contaminants, while remaining competitive with commercial coagulants. These challenges have restricted uptake and lead research towards lower-gain, lower-risk alternatives. This review documents the context in which CR must be considered, before comparing the relative efficacies and bottlenecks of potential technologies, expediting identification of the major knowledge gaps and future research requirements.
 
Article
This review examines the potential environmental impact of radiofrequency (RF) fields emitted by mobile phone base station antennas and other sources of RF radiation. Overall, many alarming investigations were found but most are characterised by severe methodological shortcomings. For this reason these studies do not provide any evidence that observed biological effects are associated with exposure to the electromagnetic fields. So far, the studies do not prove that environmental exposures to mobile phone base station radiation (and other environmental RF exposures) are harmful to wildlife.
 
Article
Sulfate-rich wastewaters are generated by many industrial processes that use sulfuric acid or sulfate-rich feed stocks (e.g., fermentation or sea food processing industry). Also, the use of reduced sulfur compounds in industry, that is, sulfide (tanneries, kraft pulping), sulfite (sulfite pulping), or thiosulfate (pulp bleaching, fixing of photographs), contaminates wastewaters with sulfate. A major problem for the biological treatment of sulfate-rich wastewaters is the production of H2S. Gaseous and dissolved sulfides cause physical (corrosion, odor, increased effluent COD) or biological (toxicity) constraints that may lead to process failure. H2S is generated by sulfate-reducing bacteria, in both anaerobic and aerobic (anoxic microenvironments) wastewater treatment systems. No practical methods exist to prevent sulfate reduction. Selective inhibition of SRB by molybdate, transition elements, or antibiotics is unsuccessful at full scale. Selection of a treatment strategy for a sulfate-rich wastewater depends on the aim of the treatment. This can be (1) removal of organic matter, (2) removal of sulfate, or (3) removal of both. Theoretically, wastewaters with a COD/sulfate ratio of 0.67 or higher contain enough COD (electron donor) to remove all sulfate by sulfate-reducing bacteria. If the ratio is lower, addition of extra COD, for example, as ethanol or synthesis gas (a mixture of H2, CO2, and CO) is required. Complete COD removal in wastewaters with a COD/sulfate ratio of above 0.67 also requires methanogenic COD degradation. Methods to reduce sulfide toxicity and to allow optimal COD removal are presented. Sulfate can be removed from the wastestream by the coupling of a sulfide oxidation step to the sulfate reduction step. Sulfur can be recovered from the wastewater in case H2S is partially oxidized to insoluble elemental sulfur.
 
Article
Closed forests cover about 3 billion hectares, or 20% of the world's total land area (excluding Antarctica). Forest plantations comprise less than 1% of this area. Natural forests range from the intensively managed ones of Central Europe and Scandinavia to the wild boreal forests of Russia and Canada and the deep jungles and dry forests of the tropics. Numerous techniques—largely drawn from the ordinary repertoire of forest management—are available to enhance our ability of these forests to sequester and store C. Although the costs of sequestering additional C in these forests may be quite low (even in comparison with intensive plantation options), increased use of natural forests for this purpose raises a host of concerns about competing forest uses, biological risk, and the capacity to actually measure the incremental C sequestered. The problems of poverty, expanding populations, weak institutions, incomplete scientific knowledge, and climatic change itself will challenge the world's capacity to use natural forests as part of a CO2 control strategy.
 
Article
Global climate change is about uncertainty related to ecological and economic processes, and political responses. It is about fairness and income distribution among nations, both now and in the future. It is a dynamic problem that involves national carbon transition functions, damage functions and discount rates. These issues form the basis of the current paper, which examines them from a conceptual point of view.
 
Article
This review provides a comprehensive overview about nonextractable residue (NER) formation and attempts to classify the various types. Xenobiotic NER derived from parent pesticides (or other environmental contaminants) and primary metabolites sorbed or entrapped within the soil organic matter (Type I) or covalently bound (Type II) pose a considerably higher risk than those derived from productive biodegradation. However, biogenic nonextractable residues (bioNER) (Type III) resulting from conversion of carbon (or nitrogen) from the compounds into microbial biomass molecules do not pose any risk. Experimental approaches to clearly distinguish between the types are provided, and a model to prospectively estimate bioNER formation in soil is proposed.
 
