Assessment of heavy metal content, distribution, and sources in Nansi Lake sediments, China

Release characteristics of arsenic from sediments and its source or sink competition with phosphorus: A case of a great lake with grass-algae alternation

The arsenic (As) release from sediments in great lakes is affected by various factors. In this study, the characteristics of As release from sediments was investigated, and the As sources and sinks with the strengths in sediments from different areas (grass-type, algae-type, and grass-algae alternation areas) in great shallow lakes (Taihu Lake, China) were analyzed, and the influence of P competition in the process of As release was also studied. The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes (0 to 28.12 µg/L), and the sediments from algae-type areas had the higher values. The sediments from western lake and northwest lake bay were a strong As and a weak P source, and the north lake bay had the opposite trend of these two regions. Intense P source competition with As from the sediments occurred in algae-type areas. The grass-type areas had strong As and P retention capacities, indicating a sink role of sediment with high As and P sorption capacities. The degree of As and P saturation had similar trend in sediments, and the grass-type areas had the higher values, 18.3%-21.4% and 15.31%-20.34%, respectively. Contribution analysis results showed that most of As release contribution was from the bottom (30-50 cm) sediments, and the surface (0-10 cm) sediments from algae-type areas contributed more to the overlying water than other region.

Sex-specific associations between maternal exposure to metal mixtures and fetal growth trajectories: A prospective birth cohort study

BACKGROUND

The associations of prenatal metals exposure with birth outcomes have been widely assessed. However, evidence on the associations between metal mixtures and fetal intrauterine growth trajectories is scarce.

OBJECTIVES

This study aimed to explore the associations of metal mixtures with fetal intrauterine growth trajectories overall and by sex.

METHODS

We analyzed data from the Ma'anshan birth cohort, which included a total of 1041 pregnant woman. The concentrations of 12 metals in maternal blood were measured during early pregnancy, and fetal intrauterine growth indicators were standardized and assessed at 16, 23, 30, 34, and 38 weeks of gestation. We used generalized linear regression and linear mixed models to identify the key fetal growth indicator (biparietal diameter (BPD)), and applied GBTM to characterize BPD SD-scores trajectories. To further assess the individual and combined effects of metals, we conducted multivariable logistic regression and repeated holdouts weighted quantile sum (WQS) regression analyses, respectively. Finally, we performed a sex-stratified analysis to explore sex-specific associations.

RESULTS

The sex-stratified multivariable logistic regression analysis indicated that in male fetal, cobalt (Co) (OR: 0.60, 95 % CI: 0.38, 0.92) was negatively associated with the high-growth BPD-SD scores trajectory. In contrast, Co (OR: 2.39, 95 % CI: 1.40, 4.45) showed a positive association in female fetal. Results from the WQS showed that early pregnancy metal mixture exposure was associated with BPD-SD scores at 16, 34, and 38 weeks in female fetal. The results highlighted Zn and Co as key metals associated with high-growth BPD SD-scores trajectory. We also identified a significant interaction between early pregnancy metal mixtures and sex on high-growth BPD SD-scores trajectories. The WQS*sex interaction term had a mean odds ratio of 1.271 (95 % CI: 1.027, 1.619).

CONCLUSION

This study suggests that exposure to prenatal metal mixtures affects fetal intrauterine growth trajectories with sexual dimorphism.

Effects of photodegradation on the composition characteristics and metal binding behavior of sediment-derived dissolved organic matter (SDOM) in nansi lake, China

Sediment-derived dissolved organic matter (SDOM) is instrumental in the cycling of nutrients and heavy metals within lakes, influencing ecological balance and contaminant distribution. Given the influence of photodegradation on the alteration and breakdown of SDOM, further understanding of this process is essential. In this research, the properties of the SDOM photodegradation process and its metal-binding reactions in Nansi Lake were analyzed using the EEM-PARAFAC and 2D-SF/FTIR-COS techniques. Our study identified three sorts of humic-like components and one protein-like component in SDOM, with the humic-like material accounting for 71.3 ± 5.19% of the fluorescence intensity (Fmax). Photodegradation altered the abundance and structure of SDOM, with a 41.6 ± 5.82% decrease in a280 and a 29.1 ± 9.31% reduction in Fmax after 7 days, notably reducing the protein-like component C4 by 54.0 ± 5.17% and the humic-like component C2 by 48.5 ± 2.54%, which led to SDOM being formed with lower molecular weight and aromaticity. After photodegradation, the LogKCu values for humic-like and protein-like substances decreased (humic-like C2: LogKCu: 1.35 ± 0.10-1.11 ± 0.15, protein-like C4: 1.49 ± 0.14-1.29 ± 0.34), yet the preferential binding sequence of protein-like materials and specific functional groups with Cu2+ such as aliphatic C-OH, amide (I) C=O and polysaccharide C-O groups remained unaltered. Our results enhance the knowledge of light-induced SDOM alterations and offer insights into SDOM-metal interactions in aquatic ecosystems.

