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Mercury toxicity in plants
Abstract
Mercury poisoning has become a problem of current interest as a result of environmental pollution on a global scale. Natural
emissions of mercury form two-thirds of the input; manmade releases form about one-third. Considerable amounts of mercury
may be added to agricultural land with sludge, fertilizers, lime, and manures. The most important sources of contaminating
agricultural soil have been the use of organic mercurials as a seed-coat dressing to prevent fungal diseases in seeds. In
general, the effect of treatment on germination is favorable when recommended dosages are used. Injury to the seed increases
in direct proportion to increasing rates of application. The availability of soil mercury to plants is low, and there is a
tendency for mercury to accumulate in roots, indicating that the roots serve as a barrier to mercury uptake. Mercury concentration
in aboveground parts of plants appears to depend largely on foliar uptake of Hg0 volatilized from the soil. Uptake of mercury has been found to be plant specific in bryophytes, lichens, wetland plants,
woody plants, and crop plants. Factors affecting plant uptake include soil or sediment organic content, carbon exchange capacity,
oxide and carbonate content, redox potential, formulation used, and total metal content. In general, mercury uptake in plants
could be related to pollution level. With lower levels of mercury pollution, the amounts in crops are below the permissible
levels. Aquatic plants have shown to be bioaccumulators of mercury. Mercury concentrations in the plants (stems and leaves)
are always greater when the metal is introduced in organic form. In freshwater aquatic vascular plants, differences in uptake
rate depend on the species of plant, seasonal growthrate changes, and the metal ion being absorbed. Some of the mercury emitted
from the source into the atmosphere is absorbed by plant leaves and migrates to humus through fallen leaves. Mercury-vapor
uptake by leaves of the C3 speciesoats, barley, and wheat is five times greater than that by leaves of the C4 species corn, sorghum, and crabgrass. Such differential uptake by C3 and C4 species is largely attributable to internal resistance to mercury-vapor binding. Airborne mercury thus seems to contribute
significantly to the mercury content of crops and thereby to its intake by humans as food. Accumulation, toxicity response,
and mercury distribution differ between plants exposed through shoots or through roots, even when internal mercury concentrations
in the treated plants are similar. Throughfall and litterfall play a significant role in the cycling and deposition of mercury.
The possible causal mechanisms of mercury toxicity are changes in the permeability of the cell membrane, reactions of sulphydryl
(-SH) groups with cations, affinity for reacting with phosphate groups and active groups of ADP or ATP, and replacement of
essential ions, mainly major cations. In general, inorganic forms are thought to be more available to plants than are organic
ones.
Plants can be exposed to mercurials either by direct administration as antifungal agents, mainly to crop plants through seed
treatment or foliar spray, or by accident. The end points screened are seed germination, seedling growth, relative growth
of roots and shoots, and, in some case, studies of leaf-area index, internode development, and other anatomical characters.
Accidental exposures occur through soil, water, and air pollution. The level of toxicity is usually tested under laboratory
conditions using a wide range of concentrations and different periods of exposure. Additional parameters include biochemical
assays and genetical studies. The absorption of organic and inorganic mercury from soil by plants is low, and there is a barrier
to mercury translocation from plant roots to tops. Thus, large increases in mercury levels in soil produce only modest increases
in mercury levels in plants by direct uptake from soil. Injuries to cereal seeds caused by organic mercurials has been characterized
by abnormal germination and hypertrophy of the roots and coleoptile.
Mercury affects both light and dark reactions of photosynthesis. Substitution of the central atom of chlorophyll, magnesium,
by mercury in vivo prevents photosynthetic light harvesting in the affected chlorophyll molecules, resulting in a breakdown
of photosynthesis. The reaction varies with light intensity. A concentration and time-dependent protective effect of GSH seems
to be mediated by the restricted uptake of the metal involving cytoplasmic protein synthesis. Plant cells contain aquaporins,
proteins that facilitate the transport of water, in the vacuolar membrane (tonoplast) and the plasma membrane. Many aquaporins
are mercury sensitive, and in AQP1 a mercury-sensitive cysteine residue (Cys-189) is present adjacent to a conserved Asn-Pro-Ala
motif. At low concentrations mercury has a toxic effect on the degrading capabilities of microorganisms. Sensitivity to the
metal can be enhanced by a reduction in pH, and tolerance of mercury by microorganisms has been found to be in the order:
total population > nitrogen fixers > nitrifiers. Numerous experiments have been carried out to study the genetic effects of
mercury compounds in experimental test systems using a variety of genetic endpoints. The most noticeable and consistent effect
is the induction of c-mitosis through disturbance of the spindle activity, resulting in the formation of polyploid and aneuploid
cells and c-tumors. Organomercurials have been reported to be 200 times more potent than inorganic mercury. Exposure to inorganic
mercury reduces mitotic index in the root-tip cells and increases the frequency of chromosomal aberrations in degrees directly
proportional to the concentrations used and to the duration of exposure. The period of recovery after removal of mercury is
inversely related to the concentration and duration of exposure.
Bacterial plasmids encode resistance systems for toxic metal ions, including Hg2+, functioning by energy-dependent efflux of toxic ions through ATPases and chemiosmotic cationproton antiporters. The inducible
mercury resistance (mer) operon encodes both a mercuric ion uptake and detoxification enzymes. In gram-negative bacteria a periplasmic protein,MerP, an inner-membrane transport protein,MerT, and a cytoplasmic enzyme, mercuric reductase, theMerA protein, are responsible for the transport of mercuric ions into cells and their reduction to elemental mercury, Hg(II).
InThiobacillus ferrooxidans, an acidophilic chemoautotrophic bacterium sensitive to mercury ions, a group of mercury-resistant strains, which volatilize
mercury, has been isolated. The entire coding sequence of the mercury-ion resistance gene has been located in a 2.3 kb fragment
of chromosomal DNA (encoding 56,000 and 16,000 molecular-weight proteins) from strain E-l 5 ofEscherichia coli. Higher plants andSchizosaccharomyces pombe respond to heavy-metal stress of mercury by synthesizing phytochelatins (PCs) that act as chelators. The strength of Hg(II)
binding to glutathione and phytochelatins follows the order: γGlu-Cys-Gly(γGlu-Cys)2Gly(γGlu-Cys)3Gly(γGlu-Cys)4Gly. Suspension cultures of haploid tobacco,Nicotiana tabacum, cells were subjected to ethyl methane sulfonate to raise mercury-tolerant plantlets. HgCl2-tolerant variants were selected from nitrosoguanidine (NTG)-treated suspension cell cultures of cow pea,Vigna unguiculata, initiated from hypocotyl callus and incubated with 18 ⧎g/ml HgCl2. Experiments have been carried out to develop mercury-tolerant plants ofHordeum vulgare through previous exposure to low doses of mercury and subsequent planting of the next generation in mercury-contaminated
soil. Phytoremediation involves the use of plants to extract, detoxify, and/or sequester environmental pollutants from soil
and water. Transgenic plants cleave mercury ions from methylmercury complexes, reduce mercury ions to the metallic form, take
up metallic mercury through their roots, and evolve less toxic elemental mercury. Genetically engineered plants contain modified
forms of bacterial genes that break down methyl mercury and reduce mercury ions. The first gene successfully inserted into
plants wasmerA, which codes for a mercuric ion reductase enzyme, reducing ionic mercury to the less toxic elemental form.MerB codes for an organomercurial lyase protein that cleaves mercury ions from highly toxic methyl mercury compounds. Plants with
themerB gene have been shown to detoxify methyl mercury in soil and water. Both genes have been successfully expressed inArabidopsis thaliana, Brassica (mustard),Nicotiana tabacum (tobacco), andLiriodendron tulipifera (tulip poplar). Plants currently being transformed include cattails, wild rice, andSpartina, another wetland plant. The problem of mercury contamination can be reduced appreciably by combining the standard methods
of phytoremediation—removal of mercury from polluted areas through scavenger plants—with raising such plants both by routine
mutagenesis and by genetic engineering. The different transgenics raised utilizing the two genesmerA andmerB are very hopeful prospects.
... Various industries yield huge amounts of Hg which are released in the soil or water as industrial wastes (Tutic et al. 2015). Acceptable amounts of Hg in calcareous and acid soil are 17 ppm and 6 ppm respectively (Patra and Sharma 2000). Hg is known to disrupt cell membranes, modify the activities of various enzymes thereby diminishing growth and Responsible Editor: Gangrong Shi metabolism (heavy metals on agroecosystems and impact on health). ...
... Various factors control the absorption of metals by plants, such as the movement of metal from the bulk to root surface (which in turn depends of the soil/media property), the movement from root surface to root (depends on sequestering of the metal ions by various molecules present on the root surface) and the translocation from root to shoot (Patra and Sharma 2000). Remediation of heavy metal contamination in agroecosystems should be based on using an agent that can modulate any of the abovementioned factors thereby lowering the uptake, accumulation and magnification of these hazardous contaminants. ...
... ROSs are also two-faced moieties which at higher concentration exert harmful effects while at lower concentration act as regulators of various metabolic processes (Mitra et al. 2022). Heavy metals are also known to cause membrane damage (Patra and Sharma 2000). Due to accumulation of ROS, membranes suffer severe oxidative damage. ...
The last few decades have witnessed a dramatic progress of human civilization via industrialization, which, in turn, is associated with a surge in pollution of the environment. Heavy metals being one of the most hazardous pollutants have posed a serious threat to life sustaining ecosystem. Among the various remediation techniques, presently, the use of nanoparticles as adsorbents and chelator of heavy metal ions has emerged being practical and cost effective. Mesoporous silica nanoparticles, due to its unique structural attributes, have found application in adsorption of heavy metals in solutions. This study encompasses elucidation of the role of mesoporous silica nanoparticles MCM 41 and MCM 48 in mitigating stress caused by toxic dose of heavy metal Hg²⁺ (25 ppm) on growing seedlings of Vigna radiata and probiotic soil bacteria Bacillus coagulans. The results revealed that application of the nanoparticles at specific concentration can stimulate an increase in growth of plantlets, decrease in the yield reactive oxygen species like superoxide anion and hydrogen peroxide, reduction of lipid peroxidation, increase in antioxidant enzyme activity in Vigna radiata, and enhancement of growth of Bacillus coagulans as compared to that of Hg²⁺ alone. Moreover, it was found that MCM 41 was effective at higher dosages compared to MCM 48, which indicates the structure to function relationship.
Graphical abstract
... The soil-root transfer of Hg results from its speciation, and the plant growth medium primarily governs Hg bioaccumulation (Hussain et al., 2022;Natasha et al., 2020). Previous reports revealed that Hg uptake by plants is likely to be attributed to the level of soil pollution; i.e., with low levels of Hg pollution, the contents of Hg in plants are more likely to be in the same range as that in the soils and below the permissible levels (Patra & Sharma, 2000). However, many reports also claimed that Hg in the foliar is accumulated through absorption, enhanced by dry deposition via stomata (Chen & Yang, 2012;Kabata Pendias, 2011;Lindberg et al., 1979;Naharro et al., 2020;Natasha et al., 2020;Rea et al., 2001). ...