Hypothesized ecological succession of microorganisms on new concrete surface exposed to H 2 S. (After Islander et al., 1991.)
Flow scheme of a packed scrubber. (After Carleton and Valentin, 1980.)
Flow scheme of a dual activated carbon bed. (After Turk et al., 1993.)
Article
Due to their very low odor threshold value (ppbv range), high toxicity, and potential corrosive effect, the presence of volatile sulfur compounds in waste gases deserves special attention. These sulfur compounds mainly include hydrogen sulfide, dimethyl sulfide, dimethyl disulfide, meth-anethiol, carbon disulfide, and carbonyl sulfide. Contrary to natural emissions, anthropogenic emissions may contribute to local concentrations, strongly exceeding the odor threshold value. These anthropogenic sources mainly include these processes where anaerobic degradation of organic matter can occur (e.g., waste water treatment and composting plants) and processes where organic matter is heated (e.g., thermal sludge-treatment plants). Industrial applications of volatile sulfur compounds (e.g., for viscose rayon manufacturing) and their production during chemical reactions (e.g., in the Kraft paper pulping process) can also lead to high local atmospheric concentrations. An overview of abatement technologies for aerobic waste gases containing these compounds is presented, including both physicochemical (scrubbing, adsorption, etc.) and biotechnological (biofiltration, biotrickling filtration) methods.
 
Article
Data on the levels of persistent lipophilic contaminants and other chemicals have been reviewed and the dominant persistent lipophilic contaminants in the Southern Hemisphere found to be the chlorohydrocarbons commonly described as the DDTs, HCHs, and the PCBs. The distribution patterns suggest that long-range transport, probably by global distillation, occurred with these substances. Endosulfan residues appear significant in areas of usage but the data are limited. The data are in accord with a reduction in usage of chlorohydrocarbons in developed countries, but an increase in usage in many tropical countries. A systematic comparison of data on the northern and southern hemispheres indicates that the northern hemisphere is generally more contaminated than the southern hemisphere. It also suggests that the process of equilibration between the two hemispheres is relatively slow. In addition, with the HCBs there is an equatorial to polar gradation in concentration probably as a result of global distillation. With the HCHs relatively high concentrations exist in the tropics, probably due to their heavy usage in these regions. With the HCBs, DDTs, and PCBs the concentrations appear to be more localized in relation to the sources because these substances are less volatile than the compounds mentioned previously.
 
Article
http://www.tandfonline.com/eprint/ihPCEu58NfbJ39xyM3PC/full This paper presents a state-of-the-art review of natural wastewater treatment technologies selected from the point of view of sustainability and relates them to feasible reuse and disposal practices available for food processing wastewater. Selected technologies include land application, constructed wetlands, and various pond systems that all make use of natural processes. The aim of the review is to help understand issues controlling wastewater reuse and how the different natural treatment systems and their combinations could help us to protect the environment, meet regulations, and conserve water, material, and energy resources.
 
Article
The impact of potential pathogenic foodborne Salmonella spp. in poultry production environments is of paramount importance, considering its implications for human health. Most of what is known about this organism under these environmental conditions is based on indirect evidence. The overall focus of this review is on the biology of potentially pathogenic foodborne Salmonella spp. in poultry environments. This is not just because of the implications regarding pathogenic Salmonella spp. for poultry production and food safety but because Salmonella spp. behavior may serve as a model for understanding general bacterial pathogen persistence in animal agricultural environments. This will help meet a long-term need to develop a comprehensive ecological picture of the contamination potential, growth, survival, and genetic stability of pathogens in poultry and other animal production environments. This will in turn lead to a better understanding of the environmental and health impacts of foodborne Salmonella spp. dissemination in animal production environments.
 
Article
Online drinking water quality monitoring technologies have made significant progress for source water surveillance and water treatment plant operation. The use of these technologies in the distribution system has not been favorable due to the high costs associated with installation, maintenance, and calibration of a large distributed array of monitoring sensors. This has led to a search for newer technologies that can be economically deployed on a large scale. This paper includes a brief description of important parameters for drinking water and current available technologies used in the field. The paper also provides a thorough review of the advances in sensor technology for measurement of common water quality parameters (pH, turbidity, free chlorine, dissolved oxygen, and conductivity) in drinking water distribution systems.
 
