The source of natural and anthropogenic heavy metals in the sediments of the Minjiang River Estuary (SE China): implications for historical pollution

The challenge of establishing natural geochemical backgrounds in human-impacted mangrove soils of Northeastern Brazil

Mangroves are delicate ecosystems constantly pressured by urbanization, pollution, and climate change. Establishing natural geochemical backgrounds (GB) or geochemical baseline levels (GBL) for metals in these soils is challenging due to the dynamic coastal conditions and the combined influence of anthropogenic and natural geological factors. This study aims to establish the natural geochemical background of trace elements in mangrove soils, a more complex task than establishing GBL. A total of 360 soil samples were collected from the mangrove environments of Todos os Santos Bay, Northeast Brazil, specifically from the estuaries of the Jaguaripe, Paraguaçu, and Subaé rivers. The samples were analyzed using handheld X-ray fluorescence spectrometry (XRF), and the data were processed using the Tukey-Inner Fence (TIF) and Cumulative Distribution Function (CDF) methods, with results compared to the multiple regression method based on geochemical data. The Subaé estuary has the highest trace element concentrations, primarily due to its unique geological context, independent of diffuse metal contamination sources. CDF effectively proposed GBL values, providing a comprehensive view of trace element distribution. However, multiple regression outperformed both TIF and CDF methods in managing environmental complexity and modelled precise estimated individual background values, independently of anthropic contamination or variation of soil texture. The predicted background values were 19% and 43% lower than CDF and TIF values, respectively. Some samples showed particularly low modelled background values, up to 75, 25 or 11 times lower than CDF values for V, Mo, Pb respectively. This study enhances the understanding of geochemical dynamics in mangrove estuaries, demonstrating the potential to estimate reliable natural soil backgrounds using advanced statistical methods, even in contaminated and highly changing coastal environments. The findings provide valuable guidelines for assessing and preserving environmental quality in mangrove soils under anthropic pressures.

Geochemistry and risk assessment of potentially toxic elements in surface river sediments (Chirchik-Akhangaran basin, Uzbekistan)

The geochemistry of river sediments depends on several factors, namely the nature of exposed lithologies, weathering, different grain-size and sorting due to hydraulic phenomena, and anthropogenic inputs. Potentially toxic elements (PTEs) in river sediments may result in potential health risks due to overexposure when riverfronts are used for recreational activities. In the present study, sediments were collected from 17 sites in the Chirchik-Akhangaran River basin in the Tashkent Province (Uzbekistan, Central Asia) during baseflow conditions. The concentration of PTEs was determined in the < 2 mm (bulk) and < 63 µm (fine) grain-size fractions. The assessment of contamination using environmental indices highlighted low to moderate contamination for Li, Be, Co, Ni, Sb, V, and Cr in Chirchik and Akhangaran sediments and from moderate to high contamination for Cu, Zn, Mo, Cd, Tl, Pb, and As in some of the Akhangaran sites. The potential ecological risk indices suggest that risk ranges from low to moderate in most stations from the Chirchik and Akhangaran River catchments; high risk is restricted to few Akhangaran sites. Risk assessment carried out for the Chirchik River, where waterfront recreational use is popular, indicates that the non-carcinogenic risk is acceptable for all contaminants and all pathways for an outdoor recreational setting. The cumulative Hazard Index (HI) resulted to be lower than the acceptance threshold (HI < 1) for both children and adults (0.795 and 9.27 × 10-2, respectively). In the case of carcinogenic effects, the risk is unacceptable for As through the ingestion pathway. The calculated screening level for As is 2.86 mg/kg.

Elevated lead mobility in sediments of a eutrophic drinking water reservoir during spring and summer seasons: Insights from isotopic signatures

Lead (Pb) pollution in sediments remains a major concern for ecosystem quality due to the robust interaction at the sediment/water interface, particularly in shallow lakes. However, understanding the mechanism behind seasonal fluctuations in Pb mobility in these sediments is lacking. Here, the seasonal variability of Pb concentration and isotopic ratio were investigated in the uppermost sediments of a shallow eutrophic drinking lake located in southeast China. Results reveal a sharp increase in labile Pb concentration during autumn-winter period, reaching ∼ 3-fold higher levels than during the spring-summer seasons. Despite these fluctuations, there was a notable overlap in the Pb isotopic signatures within the labile fraction across four seasons, suggesting that anthropogenic sources are not responsible for the elevated labile Pb concentration in autumn-winter seasons. Instead, the abnormally elevated labile Pb concentration during autumn-winter was probably related to reduction dissolution of Fe/Mn oxides, while declined labile Pb concentration during spring-summer may be attributed to adsorption/precipitation of Fe/Mn oxides. These large seasonal changes imply the importance of considering seasonal effects when conducting sediment sampling. We further propose a solution that using Pb isotopic signatures within the labile fraction instead of the bulk sediment can better reflect the information of anthropogenic Pb sources.

Total mercury, methylmercury, and their possible controlling factors in soils of typical coastal wetlands in China

Coastal wetland soils play a critical role in the global mercury (Hg) cycle, serving as both an important repository for total mercury (THg) and a hotspot for methylmercury (MeHg) production. This study investigated Hg pollution in soils dominated by Phragmites australis (PA) and Spartina alterniflora (SA) across five representative China's coastal wetlands (Yellow River (YR), Linhong River (LHR), Yangtze River (CJR), Min River (MR), and Nanliu River (NLR)). The THg concentrations ranged from 16.7 to 446.0 (96.3 ± 59.3 ng g-1, dw), while MeHg concentrations varied from 0.01 to 0.81 (0.12 ± 0.12 ng g-1, dw). We further evaluated Hg risk in these wetlands using potential ecological risk index (Er) and geographical enrichment factor (Igeo). Most wetlands exhibited low to moderate ecological risk, except the PA habitat in the YR wetland, showing moderate to high risk. Soil organic matter significantly influenced THg and MeHg distribution, while MeHg% correlated well with soil salinity and pH. These findings highlight the importance of organic-rich coastal wetland soils in THg and MeHg accumulation, with the soil properties influencing net MeHg production. Furthermore, SA habitat generally exhibited higher MeHg%, suggesting its invasion elevates the ecological risk of MeHg in coastal wetlands. ENVIRONMENTAL IMPLICATION: Mercury (Hg), a global pollutant, poses great risks to wildlife and humans. Since industrialization, anthropogenic Hg release surpassed natural sources. Long-term exposure leads to biomagnification of Hg. This study assessed Hg and methylmercury pollution and risks in soils of five China's coastal wetlands dominated by Phragmites australis and Spartina alterniflora. Environmental factors (total carbon, total organic carbon, total nitrogen, salinity, pH) were analyzed to reveal key variables influencing Hg pollution and methylation. Essential for quantifying Hg pollution in coastal wetlands, the findings provide a scientific basis for effective wetland conservation policies and addressing environmental health in these regions.

Ecological risk assessment of heavy metal(loid)s in riverine sediments along the East China Sea: A large-scale integrated analysis

This study comprehensively assesses spatial distribution, pollution levels, and potential sources of heavy metal(loid)s in surface sediments across multiple river systems along the coastal area of the East China Sea. Copper in Qiantang River and Xiangshan Bay showed higher concentations and exceeded the threshold effect value, while the higher content of Lead was mainly found in the Saijiang River, Oujiang River, and Minjiang River. Heavy metal(loid)s in the alluvium of Qiantang River, Jiaojiang River, and Yangtze River showed low to moderate pollution levels, with Cd posing the highest ecological risk, followed by Hg. Meanwhile, Qiantang River, Jiaojiang River, Yangtze River, and Oujiang River exhibited considerable to moderate ecological risks and low toxic risk. PMF model analysis results reveal that concentrations of Cr, Ni, and As were closely related with natural geogenic input (36.56 %), while industrial and traffic activities (48.77 %) were primary source of Cu, Pb, Zn, and Hg, and main source of Cd was agricultural emissions (14.67 %).

