Spatial and seasonal characteristics of dissolved heavy metals in the surface seawater of the Yellow River Estuary, China

Hydrodynamics and dissolved organic matter components shaped the fate of dissolved heavy metals in an intensely anthropogenically disturbed estuary

Anthropogenic activities and natural erosion caused abundant influx of heavy metals (HMs) and organic matter (OM) into estuaries characterized by the dynamic environments governed by tidal action and river flow. Similarities and differences in the fate of HM and OM as well as the influences of OM on HMs remain incomplete in estuaries with seasonal human activity and hydrodynamic force. To address this gap, dissolved HMs (dHMs) and fluorescence dissolved OM (FDOM) were investigated in the Pearl River Estuary, a highly seasonally anthropogenic and dynamic estuary. It aimed to elucidate the effects of hydrodynamic conditions and DOM on the seasonal fate of dHMs via the multivariate statistical methods. Our findings indicated dHMs and FDOM exhibited consistently higher levels in the upper estuarine and coastal waters in both seasons, predominantly controlled by the terrestrial/anthropogenic discharge. In the wet season, dHMs and humic-like substances (HULIS) were positively correlated, showing that dHMs readily combined with HULIS. This association led to a synchronous decrease offshore along the axis of the estuary and the transport following the river plume in the surface affected by the salt wedge. Contrarily, dHMs were prone to complex with protein-like components impacted by the hydrodynamics during the dry season. Principal component analysis (PCA) results revealed the terrestrial/anthropogenic inputs and the fresh-seawater mixing process were the most crucial factors responsible for the fate of dHM in wet and dry seasons, respectively, with DOM identified as a secondary but significant influencing factor in both seasons. This study holds significance in providing valuable insights into the migration, transformation, the ultimate fate of dHMs in anthropogenically influenced estuaries, as well as the intricate dynamics governing coastal ecosystems.

The influences of Yellow River input and nutrient dynamics on colloidal Fe migration in the Bohai Sea, China

The coupling relationship between the <1 kDa, 1-3 kDa, 3-10 kDa, 10-100 kDa, and 100 kDa-0.45 μm Fe fractions and the environmental factors in the Bohai Sea (BS) was investigated. The 1-100 kDa Fe in the surface water exhibited a non-conservative phenomenon during the river-sea mixing process, which was related to the removal of colloidal Fe via flocculation during this process. For the bottom water, the ligands released by the sediments may form additions to the <100 kDa Fe. The COC and DOC were mainly closely related to the behavior of the Fe in the bottom water. The <1 and 3-10 kDa Fe was mainly significantly positively correlated with the DOC, while the <100 kDa-0.45 μm Fe was significantly negatively correlated with the DOC. <100 kDa LMW colloidal Fe exhibited more synergistic behavior with easily absorbed ammonium salts.

Spatial distribution, compositional pattern, and source apportionment of colloidal trace metals in the coastal water of Shandong Peninsula, northeastern China

The Shandong Peninsula (SP) is the largest peninsula in China hosting rich economic and agricultural activities. In this study, we investigated the behavior of dissolved Mn, Fe, Cu, Zn, Cd, and Pb and their colloidal phases in the coastal and estuarine areas of SP. Pb and Zn had the highest contamination factors of 0.22-10.15 and 0.90-4.41, respectively. The <1 kDa accounted for 23-57 % of the total dissolved phase. Mn, Fe, Cu, Zn, Cd, and Pb were more likely to bind to 100 kDa-0.45 μm colloids (21-57 %). For colloidal Fe and Cu, the adsorption-release behavior had more significant effects on their dynamics. In contrast, the changes in colloidal Mn, Cd, and Pb were mainly controlled by the combined influence of temperature, dissolved oxygen, and microbial activity. However, the 1-3 kDa Zn exhibited a greater pH-dependent dispersion and was significantly positively correlated with it.

The role of the macroalgae Ulva lactuca on the cellular effects of neodymium and mercury in the mussel Mytilus galloprovincialis

Rare earth elements (REEs) are increasingly being studied mainly due to their economic importance and wide range of applications, but also for their rising environmental concentrations and potential environmental and ecotoxicological impacts. Among REEs, neodymium (Nd) is widely used in lasers, glass additives, and magnets. Currently, NdFeB-based permanent magnets are the most significant components of electronic devices and Nd is used because of its magnetic properties. In addition to REEs, part of the environmental pollution related to electrical and electronic equipment, fluorescent lamps and batteries also comes from mercury (Hg). Since both elements persist in ecosystems and are continuously accumulated by marine organisms, a promising approach for water decontamination has emerged. Through a process known as sorption, live marine macroalgae can be used, especially Ulva lactuca, to accumulate potential toxic elements from the water. Therefore, the present study aimed to evaluate the cellular toxicity of Nd and Hg in Mytilus galloprovincialis, comparing the biochemical effects induced by these elements in the presence or absence of the macroalgae U. lactuca. The results confirmed that Hg was more toxic to mussels than Nd, but also showed the good capability of U. lactuca in preventing the onset of cellular disturbance and homeostasis disruption in M. galloprovincialis by reducing bioavailable Hg levels. Overall, the biochemical parameters evaluated related to metabolism, antioxidant and biotransformation defences, redox balance, and cellular damage, showed that algae could prevent biological effects in mussels exposed to Hg compared to those exposed to Nd. This study contributes to the advancement of knowledge in this field, namely the understanding of the impacts of different elements on bivalves and the crucial role of algae in the protection of other aquatic organisms.

Distribution, seasonal variation and influencing factors of total dissolved inorganic arsenic in the middle and lower reaches of the Yellow River

The concentrations of dissolved arsenate in natural water has an important impact on human health. The distributions, seasonal variation and major influencing factors of total dissolved inorganic arsenic (TDIAs) were studied in the Yellow River. The concentrations of TDIAs in the middle and lower reaches of the Yellow River ranged from 4.3 to 42.4 nmol/L, which met the standards for drinking water of WHO. The seasonal variation of TDIAs concentration in the middle and lower reaches of the Yellow River was highest in summer, followed by autumn and winter, and lowest in spring. The influencing factors of TDIAs concentration in the middle and lower reaches of the Yellow River mainly include the hydrological conditions, topographical variation, the adsorption and desorption of suspended particulate matter (SPM) and the intervention of human activities. The absorption of TDIAs by phytoplankton in the Xiaolangdi Reservoir (XLD) is an important factor affecting its distributions and seasonal variation. The annual flux of TDIAs transported from the Yellow River into the Bohai Sea ranged from 1.1 × 105 to 4.5 × 105 mol from 2016 to 2018, which is lower than the flux in 1985 and 2009. The carcinogenic risks (CR) of TDIAs for children and adults were all within acceptable levels (<10-6).

Distribution, ecological, and health risk assessment of trace elements in the surface seawater along the littoral of Tangier Bay (Southwestern Mediterranean Sea)

In the current study, an environmental assessment of surface seawater in Tangier Bay was conducted by analyzing physicochemical parameters and trace elements, such as As, Cr, Zn, Cd, Pb, and Cu. The results showed mean concentrations (μg/l) of 22.50 for As, 0.46 for Cr, 8.57 for Zn, 15.41 for Cd, 0.23 for Pb, and 1.83 for Cu. While most trace elements met the guidelines, elevated levels of Cd raised concerns about long-term exposure. Pollution indices, including the contamination factor, degree of contamination, and water quality index, indicate the impact of human activities, dividing sites into arsenic-cadmium contamination, wastewater influence, and low pollution levels. Statistical methods, such as ANOVA, revealed no significant differences in trace element levels across the bay. PCA and HCA revealed that Cr, Cu, and Zn originated from common anthropogenic sources, whereas Pb and Cd originated from distinct sources. As indicates that natural geological processes influence its origin.

