Heavy metal contamination of agricultural soils affected by mining activities around the Ganxi River in Chenzhou, Southern China

Effects of atmospheric deposition on heavy metal contamination in paddy field systems under different functional areas in ChangZhuTan, Hunan Province, China

In recent decades, the problem of heavy metal contamination in rice paddies has attracted widespread attention. However, most studies on heavy metal contamination in paddy fields are biased towards soil and/or rice plants, without taking atmospheric deposition into account. In this study, atmospheric deposition, paddy soil, and rice samples were collected from three functional areas (area proximity to factories, along the roadside, and suburban) in ChangZhuTan, Hunan Province. The pollution characterization, translocation, and health risk of heavy metals were reassessed. The findings revealed that Cd and As contamination in the study area's soils was more severe, with point exceedance rates reaching 70 % and 35.9 %, respectively. The highest concentrations of As, Ni, Cd, and Pb in atmospheric deposition were found along the roadside, with 1.42 μg/m2/day, 3.21 μg/m2/day, 0.34 μg/m2/day, and 8.28 μg/m2/day, respectively. In area proximity to factories, As and Ni in atmospheric deposition showed to be lowest, whereas Cd and Pb concentrations showed lowest in suburban areas. Furthermore, the accumulation of Cd and Pb in rice grains in regions proximity to factories was significantly higher than in other regions. The human health risk assessment indicated the health risk caused by rice intake in areas proximity to factories was the highest and requires attention, which was mainly due to Cd accumulation, with HQ value reached 3.19. Correlation tests indicate that atmospheric deposition has a positive effect on heavy metal enrichment in rice grains. Further Random Forest analysis revealed that the transport of heavy metals from atmospheric deposition to leaves and shells were important influencing factors for As, Cd, Ni and Mg accumulation in rice grain. Therefore, more attention should be paid to the effects of atmospheric deposition on the accumulation of heavy metals in paddy fields in order to maintain the production safety of crops.

Industrial hemp (Cannabis sativa L.) can utilize and remediate soil strongly contaminated with Cu, As, Cd, and Pb by phytoattenuation

Industrial hemp (Cannabis sativa L.) has great application potential in heavy metal-polluted soils owing to its safe non-food utilization. However, the fate of heavy metals in different varieties of hemp planted in strongly contaminated natural soils remains unknown. Here, we investigated the growth, heavy metal uptake, distribution, and transfer of nine hemp varieties in soils strongly contaminated with Cu, As, Cd, and Pb. Hemp variety and metal type were the main factors affecting the growth and heavy metal uptake in hemp. The nine hemp varieties grew well in the contaminated soils; however, differences existed among the varieties. The biomass of Z3 reached 5669.1 kg hm-1, whereas that of Yunma No. 1 was only 51.8 % of Z3. The plant height, stalk diameter, and stalk bark thickness of Z3 were greater than those of the other varieties, reaching 168 cm, 9.2 mm, and 0.56 mm, respectively. Permanova's analysis revealed that the total effects of Cu, As, Cd, and Pb on the growth of the nine hemp varieties reached 60 %, with leaf As having the greatest effect, reaching 16 %. , Even in strongly contaminated soils, the nine varieties showed poor Cu, As, Cd, and Pb uptake. Most of the Cu, As, Cd, and Pb were retained in the root, reaching 57.7-72.4, 47.6-64.7, 76.0-92.9, and 70.0-87.8 %, respectively. Overall, the Cu, As, Cd, and Pb uptake of Wanma No.1 was the highest among the nine varieties, whereas that of Guangxi Bama was the lowest. These results indicate that hemp is a viable alternative for phytoattenuation in soils contaminated with heavy metals because of its ability to tolerate and accumulate Cu, As, Cd, and Pb in its roots, and Guangxi Bama is superior to the other varieties considering the safe utilization of hemp products.

Heavy Metal(oid)s Contamination and Potential Ecological Risk Assessment in Agricultural Soils

Soil pollution caused by heavy metal(oid)s has generated great concern worldwide due to their toxicity, persistence, and bio-accumulation properties. To assess the baseline data, the heavy metal(oid)s, including manganese (Mn), iron (Fe), Cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), mercury (Hg), chromium (Cr), and cadmium (Cd), were evaluated in surface soil samples collected from the farmlands of Grand Forks County, North Dakota. Samples were digested via acid mixture and analyzed via inductively coupled plasma mass spectrometry (ICP MS) analysis to assess the levels, ecological risks, and possible sources. The heavy metal(oid) median levels exhibited the following decreasing trend: Fe > Mn > Zn > Ni > Cr > Cu > Pb > Co > As > Cd > Hg. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) suggested the main lithogenic source for the studied metal(oid)s. Metal(oid) levels in the current investigation, except Mn, are lower than most of the guideline values set by international agencies. The contamination factor (Cf), geo accumulation index (Igeo) and enrichment factor (EF) showed considerable contamination, moderate contamination, and significant enrichment, respectively, for As and Cd on median value basis. Ecological risk factor (Er) results exhibited low ecological risk for all studied metal(oid)s except Cd, which showed considerable ecological risk. The potential ecological risk index (PERI) levels indicated low ecological risk to considerable risk. Overall, the results indicate the accumulation of As and Cd in the study area. The high nutrients of the soils potentially affect their accumulation in crops and impact on consumers' health. This drives the impetus for continued environmental monitoring programs.

Risk assessment and strontium isotopic tracing of potentially toxic metals in creek sediments around a uranium mine, China

The contamination of creek sediments near industrially nuclear dominated site presents significant environmental challenges, particularly in identifying and quantifying potentially toxic metal (loid)s (PTMs). This study aims to measure the extent of contamination and apportion related sources for nine PTMs in alpine creek sediments near a typical uranium tailing dam from China, including strontium (Sr), rubidium (Rb), manganese (Mn), lithium (Li), nickel (Ni), copper (Cu), vanadium (V), cadmium (Cd), zinc (Zn), using multivariate statistical approach and Sr isotopic compositions. The results show varying degrees of contamination in the sediments for some PTMs, i.e., Sr (16.1-39.6 mg/kg), Rb (171-675 mg/kg), Mn (224-2520 mg/kg), Li (11.6-78.8 mg/kg), Cd (0.31-1.38 mg/kg), and Zn (37.1-176 mg/kg). Multivariate statistical analyses indicate that Sr, Rb, Li, and Mn originated from the uranium tailing dam, while Cd and Zn were associated with abandoned agricultural activities, and Ni, Cu, and V were primarily linked to natural bedrock weathering. The Sr isotope fingerprint technique further suggests that 48.22-73.84% of Sr and associated PTMs in the sediments potentially derived from the uranium tailing dam. The combined use of multivariate statistical analysis and Sr isotopic fingerprint technique in alpine creek sediments enables more reliable insights into PTMs-induced pollution scenarios. The findings also offer unique perspectives for understanding and managing aqueous environments impacted by nuclear activities.

Characteristics of soil contamination by potentially toxic elements in mine areas of Mongolia

Soil contamination by potentially toxic elements (PTEs), such as metal(loid)s, in mining areas was characterized on a nationwide scale in Mongolia to understand the contamination status throughout the country, according to mine types. Positive matrix factorization (PMF) analysis exhibited better classification and explanation of soil contamination according to ore types compared to conventional statistical analysis methods such as principal component analysis (PCA) and hierarchical cluster analysis (HCA). The results of PMF analysis for metal(loid) contents in 1425 topsoil samples collected from 272 mines illuminated four Factors, which primarily contributed to As (Factor 1), Pb, Zn, and Cd (Factor 2), Ni (Factor 3), and Cu and Cd (Factor 4) contaminations, respectively. In hard-rock gold mines, As was enriched and the contribution of Factor 1 was high (31.2%) due to the affinity between As and Au. In placer gold mines, the contribution of Factor 3 (41.8%) was high due to the affinity between Ni and weathering-resistant heavy minerals. For base metal, fluorite, and coal mines, contributions of Factors 2 (32.1-50.9%) and 4 (17.7-33.6%) were high owing to sulfides containing Pb-Zn-d and Cu. These impacts of mine types were altered by local geology (e.g., skarn). Meanwhile, Hg amalgamation contributed to Hg contamination in a few hard-rock gold mines. These results suggest that soil contaminants in mining areas are mainly affected by the type of deposits with geochemical affinities, region-specific ore characteristics, and artificial processing. Understanding these effects will help establish national strategies for countermeasures, such as soil rehabilitation in mining areas.

