Combined pollution characteristics and ecological risks of multi-pollutants in Poyang Lake.

Poyang Lake, the largest freshwater lake in China, faced severe ecological degradation in the past decade. Combined pollution of multi-pollutants may be one of the contributing factors. However, the characteristics of combined pollution and the ecological risks are still not clear. In this study, we used Polar Organic Chemical Integrative Sampler (POCIS), In Situ Bioassay Passive Sampling Device (ISBPSD) and conventional sampling methods, to study the toxic pollutants levels and the combined biological toxicity effects. The results showed that high levels of organochlorine pesticides (OCPs, averaged 162 ng/g) and polycyclic musk (PCM, averaged 53.6 ng/g) residues, as well as some metals such as nickel (Ni), lead (Pb) concentrations exceeded the relevant standard level in the sediment. The risk of combined pollution in the water was relatively low, but high risk was found in the sediments. According to the ISBPSD studies, the survival rates of species in the water and sediments were only 10.0-45.0% and 1.67-11.7% respectively, which was much lower than that reported in other typical basins of China. OCPs, PCMs, and certain metals such as Pb and Ni may be the key toxic pollutants causing biological toxicity effects in Poyang Lake.

Effects of Antimony on Rice Growth and Its Existing Forms in Rice Under Arbuscular Mycorrhizal Fungi Environment.

Arbuscular mycorrhizal fungi (AMF) can form symbiotic relationships with most terrestrial plants and regulate the uptake and distribution of antimony (Sb) in rice. The effect of AMF on the uptake and transport of Sb in rice was observed using pot experiments in the greenhouse. The results showed that AMF inoculation increased the contact area between roots and metals by forming mycelium, and changed the pH and Eh of the root soil, leading to more Sb entering various parts of the rice, especially at an Sb concentration of 1,200 mg/kg. The increase in metal toxicity further led to a decrease in the rice chlorophyll content, which directly resulted in a 22.7% decrease in aboveground biomass, 21.7% in underground biomass, and 11.3% in grain biomass. In addition, the antioxidant enzyme results showed that inoculation of AMF decreased 22.3% in superoxide dismutase, 9.9% in catalase, and 20.7% in peroxidase compared to the non-inoculation groups, further verifying the negative synergistic effect of AMF inoculation on the uptake of Sb in rice. The present study demonstrated the effect of AMF on the uptake and transport of Sb in the soil-rice system, facilitating future research on the related mechanism in the soil-rice system under Sb stress.

Exposure characteristics of antimony and coexisting arsenic from multi-path exposure in typical antimony mine area.

In this study, samples of daily foods, drinking waters, surface waters, and soils were collected and screened to investigate the external exposure of Sb and As from various intake pathways in typical Sb mining area. Biomarker samples of residents were analyzed to monitor internal exposure characteristic of Sb and As in human body. Exposure dosages of As and Sb and transfer of Sb and As from environment to human body were estimated based on the external and internal exposure. The following results were obtained: daily intakes of food accounted for major intakes of both Sb and As, and highlighted the significance of foods intakes from rice and vegetable. The results of Monte Carlo simulations showed that total daily intake of Sb(n = 1444)and As(n = 1131) approximately reached 1.08 × 10-2 mg/kg/d and 1.19 × 10-3 mg/kg/d, in which 98.82% and 63.07% of residents have exceeded the threshold dosages of Sb and As. The contaminants contents in biomarkers indicated that Sb exhibited the similar internal exposure as As, while the total transfer rate of Sb from environment to human were estimated as approximately 2.04-2.40 times lower than As. This study also suggested that drinking water is another important pathway with high bioavailability and male resident may present higher priority than female in uptake of Sb and As. The paper suggested the similarity and difference on bioavailability existed in Sb and its group V elements, As, that would provide the essential information on exposure of Sb and As in the typical Sb mine area.

Aggregation and stability of sulfate-modified polystyrene nanoplastics in synthetic and natural waters.