Exploring the primary magnetic parameters affecting chemical fractions of heavy metal(loid)s in lake sediment through an interpretable workflow

The magnetic properties of lake sediments account for close relationships with heavy metal(loid)s (HMs), but little is known about their relationships with chemical fractions (CFs) of HMs. Establishing an effective workflow to predict HMs risk among various machine learning (ML) methods in conjunction with magnetic measurement remains challenging. This study evaluated the simulation efficiency of nine ML methods in predicting the risk assessment code (RAC) and ratio of the secondary and primary phases (RSP) of HMs with magnetic parameters in sediment cores of a shallow lake. The sediment cores were collected and sliced, and the total amount and CFs of HMs, as well as magnetic parameters, were determined. Support vector machine (SVM) outperformed other models, as evidenced by coefficient of determination (R2) > 0.8. Interpretable machine learning (IML) methods were employed to identify key indicators of RAC and RSP among the magnetic parameters. Values of χARM, HIRM, χARM/χ, and χARM/SIRM of sediments ranging in 220-500 × 10-8 m3/kg, 30-40 × 10-5Am2/kg, 15-25, and 0.5-1, respectively, indicated the potential ecological risks of Cd, Hg, and Sb. This study offers new perspectives on the risk assessment of HMs in lake sediments by combining magnetic measurement with IML workflow.

Environmental hazard assessment and metal contamination in coastal sediments

In order to reduce contamination levels from diverse sources, it is important to understand the factors affecting the natural ecosystems that are impacted by coastal and marine pollution. In this study, we used GIS and remote sensing techniques to investigate and evaluate the distribution of heavy metals (Fe, Mn, Zn, Cr, Pb, Co, and Cu) in surface sediments along Tamil Nadu's East Coast (from Besant Nagar to Sathurangapattinam). The CF and Igeo of metals indicate that sediments contain no evidence of Fe, Mn, or Zn metal pollution in the sediments, with only mild contamination from Co, Cu, and Pb. In contrast, the sediment samples were found to be significantly contaminated with Cr. Heavy metal contamination occurs in the following order, according to our research: Cr > Pb > Cu > Co > Mn > Zn > Fe. Except for sites 8, 10, 11, and 13, where PLI>1 implies that there is no pollution in this area, the PLI values show that most of the locations are contaminated. The ecological risk index (ERI) values for five metals in the study areas are as follows: Cr > Pb > Cu > Mn > Zn. The sediment samples fall into the low-risk and highly polluted to dangerous sediment categories for SPI, according to the Risk index (RI). Based on the Mean Effect Range-Median Quotient (M-ERM-Q), Cu, Pb, Zn, and Cr metals in the research region have a 9-21% probability of being harmful. Statistical approaches show that the majority of heavy metals in sediments are of natural origin. The spatial distribution of heavy metals in surface sediments provides the conceptual framework for practical strategies to protect coastal areas. Many shreds of evidence indicate that anthropogenic inputs from the surrounding land area are primarily responsible for the deposition of these heavy metals in the coastal zone.

Temporal and spatial changes of water quality in intensively developed urban rivers and water environment improvement: a case study of the Longgang River in Shenzhen, China

The water quality status, spatial and temporal change processes, and water environment improvement process of urban rivers are valuable lessons to be learned under the sustainable development strategy. This study aims to reveal the water environment improvement process of intensively developed urban rivers, elucidate the spatial and temporal distribution characteristics of major pollutants, and provide recommendations for their water environment management. Water quality data from eight monitoring sites (2007-2020) in the Longgang River basin in Shenzhen, China, and comprehensive pollution index method (CPI), modified comprehensive pollution index method (M-CPI), and Pearson correlation analysis method were used for comprehensive analysis. The study shows that TN, TP, NH3-N, and COD have the greatest influence on the water quality of Longgang River, with the average pollution contribution of 53.39%, 14.49%, 11.66%, and 4.92%, in order. In 2015-2020, the water quality of the main stream of the Longgang River in the wet season was worse than that in the dry season, while the water quality of the tributaries Dingshan River and the Huangsha River in the dry season was worse than the wet season. The spatial distribution characteristics based on M-CPI indicate that the water quality of the lower reaches of Longgang River, the tributaries Dingshan River and Huangsha River, is relatively poor. In addition, the water environment improvement process of Longgang River can be divided into 3 stages: engineering stage (2007-2013, rating changed from heavily polluted to basically qualified), bottleneck stage (2013-2017, rating fluctuated slightly above and below basically qualified), and ecological restoration stage (2017-2020, rating reached qualified in 2019).

Magnetic susceptibility and heavy metal contents in sediments of Riam Kiwa, Riam Kanan and Martapura rivers, Kalimantan Selatan province, Indonesia

Kalimantan Selatan is proud of the Martapura River's natural and cultural history. Martapura tributaries include Riam Kanan and Kiwa. The Martapura River is essential because it provides clean water and a livelihood for riverside residents. Human-caused river pollution grows with population density (also known as anthropogenic pollutants). This study characterizes surface sediment magnetic characteristics and heavy metal contents along the Riam Kanan, Riam Kiwa, and Martapura rivers. The purpose of this research is to evaluate the magnetic signal with respect to heavy metal contents found in surface sediments taken from rivers and to confirm the use of the rock magnetism method in environmental studies in the study area. Surface sediment samples were gathered and tested for magnetic, heavy metal, and mineralogical content. According to the findings, the pseudo-single domain (PSD) magnetite mineral predominates among the magnetic minerals that can be found in the surface sediments of the rivers Riam Kanan, Riam Kiwa, and Martapura. This substantially greater grain size may be due to magnetic particles produced by erosion along the river banks. The mass-specific magnetic susceptibility of surface sediments ranges from 103.11 to 1403.64 × 10^-8 m³/kg, with an average value of 355.67 × 10^-8 m³/kg due to the peatland environment. Magnetic susceptibility strongly negatively correlates with heavy contents like Cu, Zn, and Hg, according to Pearson correlation analysis. Due to this correlation, magnetic susceptibility may indicate heavy metal pollution in certain rivers. This current study demonstrates the novelty of the relationship between magnetic susceptibility and the contents of heavy metals in surface sediments from rivers in peatland and tropical environments by illustrating how the relationship affects the magnetic susceptibility of the sediments.

Vertical distribution, contamination status and ecological risk assessment of heavy metals in core sediments from a mangrove-dominated tropical river

Understanding the vertical distribution of heavy metals aids in tracing the contamination history, however, it is limited for mangrove-dominated river. Thus, this study aimed to assess the vertical distribution of nine heavy metals and their possible ecological risk in several layers of core sediments from a mangrove-dominated river inside the Sundarban mangrove forest (World heritage and Ramsar site), Bangladesh. 45 core samples from five stations were analyzed using Flame Atomic Absorption Spectrophotometer (FAAS). The findings showed that, with the exception of Fe, Ni, and Cu, which suggested increased metal release in recent times, higher metal levels were recorded in the surface layer (0-10 cm), followed by the middle layer (10-20 cm), and inner layer (20-30 cm) of sediment cores. When compared to non-industrial forest sediment, core sediment from industrial sites contained noticeably more metals (p < 0.05). Overall, the mean metal concentration (mg/kg) followed the increasing order of Cd < As < Pb < Cu < Cr < Zn < Ni < Mn < Fe. Among the studied metals, the levels of Cd and Ni exceeded the average shale value. Contamination indices such as enrichment factor (EF), contamination factor (CF), and geo-accumulation index (I_geo) showed that the studied sediments were only contaminated by Cd. Ecological risk assessed by ecological risk factor (E_rⁱ) and risk index (RI) suggested that the analyzed heavy metals, with the exception of Cd, posed no significant ecological threats. All of the heavy metals analyzed might have originated from similar anthropogenic sources, according to the correlation matrix, cluster analysis (CA), and principal component analysis (PCA).

A baseline study of microplastic pollution in a Southern Indian Estuary

Knowledge on the processes controlling the vertical distribution of microplastics (MPs) in estuaries is less. This research was carried out to determine the MP distribution in the surface, middle, and bottom layers of the Udyavara River Estuary in southwest India. The mean (± standard deviation) concentrations were 320.83 (± 98.30), 514.55 (± 352.16), and 755.03 (± 400.96) particles/m³, respectively. Fibres, films, and fragments dominated, and 57 % of the MPs had a size range of 0.3-1 mm, while 43 % had a size of 1-5 mm. The main polymers were high-density polyethylene and polyethylene terephthalate. A positive correlation (r = 0.421, p = 0.0205, n = 30) exists between the MPs and salinity, suggesting that the MPs are held by dense saline waters. The mean pollution load index value was 2.25 indicating severe pollution. Microplastic pollution is due to harbour, fishing, industrial activities, the effects of southwest monsoon rain, and tidal currents.