Trace metal contamination status in soils of the abandoned gold mining district of Bindiba (East Cameroon): Pollution indices assessment, multivariate analysis and; geostatistical approach

In this study, contamination by trace metals (TMs) such as Cr, Ni, Cu, As, Pb and Sb in the soils of the Bindiba mining district was assessed. This study aims to reveal the current status of the soil quality of the abandoned gold mining district of Bindiba and provide a scientific basis for its future remediation and overall management. 89 soil samples were systematically collected and characterized in order to determine the concentration of TMs (Cr, Ni, Cu, As, Pb and Sb). To assess the degree of metallic contamination, pollution indices were employed. Both multivariate statistical analysis (MSA) and geostatistical modelling (GM) were used to identify the potential sources of TMs elements and to determine the values of the modified contamination degree (mCd), the Nemerow Pollution Index (NPI) and the potential ecological risk index (RI) at un-sampled points. The results of trace metals (TMEs) characterization showed that the concentration of Cr, Ni, Cu, As, Pb and Sb ranged from 22.15-442.44 mg/kg, 9.25-360.37 mg/kg, 1.28-320.86 mg/kg, 0-46.58 mg/kg, 0-53.27 mg/kg and 0-6.33 mg/kg, respectively. The mean concentration of Cr, Cu and Ni exceeds the continental geochemical background values. The Enrichment Factor (EF) assessment indicates two categories of enrichment: moderately to extremely enrichment for Cr, Ni, and Cu and deficiency to minimal enrichment of Pb, As and Sb. Multivariate statistical analysis shows weak linear correlations between the studied heavy metals and suggests that these metals could not come from the same origins. The geostatistical modelling based on the values of mCd, NI and RI suggests a potential high pollution risk existed in the study area. The mCd, NPI and RI interpolation maps showed that the Northern part of the gold mining district was characterized by a high degree of contamination, heavy pollution, and considerable ecological risk. The dispersion of TMs in soils could mainly be attributed to anthropogenic activities and natural phenomena (chemical weathering or erosion). Appropriate measures should be taken to manage and remediate the TMs pollution in this abandoned gold mining district in order to reduce its negative effects on the environment and health of the local population.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40201-023-00849-y.

Potentially Toxic Element Contamination in Soils Affected by the Antimony Mine Spill in Northwest China

This study provides a comprehensive assessment of the potential ecological and health risks in the area of the antimony mine spill in Longnan, Northwest China, and identifies the sources of potentially toxic elements (PTEs) in the soil as a result of the spill. The geo-accumulation index and enrichment factor show that the study area is highly contaminated with arsenic (As), mercury (Hg) and antimony (Sb). The ecological risk index in the tailings spill area ranged from 320.43 to 5820.46 (mean: 1489.82), indicating a very-high potential ecological risk, with mean values of 104.86, 1118.87 and 248.84 for As, Hg and Sb, respectively. The multivariate statistical analysis suggested that Sb and Hg come from tailings leakage, while copper (Cu), nickel (Ni) and zinc (Zn) may be imported from natural sources, and As and lead (Pb) originate from agricultural activities. In addition As and Sb pose a high health risk. With the exception of the non-carcinogenic risk in adults, all other risks are significantly exceeded in other populations, with children being the highest-risk group. These findings provide important quantitative information for the assessment and management of PTE contamination in other tailings spill areas.

Effect of Soil Washing with an Amino-Acid-Derived Ionic Liquid on the Properties of Cd-Contaminated Paddy Soil

To reduce contamination levels in Cd-contaminated paddy soil while retaining soil characteristics, we have studied the Cd-removing ability of 15 different amino acid-based ionic liquids, which are considered to be green solvents, as soil washing agents and their impact on soil. The results indicated that the glycine hydrochloride ([Gly][Cl]) removed the most Cd, and under optimized conditions could remove 82.2% of the total Cd. Encouragingly, the morphology of the soil had not been significantly changed by the washing process. After the soil was rinsed twice with water and the pH was adjusted to 6.2 by adding Ca(OH)₂, the germination index of the rice increased by 7.5%. The growth of the rice was also stimulated, with lengths and weights of the rice plants increasing by 56% and 32%, respectively, after two weeks. These experiments demonstrate that amino-acid-derived ionic liquids can be promising soil-washing agents of Cd-contaminated paddy soil.

A review and critical assessment of sedimentary metal indices used in determining the magnitude of anthropogenic change in coastal environments

The current critical review examines the application of 11 frequently used sedimentary metal indices in their ability to accurately assess the magnitude of human-induced change (enrichment) in the highly vulnerable and intensely developed coastal environment. The plethora and rapidly increasing number of sedimentary metal indices should, if not derived for special purposes, produce a consistent assessment on the basis that they use the same suite of metals and concentrations. Inconsistent numerical results produced by different index formulations should, when combined with their associated classification scheme, produce a common assessment of environmental condition. However, such a consistent outcome is seldom observed. Significant differences in assessment results are partly due to the historical evolution of indices and to the extraordinary diversity of background and reference values and materials being applied to account for pre-anthropogenic metal levels and confounding due to variable sediment characteristics. Size-normalised sample and background metal data used in the mCd and MEQ indices do not require reference values to account for textural variability and provide a quasi-direct measurement of enrichment with minimal computation (simple division). These priority indices should be combined into a single index (Enrichment Quotient, EQ). Results produced by the EF index were strongly correlated to mCd and MEQ and provide a similar classification and is recommended if normalised data are unavailable. Other indices assessed (MPI, PI, mPI, SEF, Igeo, PLI and Cf, original and current) provided a range of results, which either over- or under-estimated enrichment. The confusion concerning the choice and application of background and reference values in the assessment process is reviewed and their use in local and global assessment is clarified. Single- and combined-metal evaluations are recommended to provide detailed, local and more comprehensive assessments, respectively.

Genetic variation and molecular characterization of Zygophyllum coccineum L. ecotypes of the iron mining area of El-Wahat El-Bahariya in Egypt

Remediation and mitigation processes can recover the ecosystems affected by mining operations. Zygophyllum coccineum L. is a native indigenous xerophyte that grows in Egypt's Western Desert, particularly around the iron mining ore deposits, and accumulates high rates of potentially toxic elements (PTEs) in its succulent leaves. The present study evaluated the genetic variation and molecular responses of Z. coccineum to heavy metal stressful conditions in three sites. Results revealed that Z. coccineum bioaccumulation capacity was greater than unity and varied amongst the three locations. In response to heavy metal toxicity, Z. coccineum plants boosted their antioxidative enzymes activity and glutathione levels as a tolerance strategy. Anatomically, a compact epidermis, a thick spongy mesophyll with water storage cells, and a thicker vascular system were observed. Protein electrophoretic analysis yielded 20 fragments with a polymorphism rate of 85%. The antioxidant genes (CAT: catalase, POD: peroxidase and GST: polyphenol oxidase) showed greater levels of expression. In addition, DNA-based molecular genetic diversity analyses using Start Codon Targeted (SCoT) and Inter Simple Sequence Repeat (ISSR) markers yielded 54 amplified fragments (i.e. 24 monomorphic and 30 polymorphic), with 12 unique fragments and a polymorphism rate of 55.5%. The greatest PIC values were recorded for SCoT-6 (0.36) and for both of the 14 A and 44 B ISSR primers (0.25). Diversity index (DI) of all SCoT and ISSR amplified primers was 0.23. The present findings reveal the distinct heavy metal's adaption attributes of Z. coccineum, indicating its improved survival in severely arid mining environments.

Source appointment of potentially toxic elements (PTEs) at an abandoned realgar mine: Combination of multivariate statistical analysis and three common receptor models

Identifying pollution sources and quantifying their contributions are of great importance for proposing management and control strategies of potentially toxic elements (PTEs) in soil. In this study, multivariate statistical analysis and receptor models were combined to identify potential pollution sources and apportion their contributions at an abandoned realgar mine. Principal component analysis (PCA) result shows that three factors are responsible for PTEs, which is also supported by cluster analysis (CA). Correlation analysis and spatial analysis also show that the heavy metals from the same pollution source are of higher correlation coefficients and similar spatial distribution. Three receptor models were combined to apportion contributions of pollution sources. Three pollution sources were detected by absolute principal component analysis-multiple linear regression (APCA-MLR). In contrast, four sources were identified by positive matrix factorization (PMF) and UNMIX. Soil parent material was heavily loaded on Cr, Cu, Ni and Zn, occupying the largest average contribution (30%-43%). Cadmium was mainly derived from agricultural activities with contribution higher than 60%. Arsenic accumulation was mainly associated with mining and smelting activity with contribution higher than 80%. PMF and UNMIX models showed that more than half of Pb concentrations were influenced by industrial activities. Comparatively speaking, APCA-MLR was a well-performing model for all PTEs even though it only detected three pollution sources. The study showed that it was a good choice to apply multiple receptor models in order to achieve more reliable and objective conclusions of source appointment.