Bacterial community in the metal(loid)-contaminated marine vertical sediments of Jinzhou Bay: Impacts and adaptations

Metal(loid) discharge has led to severe coastal contamination; however, there remains a significant knowledge gap regarding its impact on sediment profiles and depth-resolved bacterial communities. In this study, geochemical measurements (pH, nutrient elements, total and bioavailable metal(loid) content) consistently revealed decreasing nitrogen, phosphorus, and metal(loid) levels with sediment depth, accompanied by reduced alpha diversity. Principal coordinate analysis indicated distinct community compositions with varying sediment depths, suggesting a geochemical influence on diversity. Ecological niche width expanded with depth, favoring specialists over generalists, but both groups decreased in abundance. Taxonomic shifts emerged, particularly in phyla and families, correlated with sediment depth. Microbe-microbe interactions displayed intricate dynamics, with keystone taxa varying by sediment layer. Zinc and arsenic emerged as key factors impacting community diversity and composition using random forest, network analysis, and Mantel tests. Functional predictions revealed shifts in potential phenotypes related to mobile elements, biofilm formation, pathogenicity, N/P/S cycles, and metal(loid) resistance along sediment profiles. Neutral and null models demonstrated a transition from deterministic to stochastic processes with sediment layers. This study provides insights into the interplay between sediment geochemistry and bacterial communities across sediment depths, illuminating the factors shaping these ecosystems.

Interconnected environmental challenges: heavy metal-drug interactions and their impacts on ecosystems

Industrial expansion and inadequate environmental safety measures are major contributors to environmental contamination, with heavy metals (HMs) and pharmaceutical waste playing crucial roles. Their negative effects are most noticeable in aquatic species and vegetation, where they accumulate in tissues and cause harmful results. Interactions between HMs and pharmaceutical molecules result in the production of metal-drug complexes (MDCs), which have the potential to disturb diverse ecosystems and their interdependence. However, present studies frequently focus on individual pollutants and their effects on specific environmental parameters, leaving out the cumulative effects of pollutants and their processes across several environmental domains. To address this gap, this review emphasizes the environmental sources of HMs, elucidates their emission pathways during anthropogenic activities, investigates the interactions between HMs and pharmaceutical substances, and defines the mechanisms underlying the formation of MDCs across various ecosystems. Furthermore, this review underscores the simultaneous occurrence of HMs and pharmaceutical waste across diverse ecosystems, including the atmosphere, soil, and water resources, and their incorporation into biotic organisms across trophic levels. It is important to note that these complex compounds represent a higher risk than individual contaminants.

Entropy-weighted water quality index, hydrogeochemistry, and Monte Carlo simulation of source-specific health risks of groundwater in the Morava River plain (Serbia)

Population growth, urbanization, industry, floods, and agriculture globally degrade groundwater in river plains, necessitating action for its quality assessment and management. Hence, a comprehensive methodology, including hydrogeochemical facies (Piper, Gibbs), irrigation indices (SAR, Wilcox), entropy-weighted water quality index (EWQI), positive matrix factorization (PMF), and Monte Carlo simulation of source-specific health risks was used in this study to analyze groundwater in the Morava river plain (Serbia). The results revealed a prevalent Ca-Mg-HCO3 groundwater type, influenced by water-rock interactions. Although groundwater was found suitable for irrigation, only 66.7 % of the samples were considered drinkable. Agricultural activities, natural processes, and municipal wastewater were identified as primary pollution sources. The incremental lifetime cancer risk (ILCR) and hazard index (HI) threshold exceedance for adults and children ranged from 8.5 % to 39 % of the samples, with arsenic identified as the most risk-contributing contaminant. These findings provide valuable insights for researchers studying groundwater vulnerability in river plains.

Risk assessment of trace metals and polycyclic aromatic hydrocarbons in seawater of typical bays in the Bohai Sea

The ecological risks of trace metals (Cu, Zn, As, Cd, Pb, and Hg) and PAHs in seawater from three typical bays of the Bohai Sea (the Liaodong Bay, Bohai Bay, and Laizhou Bay) were comprehensively assessed by recompiling 637 sites. Results highlighted that scrutiny should be given to the ecological risks of Cu (3.80 μg/L) in the Bohai Bay and Hg (0.23 μg/L) in the Laizhou Bay. Conversely, the Liaodong Bay exhibited negligible ecological risks related to trace metals. The risks of ΣPAHs in the Liaodong Bay, Bohai Bay, and Laizhou Bay were moderate, with mean concentrations of 368.16 ng/L, 731.93 ng/L, and 187.58 ng/L, respectively. The source allocation of trace metals and PAHs required consideration of spatial variability and anthropogenic factors, which greatly affected the distribution and composition of these pollutants. The combined ecological risks in the Bohai Bay (6.80 %) and Laizhou Bay (5.43 %) deserved more attention.

Spatial and temporal dynamics and fluxes estimation of manganese fractions in sediments from the Pearl River Estuary, southern China

Sequential extraction was used to study the historical dynamics and fluxes of the chemical fractions of manganese (Mn) in sediments collected from the Pearl River Estuary (PRE), southern China. Results revealed that the proportion of Mn associated with different fractions decreased in the order of acid-soluble fraction (F1) > reducible fraction (F2) > residual fraction (F4) > oxidizable fraction (F3). F1 (47%) was the dominant Mn fraction, indicating the strong bioavailability of Mn to aquatic organisms in the PRE. In addition, the Mn fraction F2 was present at an average rate of 27.93 % in surface sediments, indicating that it could be mobilized when environmental conditions become increasingly reducing or oxidizing. The decline in Mn fraction fluxes after 2006 indicated that the region has partially decreased due to the removal of heavily polluting industries and effective control of sewage discharge.

Seasonal differences in trace metal concentrations in the major rivers of the hyper-arid southwestern Andes basins of Peru

The southern rivers of Peru originate in the Andes Mountains and flow in a southwestern direction to the Pacific Ocean through one of the most hyper-arid regions of the world. During each sub-equatorial summer from December to February, rains and snow melt in the Andes increase the streamflow in these rivers, even as they pass through the 100 km arid zone to the ocean. This study quantified seasonal dynamics of 34 trace metal elements (TM) and other constituent concentrations in four southern river basins of Peru (Chili-Quilca, Tambo, Camana-Majes-Colca, and Ocoña) during 2019-2020. Consistent with previous studies, we observed that: (1) the river water in the southern basins had relatively high concentrations of B, As, Fe, Al, Mn, P, Pb and Ni, with As the most ubiquitous toxic TM in all the basins, often detected at concentrations surpassing Peruvian and USEPA regulated concentrations; and (2) basins with the most to least toxic TM contamination were the Tambo > Chili-Quilca > Camana-Majes-Colca > Ocoña. Seasonal streamflow strongly influenced the concentrations of twenty TM, with 15 TM (Al, Au, Ba, Cd, Co, Cu, Fe, Gd, Mn, Ni, P, Pb, Ti, Yb and Zr) consistently higher in the wet season, and with As, B, Ge, Li, and Pd higher in the dry season. Our results improve the understanding of seasonal variability and vulnerability in western Andes superficial water sources, which are highly influenced by both local geogenic and anthropogenic conditions. A Spanish translation of this paper is available in the online Supplementary Material.

Plankton diversity and its heavy metal content in Ratai Bay of Pesawaran district, Lampung, Indonesia

Artisanal and small-scale gold mining (ASGM) activity in Way Ratai River produces heavy metal wastes; therefore, further information regarding heavy metal concentrations in the water was needed, especially in plankton samples. Furthermore, the determination of plankton diversity was also carried out in the waters of Way Ratai to determine the bioconcentration factor (BCF). Eight sampling sites were chosen along the river reaching the coast of Way Ratai. The research was conducted in November 2020 and March 2021. Ten heavy metals, Ag, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn that are commonly found in mining areas, were determined in the water and plankton samples by using ICP-OES. The results indicated that the highest concentration found was Fe in plankton samples (0.725 mg/L in the river and 1.294 mg/L on the coast). Meanwhile, contents of Cd, Cu, Fe, Mn, and Zn in the river exceeded the predetermined water quality standards, while Ag and Pb metals were not detected. The Cd, Cr, Cu, Pb, and Zn content in seawater also exceeded quality standards. The highest BCF value (12.96) was found for Fe at station G, whereas the lowest BCF value (0.13) was found for Ag at stations G and H.