Article
Wind-driven surficial oxygen transfer into stationary water bodies has become increasingly important because the fate of many pollutants in these water bodies is strongly influenced by oxygen mass transfer. There are many existing correlations that can be used for predicting wind-driven surficial oxygen transfer; however, the actual prediction has been difficult because there are large variations among numerous predictive transfer coefficient correlations. As a result, selecting an equation that can relate well to certain application conditions becomes critical for accurately predicting surficial oxygen transfer rates. To facilitate the selection process, this article critically reviews and analyzes many of wind-driven surficial oxygen transfer coefficient correlations published during the last five decades. These correlations are for oxygen and other pertinent gas transfer into nonmoving, open water bodies. Empirically derived oxygen coefficients were evaluated using the data derived from investigations in controlled wind tunnels, floating reaeration devices in open waters, and natural open waters. To compare these gas transfer coefficient correlations, gases were normalized to oxygen, and wind speeds were normalized to 10-m height. Generally, low wind speed did not significantly influence the transfer coefficients; however, the transfer coefficients increased, even exponentially, with higher wind speeds. Recently, a new unified equation was developed based on the gas transfer data published in the last five decades to estimate surficial oxygen transfer into stationary water bodies. Although this new equation satisfactorily fits the 50-year data using wind speed as a major variable, the effects of other environmental factors such as wind direction, solid contents, and precipitation need further research.
 
Article
Phosphorus is known to be an important contributor to eutrophication of aquatic systems,11. Elser, J. J., Bracken, M. E. S., Cleland, E. E., Gruner, D. S., Harpole, W. S., Hillebrand, H., Ngai, J. T., Seabloom, E. W., Shurin, J. B., and Smith, J. E. (2007). Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems. Ecology Letters, 10, 1135–1142.[CrossRef], [PubMed], [Web of Science ®]View all references but the role of organic phosphorus is often overlooked. This review uses a meta-analysis approach to investigate inorganic and organic phosphorus in organic fertilizers, soils and waters, including the quantification of organic phosphorous forms such as monoesters, diesters, and inositol hexakisphosphate. Across these media, organic phosphorus comprised 22–46% of the total phosphorus (by mass of phosphorus). Bioavailable organic phosphorus appears to be more mobile than recalcitrant forms. Organic phosphorus may represent a significant risk for eutrophication, and the risk may vary according to the season, but conclusions are hampered by a lack of data.
 
Article
The use of chemicals by society has many benefits but contamination of the environment is an unintended consequence. One example is the organochlorine compound hexachlorocyclohexane (HCH). During the 1980s, when HCH was banned in many countries, the brominated flame retardant, hexabromocyclododecane (HBCD), found increasing use. The persistent, bioaccumulative, and toxic characteristics of HBCD are, 30 years later, likely to warrant global action on production and use under the Stockholm Convention on persistent organic pollutants. Historical lessons have taught us that we need to control the use of chemicals and programs are in place worldwide in an attempt to do so.
 
Article
This paper provides a review of the up-to-date research on the treatment of micropollutants by UV-based processes. More than 140 scientific publications in the past 10 years were reviewed and analyzed, with emphasis on the peer-reviewed papers in the last three years (2009–2011). Previous studies showed that UV-based advanced oxidation processes (AOPs) could be efficient for the removal of a number of micropollutants in drinking water and wastewater although direct UV photolysis at disinfection dosages was proven not effective in removing most micropollutants. Among those UV-based AOPs, UV-oxidation with hydrogen peroxide (H2O2) has attracted great attention and shown numerous advantages as an advanced technology for micropollutants control. The public concern about the impact of micropollutants on the safety of drinking water and the increasing needs of safe water reuse will likely facilitate the application of UV-based processes for micropollutants control in drinking water treatment and water reuse.
 
Schematic representation of a typical two chamber microbial fuel cell. (Color figure available online). 
Article
Human population growth has led to accumulation of large amount and variety of wastes, which take many decades to degrade and also release toxicity during degradation. A sustainable solution is required to treat these wastes to prevent our future population from environmental hazards. Recently, microbial fuel cell (MFC) technology has emerged as a potentially promising future technology for the production of energy from organic material present in wastewaters, thus ensuring dual benefits: waste treatment and energy production. In the present review the authors discuss the wider aura of wastewater treatment capabilities of MFCs and their future challenges to overcome to explore the opportunities for future MFCs.
 