Distribution, mobilization, risk assessment and source identification of heavy metals and nutrients in surface sediments of three urban-rural rivers after long-term water pollution treatment

Sediments are critical pollution carriers in urban-rural rivers, which can threaten the water quality of the river and downstream lakes for a long time. However, it is still not clear whether conventional water pollution treatments could abate sediment pollution or not. In this study, heavy metals (HMs) and nutrient salts in the surface sediments and overlying water were investigated after decades' water pollution treatment in three urban-rural rivers. HM speciation was determined by the sequential extraction; diffusion fluxes were estimated using Fick's first law; HM ecological risk and nutrient pollution were evaluated; and pollution sources were identified by statistical analysis and GIS. The results showed that the HMs and nutrients were extremely serious in the urban regions. The accumulation level of Pb, Cu and Cd in the sediments of the three rivers were all much higher than the soil background value, and the labile fractions accounted for high proportions (57 % for Pb, 55 % for Cu and 43 % for Cd), which could be easily eluate from the sediments and caused hazards to the aquatic environment. The sediment diffusion fluxes of HMs and ammonia nitrogen were mostly positive, which indicated these sites currently released these pollutants from sediment to overlying water. Cd, Pb, Cu and Cr may mainly originate from industrial discharge and domestic sewage, while Cr was also greatly affected by crustal weathering; nutrient pollution may originate from agricultural activities and domestic sewage. Our study demonstrated that after decades' conventional water treatment in these rivers, the sediment pollution was still in a serious level with high ecological risk, and Cd was the dominant pollutant. At present, the external point source pollution has been effectively controlled, thus, the in-depth understanding of the sediment pollution characteristics after long-term water treatment could provide a scientific basis for the accurate elimination of river pollution.

Heavy metal and persistent organic pollutant profile of sediments from marine protected areas: the northern Persian Gulf

Marine protected areas (MPAs) are one of the policy tools to support marine biodiversity conservation and sustainable use of marine resources. The distribution, sources, and ecological risk assessment of persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbon (PAHs), total petroleum hydrocarbons (TPHs), polychlorinated biphenyls (PCBs), and heavy metals (HMs) in sediments of MPAs in the northern Persian Gulf, were evaluated for the first time in this study. The Σ16PAHs ranged from 4.65 to 20.86 μg/kg dry weight (dw). The molecular ratios and ring's pattern of PAHs suggested a mixed origin with a predominance of pyrogenic sources. The TPH concentration varied from 5.21 to 17.90 μg/g dw. Ecological risk assessment suggested that sediment samples in Bushehr Province's MPAs can be categorized as medium risk. The mean concentration of ∑18PCB was 0.345-0.419 ng/g dw, and the main components correspond to PCB-77, PCB-105, PCB-81, PCB-101, and PCB-114. The mean concentration of As, Co, Cr, Ni, V, Mg, Pb, Zn, Cu, Al, and Fe varied from 4.79 to 9.69, 2-12, 39-142, 18-90, 15-58, 184-425, 7-45.9, 6-42.4, 4-20 μg/g dw, 0.75-4.12%, and 0.35-1.62%, respectively. Multivariate analysis, such as principal component analysis (PCA) and cluster analysis (CA), coupled with correlation coefficient analysis, was used to analyze the analytical data and to identify possible pollution sources. The results of this study provided the background information on the extent of POP contamination in the sediment and highlighted the need to further control pollution in MPAs.

Application of high-resolution techniques in the assessment of the mobility of Cr, Mo, and W at the sediment-water interface of Nansi Lake, China

There are few studies on the simultaneous behavior of chromium (Cr), molybdenum (Mo), and tungsten (W) belonging to group VIB of the periodic table. Herein, based on high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) technology, the vertical distribution characteristics of DGT-labile and soluble Cr, Mo, and W in two lakes of Nansi Lake (Weishan Lake and Dushan Lake) were analyzed. In addition, the net diffusion fluxes and R-value (CDGT/Csol) were used to evaluate the mobility and release risk of metals at the sediment-water interface. The results showed that the DGT-labile concentrations of the three metal elements (Cr, Mo, and W) in Weishan Lake were higher than those in Dushan Lake, both in overlying water and sediment. This is mainly due to the dredging of the Dushan Lake area, which can permanently remove the polluted sediment in the lake. Meanwhile, the exogenous input is relatively high near the tourist area of Weishan Island. The net diffusion fluxes indicate that the W has a potential release risk of diffusion to the overlying water in Dushan Lake. The release of Cr, Mo, and W is thought to be related to the reductive dissolution of Fe/Mn (hydr)oxides based on Pearson correlation coefficients. The R-values of Cr and W indicate that Cr and W belong to the partial continuity case. The R-value of Mo was lower than the minimum value, meaning that Mo belongs to the single diffusion type and it is difficult for Mo sediments to supply pore water.