Land Use Changes Influence the Soil Enzymatic Activity and Nutrient Status in the Polluted Taojia River Basin in Sub-Tropical China

Different land use practices may improve soil quality or lead to soil deterioration. Recently, environmental problems, such as heavy pollution and soil erosion, have led to serious land degradation in the Taojia River basin. In this study, we explored the soil fertility characteristics (mechanical composition; pH; soil organic matter (SOM); soil total nitrogen (TN); and the activity of four enzymes, i.e., urease, hydrogen peroxide, alkaline phosphatase, and sucrose enzymes) under different types of land use in the Taojia River basin. Soil samples were taken from 0-10 cm, 10-20 cm, and 20-40 cm depths from four different land use types that were widely used in the Taojia river basin, including cultivated land, vegetable fields, woodlands, and wastelands. The results showed that the soil enzyme activity and the constituents of the soil were closely related and significantly affected each other (p < 0.05). Woodland soil exhibited the highest content of SOM in all soil depths. Soil total nitrogen mainly depended on the accumulation of biomass and the decomposition intensity of organic matter, so the changes in TN followed the trends of the changes in SOM. Woodland soil showed an improved mechanical composition. We were also able to observe an increased clay content in woodland soil. Woodland soil also exhibited the reversal of soil desertification and an increase in nutrient/water retention capacity. Therefore, an increase in woodland areas would be an appropriate goal in terms of land use in order to improve the eco-environmental quality of the Taojia River basin.

Effect of ferrous sulfate modified sludge biochar on the mobility, speciation, fractionation and bioaccumulation of vanadium in contaminated soil from a mining area

In contaminated soil, pristine biochar has poor applicability for immobilizing vanadium (V), which mainly exists as oxyanions in soil. To elucidate the immobilization potential and biotic/abiotic stabilizing mechanisms of a ferrous sulfate (FS)-modified sludge biochar in a V-contaminated soil from a mining area, we investigated the effects of biochar addition on the soil characteristics, growth of alfalfa, leachability, bioavailability, speciation, and fractionation of V, and changes in the microbial community structure and metabolic response. The results showed that the water extractable, acid-soluble (F1), and pentavalent fractions of V in soil decreased by up to 99 %, 95 %, and 55 %, respectively, whereas the reducible and (F2) oxidizable (F3) fractions increased by up to 45 % and 76 %, respectively. After the soil was treated with the FS-modified biochar for 90 d, the V concentration in the roots and shoots of alfalfa (Medicago sativa L.) decreased by up to 81.5 % and 96 %, respectively. The changes in the speciation, fractionation, and efficient immobilization of V in the studied soil were due to the combined effects of the biochar-induced decrease in soil pH, adsorption and precipitation by elevated iron concentrations, reduction and complexation due to an increase in the organic matter content, and microbial reduction by Proteobacteria.

Characterization of physicochemical parameters and bioavailable heavy metals and their interactions with microbial community in arsenic-contaminated soils and sediments

Mobility and toxicity of heavy metal contamination in the environment are highly dependent on its bioavailability. Most of previous studies focused on total heavy metal contents and their influence on microbial community in soils and sediments. Little were concerned about bioavailable fractions. In the current study, soil and sediment samples were collected near an abandoned realgar mine in Shimen County, China. Bioavailable heavy metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sb, and Pb in the samples were extracted using three-step sequential extraction method. Interactions among physicochemical parameters, total and bioavailable heavy metals, and microbial community in the collected samples were investigated. The study area has been severely contaminated by As with a concentration up to 2158 mg·kg-1 detected. The result of principal component analysis showed that the abundance of operational taxonomic units (OTUs) in the soils were obviously different from those in the sediments. In the soil samples, pH made a dominant contribution on the OTU abundance of microbial community. Correlation analyses revealed that the alpha diversity indices and microbial taxon were most correlated with bioavailable fractions of heavy metals in all the samples. That means bioavailable heavy metals rather than total heavy metals or physicochemical parameters played a more important role on richness and diversity of microbial community. Little connections were observed between microbial community and As no matter total concentration or bioavailable fraction. However, bioavailable Fe and Mn were recognized as the major driving force shaping the taxonomic structure of microbial community due to their relatively high concentrations and high affinity to other heavy metal contamination in soils and sediments.

Tissue-specific distribution and bioaccumulation pattern of trace metals in fish species from the heavily sediment-laden Yellow River, China

The Yellow River is one of the largest contributors to the global riverine sediment flux from the land to the ocean. Tissue-specific bioaccumulation of trace metals in fish from heavily sediment-laden rivers remains unclear to date. The concentrations and distributions of trace metals in water, suspended matters, sediments, and various fish tissues were investigated in the mainstem of the Yellow River were investigated. The concentrations of most metals in abiotic media were high in the Gan-Ning-Meng of upstream and downstream segments, and were highest in fine-sized suspended matters. The highest concentrations of most metals were in the gill and liver, followed by the gonad, and lowest in the muscle, and there were a significant overall differences among the tissues. The concentrations of metals in some tissues (e.g., muscle and gill) significantly differed among regions and feeding habits. The highest values of the bioaccumulation factor for suspended matters (BF_SPM) were observed in the midstream region (e.g., reaching to 19.0 for Se in the liver). This was determined by metal type and tissue specificity, food composition, and concentration of metals in abiotic media. The results highlight the significance of suspended matters for the distribution of trace metals in abiotic and biotic media.

Bioaccessibility of Cd and its Correlation with Divalent Mineral Nutrients in Locally Grown Rice from Two Provinces in China

Rice and rice products are the main sources of Cd contamination in humans. The total and bioaccessible concentrations of Cd and three divalent nutrients, Mn, Cu, and Zn, in locally grown rice grains from Hunan and Guangdong Provinces in China were investigated. An in vitro physiologically based extraction test method was introduced to evaluate the bioaccessibility of the target metals in the rice grains. The mean concentrations of Cd in the rice grains were 0.245 mg/kg and 0.235 mg/kg from Hunan and Guangdong Provinces, respectively. Large variations were observed in the Cd concentrations, indicating a heterogeneous distribution of Cd contamination throughout the study areas. The bioaccessibility of Cd, Mn, and Zn in the gastrointestinal fractions was significantly lower than that in the gastric fractions. In contrast, the bioaccessibility of Cu at the intestinal phase was detected in the rice grains from both provinces. The correlation analysis showed significant relationships between total Cd concentrations and bioaccessible Cd fractions, indicating that higher total Cd in rice grains always resulted in higher bioaccessible Cd. Consistent correlations in the rice grains were observed between Zn and Mn. However, a lack of correlation was found between Cd and Zn in the current study. Risk assessment according to bioaccessible Cd would significantly reduce the exposure risk to Cd from rice consumption.

Interactions among heavy metal bioaccessibility, soil properties and microbial community in phyto-remediated soils nearby an abandoned realgar mine

Soil samples were collected from a representative arsenic (As) contaminated region under phytoremediation of hyperaccumulation plants. Relative abundance and diversity of microbial communities in the soil samples were characterized via 16S rRNA genes sequencing. At the phylum level, Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes and Firmicutes shows the highest abundance, accounting for more than 90 % of the classified sequences in the soil samples. Physicochemical parameters including pH, total organic carbon (TOC), cation exchange capacity (CEC), and electrical conductivity (EC), and heavy metal concentrations including total and bioaccessible contents in the soil samples were determined to investigate potential relationships between the microbial communities and the environmental factors. Principal component analysis (PCA) based on the operational taxonomic units (OTUs) matrix revealed distinct separation among the samples. The soil pH was confirmed as the dominant force to discriminate the soil samples with similar land use type and heavy metal contamination. There was little relevance between the total concentrations of heavy metals and the microbial communities. However, the bioaccessible concentrations of heavy metals were associated with the physicochemical parameters and relative abundances of bacterial genera according to correlation analyses. Although the soil samples were considerably contaminated by As, the abundances of bacterial phyla linked with As were lower than 1.0 % in most of the soil samples. The results indicated that the abundances of microbial communities in the soils were the consequence of concerted effects from all the environmental factors.

Potential Loss of Toxic Elements from Slope Arable Soil Erosion into Watershed in Southwest China: Effect of Spatial Distribution and Land-Uses

The watershed-scale distribution and loss of potentially toxic elements (PTEs) through soil erosion from slope lands to a watershed has not yet been systematically studied, especially in small mountain watersheds with high geological background PTEs in Southwest China. In this study, the spatial distribution, loss intensities and ecological risks of 12 PTEs were investigated in 101 soil samples from four types of land use in a typical watershed, Guizhou Province. Moreover, in order to avoid over- or underestimation of the contamination level in such specific geologies with significant variability in natural PTE distribution, the local background values (local BVs) were calculated by statistical methods. The dry arable land had the highest loss intensity of PTEs and was the largest contributor of PTEs (more than 80%) in the watershed, even though it covers a much smaller area compared to the forest land. The loss of Cd, As, Sb, and Hg from slope arable lands into the watershed leads to a relatively high potential ecological risk. The study suggested that both PTEs content with different types of land-uses and intensities of soil loss are of great importance for PTEs’ risk assessment in the small watershed within a high geological background region. Furthermore, in order to reduce the loss of PTEs in soil, the management of agricultural activities in arable land, especially the slope arable land, is necessary.