Nanoplastics (NPs) are becoming emerging pollutants of global concern. Understanding the environmental behavior of NPs is crucial for their environmental and human risk assessment. In this study, the aggregation and stability of polystyrene (PS) NPs were investigated under different hydrochemical conditions such as pH, salt type (NaCl, CaCl2, Na2SO4), ionic strength (IS), and natural organic matter (NOM). The critical coagulation concentrations of PS NPs were determined to be 158.7 mM NaCl, 12.2 mM CaCl2, and 80.0 mM Na2SO4. Ca2+ was more effective in destabilizing PS NPs, compared to Na+, owing to its stronger charge screening effect. In the presence of monovalent ions, NOM reduced aggregation through steric repulsion, whereas in the case of divalent ions, NOM induced aggregation through cation bridging. Initial and long-term stability studies demonstrated that, in waters with high IS and NOM content, NOM was the most significant factor affecting NPs aggregation. PS NPs would be highly suspended in all freshwaters, and even in wastewater, whereas they would aggregate rapidly and deposit in seawater. Finally, a statistical model was established to evaluate the hydrodynamic diameter of NPs in different waters. The results indicated the stability of PS NPs in natural aquatic environments and their potential for long-term transport.

Synthesis of Fe3O4 magnetic nanoparticles coated with cationic surfactants and their applications in Sb(V) removal from water.

Antimony (Sb) pollution was an emerging environmental risk in several contaminated waters, whereas its removal still presented as a severe challenge due to the lack of efficient adsorbent and its further removal mechanism. In this study, synthesized absorbents, Fe3O4 magnetic nanoparticles (Fe-MNPs) modified and dispersed with commonly used cationic surfactants, were applied to remove Sb contamination in real surface waters, its synthesized conditions, removal performance and mechanism were investigated by using batch experiments and characterization analyses. Optimum conditions on Sb(V) (the dominant form is Sb(OH)6-) removal by modified adsorbents were obtained as: cetylpyridinium chloride (CPC) coated on Fe-MNPs, mass ratio of Fe-MNPs: CPC = 4:1 and pH = 3-5. Magnetic properties of synthesized adsorbent were not affected, dispersibility was enhanced after fabrication of CPC, that indicated the Fe-MNPs@CPC could be separated and reused with external magnetic field. The adsorption efficiency of this low-cost adsorbent coated with CPC was superior than several traditional adsorbents. The practical application of Fe-MNPs@CPC in five types real waters from the Xikuangshan (XKS) Sb mine area and regeneration experiments by 1 M (mol/L) NaOH solution further confirm its practicability and reusability. Removal experiment results, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) spectra suggested that electrostatic attraction and surface bonding might responsible for the Sb(V) removal by Fe-MNPs modified with cationic surfactants.

Identifying bioaccessible suspect toxicants in sediment using adverse outcome pathway directed analysis.

Chemical mixtures are a common occurrence in contaminated sediment and determining causal relationship between sediment contamination and adverse outcomes is challenging. The bioavailability and choice of bioassay endpoints played important roles in elucidating causality. As such, bioaccessibility-based XAD extraction and adverse outcome pathway (AOP) guided bioassays were incorporated into an effect-directed analysis to more effectively determine sediment causality. XAD extracts of sediments from urban waterways in Guangzhou, China were examined using cell viability bioassays with four human tumor cells from lung, liver, breast, and bone marrow. Pronounced effects to SH-SY5Y cells were noted, thus neurotoxicity was subsequently focused in the AOP-guided bioassays. Intracellular calcium influx, mitochondrial membrane potential inhibition, reactive oxygen species generation, and cell viability were utilized as evidence for neurotoxicity AOP-guided analysis. Suspect toxicants were identified in active fractions using GC-MS. Toxicity confirmation was performed by evaluating toxicity contributions of the candidates to the pathway. Cypermethrin, bisphenol A, galaxolide, tonalide, and versalide were found as the major stressors across key events of the studied pathway. Moreover, good correlations among key events validated the feasibility of method to predict in vivo response, suggesting that considering bioavailability and AOP improved environmental relevance for toxicant identification in a complex mixture.