... Zayed et al. (1998) previously also acknowledged that Cr is very unlikely to be transported upward in higher vascular plants. According to Patra and Sharma (2000), the roots of tobacco play a role as a barrier to Cr translocation across the above-ground tissues. Ertani et al. (2017) argued that most plants' vacuoles in root cells form a protective mechanism to block Cr migration in above-ground tissues. ...
... Nevertheless, the earlier reports had highlighted that tobacco is sensitive to Cr bioavailability, so its concentration in soil results in subsequent foliar uptake (Parr et al., 1976;Soane & Saunders, 1959). Many previous studies accentuated the inability of plants to accumulate and translocate Hg from roots upward in plants and agreed on the likelihood of most plants to be Hg excluders (Ahammad et al., 2018;Beauford et al., 1977;Fernández-Martínez et al., 2015;Kabata Pendias, 2011;Patra & Sharma, 2000;Sierra et al., 2008). However, Bontidean et al. (2004) argued that when Hg in plant leaves is detected in lower levels because of poorly translocation, it will restrict the use of such species as biological indicators of Hg contaminated soils. ...
The present study investigated the bioaccumulation and translocation of mercury (Hg) and chromium (Cr) in Yunyan 87 flue-cured tobacco (Nicotiana tabacum) and assessed the influence of soil pH on the metal uptake by plant organs at the field scale. The study was conducted in 4 different regions selected from Sichuan Province, China: Guangyuan, Luzhou, Panzhihua, and Yibin. The results revealed that Hg highly contaminated Yibin soils at 0.29 mg kg−1 and by Cr at 147 mg kg-1, which is above the permissible limit. The levels of Hg in tobacco plant organs were predominantly in the order of leaves > root > stem. The overall trend for Cr contents in tobacco organs was in the order of root > leaves > stem. The results of an index of bioaccumulation (IBA) and translocation factor (TF) showed that the values observed in Panzhihua and Guangyuan tobacco leaves were generally higher, despite the low levels of soil contamination. The linear mixed model (LMM) demonstrated that the log of Hg IBA in tobacco organs was likely to decrease with soil pH increase, whereas the log of Cr IBA only decreased in the root but gradually increased in the aerial parts with soil pH increase. The total random variation in the log of metals’ IBA due to regions indicated that for Hg, 33.42% of the variation was explained by regional differences, while for Cr, only 13% was accounted. The results suggested that Yibin and Luzhou need to correct the soil acidity if they are set to reduce Hg contamination in tobacco-growing soils. Guangyuan and Panzhihua need efforts to keep the soil pH on track to avoid high contamination levels, and effective measures of soil nutrients supply are required to produce high tobacco leaf quality free from heavy metal content. The findings of this study may be used to ascertain regional differences in heavy metals, particularly Hg and Cr uptake by tobacco plant organs, and to prevent the cultivation areas contamination through soil pH monitoring.
... Worst of it, during gold extraction from the wetland in Bitsya Subcounty, mercury is normally used to separate gold from sand (NSOER, 2019). According to Patra and Sharma, (2000), organic mercurial was noted to; cause abnormal germination and hypertrophy of the roots and coleoptile in cereals, affect both light and dark stages of photosynthesis by substituting the central atom of chlorophyll (Magnesium) with mercury atom in vivo thus stopping photosynthetic light harvesting in the affected chlorophyll molecules. This triggers the breakdown of photosynthesis, leading to reduced productivity and death of plants, and therefore reduction in the health status of the wetland ecosystem function. ...
... harmfully degrade the capabilities of the soil microorganisms (Patra and Sharma, 2000). ...
... Mercury in Uganda most especially in the study area was used to separate gold that was normally extracted along with sand (NSOER, 2019). Therefore, the low NDVI values in the sites (middle) where artisanal gold mining was mostly done, confirms the negative effects of mercury on wetland vegetation as addressed by Patra and Sharma, (2000); Edmonds et al., (2010); Lázaro et al., 2018). ...
Wetland degradation due to anthropogenic activities including artisanal gold mining is widely common in Uganda, and this affects vegetation health status if not controlled. However, the use of the Normalised Difference Vegetation Index (NDVI) to determine the health status of wetlands is rare. In this study, remote sensing techniques with the use of spatial-temporal Normalised Difference Vegetation Index (NDVI) were used for the wetlands in Bitsya Subcounty, Buhweju district (noted for artisanal gold mining with the use of mercury) to determine the wetland health status for the period between 2012-2021. This was for the purposes of identifying target areas for intervention and developing appropriate, location-specific intervention options. 7 images of 30 * 30 m and 3 images of 10 * 10 m respectively, ortho-rectified, cloud-free Landsat and Sentinel images obtained from the USGS archive were analysed. The results showed that the high NDVI value (0.775) was detected in the year 2019 and the low NDVI value (0.068) was detected in the year 2017. The NDVI maps showed low values mostly in the middle of the wetland where artisanal gold mining was mostly taking place, indicating a huge decline in the wetland health status as compared to other wetland edges noticed with high NDVI. The results from the study suggest that the wetland policies in the study area could not be effectively implemented and this reduces the vegetation health status, threatening the functionality of the wetland and as well as loss of the free natural goods and services derived from them. This necessitates the development of wetland restoration campaigns. However, failure to implement the wetland policies may have an ecosystem impact on the wetland micro and macro-organisms, soil nutrients, and water quality as well as a decline in vegetation health
... Plants uptake mercury in the forms of elemental mercury (Hg 0 ), Hg (II) and organic methylmercury (MeHg) and terrestrial plant species have less MeHg in their body compared to the aquatic plant species (Li et al. 2017). The mercury uptake in the plants occurs from the soil, sediment, water, and the atmosphere (Patra and Sharma 2000). Xylem sap in plants plays a vital role in mobilizing total mercury and methylmercury inside the plant tissue (Bishop et al. 1998). ...
... The excessive production of reactive oxygen species (ROS) has been considered one of Hg's significant plant exposure outcomes; the effect is discussed in Section 4.7. The application of Hg-contained fungicide also has influenced plants, like abnormal germination and hypertrophy of the roots and S-H (sulfhydryl) systems of the embryo (Patra and Sharma 2000). ...
... barrier of Hg translocation from root to shoot and leaf. However, the leaf part acts as a site for Hg loss to the environment (Nyman and Lindau 2016;Patra and Sharma 2000;Raj et al. 2020). Among different plant organs, roots are severely affected due to the higher concentration of Hg 2+ in soil solution. ...
The presence of high levels of Hg (mercury) in the soil has been considered one of the major global environmental problems. Hg contamination mainly occurs through a number of anthropogenic activities, and mining plays a vital role in them. Hg presents in the soil medium as either bounded with minerals or as an adsorbent in soil solution, and their forms also regulate their toxicity in the organisms. Plants show a number of responses, including morphological, anatomical, photosynthetic, enzymatic and cellular levels when exposed to Hg. A number of physiological changes occurred in the plant body, including redox balance, ROS (reactive oxygen species) production, chelation, antioxidative tolerance, and miRNA-mediated tolerance to cope with Hg toxicity. The phytoremediation of Hg has not been successful due to a lack of finding Hg hyperaccumulator plant species. Hg contamination in Asia has received attention as a high level of methyl mercury uptake in the rice, and it has become the prenominal pathway for Hg exposure in the local populations. The Hg uptake in the plants demands further research as long-term consumption below than threshold level of methylmercury could be harmful to the human central nervous system.
... Metal anomalies across the PTB have been extensively documented (e.g., Grasby et al., 2015;Rampino et al., 2017;Chu et al., 2021;Liu et al., 2023). Moreover, exposure of extant plants to elevated concentrations of Co, Hg, and Ni has been shown to induce various cytological defects at both the micro-and macromorphological scales (Mishra and Kar, 1974;Léonard and Lauders, 1990;Beyersmann and Hartwig, 1992;De Flora et al., 1994;Patra and Sharma, 2000). Crucially, multiple studies have noted an apparent synchroneity between the occurrence of aberrant palynomorphs and elevated Hg concentrations during various biotic crises (e.g., Lindström et al., 2019;Chu et al., 2021;Shu et al., 2023;Bos et al., 2024), which underscores the potential role of heavy metal-induced mutagenesis in driving ecological disruptions during these critical periods. ...
... These modern malformations are linked to incomplete separation of pollen mother cells during meiosis, resulting in polyploidy (Ickert-Bond et al., 2003). Since heavy metal exposure is known to induce both polyploidy and the abnormal thickening of pollen walls (Sheoran and Singh, 1993;Patra and Sharma, 2000), we believe that the distinct morphology of E. permasensis may be an expression of cytogenetic defects caused by metal toxicity. While introgressive hybridisation can also cause the production of abnormal pollen, as in extant examples (Ickert- Bond et al., 2003), we believe that this is unlikely to be the cause of the distinct morphology of E. per-masensis, since such morphotypes would be prevalent throughout Permian and Triassic deposits wherever Ephedripites spp. ...
The end-Permian extinction (EPE) (∼251.9 Ma) is considered the most severe biotic crisis in Earth’s history. Rapid climatic change and oceanic acidification triggered by Siberian Traps volcanism culminated in a widely documented mass extinction in the marine realm, but the event’s impact on terrestrial ecosystems, particularly plant communities, is less well understood. While the existence of a floral mass extinction at the Permian-Triassic Boundary (PTB) is still debated, there is mounting evidence for pervasive mutagenesis among various plant lineages, as expressed by the high incidence of aberrant spores and pollen grains. Previous studies have proposed a causal relationship between increased UV-B flux and plant mutagenesis across the PTB, yet the role of volcanically derived heavy metals as a contributing factor has received considerably less attention. Here we present the results of a high-resolution palynological, sedimentological, and geochemical analysis of a continuous and previously unstudied PTB section from the Norwegian Arctic. The study reveals an abrupt increase in the levels of heavy metals across the EPE negative carbon isotope excursion (CIE). Palynological analysis indicates disruption, and a phased transition of plant communities at the PTB, without a significant turnover in species or decrease in diversity. However, the abrupt appearance and elevated abundance of aberrant palynomorphs coincides with increased concentrations of As, Co, Hg, and Ni, which is interpreted as compelling evidence for heavy metal-induced stress and genetic disturbance in plant communities during the EPE. We hypothesise that biomagnification of these elements may have been a significant driver for the end-Permian biotic crisis. Our findings are correlated via biostratigraphy and chemostratigraphy with other circum-Arctic PTB sections described in the literature, demonstrating the isochroneity and facies independence of these widespread palaeoecological changes.
