Human health risk assessment of heavy metals in the soil–Panax notoginseng system in Yunnan province,China

In this study, a total of 69 topsoil samples and 10 Panax notoginseng samples from Yunnan Province were collected and the concentrations of As, Cd, Cu, Hg, Ni, Pb and Zn in all the samples were determined. The hazard index (HI), total carcinogenic risk (TCR) and estimated daily intake (EDI) of heavy metals were calculated to assess the health risk of P. notoginseng growers and consumers. The average concentrations of As, Cd, Cu, Hg, Ni, Pb and Zn in P. notoginseng planting soils are 43.6, 0.55, 50.8, 0.30, 73.4, 58.2, and 161 mg/kg, respectively. The average Nemerow integrated pollution index of heavy metals in soils is 1.8, indicating that the P. notoginseng planting soils are slightly polluted by those heavy metals. The average HI value is 1.29 and the TCR value of As is above the threshold value, suggesting that As pollution in soil has adverse impact on local growers' health. P. notoginseng is polluted by Cd, As and Pb. 39.1% of estimated daily intakes of As for P. notoginseng consumers through leaf consumption exceeding its permitted daily exposure dosages, suggesting that there is a potential health risk for P. notoginseng consumers to consume P. notoginseng leaves.     

Regional distribution characteristics and ecological risk assessment of heavy metal pollution of different land use in an antimony mining area – Xikuangshan,China

Abstract

Mining activities have introduced various heavy metals and metalloids to surrounding soil environments, causing adverse impacts to the ecological environment system. The extremely high concentration of various heavy metals and metalloids make the Xikuangshan (Hunan, China) an excellent model to assess their ecological risk. In this study, the soil samples from 26 locations of different land use methods in four areas (smelting area, road nearby ore, mining area, and ore tailing area) in Xikuangshan with different levels of various heavy metals and metalloids (Sb, As, Pb, and Cd) were analyzed; in addition, the index of geo-accumulation and the potential ecological risk index were used to evaluate ecological risk. The results showed that the average contents of Sb, As, Pb, and Cd in all soil samples were 4368.222?mg·kg^?1, 40.722?mg·kg^?1, 248.013?mg·kg^?1, and 40.941?mg·kg^?1, respectively, implying serious contamination of compound pollution of heavy metals in soil. The concentration of heavy metals in soil among smelting area, road nearby ore, mining area, and ore tailing area showed significant distribution characteristics of region because different mining activities such as smelting, mining, transportation, and stacking caused different pollution intensity. Moreover, the contents of Sb in soil samples decreased successively in residue field, wasteland, forestland, sediment, grassland, and vegetable field, and the contents of Sb in vegetable-field and ecological restoration grassland were relatively low, which indicate that the method of grassland ecological restoration is an effective method to control antimony pollution in soil. The results of ecological risk assessment showed that the antimony mining area was seriously polluted by Sb, As, Pb, and Cd, and had strong ecological risk, and Sb and Cd were the most important pollution factors, which indicated that the pollution of Sb and Cd should be a major concern of relevant departments of environment and health.     

Heavy metals contamination and human health risk assessment in soils of an industrial area,Bandar Abbas – South Central Iran

The purpose of this study was to determine the contamination level, distribution, health risk and potential sources of Cr, Cd, Pb, Zn, Cu, Ni and As in 66 topsoil samples from industrial areas in Bandar Abbas County. The geoaccumulation index, pollution index and pollution load index were calculated to assess the pollution level in the industrial soils. The hazard index and carcinogenic risk were used to assess human health risk of heavy metals. Results showed that the contamination levels of heavy metals were in the descending order of Cu> Cd> Pb> Zn> As> Ni> Cr. Moreover, based on principal component analysis, Cd, Zn, Cu, and Pb originated mainly from anthropogenic sources, including power plants, oil and gas refinery, steel and zinc production factories and municipal waste landfills. For non-carcinogenic effects, hazard index of studied metals decreased in the order of Cr> As> Cd> Pb> Ni > Cu> Zn. Arsenic, chromium and cadmium were regarded as the priority pollutants. Carcinogenic risks due to Cd and As in suburban soils were within tolerable risk to human health; however, children faced more health risk in their daily life than adults via their unconscious ingestion and dermal contact pathway.     