Assessment of metal contaminants along the Bay of Bengal - Multivariate pollution indices

The spatial concentration of heavy metals (Mn, Ni, Cu, Co, Zn, Cd, and Pb) was studied in coastal areas (n = 9) including water (n = 27) and sediment (n = 27) in the Palk Bay, India to understand the metal pollution due to prevailing natural and anthropogenic activities. Pollution indices like metal index (MI), geoaccumulation index (Igeo), contamination factor (CF), pollution load index (PLI) and potential ecological risk (PER) were calculated based on the background/reference value. The values of MI index indicated that water was free of metals, whereas Igeo, CF, PLI and PER indicated moderate contamination of sediment in monsoon. Cadmium concentrations were the highest irrespective of the indices (Igeo: 0.04-1.42, Cf: 0.36-0.74, PLI: 0.36-0.74, and PER: 76.89-143.36) indicating moderate pollution. The Principal Component Analysis (PCA) affirmed that Cd was positively correlated with stations indicating anthropogenic sources of Cd contamination.

Saltwater intrusion regulates the distribution and partitioning of heavy metals in water in a dynamic estuary, South China

The mixing processes of fresh-salt water in estuarine and coastal regions have a substantial impact on the characteristics of heavy metals. A study was conducted in the Pearl River Estuary (PRE), located in South China, to examine the distribution and partitioning of heavy metals and the factors that influence their presence. Results showed that the hydrodynamic force, caused by the landward intrusion of the salt wedge, was the major contributor to the aggregation of heavy metals in the northern and western PRE. Conversely, metals were diffused seaward at lower concentrations along the plume flow in surface water. The study found that some metals, including Fe, Mn, Zn and Pb, were significantly higher in surface water than in bottom water in eastern waters, but the reverse was true in the southern offshore area, where limited mixing hindered the vertical transfer of metals in the water column. The partitioning coefficients (K_D) of metals varied, with Fe exhibiting the highest K_D (1038 ± 1093 L/g), followed by Zn (579 ± 482 L/g) and Mn (216 ± 224). The highest K_D values of metals in surface water were observed in the west coast, while the highest K_D in bottom water was found in eastern areas. Furthermore, re-suspension of sediment and the mixing of seawater and freshwater offshore, caused by seawater intrusion, resulted in the partitioning of Cu, Ni and Zn towards particulate phases in offshore waters. This study provides valuable insights into the migration and transformation of heavy metals in dynamic estuaries influenced by the interaction of freshwater and saltwater and highlights the importance of continued research in this field.

Potential risks, source apportionment, and health risk assessment of dissolved heavy metals in Zhoushan fishing ground, China

Dissolved heavy metal pollution in the ocean is one of the most severe environmental concerns; however, the potential sources of heavy metals and the resulting health risks are not fully understood. To explore the distribution characteristics, source apportionment, and health risks of dissolved heavy metals (As, Cd, Cu, Hg, Pb, and Zn) in the Zhoushan fishing ground, this study analyzed heavy metals in surface seawater during the wet and dry seasons. The concentrations of heavy metals varied greatly between seasons, and the mean concentration in the wet season was generally higher than that in the dry season. A positive matrix factorization model coupled with correlation analysis was applied to identify promising sources of heavy metals. Four potential sources (agricultural, industrial, traffic, atmospheric deposition, and natural sources) were identified as the determinants of the accumulation of heavy metals. The health risk assessment results revealed that non-carcinogenic risk (NCR) for adults and children were acceptable (HI < 1), and carcinogenic risk (CR) were at a low level (1 × 10^-6 < TCR ≤ 1 × 10^-4). The source-oriented risk assessment indicated that industrial and traffic sources were the main sources of pollution, contributing 40.7 % of NCR and 27.4 % of CR, respectively. This study proposes forming reasonable, effective policies to control industrial pollution and improve the ecological environment of Zhoushan fishing grounds.

Chemical hazard of robotic hull in-water cleaning discharge on coastal embryonic fish

In-water cleaning (IWC) involves the removal of biofilms and foulants from the hull of a ship using brush or water jet. During IWC, several factors associated with the harmful chemical contaminants release to the marine environment, which can create "hotspots" of chemical contamination in coastal areas. To elucidate the potential toxic effects of IWC discharge, we investigated developmental toxicity in embryonic flounder, which are sensitive life stage to chemical exposure. Zinc and copper were the dominant metals, while zinc pyrithione was the most abundant biocide associated with IWC discharge in two remotely operated IWC. Discharge from IWC carried by both remotely operated vehicles (ROVs) produced developmental malformations including pericardial edema, spinal curvature, and tail-fin defects. In an analyses of differential gene expression profiles (fold-change of genes with a cutoff < 0.05) as assessed by high-throughput RNA sequencing, genes associated with muscle development were commonly and significantly changed. The gene ontology (GO) of embryos exposed to IWC discharge from ROV A activities highly enriched muscle and heart development, while cell signaling and transport were evident in embryos exposed to IWC discharge of ROV B. We analyzed the gene network by significant GO terms. In the network, TTN, MYOM1, CASP3, and CDH2 genes appeared to be key regulators of the toxic effects on muscle development. In embryos exposed to ROV B discharge, HSPG2, VEGFA, and TNF genes related to the nervous system pathway were affected. These results shed light on the potential impacts of muscle and nervous system development in non-target coastal organisms exposed to contaminants found in IWC discharge.

Contamination, sources and health risks of potentially toxic elements in the coastal multimedia environment of South China

Coastal ecosystems are vulnerable to the accumulation of potentially toxic elements (PTEs), which pose a threat to marine ecosystems and human health. In this study, the concentrations of eight PTEs in a typical area of South China were analysed, and their distributions, seasonal variations, pollution degrees, potential health risks and sources in seawater, sediment and organisms were evaluated. The comprehensive pollution index (CPI), pollution load index (PLI), potential ecological risk index (PERI) and target hazard quotient (THQ) were applied to assess seawater, sediment and organism quality, respectively. The annual mean concentrations of Zn, Hg, Cr and As in the bottom seawater were higher than those in the surface water while those of Pb, Mn and Cu were higher in the surface seawater. The mean content of Hg was higher than the corresponding background value of that in China Shelf Sea sediment. Marine organisms have a high enrichment capacity for Cu, Zn, Cr, Hg, As and Mn in seawater. Based on CPI, the seawater was generally not polluted by PTEs. The PLI and PERI results demonstrated that Hg was the main contamination element in surface sediment. The total target hazard quotient (TTHQ) analysis illustrated that long-term consumption of some fish by children poses a noncarcinogenic health risk, while that risk to adults is negligible. Natural sources, agricultural activity sources, coal burning and industrial emission sources were the main sources of the PTEs in surface sediments according to positive matrix factorization (PMF) model.

Mercury levels in an environmentally protected estuarine area in Northeast Brazil: partitioning in the water column and transport to the ocean

In this study, total Hg concentrations (HgT) were determined in the suspended particulate matter (SPM) and the dissolved fraction of the water column to evaluate their behavior through a gradient of physical-chemical parameters in a continuum between rivers and the Serinhaém River estuary of the Pratigi Environmental Protection Area, a pristine environment without point sources of Hg contamination, located in Northeast Brazil. Twelve points were sampled, forming a river-estuary transect, and two samplings were carried out (April and September 2019). Significant spatial and temporal effects were detected only for particulate HgT and not for dissolved HgT. Considering both samplings, the mean HgT concentrations in SPM were 1112 ± 824 and 44 ± 33 ng·g^-1 in the river and estuary, respectively. Also, HgT concentrations in the dissolved fraction (1.61 ± 0.61 ng·L^-1) were below the limits established by environmental agencies (CONAMA = 2 μg∙L^-1 and USEPA = 1.4 μg·L^-1). Salinity and SPM concentrations were important predictors of HgT in the water column (R² = 0.81, p < 0.0001; R² = 0.56, p < 0.0001, respectively). Mercury transport to the ocean through SPM was 2 kg∙year^-1, 4000 times greater than the dissolved fraction.

Risk assessment and spatio-temporal distribution of dissolved trace metals in Swarna, Sharavati and Kali estuaries, South-West Coast of India

Trace metals act as a limiting nutrient and prerequisite for primary productivity in marine environments. The distribution of metals in dissolved phase along the salinity gradients of Swarna, Sharavati and Kali estuaries in southwestern India, during post and pre-monsoon seasons, were studied. We have investigated the behaviour of trace metals in the estuarine environment and their extent of impact on human health and ecosystem. The study revealed, non-conservative behaviour of dissolved Mn, Fe, Ni, Cd and Co in the estuaries. Whereas Cu behaved non-conservatively in post-monsoon and conservatively in pre-monsoon seasons. Risk assessment studies revealed that higher chronic daily intake (CDI) in humans, through dermal pathway, in Swarna and Sharavati estuaries during post-monsoon, whereas it was during pre-monsoon season in the Kali estuary. Hazard Index values for the studied metals in adults and children are below risk thresholds, though children are more prone to health risk through the dermal pathway.