Streambed pollution: A comprehensive review of its sources, eco-hydro-geo-chemical impacts, assessment, and mitigation strategies

Streambeds are an integral part of the river ecosystem. They provide habitat to a vast array of aquatic and benthic organisms as well as facilitate the bio-degradation and transformation of organic matter and vital nutrients. Increasing anthropogenic influence introduces multiple stressors to the stream networks resulting in pollution of streambeds, which in turn, have detrimental effects on the overall stream ecosystem health. There is a huge gap in the current understanding of streambed pollution and its impacts, and the widely practiced streambed pollution mitigation strategies lack a holistic approach. In this comprehensive review, we first synthesize the state-of-the-art knowledge of conventional and emerging forms of contaminants, their overall impacts on stream ecosystem functions, and present future directions to comprehend the problem of streambed pollution. We highlight that fine sediments and plastics (found especially in urban streambeds) are among the major physical pollutants causing streambed pollution and the chemical pollutants generally comprise hydrophobic compounds including various legacy contaminants such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT), a wide range of pesticides and a variety of heavy metals. Moreover, in recent years, highly polar and hydrophilic emerging contaminants such as micro-plastics, pharmaceutical waste and personal care products have been identified in riverbeds and streambeds across the world. We stress that the impacts of streambed pollution have been largely studied with discipline-driven perspectives amongst which the ecological impacts have received a lot of attention in the past. To present a comprehensive outlook, this review also synthesizes and discusses most of the understudied hydrological, geomorphological and biochemical impacts of different forms of streambed pollution. Subsequently, we also present a global inventory by compiling information from the published literature to highlight the status of streambed pollution around the globe. In the end, we endorse the positive and negative aspects of the current impact assessment methodologies and also highlight various physical, chemical and biological remediation measures that could be undertaken to alleviate streambed pollution.

Spatial variation and ecological risk assessment for heavy metals in marsh sediments in Fuzhou reach of the Min River, Southeast China

To explore the pollution levels, sources and risks of heavy metals in sediments in Fuzhou reach of the Min River, the sediments involving in seven marsh types were sampled. Results showed that the concentrations of Pb, Zn and Cd in sediments declined from freshwater segment to estuarine segment. Higher levels of Cu, Cr and Ni in sediments generally occurred in estuarine segment. The highest levels of Pb and Cd were observed in bush swamp, while those of Cr, Ni, Zn and Cu occurred in mudflat. Cr, Cu, Zn and Ni probably shared common source, while Pb and Cd originated from another source. Pb and Cd were identified as heavy metals of primary concerns and the former showed high potential toxicity and high contributions to ΣTUs. Next step, the metal pollutions in sediments might be more serious if effective measures were not taken to control the loading of pollutants.

A Food-Safety Risk Assessment of Mercury, Lead and Cadmium in Fish Recreationally Caught from Three Lakes in Poland

Simple Summary

The research aimed to determine the content of lead (Pb), cadmium (Cd), and mercury (Hg) in water, sediment, and freshwater fish species roach (Rutilus rutilus), perch (Perca fluviatilis), and pike (Esox lucius) from the Dratów, Syczyńskie, and Czarne Sosnowickie lakes located on Polesie Lubelskie, Poland, as well as a food safety assessment for the consumer. Pb and Cd were measured by graphite furnace atomic absorption spectrometry, while Hg was measured by cold vapor atomic absorption spectrometry. The research results showed that both the waters and the sediments of the studied lakes are characterised by a low concentration of Pb, Cd, and Hg, which indicates the lack of a moderate influence of anthropopressure on these reservoirs. The range of heavy metal contents in the muscles of roach, pike, and perch for Pb was 0.0399–0.1595, 0.0305–0.0920, and 0.0296–0.1057 mg kg⁻¹, respectively; for Cd 0.0014–0.0095, 0.0010–0.0015, and 0.0020 mg kg⁻¹, respectively; and for Hg 0.0123–0.0499, 0.0185–0.0255, and 0.0216–0.0583 mg kg⁻¹, respectively. The content of heavy metals in fish muscles was low and conformed to requirements as defined in the European Union (EU) food legislation. The health risk assessment with regard to the heavy metal contents in the muscles of fish confirmed the safety of this food for consumers.

Abstract

Heavy metals are introduced into water due to anthropogenic activities and can significantly affect an entire ecosystem. Due to their close integration with the water environment, fish are a sensitive indicator of contamination. In addition, fish is an important element in human diets, therefore, monitoring the concentrations of metallic contaminants in their meat is particularly important for food safety. This study aimed to assess the pollution of water ecosystems with selected toxic heavy metals in lakes Dratów, Czarne Sosnowickie, and Syczyńskie. The concentration of Pb, Cd, and Hg in water, sediment, and freshwater fish muscle tissue was determined, and a food safety assessment was performed. The analysis of water and sediments showed that the sediments were characterised by a significantly higher concentration of heavy metals. Presumably, this ecosystem element plays an important role in the uptake of heavy metal contaminants by fish whose levels were higher in planktonophagous and benthophagous fish species as compared to predatory fish. The food safety assessment showed that amounts of heavy metals in the muscle tissue posed no threat to the health of consumers ingesting that fish species, neither individually (THQ) nor collectively (TTHQ).

Assessment of metal enrichment and contamination in surface sediment of Mandovi estuary, Goa, West coast of India

Metal concentration in the sediments was determined to assess the metal enrichment and level of contamination in the Mandovi estuary. The metal distribution in the Mandovi estuary revealed preferential input through open-cast iron-ore mining, industrial, fishing, and agricultural activities. The heavy riverine runoff associated with high rainfall influenced the distribution of Mn, Zn, and Pb during monsoon season. In addition, sediment grain size and associated organic matter governed metal distribution in surface sediments. The role of grain size and organic matter along with Fe-Mn oxides in the distribution of metals was construed through correlation and factor analysis. Geo-accumulation index, contamination factor, and potential contamination index indicated contamination of surficial sediments of the Mandovi estuary with Cr and Pb.

Occurrence, distribution, and pollution indices of potentially toxic elements within the bed sediments of the riverine system in Pakistan

Potentially toxic elements (PTEs) are a major source of pollution due to their toxicity, persistence, and bio-accumulating nature in riverine bed sediments. The sediment, as the largest storage and source of PTEs, plays an important role in transformation of mercury (Hg), lead (Pb), nickel (Ni), chromium (Cr), copper (Cu), zinc (Zn), and other toxic PTEs. Several important industrial hubs that contain a large population along the banks of different rivers, such as Kabul, Sutlej, Ravi, Jhelum, and Chenab in Pakistan, are acting as major sources of PTEs. In this study, 150 bed sediment samples (n=30 from each river) were collected from different sites. Total (acid extracted) PTE (Hg, Cu, Cr, Ni, Zn, and Pb) concentrations in bed sediments were determined using inductively coupled plasma mass spectrometry (ICP-MS). Sediment pollution indices were calculated in the major rivers of Pakistan. The results demonstrated high levels of Hg and Ni concentrations which exceeded the guideline standards of river authorities in the world. The contamination factor (CF) and contamination degree (CD) indices for Hg, Ni, and Pb showed a moderate to high (CF≥6 and CD≥24) contamination level in all the selected rivers. The values of geo-accumulation index (I_geo) were also high (I_geo≥5) for Hg and Pb and heavily polluted for Ni, while Cr, Cu, and Zn showed low to unpolluted (I_geo) values. Similarly, the enrichment factor (EF) values were moderately severe (5≤EF≤10) for Hg, Pb, and Ni in Sutlej, Ravi, and Jhelum, and severe (10≤EF≤25) in Kabul and Jhelum. Moreover, Hg and Ni showed severe to very severe enrichment in all the sampling sites. The ecological risk index (ERI) values represented considerable, moderate, and low risks, respectively, for Hg (The ERI value should not be bold. Please unbold the  ERI in the whole paper. It should be same like RI, CD and EF. [Formula: see text]≥160), Pb and Ni (40≤[Formula: see text]≤80), and Cr, Cu, and Zn ([Formula: see text]≤40). Similarly, potential ecological risk index (PERI) values posed considerable (300≤RI≤600) risk in Ravi and moderate (150≤RI≤300) in Kabul and Jhelum, but low (RI≤150) risk in Ravi and Chenab. On the basis of the abovementioned results, it is concluded that bed sediment pollution can be dangerous for both ecological resources and human beings. Therefore, PTE contamination should be regularly monitored and a cost-effective and environmentally friendly wastewater treatment plant should be installed to ensure removal of PTEs before the discharge of effluents into the freshwater ecosystems.