Assessment of a heavy metals‐contaminated site using sequential extraction,TCLP, and risk assessment techniques

The mobility of selected heavy metals in contaminated soil at a previous industrial site in Brisbane, Australia, was assessed using a sequential extraction technique. Copper, Pb, Zn, Cr, Fe, and Mn were extracted from the soil solution/exchangeable, carbonate, Fe and Mn oxides, and organic matter fractions. The amounts of metals adsorbed by these fractions were used as an indicator of each metal's mobility in the soil. Copper and Pb were largely adsorbed by the organic and oxide fractions, while a significant amount of Zn was extracted from the carbonate fraction. The potential mobility and biological availability of the metals in these soils is Zn > Cr = Cu ≈ Pb. Soils were also analyzed using the toxicity characteristic leaching procedure (TCLP) to determine whether the contaminated soil could be disposed of by landfilling. The leachability of all metals from the soils was very low, with metal concentrations below the allowable limits. The TCLP also showed that Zn was the most mobile metal in these soils. An environmental and health risk assessment was undertaken, and it was concluded that the site did not represent a risk despite the “total”; concentrations of some metals being up to 40 times the investigation threshold value adopted in Australia.     

Distribution features and internal relations of heavy metals in soil–maize system of mining area,Anhui Province,Eastern China

A total of 59 topsoil and corresponding maize plants were collected from this study area. The spatial distribution, correlation analysis, and multiple linear regression of heavy metals were researched detailedly in this article. The results showed that distribution characteristics of heavy metals (Pb, Cd, and Ni) in different parts of maize plants (immature stage) accumulated mostly in stems, with Pb mainly accumulated in roots (mature period), and Cd and Ni mostly in leaves. Except for the southeastern local region of this mining area, Mn and Cu possessed roughly similar spatial distribution characteristics. The results of partial correlation analysis indicated that Cu, Cd in the roots of the tested maize plants and Ni in soil may have antagonistic effects, Cu (soil)–Cu (stem) and Ni (soil)–Pb (stem) had a certain promoting effect. Besides, Cu, Pb, and Ni in soil promoted the absorption of Cu, Pb, and Ni in the leaves, whereas Cr and Pb in soil can promote the enrichment of Mn in maize grains. Our findings suggested that the concentrations of heavy metals in maize organs could be predicted accurately using the established models.     

Environmental risk assessment of heavy metals pollution in aquatic ecosystem—A case study: Sediment of Kor River,Iran

A comprehensive investigation of fractionation and environmental risk of nine heavy metals is carried out for 12 sediment samples collected from Kor River, Iran. For this purpose, the 5-stage sequential extraction method, along with individual contamination factor, global contamination factor, and Environmental Risk Index (ERI), is used. Total concentrations of Cr, Hg, Ni, and Zn were found to be beyond the threshold effect level. The results of fractionation patterns indicate that As, Cr, Ni, Pb, and Zn are mostly associated with Fe-Mn oxide fraction, organic fraction, and residual fraction, while Cd and Mo are predominantly associated with carbonate fraction. Cu and Hg are mostly associated with organic and exchangeable fractions. The results of ERI revealed High to Dangerous risks in 40% of Kor River stations. The applied approach in this study is beneficial to other environmental studies that require analysis of complex data.     

Prevalence of dermal pathway dominance in risk assessment of contaminated soils: A survey of superfund risk assessments, 1989–1992

Exposure to soil‐borne contaminants can occur through ingestion, inhalation and/or dermal absorption. A study was undertaken to assess the relative frequency with which dermal exposures are predicted to pose the greatest risk attributable to contaminated soils in Superfund risk assessments. Screening of over 200 risk assessments from the period 1989–1992 resulted in identification of 37 sites at which projected lifetime excess cancer risks attributed to dermal contact with soil were greater than the nominal regulatory threshold of 1.10^‐4. At 19 of these sites, the dermal/soil pathway is estimated to contribute the largest carcinogenic risk associated with surface soil contamination, and may therefore drive cleanup of that medium. At 9 of the sites, the dermal/soil pathway is predicted to present a higher carcinogenic risk than any other pathway. Chemical contaminant type and estimates of soil adherence and surface area exposed appear to be the primary factors that distinguish sites at which dermal/soil pathway carcinogenic risk estimates are elevated relative to other exposure pathways. Quantification of exposure parameters, especially those related to behavior, remains a significant need.     