Combining metal and sulfate isotopes measurements to identify different anthropogenic impacts on dissolved heavy metals levels in river water

Dissolved heavy metals (DHMs) contamination has raised global concern for ecological and human health development. Weathering of sulfide-bearing ore metals can produce acidic, sulfate-rich solutions in the presence of water and oxygen (O₂), and DHMs are released to deprave the river water quality. Sulfur and oxygen isotope signatures (δ³⁴S_SO4 and δ¹⁸O_SO4) could identify this pyrite-derived sulfate; however, it is yet not well known whether the δ³⁴S_SO4 and δ¹⁸O_SO4 values could limit the DHMs sources and illustrate anthropogenic impacts on DHMs along the river corridor. We tried to solve this problem through field works in the Luohe River and Yihe River, two tributaries of the Yellow River, China, where metal sulfide mine activities mostly occurred upstream, but agricultural and domestic behaviors concentrated in the lower plain reaches. In the Luohe River upper areas, δ³⁴S_SO4 values had negative correlations with concentrations of cadmium (Cd) (p < 0.01), nickel (Ni) (p < 0.05), molybdenum (Mo) (p < 0.01), uranium (U) (p < 0.01), and SO₄^2- (p < 0.01). However, as the δ³⁴S_SO4 values increased downstream in the Luohe River, concentrations of copper (Cu) (p < 0.05), mercury (Hg) (p < 0.05), Ni (p < 0.05), and SO₄^2- (p < 0.01) simultaneously elevated. The Bayesian Isotope Mixing Model (BIMM) results via δ³⁴S_SO4 values demonstrated 64.3%-65.3% of SO₄^2- from acid mine drainage (AMD) in the Luohe River's upper reaches and 63.5%-67.7% in the Yihe River's upper reaches, and about 33% from sewage and industrial effluents in the Luohe River's lower reaches and 27% in Yihe River's lower reaches. Our results confirmed the different anthropogenic impacts on the DHMs concentrations in Luohe River and Yihe River and provided a robust method for DHMs sources appointment and pollution management in river systems.

Human Health Risk Assessment of Heavy Metal Concentration in Seafood Collected from Pattani Bay, Thailand

A significant impact of marine pollution is the contamination of seafood which has raised concerns due to its potential human health risks. This current study investigated seasonal bioaccumulation of 9 heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in 14 commercially important seafood species, including 4 fish, 5 molluscs, and 5 crustacean species. Samples were collected from Pattani Bay, Pattani province, Thailand, during the dry (July 2020) and wet (February 2021) seasons. The edible samples were analyzed for heavy metal concentrations using a flame atomic absorption spectrophotometer. The bioaccumulation trend of heavy metals decreased in the sequence of molluscs > crustaceans > fish. The possible human health risks associated with heavy metal-contaminated seafood consumption were assessed. The parameters investigated for non-carcinogenic and carcinogenic were target hazard quotient (THQ), total hazard index (HI), and target cancer risk (TR). The average ranges of THQs (7.79 × 10−8−8.97 × 10−3), HIs (4.30 × 10−5−1.55 × 10−2), and TRs (2.70 × 10−9−1.34 × 10−5) were observed in the studied seafood species. The results revealed no non-carcinogenic and carcinogenic health risks from consuming these 14 kinds of seafood.

Dissolved metal assessment in surface seawater: A spatial-seasonal evaluation in the Zhejiang coastal waters, the East China Sea

The spatial-seasonal distributions and variations, correlations with environmental variables and the pollution degrees of dissolved metals in the Zhejiang coastal seawater were investigated. The concentrations of six dissolved metals (i.e. Cu, Pb, Zn, Cd, As and Hg) were in the ranges of 0.10-6.40 (1.6 ± 0.8), 0.16-3.60 (1.2 ± 0.7), 2.50-24.0 (8.5 ± 4.8), 0.011-0.180 (0.07 ± 0.03), 0.85-4.20 (2.1 ± 0.8) and 0.001-0.110 (0.06 ± 0.02) μg/L, throughout the four seasons, respectively. Significant differences in all the dissolved metals were found among seasons, whereas no significant differences were found among stations. The average concentrations of metals were in the following order: Zn > As>Cu > Pb > Cd > Hg. Single metal contamination factor was in the following order: Pb > Hg > Zn > Cu > As>Cd. The pollution level of dissolved metals in the Zhejiang coastal waters (ZCW) was low. Most of the dissolved metals were correlated to temperature, indicating seasonal differences. The redundancy analysis (RDA) indicated that depth, temperature, nitrate and phosphate could best explain the variance pattern of dissolved metals in the ZCW.

Comparison of Pollution Levels, Biomagnification Capacity, and Risk Assessments of Heavy Metals in Nearshore and Offshore Regions of the South China Sea

Seawater and fish were collected from nearshore (Pearl River Estuarine, PRE) and offshore (middle of the South China Sea, MSCS) regions of the South China Sea (SCS) to determine the heavy metals (HMs) pollution status and biomagnification characteristics. Results show that Cu in PRE seawater was moderately contaminated. Overall pollution risk of seawater were PRE (3.32) > MSCS (0.56), whereas that of fish was MSCS (0.88) > PRE (0.42). δ¹³C and δ¹⁵N exhibited distinguished characteristics for PRE and MSCS fish, indicating the diverse energy sources, nitrogen sources, and food web structures of nearshore and offshore regions. Cu was biomagnified whereas Pb and Ni were biodiluted in offshore fish. Hg presented significant biomagnification in both of nearshore and offshore fish. Finally, the target hazard quotient of Hg (1.41) in MSCS fish exceeded the standard limit, which was posed by high Hg concentration and consumption rate of offshore fish.

Spatiotemporal patterns and influencing factors of dissolved heavy metals off the Yangtze River Estuary, East China Sea

Dissolved heavy metal pollution in the ocean is becoming an environmental concern. Their distribution patterns are complex and influenced by multiple factors in the coastal ocean. Therefore, more investigations are needed to understand their behavior in the seawater. This study systematically investigated the distribution of Cu, Pb, Cd, As, Zn and seawater properties in the surface and bottom water off the Yangtze River Estuary, East China Sea in spring, summer and autumn, 2019. The results showed significant spatiotemporal distribution that three-zone-pattern of estuary, nearshore, and offshore can be divided. While sources, hydrodynamics, biological uptake and sediment resuspension affected the overall distribution, dissolved oxygen and pH dominantly influenced the estuary and offshore respectively, with more complex factors in the nearshore. Low ecological risks were assessed during the study, but global warming, ocean acidification and hypoxia are essential concerns to understand the biogeochemistry of dissolved heavy metals in the ocean.

The scale identification associated with priority zone management of the Yangtze River Estuary

Watershed and catchment area-based water quality management are important methods for comprehensive management of rivers and lakes. The impacts of land use/land cover (LULC) on river water quality vary with spatial scales, such as watersheds, catchments, and riparian zones. Achieving an effective spatial scale relationship between LULC and water quality, determining priority management areas, and reaching sustainable development of large estuarine deltas remain problematic. In this study, buffering analysis on the water quality data of the Yangtze River Estuary from 2009 to 2018 was conducted based on LULC, and the priority management areas of the basin were identified. Also, we infer that future river restoration or management efforts should focus on priority management area construction of a 1500 m riparian zone and a 150 km reach zone. Conclusively, establishing a priority management area within the effective buffer zone is key to watershed water quality management.