Subtotal content and geochemical fractionation of potential toxic elements in agricultural soils from Mocorito River basin in NW Mexico: environmental and health implications

Agricultural soils were collected from Mocorito river basin, to determine potentially toxic elements (PTEs) subtotal concentrations and geochemical fractionation, and evaluate their environmental and health risks. All sites showed low As and Cr concentrations. Subtotal concentrations (mg/kg) ranged between 6.8 and 25.6 for As, 1.9 and 2.5 for Cd and 22.5 and 55.1 for Cr. These values were classified as moderately contaminated for As, while a considerable contamination was presented for Cd and Cr. Geochemical partitioning revealed that PTEs are strongly linked with residual phase. Arsenic was associated with amorphous Fe-oxyhydroxides. Ecotoxicological indices showed from low (As and Cr) to considerable (Cd) potential ecological risk factors; potential non-carcinogenic risks by As, Cd and Cr, and potential carcinogenic risks by As and Cr. Lithogenic and anthropogenic sources were identified. Arsenic and Cr showed lithogenic influence, while Cd increased, caused by nearby activities, representing an environmental and health risk.

Multivariate correlation analysis of bio-accumulation with soil properties and potential health risks of cadmium and lead in rice seeds and cabbage in pollution zones, China

A total of 475 representative cultivated land and 435 crop samples from 11 provinces of China were collected, and lead and cadmium in 6 polluted areas by wastewater irrigation and metallurgy industry were analyzed. Rice is the major cash crop and staple food of Chinese residents. Cabbage is also a common food in Chinese daily life. Pollution levels and spatial distribution of soil, rice, and cabbage samples were illustrated on the map. In individual or multiple areas, the multivariate correlation of heavy metal's (cadmium and lead) bio-accumulation in two kinds of plants (rice seed and cabbage) and soil properties (pH, cation exchange capacity, and organic matter) was also investigated. Spearman correlation analysis showed that soil pH values and organic matter (OM) had significant effects on the uptake of Cd and Pb in rice seed: the correlation between lg Cd BCF and pH values is -0.148* (p = 0.026), and the correlation between lg Pb BCF and pH values is -0.339** (p = 0.000). The cation exchange capacity (CEC) and pH significantly impact the Cd and Pb uptake in cabbage: the correlation between lg Cd EF and pH values is -0.199* (p = 0.040), and the correlation between lg Pb EF and pH values is -0.203** (p = 0.009). The Cd and Pb bio-concentration factor BCFs of rice and cabbage decreased with the increase of pH, CEC, and OM, except that Pb BCFs increased with the increase of OM in certain areas. The BCF of Cd varied positively from Pb in cabbage, but inversely with Pb in rice significantly at the 0.01 level (two-tailed Spearman correlation analysis). For the first time, the health quotient (HQ) of Cd and Pb in different regions was also calculated and illustrated on the map. In the soil samples of different areas, average HQ values of Cd and Pb in maturity varied from 0.0003-0.0023 to 0.0051-0.0460; average HQ values of immaturity were 0.0011-0.0103 and 0.0222-0.2014. In the rice samples of different areas, average HQ values of Cd and Pb in maturity varied from 0.305-1.360 to 0.027-0.321; average HQ values of immaturity were 0.601-2.678 and 0.053-0.633. Average HQ values orders of magnitude in the cabbage samples of different areas are the same as that of rice samples, and it is 2-4 orders higher than those in soil. Average HQ values of Cd and Pb in maturity varied from 0.152-1.354 to 0.006-0.506; average HQ values of immaturity were 0.510-4.192 and 0.022-0.207. The total HQ values ingested by children were all higher than those in adults. After investigation, it was found that the total HQ value of mature plants was also higher than that of immature plants. The results of this study would be of great help to future soil remediation with similar types.

Health risk assessment of trace metals in selected food crops at Abuakwa South Municipal, Ghana

Trace metals contamination has recently been a major issue due to its damaging effects on public health and environmental receptors. This study focussed on the health risk assessment of trace metals (As, Pb, Cr, and Ni) associated with the direct intake of some selected food crops (namely cocoyam and plantain) at Abuakwa South Municipal, Ghana. The food crops and soil samples were selected randomly from three reclaimed mined sites and one non-mining site in the study area. Results from the trace metal concentration analyses in the soil samples showed that As, Cr, and Ni were above the control. The daily intake of metals (DIM), target hazard quotient (THQ), and carcinogenic risk (CR) assessments of health risks accompanied by the continuous ingestion of the selected food crops polluted through these trace metals were evaluated. 0.23 mg/kg and 0.05 mg/kg, 0.11 mg/kg and 0.02 mg/kg, 0.78 mg/kg and 0.65 mg/kg, and 0.23 mg/kg and 0.09 mg/kg were recorded for As, Cr, Ni, and Pb in that order in the cocoyam and plantain, respectively. The As and Pb concentrations in the food crops were above the WHO recommended limits. This implies that individuals within the vicinity are exposed to high levels of As and Pb through food intake which could result in varying health implications. The DIM and THQ for the studied trace metals were below their permissible limits suggesting that there is a tolerable non-carcinogenic adverse health risk level for adults and children within the studied area. In addition, the lifetime probability of contracting cancer by ingesting Ni, Pb, and Cr in plantain grown in the study area is high. It is recommended that regular monitoring of these trace metals in food crops be carried out in preventing their excessive accumulation.

Evaluation of trace elements pollution in deposited dust on residential areas and agricultural lands around Pb/Zn mineral areas using modified pollution indices

Dust deposited on residential and agricultural lands can have serious consequences for the ecosystem when toxic trace elements are present. This study aimed to assess the ecological risk of the trace elements found in the deposited dust around the Mehdi Abad Pb/Zn mine, Yazd, Iran, using several modified pollution indices. The dust samples were collected by the grid method and a Marble Dust Collector (MDCO) sampler to evaluate the concentration of thirty trace elements: nickel (Ni), lead (Pb), barium (Ba), beryllium (Be), chromium (Cr), copper (Cu), dysprosium (Dy), lanthanum (La), lithium (Li), niobium (Nb), tin (Sn), neodymium (Nd), praseodymium (Pr), rubidium (Rb), Ferrum (Fe), sulfur (S), selenium (Se), strontium (Sr), tantalum (Ta), terbium (Tb), zirconium (Zr), tellurium (Te), thorium (Th), titanium (Ti), uranium (U), vanadium (V), yttrium (Y), ytterbium (Yb), thulium (Tm), and cobalt (Co). This study employed multivariate statistical techniques, including Hierarchical cluster analysis (HCA) and the IDW interpolation technique, as well as modified pollution indices such as Enrichment Factor (EF), Modified Pollution Index (MPI), Modified Potential Ecological Risk Index (MRI), and Modified Hazard Quotient (mHQ). All the statistical data analyses were performed via SPSS Statistics, version 22.00. The HCA results showed that all of these trace elements, except Fe, form a group and had similar behavior. The average levels of all elements in the dust samples except for Cr, S, Sr, Ta, Tb, and Te exceeded the background value. The results confirmed that both anthropogenic activities and natural factors were responsible for the trace elements found in the dust. The average EF value for Pb (43.26) indicated its extremely high enrichment in the study area. The MPI, mHQ, and MRI results showed that 33%, 100%, and 33.33% of the dust samples were in the heavily polluted, extreme severity, and high risk categories, respectively. The IDW analysis results revealed that the highest value of the MRI and mHQ indices was in agricultural lands and residential areas; the predominant wind direction also played a role in transferring the elements from the mine to these areas. In general, the results indicated that mining activities increased the ecological risk in Mehdi Abad due to the presence of trace elements, especially Pb.