Pollution,source, and ecological risk assessment of trace elements in surface sediments of Lake Aktaş, NE Turkey

This study applies ecological indices to determine the anthropogenic-based metal enrichment and potential ecological and ecotoxicological risks posed by each metal in the sediments of Lake Akta?, NE Turkey. Sediment samples were collected from nine stations (St1–St9) within the Turkish boundary of Lake Akta? and the heavy metal, total organic carbon %, CaCO₃%, chlorophyll degradation products (chlorophyll-α), total sulfur %, and total phosphate % contents in the sediment samples were determined. Enrichment factor (EF), pollution load and potential ecological risk (PER) indices were calculated to shed light on the ecological effects of heavy metals. The metal content was ranked in descending order of Al > Fe > Mn > Zn > Ni > Cr > Cu > Pb > As > Cd > Hg. The EF values ranged 0.87–1.0 for Cu, 1.04–1.14 for Pb, 1–1.08 for Zn, 0.88–0.95 for Ni, 0.99–1.24 for Mn, 0.89–0.93 for Fe, 0.82–1.01 for As, 0.96–1.19 for Cd, 0.94–1.0 for Cr, and 1.42–1.90 for Hg. Minimal contamination was found for Hg. Pollution load, PER, and toxic risk indices indicated no ecological risk currently. However, considering the PER index for metals individually, a moderate potential risk was detected for Hg. The data obtained from multivariate statistical analyses indicate that Hg and Mn originate from the atmosphere, while other elements have lithogenic sources.     

Aquatic plants–based risk model for assessment of ecological safety of rivers

In order to ensure the ecological safety in river beds, each project affecting it must be subjected to an evaluation in terms of its implementation results on the river habitats. Technical activities in the river beds can cause irreversible changes in their biocenosis. However, due to the lack of a method that allows us to predict these changes, the decisions made by designers and contractors can be evaluated only after completing the investment. Therefore, it is necessary to elaborate a method to evaluate the environmental safety in regulated and maintenanced rivers. This article presents a model that allows us to predict the changes in vascular aquatic plant communities, which result from technical interference in the river bed. The model was elaborated based on the results of the study performed in 2007–2011 in natural and transformed lowland watercourses from Lower Silesia area (Poland). It takes into account the elements of the watercourse bed ecosystem, which significantly affect the magnitude of the changes in plant communities. Based on this model, it is possible to evaluate the level of ecological risk associated with the execution of maintenance and regulatory works.     

Water-environmental risk assessment of the Beijing–Tianjin–Hebei collaborative development region in China

With the rapid development of social and economic conditions in the Beijing–Tianjin–Hebei (BTH) collaborative development region in China, the water-environmental problems gradually evolve into a regional problem. As an important tool of predicting and preventing these problems, water-environmental risk assessment (WERA) plays an increasingly important role in environment management. This study mainly targets the surface water environment and takes the BTH region as a study area in developing a water-environmental risk assessment index system based on the Driving force-Pressures-States-Impacts-Responses model. The weighting, risk, and zoning of each index are determined using multiple methods such as the Analytic Hierarchy Process, fuzzy comprehensive evaluation, and geographic information system technology. Further discussions are made to analyze the leading factors of high-risk units, the relationship between the risk level and social economy, and the uncertainty of WERA. Generally speaking, results show that the relative high-risk areas mainly distribute in Beijing, Tianjin, Shijiazhuang, and Tangshan, and the relative low-risk areas mainly distribute in Chengde and Zhangjiakou. The remaining parts of the region are at the middle-risk level. The results also show a positive correlation between the risk level and the social economy. This study gathered lots of data and carried out a number of calculation work, and is expected to improve the WERA methods and help managers set the priorities for local water-environmental management and make more effective decisions in the context of BTH collaborative development.     

Mechanisms of plant and microbial adaptation to heavy metals in plant–microbial systems

The data on heavy metal (HM) accumulation and detoxification by plants and bacteria in plant–microbial systems (PMS) are reviewed. Bacteria are shown to be the labile component of the system, responsible for a considerable amelioration of HM stress impact on plants and for improved PMS adaptation to heavy metals. Simulation of plant–microbial interactions under conditions of soil contamination by HM revealed the protective role of bacterial migration from the rhizoplane to the rhizosphere.     