Bioaccumulation of mercury along continuous fauna trophic levels in the Yellow River Estuary and adjacent sea indicated by nitrogen stable isotopes

Mercury (Hg), and its organic forms, are some of the most hazardous elements, with strong toxicity, persistence, and biological accumulation in marine organisms. Hg accumulation in continuous trophic levels (TL) in marine food chains remains unclear. In this study, individual invertebrate and fish samples collected from the Yellow River Estuary adjacent sea were grouped into continuous TL ranges, and the bioaccumulations of total Hg (THg) and methylmercury (MeHg) were analyzed. The trophic magnification factor in invertebrates and fish was 1.40 and 1.72 for THg, and 2.56 and 2.17 for MeHg, indicating that both THg and MeHg were significantly biomagnified with increasing TL in both invertebrates and fish through trophic transfer. To evaluate the health risk of seafood consumption, the target hazard quotient (THQ) was calculated. Increasing THQ values indicated that the health risks of invertebrate and fish consumption in humans, especially children, were both elevated with increasing TL. THQ values > 1 indicated that consumption of invertebrates at a TL above 4.0 and fish above 4.5 may pose a relatively higher risk for children. Therefore, the consumption of both individual invertebrates and fish at high trophic positions may present greater health risk, especially in young children.

Distribution and risk assessment of heavy metals in the economic fish of the Southern Fujian Province

The distribution and risk assessment of heavy metals (Pb, Cu, Cr, Zn, Cd, As and Hg) in the economic fish of the Southern Fujian Province was acquired. The Cd content was below the detection limit. 53.5% of As and 26.7% of Hg were lightly polluted, but the indices of P_in (Nemero comprehensive pollution index) and MPI (metal pollution index) both indicated no pollution. The indices of EDI (estimated daily intake) and THQ (target hazard quotient) both indicated no non-carcinogenic risk of HMs. The index of R_i (average annual cancer risk) verified no carcinogenic risk for Pb and acceptable risk for As. Furthermore, molecular docking results revealed As may have significant reproductive toxicity to humans. Our findings serve to heighten an awareness of economic fish consumption and provide a reference for marine environmental management and food security in study area.

Water quality characteristics, sources, and assessment of surface water in an industrial mining city, southwest of China

This study analyzed the physiochemical factors, spatial-seasonal variations, and correlations of main pollutants, water quality evaluation and possible sources of nitrogen in the surface water of Anning, an industrial mining city, southwest of China. Seventy surface water samples were examined through an analysis of 41 physiochemical indices in the dry and wet seasons in April and July 2019, respectively, while a part of water site samples collected in July 2020 was taken for isotope detections. To identify the water quality, single-factor pollution index (SI), Nemerow pollution index (NPI), and water quality comprehensive pollution index (CPI) were calculated based on 13 pollutants using GB 3838-2002 class III water standard values. Results pointed to typical pollutants of TN, TP, and F with ranges of l.d.-44.8 (2.00 ± 3.69) mg/L, l.d.-250 (2.07 ± 15.35) mg/L, and l.d.-11 (1.48 ± 7.34) mg/L respectively with high spatial variability. The concentrations of heavy metals present in the water samples followed the sequence: Zn > Ni > Cu > As > Pb > Cd > Hg, and most of the samples showed low values relative to the standard permissible limits. In three methods, the water quality evaluation results of SI method were obviously worse than NPI and CPI methods. The NPI and CPI values had ranges of 0.116-887.40 (8.12 ± 74.89) and 0.03-111.54 (1.17 ± 9.40), respectively; consequently, the water quality was considered generally well, with more than 65% of sites classified as "cleanness" or "sub-cleanness." Most of the values of δ¹⁵N and δ¹⁸O had ranges of 6.62-20.05‰ and - 6.53-4.70‰, which suggested the livestock manure resources were the possible sources of nitrogen that entered the surface water causing more pollution in the wet season. Part of sites with serious water pollution had very high concentrations of P, F, or heavy metals and might be closely correlated with the point source pollution of phosphate chemical industry or iron ore mining and smelting. The results of this study can provide the basic data for efficient water management and human health protection for local government.

Pollution assessment and sources of dissolved heavy metals in coastal water of a highly urbanized coastal area: The role of groundwater discharge

Heavy metal concentrations and physicochemical parameters in coastal waters were measured to analyze the spatial distribution characteristics, pollution degrees, and sources of heavy metals in the heavily urbanized Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in China. Heavy metal concentrations in the eastern GBA were higher than those in the west, and the levels of Pb and Zn in seawater were higher than those in groundwater and river water. Both the pollution factors and comprehensive water quality index demonstrated that seawater was not contaminated with As, Cd, Cr, and Ni, whereas low to considerable levels of contamination of Pb and Zn were observed in the central and eastern sections of the GBA. Multiple statistical analyses suggested that the Pb and Zn contaminations in seawater were probably derived from atmospheric deposition and human activities, and the excess amounts of As, Cd, Cu, Ni, and Zn in groundwater were attributed to anthropogenic activities. The heavy metal fluxes from submarine groundwater discharge (SGD) were comparable to, or even greater than, those from local rivers. Therefore, SGD is a significant invisible contributor of heavy metals into the coastal ocean that has often been overlooked in comparison to other visible pollution sources. This study suggests that SGD should be considered in the assessment of heavy metal pollution and future water quality management protocols in marine ecosystems.

Impact of water-sediment regulation on the concentration and transport of dissolved heavy metals in the middle and lower reaches of the Yellow River

Anthropogenic activities in river basins, especially large-scale water conservancy projects, have notably impacted the physical, chemical and ecological environments of estuaries and coastal areas. In this paper, the effects of water and sediment regulation (WSR) on the concentration and transport of heavy metals in the Yellow River were studied based on a continuous daily heavy metal survey in both the middle reaches (Xiaolangdi station) and lower reaches (Lijin station) of the Yellow River during the WSR period in 2019. The results indicated that the variation in the water oxidation-reduction environment of the Xiaolangdi reservoir during the WSR process exerted an important impact on the concentrations of dissolved Cu, Cd, Pb, Cr and As at the Xiaolangdi station but exerted almost no influence on the concentration of dissolved Ni. At Lijin station, the dissolved heavy metal content first increased and then decreased in the first stage, which mainly depended on the release of heavy metals from resuspended sediments. In the second stage, the heavy metal content gradually decreased due to adsorption onto fine particles discharged from the reservoir. The dissolved heavy metal flux during the water-sediment regulation scheme (WSRS) period accounted for 16.9-33.4% of the annual total dissolved heavy metal flux. WSRS changed transport of water and sediment. The dissolved heavy metal concentrations at the Xiaolangdi station were mainly controlled by the discharge of water and sediments from the Xiaolangdi reservoir, while the dissolved heavy metal concentration at the Lijin station was largely affected by the sediments resuspended from downstream riverbeds and the water and sediment scheduling mode of the Xiaolangdi reservoir. Dissolved heavy metal transportation was highly influenced by the WSR process within a short time. Human intervention, especially WSRS operation, apparently alters the natural states of both the mainstream and estuarine environments of the Yellow River.

Seasonal and Spatial Variation in Dissolved Heavy Metals in Liaodong Bay, China

Spatial–seasonal variations in dissolved heavy metals in surface seawater were analyzed based on surveys at 87 sampling sites and water samples from six rivers across Liaodong Bay. The concentrations of copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) had ranges of 0.20–40.00 (5.45 ± 5.67), 0.51–33.64 (4.68 ± 3.93), 0.03–13.47 (2.22 ± 2.01), and 0.50–80.09 μg/L (14.22 ± 16.32), respectively, throughout the four seasons of 2020. The trace metal concentration showed a spatial gradient of high to low from river to estuary and from inshore to offshore areas. A combination of pollution levels and marine sensitivity was employed to assess the pollution degree of the heavy metals. As a whole, the single pollution factors of trace metals in Liaodong Bay were ranged in the order Pb > Zn > Cu > Cd. The total pollution degree was relatively high in autumn and summer due to increased riverine inputs after the rainy season, while relatively low in spring and winter. These findings provide baseline data for future targeting policies to protect marine environments in Liaodong Bay.