Article
The author reviews the current state of recent microbial community studies conducted on lab-pilot-full scale agricultural biogas digesters fed with energy crops operated in mono- and codigestion modes with or without use of manure as cosubstrate. It is commonly concluded by researchers that methane (CH4) formation mostly resulted from conversion of hydrogen (H2) and carbon dioxide (CO2), rather than aceticlastic methanogenesis. Hydrogenotrophic methanogenesis seems to be the major pathway for formation of methane from energy crops in agricultural biogas digesters.
 
Article
As a result of the industrialization and urbanization in the world, human pressure on the environment is intensifying, leading to detrimental changes in both biotic and abiotic compartments. One of the many consequences of this state of affairs is the increasing rate of emission into the atmosphere of volatile organic compounds, including the so-called BTEX (benzene, ethylbenzene, toluene, xylenes) compounds. The authors review the main sources of BTEX compounds in ambient air and the impact on the photochemistry and individual elements of the environment (water, air, soil, living organisms). Potential transport mechanisms, which include transpiration, distribution, bioaccumulation, biodegradation, are described. The authors present the characteristic mechanisms of radical reactions and gives a view on environmental fate of BTEX compounds in the atmosphere. The article comprises the concentration of BTEX compounds both in rural and industrial areas of different parts of world, showing the scale of existing emissions of BTEX compounds to the atmosphere.
 
General classification of methods used for sampling and analysis of gas samples. 
Classification of volatile organic compounds with respect to their characteristics.
Sampling and analytical procedures for the determination of VOC in air
Article
Volatile organic compounds (VOC) are the total organic compounds that contribute to photochemical ozone formation. They have a vapor pressure greater than 0.013 kPa at 298 K (according to the American Society for Testing and Materials (1996)), 0.01 kPa at 293 K (according to the European Union (1999)), or 10 Pa at 298 K (according to the U.S. Environmental Protection Agency (1999)), with a lower boiling point limit of 50–100°C and an upper boiling point limit of 240–260°C. VOC include countless potentially hazardous substances released to the outdoor or indoor environment. The prevention or reduction of exposure to VOC in the air requires qualitative and quantitative analysis of these chemical agents. A correct assessment of human exposure to VOC requires appropriate and efficient methods of sampling and analysis. The authors present a survey of VOC definitions, an analytical discussion of the necessity and viability of exposure studies, the principal VOC studied, and a critical revision of methods of sampling and analyses.
 
Article
Ammonia oxidation is a central step in the global nitrogen cycle that involves several different-conditions and metabolic bioprocesses, including aerobic versus anaerobic ammonia oxidation, and autotrophic versus heterotrophic ammonia oxidation. With the development and application of metagenomics and other modern molecular approaches, some new organisms (particularly ammonia-oxidizing archaea) and novel pathways related to ammonia oxidation have been identified. Consequently, the understanding of nitrogen cycling processes and the microorganisms that mediate them have been greatly improved. Here the authors summarize the biochemistry, microbiology, and ecophysiology of these organisms (including autotrophic ammonia-oxidizing bacteria, heterotrophic nitrifying bacteria, anaerobic ammonia-oxidizing bacteria, and ammonia-oxidizing archaea) and discuss the current knowledge and important concepts associated with their corresponding pathways. Factors influencing their distribution, abundance, community structure and potential ammonia oxidation rates in natural and engineered ecosystems are also addressed. Furthermore, the mechanism of nitrous oxide emission during these processes and the specific control strategies are explained or proposed. The significant roles of these organisms in novel biological wastewater treatment processes are also evaluated. Finally, several urgent issues and significant perspectives related to these novel pathways and players have been addressed to evoke the involvement of researchers in broadening future studies.
 
Article
Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) is promoted as an energy source and more recently as a greenhouse gas (GHG) mitigation measure. In this context, AD systems operating at thermophilic temperatures (55–60°C)—compared to mesophilic temperatures (35–40°C)—have the unique feature of producing hygienic soil conditioners with greater process efficiency, higher energy yield, and more GHG savings. Startup of AD systems is often constrained by the lack of acclimated seeds, leading to process instability and failure. The authors focus on strategies to startup thermophilic digesters treating OFMSW in the absence of acclimated seeds and examines constraints associated with process stability and ways to overcome them. Relevant gaps in the literature and future research needs are delineated.
 