Traceability and Emission Reduction of Dissolved Inorganic Nitrogen in Minjiang Estuary, China

The accumulation of dissolved inorganic nitrogen (DIN) in estuaries has become a global environmental problem. A two-dimensional, hydrodynamic water quality model was constructed in this study to investigate the sources of DIN pollution in the Minjiang Estuary. The concentration response field between the stream input and DIN in the estuary was established by using the surveyed source data of the study area. A sharing coefficient method was used to calculate the contribution percentage of each outfall to derive and propose a reasonable nitrogen reduction plan. The results showed that the input of land-based nitrogen into the Minjiang River contributed more than half of the DIN in the near-shore sea; the middle and upper reaches of the Minjiang River largely influenced the estuary area (38.57%). Conversely, the estuary and the coastline accounted for a smaller proportion of only 5.24%, indicating that an integrated DIN reduction should be implemented in the estuary area of the whole river basin. The model calculations showed that the reduction results, after remediation according to the current national standards for wastewater discharge in rivers, were not satisfactory. Thus, a new scheme is proposed in this paper-the total nitrogen (TN) input from land-based sources into the Minjiang Estuary and from the Shuikou Dam to the Min'an section should be reduced to below 31.64%; simultaneously, the DIN concentration discharged from the Shuikou Dam should be controlled and maintained below 0.5 mg·L^-1 (TN = 0.8 mg·L^-1). These results will provide guidelines for developing strategies for the improvement of DIN and water quality in similar estuaries.

Sediment record of heavy metals over the last 150 years in Northeast China: implications for regional anthropogenic activities

Evidence from terrestrial sedimentary heavy metals record is a robust indicator of anthropogenic activity changes. Heavy metals and particle sizes in ²¹⁰Pb-dated sediment cores extracted from Hulun and Chagan lakes were measured to reconstruct the sediment record and evaluated health risk of heavy metals in the last 150 years in Northeast China. In general, the particle size of Hulun Lake was finer with more contents of clay than Chagan Lake, while the concentrations of most heavy metals in Hulun Lake was lower. Prior to the 1970s, significant positive correlations between most heavy metals and clay, indicating that that they were likely co-transported and both lakes were dominated by natural inputs. The two records showed significant increases in concentrations of heavy metals between 1970s and 1990s, which were associated with recent anthropogenic activities derived from principal component analysis of clay and heavy metals. Specifically, the exploitation of mineral resources and traffic source in the Hulun Lake, and the emissions of pesticides and fertilizers from agricultural activity, and the combustions of coal and fossil fuels from industrial activity in the Chagan Lake. Since 1990s, natural processes was the main source of heavy metals in Hulun Lake due to the environmental protection policy, while emissions of industrial, agricultural and domestic sewage were still the main source in Chagan Lake. Overall carcinogenic risks caused by single heavy metal elements determined for the two lakes were considered to be acceptable. However, Cr was associated with a risk for children across since 1970s which should be paid more attention.

Occurrence of microplastics and heavy metals accumulation in native oysters Crassostrea Gasar in the Paranaguá estuarine system, Brazil

The ubiquitous presence of contaminants in the marine environment is considered a global threat to marine organisms. Heavy metals and microplastics are two distinct classes of pollutants but there are interactions between these two stressors that are still poorly understood. We examined the potential relationship between heavy metals (Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Ba, Hg, Pb) and microplastic particles in oysters sampled along the Paranaguá Estuarine System. The results suggested high levels of As and Zn in the bivalves, which are destined for human consumption. Microplastic particles were found in oysters from all sampled locations, demonstrating the spread of this pollutant in the marine environment and its ability to bioaccumulate in oysters. However, our data did not demonstrate a direct relationship between microplastics and heavy metals, suggesting that these particles are not the main route for heavy metal contamination of oysters in the Paranaguá Estuarine System.

The concentration distribution and biohazard assessment of heavy metal elements in surface sediments from the continental shelf of Hainan Island

The level of heavy metals (Cr, Co, Ni, Cu, Zn, and Pb) and Al₂O₃ were quantified in 140 surface sediment samples from the continental shelf of Hainan Island (CSHI). The mean heavy metal concentration in the decreasing order was: Cr > Zn > Pb > Ni > Cu > Co. Although heavy metals were locally enriched in the CSHI, the overall pollution level was relatively low. The biohazard assessment results of the mean effects range-median quotient (M-ERM-Q) and hazard quotient (HQ) for a single metal element (Cu, Pb, Zn) in the surface sediments showed that the exposure to individual heavy metals posed a low health risk. However, the biohazard assessment of multiple metals was higher than the single metals. Particular attention should be paid to the potential biological hazard from Cr and Ni in the CSHI.

Underestimated heavy metal pollution of the Minjiang River, SE China: Evidence from spatial and seasonal monitoring of suspended-load sediments

Previous assessments on rivers in SE China with highly developed economy and enormous population indicate diverse and relatively low particulate heavy metal pollution levels. However, the controlling mechanisms for heavy metal enrichment and transport remain enigmatic. Here, we target a mesoscale mountainous river, the Minjiang River, and obtain grain size, mineralogical and heavy metal concentration (Pb, Cd, Cr, Mn, Mo, Zn, V, Co, Ni, Cu) data from seasonal suspended particulate matter (SPM) near the river mouth, riverbed sediments and SPM samples from mainstream and major tributaries of the river. The results indicate that SPM samples have higher particulate heavy metal concentrations than riverbed sediments collected in pairs. Heavy metal concentrations of Cd, Zn, Cr, V, Co, Ni and Cu are higher in upstream SPM samples than those in downstream regions, whereas Pb, Mn and Mo concentrations don't show this spatial variation. Most heavy metals (e.g., Pb and Zn) show high concentrations in flood seasons and relatively low concentrations in dry seasons, revealing a hydrologic control. However, Cr and Mn show high concentrations in some dry season samples, suggesting incidental anthropogenic input events. The SPM-based pollution assessments using enrichment factor, geoaccumulation index and potential ecological risk index demonstrate that the Minjiang River is moderately to strongly polluted by particulate Pb, Cd, Mo and Zn contaminations and most particulate heavy metals have moderate to considerable potential ecological risks. We contend that transport and discharge of particulate heavy metals by the Minjiang River are controlled by both natural and anthropogenic forcings and the pollution levels are worse than previously known. Our findings suggest that particulate heavy metal discharge by subtropical mountainous rivers is related to sediment types and hydrologic characteristics. Therefore, high-spatiotemporal-resolution investigations on river SPM samples are highly recommended to better evaluate particulate heavy metal pollution levels and aquatic environmental conditions.

Insights into leaded gasoline registered in mud depocenters derived from multivariate statistical tool: southeastern Brazilian coast

Lead has been widely used since antiquity, but its uses drastically increased during the Industrial Revolution. The global emission of Pb into the environment was mainly due to tetraethyl lead added to gasoline as an antiknock additive. Because of its toxicity and neurological effects, the compound was phased out in the 1980s. Isotopic signatures are widely applied to differentiate sources of Pb; however, this is an expensive and sophisticated analysis compared to elemental analysis. Thus, this study aims to gain insight into leaded gasoline registered in mud depocenters from the southeastern Brazilian coast using multivariate statistical tools on elemental analysis data of trace elements. Seven multiple cores were collected on board the Research Vessel Alpha Crucis. Al, As, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, Sc, Sr, V and Zn were analyzed by acid digestion and quantified by ICP-OES. Levels and enrichment factors of Pb resulted in homogeneous columns, indicating that small variations in concentrations can be attributed to grain size differences, not presenting contaminated levels. From statistical results, the highest contribution on the first component was represented by a lithogenic source with the leaching of continental rocks. Lead content was notable in its high loadings in other components, which suggests atmospheric deposition. An increase in these components in subsurface samples from vertical profiles between 1935 and 1996 could represent a fingerprint of the consumption of leaded gasoline in Brazil between 1923 and 1989. Thus, statistical analysis of elemental data enabled to infer possible sources and pathways of Pb to the environment, without isotopic analysis.

Geochemical background indicators within a tropical estuarine system influenced by a port-industrial complex

This study aims to determine the background values for metals in the Suape estuarine system, Brazil, and to identify contamination caused by anthropogenic sources. Two cores were sampled. Sedimentation rates and metal content were analysed. The Al-normalized method was used to infer the background values, and to identify anthropic influences, the enrichment and contamination factors and the geoaccumulation index were employed. The results revealed an Mn, Ni, Zn, Ga, Pb, Sr, Ti, Mg, V and Fe content (mg kg^-1) of 101.8, 5.7, 24.4, 8.3, 14.5, 41.9, 2744.6, 4581, 14.9 and ~ 1% respectively. After the installation of the Suape port, an increase in metal contents and in fluxes were recorded. Increases in Zn, Ga, V and Pb are supported by the indexes showing moderate contamination, enrichment and suggest an area moderately polluted. The other studied metals do not reflect an anthropogenic impact, with low values of contamination, enrichment factors and geoaccumulation indexes.