Spatial distribution and risk assessment of agricultural soil pollution by hazardous elements in a transboundary river basin

The present study aimed to evaluate the sources of pollution and the potential human and ecological risks of hazardous elements (HEs) in 40 hotspot sites of the agricultural soil around the Arvand River, Iran. The mean concentrations of As, Cd, Co, Cr, Ni, Pb, Zn, and Hg were measured to be 7.2, 0.8, 14.0, 67.9, 69.5, 63.0, 296, and 0.66 (mg kg^-1), respectively. With the exception of Ni, the mean concentrations of all the elements were found to be higher than those in the background. The spatial distribution of HEs in the study area indicated an increasing trend of contamination from the north to the south. Pb, Zn, and Hg were the most enriched elements, resulting in a high pollution load. Moreover, the agricultural soil of the study area was threatened by a very high ecological risk due to the contribution of Hg, Cd, and Pb. Multivariate statistical analyses determined that the pollution sources are specified by the oil refinery emissions and effluents, irrigation with polluted water, fertilizers, dust storms, and airport emissions. The carcinogenic risk of HEs in both adults and children revealed an acceptable level; however, children faced a great chance of non-carcinogenic risk. The results provide a scientific basis for monitoring HEs and managing health risks via effective methods in the agricultural areas of the Arvand River basin.

Ecological risk assessment of heavy metal-contaminated soils of selected villages in Zamfara State, Nigeria

The incidence of heavy metal contamination in Zamfara State, northern Nigeria, due to artisanal mining in some villages has resulted in the pollution of a vast area of land and water. This study evaluated the extent of environmental risks caused by heavy metals. It involved five (5) villages (Bagega, Dareta, Sunke, Tunga, and Abare) where mining activities were taking place and Anka town with no record of mining activities served as control. In each of the five villages, three sites (3) were identified as a mining site, processing site, and village making a total of sixteen (16) sites. Bulked soil samples were collected in triplicate and analyzed for iron, lead, cadmium, chromium, zinc, and nickel using flame atomic absorption spectrophotometry. Measured concentrations of the heavy metals in soils were then used to calculate the pollution and ecological risk pose by heavy metals. Their concentrations were in the order Fe > Pb > Cr > Zn > Cd > Ni, with Pb and Cd having a concentration higher than permissible levels for soils and accounted for 98.64% of the total potential ecological risk. Also, all the different pollution indices examined showed that all the sites were polluted with Cd, and all the processing sites were polluted with Pb. This reveals that processing sites pose more risk to heavy metal contamination. Correlation analysis showed a highly significant (p < 0.001) positive correlation between Pb and Zn, Cr and Ni, and a significant (p < 0.01) positive correlation between Fe and Pb, Zn and Cr. The principal component analysis suggested that Pb, Zn, Cr, and Ni likely originated from the same source, i.e., mining activities, and Fe and Cd originated from the abundant parent material in the study area.

Bioremediation effect of pomegranate peel on subchronic mercury immunotoxicity on African catfish (Clarias gariepinus)

The primary aim of the present study is to evaluate the highest concentrations of heavy metals (HMs) in Nile catfish (Clarias gariepinus, C. gariepinus) and water samples, as well as to investigate the efficiency of pomegranate peels (PPs) (supplemented either through water or diet) in enhancing fish immunity and counteracting the toxicity of high concentrations of HMs. Water and C. gariepinus samples were collected from two private fish farms in Al Sharkia Governorate. Mercury (Hg) showed the highest concentration (0.13 ppm). The adsorption capacity of PP was evaluated by testing different concentrations, 0.3, 0.6, 0.9, 1.2, and 1.5 g L^-1, wherein 1.5 g L^-1 revealed the highest Hg adsorption efficiency. The results indicated that Hg concentration was decreased with increased PP concentration until 72 h. In a trial that lasted for 60 days, 240 C. gariepinus (75.12 ± 3.12 g) were randomly divided into eight equal groups with three replicates per group. The first group (CT) served as the negative control (fish fed on a basal diet). The second group (PPW) was fed on a basal diet and supplemented with 0.3 g L^-1 of PP via water. The third (PPD1) and fourth (PPD2) groups received basal diets enriched with 1 and 2 g PP powder/kg diet. respectively. The fifth group (Hg) served as the positive control that was fed on a basal diet and exposed to 0.13 ppm of Hg. The sixth (Hg + PPW), seventh (Hg + PPD1), and eighth (Hg + PPD2) groups were exposed to 0.13 ppm of Hg and received the same type of treatment as in second, third, and fourth groups. Hg exposure significantly elevated aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, and creatinine levels, as well as oxidative stress biomarkers, including reduced glutathione (GSH) and malondialdehyde (MDA). Pomegranate supplementation through diet elevated the levels of red blood cells (RBCs), hemoglobin (Hb), packed cell volume (PCV), lysozyme, and anti-protease activity. Moreover, PP supplementation through water revealed minimum urea and creatinine levels, and the highest nitric oxide level. Moreover, Hg residue level in fish muscles noticeably decreased in the PP-treated groups. These results demonstrated the efficiency of PP supplementation (either through water or diet) in enhancing fish immunity and counteracting subchronic Hg toxicity.

Application of inorganic passivators reduced Cd contents in brown rice in oilseed rape-rice rotation under Cd contaminated soil

Immobilization of heavy metals by the application of chemical amendments is an eco-friendly, economical and effective method to remediate cadmium (Cd) -contaminated soils. Field experiments were conducted during 2016-2018 following oilseed rape-rice rotation with the application of inorganic passivators i.e., slaked lime (CaOH₂>95%) and sepiolite (SiO₂>50%, MgO>20%). The experimental treatments were comprised of: rice planting in winter fallow and without passivator (F-PA0); fallow with slaked lime (F-PA1); fallow with sepiolite (F-PA2); oilseed rape-rice rotation without passivator (R-PA0); rotation with slaked lime (R-PA1); and rotation with sepiolite (R-PA2). The slaked lime and sepiolite were applied after the harvest of rape at 2000 and 5000 kg ha^-1, respectively. Results revealed that the Cd contents were reduced by 47.44-49.03% in brown rice for F-PA2 and 9.54-42.66% in soil for R-PA2. The superoxide dismutase (SOD) activity was decreased by 10.65-17.98%, the malondialdehyde (MDA) contents were reduced by 28.57% whereas the proline content was decreased by 32.61% under R-PA2. In addition, the filled grain percentage was improved by 6.87% (F-PA2) and 3.70% (R-PA1), respectively. Overall, rice sown after oilseed rape gave better yields than sown after fallow fields while application of slaked lime and sepiolite as passivator could be a potential management option to grow crops in metal polluted soils.

Associations between essential metals exposure and metabolic syndrome (MetS): Exploring the mediating role of systemic inflammation in a general Chinese population

BACKGROUND

Essential metals have been reported to be associated with metabolic diseases. However, the relationships between essential metals exposure and Metabolic Syndrome (MetS) is still uncertain, and the underlying mechanisms of the association remain unclear.

OBJECTIVES

To investigate the associations of urinary essential metals with MetS prevalence; and further to explore potential role of systemic inflammation biomarker, C-reactive protein (CRP), in relationships between essential metals exposure and MetS prevalence in a cross-sectional study.

METHODS

Concentrations of 8 urinary essential metals and plasma C-reactive protein (CRP) were quantified in 3272 adults from Wuhan-Zhuhai cohort. Urinary essential metals were adjusted by the corresponding urinary creatinine concentrations and reported as μg/mmol creatinine. Multivariable logistic regression and linear regression models were used to evaluate dose-response relationships between essential metals, plasma CRP, and MetS prevalence. Mediation analysis was performed to investigate the role of plasma CRP in the associations between urinary essential metals and MetS prevalence.

RESULTS

In the single-metal models, we observed positive dose-dependent relationships of urinary copper and zinc with MetS prevalence. Compared with the lowest quartiles of urinary metals, the ORs (95% CI) of MetS in the highest quartiles were 1.40 (1.03, 1.91) for urinary copper and 2.07 (1.51, 2.84) for zinc, respectively. The dose-dependent relationships of zinc and copper with MetS remained significant in the multiple-metal models and Bayesian kernel machine regression (BKMR) models. No significant associations were observed between others essential metals (e.g. manganese, iron, cobalt, selenium, chromium, molybdenum) and MetS in this general population (all P value > 0.05). In addition, urinary copper and zinc increased monotonically with plasma CRP elevation, and plasma CRP was positively associated with the MetS prevalence. Mediation analysis indicated that plasma CRP mediated 5.2% and 3.2% in the associations of urinary copper and zinc with MetS prevalence, respectively.

CONCLUSIONS

Elevated concentrations of urinary copper and zinc were associated with increased prevalence of MetS. Systemic inflammation may play an important role in the associations of copper and zinc exposure with MetS.