Published antimony concentrations (in μ g/L) in serum and plasma of healthy individuals. (a) Box-and-whisker plot showing the median and the 25th and 75th percentiles (box), nonoutlier maximum and minimum values (whiskers), and outliers (more or less than 2–3 times the upper or lower quartile). Quartile option: Excel. (b) Values represented in chronological order (as they appear in Table 1) showing the technique used. (c) Same values showing the type of sample pretreatment. Outliers have not been represented in (b) and (c) (Color figure available online). 
Published antimony concentrations (in μ g/L) in whole blood of healthy individuals. (a) Box-and-whisker plot (see meaning in legend of Figure 1). (b) Values represented in chronological order (as they appear in Table 2) showing the technique used. (c) Same values showing the type of sample pre-treatment. Outliers have not been represented in (b) and (c) (Color figure available online). 
Article
The authors present an evaluation of published antimony concentrations in human blood. It is the last installment of a series of studies on the use different biological tissues in human biomonitoring that have appeared in Critical Reviews in Environmental Science and Technology. The objective was to assemble and evaluate published data from a methodological point of view and establish, if possible, a range of plausible values for antimony concentrations in whole blood and plasma and/or serum for nonexposed humans. Determining the concentration of antimony in blood is far from straightforward because samples are highly prone to contamination and values are low, close to the detection limits of the techniques available. In combination with the lack of adequate certified reference materials, this makes it impossible to establish a value for antimony content in the blood of healthy, non-exposed individuals based on published values. However, more recent results have opened up the possibility of suggesting a concentration ceiling of around 1 μg L–1. The review includes a detailed discussion of the main problems encountered in determining antimony in this complex matrix that may prove useful as a guide for future work.
 
Schematic illustration of the sources of road-deposited sediments (adapted from Taylor, 2007). 
Sources of major organic pollutants and pollutant concentration or emission rate
Examples of factors influencing pollutants concentrations in RDS and neighboring soils. (a) Distance from road (Pt and Pd in Germany, Zereini et al., 2007; Pb in Jordan, Massadeh et al., 2004). (b) Distance from road (Pb), lierature summary of 10 studies (Sutherland and Tolosa, 2001). (c) Traffics volume (in Sydney, Australia, AADT-Annual average daily traffic; Davis and Birch, 2011). (d) Road site difference (GR [general rotary], RR [riverside rotary], HW [highway], CR [circulation road], DT [downtown area], BG [background], Korea; Duong and Lee, 2011). (e) Temporal variability (Manchester, England; Robertson and Taylor, 2007). (f) RDS particle size (Korea; Duong and Lee, 2009; redrawn from references cited in the figure captions) (Color figure available online). 
Sources of major inorganic pollutants and pollutant concentration/or emission rate
Approaches used for pollutant source identification and apportionment
Article
Road-deposited sediments (RDS) often contain elevated concentrations of inorganic and organic pollutants such as heavy metals, metalloids, and polycyclic aromatic hydrocarbons. The authors trace new developments and trends on RDS pollutant characteristics with respect to their distribution in time and space, total and labile fractions in the different particle size and density fractions, source apportionment, and chemical speciation, as well as on the management of the pollutants. Recent research provides more reliable information to understand pollutants’ origin, bioavailability, transport pathways, and methods to minimize their risks. Use of special chemical, physical, mineralogical, and statistical methods has contributed to a better understanding of source apportionment of many of the pollutants but more research is needed on others. The degree of accumulation of pollutants in RDS that are derived from roads and vehicles has been quantified by using enrichment factors. Many of the studies on RDS pollutant management dealt with reducing pollutants by road sweeping and water flushing but these have not been found to be very effective. Pollutants that enter the water bodies through stormwater runoff need to be removed to protect the aquatic environment in the receiving water. The current knowledge on stormwater treatment methods to remove pollutants is also presented.
 
Article
The Lemna bioassay is one of the most standardized higher plant bioassays for assessing the impacts of contaminants in aquatic environments. The simple anatomy and ease with which Lemna sp. can be handled makes them ideal test organisms. They have been used to predict the cytotoxic, cytogenetic, and mutagenic effects of several chemical pollutants including, inter alia, polycyclic aromatic hydrocarbons, heavy metals, metalloids, organometallic compounds, pesticides, pharmaceuticals, radionuclides, and pharmaceuticals. However, there is still some contention as to the exact scope of application and definition of the Lemna bioassay regarding its accuracy of prediction and toxicity assessment. In this article, we review some critical issues on the development and effective use of the Lemna bioassay.
 