Role of the tyrosine aminotransferase AccTATN gene in the response to pesticide and heavy metal stress in Apis cerana cerana

Tyrosine aminotransferase (TATN) is the first enzyme involved in the metabolic degradation of tyrosine, and it plays an important role in tyrosine detoxification and helps the body resist oxidative damage. However, the function of TATN in Apis cerana cerana (A. c. cerana) remains unclear. To explore the role of TATN in the response to pesticide and heavy metal stress in A. c. cerana, AccTATN was isolated and identified. AccTATN was highly expressed in the integument and the adult stage. Exposure to multiple pesticides and heavy metal stress upregulated AccTATN expression. RNA interference experiments showed that silencing AccTATN reduced the resistance of A. c. cerana to glyphosate and avermectins stress. The expression of antioxidant-related genes and the activity of antioxidant enzymes were reduced after AccTATN was silenced, leading to the accumulation of oxidative damage. Overexpression of the recombinant AccTATN protein in a prokaryotic system also confirmed its role in heavy metal stress and improved antioxidant capacity. Our study showed that AccTATN may promote resistance to pesticide and heavy metal stress by regulating the antioxidant capacity of A. c. cerana. This study provides a valuable theoretical basis for A. c. cerana conservation.

Interactions among heavy metals and methane-metabolizing microorganisms and their effects on methane emissions in Dajiuhu peatland

Peatlands play a crucial role in mediating the emissions of methane through active biogeochemical cycling of accumulated carbon driven by methane-metabolizing microorganisms; meanwhile, they serve as vital archives of atmospheric heavy metal deposition. Despite many edaphic factors confirmed as determinants to modulate the structure of methanotrophic and methanogenic communities, recognition of interactions among them is limited. In this study, peat soils were collected from Dajiuhu peatland to assess the presence of heavy metals, and methanotrophs and methanogens were investigated via high-throughput sequencing for functional genes mcrA and pmoA. Further analyses of the correlations between methane-related functional groups were conducted. The results demonstrated that both methane-metabolizing microorganisms and heavy metals have prominent vertical heterogeneity upward and downward along the depth of 20 cm. Pb, Cd, and Hg strongly correlated with methanotrophs and methanogens across all seasons and depths, serving as forceful factors in structural variations of methanogenic and methanotrophic communities. Particularly, Pb, Cd, and Hg were identified as excessive elements in Dajiuhu peatland. Furthermore, seasonal variations of networks among methane-related functional groups and environmental factors significantly affected the changes of methane fluxes across different seasons. Concretely, the complicated interactions were detrimental to methane emissions in the Dajiuhu peatland, leading to the minimum methane emissions in winter. Our study identified the key heavy metals affecting the composition of methane-metabolizing microorganisms and linkages between seasonal variations of methane emissions and interaction among heavy metals and methane-metabolizing microorganisms, which provided much new reference and theoretical basis for integrated management of natural peatlands.

Evaluating the release risk of potentially toxic elements from sediments in the New Zhuzhao River Estuary of Nansi Lake, using high-resolution technology and sequential extraction

Potentially toxic elements (PTEs) re-release from sediment is an essential process in the sediment-water interface (SWI), especially for the influent river estuary as an important accumulation site. In this study, the diffusive gradient in thin films (DGT), high-resolution dialysis (HR-peeper) technique, and BCR sequential extraction were employed to evaluate the release risk of PTEs (As, Cu, Pb, Zn, Cd) in the New Zhuzhao River Estuary of Nansi Lake. Results showed that Cd existed primarily in the non-residual fraction (accounting for 59.87%), and the residual fractions of As, Cu, Pb, and Zn accounted for a greater proportion (12.65 to 33.07%). The mobility of Cd was the highest with a risk assessment code of 33.53% reaching the medium risk category. The resupply capacity calculated by C_DGT/C_Dis showed that As was the largest, with an average value of 0.43, indicating the strongest release capacity of As from the sediment to pore water. Furthermore, the diffusive fluxes using DGT and HR-peeper showed that As possesses a much higher potential to release upward overlying water than other elements.