Technical study on national mandatory guideline for deriving water quality criteria for the protection of freshwater aquatic organisms in China.

Water quality criteria are the basis for formulating environmental water quality standards, and are also an important part of environmental water protection and environmental management programs. The current study focused on a systematic discussion of the current research progress of water quality criteria theories and methodology for aquatic organisms both in China and internationally. This study also successfully pointed out key scientific issues which should be considered in the determination of water quality criteria guidelines from the following perspectives for a national strategy: the selection of pollutants; data collection and screening; species selection; water quality criteria derivation methods, and so on. For the first time, this study systematically introduced technology for the determination of water quality criteria guidelines for protecting aquatic organisms which was suitable for China's regional characteristics and national conditions. Furthermore, this study pointed out the key research directions which should be considered in the future construction of China's environmental criteria and management systems, in order to provide technical support for environmental protection and management projects.

Heavy metal distribution in Tiaoxi River's sediment.

According to current study, seven surface sediments and three sediment cores were collected from three typical areas of Tiaoxi River, which were living area, agricultural area, and industrial area. The water quantity into the Lake Taihu from the Tiaoxi River accounted for almost one third of the total water quantity by all rivers into the Lake Taihu. To study geochemical features and pollution history of heavy metals in three typical areas of Tiaoxi River, total content and chemical fractionations of Cu, Pb, Cd, Cr, Mn, Zn, Fe, As, and Hg were analyzed for surface and core sediments using the speciation extraction procedure, proposed by the Commission of the European Communities Bureau of Reference (BCR), together with grain size and organic carbon measurements. The results showed that the concentration of nine heavy metals and the variation characteristics of Zn, Cu, Fe, Mn, and Cr are different among five cores, which has shown that the river responses to natural and anthropogenic activities were dissimilar in various areas. BCR sequential extraction showed contents of Cr, Fe, and Cu were dominated in the remaining parts. Non-residual fractions for Zn and Mn contained major portions. Based on RAC (risk assessment core), the risk of Mn was high to very high in the three typical areas, and the risk of Zn was medium in the three typical areas.

Removal of antimonate (Sb(V)) and antimonite (Sb(III)) from aqueous solutions by coagulation-flocculation-sedimentation (CFS): Dependence on influencing factors and insights into removal mechanisms.

This study investigates the effects of different influence factors on the removal of inorganic Sb species using coagulation-flocculation-sedimentation (CFS) and establishes the mechanism of the process. Thus, the influence of pH, initial Sb concentrations, coagulant dosages and competitive matters on Sb(V) and Sb(III) removal via CFS with polymeric ferric sulfate (PFS) was investigated systemically. Competition experiments and characterization methods, including X-ray diffraction (XRD), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS), were performed to determine the mechanisms of the process. The main conclusions included: (i) Optimum Sb removal was observed at a pH range of 4-6 and dosages of 4 × 10-4 mol/L and 8 × 10-5 mol/L for Sb(V) and Sb(III), respectively. Additionally, both Sb(V) and Sb(III) removal could be inhibited by the presence of phosphate and humic acid (HA). (ii) A higher priority was observed for the removal of Sb(III) over Sb(V). (iii) After excluding precipitation/inclusion/occlusion, coprecipitation involving chemical bonding played a significant role in both Sb(V) and Sb(III) removal, and electrostatic force served another significant role in Sb(V) removal. The Sb(V) and Sb(III) contamination in real contaminated waters was successfully removed using PFS via CFS process. The results of this study provide insights into the removal mechanisms of inorganic Sb species via CFS.

Influences of environmental factors on biomass of phytoplankton in the northern part of Tai Lake, China, from 2000 to 2012.