Overview of test species used in internationally accepted sediment toxicity tests with benthic invertebrates (ASTM, EPA, ISO and OECD)
Overview of methods for prospective sediment toxicity testing with microorganisms. 
Characteristics of the micro-and mesocosm studies evaluated in this review
Article
Sediment toxicity tests play an important role in prospective risk assessment for organic chemicals. This review describes sediment toxicity tests for microorganisms, macrophytes, benthic invertebrates, and benthic communities. Current approaches in sediment toxicity testing are fragmentary and diverse. This hampers the translation of single-species test results between freshwater, estuarine and marine ecosystems and to the population and community levels. A more representative selection of species and endpoints as well as a unification of dose metrics and exposure assessment methodologies across groups of test species, constitutes a first step toward a balanced strategy for sediment toxicity testing of single organic compounds in the context of prospective risk assessment.Supplementary materials are available for this article. Go to the publisher's online edition of Critical Reviews in Environmental Science and Technology for the supplemental material.
 
Article
Metals being recalcitrant to biodegradation process pose a persistent threat to human health and environment. In view of increase in discharge along with improper management of persistent metal pollutants, it is imperative to develop cost-effective and efficient methods for their remediation. As contamination of soil and water has threatened the well being of humans and natural environment, microorganisms play crucial role in combating the widespread pollution of global environment. Clusters of genes coding for catabolic transformation facilitate their detoxification from the environment. Development of effective tools to facilitate environmental cleanup of metal pollutants beyond genetic confines of natural host has resulted in the expressional enhancement of promiscuous enzymes, involved in the transformation of metal compounds. A thorough understanding of microbes that express heterologous proteins for metal transformation would result in economic production and as such its application in bioremediation process. This review summarizes fundamental insights regarding metals in relation to oxidative stress, insights on metal binding proteins/peptides for immobilization, information regarding genetic engineering for enzymes involved in metal transformation, and strategies that can be employed to overcome the bottlenecks associated with microbial based remediation strategies.
 
Comparison of N 2 O uptake database in rice and non-rice agricultural soils. 
Nitrous oxide biogeochemistry in a submerged rice field (modified from Majumdar, 2000). 
N 2 O-N remaining in the flask headspace after consumption with time in various soils. (Color figure available online). 
Factors affecting N 2 O consumption and uptake in submerged rice soils (continued) Factor Suggested mechanisms 
Article
Submerged soils and rice fields are known sources of nitrous oxide (N2O) but also act as its sinks. Nitrous oxide uptake (movement from atmosphere into soil) and consumption (conversion of N2O to N2) in rice fields are both very significant, as they help decrease N2O concentration in the atmosphere. Rice soils had reportedly shown N2O uptake ranging from about 0.13 to 191 μg N2O-N m−2 hr−1 while in non-rice soils the same was about 0.0014–484 μg N2O-N m−2 hr−1. This review synthesizes the available information on N2O uptake and consumption in submerged soils vis-à-vis rice fields.
 
Article
Bioremediation as a sustainable alternative to chemical-physical processes is an attractive solution for soil decontamination and renewal of polluted sites. Depending on the site characteristics and target treatment requirements for the decontaminated soil, in situ or ex situ technologies are employed. Ex situ technologies are advantageous when a safe and effective intervention is required (i.e., in the presence of severe contamination of highly hazardous compounds). In this review, conventional and innovative ex situ technologies for soil bioremediation are presented. For each one the principle of operation and recent applications are reported. In addition, strategies to improve their efficiency are explored. Finally, the possibility of making these technologies more competitive by indicating research needs for their future development is highlighted.
 
Article
Chloronitrobenzenes and chloroanilines are among the recalcitrant, toxic environmental contaminants that pose chronic threat to the health and safety of humans and wildlife. Pentachloronitrobenzene (PCNB) is an emerging environmental chloronitroaromatic contaminant, widely distributed in the environment due to its worldwide intensive use. The interactions between potentially competing microbial processes (i.e., iron reduction, nitrate reduction, methanogenesis, and dechlorination) can significantly influence the environmental fate of PCNB and chloroanilines resulting from the reductive biotransformation of PCNB. This review evaluates presently available toxicity and distribution information as well as the transformation and degradation potential of PCNB and chloroanilines under different environmental conditions.
 