... Though reports related to the mechanism of accumulation of mercury in plants and their tissue distribution are scanty, literature pertaining to the effect of mercury on the plant systems are plentily available in comparison to animal systems. Some of the possible mechanisms through which mercury can impair important biochemical and physiological processes in living organisms include inhibition of germination (27), a decrease of biomass production (28), inhibition of photosynthesis (27), hindrance of protein function and induction of oxidative stress (29) anddamaging effect on DNA (30). ...
... Though reports related to the mechanism of accumulation of mercury in plants and their tissue distribution are scanty, literature pertaining to the effect of mercury on the plant systems are plentily available in comparison to animal systems. Some of the possible mechanisms through which mercury can impair important biochemical and physiological processes in living organisms include inhibition of germination (27), a decrease of biomass production (28), inhibition of photosynthesis (27), hindrance of protein function and induction of oxidative stress (29) anddamaging effect on DNA (30). ...
Heavy metals are toxic metals which are persistent in nature due to their nondegradable nature.Due to increase in industrialization and urbanization heavy metals are being added to theenvironment and consequently causing heavy metal pollution of water and soil. These heavy metals cause significant stress on crop plants and effect various parameters such as growth and yield. Manymethods like physical, chemical and biological methods are available to degrade these heavymetals. Recently, bioremediation is being widely used because of its cost-effective andenvironment friendly approach. Bioremediation is a biological process which makes use ofmicroorganisms to remove hazardous substances or environmental pollutants from air, water,soil, industrial effluents etc. Bacteria and fungi are mostly employed for bioremediation.These organisms are genetically engineered for effective use in bioremediation. This not onlydiscussed about the importance of bacteria for bioremediation of heavy metals but alsodiscussed about the challenges and limitations of bacteria for bioremediation. In this chapter, a variety of mechanisms responsible for adaptation of microorganisms to high heavy metal concentrations, e.g. metal sorption, uptake and accumulation, extracellular precipitation and enzymatic oxidation or reduction, will be reported. Moreover, molecular mechanisms responsible for their metal tolerance will be described.
... The main pathway of Hg into the above-ground parts of plants is aerial uptake of either gaseous Hg(0) or particle-bound organic Hg, while almost all Hg absorbed directly from the soil remains in the roots. 46,52 Over 90% of Hg transported from the roots to the leaves and stem is released into the atmosphere through leaf stomata, 50,53 compounding the notion that Hg concentrations in plant leaves and stems should be more closely related to gaseous Hg than soil Hg. Therefore, one would expect fescue Hg concentrations at ancient mining sites to have been more similar to those at reference sites than those at contemporary mining sites, because ancient mining sites have lacked gaseous Hg(0) emissions for centuries. ...
... 54,55 Another possible pathway is the direct absorption of particle-bound mercury transported from the earth's surface to the atmosphere through grass stomata. 52 The mechanisms that may explain the unexpected similarities in fescue Hg concentrations between ancient and contemporary mining sites require further investigation. If soil-bound Hg has indeed been able to volatilize at a substantial rate for 700 years after the cessation of ancient mining activities in the Fergana Valley, then environmental risk assessments should be conducted to determine the suitability of the land for residential, industrial, and agricultural development at these sites. ...
The toxic metal mercury (Hg) has been mined, processed, and used throughout the Fergana Valley region of post-Soviet Central Asia for millennia. Although most historical Hg mining activities have ceased throughout the Fergana Valley region, today Hg is still mined, processed, and exported globally from the Khaidarkan kombinat in southwestern Kyrgyzstan. Despite the rich history of Hg mining and use throughout the Fergana Valley region, the legacy effects of these activities on environmental Hg contamination remain undescribed. Mercury concentrations were analyzed in topsoil, terrestrial vegetation, earthworms, riverine sediments, and fishes collected from sites with varied histories of Hg mining within the Fergana Valley region. Environmental and biological Hg concentrations were greatest at contemporary mining sites where Hg has been mined after 1940, intermediate at ancient mining sites where all historical Hg mining activities ceased before 1300 AD, and lowest at reference sites without known Hg mining history. For all environmental media and biota, Hg concentrations were 1-2 orders of magnitude greater at contemporary mining sites than at reference sites. Elevated Hg concentrations at contemporary mining sites are attributed to the recency and intensity of Hg mining and showcase the detrimental effects of Hg mining to diverse environmental media and biota. Elevated Hg concentrations at ancient mining sites are attributed to a combination of 1) legacy Hg contamination in soils and sediments introduced by historical mining and processing activities over 700 years ago and 2) the presence of naturally Hg-rich geologic belts upon which ancient mines were constructed.
... Research on the reaction of terrestrial plants to soil contaminated with mercury has been carried out in the last few decades. These studies have demonstrated that, on average, plants are less able to absorb mercury through their roots than through parts of their bodies that are above ground (Fernández-Martínez et al., 2015;Patra and Sharma, 2000). When attached to fulvic acid, inorganic mercury forms are usually easier for roots to absorb from the soil (Hongtao et al., 2004;Meng et al., 2012). ...
... Most cited papers on the phytoremediation of mercury pollution in WoS [69][70][71][132][133][134][135][136][137][138][139][140][141][142][143][144][145][146][147]; Table S5. Most cited papers on the phytoremediation of mercury pollution in Scopus [3,14,22,[69][70][71][72][73][74][148][149][150][151][152][153][154][155][156][157][158]; Table S6. Top 31 keywords with the strongest citation bursts in WoS; Table S7. ...
Mercury is classified as one of the world’s most toxic and dangerous pollutants as it tends to bioaccumulate and biomagnify within the trophic chain and is persistent. Various approaches are available to remediate Hg-affected sites including phytoremediation, which includes the use of plants to clean up contaminated environments. The phytoremediation of mercury contamination is attracting increasing attention because of its advantages: it is environmentally friendly, inexpensive, simple, and can improve soil fertility. In this report, VOSviewer (version 1.6.1) and Bibliometrix (version 4.16) software were used to analyze 457 and 697 documents published from 2000 to 2023, retrieved from the databases WoS and Scopus, respectively. China, India, the United States, and Spain were the top four most productive countries. The largest topic area was environmental sciences, and the Chinese Academy of Sciences was the organization that contributed the most to the overall number of publications. The keywords with the highest frequency excluding phytoremediation and mercury in WoS were heavy metals, accumulation, cadmium, soils, and phytoextraction. In Scopus, the most frequent keywords were bioremediation, heavy metals, soil pollution, bioaccumulation, biodegradation, and environmental. From the above analysis, we concluded that future research should focus on (1) finding native plants, (2) genetic engineering applications, (3) increasing remediation ability through assisted phytoremediation, and (4) the detoxification mechanism of mercury. This study provides insights into trending themes and serves as a reference for future research.
... Mercury contamination in the environment comes from both natural and anthropogenic sources. Agricultural sources include fertilizers, pesticides, and fungicides (Patra and Sharma, 2000), which have been extensively used to control diseases affecting economically important food crops. Mercury has low bioavailability in soils but excessive amounts combined with a low soil pH and high cation exchange capacity can promote increased plant uptake. ...
Chromolaena odorata (L.f.) R.M. King et H. Robinson plants were grown in Hoagland’s solutions with 0.00 ppm and 1.00 ppm Hg(NO3)2. The calcium, magnesium, iron, and sulfur levels in the leaves were found to be not significantly affected by presence of the uptaken Hg2+. The chlorophyll a, chlorophyll b, and total chlorophyll contents of its leaves also remained within normal levels, which may indicate that the photosynthetic machinery of the Hg-exposed C. odorata was unaffected by the presence of Hg2+. The results of the ICP-AES analyses of the Hg2+ contents established the presence of Hg2+ in all the subcellular components obtained from the leaves of the Hg-treated C. odorata plants, and that the ultimate localization of Hg2+ is in the vacuoles. The findings revealed no significant differences in the degree of oxidative injury between the cells from the control and Hg-treated plants, as evidenced by the low lipid peroxidation levels obtained with the TBARS assay. The SH-containing biomolecules that were initially detected through DTNB assay manifested a predominant peak in the RP-HPLC chromatographs of both the control and Hg-treated plants, with their retention times falling within the ranges of GSH, MT, and cysteine standards. However, the concentrations of the GSH- and/or MT-like, Cys-containing biomolecules detected in the leaves of Hg-treated C. odorata plants were ten times higher than those of the control.The findings of this study suggest that the enhanced antioxidative capacity, the production of Hg-binding biomolecules, and the localization of Hg2+ ions ultimately in the vacuoles of the leaves are the mechanisms which bring about Hg2+ tolerance and homeostasis in C. odorata plant. These results indicate that C. odorata is a potentially effective phytoremediator for Hg2+.
... Plants take up Hg easily from solution cultures. Soil Hg however is not only directly absorbed by plants, but also indirectly absorbed from Hg vapor gradually released in soils (Manomita & Sudhir, 2022). ...
This study assessed the physicochemical and heavy metal properties of soil and the risks associated with Zea mays contamination by heavy metals in farmed dump sites in Tubah Sub-division, Northwest Cameroon. Three surface soil samples (0-20 cm) and Zea mays plant samples were collected from Bambili (S1), Baforkum (S2) and Bambui (S3) and analyzed following standard analytical procedures. Results of physicochemical analysis showed that all the soils had low pH values (5.45-6.12), moderate organic matter content (3.93% - 7.14%), and high available phosphorus (9.51-52.58 mg/kg). Total heavy metal concentrations for all soil samples ranged from 4.66-5.23 mg/kg, 65.32-98.12 mg/kg, 1555.12-2158.65 mg/kg, 94.64-115.34mg/kg, 0.87-1.01 mg/kg, 96.54-156.3 mg/kg, and 289.43-450.48 mg/kg for Cd, Pb, Mn, Cu, Hg, Cr and Zn respectively. Total heavy metal concentrations in Zea mays plant ranged from 2.66-4.33 mg/kg, 21.32-28.21 mg/kg, 55.12-230.34 mg/kg, 8.64-34.23 mg/kg, 0.47-0.81 mg/kg, 53.43-76.3 mg/kg, and 89.43-108.48 mg/kg for Cd, Pb, Mn, Cu, Hg, Cr and Zn respectively. This study thus revealed that the soils and Zea mays plants were contaminated to varying degrees by the heavy metals Cd, Mn, Cu, Hg, Cr and Zn, and consequently, there are potential health hazards associated with the consumption of Zea mays cultivated on these soils. Physical remediation (capping, washing of soil, excavation of soil), chemical remediation (immobilization, solidification, vitrification), and phytoremediation can be employed to recover heavy metals from such soils, meanwhile, lime-induced immobilization of heavy metals could assist to keep the metals in the soil in an insoluble state.
... Hg has no biological roles in the plants. Hg toxicity in plants changes the permeability of cells membrane, reacts with sulphydryl groups and shows affinity for reacting with phosphate groups (Patra & Sharma, 2000). It is also known to impact antioxidant defence system (Israr et al., 2006;Sparks, 2005). ...