Understanding the Heavy Metal Pollution Pattern in Sediments of a Typical Small- and Medium-Sized Reservoir in China

Heavy metal pollution in sediments is a common environmental issue in small- and medium-sized reservoirs not only in China but also worldwide; however, few interpretations of the pollution pattern exist. Based on the analyses of accumulation characteristics, ecological risks, and source apportionments of eight heavy metals (As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn) in sediments, we derived a paradigm to describe the pollution pattern of heavy metals in sediments of a typical small- and medium-sized Tongjiqiao Reservoir. The results showed high levels of Cd, Hg, and As pollutants in the surface and upper sediment layers of the pre-dam area. Additionally, As, Cd, Hg, and Pb pollutants peaked in the middle layers of the inflow area, indicating a high ecological risk in these areas. The positive matrix factorization results implied that industrial, agricultural, and transportation activities were the main sources of heavy metals. The heavy metal pollution pattern exhibited three distinct stages: low contamination, rapid pollution, and pollution control. This pattern explains the heavy metal pollution process in the sediments and will provide scientific guidance for realizing the green and sustainable operation and development of the reservoir.

Effects of hydrological connectivity project on heavy metals in Wuhan urban lakes on the time scale

Metal pollution in lakes threatens the ecological environment and human health. When environmental conditions change, heavy metals (HMs) in lake sediments can cause secondary pollution. At present, the implementation of the Hydrological Connectivity Project (HCP) is a significant means of lake governance. In this study, the accumulation, potential ecological risk, and sources of HMs in Four lakes (Houguan Lake, Tangxun Lake, Moshui Lake, and Chen Lake) in Wuhan city were compared before and after the completion of the HCP. The results indicated that the HCP reduced the enrichment factor of HMs and the potential ecological risk in the heavily polluted Moshui Lake but caused secondary pollution in the less polluted Houguan Lake. Moreover, the degree of purification of lakes that took a longer time to complete the HCP (Moshui Lake) was significantly higher than that of lakes with a shorter HCP completion time (Tangxun Lake). Water exchange caused by the HCP leading to exchange of the primary pollution source between Houguan Lake and Moshui Lake to a certain extent. This study provides a reference for evaluating the implementation effect of the HCP on HM pollution in lakes and for future governance planning.

Maternal exposure to metal mixtures during early pregnancy and fetal growth in the Jiangsu Birth Cohort, China

Previous epidemiological studies have reported that prenatal exposure to metals might have influence on fetal growth. Most studies assessed the effect of individual metals, while the investigation on the relationship between multiple metal exposure and fetal growth is sparse. The objective of the present study is to assess the joint impact of metal mixtures on fetal growth during pregnancy. A total of 1275 maternal-infant pairs from the Jiangsu Birth Cohort (JBC) Study were included to investigate the effect of maternal metal exposure on fetal biometry measures at 22-24, 30-32, and 34-36 weeks of gestation. Lead (Pb), arsenic (As), cadmium (Cd), mercury (Hg), chromium (Cr), vanadium(V), thallium (Tl) and barium (Ba) were measured by inductively coupled plasma mass spectrometry (ICP-MS) in maternal urine samples collected in the first trimester. We used general linear models and restricted cubic splines to test dose-response relationships between single metals and fetal growth. The weighted quantile sum (WQS) models were then applied to evaluate the overall effect of all these metals. We observed inverse associations of exposure to Pb, V and Cr with estimated fetal weight (EFW) at 34-36 weeks of gestation. Notably, maternal exposure to metal mixtures was significantly associated with reduced EFW at 34-36 weeks of gestation after adjusting for some covariates and confounders (aβ -0.05 [95% CI: 0.09, -0.01], P = 0.023), and this association was mainly driven by Cr (30.41%), Pb (23.92%), and Tl (15.60%). These findings indicated that prenatal exposure to metal mixtures might impose adverse effects on fetal growth.

Heavy metals in lake surface sediments in protected areas in Poland: concentration, pollution, ecological risk, sources and spatial distribution