Article
Carbon nanotubes (CNTs) are the engineered nanomaterial that has a very simple chemical composition and structure. Extremely high aspect ratios, molecularly smooth hydrophobic graphitic walls, and nanoscale inner diameters of CNTs give rise to the peculiar adsorption properties. This review provides an overview on CNTs functionalization and their application as an adsorbent for scavenging heavy metals and radionuclide from wastewater systems. A summary of recent information obtained using batch studies and deals with mechanisms involved during the adsorption have been reported. Adsorption capacity of CNTs has been observed by numerous investigators to increase substantially after functionalization/treatment with oxidizing agents such as NaOCl, HNO3, H2SO4, KMnO4, and other oxidizing agents. However, the selectivity of CNTs toward metal ions depends on both the route used for their synthesis and reagent employed for purification. The recovery of metal ions and the regeneration of CNTs have minimal impact on their performance. Desorption of metal ions from saturated adsorbent can be achieved using acid/base elution.
 
The Kwinana Seawater Reverse Osmosis Desalination (SWRO) Plant and Wind Farm in Perth, Western Australia. 3a (Upper Left) The SWRO Plant seaside location in Pert; 3b (Upper Right) The Emu Downs Wind Farm consisting of 48 Vestas wind turbines each with 1.65 MW generating capacity; 3c (Lower) The desalination plant, with 12 SWRO trains with a capacity of 160 megalitres per day and six BWRO trains delivering a final product of 144 megalitres per day. (Pankratz, 2008).  
Water cost for desalination by Renewable Energies (adapted from Bourouni et al., 2011)
LHS: Jiangxia pilot tidal plant (Photo by Zhou Xuejun). Middle: The pendulum-type wave energy conversion device in Daguan Island (100 kW, 2000, NOTC). RHS:2 kW device for surface tidal current (2009, NENU) (Wang et al., 2011)  
Article
Recent trends and challenges in applications of renewable energy technologies for water desalination are critically reviewed with an emphasis on environmental concerns and sustainable development. After providing an overview of wind, wave, geothermal, and solar renewable energy technologies for fresh water production, hybrid systems are assessed. Then scale-up and economic factors are considered. This is followed with a section on regulatory factors, environmental concerns, and globalization, and a final segment on selecting the most suitable renewable energy technology for conventional and emerging desalination processes.
 
Article
Lead contamination in China has been extensively documented by scientists in China and elsewhere over the past two decades, as summarized in this review of articles published in peer-reviewed scientific journals. Sources of that contamination include (a) deposits from previous emissions of leaded gasoline, which was finally eliminated in the past decade; (b) previous and continuing emissions from fossil fuel combustion, which are increasing markedly with the rapid industrialization of China; (c) previous and continuing emissions from other industrial activities, including mining, smelting and municipal waste incineration; and (d) previous and continuing additions of contaminated fertilizers, sewage, and untreated wastewater to agricultural fields. Lead concentrations of some Chinese agricultural produce are also elevated by acid rain and acidic fertilizers, which increase the solubility and bioavailability of both natural and contaminant lead in soil. In addition, some Chinese products are contaminated with lead during their production, processing, packaging, and transport. As a consequence of the long-range transport of industrial lead emissions from China and the global market for its products, the problem of lead pollution in China is a global problem.
 
Article
China has been one of the countries suffering from the most serious soil erosion, which has severely degraded soil productivity and water quality, thus affecting agricultural activities and hindering economic and social development. During the past few decades, a large amount of effort has been made to combat soil erosion. Vegetation restoration as a major strategy is given equal importance compared to engineering measures. Although a measure of success has been achieved, many uncertainties remain unanswered such as to what extent the vegetation restoration has reduced soil erosion and sediment loads especially in large river systems. This paper first analyzes the impacts of vegetation restoration on soil erosion and sediment loads in terms of vegetation cover and vegetation species. Then, the spatial scale effect of soil erosion reduction benefit resulting from vegetation restoration is elaborated. Soil erosion reduction benefit decreases with increased vegetation planting area. In addition, a comprehensive discussion about the disputes between vegetation restoration and engineering measures is made by integrating published studies spanning large spatial and temporal scales. Finally, future research needs regarding vegetation restoration efforts are given. In order to evaluate the effects of vegetation restoration programs on soil erosion, assessments in shorter time interval and larger spatial scale should be undertaken. Further, the present assessment system mainly based on simple statistical methods has to be improved. Specific areas demanding immediate attention, including the western China in general and the upper Yangtze River basin in particular, are highlighted as well.Supplemental materials are available for this article. Go to the publisher's online edition of Critical Reviews in Environmental Science and Technology to view the supplemental file.
 