Distribution, source and risk assessment of heavy metals in the seawater, sediments, and organisms of the Daya Bay, China

Cu, Pb, Zn, Cd, Cr, Hg and As in seawater, sediment and organisms of the Daya Bay, Guangdong province, China were measured to acquire the comprehensive understanding on distribution, sources and risk assessment of heavy metals (HMs) in the marine ecosystem. The concentrations were relatively ideal, and the Pb was the major pollutant in the seawater and sediment. The contents of HMs were highest in spring; the concentrations near the sewage outlet and shore were noticeable. Submarine pipeline sewage, atmospheric deposition and runoff were the main sources of HMs in coastal waters. Studied HMs were preferentially retained by liquid phase; Cd, Cu and Zn were the most accumulated elements in the organisms from the surrounding environment. Cd in shellfish deserved particular attention, but the health risks including non-carcinogenic and carcinogenic risks of all elements were within acceptable limits. The potential health risks of Pb have been confirmed by molecular docking.

Characteristics of Heavy Metals in Seawater and Sediments from Daya Bay (South China): Environmental Fates, Source Apportionment and Ecological Risks

In this study, the spatiotemporal distributions, potential sources, and ecological risks of Hg, Cr, and As in seawater, and Hg, As, Zn, Cd, Pb, and Cu in sediments from Daya Bay were investigated. The five-year average concentrations of Hg, Cr, and As in seawater were 0.020 μg/L, 0.79 μg/L, and 2.08 μg/L, respectively. The five-year average concentrations of Hg, As, Zn, Cd, Pb, and Cu in surface sediments were 0.04 mg/kg, 7.34 mg/kg, 63.81 mg/kg, 0.23 mg/kg, 25.60 mg/kg, and 11.78 mg/kg, respectively. Annual variations in Hg, Cr, and As in seawater exhibited different trends. HMs in sediments, such as As, Zn, Pb, and Cu, exhibited similar annual variations, whereas Hg and Cd exhibited different annual variations. The spatial distribution of metal species in seawater and sediments showed significant variability, and the concentrations decreased gradually from the coast to the open sea. The comprehensive potential ecological hazard index (RI) of HMs in sediments indicated a relatively high risk, especially for Hg and Cd contamination. The geoaccumulation indices (Igeo) of As, Zn, Pb, and Cu suggested that these metals did not pollute Daya Bay, whereas those of Cd and Hg indicated mild and moderate pollution. The environmental fates of HMs were discussed based on Pearson correlation analysis, revealing that concentrations of HMs were greatly affected by parameters, such as pH, salinity, dissolved oxygen (DO), and total organic carbon (TOC). Principal component and factor analyses indicated that Hg, Cr, As, and dissolved inorganic nitrogen (DIN) in water originated from similar sources, including domestic sewage and wastewater from fishing ports, runoffs, and outlets. For sediments, it was proposed that Cu, Zn, As, Pb, and TOC exhibited similar sources, including cage culture and waste discharge from outlets. Meanwhile, Hg and Cd originated from other point sources, such as a harbor. The study suggests that sustainable management and economic development be integrated to control pollutant emissions in Daya Bay.

Cadmium (Cd), Copper (Cu), and Zinc (Zn) levels in commercial and non-commercial fishes in the Blanakan River Estuary, Indonesia: A preliminary study

The Blanakan River Estuary, located on the northern coast of West Java, receives heavy metals from anthropogenic activities nearby. This study investigates Cu, Cd, and Zn metals in water and their accumulation in fish (commercial and non-commercial). The samples (water and fish) were collected from seven sampling stations. The metals concentration in the surface water of the Blanakan River Estuary has exceeded the limit allowed by the Indonesian government. The average metal concentration sequence in commercial and non-commercial fish was Zn > Cu > Cd. In general, it was found that the concentration of Zn and Cd (Cu) metals in fish had (had not) exceeded the limits allowed by the FAO/WHO. Based on Bioconcentration Factor (BCF) value, all of fishes species have a low ability to accumulate heavy metals (BCF <1000). Based on Estimated Daily Intake (EDI), all fish species have a low risk for health, both for adult and children.

Distribution, sources, and ecological risks of potentially toxic elements in the Laizhou Bay, Bohai Sea: Under the long-term impact of the Yellow River input

Potentially toxic element (PTE) contamination is a common environmental issue in offshore regions worldwide. Water and sediment samples were collected from the Yellow River downstream and adjacent Laizhou Bay to investigate the residues, sources, and ecological risks of 11 typical PTEs (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sc, V, and Zn). The results indicated that the concentrations of PTEs in the sediments decreased from the Yellow River Estuary to the inner Laizhou Bay under the long-term effect of the Yellow River input. Principal component analysis (PCA) identified three potential sources: natural origins, coastal anthropogenic activities (e.g., oil exploration and steel refining), and marine production (e.g., marine aquaculture and transportation). Among the PTEs, Cd was the most significant contaminant, with a contamination factor (CF) of 2.06 ± 0.78. Furthermore, Cd was the most sensitive factor used in evaluating the overall ecological risk using Monte Carlo analysis, with a contribution of up to 96%. Although the overall contamination and risk levels were low in the bay, a higher pollution load index (PLI) and risk index (RI) adjacent to the Yellow River Estuary indicated that the Yellow River remained the primary contributor to the PTEs contamination in the bay.

Spatial and environmental characteristics of colloidal trace Cu in the surface water of the Yellow River Estuary, China

Dynamic variations in chemical composition and size distribution of dissolved copper (Cu) along the river-sea interface in the Yellow River Estuary (China) were investigated. On average, ~64% and ~8% of bulk dissolved Cu (<0.45 μm) were partitioned in the <1 kDa fraction and 1-100 kDa, respectively. The other 28% were in the 100 kDa-0.45 μm colloids, which indicates that this fraction may dominate the overall morphology of colloidal Cu. The <3 kDa Cu fraction was susceptible to environmental parameters and the >3 kDa fraction was related to the behavior of dissolved organic carbon. 1-100 kDa Cu migrated more violently than >100 kDa Cu and tended to be a stable polymer, with stability increasing towards the sea. The source of <1 kDa Cu was complex and may be supplemented by the decomposition of small molecular colloids and the addition of the sediments or particles ligands.

Assessment of cadmium pollution and subsequent ecological and health risks in Jiaozhou Bay of the Yellow Sea

Million tons of cadmium (Cd) are annually discharged into China's coastal regions, creating a persistent hazard to marine organisms and human health. This study assessed Cd residues in the Yellow Sea's semi-enclosed Jiaozhou Bay (JZB), finding concentrations of 0.05-0.94 μg/L in seawater and 0.03-0.18 mg/kg in sediment. For marine organisms, mollusks had the highest Cd concentration (0.44 ± 0.09 mg/kg), followed by crustaceans (0.26 ± 0.08 mg/kg) and fish (0.10 ± 0.02 mg/kg). Cd was clearly accumulated by mollusks, with biota-sediment accumulation factor (BSAF) values >1 and biota-water accumulation factor (BWAF) values >1000. Stable nitrogen isotope (δ¹⁵N) analysis showed that Cd underwent biomagnification in mollusks, but was significantly bio-diluted with increasing trophic level among other marine organisms. In general, Cd contamination levels were low in the JZB's seawater and sediment, and fish was estimated to be certainly polluted due to strict safety limitations on seafood in China. Current Cd residues mean that few aquatic species (<< 5%) would be affected by acute exposure, and ~ 10% of the species would be affected by chronic exposure. Based on target hazard quotients (THQ) and estimated weekly intakes (EWIs), urban residents around the JZB would experience higher health risks in comparison with rural residents due to higher seafood consumption rates, especially from mollusk consumption. Therefore, urban households in the area should increase their fish consumption rate and reduce that of mollusks.