An integrated approach to quantifying ecological and human health risks from different sources of soil heavy metals

Heavy metals (HMs) in soil cause adverse effects on ecosystem and human health. Quantifying ecological risk and human health risk (HHR) from sources can determine priority sources and help to mitigate the risks. In this research, geostatistics and positive matrix factorization (PMF) were used to identify and quantify the sources of soil HMs; and then ecological risk and HHR from different sources under woodland, construction land and farmland were quantitatively calculated by combining the potential ecological risk index (RI) and HHR assessment models with PMF model. Taking Jiedong District as an example, four sources were quantitatively apportioned, which were agricultural practices (23.08%), industrial activities (29.10%), natural source (22.87%) and traffic emissions (24.95%). For ecological risk, industrial activities were the greatest contributor, accounting for about 49.71%, 48.11% and 47.15% under construction land, woodland and farmland, respectively. For non-carcinogenic risk, agricultural practices were the largest source under woodland and farmland, while industrial activities were the largest source under construction land. As for carcinogenic risk, no matter which kind of land use, agricultural practices were the largest source. In addition, the health risks of children, including non-carcinogenic and carcinogenic risks, were higher than those of adults, and the trends in health risks for children and adults were similar. The integrated approach was useful to evaluate ecological risk and HHR quantification from sources under different land use, thereby providing valuable suggestions for reducing pollution and protecting human health from the sources.

Second generation effects of larval metal pollutant exposure on reproduction, longevity and insecticide tolerance in the major malaria vector Anopheles arabiensis (Diptera: Culicidae)

Background

Members of the Anopheles gambiae complex breed in clean, sunlit temporary bodies of water. Anthropogenic pollution is, however, altering the breeding sites of the vectors with numerous biological effects. Although the effects of larval metal pollution have previously been examined, this study aims to assess the transgenerational effects of larval metal pollution on the major malaria vector An. arabiensis.

Methods

Two laboratory strains of An. arabiensis, SENN (insecticide-susceptible) and SENN-DDT (insecticide-resistant), were used in this study. After being bred in water polluted with either cadmium chloride, copper nitrate or lead nitrate, several life history characteristics that can have epidemiological implications (fertility, apoptotic damage to reproductive structures, adult longevity and insecticide tolerance) were examined in the adults and compared to those of adults bred in clean water.

Results

All metal treatments reduced fecundity in SENN, but only lead treatment reduced fertility in SENN-DDT. Cadmium chloride exposure resulted in apoptosis and deformation of the testes in both strains. After breeding generation F0 in polluted water, F1 larvae bred in clean water showed an increase in longevity in SENN-DDT adult females. In contrast, after breeding the F0 generation in polluted water, longevity was reduced after cadmium and copper exposure in the F1 generation. Larval metal exposure resulted in an increase in insecticide tolerance in adults of the SENN strain, with SENN-DDT adults gaining the greatest fold increase in insecticide tolerance.

Conclusions

This study demonstrates that a single exposure to metal pollution can have transgenerational effects that are not negated by subsequent breeding in clean water.

Heavy metal speciation with prediction model for heavy metal mobility and risk assessment in mine-affected soils

Heavy metals from mines affect the soil and groundwater, and cause and severely impact on the health of local residents. The soil samples were characterized for the distribution and by the chemical speciation method, and then estimated the human health risks of the two mineaffected soils after stabilization process.. Two extraction techniques (Tessier and Wenzel methods) were applied to fractionate metals, such as arsenic (As) and zinc (Zn), to quantify the chemical status of metals in the soils. The mobility of As and Zn was predicted using the ASTM test and sequential extraction (Tessier and Wenzel) method results. The correlation coefficients of As and Zn mobility prediction using Tessier and Wenzel Fraction 1 were 0.920 and 0.815, respectively. The sum of fractions F1 + F2 + F3 showed the highest correlation coefficients value and F value for mobility prediction of both As and Zn. The hazardous indices (HI) for non-carcinogenic risk and carcinogenic risk (CR) to humans were evaluated according to the pseudo-total concentrations of metal in soils. The CR values of carcinogenic for As were within the ranges from 1.38 × 10^-4 to 1.25 × 10^-3 and 3.71 × 10^-4 to 3.35 × 10^-3 for both Young Dong (YD) and Dea San (DS), respectively. The HI for non-carcinogenic risk was the highest for As in the YD (2.77) and DS (7.46) soils, which covered approximately 96 and 84% of HI, respectively. In summary, the contribution of As to risk from heavy metals was dominant.

Trace metal element pollution of soil and water resources caused by small-scale metallic ore mining activities: a case study from a sphalerite mine in North China

Trace metal element contamination in mining areas is always a huge environmental challenge for the global mining industry. In this study, an abandoned sphalerite mine near the Yanshan Mountains was selected as subject to evaluate the soil and water contamination caused by small-scale mining. The results show that (1) Pearson correlation matrix and principal component analysis (PCA) results reveal that Zn, Cu, Cd, and Pb were greatly affected by the operation of mines, especially mineral tailings. The contents of trace metal elements decrease with the increase of the distance from the mining area. Zinc, Pb, and Cd were discovered in almost all soil samples, and Zn accounted for about 80% of pollution of the topsoil. (2) The trace element pollution levels in the topsoil of the three villages were ranked as follows: Cd > Cu > Pb~Zn. The potential ecological risk of farmland around the mine ranges from lower to higher, with Cd being the most harmful. (3) Human health risk assessment results show that trace elements in the mining area pose obvious non-carcinogenic health risks to children while the risks to adults are not equally obvious. The carcinogenic risk of Cd and Cr is within a safe range and does not pose an obvious cancer risk to the population.

Spatial and interspecies differences in concentrations of eight trace elements in wild freshwater fishes at different trophic levels from middle and eastern China

There have been numerous studies on concentrations of trace elements in aquatic ecosystems, but few have been conducted at a large spatial scale. This study collected 410 samples of five wild freshwater fishes at different trophic levels from middle and eastern China. Concentrations of eight trace elements, chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb) and cadmium (Cd) and stable isotope ratios (δ¹³C and δ¹⁵N) were determined in dorsal muscle of fishes. Spatially, concentrations of trace elements were least in fishes from the Hai River Basin, while those in fishes from the Taihu Lake Basin were greatest. The carnivorous topmouth culter and omnivorous common carp and crucian carp accumulated greater amounts of trace elements than did the planktivorous silver carp and bighead carp. Trophic biomagnification was for Cu, Fe and Zn, but not for Cr, Ni, As, Pb and Cd. Concentrations of As in 15 muscle samples (3.7%) from Taihu Lake Basin exceeded the guidelines (1.0 mg/kg, wet mass) provided by FAO/WHO (2014), while the total target hazard quotient (TTHQ) values were <1.0, indicating no obvious non-carcinogenic risks to humans that consume those fishes. However, people who consume larger amounts of fish products, or people who are vulnerable, such as pregnant women, children and people with poor health, might be at greater risk. Also, exposure to trace metals through other routes cannot be ignored. Accumulations of trace elements in Chinese freshwater fishes were affected by both geographical conditions and human activities.

Atmospheric bulk deposition of heavy metal(loid)s in central south China: Fluxes, influencing factors and implication for paddy soils

The depositions of heavy metal(loid)s (HMs) were measured in an urban agglomeration of China to investigate the fluxes, influencing factors, sources, and potential effects of these HMs. Our results showed that the deposition fluxes of As and Cd were higher in this area than in other regions. In the area, 59.63% of the total deposition fluxes of the Cr, Cu, Ni, Pb and Zn were observed in the wet season (March to July). Lower total fluxes of HMs were observed at the rural site. Principal component analysis (PCA) results showed that the As, Cd, Pb, and Zn might originate from the same anthropogenic sources, including traffic and industrial sources, and that the Cr, Cu, and Ni might come from natural sources. Correlation analysis and redundancy analysis (RDA) showed that rainfall, wind speed, and PMs were critical factors influencing the atmospheric bulk deposition of HMs. For the paddy soil, the input fluxes of HMs by deposition, accounted for 38.66-84.57% (except for Cr) of the total input fluxes. The prediction indicated that the accumulation of HMs in surface soil will notably increase over the next decades due to the influence of atmospheric deposition.

Heavy metal distribution, translocation, and human health risk assessment in the soil-rice system around Dongting Lake area, China

Heavy metals including copper (Cu), zinc (Zn), cadmium (Cd), chromium (Cr), lead (Pb), and arsenic (As) were investigated in 89 pairs of rice plant and paddy soils around Dongting Lake area, China. Rice plants and soils were collected with GPS device, and heavy metal contents in different rice plant tissues and soils were measured. The aim of the present study was to assess the heavy metal pollution and translocation in the whole soil-rice system, including the consequent human health risk for residents. According to the indices of average geoaccumulation (I_geo) of the studied elements, paddy soils in study area were moderately polluted by Cd, lowly polluted by Pb, and not polluted by Cu, Zn, Cr, and As. Considering the much higher concentrations of studied elements in roots than in other tissues of rice plants, a great mass of these elements was assumed to be confined in the roots. The low translocation factors from root to shoot (Tf_root-shoot) of all the studied heavy metals (0.04-0.74) underpinned this. The high translocation factors from soil to root (Tf_soil-root) of Cd (9.12), As (4.38), and Zn (2.05) indicated the high bioavailability of these heavy metals for rice plant. The health risk assessment using target hazard quotients (THQs) model indicated that Cd (5.17 for adults and 4.49 for children respectively) and As (3.61 for adults and 3.14 for children respectively) could cause human health risk both for adults and children. Further, given the rate of individual THQ values exceeding one, Cu might also be considered as a potential human health dangerous element in the study area. It was worth noting that as one of the main pollutants, Pb did not show human health risk through rice grain consumption due to its low Tf values in soil-rice system. However, the risk identification of As using comparisons of measured concentrations with risk screening value in Chinese paddy soil standard (GB15618-2018) was not consistent with the human health risk assessment result. This might indicate that site-specific risk screening values of As in China is in demand.