Long-term (2000 to 2012) monthly data on communities of phytoplankton, and environmental variables were measured in water collected from Meiliang Bay and Wuli Lake of Tai Lake, China. Redundancy analysis (RDA) was conducted to explore relationships between the phytoplankton communities and environmental variables. Change points for concentrations of nutrients, which serve as early warnings of state shifts in lacustrine ecosystems, were identified using the Threshold Indicator Taxa Analysis (TITAN). The biomass of phytoplankton was positively correlated with the concentrations of total phosphorus (TP), suspended solids (SS), water temperature (WT), and pH but negatively correlated with the N/P ratio (by mass) and Secchi disk depth (SD). Furthermore, TP, rather than other factors, was a controlling factor limiting the primary production of phytoplankton in most of this region. The change points for concentrations of TP controlling the occurrences of sensitive and tolerant taxa were 56.1 and 103.5 µg TP/L, respectively. These results imply that an abrupt change in this lacustrine ecosystem has occurred in most parts of the study area, and the turbid state of this lake can be altered by reducing TP loading. This study provides an alternative ecological method for exploring the production of algal blooms and could advance the understanding of HABs.

Copper and zinc, but not other priority toxic metals, pose risks to native aquatic species in a large urban lake in Eastern China.

Over the past 20 years, global production of copper (Cu) and zinc (Zn) rank in the top three compared to other metals such as Pb, Cd, Cr, Ni, As and Hg. However, due to the potential for exposure and toxicity to humans, more attention of environmental pollution was paid to other metals such as Cd and Hg. Aquatic organisms are sensitive to Cu and Zn. Even though internal concentrations of these required elements are homeostatically controlled, toxic effects can occur at the fish gill surface. In this work, concentrations in surface waters and toxic effects of Cu, Zn, Ni, Cr, Pb, Cd, As, Hg were determined and risk of various metals in Tai Lake, China were evaluated using both risk quotients and joint probability distributions. Two transition metals, Cu and Zn posed the greatest risks to aquatic organisms while measured concentrations of other metals were less than thresholds for adverse effects. Approximately 99.9% and 50.7% of the aquatic organisms were predicted to be affected by Cu and Zn in surface water of Tai Lake respectively. Our results highlight ecological risks of Cu and Zn in water of a typical, large, urban lake in Eastern China, which was ignored in the past.

Comparison of arsenic and antimony biogeochemical behavior in water, soil and tailings from Xikuangshan, China.

Although similar geochemical behaviors of arsenic (As) and antimony (Sb) in the environment has been assumed and widely reported, growing evidence suggests the two elements cannot, under some conditions, be assumed to behave similarly. In this four-year study (samples collected in each year), comparative investigation of the biogeochemistry of As and Sb in water/fish, soil/vegetable, tailings/plant samples were carried out at the world's largest active Sb mine area (Xikuangshan, China). Depending on duration the tailings had been stacked, significant differences in spatial distributions between As and Sb were found, and these were associated with change in pH over time. Bio-accumulation factors (BAFs) of As were approximately 10-fold greater than those of Sb in fish/water, plant/tailing, and vegetable/soil systems. Sb had higher BAF in non-fatty tissues such as gills of fishes and shells of crabs. BAFs of Sb in vegetable/soil exhibited insignificantly, but different from As, positive correlation with pH in soil.

Elemental bioimaging of tissue level trace metal distributions in rice seeds (Oryza sativa L.) from a mining area in China.

Rice is a staple food and major source of nutrients, but it also bioaccumulates toxic elements. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine tissue-level trace metal spatial distribution in rice (Oryza sativa) seeds from the active Xikuangshan Sb mine area in China. Whole grain quantified elemental bioimages showed the highest concentration of Zn (1755 mg/kg) in the embryo andmicro zones of elevated Sb, As, Pb, Cd as high as 280, 57, 31 and 830 mg/kg, respectively on the husk/bran/endosperm tissues. Bioimages suggest that both Sb and Cd may be competing with Zn for binding sites. Both Sb(III) and Sb(V) species were detected in seeds from upstream and downstream fields indicating the presence of toxic Sb(III). Brown rice is a good source of Zn, but white rice is a safer option if rice is grown in a polluted area.