Heavy metal pollution is one of the modern environmental problems that contaminate soil, water, and air. Heavy metal pollution not only results in significant crop yield losses, but also poses health risks. When subjected to heavy metal toxicity, which happens when the quantity of particular heavy metals in the soil or water exceeds their tolerance levels, plants can exhibit a variety of reactions. Metal accumulation in the tissues of plants causes oxidative stress. The oxidative stress in turn impacts cellular homeostasis and adversely affects growth and development. Plants exhibit different mechanisms to fight stressful conditions and lessen the negative consequences of heavy metal toxicity. In this regard, the first line of defence in response to heavy metal toxicity provided by the plant is restricting the uptake of the metals. The second line of defence includes various detoxification mechanisms. Microbes especially associated with the rhizospheric region of the crops have role in remediation of the soils from metal contaminants. The present review highlights the impact of heavy metal on plants and role of the microbes in lessening of heavy metal stress in plants.
... According to the characteristics of Hg, because of the bio-concentration, bio-accumulation, and biomagnification properties, such amounts in the ecosystem will increase to much higher levels; considerable increases in soil Hg levels result in relatively small increases in plant Hg levels by direct absorption from soil. Despite plants absorbing little organic and inorganic Hg from the soil, and there is a barrier to Hg transfer from plant roots to crowns (Patra & Sharma, 2000). ...
Background: Mercury (Hg), in particular methyl-mercury (Methyl-Hg), is a potentially dangerous heavy metal with special physicochemical features including environmentally persistent, bio-accumulative, bio-concentrated, and bio-magnification. Thus, it has the potential to be high risk to both human and environmental health. However, there are few studies quantifying mercury toxicity in all environmental components, especially in developing countries. Therefore , the aim of this systematic review and meta-analysis was to determine the amount of mercury present in various environmental components. Methods: Preferred Reporting Items for Systematic Reviews (PRISMA) updated criteria were used for the flow diagram. PubMed, Medline, Web of Science, Embase, previous reviews, reports, and other methods were searched as databases. A thorough search was conducted for all studies published 2000-2023 using keywords and MeSH terms with Boolean logic operators (AND, OR). The titles and abstracts returned by the search were screened. Data were extracted using a prescribed Microsoft Excel. The mean concentration of Hg in soil, blood, fish and dust, and plant leaf was estimated using STATA version 17. The random effect model with a 95% confidence interval was used at a p-value of less than 0.05. Results: A total of 208 records were searched from PubMed (n=33), Medline (n=39), Web of Science (n=37), Embase (n=23), previous reviews (n=18), reports (n=5) and via other methods (n=53). This review revealed that different concentrations of Mercury (Hg) are found in various components of the environment. This review found the mean mercury concentration in fish was 1.60 µg (95% CI:-0.02, 3.22 µg), soil 0.32mg/kg (95%CI:-1.25, 1.90mg/km) , dust 0.47 mg/kg (95% CI:-1.10, 2.04mg/km) and water bodies 0.55 µg/dm3 (95% CI:-1.04, 2.13), plant 28.96 mg/kg (95% CI:-22.57, 80.49 mg/kg), and human blood at 0.92 µg/L (95% CI:-0.72 µg/L, 2.57). Conclusions: This systematic review and meta-analysis concluded that the methyl-mercury form is the most prevalent in both biotic and abiotic as compared to other forms of mercury. Nevertheless, limited research has been found in low-and middle-income nations, where the majority of raw mercury is produced. Moreover, the review suggested that international cooperation, national policies, and regulations on mercury management are crucial for minimizing the harmful effects of both biotic and abiotic mercury components.
... Outros danos ocasionados no metabolismo das plantas podem ser por meio da alteração da estrutura e a funcionalidade das células de algumas organelas, bem como a disfunção do processo fotossintético e na transpiração (Krupa;Baszynski, 1995), redução da absorção de água e nutrientes minerais (Cho;Park, 2000;Patra;Sharma, 2000), inibição da síntese de clorofila (Godbold;Hüttermann, 1986;Cargnelutti et al., 2006) e aumento da peroxidação lipídica (Cho;Park, 2000). ...
O mercúrio é um metal pesado reconhecido por seus riscos significativos à saúde humana e ao meio ambiente, especialmente quando se transforma em metilmercúrio, uma forma altamente tóxica, capaz de causar danos neurológicos, cardiovasculares e reprodutivos em animais e humanos, tornando essencial o monitoramento das concentrações desse metal, especialmente em pisciculturas, considerando seus impactos adversos na contaminação de peixes e consequentemente à saúde humana ao consumi-los. Portanto, o objetivo deste artigo foi avaliar a concentração de mercúrio em 12 pisciculturas no Estado de Mato Grosso, Brasil. Para isso, foram coletadas amostras de sedimentos, solos e vegetação dos tanques de criação de peixes e nas áreas adjacentes (aproximadamente 15 metros dos tanques). Além disso, tecidos de músculo, cérebro, fígado e nadadeiras do peixe híbrido tambatinga foram coletadas. Todas as amostras foram analisadas seguindo o método US EPA 7473, para as matrizes e utilizando o aparelho DMA-80. De acordo com os resultados, as análises revelaram que as concentrações de mercúrio estavam abaixo dos limites estabelecidos pela legislação brasileira, sugerindo conformidade com os padrões regulatórios. Entretanto, é importante salientar a ausência de determinação pela Resolução do Conselho Nacional do Meio Ambiente (CONAMA) sobre os limites aceitáveis de mercúrio na vegetação de áreas rurais, o que configura uma lacuna normativa que demanda atenção. Assim como é crucial enfatizar a persistente toxicidade do mercúrio e a necessidade de monitoramento contínuo, devido ao seu potencial impacto na saúde humana e ambiental a longo prazo. Portanto, a vigilância constante é fundamental para garantir a segurança alimentar e a preservação dos ecossistemas aquáticos.
... As shown in Figure 8, mercury concentration levels in sediments and water bodies began to decrease gradually with the increase of mercury content in plants at the beginning of spring growth. This phenomenon can be attributed to the biosorption of Hg by the plants and the uptake and transport mechanism of Hg by the root system (Patra and Sharma, 2000). The enrichment of Hg within the plant gradually increased with further growth of the plant. ...
Mercury (Hg), as a global pollutant, is persistent, migratory, insidious, highly biotoxic and highly enriched, and is widely distributed in the atmosphere, hydrosphere, biosphere and lithosphere. Wetland ecosystems, as active mercury reservoirs, have become the most important sources and sinks of heavy metal mercury. Distinguished from natural wetlands, artificial wetlands located in urban sections of rivers face problems such as diverse urban pollution sources and complex spatial and temporal changes. Therefore, in this study, five intermittently distributed artificial wetlands were selected from the upstream to the downstream of the Changchun section of the Yitong River, a tributary of the Songhua River basin in the old industrial base of Northeast China. The mercury levels in the water bodies, sediments and plants of the artificial wetlands were collected and tested in four quarters from April 2023 to analyse the spatial and temporal distribution characteristics of total mercury. The results showed that the mercury levels in the water bodies, sediments and plants of the five wetlands showed a fluctuating trend with the river flow direction and had certain spatial and temporal distribution characteristics. This phenomenon was attributed to the sinking of external mercury pollution sources. In general, the wetland ecosystems showed a decreasing trend in the total Hg output of the downstream watershed. This may be due to the retention of particulate matter by aquatic plants in artificial wetlands to regular salvage of dead aquatic plants. At the same time urbanization and industrialization affect mercury levels in aquatic environments, so the risk of residential exposure needs to be looked at.
... Natural emissions of mercury form two-thirds of the input; manmade releases form about one-third. Significant amounts of mercury may be added to agricultural land with sludge, fertilizers, lime, fungicides, and manures [17,18] . ...
... Concentraciones mayores a 5 mg/kg de Hg son muy tóxicas para la mayoría de las plantas (Kabata-Pendias y Pendias 2010). La toxicidad, acumulación y distribución del Hg en los distintos órganos vegetales puede variar entre especies de plantas expuestas a concentraciones similares del metal (Patra y Sharma 2000). Las plantas tolerantes e hiperacumuladoras son las únicas que pueden almacenar altas concentraciones de metales en raíces y vástagos sin presentar signos de toxicidad (Kramer 2010), pero los umbrales para el Hg aún no se encuentran claramente establecidos (Liu et al. 2020). ...
Mercury (Hg) is the most harmful heavy metal for living beings due to its high toxicity, persistence, and bioaugmentation in the food web. Lantana camara has been considered promising for the phytoremediation of different metals, but its response to Hg has not been characterized. The objective of this study was to evaluate the effectiveness of L. camara to bioaccumulate, translocate, and volatilize Hg in artificially contaminated soils (1.0 and 8.0 mg/kg Hg). After two months of treatment, the dry weight was measured and the Hg present in stems, roots, leaves, and atmosphere was quantified using atomic absorption spectroscopy. The volatilized Hg was captured in hermetic chambers with continuous airflow, connected to a trap solution (5 % KMnO4 dissolved in H2SO4). The translocation factor was < 1, and the bioaccumulation factor was > 1 in both treatments. The Hgº values volatilized in high mercury indicate that approximately 7.1 µg/g plant/day can be released into the atmosphere. Our results indicate that L. camara accumulates Hg mainly in the root, showing potential for phytostabilization, but the observed volatilization rates point towards a more restricted use of this species in phytoremediation strategies.
... It is an odourless white crystalline solid, used as laboratory reagent. It is a highly toxic compound that volatizes slightly at room temperature and appreciably at 150°C (Patra &Sharma, 2000). Mercuric chloride is highly toxic, both acutely and as a cumulative poison. ...
Drug-induced injury is a key cause of kidney disease. Mercuric chloride, an antineoplastic agent used for treating various malignancies can cause kidney injury and induce nephrotoxicity. This study was to determine the effects of Newbouldia laevis on mercury chloride-induced kidney damage in adult male Wistar rats. Twenty-five adult male Wistar rats weighing between 110-200g were used for this study. The animals were divided into five groups: A to E with five rats per group. Group A served as the control group and was administered 1ml of distilled water daily. Group B received a low dose of Newbouldia laevis (200mg/kg body weight) for 28 days along with Mercuric chloride (10mg/kg body weight). Group C received an intermediate dose of Newbouldia laevis (400mg/kg) for 28 days with Mercuric chloride (10mg/kg). Group D received a high dose of Newbouldia laevis (800mg/kg) for 28 days with Mercuric chloride (10mg/kg). Group E received only Mercuric chloride (10mg/kg) daily for 28 days. Rats in each group were allowed unrestricted access to water and feed during the experiment. Intracardial collection of blood from the Wistar rats was carried out in each group and the kidney function were assessed. The kidney tissues were processed for light microscopy study. Group A kidney tissues showed normal tubules, glomeruli, and interstitial spaces. Group E showed mercuric chloride-induced kidney injury: perivascular infiltrates of inflammatory cells; patchy tubular necrosis. Group D showed amelioration of the damages caused by Mercuric chloride. It can be concluded that Newbouldia laevis ameliorated Mercuric chloride-induced kidney damage in dose-dependent-pattern.