A critical prospective analysis of the potential toxicity of trace element regulation limits in soils worldwide: Are they protective concerning health risk assessment? - A review

Trace elements (TEs) may have toxic effects to plants and humans; thus, countries and organizations impose maximum allowable regulation limits of their concentrations in soils. Usually such limits are placed in different categories according to soil use, soil properties or based on both attributes. However, some countries have regulation limits irrespective of differentiation in soil properties. In this review, we aimed at collecting TE regulation limits in soils from major countries and organizations around the globe, and critiquing them by assessing potential human health risks in the case of soils attaining the maximum allowable values. We explored the soil-to-human pathway and differentiated among three major exposures from TEs, i.e., residential, industrial and agricultural. We observed the existence of problems concerning TE regulation limits, among which the fact that limits across countries do not regulate the same TEs, not even a minimum number of TEs. This indicates that countries do not seem to agree on which regulation limits of TEs pose a high risk. Also, these regulation limits do not take into account TE mobility to neighbouring environment interphases such as plant, especially edible, and water matrices. Moreover, limits for same TEs are vastly diverse across countries; this indicates that those countries have conflicting information concerning TE-related health risks. Subsequently, we addressed this problem of diversity by quantifying resultant risks; we did that by calculating human health risk indices, taking into consideration the cases in which the highest allowable TE limits are attained in soil. Arsenic limits were found to generate a relatively high hazard quotient (HQ_i, accounting for human intake over the maximum allowable oral reference dose for that same TE), indicating that its risk tends to be underestimated. Other TE limits, such as those of Cd, Cu, Ni, Pb, and Zn typically result in low HQ_i, meaning that limits in their cases are rather overprotective. Our approach reveals the need of reducing diversity in regulation limits by drafting soil legislations of worldwide validity, since risks are common across countries. We suggest that new directions should strategically tend to (a) reduce limits of TEs with underestimated contribution to health risk (such as As), (b) cautiously increase limits of TEs that currently cause minor health risks, (c) quantify TE risks associated with uptake to edible plants and potable water, and (d) consider multi-element contamination cases, where risks are cumulatively enhanced due to TE synergism.

Biota-sediment metal accumulation and human health risk assessment of freshwater bivalve Corbicula fluminea in Dongting Lake, China

In this study, we analyzed the concentrations of metals in sediments and Corbicula fluminea in China's Dongting Lake to assess the suitability of C. fluminea as an effective biomonitor of metal contamination in sediments and food safety. We analyzed the biota-accumulation capacity by calculating the biota-sediment accumulation factor (BSAF) and assessed the potential human health risk of metals exposure via consumption of C. fluminea using the target hazard quotient (THQ) and total target hazard quotient (TTHQ). The results showed that the average concentrations of As (31.93 mg kg^-1), Cd (5.54 mg kg^-1), Cr (105.50 mg kg^-1), Cu (32.53 mg kg^-1), and Zn (207.89 mg kg^-1) in sediments were higher than their respective standard set by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. The sediment metals, which were mainly anthropogenic in origin, were at high levels and pose a relatively high ecological risk. Cadium (Cd) showed very high potential ecological risk levels and should be included in the prior pollutants list in the studied area. The mean levels of As (0.81 mg kg^-1) in C. fluminea were 1.62-times higher than that set by the National Health Commission of the People's Republic of China. BSAF values of the soft tissues of C. fluminea were between 0.05 and 2.14, with higher values for Cu (2.14), Cd (1.77), Zn (1.60), and Ni (1.27). Soft tissues of C. fluminea were able to reflect spatial differences in Sr within sediments around Dongting Lake. The results indicated that C. fluminea could be an potential biomonitor for sediment metals assessment in biomonitoring programs, especially for Cu, Cd, Zn, Ni, and Sr. The mean values for THQ and TTHQ of all the analyzed metals were below 1.0, indicating that the intake of metals via comsumption of C. fluminea does not result in an appreciable risk to human health.

Ionomic profile and arsenic speciation in Semisulcospira cancellata, a freshwater shellfish from a mine-impacted river in China

Freshwater aquatic environment close to cities and industrial areas is more sensitive than marine environment. The freshwater shellfish Semisulcospira cancellate was introduced as a bioindicator to monitor the heavy metal contamination in the river through ionomic profiles and arsenic speciation. The shellfish samples were collected near four cities along the Xiang River in China. The concentrations of elements including Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Cd, Sn, Sb, Ba, and Pb were determined using ICP-MS. Multivariate statistical analyses such as Pearson's correlation analysis and principle component analysis (PCA) were employed to identify the possible sources of the elements in the shellfish samples. Three principle components were extracted from the ionomic matrix and were associated with natural existence, biological pathways, and mining and smelting activities, respectively. The ionomic profiles of the shellfish samples were evaluated through hierarchical cluster analysis (HCA) which was exhibited in the form of heatmap. The shellfish samples were categorized according to the sampling sites with different contamination levels. Six As species including arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) were separated and quantified using HPLC-ICP-MS. The concentrations of As(III) and As(V) were linearly increased with total As concentration increasing. However, the proportion of AsB was decreased with total As while the AsB concentration was irrelevant to total As.

Assessment of heavy metal contamination, distribution and source identification in the sediments from the Zijiang River, China

In this study, the contents of 10 heavy metals (Sb, Cd, Cr, Mn, Co, Ni, Cu, Zn, As, and Pb) in 49 sediment samples from the Zijiang River were determined by using inductively coupled plasma-optical emission spectrometry. Contamination indexes including geoaccumulation index, modified degree of contamination, sediment quality guidelines, potential ecological risk index, together with potential ecological risk factor were used to assess heavy metal contamination in the sediments of the Zijiang River. Pearson's correlation analysis and principal component analysis were used to identify the sources of heavy metals. The results indicated that the mean values of heavy metals in the Zijiang River's sediments were found to be significantly higher than the corresponding background values. But when comparing with that in other rivers in the world, they were at medium levels except for Sb. Furthermore, a comparison of the heavy metal concentrations and the consensus-based sediment quality guidelines showed that the heavy metal pollutions (Cd, Cr, Ni, Cu, Zn, As, and Pb) tended to occasionally pose harmful impacts on the ecosystem. The values of contamination indexes revealed that serious heavy metal contamination and relatively high potential ecological risks were mainly existed in the downstream of antimony mining and smelting factories (S23-S49). In addition, high potential ecological risks of Sb were observed in sampling sites that were close to those factories (S23, S24, S25, and S27), and high potential ecological risks of Cd were observed in the downstream (S37-S49). Basing on the Pearson's correlation analysis and principal component analysis, three main sources were identified. Co, Zn, Cd, and Cu contaminants were mainly derived from agricultural activities; As, Sb, Mn, and Pb mainly came from mining and smelting activities; Cr and Ni were mainly from natural sources.

Trace elements concentrations in soil, desert-adapted and non-desert plants in central Iran: Spatial patterns and uncertainty analysis

The concentrations of Cd, Cr and Pb in soil samples and As, Cd, Cr and Pb in plant specimens were analyzed in an arid area in central Iran. Plants were categorized into desert-adapted (Haloxylon ammodendron, Atraphaxis spinosa and Artemisia persica) and non-desert species. It was found that the trace element (TE) accumulating potential of the desert species (Haloxylon ammodendron and Artemisia persica) with a mean value of 0.1 mg kg^-1 for Cd was significantly higher than that of the majority of the non-desert species with an average of 0.05 mg kg^-1. Artemisia also had a high As accumulating capability with a mean level of 0.8 mg kg^-1 in comparison with an average of 0.2 mg kg^-1 for most of the other plant species. The mean values of Cr and Pb in Haloxylon ammodendron and Artemisia persica were 5 and 3 mg kg^-1, respectively. Among the desert-adapted plants, Atraphaxis proved to be a species with high Cr and Pb accumulating potential, as well. The geoaccumulation index and the overall pollution scores indicated that the highest environmental risk was related to Cd. Different statistical analyses were used to study the spatial patterns of soil Cd and their connections with pollution sources. The variogram was estimated using a classical approach (weighted least squares) and was compared with that of the posterior summaries that resulted from the Bayesian technique, which lay within the 95% Bayesian credible quantile intervals (BIC) of posterior parameter distributions. The prediction of cadmium values at un-sampled locations was implemented by multi-Gaussian kriging and sequential Gaussian simulation methods. The prediction maps showed that the region most contaminated by Cd was the north-eastern part of the study area, which was linked to mining activities, while agricultural influence contributed less in this respect.