Impacts of copper and lead exposure on prokaryotic communities from contaminated contrasted coastal seawaters: the influence of previous metal exposure

Our understanding of environmental factors controlling prokaryotic community is largely hampered by the large environmental variability across spatial scales (e.g. trace metal contamination, nutrient enrichment and physicochemical variations) and the broad diversity of bacterial pre-exposure to environmental factors. In this article, we investigated the specific influence of copper (Cu) and lead (Pb) on prokaryotic communities from the uncontaminated site, using mesocosm experiments. In addition, we studied how pre-exposure (i.e. life history) affects communities, with reference to previous metal exposure on the response of three prokaryotic communities to similar Cu exposition. This study showed a stronger influence of Cu contamination than Pb contamination on prokaryotic diversity and structure. We identified 12 and 34 bacterial families and genera, respectively, contributing to the significant differences observed in community structure between control and spiked conditions. Taken altogether, our results point toward a combination of direct negative responses to Cu contamination and indirect responses mediated by interaction with phytoplankton. These identified responses were largely conditioned by the previous exposure of community to contaminants.

Assessment of heavy metal contamination in surface sediments in the western Taiwan Strait

The concentrations of the heavy metals Cu, Pb, Zn, As, Cr, Co, and Ni of a total of 187 surface sediment samples collected from the western Taiwan Strait were analyzed. The distribution characteristics and degree of contamination of these elements were investigated. The mean concentrations of Cu, Pb, Zn, As, Cr, Co, and Ni in the surface sediments of the study area were 10.2 mg/kg, 18.3 mg/kg, 51.7 mg/kg, 7.5 mg/kg, 38.7 mg/kg, 8.0 mg/kg, and 16.5 mg/kg, respectively. The heavy metals in the study area were mainly from natural sources. The regional pollution load index (PLIzone) was 0.64, indicating that there was no contamination, and an area with a relatively high PLIzone was found in the northern part of the study area. Furthermore, the impacts of the rapid development of Fujian's marine economy on the marine environment in the past decade should be further compared and analyzed.

Elemental Contaminants in Surface Sediments from Jiulong River Estuary, China: Pollution Level and Ecotoxicological Risk Assessment

Estuaries, being the transitional zones between freshwater and marine environments, are important for protecting and rehabilitating the aquatic environments. Sediments from freshwater and marine environments were studied in Jiulong River Estuary (JRE) in different years for rare earth elements (REEs) and some environmentally important metal and metalloid elements (MMEs). The concentration of REEs ranged from 0.11 (Tm) to 296.20 mg kg−1 (Ce), while that of MMEs ranged from 0.40 (Cd) to 86,000 mg kg−1 (Al). The temporal analysis indicated an increase of both REEs and MMEs contaminants from 2012 to 2018. Fractionation of REEs and Ce and Eu anomalies indicated natural weathering, erosion processes and changes in redox chemistry at the sampling sites. Spatial structure analysis showed relatively higher levels of both REEs and MMEs in the freshwater sediments. These variations among the sampling sites indicated different land use and anthropogenic activities. The values of enrichment factor (EF) and geoaccumulation index (Igeo) indicated anthropogenic sources of accumulation, while, ecological risk assessment (Eix) and potential ecological risk index (PERI) indicated potential hazards for biota due to the accumulation of Pb, Zn and As elements.

Iron mineralogy and speciation of sediment iron-bearing minerals in mangrove forest: Case study of Zhangjiang estuary, China

Few investigations of iron speciation exist in intertidal conditions with little attention given to understanding the geochemical behavior of Fe³⁺-Fe²⁺ and its biogeochemical processes. Here, one sediment core was collected in Yunxiao mangrove forests, Zhangjiang estuary, China and iron mineralogy was determined by magnetic methods and Mössbauer spectroscopy. Changes in magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, and saturation isothermal remanent magnetization were linked to changes of pseudo-single domain soft coercive components with minor antiferromagnetic fractions and the presence of minimal concentrations of superparamagnetic particles was confirmed by the no frequency dependent of AC magnetization. A positive correlation between L-ratio and hard isothermal remanent magnetization is congruent with the distribution of high-coercivity antiferromagnetic minerals. At 295 K, the Mössbauer spectrum of specimens was well fitted with a single magnetic sextet, hematite and two magnetic doublets, paramagnetic Fe²⁺ and paramagnetic Fe³⁺. The usefulness of magnetic data and Mössbauer spectroscopy could offer valuable analytical tools for tracking changes of iron speciation and phase in the intertidal conditions.

Spatial-temporal distribution and transport flux of polycyclic aromatic hydrocarbons in a large hydropower reservoir of Southeast China: Implication for impoundment impacts

In order to investigate the impacts of dam-related water impoundment on the spatial-temporal variations and transport of anthropogenic organic pollutants, 15 priority polycyclic aromatic hydrocarbons (PAHs) were analyzed in water samples from the Shuikou Reservoir (SKR) of the Minjiang River. The SKR was formed after the construction of the Shuikou Dam, which is the largest hydropower station in Southeast China. The water samples were collected from the backwater zone of the SKR, in both the wet and dry seasons, corresponding to the drainage and impoundment periods of water flow, respectively. The concentrations of the dissolved PAHs in surface water from the wet season (average of 161 ± 97 ng L^-1) were significantly higher (ANOVA, p < 0.01) than those from the dry season (average of 43 ± 21 ng L^-1). PAH concentrations in the SKR decreased from upstream (industrialized cities) to downstream (rural towns or counties), indicating high PAH loads caused by intensive urbanization effects. The high proportions of 3-ring PAHs in the wet season were from local sources via surface runoff; while the elevated proportions of 4- to 6- ring PAHs in the dry season reflected atmospheric deposition emerged of these PAHs and/or volatilization of 3-ring PAHs enhanced. Molecular diagnostic ratios of PAH isomers in multimedium and principal component analysis indicated that PAH presence in the SKR was mainly attributed to pyrogenic origin. The isomeric ratios of fluoranthene to fluoranthene plus pyrene in the wet season were homogeneous, implying that there were continuous new inputs along the riverine runoff. However, these ratios showed spatial downward trend in the dry season, indicating continued degradation of PAHs occurred along the transport path during the impoundment period. The input and output fluxes of PAHs in the SKR were 5330 kg yr^-1 and 2991 kg yr^-1, revealing that the reservoir retained contaminants after impoundment of the hydropower dam.

Behaviour of metals in an urban river and the pollution of estuarine environment

The high pollutant loads discharged from cities pose risks to urban waterways, and in turn the estuarine environments, making it challenging to improve urban liveability. Past studies on the behaviour of pollutants in rivers have largely investigated their transport along the waterway, primarily focusing on the movement of water and sediment. However, the current approaches in pollutant transport modelling provide limited insights into how pollutant transfer between water and sediment phases influences their transport from the upstream towards the estuarine environment. This research study firstly identified typical patterns of metal loads along an urban river in a highly populated city in China. The outcomes were then used to conceptualise metal transfer between water and sediment phases. It was noted that physico-chemical characteristics of water and sediments play a key role in metal transfer between the two phases, and the dominant transfer path (sediment to water/water to sediment) is different between different metals, independent of their origin (crustal, anthropogenic or marine-related). Several scenarios were derived from the conceptualisation of metal behaviour. These in turn were then used to develop real-world scenarios of metal transport in rivers based on the field data. The conceptualisation of metal behaviour confirmed that each metal is likely to have a dominant phase of transport (sediment/water), which is influenced by the dominant transfer path of that metal between water and sediments.