... Hg +2 affects both light and dark reactions of photosynthesis. Mg is replaced by Hg 2+ that affects chlorophyll molecules, making them unable to capture photosynthetic light, resulting in a disturbed photosynthesis process (Patra and Sharma 2000). ...
... The genus M. (mint) is one of the most significant taxa of the family Lamiaceae, and includes 25 to 30 species grown in different parts of the world [23]. Due to chilling, pleasant fragrance and taste, the essential oils of mint are utilized in perfumery, beauty care products, candy parlor, and the pharmacological enterprises [24]. Similarly, genus R. is very diverse and comprises above 750 species in 12 subgenera found in all continents except Antarctica [25]. ...
Extracts obtained from M. longifolia (Lamiaceae) and R. ellipticus (Rosaceae) were selected to utilize in the reduction and stabilization of silver nanoparticles (AgNPs) for achieving remarkable bioactivities. In brief, the cytotoxic potential of the as synthesize AgNPs was high at higher concentrations. In DPPH assay, maximum antioxidant potential was shown by AgNPs synthesized from M. longifolia. Meanwhile, Methanolic extracts exhibited more antioxidant potential than chloroform based extracts.
Further, brine shrimp lethality assay was carried out to achieve 34.6 μg/mL & 25.65 μg/mL LD50 values against the NPs prepared from M. and R., respectively. In addition, antioxidant activities were carried by ABTS Radical cation assay where 38.6 μg/mL and 47 μg/mL IC50 values were obtained for the NPs obtained from M. longifolia and R. ellipticus, respectively. Reducing power assay (0.370–0.15 and 0.37–0.26 mean absorbance) and DPPH (% scavenging: 88.91–46.48 and 88.91–44.78) percentages were recorded for M. and R. synthesized AgNPs, respectively.
In brief, M. longifolia functionalized particles performed better in comparison to R. ellipticus treated particles. In addition, the nano assembly dispersed in polar solvent demonstrated better results in comparison to non-polar solvents.
In conclusion, the as synthesized AgNPs were better in bioactivities than crude extracts of the selected plants.
In future, this work could be extended to isolating active components for the nanofabrication of biologically intelligent nanoparticles for pharmacological interest. In the proposed investigation, the purified bioactivities fractions would be highlighted for further consideration in various medical treatments.
... The extensive contamination of mercury in soil and sediments results in an increase in atmospheric mercury levels [5]. This pollution adversely affects land quality and hampers plant's vegetative growth, including their roots and shoots [6,7]. Moreover, mercury also poses significant health risks to humans, including heart diseases, cancer, liver disorders, sensory impairments, and developmental disruptions in children [8]. ...
Lebong a regency in Bengkulu Province, possesses prominent potential in gold mining. This mining activity is conducted through amalgamation techniques, resulting in the deposition of mining residue containing mercury, subsequently leading to environmental pollution. Recognizing the hazards associated with such pollution, it becomes imperative to mitigate the presence of mercury through effective remediation strategies. Bioremediation, utilizing Mercury Resistant Bacteria (MRB), widely known as a viable method for mitigating mercury contamination. This study aims to isolate and characterize MRB to facilitate their potential application in addressing heavy metal pollution. This study involved the isolation and characterization of MRB through morphological observations, Gram staining, and biochemical tests (glucose, sucrose, fructose, citrate utilization, starch hydrolysis, urease activity, and catalase production). A total of 43 bacterial isolates were obtained from water, sediment, and soil samples collected from surrounding gold mining waste disposal. Among these isolates, bacteria resistant to mercury were selected on NA supplemented with various concentrations of mercury. Five potential candidates of MRB were identified, with the highest mercury concentration tested being 1000 ppm. Based on identification using Bergey’s Manual of Determinative Bacteriology, it was determined that four out of the five isolates belonged was Pseudomonas , while another belonged to S taphylococcus .
... The previous literature reported that the average size of CDs less than 50 nm could be uptake in the xylem of plants [56]. Moreover, the Hg 2+ stress of the seeding was mitigated by CDs and NCDs due to the free radicals inhibition ( Table 2) [57]. ...
... Some plants accumulate mercury in the shoots because of direct translocation or direct absorption of the metal in its vapor form through the leaves [6]. With lower levels of mercury pollution, the relative amount of flora with high levels of mercury naturally drops [26]. S. caroliniana from which the samples were collected were not located in mercury-rich environments. ...
Remediation of heavy metals is a complex, difficult, and expensive exercise and commonly involves relocation of the problem from one place to another (e.g., a contaminated site to a hazardous waste landfill). Alternatively, bioremediation can be used so that metals can be sequestered into the woody portion of the plant, where they are fixed into the organic matter and remain undisturbed for extended periods (e.g., wetland area soils). A species of willow (Salix caroliniana) was investigated to ascertain its potential for use in the bioremediation of mercury. It was found that the plant did bioaccumulate mercury and did so especially in the wood compared to its leaves (8.8 to 1 ratio in the mercury activity; activity of 12,071 to 1164). While there is moderate potential for use in bioremediation, the measured concentration in the wood was quite low (average of 11.91 ppb). The low concentration was caused by the location of the sampled trees in environments that were either pristine or had low soil concentrations of mercury. Furthermore, 90% of the mercury accumulated in the leaves appeared to be adsorbed via atmospheric deposition in southwest Florida where there are minimal sources of anthropogenic mercury, but the region is impacted by Saharan dust, which does contain mercury.
... Immediately, the peroxidation of proteins and lipids will destroy the integrity of the plasma membrane [4,96]. With Hg stress, plant shows abnormalities in the whole physiological processes, causing toxic effects, inhibiting growth, reducing photosynthesis, and impeding absorption of nutrients [57,58,8]. ...
... Some reports state that Pb adversely affects the protein content and related nucleic acids [4][5][6]. Maximum attention has been paid on the interaction of Pb exposure and antioxidant enzymes [7,8]. ...
The pesticides and heavy metals have profound effect on the total protein of Red and White muscles of Heteropneutes fossilis. The increase in concentration and exposure period has shown great reduction in the quantity from the control value. The two pesticides: Malathion & γ-BHC and two heavy metal compounds lead nitrate and sodium arsenite were found to be significantly decreasing the total protein of these two tissues. However, the decrease in case of lead nitrate was quite noticeable.
... 23 Cadmium (Cd) and mercury (Hg) were found to be highly hazardous toxic metals. 24,25 Even at very low concentrations, Cd can severely change plant enzyme activities and ultimately cause stress. 26,27 Another very potent toxic metal is mercury (Hg) which causes serious crop destruction in plants, alteration in RNA expression, DNA methylation, modifications in histones, and visible injuries and physiological disorders in humans. ...
In plants, ATP-binding cassette (ABC) transporters facilitate the movement of substrates across membranes using ATP for growth, development, and defense. Soils contaminated with toxic metals such as cadmium (Cd) and mercury (Hg) might adversely affect the metabolism of plants and humans. In this study, a phylogenetic relationship among soybeans' (Glycine max) ATP binding cassette (GmABCs) and other plant ABCs was analyzed using sequence information, gene structure, chromosomal distribution, and conserved motif-domain. The ontology of GmABCs indicated their active involvement in trans-membrane transport and ATPase activity. Thirty-day-old soybean plants were exposed to 100 μM CdCl 2 and 100 μM HgCl 2 for 10 days. Physiological and biochemical traits were altered under stress conditions. Compared to Control, GmABC transporter genes were differentially expressed in response to Cd and Hg. The qRT-PCR data showed upregulation of seven ABC transporter genes in response to Cd stress and three were downregulated. On the other hand, Hg stress upregulated four GmABC genes and downregulated six. It could be concluded that most of the ABCB and ABCG subfamily members were actively involved in heavy metal responses. Real-time expression studies suggest the function of specific ABC transporters in Cd and Hg stress response and are helpful in future research to develop stress-tolerant varieties of soybean.
Nutrient starvation is a critical consequence of heavy metal toxicity, severely impacting plant health and productivity. This issue arises from various sources, including industrial activities, mining, agricultural practices, and natural processes, leading to the accumulation of metals such as aluminum (Al), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and nickel (Ni) in soil and water. Heavy metal exposure disrupts key physiological processes, particularly nutrient uptake and transport, resulting in nutrient imbalances within the plant. Essential nutrients are often unavailable or improperly absorbed due to metal chelation and interference with transporter functions, exacerbating nutrient deficiencies. This nutrient starvation, coupled with oxidative stress induced by heavy metals, manifests in impaired photosynthesis, stunted growth, and reduced crop yields. This review presents important insights into the molecular mechanisms driving nutrient deprivation in plants exposed to heavy metals, emphasizing the roles of transporters, transcription factors, and signaling pathways. It also examines the physiological and biochemical effects, such as chlorosis, necrosis, and altered metabolic activities. Lastly, we explore strategies to mitigate heavy metal-induced nutrient starvation, including phytoremediation, soil amendments, genetic approaches, and microbial interventions, offering insights for enhancing plant resilience in contaminated soils.
Agriculture is important for human beings because it provides food, employment, and other necessities, and pollution in agriculture causes several problems. Heavy metals are always at the top of the list regarding concerns about agriculture pollution. Heavy metals reach in agriculture from various sources but the uses of agrochemicals like fertilizers and pesticides in agriculture are the most common sources. The most common heavy metals are arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), nickel (Ni) and zinc (Zn). Heavy metal pollution in agriculture threatens human and animal health, pollutes groundwater, causes plant phytotoxicity, and reduces agricultural productivity and soil health. Heavy metals enter the food chain mostly through the soil, where they are absorbed by plant roots. Once they enter the food chain, they pose a serious risk to each organism linked to that food chain. Heavy metals create imbalances in several crucial processes in plants and soil ecosystems. Heavy metal degradation takes too much time in soil and remains in the soil for a very long time. Heavy metal degradation from the soil ecosystem may be accomplished through the use of bioremediation.