Pollution Assessment of Trace Elements in Agricultural Soils around Copper Mining Area

Agricultural soils from Dongchuan copper mining area were sampled and analyzed to determine the concentrations of selected trace elements, namely As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. The main objectives of this study were: (1) To determine the levels of trace elements and their spatial distribution in soils; (2) to evaluate the potential ecological risk; and (3) to identify the main sources of risk element pollution. The environmental risks were assessed using five different contamination and pollution indexes. Descriptive and exploratory statistical analyses were performed to identify the relations among the trace elements in soils and possible sources of pollution. Although the values of As, Cu and Zn in the soils were significantly higher than Yunnan background values and exceeded the limits of the Chinese national standards in several sampling points, the most serious threat for the ecosystem and human health was represented by Cd. The main sources of Cu and As were identified mining activities, airborne particulates from smelters and the weathering of tailings, and partly also agricultural fertilizers. The major source of Cd was agricultural fertilizers and partly sources associated with mining and smelting activities.

Evaluating a 5-year metal contamination remediation and the biomonitoring potential of a freshwater gastropod along the Xiangjiang River, China

Effective remediation of heavy metal pollution in aquatic systems is desired in many regions, but it requires integrative assessments of sediments, water, and biota that can serve as robust biomonitors. We assessed the effects of a 5-year metal contamination remediation along the Xiangjiang River, China, by comparing concentrations of trace metals in water and surface sediments between 2010-2011 and 2016. We also explored the trace metal biomonitoring potential of a freshwater gastropod (Bellamya aeruginosa). Metal concentrations in water (means and ranges) dropped over time to within permissible limits of drinking water guidelines set by China, USEPA, and WHO in 2016. Although sediment means and ranges of Cd, Pb, Zn, and Mn also diminished with remediation, those for Cr and Cu slightly increased, and all six metals retained concentrations higher than standards set by China. All metals in sediments could also be associated with anthropogenic inputs using a hierarchical clustering analysis, and they generate high potential ecological risks based on several indices, especially for Cd and As. The bio-sediment accumulation factors of all measured trace metals in gastropod soft tissues and shells were lower than 1.0, except for Ca. Trace metal contents in gastropods were positively correlated with those in water and surface sediments for As (soft tissues) and Cr (shells). Collectively, our results do not yet highlight strong beneficial effects of 5-year remediation and clearly illustrate the heavy metal pollution remaining in Xiangjiang River sediment. Additional physical, chemical, and biological measurements should be implemented to improve sediment quality. We further conclude that gastropod soft tissues and shells can be suitable biomonitors of spatial differences in some heavy metals found within river sediments (e.g., As, Cr).

Distribution, contamination and accumulation of heavy metals in water, sediments, and freshwater shellfish from Liuyang River, Southern China

Heavy metal distributions in water, sediments, and freshwater shellfish collected from Liuyang River in China have been investigated. The concentrations of heavy metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb were determined by ICP-MS. The distribution pattern of heavy metals in sediments was different from that in water. Large coefficients of variation of heavy metal concentrations were observed in water due to the susceptibility to discharge fluctuation and seasonal variation. Multivariate statistical analysis such as Pearson's correlation analysis, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were employed to identify the possible sources of heavy metals in sediments. These heavy metals were categorized into three distinct groups, one was derived from natural existence and two were associated with anthropogenic activities. Five shellfish species including three species of gastropod mollusks (Parafossarulus eximius, Semisulcospira cancellata, and Pomacea canaliculata) and two species of bivalve mollusks (Corbicula fluminea and Anodonta woodiana) were collected and investigated. The distribution pattern of heavy metals in shellfish species was visualized by the nonmetric multidimensional scaling (NMDS) plot. The metal pollution index (MPI) values for the shellfish species were in the descending order of C. fluminea > A. woodiana > S. cancellata > P. eximius > P. canaliculata.

Accumulation, translocation and conversion of six arsenic species in rice plants grown near a mine impacted city

Paddy rice (Oryza sativa L.) as the staple food in China was found to be efficient in accumulating arsenic (As) due to cultivated in flooded paddy soil. Uptake and translocation of As in rice plant depended on the As species. In this work, rice plant samples including roots, straws and grains as well as rhizosphere soils were collected from paddy fields near Changsha, a mine impacted city in Southern China. The total As concentrations in the collected samples were observed in the descending order as root > soil > straw > grain. The predominant As species detected in rice plants were inorganic forms: arsenite [As(III)] and arsenate [As(V)]. Except monomethylarsonate (MMA) and dimethylarsinate (DMA), other two organoarsenicals, arsenobetaine (AsB) and arsenocholine (AsC), were also detected in rice plants. DMA and AsB were mainly formed in rice roots with the assistance of microorganisms. MMA and AsC detected in straws might be derived from methylation and oxidation of As(III). The results of multiple linear regressions indicated that the straw As species were remarkable predictors of the corresponding grain As species. Demethylation or degradation of MMA, DMA and AsC were predicted when translocated from straw to grain.

Arsenic speciation and heavy metal distribution in polished rice grown in Guangdong Province, Southern China

Arsenic speciation and heavy metal distributions have been investigated in locally grown rice grains from Guangdong Province, Southern China. A total of 41 polished rice grain samples were collected throughout Guangdong Province. Arsenite (As(III)), as the predominant form found in the rice, was positively correlated (p<0.01) with total As (tAs) concentration. However, the percentage of As(III) reduced while tAs concentration increased (r=-0.361, p<0.05), due to restricted accumulation and translocation of As(III) in rice grains at high level of tAs. Statistical and geostatistical analyses were applied to investigate potential origins of heavy metals in rice. Only Cd, Cu and Ni were identified as influenced by anthropogenic sources such as industrial and commercial activities. As and Pb were primarily controlled by natural occurrence. The results of health risk assessment implied that continuous intake of rice grown in Guangdong Province could cause considerably non-carcinogenic and carcinogenic risk to local inhabitants.

Effects on heavy metal accumulation in freshwater fishes: species, tissues, and sizes

Three fish species (Carassius auratus, Pelteobagrus fulvidraco, and Squaliobarbus curriculus) were collected from Xiang River near Changsha City, Southern China. The concentrations of heavy metals including arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), lead (Pb), and zinc (Zn) in the muscle, gill, and liver of three species were determined by the inductively coupled plasma mass spectrometry method. One-way analysis of variance (ANOVA) was introduced to determine the significant variations (p < 0.05) of heavy metals. Livers were found to accumulate Cd and Cu due to the metallothionein proteins. High levels of Mn and Pb in the gills indicated that the main uptake pathway of these heavy metals was from the water. The carnivorous species, P. fulvidraco, was found to accumulate the highest levels of toxic elements (As, Cd, and Pb), while relatively high concentrations of nutrient elements (Cu, Fe, Mn, and Zn) were accumulated in omnivorous species (C. auratus and S. curriculus). According to the results of Pearson's correlation analysis, there were few significant relationships at p < 0.01 level between the concentrations of the analyzed elements and the fish sizes. The results of risk assessment indicated that exposure to the toxic heavy metals from fish muscle consumption posed no non-carcinogenic health risk to local inhabitants.

Accumulation behavior and risk assessment of heavy metals and arsenic in tissues of white bream (Parabramis pekinensis) from the Xiang River, southern China

Aquatic environment suffered from serious heavy metal and As pollutions due to rapid industrialization and urbanization in the last decades. In order to evaluate the heavy metal and As contamination in aquatic organism in southern China, the levels of As, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn in muscle, gill, and liver of white bream (Parabramis pekinensis) collected from Xiang River were analyzed. The statistically significant differences of the analyzed element concentration (wet weight) between tissues were determined through one-way analysis of variance (ANOVA). The liver presented high affinity for accumulation of Cd, Cu, and Zn due to the binding activity of metallothionein proteins. Mn and Pb mainly accumulated in the gill indicated the major uptake route through the gill. Lack of correlation between analyzed element and fish size might imply no or weak biomagnification of the analyzed elements in fish tissues. The potential health risk associated with exposure to heavy metals and As was evaluated. The uncertainty of target hazard quotient was calculated by Monte Carlo simulation. The results indicated that the analyzed element contents in the white bream muscle posed relatively low-chronic toxic risk to consumers.