Preliminary study on heavy metals contamination of soil using solid phase speciation and the influence on groundwater in Bozanta–Baia Mare Area,Romania

Abstract

A preliminary study on soil contamination with heavy metals and As based on solid phase speciation according to the Tessier scheme and the influence on groundwater in an area under anthropogenic influence (Bozanta-Baia Mare, Romania) was conducted. The partitioning of Al, As, Cd, Cu, Fe, Mn, Pb and Zn in five fractions is discussed in relation to soil characteristics, pH, organic matter content, mineralogical composition and distribution of the same elements in airborne particulate matter. The airborne particulate matter contains high quantities of As, Cd, Cu, Pb and Zn as exchangeable fraction. The sequential extraction carried out on soil samples revealed the main role of Fe-Mn oxides surface in the immobilization of metals. Organic matter has a specific role in complexation of Cu, Pb, As and Al, since high contents of these metals were recovered in the oxidizable fraction. Cadmium has a high selectivity for carbonate minerals. The amendment of soil with natural fertilizer increases the exchangeable fraction of metals with the highest toxicity. The available fraction for plants (exchangeable + carbonate-bound species) exceeded the alert values in soil, therefore the continuous monitoring of the area is necessary. The soil is unsuitable for agricultural use due to high contamination on surface with toxic elements resulted from anthropogenic activities. Groundwater is contaminated with very toxic elements (As, Cd and Pb) but also with Cu, Mn and Zn and is unsuitable as supply for drinking water.     

Diversity and spatial–temporal distribution of airborne fungi at the world culture heritage site Maijishan Grottoes in China

The deposition of the airborne microorganisms onto cultural heritage is associated closely with the subsequent biodeterioration. In this study, a systematic investigation was carried out to detect the seasonal variation and diversity of airborne fungal concentration at the World Cultural Heritage Site Maijishan Grottoes in western China. A bio-aerosol sampler was deployed to collect samples over four seasons in 2016. The culturable airborne fungi were isolated, purified and then identified with the extraction of genomic DNA, PCR amplification of ITS rRNA region, sequencing, and phylogenetic analysis. The concentrations of culturable fungi ranged from 216 to 1389 CFU/m³, which varied seasonally with significant differences among the sampling sites. Fifteen different fungal genera were confirmed, among them, Cladosporium was the most predominant fungal genus, followed by Penicillium. The fungal community structure and their relationship with environmental factors were also delineated. The spatial–temporal differences of airborne fungi at Maijishan Grottoes were mainly due to height, rainfall, relative humidity, and temperature. The dominant genera Cladosporium and Penicillium may pose potential threats to the ancient painted sculptures and murals, and monitoring of the airborne fungi at such a heritage site could provide supporting data for the pre-warning and control of fungal outbreaks inside the caves for better management.

     

Spatial patterns and associations of dominant woody species in desert–oasis ecotone of South Junggar Basin,NW China

Spatial patterns and associations of plant species are important for revealing how species interact with each other and with the environment, and hence have important implications for the understanding of species interaction and underlying ecological processes with apparent patterns in temperate desert vegetation. In this paper, the function g (r) was used to characterize the spatial patterns and associations of four dominant woody species in three 1-ha desert plant plots in the desert–oasis ecotone of South Junggar Basin, NW China. The complete spatial randomness null model showed four species exhibited significant aggregations at small scales (<20 m). Anabasis aphylla and Nitraria roborowskii, Haloxylon ammodendron and Reaumuria songarica were spatially positive associations at small scales with the independent null model, while A. aphylla and H. ammodendron, A. aphylla and R. songarica, R. songarica and N. roborowskii species pairs exhibited negative associations at small or moderate scales (20–60 m) in our study. The random labeling null model showed that dead standing plants of A. aphylla were largely determined by the combined effects of intra- and interspecific competition. In addition, the results also indicated that the two main factors of habitat heterogeneity and sandy desertification play important roles in determining spatial distribution patterns and associations of woody species in the desert–oasis ecotone of South Junggar Basin. Thus, the differences of species features in spatial patterns and associations should be paid more attention when planning afforestation and developing conservation strategies.     

The bioassessment of fish and macroinvertebrates in a Mediterranean–Atlantic climate: Habitat assessment and concordance between contrasting ecological samples