Coastal wetland soils play a critical role in the global mercury (Hg) cycle, serving as both an important repository for total mercury (THg) and a hotspot for methylmercury (MeHg) production. This study investigated Hg pollution in soils dominated by Phragmites australis (PA) and Spartina alterniflora (SA) across five representative China’s coastal wetlands (Yellow River (YR), Linhong River (LHR), Yangtze River (CJR), Min River (MR), and Nanliu River (NLR)). The THg concentrations ranged from 16.7 to 446.0 (96.3 ± 59.3 ng g−1, dw), while MeHg concentrations varied from 0.01 to 0.81 (0.12 ± 0.12 ng g−1, dw). We further evaluated Hg risk in these wetlands using potential ecological risk index (Er) and geographical enrichment factor (Igeo). Most wetlands exhibited low to moderate ecological risk, except the PA habitat in the YR wetland, showing moderate to high risk. Soil organic matter significantly influenced THg and MeHg distribution, while MeHg% correlated well with soil salinity and pH. These findings highlight the importance of organic-rich coastal wetland soils in THg and MeHg accumulation, with the soil properties influencing net MeHg production. Furthermore, SA habitat generally exhibited higher MeHg%, suggesting its invasion elevates the ecological risk of MeHg in coastal wetlands.
Artisanal and small-scale gold mining (ASGM) is the largest global anthropogenic mercury (Hg) source and is widespread in the Peruvian Amazon. Consuming Hg-laden foods exposes people to this potent neurotoxin. While numerous studies have examined fish Hg content near ASGM, Hg accumulation in other commonly consumed animal-and plant-based foods from terrestrial environments is often overlooked. In this study, we aim to address understudied dietary Hg exposures.
To understand Hg exposure from food staples in the Peruvian Amazon, we measured total and methyl Hg in local crops, fish, chicken meat, chicken feathers, and eggs from ASGM-impacted and upstream (reference) communities. Diet surveys were used to estimate probable weekly Hg intake from each food. Fish and chicken stable carbon and nitrogen isotope signatures were analyzed to evaluate trophic magnification.
Though few crops exceeded food safety recommendations, rice methyl Hg proportions were high (84%). Trophic level was an expected key predictor of fish Hg content. 81% (17 of 21) of local carnivorous fish exceeded WHO and EPA recommendations. Compared to upstream communities, mining-impacted communities demonstrated elevated total Hg in crops (1.55 (interquartile ranges (IQR): 0.60–3.03) μg kg⁻¹ upstream versus 3.38 (IQR: 1.62–11.58) in mining areas), chicken meats (2.69 (IQR: BDL–9.96) μg kg⁻¹ versus 19.68 (IQR: 6.33–48.1)), and feathers (91.20 (IQR: 39.19–216.13) μg kg⁻¹ versus 329.99 (IQR: 173.22–464.99)). Chicken meats from mining areas exhibited over double the methyl Hg concentrations of those upstream. Methyl Hg fractions in chicken muscle tissue averaged 93%. Egg whites and livers exceeded Hg recommendations most frequently. Proximity to mining, but not trophic position, was a predictor of chicken Hg content.
Our results demonstrate that terrestrial and aquatic foods can accumulate Hg from mining activity, introducing additional human Hg exposure routes. However, locally sourced carnivorous fish was the largest contributor to an estimated three-fold exceedance of the provisional tolerable weekly Hg intake.
Mercury (Hg) is a naturally occurring heavy metal with wide distribution in the environment in various forms such as elemental, organic, and inorganic. Higher concentrations of mercury radiation, fluctuates from >6000 to 8000 Mg Hg/year, are regarded as a global contaminant which accumulates in the atmosphere because of anthropogenic and natural processes. The soil, water, and air resources are heavily contaminated by these toxic substances due to their high persistence and toxicity. Hg accumulation within plants magnifies the presence of harmful substances in the food web and has the potential to be genotoxic, neurotoxic, and oncogenic. However, higher Hg concentrations are also harmful to plants as it hampers growth-related attributes and impair their physiological and metabolic activities. Consequently, it promotes the risk to food security and the flow of toxicity from targeted sources towards untargeted sources. However, soil cleaning, solidification, thermal and biological treatments are the main topics of discussion to overcome the Hg mobilization in soil.
The effects of mercury complexes on human body and cells vary depending on the extent of exposure and their pharmacological form. Objectives: To characterize mercury complex and then investigate the effects on cellular interaction via cell death. Methods: The synthesis of the mercury complex was carried out, and its characterization was done by FTIR, elemental percentage and powder X-ray diffraction (PXRD). The complex was analyzed through atomic force microscopy (AFM) and by microscopy imaging its surface morphology and cellular interaction were also studied. Results: The presence of the mercury-complex results in cell death in concentration and time dependent manner. Conclusions: The synthesized mercury-complex has the ability to harm cells.
This study aims to determine the effect of biochar application on Hg mobility in a closed leaching experiment using gold processing tailings contaminated soil. The factorial experiment was set up using a Completely Randomized Design (RBD) which tested three types of biochar (rice husk biochar, coconut shell, and corncob biochar) and three doses of biochar (0.10 tons ha-1 and 15 tons ha-1). The PVC column containing a mixture of polluted soil and dibiochar was washed four times with deionized water for a total of 1090 ml of watering. The results showed that the application of biochar can reduce the mobility of mercury (Hg) in small scale gold processing tailings polluted soils. The dissolved Hg concentration in the leachate decreased with increasing dose of biochar application. Leachate from corn cob biochar (15 tons ha-1) treatment showed the lowest Hg concentration of 0.0012 ppm but was not significantly different from leachate from the soil column that was applied coconut shell and rice husk biochar. The concentration of Hg in the leachate for all biochar treatments ranged from 0.0012 - 0.0062 ppm, significantly different from the leachate concentration of the soil column without biochar, which was 1.62 ppm. This provides an indication that biochar can reduce the leaching rate, so that the concentration of Hg is not much leached into the soil. Therefore, biochar can be used as a soil enhancer in remediation of mercury (Hg) polluted soil so that it can slow down the mobility of mercury (Hg) so that it has a small impact on the environment.
Mercury is a highly hazardous heavy metal that has no recognised biological use in the human body. It exists in three forms viz. Elemental mercury, Organic mercury and Inorganic mercury. All these three forms have been proven to have hazardous impact on living community. It has the capacity to accumulate in the various tissues of body and increases its concentration when moves up from lower to higher trophic level. Living beings are potentially in danger due to the development of industrial technology, the widespread and uncontrolled use of synthetic chemicals like herbicides, fertilisers, insecticides and fungicides, as well as industrial effluents. Coal-fired thermal power plants serve as the principal source of mercury poisoning fall to the ground from the air and then wash into a water body. Organisms of aquatic biota are easily exposed to and ingest mercury deposits in the tissues especially in gonads, liver, kidney and gills. Long-term mercury exposure damages the nervous system and causes tremors, spasms and memory loss, hallucinations, severe sadness, and increased excitability, delirium and personality alterations. Alterations in the histopathology and cytology are the initial indications of stress upon mercury toxicity. Several histological aberrations have been observed on the cellular level. The current study provides an understanding of the systematic adverse effects of mercury content on the neurological and cytological features of plants, animals and humans. Additionally, it highlights the significance of cytology and neurology as a tool for a more accurate assessment of mercury in toxicity control programmes. The molecular mechanism behind the toxico-kinetics of mercuric toxicity in living organisms requires more investigation in order to develop detoxifying techniques that will enhance general health.
Mercury is a global pollutant that poses significant risks to human health and the environment. Natural sources of mercury include volcanic eruptions, while anthropogenic sources include industrial processes, artisanal and small-scale gold mining, and fossil fuel combustion. Contamination can arise through various pathways, such as atmospheric deposition, water and soil contamination, bioaccumulation, and biomagnification in food chains. Various remediation strategies, including phytoremediation, bioremediation, chemical oxidation/reduction, and adsorption, have been developed to address mercury pollution, including physical, chemical, and biological approaches. The effectiveness of remediation techniques depends on the nature and extent of contamination and site-specific conditions. This review discusses the challenges associated with mercury pollution and remediation, including the need for effective monitoring and management strategies. Overall, this review offers a comprehensive understanding of mercury contamination and the range of remediation techniques available to mitigate its adverse impacts.
Graphical Abstract
Bibliometric analysis is an important tool for the assessment of research trends on a topic of interest. With the rising demand for research on sediments, the current work is aimed to evaluate the number of publications, major countries involved, and major thrust areas of research using the search keywords “sediment organic carbon” and “sediment heavy metals.” The bibliometric recovery of 1367 publications was done from the Scopus database during the study period of 23 years, that is, from 2000 to 2022 (till August) and the analyses were performed using VOSviewer and Biblioshiny software. The result showed a greater number of publications on sediment organic carbon than the heavy metals. Research articles were the most preferred publication type as compared to book chapters, conference proceedings, review articles, and so on. No particular journal was found to have a significant impact on the topic of research, but Chemosphere and Marine Pollution Bulletin showcased the highest impact on publication with an H‐index score of 36 each. While, China dominated the research on the concerned topic followed by India and the United States, a low level of inter‐country collaboration was however detected in the analysis suggesting a regional influence on sediment‐related topics. “Risk assessment,” “Geo‐accumulation index,” and “Potential ecological risk” were the major focal areas that were associated with the assessment of sediment quality and heavy metal accumulation. It can be concluded that sediment related research has been regionally focused. More inter‐country collaborations can aid in trans‐disciplinary research related to sediments in the future.
Artificial grow lights, such as light-emitting diodes (LEDs) and fluorescent grow lights, are commonly used in modern day indoor farming, citing advantages in energy efficiency and a higher controlled environment. However, the use of LEDs poses a risk in mercury contaminations as a result of its production process, specifically LEDs with polyurethane encapsulates that were traditionally produced using mercury resins as a catalyst. A total of 10.0 ppm of mercury was detected in a curly kale sample harvested from an indoor hydroponic vegetable farm, exceeding Singapore Food Regulation's limit of 0.05 ppm. Vegetables, farming inputs, and surface swabs from the affected farm were analyzed using wet acid digestion followed by cold vapor atomic absorption spectroscopy analysis. The investigation found high concentrations of mercury in the LED encapsulant, and the encapsulant material was identified to be polyurethane by Fourier transform infrared spectroscopy and pyrolysis-gas chromatography-mass spectrometry analysis, indicating the source of mercury contamination to be the LED polyurethane encapsulant.
Total concentrations of Hg in soils and the narrow-leaved fireweed Chamaenerion angustifolium L., as well as the forms of Hg presence in soils by the method of sequential extractions were examined to study the processes of mobilization-immobilization of Hg in the soils of the territory of the chlor-alkali plant sludge storage and the features of the bioaccumulation of this element in herbs. The determination of Hg in all samples was carried out by the atomic absorption method. High concentrations of Hg in soils near the sludge storage have been established. In almost all soil samples the amount of Hg is above the regional background. Fractionation showed that Hg in soils is found mainly in organic, strongly bound and sulfide fractions. Due to the low concentrations of Hg mobile fractions, water- and acid-soluble, a relatively low accumulation of Hg in Chamaenerion angustifolium L. was found, which was also facilitated by the barrier properties of the herb roots. Nevertheless, the accumulation of predominantly organic and strongly bound forms of Hg in soils indicates a high potential for Hg mobilization from these fractions due to changes in various physicochemical and biogeochemical properties of soils.