Antimony pollution in China.

Antimony (Sb) is ubiquitous throughout the environment as a result of natural processes and human activities. In China, superlarge-, large and medium-sized Sb deposits are concentrated in the Guangxi (34.4%), Hunan (21.2%), Yunnan (12.2%) and Guizhou (10.2%) provinces. Due to Sb mining and smelting processes, large quantities of Sb have been released resulting in serious Sb contamination of the local environments. Furthermore, coal combustion and Sb products consumed by the domestic market are also important potential Sb contamination sources. Here, an integrated overview of the current knowledge on the distribution of Sb in Chinese environments and the human health risk with respect to Sb contamination in Chinese mining and smelting areas are presented. The average Sb concentrations found in soils were divided into three groups. Group 1 had lower Sb concentrations of 0.5-1.5mgkg(-1), Group 2 had medium concentrations of 1.5-2mgkg(-1), and Group 3 had relatively high concentrations of over 2mgkg(-1). Soils from the Yunnan, Guangxi, Guizhou and Hunan provinces were extremely enriched in Sb. Data on the sediment and water mainly came from the Yangtze River water systems and some mining and smelting areas. The Sb concentrations in sediments were of the order of a few mgkg(-1). In water, Sb was mainly concentrated in the particle matter. Higher concentrations in water (up to 29.4mgL(-1)) and sediments (up to 1163mgkg(-1)) were mainly limited to the proximity of mining and smelting areas than the faraway places (<5.00mgL(-1) for water and <3.00mgkg(-1) for sediments, respectively). Plants growing in these contaminated soils accumulated high levels of Sb (up to 143.7mgkg(-1)) and exceeded the tolerable concentration (5mgkg(-1)), thus threatening the health of local inhabitants. The local environments around Sb mining and smelting areas were seriously contaminated.

Health risk associated with dietary co-exposure to high levels of antimony and arsenic in the world's largest antimony mine area.

Like arsenic (As), antimony (Sb) is known to be a genotoxic element in vitro and in vivo. Sb is now recognized as a global contaminant and has aroused the global concerns recently. However, knowledge is scarce concerning the transfer of Sb from the environment to humans and the related hazards to human health. In this pilot study, the health risk and main pathway of long-term human exposure to Sb and As for residents around Chinese Xikuangshan (XKS) Sb mine, the world's largest Sb mine, were evaluated by dietary exposure and hair accumulations survey. The concentrations and species of Sb and As in food samples (n=209) from three main categories and six subcategories, and in hair samples (n=89) were determined. Residents in the vicinity of XKS had an estimated dietary intake of Sb (554 µg/day) which was 1.5 times higher than the tolerable daily intake (TDI) (Sb, 360 µg/day), whereas their dietary intake of inorganic As (107 µg/day) was slightly lower than the provisional tolerable weekly intake (PTWI) of 15 µg/kg BW/week (equal to 129 µg As/day). Hair Sb and As concentrations (Sb, 15.7 mg/kg, DW; As, 3.99 mg/kg, DW) in XKS residents are both above the normal/toxic level. Rice, vegetables (especially leafy vegetable), drinking water, and meat/poultry were the dominant dietary intake sources of Sb for the residents. In contrast, rice was the uniquely dominant dietary intake source of As. Antimonate (Sb(V)) was the dominant Sb species in vegetables, drinking water and residents' hairs. This study highlighted the difference of exposure characteristics between Sb and As. The preliminary results suggested that dietary exposures to Sb, rather than As, was the dominant health risk to local residents. Nevertheless, the adverse effects of As levels on the health of residents still can not be ignored since the elevated As concentrations in human hair have reached the critical level for health risks. In addition, this pilot study did not consider the possible Sb and As combined effects.

Antimony, arsenic and mercury in the aquatic environment and fish in a large antimony mining area in Hunan, China.