Article
Chlorinated phenolic compounds are among the most abundant recalcitrant wastes produced by the paper and pulp industry, being accumulated in the effluents after secondary treatments. Due to their high toxicity to a wide range of organisms, chlorinated phenolic compounds pose a big concern to human and environmental health. These compounds are produced upon the partial degradation of lignin during bleaching process, and as such they are degradable by white rot fungi, the only organisms capable of degrading lignin to CO2 and H2O. White rot fungi are a group of organisms very suitable for the removal of chlorinated phenolic compounds from the environment. Indeed, they are robust, ubiquitous organisms and may survive also in the presence of high concentrations of various pollutants, even with a low bioavailability. The activity of white rot fungi is mainly due to the action of oxidoreductive enzymes, i.e., laccase, manganese peroxidase and lignin peroxidase, which are deliberately released by fungal cells into their nearby environment. In cases of secondary metabolism and oxidative stress, the fungi produce other intra- and extracellular enzymes to provide substrates for the key enzymes just mentioned. Phanerochaete chrysosporium is one of the most widely studied fungi, for which intermediary products and reactions involved in the degradation of chlorophenols have been identified. Extracellular laccases and peroxidases carry out the first productive step in the oxidation of chlorophenols, forming para-quinones and consequently releasing a chlorine atom. Further degradative steps involving several enzymes and highly reactive, nonspecific redox mediators produced by the fungus render it capable of efficiently degrading several toxic compounds. In soil environment, chlorophenols may be involved in physical-chemical processes such as polymerization and/or adsorption of/on humic substances that may hinder their degradation by microbial cells, even though both processes can result in dehalogenation of the chlorinated compounds. This review analyzes the presence of chlorophenols in the environment, their main chemical and physical properties, and the main processes in their degradation by white rot fungi with particular attention to soil environment. The reactions involved in the process, the intermediary products, the factors that may affect the fungal transformation of chlorophenols, and the possible applications for environmental purposes of both the whole fungal cells and/or their enzymes as isolated catalytic agents are also addressed.
 
Types of soil phytoremediation (adapted from Sing et al., 2002; Suresh and Ravishankar, 2004). 
Abnormal metal accumulation levels registered for the aboveground sections of some plant species growing in contaminated soils
Article
Increased soil pollution with heavy metals due to various human and natural activities has led to a growing need to address environmental contamination. Some remediation technologies have been developed to treat contaminated soil, but a biology-based technology, phytoremediation, is emerging. Phytoremediation includes phytovolatilization, phytostabilization, and phytoextraction using hyperaccumulator species or a chelate-enhancement strategy. To enhance phytoremediation as a viable strategy, microbiota from the rhizosphere can play an important role, but the use of genetic engineering can also increase the success of the technique. Here we review the key information on phytoremediation, addressing both potential and limitations, resulting from the research established on this topic.
 
Article
In view of the specific properties of mercury and its capability of forming compounds that can be bioaccumulated and biomagnified at successive levels of the trophic pyramid, it has become necessary to gather detailed information on the sources of emission of this element into the environment and its fate there. Moreover, the increasing awareness of the relationship between the toxicity of mercury and its chemical form has sharpened interest in the identification of its various forms in environmental samples. Investigating the speciation of mercury has therefore become of major importance with respect not only to determining its biogeochemical cycle but also to assessing the scale of this analytical challenge, given the need to design the appropriate analytical methodologies and reference materials that will constitute the tools for obtaining reliable analytical information.
 
Article
Tobacco smoke contains more than 4,000 chemicals, and 44 compounds have been classified as human carcinogens. Toxicity can be both mainstream smoke as well as the constituents of environmental tobacco smoke. In the light of this evidence, work is intensifying on assessing exposure on the basis of the results of tests performed to quantify the amounts of suitable environmental tobacco smoke constituent biomarkers in samples of biological materials taken from humans. The authors present information on the composition of tobacco smoke and its toxicity to humans, and also data on the methodologies applicable in the analysis of biological material samples for their biomarker content.
 
Top-cited authors
Allison A MacKay
  • The Ohio State University
Esther Oliveros
  • Paul Sabatier University - Toulouse III
Morton Barlaz
  • North Carolina State University
Yong Sik Ok
  • Korea University
Thomas H Christensen
  • Technical University of Denmark