Human intervention and drought conditions in Mediterranean rivers may necessitate the collection of organisms from a different habitat type to that specified by the original bioassessment protocol; it is therefore critical to understand the consequences of adaptive sampling strategies in these lotic systems. In a survey of 31 streams (2nd–4th order) in northern Portugal we collected separate macroinvertebrate samples from running-water and standing-water habitats and fish samples from a delineated reach, inclusive of all habitat types. In addition to collecting habitat data specific to macroinvertebrates and fish we conducted a generalized River Habitat Survey (RHS) and derived scores designed to report habitat quality and habitat degradation. Ecological data were described in terms of taxonomic structure, functional organization and by biotic indices and interpreted in relation to habitat data, comparing samples within and between sites for concordance. Macroinvertebrates from respective habitats differed in their relationship with habitat variable with running-water samples more strongly related to substrate and water quality and standing-water samples more strongly reflecting habitat characteristics at the reach scale. Running- and standing-water samples from the same-site varied widely, indicating that substituting standing-water for running-water samples in macroinvertebrate-based bioassessment carries a high risk of misclassification. However, a consistent bias in index scores suggests that a habitat-adjusted interpretation of biotic indices could be employed to improve measurement precision. Variation in key parameters of the fish community corresponded to changes in water quality and habitat structure and to reach-scale features recorded by the RHS. Trends between macroinvertebrate and fish measurements indicated common patterns for oxygen/flow sensitive taxa and for trophic organization that were related to similar habitat preferences. Whilst macroinvertebrates demonstrated no relationship with derived scores of habitat quality, the fish-based Index of well-being (Iwb) was strongly related to the Habitat Modification Score. Overall these data indicate how different ecological samples can be used to focus on different aspects of habitat quality and are suggestive of strategies for both the collection and interpretation of ecological data that would improve assessment performance. This study emphasizes the need to adapt assessment methods not only to the species pool but also to the differences in the managed and natural habitat characteristics of these types of Mediterranean streams.     

Water resources stress assessment and risk early warning–a case of Hebei Province China

In most parts of China, water resources development and utilization has reached or exceeded the international warning level, especially in the northern arid and semi-arid regions, the serious water stress have aroused worldwide concerns. Many issues of water resources are closely and some inseparably associated with human activities. In this study, the water footprint (WF) and related indicators were applied as comprehensive indicators to assess real water use by humans from the consumption perspective. A Fuzzy Comprehensive Evaluation Model (FCE) was used for the evaluation in its role to assess water stress. And the index system of water stress assessment including four aspects, namely water supply and demand balance, socio-economy, agricultural production and ecological environment was established. Taking the case of Hebei province of China where there is serious conflict between water supply and demand, water stress assessment of all eleven administrative areas for the period 2000–2013 was analyzed. The findings showed that water stress was denoted by three levels, namely high water stress (red zone), general water stress (yellow zone) and low water stress (blue zone), which lays the foundation of the further research on water risk warning. According to the results of water stress assessment and the socio-economic development trends of Hebei, a Markov Chain Risk Warning model was built to describe the risk state of water system and to predict the transition probability of future states. This was intended to focus on the possibility that water stress levels might change into higher water stress level. The current study aims at extending earlier research by making a first step from water footprint estimation towards water stress assessment and providing reference for scientific management of water resources in arid and semi-arid regions.     

Changes in abundance and spatial distribution of geese molting near Teshekpuk Lake,Alaska: interspecific competition or ecological change?

Goose populations molting in the Teshekpuk Lake Special Area of the National Petroleum Reserve—Alaska have changed in size and distribution over the past 30 years. Black brant (Branta bernicla nigricans) are relatively stable in numbers but are shifting from large, inland lakes to salt marshes. Concurrently, populations of greater white-fronted geese (Anser albifrons frontalis) have increased seven fold. Populations of Canada geese (Branta canadensis and/or B. hutchinsii) are stable with little indication of distributional shifts. The lesser snow goose (Anser caerulescens caerulescens) population is proportionally small, but increasing rapidly. Coastline erosion of the Beaufort Sea has altered tundra habitats by allowing saltwater intrusion, which has resulted in shifts in composition of forage plant species. We propose two alternative hypotheses for the observed shift in black brant distribution. Ecological change may have altered optimal foraging habitats for molting birds, or alternatively, interspecific competition between black brant and greater white-fronted geese may be excluding black brant from preferred habitats. Regardless of the causative mechanism, the observed shifts in species distributions are an important consideration for future resource planning.     

The 1991–1992 rapid ecological assessment of Palau’s coral reefs

At the request of the Palau and US governments, a team of 30 scientists under the leadership of the Nature Conservancy completed a rapid ecological assessment (REA) of nearshore marine resources in Palau in 1992. The REA provided ecological input to Palau's ongoing master plan for economic development and identified 45 marine sites worthy of special protection. The REA relied on previous literature, 1992 aerial photography, interviews, and field observations. A combination of qualitative and quantitative techniques were used to assess stony corals, other reef invertebrates, reef and shore fishes, macroscopic algae, seagrasses, sea turtles and other marine organisms. The REA covered a variety of coral reef habitats including beaches, seagrass beds, fringing reefs, lagoons, passes, channels, reef holes, patch and pinnacle reefs, barrier reefs, atolls, submerged reefs, mangroves, and rock islands. Major stresses to Palau's coral reefs include sedimentation from soil erosion, overfishing, and damage from periodic storms and waves. Minor stresses include dredge-and fill activities, sewage pollution, anchor damage, tourism use, ship groundings, aquarium fish collecting, and minor crown-of-thorns (Acanthaster) infestations.     