Antimony (Sb) has received increasing attention recently due to its toxicity and potential human carcinogenicity. In the present work, drinking water, fish and algae samples were collected from the Xikuangshan (XKS) Sb mine area in Hunan, China. Results show that serious Sb and moderate arsenic (As) contamination is present in the aquatic environment. The average Sb concentrations in water and fish were 53.6 + or - 46.7 microg L(-1) and 218 + or - 113 microg kg(-1) dry weight, respectively. The Sb concentration in drinking water exceeded both Chinese and WHO drinking water guidelines by 13 and 3 times, respectively. Antimony and As concentrations in water varied with seasons. Fish gills exhibited the highest Sb concentrations but the extent of accumulation varied with habitat. Antimony enrichment in fish was significantly lower than that of As and Hg.

[Pollution characteristics of antimony, arsenic and mercury in human hair at Xikuangshan antimony mining area and Guiyang City, China].

The concentration levels of antimony, arsenic and mercury in human hair collected from Xikuangshan antimony mining area and Guiyang City were determined by hydride generation-atomic fluorescence spectrometry after having been digested by nitric acid and perchloric acid. The contents of Sb, As and Hg are 15.9, 4.21, 1.79 microg/g in the samples from Xikuangshan antimony mining area and 0.532, 0.280, 0.338 microg/g in the samples from Guiyang City respectively. The contents of Sb, As and Hg in human hair of Xikuangshan antimony area are much higher than those of Guiyang City. The independent-samples t-test shows that there are no marked differences in the contents of Sb and As between male and female hair samples from both Xikuangshan antimony mining area and Guiyang City (p > 0.05), while Hg contents in male hair are apparently higher than those in female hair from Guiyang City (p < or = 0.05). There is positive correlation observed between As and Sb, as well as between As and Hg, while Sb is weakly correlated with Hg (p < or = 0.01). These results show that the heavy metals (Sb, As and Hg) in antimony mining area may significantly affect human health than in the un-mining areas.

Allocation and source attribution of lead and cadmium in maize (Zea mays L.) impacted by smelting emissions.

Plants grown in contaminated areas may accumulate trace metals to a toxic level via their roots and/or leaves. In the present study, we investigated the distribution and sources of Pb and Cd in maize plants (Zea mays L.) grown in a typical zinc smelting impacted area of southwestern China. Results showed that the smelting activities caused significantly elevated concentrations of Pb and Cd in the surrounding soils and maize plants. Pb isotope data revealed that the foliar uptake of atmospheric Pb was the dominant pathway for Pb to the leaf and grain tissues of maize, while Pb in the stalk and root tissues was mainly derived from root uptake. The ratio of Pb to Cd concentrations in the plants indicated that Cd had a different behavior from Pb, with most Cd in the maize plants coming from the soil via root uptake.

Heavy metals in an impacted wetland system: a typical case from southwestern China.

Historical zinc smelting in Hezhang, southwestern China, has resulted in significant heavy metal contamination of the surrounding ecosystems. The Caohai wetland system, which is an important national nature reserve close to the Hezhang zinc smelting area, was investigated in the present study. Results showed that sediments from the Caohai wetland system have been seriously contaminated by Cd, Pb and Zn with the highest concentrations in the surface sediments being up to 71, 160 and 1,200 microg g(-1), respectively. The heavy metals in the sediments were strongly associated with the organic/sulphide and residual fractions. A more oxidized condition induced by aquatic plants tended to cause the Cd, Pb and Zn bound to the Fe-Mn oxide fraction to become more dominant. Pb isotopic compositions in the sediments indicated that the inventories of Pb in the Caohai wetland sediments were mainly derived from the historical zinc smelting in the Hezhang area, although other anthropogenic sources, such as the gasoline Pb, also made a substantial contribution to the Pb in the sediments. Heavy metal contamination in aquatic plants was also studied and the results indicated that heavy metals accumulated by plants may pose a potential threat to the higher trophic-level organisms, including humans.