Long-term study of heavy metal pollution in the northern Hangzhou Bay of China: temporal and spatial distribution, contamination evaluation, and potential ecological risk

Coastal ecosystem is vulnerable to heavy metal contamination. The northern Hangzhou Bay is under intensifying impact of anthropogenic activities. To reveal the heavy metal pollution status in the coastal environment of the Hangzhou Bay, a long-term investigation into the heavy metal contamination during 2011 to 2016 was initiated. Seawater and sediment samples of 25 locations depending on the sewage outlet locations in the northern Hangzhou Bay were collected to analyze the concentrations and temporal and spatial distribution of Cu, Pb, Zn, Cd, Hg, and As. Pollution condition, ecological risk, and potential sources were additionally analyzed. Results show that the annual mean concentrations of Cu, Pb, Zn, Cd, Hg, and As were 2.13-4.59, 0.212-1.480, 7.81-20.34, 0.054-0.279, 0.026-0.090, and 1.08-2.57 μg/L in the seawater, and were 16.34-28.35, 16.25-26.33, 67.32-97.61, 0.084-0.185, 0.029-0.061, and 6.09-14.08 μg/L in the sediments. A decreasing trend in Cu, Pb, Zn, Cd, and Hg concentrations and an increasing trend in As of the seawater were observed. However, in the sediment, the heavy metals demonstrated a rising trend, except for Hg. The single-factor pollution index showed an increasing trend in Cd and As in the seawater, depicting an enhanced pollution of Cd and As, while in the sediments, Cu, Pb, and As were in pollution-free level (average Geo-accumulation index (I_geo) values below 0) in general, and only occasional slight pollution occurred in individual years, e.g., As with 0.403 in 2016. The mean I_geo values of Cd ranged from - 0.865 to 0.274 during 2011 to 2016, indicating that the pollution level of Cd was slight, but is likely to increase in the forthcoming years. The level of heavy metal contamination in sediments was low in 2011 (5.853) and 2012 (5.172), and moderate during 2013 to 2016 (in the range of 6.107 to 7.598), while the degree of potential ecological risk was low in the study period, except moderate in 2013 (125.107). The highest contamination degree and potential ecological risk appeared in 2013 (Cd = 7.598; RI = 125.107), while Cd and Hg contributed over 75% of the ecological risk. Overall, the results show low pollution level and low potential ecological risk in the northern Hangzhou Bay; however, more attention should be paid to the potential ecological risk due to Hg and Cd. Graphical abstract Spatial distribution of the heavy metal levels in the sediment of the coastal environment of the northern Hangzhou Bay on a long-term basis.

Occurrence, partition, and risk of seven heavy metals in sediments, seawater, and organisms from the eastern sea area of Shandong Peninsula, Yellow Sea, China

To obtain a systematic knowledge on occurrence, partition, and risk of seven heavy metals (Cu, Pb, Zn, Cd, Cr, Hg, and As) in multi-media of marine ecosystem, sediments, seawater, and 20 species of organisms were collected from 62 sites in the eastern sea area of Shandong Peninsula, located in Yellow Sea (China), in four seasons of 2016. The concentrations were in the low-middle level compared with values from other sea areas all over the world. The highest concentrations of most of the seven elements were detected in sediments and seawater near the coastline. LogKd (distribution coefficient of sediment/water) ranged from 3.3 to 4.7. Concentrations of heavy metals in mollusc and/or crustacea were generally higher than that in fish (especially pelagic species), and while there was no significant relationships between pollutant concentrations and trophic levels. Cd and As were the most bio-accumulative elements, and As in mollusc may pose low non-carcinogenic risk We suggest that in the studied area heavy metals are mainly sourced from terrestrial input, preferentially retained by sediments, then accumulated in mollusc, and finally entered human body through mollusc consumption. Our study sounds an alarm for stricter control of metal emissions into this sea area.

Sources and ecological risk assessment of the seawater potentially toxic elements in Yangtze River Estuary during 2009-2018

The purpose of this paper is to understand the sources of potentially toxic elements (PTE) and provide some suggestions to control PTE pollution. For this purpose, data from 30 monitoring stations for 2009-2018 were used to assess the PTE concentrations of Hg, Cu, Pb, Cd, Zn, and As in the Yangtze River Estuary. The PTE concentrations varied significantly (P < 0.05) by one-way ANOVA in the ranges of 0.002-0.224 (Hg, 0.043 ± 0.032), 0-9.700 (Cu, 1.600 ± 1.000), 0-3.900 (Pb, 1.000 ± 0.700), 0.002-0.370 (Cd, 0.050 ± 1.000), 0.100-85.000 (Zn, 14.000 ± 13.000), and 0.998-3.290 μg/L (As, 1.857 ± 0.455). Generally, the PTE concentrations decreased from year to year and were consistently satisfied the "grade-one seawater" quality standard after 2014. The concentrations of Cu, Cd, Zn, and As decreased as far from inshore, while increased closer to land in the estuary. Concentrations of Pb and Hg showed differences because of local industrial and aquacultural activities. This study identified three clusters and two PTE sources and provided some constructive suggestions for pollution control in PTE.

Correlation patterns between magnetic parameters and heavy metals of core sediments in the Yellow River Estuary and their environmental implications

The potential use of environmental magnetism to investigate heavy metal pollution was investigated by analyzing sediment samples from a short sediment core (Z07) from the Yellow River Estuary. The heavy metal concentrations and speciation, grain sizes, and magnetic properties were determined, and correlations between the parameters were identified. Strong exponential relationships were found between the Hg concentrations and χ_fd%, χ_ARM-20mT, and clay content. Linear correlations were found between the As, Cd, Co, Cr, Ni, Pb, and Zn concentrations and χ_fd%, χ_ARM-20mT, and clay content. This indicated that Hg was mainly sorbed to the surfaces of nano-sized magnetic and clay minerals and predominantly had anthropological sources but the other heavy metals had mineralogical and other natural sources. These conclusions were supported by the heavy metal fractionation results. Heavy metal concentrations in sediment at site Z07 have decreased markedly since 2003 in response to water and sediment regulations being implemented.

Hydrochemical composition and potentially toxic elements in the Kyrgyzstan portion of the transboundary Chu-Talas river basin, Central Asia

Water chemistry and the assessment of health risks of potentially toxic elements have important research significance for water resource utilization and human health. However, not enough attention has been paid to the study of surface water environments in many parts of Central Asia. Sixty water samples were collected from the transboundary river basin of Chu-Talas during periods of high and low river flow, and the hydrochemical composition, including major ions and potentially toxic elements (Zn, Pb, Cu, Cr, and As), was used to determine the status of irrigation suitability and risks to human health. The results suggest that major ions in river water throughout the entire basin are mainly affected by water-rock interactions, resulting in the dissolution and weathering of carbonate and silicate rocks. The concentrations of major ions change to some extent with different hydrological periods; however, the hydrochemical type of calcium carbonate remains unchanged. Based on the water-quality assessment, river water in the basin is classified as excellent/good for irrigation. The relationship between potentially toxic elements (Zn, Pb, Cu, Cr, and As) and major ions is basically the same between periods of high and low river flow. There are significant differences between the sources of potentially toxic elements (Zn, Pb, Cu, and As) and major ions; however, Cr may share the same rock source as major ions. The risk assessment revealed low non-carcinogenic and carcinogenic risks for human health; however, the maximum carcinogenic risk for As exceeded the allowable value, which requires further consideration. These results provide a scientific basis for the management of agricultural irrigation uses and also infill existing gaps regarding the hydrochemical composition in the Chu-Talas river basin, Central Asia.

Spatial-temporal variations and trends predication of trace metals in oysters from the Pearl River Estuary of China during 2011-2018

Estuaries are often considered to be the filters of pollutants from the land-derived outflows of freshwater to open seawater. Oysters are efficient bioaccumulators of metals in the estuarine environment, however, little information is available on the long-term tissue variability of metals in a large dynamic estuary under complex urbanized and anthropogenic impacts. Thus, an eight-year biomonitoring study of metals (Ag, Cd, Cr, Cu, Ni, Pb, and Zn) in the oysters from 10 sites were carried out to reveal the highly spatial-temporal variations in the Pearl River Estuary (PRE) of China during 2011-2018. Cd, Cu, and Zn in oysters were significantly correlated with the dissolved metals in seawater. Geographically, Ag, Cd, and Cr were higher in the western sites, and Cu, Ni, and Zn were higher in the eastern sites. High seasonal variations of Ag, Cu, and Zn were found in the wet season. The calculated annual change rates (v_c) of Cd, Cu, Zn, Ag, Pb, Ni, and Cr in the oysters were -1.1, -45, -48, 0.338, -0.216, -2.2, and -2.8 μg/g/y, respectively. If such decreasing rates of v_c (or natural logarithm rates v) were maintained, Cd, Cu, Zn, Pb, and Ni in oysters from PRE would be expected to recover to the national 50% concentrations in years 2022 (2024), 2045 (2079), 2073 (2110), 2021 (2023), and 2019 (2020), respectively. Long-term series observations of metals in organisms reflected the real bioavailability of metals, pollution status, and trends for environmental management and control in a large dynamic and contaminated estuary.