This paper presents the state and spatial distribution of surface sediment contamination of 77 lakes in Poland by Cr, Ni, Cd, Pb, Zn, and Cu. The analyzed lakes were located within a network of nature protection areas in the territory of the European Union (EU). Spatial distribution of the heavy metals (HMs), factors favoring the delivery/accumulation of HMs in surface sediments, and pollution sources were analyzed. The results indicate the contamination of lake sediments by HMs, but the potentially toxic effects of HMs are only found in single lakes. The spatial distribution of Cr indicates predominant impacts of point sources, while for Pb, Ni, and Zn, the impact of non-point sources. The analysis showed the presence of areas with very high values of particular HMs (hot spots) in the western part of Poland, while a group of 5 lakes with very low values of Ni, Pb, and Zn (cold spots) was identified in the central part of Poland. Principal component analysis showed that presence of wetlands is a factor limiting HMs inflow to lakes. Also, lower HMs concentrations were found in lake surface sediments located in catchments with a higher proportion of national parks and nature reserves. Higher HMs concentrations were found in lakes with a high proportion of Special Protection Areas designated under the EU Birds Directive. The positive matrix factorization analysis identified four sources of HMs. High values of HMs concentrations indicate their delivery from industrial, urbanized, and agricultural areas. However, these impacts overlap, which disturbs the characteristic quantitative profiles assigned to these pollution sources.

Co-exposure of potentially toxic elements in wheat grains reveals a probabilistic health risk in Southwestern Guizhou, China

Bijie is located at a typical karst landform of Southwestern Guizhou, which presented high geological background values of potentially toxic elements (PTEs). Recently, whether PTE of wheat in Bijie is harmful to human health has aroused people's concern. To this end, the objectives of this study are to determine the concentrations of PTE [chromium (Cr), nickel (Ni), arsenic (As), lead (Pb), cadmium (Cd), and fluorine (F)] in wheat grains, identify contaminant sources, and evaluate the probabilistic risks to human beings. A total of 149 wheat grain samples collected from Bijie in Guizhou were determined using the inductively coupled plasma mass spectrometer (ICP-MS) and fluoride-ion electrode methods. The mean concentrations of Cr, Ni, As, Cd, Pb, and F were 3.250, 0.684, 0.055, 0.149, 0.039, and 4.539 mg/kg, respectively. All investigated PTEs met the standard limits established by the Food and Agriculture Organization except for Cr. For the source identification, Cr and Pb should be originated from industry activities, while Ni, As, and Cd might come from mixed sources, and F was possibly put down to the high geological background value. The non-carcinogenic and carcinogenic health risks were evaluated by the probabilistic approach (Monte Carlo simulation). The mean hazard quotient (HQ) values in the three populations were lower than the safety limit (1.0) with the exception of As (children: 1.03E+00). However, the mean hazard index (HI) values were all higher than 1.0 and followed the order: children (2.57E+00) > adult females (1.29E+00) > adult males (1.12E+00). In addition, the mean carcinogenic risk (CR) values for Cr, As, Pb, and Cd in three populations were all higher than 1E-06, which cannot be negligible. The mean threshold CR (TCR) values were decreased in the order of children (1.32E-02) > adult females (6.61E-03) > adult males (5.81E-03), respectively, all at unacceptable risk levels. Moreover, sensitivity analysis identified concentration factor (C _W ) as the most crucial parameter that affects human health. These findings highlight that co-exposure of PTE in wheat grains revealed a probabilistic human health risk. Corresponding measures should be undertaken for controlling pollution sources and reducing the risks for the local populace.

Spatiotemporal changes of eutrophication and heavy metal pollution in the inflow river system of Baiyangdian after the establishment of Xiongan New Area

Pollution in inflow rivers seriously endangers the water environment in downstream lakes. In this study, an inflow river system of the Baiyangdian-Fuhe river system (FRS) was investigated to display timely pollution patterns of eutrophication and heavy metals after the establishment of Xiongan New Area, aiming to reveal the weak parts in current pollution treatments and guide the further water quality management. The results showed that the pollution of eutrophication was worse than the heavy metals in FRS, with serious eutrophic parameters of ammonia nitrogen (NH₄ ⁺-N) and chemical oxygen demand (COD). There were greatly spatiotemporal variations of the pollution in FRS. (1) Concentrations of NH₄ ⁺-N and total phosphorus were all higher in summer and autumn, whereas, COD contents were higher in spring; the water quality index (WQI) of eutrophication linearly increased along FRS in summer and autumn, with pollution hotspots around the estuary area. (2) The pollution levels of plumbum exceeded cadmium (Cd) and chromium (Cr) but without strongly spatiotemporal changes; however, Cd and Cr in the town area and Cd in spring showed higher concentrations; the WQI of heavy metals showed single peak curves along FRS, with significantly higher values around the town area. Additionally, the four potential pollution sources: domestic sewage, traffic pollution, agricultural wastewater and polluted sediments were identified based on the pollution patterns and pollutant associations. These findings demonstrated current treatments failed to eliminate the pollution in some hotspots and periods, and the in-depth understanding of the pollution spatiotemporal patterns in this study, especially the pollution hotspots, serious periods and potential sources, are crucial to furtherly develop spatiotemporally flexible pollution treatment strategies.