Geochemical and probabilistic human health risk of chromium in mangrove sediments: A case study in Fujian, China

Deciphering the mobility and transfer of heavy metals in transition buffers is vital to understanding their behavior in mangrove forests. As one of the most redox-sensitive metals, the geochemical fractionation of sediment Chromium in mangrove forests and its health risks to the coastal fishermen folk is not clearly understood. This study investigated the current levels, enrichment, geochemical fractionation, and eco-toxicity on organisms of sediment Chromium from three mangrove forests in southeast China. A health risk assessment for different exposure pathways were also determined with Monte Carlo simulations technique. The results revealed that the concentration of sediment Chromium ranged from 30.75 mg kg^-1 to 99.28 mg kg^-1. The geochemical fractionations of sediment Chromium were mainly associated with amorphous Fe fraction, crystalline Fe fraction and residual fraction. Notably, 83.12% of samples analyzed in the residual phases of Chromium exceeded the background value of 40.7 mg kg^-1. Adverse effect index revealed a considerably negative effect on benthos occurrence in the mangroves. Values of non-carcinogenic risks were below unity at all samples, whereas the cancer risks associated with Cr(VI) exposure via fish consumption at median were close to 1.73 ×10^-5. A sensitivity analysis indicated that sediment Cr(VI) concentration and exposure frequency were the most relevant variables in the risk model. As the first attempt to provide information on the human health risks of sediment Chromium in mangrove forests in China, findings from this study can help track potential adverse effects and avoid risks from sediment Chromium.

Magnetic mineral characteristics, trace metals, and REE geochemistry of river sediments that serve as inlets to Lake Limboto, Sulawesi, Indonesia

This article presents magnetic mineral characteristics, trace metals, and REE geochemistry of river sediments that serve as inlets to Lake Limboto, Sulawesi, Indonesia related to article entitled “Lithogenic and anthropogenic components in surface sediments from Lake Limboto as shown by magnetic mineral characteristics, trace metals, and REE geochemistry” [1]. River sediments were obtained from three rivers, namely Alopohu, Bionga, and Talumelito. Sieved sediments were subjected to magnetic susceptibility measurements as well as geochemical analyses that include AAS analyses for trace metals and ICP-OES for REE. Extracted magnetic grains were also subjected to magnetic hysteresis analyses as well as XRD and SEM analyses. These data are invaluable in identifying the contribution of each river (and its catchment area) to the surface sediments of Lake Limboto.

Magnetic properties and correlation with heavy metals in mangrove sediments, the case study on the coast of Fujian, China

To characterize the magnetic signature of sediment heavy metal contamination and identify sources of heavy metals in mangroves, 83 sediment specimens were collected from three mangroves in Fujian, China; various magnetic parameters and heavy metal concentrations were then determined. Variation in magnetic magnetization among specimens was linked to changes in pseudo-single-domain magnetite. Average values of Co, Cu, Ni, and Zn (but not Cr or Pb) were slightly lower than background levels. Geochemical evidence suggested that Co, Cr, Ni, Ti, and V were associated with lithogenic minerals in the sediment, while Cu, Pb, and Zn were associated with terrigenous minerals. A strong positive correlation was seen between magnetic concentration-dependent parameters and metal concentrations (Cu, Pb, and Zn), suggesting enrichment of metal-containing magnetic minerals with heavy metal pollution. The combined assessment of both sediment magnetic properties and heavy metal concentrations thus provides insight into the pollution status of mangrove sediments under complex conditions.

Biomarker responses in oysters Crassostrea hongkongensis in relation to metal contamination patterns in the Pearl River Estuary, southern China

The Pearl River Estuary (PRE) is the third largest estuary in China, where estuarine organisms are under metal stress at various biological levels. Based on the metal concentrations measured in oyster Crassostrea hongkongensis, we documented a change in dominance of metal contamination from Cd, Cr, Cu, Ni and Zn to Ag, Cd, Cu and Zn. In general, metal concentrations were higher in upstream stations and displayed a clear up-downstream gradient. Compared to the historical values, we noted the reductions in Cd, Cr and Ni concentrations, and the changing inputs due to evolving industrial activities were responsible for shaping the metal contamination profile in the PRE region. Along with metal concentrations, a suite of biomarkers was analyzed. Among the metals measured in the oyster tissues, Ag, Cd, Cu, Ni and Zn showed the strongest associations with pro-oxidant and oxidative stress responses (superoxide dismutase, lipid peroxidation and lysosomal membrane destabilization) and detoxification responses (glutathione and metallothionein), suggesting that the present metal contamination still exerts significant amount of stress in biota in the PRE. Metal contamination in estuaries in China is still severe compared to other countries, therefore continuous efforts should be taken to monitor the changing metal profiles with necessary control and remediation measures.

Heavy metal contents and magnetic properties of surface sediments in volcanic and tropical environment from Brantas River, Jawa Timur Province, Indonesia

Brantas River is a largest urban river supplying raw water and drainage in Jawa Timur Province, Indonesia. Dense population along the river is a threat of pollution due to anthropogenic pollutants. In this study, we characterize the magnetic properties and heavy metal contents of surface sediments in various locations along the Brantas River. This study aims to enhance our understanding of the relationship between magnetic parameters and heavy metal contents in surface sediments from river. Surface sediment samples were taken and measured by a series of magnetic measurements, mineralogical analysis and heavy metal contents. The results show that magnetic minerals in surface sediments of Brantas River are dominated by PSD magnetite mineral. This relatively coarser grain size can be caused by magnetic particles produced by erosion around the river. Surface sediments have very high mass-specific magnetic susceptibility varying from 844.0 to 7231.4 × 10^-8 m³kg^-1 (on average of 3022.9 × 10^-8 m³kg^-1) because influenced by the surrounding volcanic environment. Magnetic susceptibility can identify and classify enrichment of heavy metals. Based on the Pearson correlation analysis, magnetic susceptibility has strong positive correlation with the heavy metal contents of ferromagnetic elements such as Fe and Co so that it can potentially be used as an indicator of pollution of both these heavy metals in the Brantas River. This present work shows the novelty of the relationship between magnetic susceptibility and heavy metal contents in surface sediments from river in volcanic and tropical environment.

Ecological risk assessment of metals in sediments and selective plants of Uchalli Wetland Complex (UWC)-a Ramsar site

Wetlands act as kidneys of land and facilitate remediation of metals and other harmful pollutants through uptake by aquatic macrophytes. The aim of the present study was to investigate metal concentrations in sediments and plants, sources of metal origin, and contamination level in Uchalli Wetland Complex. Sediment samples were collected from 15 randomly selected sites. Metal concentrations (Cd, Pb, Ni, Cu, Zn, Cr, As, Mn) in sediments and macrophytes were determined during summer and winter seasons using the inductively coupled plasma technique. Metal concentrations in sediments during summer and winter seasons were in the order as follows: As > Mn > Zn > Cr > Ni > Cd > Pb > Cu and As > Mn > Zn > Cr > Ni > Pb > Cd >Cu respectively. All analyzed metals were within European Union (EU) limits. In macrophytes, these metals were in the order as follows: Mn > As > Ni > Zn > Cr > Cd > Cu > Pb and As > Mn > Zn > Ni > Cr > Cd > Pb during summer and winter seasons respectively. Contamination degree (C_d) (1.023-5.309) for these lakes showed low contamination during both seasons; mC_d values (below 1.5) showed very little contamination degree, while the pollution load index (0.012 to 0.0386) indicated no metal pollution in these lakes. PCA applied on sediment showed that Pb, Zn, Cr, Cu, and Cd had anthropogenic sources of origin. As and Mn were due to natural processes while Ni could be resultant of both anthropogenic and natural sources. PCA on macrophytes showed that Ni, Pb, Cr, Zn, Cu; Cd, As; Mn had anthropogenic, natural, and anthropogenic + natural sources of origin. The study concluded that metal concentrations in sediments were not up to dangerous level.

First assessment on trace elements in sediment cores from Namibian coast and pollution sources evaluation

Trace elements (TEs), Rare Earth Elements (REEs) and Pb isotope ratios were determined in six small cores sampled along the Namibian coast and different indices, such as Enrichment Factor, Geo-accumulation Index and Pollution load index, were calculated to evaluate possible metal contamination in the area. Concentrations of Pb, Cu, As and Cd were strongly enhanced at the upper 7 cm of core C5, which is located at Walvis Bay, at the major harbor and urban/industrial center of Namibia, indicating the impact from the recent anthropogenic activities. Principal Component Analysis was applied to the data set indicating possible common sources of the contaminants. Pb stable isotope ratios, combined with the dating of core C5 at Walvis Bay, further confirmed the anthropogenic provenance of Pb sources in the recent sediment deposits, which occurred after 1945, when the anthropogenic activities in the area began to increase. REEs profiles were also determined, showing enrichment in REEs for some of the samples, typical for the minerals present in the area. Ce anomaly was detected in one of the cores but the REEs profile did not reveal anomalies ascribable to anthropogenic influence.