Accumulation and translocation of heavy metals in the canola (Brassica napus L.)—soil system in Yangtze River Delta, China

Aims and methods

Concentrations of heavy metals such as Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in different tissues (seeds, roots and shoots) of the mature canola (Brassica napus L.) plants and in the associated rhizosphere soils from Yangtze River Delta (YRD) region of China, were determined to evaluate the heavy metals’ pollution in the soils and the canola seeds, and to discuss their accumulation and translocation characteristics in canola plants. At the same time, the phytoextraction potential of the canola plant for the above heavy metals was theoretically calculated and discussed on the basis of above measured data.

Results

The results showed that the concentration ranges of Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in the rhizosphere soils were 0.115–0.481, 3.40–20.5, 0.069–0.682, 9.92–27.4, 46.8–86.6, 17.7–253.3, 65.2–511.7 and 16.0–37.8?mg?kg^?1, respectively. The concentrations of Cu, Zn and Hg at some sampling sites exceeded the 2nd grade threshods of Chinese national environmental quality standard for soils. The potential ecological risk of heavy metals in the canola rhizosphere soils decreased in the order of Zhejiang > Shanghai > Jiangsu provinces. The concentration ranges of above heavy metals in the canola seeds were 0.032–0.067, 0.002–0.005, 0.001–0.005, 0.053–0.165, 0.191–0.855, 3.01–13.20, 34.82–96.95 and 0.343–2.86?mg?kg^?1, respectively, with Cu and Zn at some sampling sites exceeding the permissible concentrations in foods of China. Heavy metals’ concentrations in canola seeds didn’t increase with their increasing concentrations in the rhizosphere soils. The bioconcentration factors (BCFs) of most heavy metals in the canola seeds decreased with their increasing concentrations in the associated rhizosphere soils. The average BCFs of heavy metals decreased in the order of Zn (0.488)>Cd (0.241)>Cu (0.145)>Ni (0.038)>Hg (0.021)>Pb (0.005)=Cr (0.005)>As (0.000) in the canola seeds, Cd (1.550)>Cu (0.595)>Zn (0.422)>Hg (0.138)>Ni (0.085)>Pb (0.080)>As (0.035)>Cr (0.031) in the roots, and Cd (0.846)>Zn (0.242)>Cu (0.205)>Hg (0.159)>Ni (0.031)>Pb (0.025)>As (0.012)>Cr (0.007) in the shoots, respectively. The accumulation capacity for most of the above heavy metals in the mature canola tissues was root > shoot > seed, with the exceptions of seed > root > shoot for Zn and shoot > root > seed for Hg. Except Hg from root to shoot and Zn from root to seed, translocation factors (TFs) of above heavy metals were lower than 1.0.

Conclusions

The concentrations, BCFs and TFs of above heavy metals in the canola tissues indicated that the investigated canola plants did not meet the criteria of hyperaccumulators for the above heavy metals. The phytoextracton potential of the studied canola plants for the above heavy metals from the polluted soils was very limited. It would take 920, 3,170 and 3,762?years (assuming two crops per year) to reduce the initial soil Zn, Cu and Hg concentrations, respectively, from the most polluted soil concentrations to the 2nd grade thresholds of Chinese national environmental quality standard for soils.     

Process of exotrophy in fish. Effect of heavy metals—Zn and Cu

The review summarizes for the first time the information on effects of Zn and Cu on various links of the fish exotrophy process. It has been shown that essential metals, like the nonessential ones, can produce negative effects on various aspects of the food-procuring behavior, on sensor systems providing alimentary behavior, and on the digestive enzymes realizing digestion in fish of different ecological groups. A particular attention is paid to their different effects on proteinases functioning in stomach and intestine of various fish species as well as on hydrolase activities in their potential nutrition objects (fish and invertebrate animals). Several mechanisms are considered which allow decreasing the negative action of Zn and Cu on the process of fish exotrophy.