Elementares Quecksilber ist das einzige bei Raumtemperatur flüssige Metall und besitzt im Vergleich zu anderen Metallen einen relativ hohen Dampfdruck. In seinen Salzen tritt es fast ausschließlich als zweiwertiges Ion auf. Unter Quecksilberverbindungen versteht man Verbindungen, die mindestens ein Quecksilberatom enthalten. Als quecksilberorganische Verbindungen wie Methylquecksilber, Ethylquecksilber oder Phenylquecksilber (auch “Quecksilberorganyle” oder “Organoquecksilberverbindungen”) werden solche Verbindungen bezeichnet, die mindestens eine kovalente Quecksilber‐Kohlenstoffbindung enthalten, nicht jedoch Quecksilber‐Salze organischer Säuren. Aufgrund der kumulativen toxischen Effekte vieler Hg‐Verbindungen sind weiterhin Bemühungen zur Reduktion jeglicher Hg‐Einträge in Böden erforderlich und Einträge zu überwachen. Die Datenbasis dafür ist zu vergrößern.
Heavy metal contamination of soil poses a serious threat to soil quality and crop productivity worldwide. Heavy metals in the environment affect all life forms, whereas lighter metals could be toxic, depending on their accumulation in body tissues. Anthropogenic activities have subsidized their discharge from natural sources to water bodies, atmosphere, and soil, consequently, creating a polluted environment for life forms. It becomes imperative to support and strengthen plant performance in contaminated environment for safe and healthy food production. To date, many scientific methods have been introduced to remediate heavy metal toxicity in plants, predominantly by applying biostimulants. Biostimulants encourage the existing chemical and biological processes in the plant and associated microbes to augment the plant’s growth, yield, and quality by enhancing nutrient uptake, nutrient use competence, and tolerance to abiotic stress. This chapter focuses on the use of biostimulants for plant growth enhancement and for the alleviation of heavy metal toxicity in plants.
Exposure of corn seedlings to different concentrations of the toxic heavy metal mercury(II) led to significantly altered activities of the enzyme glutathione transferase (GT, EC 2.5.1.18) important in glutathione utilization in this plant. Markedly elevated activities were found in the shoots. In the roots, however, the activities slightly decreased, induction was observed only after 3 days of exposure to 30 μM mercury concentration. The induction of GT activity was generally preceded by a decline. These responses are specific, as indicated by their time course and dose-dependence.
The effects of different concentrations of eleven different metals (aluminum chloride, chromium nitrate and potassium dichromate, lead nitrate, copper sulfate, manganous sulfate, cobaltous nitrate, zinc sulfate, magnesium sulfate, nickel sulfate, cadmium chloride, and mercuric chloride) on cell division and nucleoli in root tip cells of Allium cepa were studied. The results showed that the metal ions could, in varying degrees, cause chromosome, nucleus, and nucleolus irregularities, including c-mitosis, chromosome bridges, chromosome stickiness, irregularly shaped nuclei, micronuclei, irregularly shaped nucleoli, some silver-stained material scattered in the nucleus, the weakening of silver-staining reaction at the periphery of the nucleolus, and the release of nucleolar material from the nucleus into the cytoplasm. The Allium test may be useful for the rapid screening of chemicals involved in environmental problems.
The study investigated the absorption and some physiological effects of mercury in water hyacinth (Eichhornia crassipes) plants found in Laguna de Bay. Plants of approximately similar size and vigor were collected from natural populations in the lake for the experiments. To which was added 1.0, 10.0, 20.0 and 50.0 ppm of the heavy metal for six days. Analysis of the mercury content of submerged and aerial tissues of the plant was done on the second, fourth and sixth day. Submerged tissues consistenly accumulated more of the heavy metal than the aerial tissues. The higher the level of mercury in the growth medium, the higher was the concentration of the heavy metal in the plant tissue. The physiological responses of the water hyacinth plant to various levels of mercury in the culture solution was determined in terms of gain in plant fresh weight, root growth, leaf development and chlorophyll content, ramet production and visible leaf injury symptoms. The addition of mercury caused a decrease in fresh water and an inhibited root growth and ramet production. The higher the level of mercury in the culture medium, the greater was the degree of growht inhibition. Leaf development, however, was not greatly affected by mercury. The addition of 0.005 and 0.005 and 0.01 ppH Hg. THe chlorophyll content of the mature leaves of plants that grow under 1.0 2.0 ppm Hg was greatly reduced. Visible leaf injury in terms of drying tips and necrotic spots was noted in plants grown in culture solution cotaining various levels of mercury. The higher the concentration of mercury, the greater was the degree injury.
A study was made of the pattern of distribution of mercury in the tissues of some plant species collected around a chlor-alkali factory in India. Different plants accumulated different levels of mercury in their tissues. Accumulation in leaves was the highest, followed by the stem and the root and, in some cases, the root and the stem. A significant correlation was noted between the mercury concentration of the soil and the plant tissues and between different tissues. Grazers (goats, sheep) also accumulated significant levels of mercury in their tissues.
I intend to fill, with this book, a need that has long been felt by students and professionals in many areas of agricultural, biological, natural, and environmental sciences-the need for a comprehensive reference book on many important aspects of trace elements in the "land" environment. This book is different from other books on trace elements (also commonly referred to as heavy metals) in that each chapter focuses on a particular element, which in tum is discussed in terms of its importance in our economy, its natural occurrence, its fate and behavior in the soil-plant system, its requirement by and detriment to plants, its health limits in drinking water and food, and its origin in the environment. Because of long distance transport to pristine areas of cadmium, lead, copper, and zinc in relatively large quantities, these elements have an extra section on natural ecosystems. A blend of pictorial and tabular data are provided to enhance understanding of the relevant information being conveyed. Since individual chapters are independent of one another, they are arranged alphabetically. However, readers with weak backgrounds in soil science are advised to start with the chapter on zinc, since soil terminology is discussed in more detail here. Sections on sorption, forms and speciation, complexation, and transformations become more technical as soil physical-(bio )chemical phenomena are discussed. The less important "environmental" trace elements are discussed together in the "Other Trace Elements" chapter.
The genetic activities on cytoplasmic respiration-deficient mutation and nuclear mitotic crossingover, mitotic gene conversion and reversion of several metal ions were studied in Saccharomyces cerevisiae. The results show that Cd, Cu, Mn and Hg ions cause cytoplasmic respiration-deficient mutation in S. cerevisiae strain N123, and all of the metalions inhibited growth and were highly toxic on living yeast cells. The surviving cells of diploid yeast S. cerevisiae strain D7 were also reduced by the treatment of all metal ions at the concentrations of 10⁻² -10⁻⁴ M, but no mitotic crossingover was observed. Mitotic gene conversion was induced by Co, Cr, As and Cd ions and mitotic crossingover in convertants was observed by treatment with Cr, Mn, Ni and Cd ions. In the case of Pb and Hg, less mitotic gene conversion was observed but crossingover in convertants increased in higher concentrations of metals, and no genetic activities were shown by Cu and Zn. Only Mn ion induced reversion, point mutations, at high level but not in all other metals.
Trace elements refer to elements that occur in natural and perturbed systems in small amounts and which, when present in sufficient concentrations, are toxic to living organisms. Introductory comments are made on biogeochemical cycles of trace elements; their resources; soil and plant capacities for such chemicals; and trace elements in the food chain. There follow chapters on As, B, Cd, Cr, Cu, Pb, Mn, Hg, Mo, Ni, Se and Zn, reviewing for each element its general properties, production/uses, natural occurrence, and sources in the terrestrial environment, and its environmental and ecological behaviour and significance in soils, plants, drinking water and food. A final chapter outlines these characteristics for Sb, Ba, Be, Co, F, Ag, Tl, Sn, Ti and V.-P.J.Jarvis
An experiment using artificial acidification has been carried out under subarctic conditions in northern Finland. Vegetation samples from plots treated with simulated acid rain (pH 4 and pH 3) were analysed for their contents of aluminium, cadmium, manganese, mercury and zinc and compared with wet and dry control plots. No or only small differences in metal contents were detected between the plots. The acidification experiment is going to be continued and the contents of metals should be followed up for a longer period of time.
Effects of heavy metals (Lead, Mercury and Cobalt) were studied on the activities of aminotransferases and starch degrading enzymes (α-amylase and β-amylase) in leaves of young Sorghum vulgare seedlings. Pb, Hg, and Co in general, had a favourable effect on the activities of alanine aminotransferase (GPT), aspartate aminotransferase (GOT). The activity of α-amylase and β-amylase was promoted by Hg and Co except in the highest concentrations of Hg used (50 ppm) where a decrease in the activity of both enzymes was notified.
A number of industrial installations at Aligarh, dump large quantities of effluents containing heavy metals such as Chromium, Copper, Iron, Nickel and Mercury, which reach and contaminate our crops, forage and other pasture plants. Mercury, Copper and Chromium tolerance of four pasture plants during germination stage was studied. The relative order of the metal toxicity was Hg greater than Cu greater than Cr. Of the four pasture plants, legumes (Indigo fera enneaphylla Linn. and Desmodium triflorum DC. ) were found most tolerant and the other forb (Eclipta alba Hassk. ) the least.
HgCl2 tolerant (up to 18 μg/ml) variants were selected from N-methyl-N- nitrosoguanidine (NTG) treated suspension cultures of V. unguiculata grown in MS-3 medium. The frequency of appearance of tolerant cells was 1.93 x 10-7 to 4.19 x 10-6. Maximum HgCl2 tolerant calli were recovered from cells treated with 10 μg/ml NTG. Hg tolerance was not lost during long term culture in absence of Hg stress, however, the number of tolerant calli dropped from 89 to 9. The significance of these observations has been discussed.
Toxicological effects of leached mercury from the Chlor-alkali industry on the changes in residual mercury content and pigment content in Pistia and Hydrilla were studied. The plants were exposed to 500 mg l-1 of the solid waste of a Chlor-alkali industry in an aquarium under controlled conditions for 28 days. At 7 d interval period, plants were taken out for pigment and residual mercury analysis. Drastic depletion in chlorophyll content was marked in the exposed plant leaves when compared to control leaves. A significant increase in phaeophytin and carotenoid level was marked in exposed plant leaves, when compared to control plant leaves. A positive and significant increase in residual mercury level was observed in the exposed plants with an increase in exposure period.