A multivariate approach and sediment quality index evaluation applied to Baixada Santista, Southeastern Brazil

Current studies use indices and chemometric approaches to assess the health quality of estuarine systems to support estuarine management. This study aims to use a multivariate approach and a set of indices to evaluate sediment health quality. Levels of Al, As, Cd, Cr, Cu, Fe, Ni, Pb, Sc, V, and Zn were quantified by ICP-OES, and nine indices were applied and evaluated individually. Most of the indices presented high values of Cu, Pb, and Zn, and the aggregative indices differed from each other in magnitude; however, the spatial distribution demonstrated the same trends. From PCA results, it was possible to differentiate lithogenic from the anthropogenic contribution, especially by Cu, Pb, and Zn. Thus, the integration of geochemical approaches and chemometric tools supported the interpretation of elemental contribution in terms of sources and pathway of heavy metals, which was similar to the results of other studies conducted in the area.

Spatial distribution and ecological risk assessment of sediment metals in a highly industrialized coastal zone southwestern Taiwan

Spatial variations of Cr, Cu, Hg, Ni, Pb, and Zn in the surface sediments from 34 stations of the Kaohsiung coastal zone southwestern Taiwan were studied to address the current pollution status, sediment quality, and potential ecological risk. The study revealed that the concentrations of sediment metals in Kaohsiung Harbor were alarmingly high compared to the other region of Kaohsiung coast. The concentrations of Cr, Cu, Hg, Ni, Pb, and Zn in the harbor sediments were as high as 351, 247, 1.93, 61.8, 60.9, and 940 mg kg^-1, respectively. The current situation of metal pollution was assessed by different pollution indices and results showed moderate to severe enrichment of Cu, Hg, and Zn in the harbor sediments. According to the degree of contamination, pollution load index, and contamination severity index, the sediments from the inner Kaohsiung Harbor show high degree and high severity of metal contamination, while the rest of Kaohsiung coastal areas show uncontaminated or low-level pollution. Results of mean ERM quotient and potential ecological risk index also indicated that the harbor sediments posed a 49% probability of biological toxicity and very high ecological risk. The toxic units indicated that the negative biological effects of the six metals in the harbor sediments were Zn > Cu > Cr > Ni > Hg > Pb. In contrast to Kaohsiung Harbor as a trap where considerable amount of anthropogenic metal loadings accumulated in sediments, low metal concentrations were observed in most Kaohsiung coastal sediments. It probably resulted from the limited fine-grained sediment deposition. In the wave-dominated Kaohsiung coastal zone, fine-grained sediments associated with polluted metals tend to be easily resuspended and transported offshore via waves and wave-induced currents. The results of this study can provide valuable information for river and coastal zone management.

Changes in Bacterioplankton Communities Resulting From Direct and Indirect Interactions With Trace Metal Gradients in an Urbanized Marine Coastal Area

Unraveling the relative importance of both environmental conditions and ecological processes regulating bacterioplankton communities is a central goal in microbial ecology. Marine coastal environments are among the most urbanized areas and as a consequence experience environmental pressures. The highly anthropized Toulon Bay (France) was considered as a model system to investigate shifts in bacterioplankton communities along natural and anthropogenic physicochemical gradients during a 1-month survey. In depth geochemical characterization mainly revealed strong and progressive Cd, Zn, Cu, and Pb contamination gradients between the entrance of the Bay and the north-western anthropized area. On the other hand, low-amplitude natural gradients were observed for other environmental variables. Using 16S rRNA gene sequencing, we observed strong spatial patterns in bacterioplankton taxonomic and predicted function structure along the chemical contamination gradient. Variation partitioning analysis demonstrated that multiple metallic contamination explained the largest part of the spatial biological variations observed, but DOC and salinity were also significant contributors. Network analysis revealed that biotic interactions were far more numerous than direct interactions between microbial groups and environmental variables. This suggests indirect effects of the environment, and especially trace metals, on the community through a few taxonomic groups. These spatial patterns were also partially found for predicted bacterioplankton functions, thus indicating a limited functional redundancy. All these results highlight both potential direct influences of trace metals contamination on coastal bacterioplankton and indirect forcing through biotic interactions and cascading.

Evaluating the applicability of MESS (matrix exponential spatial specification) model to assess water quality using GIS technique in agricultural mountain catchment (Western Carpathian)

The formation of many sources of pollution in a short period of time is due to mountain soil erosion by water. One of the major mechanisms decisive in the intensification of such erosion is the loosening of soil material on the slope. Water quality studies show the impact of diversified spatial management and allow making the right decisions in environmental management in mountain areas with high variability of use and land cover. The research undertaken as part of the paper was carried out in order to determine the dependency between total suspended solids (TSS) and the physicochemical parameters of surface waters and the amount of soil losses in the use structure within the mountain catchment. The paper focused on the frequency of phenomena in time and the possibility of stopping the surface runoff on the slope and on the soil's susceptibility to water erosion. The dependencies between multipoint sampling and the concentration of material washed off the slope due to precipitation were verified with a multivariate analysis. Sampling took place in hydrometric sections, and during small floods, in the waterbed cross section. Research shows that such sampling is the basis for the calculation of the transported load, reflecting the average variation in concentration. The variation in the volume of the load from the individual parts of the catchment was assessed by the spatial autoregressive model. It was found that the use of river basin areas affects water chemistry. Water reservoirs are an important ecological barrier for the migration of nitrate nitrogen (N-NO₃) and phosphate phosphorus (P-PO₄), which is marked by changes in the growing season. Water along the sections of the river near the quarry with a high degree of sodding showed good quality condition. Despite significant differences between measurement sampling sites, high total dissolved solid (TDS) values were found in communities adjacent to forests and meadows. However, the highest electrical conductivity (EC) and TSS concentrations were found in the interface with cultivated areas. Biogenic indices showed variation depending on the way the adjacent areas were used. GIS linked spatial variables with the formation of water pollution. The analysis of spatial autoregression pointed to the impact of arable land. Moreover, the analysis of spatial autoregression with the MESS function designated a connection between agricultural land use and nitrite nitrogen (N-NO₂), EC, TSS, and dissolved oxygen (DO). Graphical abstract ᅟ.

An 87-year sedimentary record of mercury contamination in the Old Yellow River Estuary of China

A sediment core, spanning from the year 1925 ± 3.03 to 2012, was collected for analyzing historical distribution of mercury (Hg) in the Old Yellow River Estuary (OYRE), China. The Hg concentrations in the sediment core ranged from 14 to 351 ng g^-1, with the high values occurred in the middle layers (1960-1996), which may be resulted from intensive human activities during this period, such as oil exploitation and booming of petrochemical industry, salt chemical industry and chlor-alkali plants. A significant positive correlation was found between THg and loss on ignition (LOI). The main fraction of Hg existed in residual part while the fraction that was easy to leach out from sediments accounted for only a small portion according to the results of BCR sequential extraction procedure. Multiple ecological risks indices and guidelines of Hg indicated that the sedimentary record presented an "intermediate state" for Hg contamination in the OYRE.

Heavy metals and arsenic content in water along the southern Caspian coasts in Iran

Due to the importance of pollution monitoring in marine ecosystems and lack of a coherent and systematic investigation of heavy metal ions along the southern shores of the Caspian Sea, in the present study, the amount of these metals and As ions in coastal waters along its 780-km-long coast in Iran have been studied. Heavy metals (cobalt, nickel, copper, zinc, cadmium, mercury, lead) and a poisonous metalloid (arsenic) were selected in 59 sampling stations and determined using differential pulse polarography method. The multivariate statistical tools were applied to describe and interpret the experimental data. The overall mean concentrations of studied metals (in microgram per liter; μg L^-1) in the samples were found in the order Zn (10.9) > Ni (7.4) > Cu (5.5) > Pb (1.9) > Hg (1.4) > As (1.3) > Co (1.1) > Cd (0.2). The results when compared with reported international standards confirmed that the sampled waters do contain some of these elements above the suggested maximum permissible limits. Hg and Cu were detected in 54.2 and 72.9% of the samples, almost all above the permissible limits. Ni, Zn, Pb, and Co were detected in 100, 96.6, 93.2, and 88.1%, respectively, while 8.5, 22.0, 3.4, and 1.7% were above the permissible limits. Cd and As were present in 61 and 93% of the samples, and their concentrations were higher than the rate presented by Russian System of Management Chemicals (RSMC). In addition, spatial distribution of heavy metal concentrations showed that Gorgan Bay is an ecosystem serving as a filter, trapping natural and anthropogenic materials that are brought from industrial, commercial, and urbanized areas. The multivariate data analysis reveals that Caspian Sea is contaminated by both anthropogenic as well as pedo-geochemical sources.