Modulation of copper-induced antioxidant defense, Cu transport, and mitophagy by hypoxia in the large yellow croaker (Larimichthys crocea)

This study aimed to investigate the effects of hypoxia on Cu-induced antioxidant defense, Cu transport, and mitophagy in the liver of the large yellow croaker. Fish were exposed to hypoxia (3.0 mg L^-1), Cu (120 μg L^-1), and hypoxia (3.0 mg L^-1) plus Cu (120 μg L^-1) for 48 h. Hypoxia exposure increased antioxidant abilities to maintain cellular redox balance. Although Cu exposure alone improved antioxidant defense, Cu transport, and mitophagy, these stress responses could not completely neutralize Cu toxicity, as reflected by the elevated reactive oxygen species (ROS) and lipid peroxidation (LPO) and hepatic vacuoles. When compared with Cu stress alone, hypoxia increased Cu toxicity by inhibiting antioxidant defense, Cu transport, and mitophagy, leading to the increment of mortality, ROS, and LPO, and the deterioration of histological structure. The adverse effects of hypoxia on Cu-induced metal transport and mitophagy might be involved in metal-responsive element-binding transcription factor-1 (MTF-1) and Forkhead box O-3 (FoxO3) signaling pathways, respectively. Overall, hypoxia reduced antioxidant response, Cu transport, and mitophagy in fish exposed to Cu, which contributes to understanding the molecular mechanisms underlying negative effects of hypoxia on Cu toxicity in fish.

Spatial-seasonal variations and ecological risk of heavy metals in Persian gulf coastal region: case study of Iran

PURPOSE

This study aimed to perform a systematic review to analyse the seasonal concentration and ecological risk assessment of heavy metals (HMs) in seawater and sediment samples collected from the coastline of Jam city in Bushehr, Iran.

METHODS

A total of 96 sediment and seawater samples were collected from 16 sampling stations during the spring, summer, autumn, and winter of 2017. Then, the concentrations of Pb, Ni, Cd, Cr, Cu, Zn, and Fe were determined. Finally, the pollution load index (PLI), ecological risk (Er), and environmental risk (RI) were calculated to assess the HM ecological risk.

RESULTS

The results showed that the mean concentrations of HMs were lower than the maximum acceptable concentration by SQG and NOAA. In addition, the PLI assessed a low pollution load level in the region. The ER and RI results also showed that the region was at low risk, and the metal risk was classified as Cd > Cu > Pb > Ni > Zn > Cr. In some samples, the mean concentrations of HM were found to be higher with a statistically significant difference (P˂0.05). The results also showed that sediments were engaging in a moderate Er by Cd.

CONCLUSIONS

Generally, the rapid growth of urbanization, as well as industrial and human activities, along this coastline and area has increased the pollutants dumped into the seawater and sediments. Thus, it is necessary to take regular monitoring programs and develop better management strategies to minimize the amount of HMs entering into this coastal area.

Heavy Metals and Related Human Health Risk Assessment for River Waters in the Issyk-Kul Basin, Kyrgyzstan, Central Asia

The water resources of Central Asia play an important role in maintaining the fragile balance of ecosystems and the sustainable development of human society. However, the lack of research on the heavy metals in river waters has a far−reaching influence on public health and the sustainable development in Central Asia. In order to reveal the possible sources of the heavy metals and to assess the associated human health risks, thirty−eight water samples were collected from the rivers of the Issyk−Kul Basin during the period with low river flow (May) and the period with high river flow (July and August), and the hydrochemical compositions and major ions of heavy metals were analyzed. No changes in hydrochemical facies were observed between the two periods and the river water type was calcium bicarbonate. Carbonate dissolution and silicate weathering controlled the variation of cations and anions in river waters from the Issyk−Kul Basin. There were some differences in the sources of heavy metals in water bodies between the two periods. During the period with low river flow, heavy metals (Cr) were closely clustered with major ions, indicating that they were mainly affected by water–rock interactions. During the period with high river flow, all heavy metals studied in this paper had different sources of major ions, and the heavy metals maybe influenced by human activities. From the human health risk assessment, the hazard quotients for all samples were less than 1, reflecting that there was no noncarcinogenic risk in the river waters of the Issyk−Kul Basin during the two sampling periods. However, the water samples with carcinogenic risk of arsenic exceeding the threshold (10⁻⁴) accounted for 21.1% of the total, indicating that there were some certain carcinogenic hazards for human health via water drinking with direct oral ingestion. The results are of certain significance for the utilization and protection of water resources in the basin as well as the protection of public health.

Ecological risk assessment of heavy metal pollution in the water of China's coastal shellfish culture areas

In order to learn about the status of heavy metals and ecological risks in the water of thirteen China's costal shellfish culture areas, principal component analysis was applied to analyze the distributions of five kinds of heavy metal, while the safety threshold method was employed to evaluate the ecological risks. The results showed that among the 13 shellfish culture areas, the average metal concentrations were in the order of Zn > Cu > Pb > Hg > Cd, and all heavy metals were below the second standards for sea water quality of China. The distribution of heavy metals in 13 shellfish culture areas was reflected by two principal components with the contribution rates of F1(Cu) and F2(Zn, Pb) were 36.14% and 23.40%,respectively,which was less affected by economic and geographical differences. The ecological risks assessment of five kinds of heavy metals showed that MOS10 was more than one; the probabilities of five heavy metals affecting more than 10% of aquatic organisms were 49.52%, 24.11%, 17.49%, 22.05%, and 5.66%, respectively, the ecological risk of five main heavy metals was in order Cu > Zn > Cd > Pb > Hg. In the selected thirteen shellfish culture areas, the value of msPAF of seven culture areas was higher than 20%, indicating these areas are highly ecologically contaminated by heavy metals, and the other four shellfish culture areas with value of 0, indicating that these areas have no ecological risk of heavy metals pollution.

Zinc chloride influences embryonic development, growth, and Gh/Igf-1 gene expression during the early life stage in zebrafish (Danio rerio)

Although zinc is an essential element for organisms, excess zinc exposure is harmful. We assessed the possible negative influence of zinc (Zn) on the freshwater fish Danio rerio during its early life stage by using Organization for Economic Cooperation and Development test guideline no. 210. Lethality of Zn after hatching occurred in a concentration dependent manner. The LC₅₀ and lowest observed effect concentration of mortality values in the present toxicity assay were 2.31 mg/L (95% confidence limit: 1.81-3.05) and 1.5 mg/L, respectively. These values were close to the reported concentration recorded in aquatic environments. Growth inhibition was observed at 15 and 30 days post-hatching with Zn exposure of 1.5 mg/L. In general, the growth hormone (Gh)/insulin-like growth factor-I (Igf-1) axis is important for growth in fishes, and Zn exposure induced a significant reduction of igf-1 expression at the concentration that caused growth inhibition. These findings suggest that the observed growth inhibition was induced by the suppression of igf-1 expression. In addition, these results suggest that by examining gene expression on the Gh/Igf-1 axis, it may be possible to predict growth suppression by chemical exposure.

Effect of nano zinc oxide on the acute and reproductive toxicity of cadmium and lead to the marine copepod Tigriopus japonicus

Given the absorbability of nZnO and its inevitable coexistence with trace metals such as Cd and Pb in coastal environment, nZnO can adsorb these pollutants thereby affecting their distribution in different media of marine ecosystem. The marine copepod Tigriopus japonicus was applied in the present study to investigate the combined effect of nZnO and Cd or Pb on mortality and reproduction in marine organisms. For acute exposure, presence of 1.0 mg/L nZnO increased the toxicity of both Cd and Pb, as their LC₅₀ decreased from 5.9 and 75.4 mg/L to 3.95 and 48.0 mg/L, respectively. For 21 d chronic exposure, the reproduction of the copepod was influenced by Cd and Pb at environmental relevant concentrations, and the interaction between nZnO and Cd or Pb appeared to be antagonistic. The waterborne Cd and Pb concentration was affected by nZnO for neither acute nor chronic exposure, indicating no adsorption of these two metals to nZnO at relative low concentration. The overall findings of this study suggested the binary exposure to nZnO/Cd or nZnO/Pb might have potential different toxic mechanisms between acute and chronic exposure.