The critical values of heavy metal elements in soil are: Hg 0.5ppm, Cd 1.2ppm, Pb 20ppm, Cu 160ppm, Zn 500ppm, and Ni 30ppm. -from Authors
Metal analyses performed with atomic absorption spectrophotometry revealed no differences in Vaccinium myrtillus growing in Myrtillus-type forest in the catchment areas of an acidified and nonacidified lake in Espoo, southern Finland. Earlier, higher contents of Al, Zn and Cd were found in plants collected over the whole catchment area of the acidified lake (where barren forest types predominate). This suggests that the proportions of different vegetation types in the catchment area determine the degree of lake acidification. This conclusion was supported by the observation that the contents of Cd were significantly higher in plants growing in the more barren forest site types. No significant differences were found for Al. The plant nutrients Fe and Zn showed the highest levels in the most fertile forest type. The contents of Al and Fe in V. myrtillus leaves increased with decreasing distance from the shoreline of the lakes, but no such increase was noted for Zn, Cd or Hg. Clearly higher contents of Al, Fe and Hg were observed in V. myrtillus leaves in autumn than in spring, whereas Zn showed higher levels in the spring. In future work, attention should be paid to seasonal changes in the contents of metals in plants.
Changes in the pigment content of a mulberry plant exposed to solid waste of a chlor-alkali industry was reported. Initial appearance of brown patches followed by total browning of the leaf lead to fall of all leaves in the exposed plant. Drastic but significant decline in pigment contents in exposed plants were observed at higher concentrations of the solid waste and at prolonged exposure periods. However, on initial increase in the parameters were also recorded.
The authors studied the effects of various concentrations of six heavy metals on the growth of secondary callus tissue cultures of Ruta graveolens L. The experiments were aimed at determining the limits of tolerance shown by the cell population of rue to the compounds applied and to their divalent metal ions, respectively. The following ions were put to test: cadmium (Cd), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn). The concentrations ranged between 10-4 to 10-6 M, or from 10-5 to 10-7 M in the case of mercury. The incubation culture medium contained WHITE'S macroelements (1954) completed with HOAGLAND's microelements and with 6 mg 2, 4-D and 4 mg IAA per litre. The incubation lasted 4 weeks at a temperature of 25 (±2)°C with 16-hour light and 8-hour dark periods. The rate of illumination was 120 W/m . The effect of the heavy metals used in the experiments was characterized by the change in the fresh and dry weight of the callus tissue and in the nuntier of cells per units weight. As seen from the results of the experiments the effect of the metal ions and compounds was a function of the concentration; nevertheless, any concentration applied inhibited the growth of the fresh weight of rue callus. In comparison to the control it was inhibited most by copper and least by lead and mercury, and the highest concentrations of nickel and copper evan caused lethality. The dry weight increased in inverse ratio to the inhibition of fresh weight, due to the dehydration of the calls, a sign of the toxicity of heavy metals. The number of cells varied, often it was the same as in the control. As shown by the experiments the toxicity of heavy metals may manifest itself in the dehydration of cells. Further, the results obtained indicate that the limit of tolerance to toxic heavy metals may vary with the plant species, it is therefore desirable to carry out screening with as many species as possible (MARÓTI and BOGNÁR, 1985).
The mercury content of the epiphytic lichen Hypogymnia physodes was used to investigate the long-range transport of mercury in air and mercury air pollution in Finland. Highest background values were found in SW Finland, indicating an influx of mercury with the prevailing winds. High concentrations were found near the three Finnish chlor-alkali works. Refs.
Bacteria carry out chemical transformations of heavy metals. These transformations (including oxidation, reduction, methylation, and demethylation) are sometimes by-products of normal metabolism and confer no known advantage upon the organism responsible. Sometimes, however, the transformations constitute a mechanism of resistance. Many species of bacteria have genes that control resistances to specific toxic heavy metals. These resistances often are determined by extrachromosomal DNA molecules (plasmids). The same mechanisms of resistance occur in bacteria from soil, water, industrial waste, and clinical sources. The mechanism of mercury and organo- mercurial resistance is the enzymatic detoxification of the mercurials into volatile species (methane, ethane, metallic Hg0) which are rapidly lost from the environment. Cadmium and arsenate resistances are due to reduced net accumulation of these toxic materials. Efficient efflux pumps cause the rapid excretion of Cd2+ and AsO43−. The mechanisms of arsenite and of antimony resistance, usually found associated with arsenate resistance, are not known. Silver resistance is -due to lowered affinity of the cells for Ag+, which can be complexed with extracellular halides, thiols, or organic compounds. Sensitivity is due to binding of Ag+ more effectively to cells than to CI−.
Methylmercury chloride is a powerful inhibitor of the cell cycle in Yeasts. Its effect is reversible at low doses. It does not induce any nuclear mutation (at least among the ones we tested). Neither does it increase the amounts of intra and inter-genic conversions induced by a variety of mutagenic agents. However, in co-treatment with some carcinogens and mutagens, it causes a drastic depressive effect on survival.
Mercury pollution of the environment is a persistent problem despite legislative controls on its use. This article traces the history of mercury levels in Swedish fauna over the last 150 years, drawing particular attention to the fact that levels of mercury in Swedish birds and animals decreased sharply after the use of alkyl mercury compounds as seed dressing was banned in Sweden in 1966. Nevertheless, mercury in industrial emissions and its long-range transport and deposition in Scandinavia still pose a threat, especially to fauna which feed on aquatic organisms.
This investigation was intended to find out if the high mercury contents in Swedish seed-eating birds could be explained by the consumption of methyl and ethyl mercury-treated seed grain which had not been covered with earth during sowing. Pheasants no. 1-7 were shot in January 1965 within in area which in March-April 1964 had to c. 40% and in September to c. 15% been sown with methyl mercury dicyandiamide-treated seed grain of cereals. Pheasants no. 8-10 were shot in December 1965-January 1966 within an area which in the autumn 1965 had to c. 25% been sown with ethyl mercury halogenide-treated seed grain of cereals. The body weights (g) of these pheasants, mercury contents (μg/g and mg) in musculature, liver, kidneys and plumage and mercury contents (μg/g) in claws are shown in Tab. 2. Pheasants no. 11-18 were shot in the same area as pheasants no. 1-7 in December 1966. The seed grain had during this year been treated with mercury-free disinfectants. No mercury could be found in the organs, plumage or claws. The total mercury consumption could be calculated for pheasants no. 1-7 to be 16.89, 8.49, 3.75, 2.63, 2.17, 0.51 and 0 mg, respectively, and for pheasants no. 8-10 to 6.74, 2.02 and 0.18 mg, respectively. The amount of seed grain from the autumn sowing 1964 which was left on the surface and therefore was available to seed-eating birds within the area where pheasants no. 1-7 were shot was estimated to be c. 6 kg/hectare. Since the methyl and ethyl mercury-treated seed grain contained on average 16 mg Hg/kg, the consumption of treated grain of pheasants no. 1-7 was calculated to be 1.06, 0.53, 0.23, 0.16, 0.14, 0.03 and 0 kg, respectively, and for pheasants no. 8-10 to 0.40, 0.13 and 0.01 kg, respectively. Against the background of these figures it seems that the alkyl mercury-treated seed grain left on the surface during sowing could completely explain the remarkably high mercury contents in pheasants and other seed-eating birds and therefore also in their predators. /// Исследовались причины высокого содержания ртути у швецских птиц, питающихся семенами злаков. Это может быть объяснено применением метил- и этил- ртутных соединений для обработки семян пшеницы. Птицы поедяют зерна, которые не покрываются почвой во время посева. Фазаны N o 1-7 застрелены в январе 1965 г. на участках, которые в марте-апреле 1964 г. на 40% и в сентябре - на 15% были засеяны семенами злаков, обработанными метиловым ртутным дицианидамидом. Фазаны N o 8-10 застрелны в декабре 1965 г. - январе 1966 г. на участках, которые осенью 1965 г. на 25% были засеяны семенами злаков, обработанными ртутными галогенидами. Получены данные по содержанию ртути в мускулатуре, печени, почках, оперенье и когтях фазанов. Фазаны N o 11-18 застрелены в тех же участках, что и фазаны N o 1-7, в декабре 1966 г. Семена в течение этого года не обрабатывались веществами, содержащими ртуть. Во внутренних органах фазанов, опереньи и когтях ртуть не обнаружена. Общее потребление ртути, рассчитанное для фазанов N o 1-7, составляет 16,89; 8,49; 3,75; 2,63; 2,17; 0,51 и О мг, а для фазанов N o 8-10-6,74; 2,02 и 0,18 мг. Количество семян, которое осталось на поверхности почвы от осенних посевов 1964 г. и таким образом было доступно для птиц, на участках, где застрелены фазаны N o 1-7, достигло 6 кг/га. Поскольку семена, обработанные метил- и этил- ртутными соединениями, имели среднее содержание ртути 16 мг/1 кг, потребление обработанных семян фазанами N o 1-7 составляло соответственно 1,06; 0,53; 0,23; 0,16; 0,14; 0,03 и 0 кг, а фазанами N o 8-10-0,40; 0,13 и 0,01 кг. На этом основании можно заключить, что семена, обработанные акильной ртутью и оставленные на поверхности почвы во время посева, могут быть причиной высокого содержания ртути у фазанов и других семеядных птиц, а, следовательно, и у их вредителей.
生産地の明かな,シイタケ原木栽培子実体37検体および菌床栽培子実体とその菌床培地19検体を収集し,子実体間の一般成分値ならびに無機質量を比較した.また,菌床成分と子実体成分の相関についても検討を行った.原木栽培シイタケ子実体は炭水化物およびカルシウム,銅,マンガン,水銀の各元素含量が菌床栽培品よりも有意に高く,逆に水分,タンパク質,灰分およびカリウム,リン,亜鉛の各元素では有意に低い結果を示した.菌床栽培シイタケでは培地窒素含量と子実体窒素含量に有意の相関がみられ,これは菌床栽培シイタケ子実体のタンパク質が原木栽培ものよりも高いことを良く説明している.菌床より子実体への無機元素の濃縮はカリウム(3.15倍),ナトリウム(1.68倍),リン(1.21倍),カドミウム(11.58倍)で見られたが,培地と子実体間に有意の相関がみられたのはリンのみであった.カルシウムと鉄は培地からの濃縮は見られなかったが,培地と子実体問で有意の相関がみられた.
Appropriate compost standards are being considered in Canada. Five aspects of compost safety and quality are being evaluated; probably the most controversial aspect is the standards for metals in compost. In order to assist in the development of appropriate standards, the authors began an extensive research project in October, 1993 to determine the bioavailability of metals from compost and compost-metal mixtures. Swiss chard was grown in compost-amended soils or compost in a growth room using five treatments of increasing percentages of compost in the media (0, 25 percent, 50 percent, 75 percent, 100 percent compost (v/v)). A Truro loamy sand and a race-track manure-biosolids compost (RTM-biosolids) supplemented with a high metal biosolids were used in a completely randomized design with five replicates. Dry matter yield, metal content in plant tissue, and total metal uptake were evaluated as well as the total and DTPA-extractable metal content in the compost-soil mixes. The results of this and five other experiments conducted by the authors will help determine whether the suggested limits for As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se and Zn in composts are appropriate.