Distribution of heavy metals in seafloor sediments on the East China Sea inner shelf: Seasonal variations and typhoon impact

Based on concentrations and distributions of heavy metals, grain size and loss on ignition (LOI) in the seafloor sediments acquired during three surveys in winter and in summer (before and after typhoon Morakot) in the mud deposition center off the Fujian-Zhejiang coast, East China Sea, the seasonal and typhoon-induced variations of heavy metals in seafloor sediments are discussed. It is found that different concentrations of heavy metals occurred in seafloor sediments, but their distribution patterns were similar, gradually decreasing from near-shore to offshore. The distribution of heavy metals was correlated with grain size and LOI in seafloor sediments, which showed significant seasonal variations and typhoon's impact. Based on these results, a conceptual evolution model was built about the seasonal and typhoon's impact on the deposition environment of heavy metals, which has implications for understanding the migration, settling, and burial processes of heavy metals in the sea.

Geochemical Assessment and Spatial Analysis of Heavy Metals in the Surface Sediments in the Eastern Beibu Gulf: A Reflection on the Industrial Development of the South China Coast

The Beibu Gulf (also named the Gulf of Tonkin), located in the northwest of the South China Sea, is representative of a bay suffering from turbulence and contamination associated with rapid industrialization and urbanization. In this study, we aim to provide the novel baseline levels of heavy metals for the research area. Concentrations of five heavy metals (i.e., Cu, Pb, Zn, Cd and Cr) were determined in surface sediments from 35 sites in the eastern Beibu Gulf. The heavy metal content varied from 6.72 to 25.95 mg/kg for Cu, 16.99 to 57.98 mg/kg for Pb, 73.15 to 112.25 mg/kg for Zn, 0.03 to 0.12 mg/kg for Cd, and 20.69 to 56.47 mg/kg for Cr, respectively. With respect to the Chinese sediment quality criteria, sediments in the eastern Beibu Gulf have not been significantly affected by coastal metal pollutions. The results deduced from the geoaccumulation index (I_geo) showed that the study area has been slightly polluted by Pb, which might be caused by non-point sources. Relatively high concentrations of Cu, Pb and Cd were found around the coastal areas of Guangxi province, the Leizhou Peninsula and the northwest coast of Hainan Island, whereas the highest concentrations of Zn and Cr were found on the northwest coast of Hainan Island. Spatial distribution patterns of the heavy metals showed that bioavailable fractions of Pb were higher than in the residual fractions, while Cu and Cd concentrations in exchangeable and carbonate fractions were relatively higher than those in the bioavailable fractions. Hierarchical clustering analysis suggested that the sampling stations could be separated into three groups with different geographical distributions. Accompanying their similar spatial distribution in the study area, significant correlation coefficients among Cu, Cd and Pb were also found, indicating that these three metals might have had similar sources. Overall, the results indicated that the distribution of these heavy metals in the surface sediments collected from the Beibu Gulf was complex.

Altitudinal patterns and controls of trace metal distribution in soils of a remote high mountain, Southwest China

The aim of this study is to reveal the effects of regional human activity on trace metal accumulation in remote alpine ecosystems under long-distance atmospheric transport. Trace metals (Cd, Pb, and Zn) in soils of the Mt. Luoji, Southwest China, were investigated along a large altitudinal gradient [2200-3850 m above sea level (a.s.l.)] to elaborate the key factors controlling their distribution by Pb isotopic composition and statistical models. The concentrations of Cd, Pb, and Zn in the surface soils (O and A horizons) were relatively low at the altitudes of 3500-3700 m a.s.l. The enrichment factors of trace metals in the surface soils increased with altitude. After normalization for soil organic matter, the concentrations of Cd still increased with altitude, whereas those of Pb and Zn did not show a clear altitudinal trend. The effects of vegetation and cold trapping (CTE) (pollutant enrichment by decreasing temperature with increasing altitude) mainly determined the distribution of Cd and Pb in the O horizon, whereas CTE and bedrock weathering (BW) controlled that of Zn. In the A horizon, the distribution of Cd and Pb depended on the vegetation regulation, whereas that of Zn was mainly related to BW. Human activity, including ores mining and fossil fuels combustion, increased the trace metal deposition in the surface soils. The anthropogenic percentage of Cd, Pb, and Zn quantified 92.4, 67.8, and 42.9% in the O horizon, and 74.5, 33.9, and 24.9% in the A horizon, respectively. The anthropogenic metals deposited at the high altitudes of Mt. Luoji reflected the impact of long-range atmospheric transport on this remote alpine ecosystem from southern and southwestern regions.

Evaluation of heavy metal mobilization in creek sediment: Influence of RAC values and ambient environmental factors

The risk assessment code (RAC) is a common method for assessing heavy metal (HM) mobility and their potential health risks, based on HM total concentration and chemical speciation. In this study, both the RAC and the influence of ambient environmental factors were investigated in a river sediment system. Sixty-eight sediment samples were collected from the main river system in Shanghai, China. The total concentration and chemical speciation of Cu, Zn, Ni, Pb, Cd, Cr, As, and Hg were determined in the samples. The influence of sediment environmental factors, such as acid-volatile sulfide (AVS), Fe & Mn, and total organic carbon (TOC), on total metal concentrations and speciation was also investigated. The relationship between the main environmental media and distribution of HMs was discussed using PCA and NMDS. The transfer-transformation behaviors of Pb, Ni, and Cr were mainly controlled by AVS and TOC while Zn, Cu, and Cd were influenced by Fe & Mn and TOC. The relationship between the RAC value of HM and environmental factors revealed that 7% of Cr, 23% of Ni, and 15% of Pb had a high risk of mobility at TOC values below 3.5% and sulfite contents below 10mmol/kg. In comparison, 29%, 10%, and 10% of Zn, Cu, and Cd, respectively, had a high risk of mobility at TOC<3.5% and Fe & Mn content >4×10⁵mg/kg. Evidently, the chemical fractions of HM had a strong dependence on the S, Fe, Mn, and organic compounds in the sediment. This study provides a promising pathway for the rapid evaluation of potential risks from HMs in river sediments.

Risk assessment of trace metal-polluted coastal sediments on Hainan Island: A full-scale set of 474 geographical locations covering the entire island

Hainan Island is the second largest island and one of the most famous tourist destinations in China, but sediment contamination by trace metals in coastal areas is a major issue. However, full-scale risk assessments of trace metal-polluted coastal sediments are lacking. In this study, coastal surface sediments from 474 geographical locations covering almost the entire island were collected to identify risk-related variables. Controlling factors and possible sources of trace metals were identified, and the toxicity effects were carefully evaluated. Our results suggest that trace-metal pollution in coastal sediments, which was mainly caused by Pb, Zn and Cu emissions, has primarily resulted from industrial sewage and shipping activities and has threatened the offshore ecosystem of Hainan Island and warrants extensive consideration. This is the first study that has systematically investigated trace metal-polluted coastal sediments throughout the entirety of Hainan Island and provides solid evidence for sustainable marine management in the region.

Metals in Fishes from Yongshu Island, Southern South China Sea: Human Health Risk Assessment

In order to assess the bioaccumulation of metals associated with gender, tissues, and their potential ecological risk, four species of fish were collected from the Yongshu Island in the Southern South China Sea. Metals and stable Pb isotopes in their tissues (muscle, gill, liver, intestine, and ovary) were determined. The concentrations of metals (mg/kg, dry weight) in these species were ND-21.60 (Cd), 1.21-4.87 (Cr), 0.42-22.4 (Cu), 1.01-51.8 (Mn), 0.30-3.28 (Ni), 6.04-1.29 × 103 (Zn), 14.89-1.40 × 103 (Fe), and 0.22-3.36 (Pb). In general, the liver and intestine absorbed more metals than the other tissues. Metals accumulation can be influenced by gender and feeding behavior and in fact, female fish and dietary exposure are more prone to accumulate metals. In addition, Pb isotopic ratios indicated that all species had significant biological fractionation, which may not make them good tracers for source identification. The metal concentrations of most samples were lower than the national standard values of the FAO (USA), which suggested that human consumption of these species may not cause health risks. However, since the surrounding areas are developing rapidly, the potential environmental risk of metals will intensify and should receive more attention.