Distribution and risk analysis of heavy metals in sediments from the Yangtze River Estuary, China

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10-93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

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 %).

Spatial distribution and pollution assessment of metals in sediments along the industrialized coast of East Java, Indonesia

The eastern coastline of Gresik, located in East Java, Indonesia, experienced significant industrialization, leading to the development of numerous diverse sectors. These diverse industrial activities, in addition to other human activities, result in the contamination of sediment across the eastern coast of Gresik with a variety of metals. Metals like arsenic (As), cadmium (Cd), copper (Cu), and zinc (Zn) have exceeded the international standards for sediment quality, potentially causing significant harm to the aquatic ecosystem in this coastal region. The results of the multivariate analysis indicate that the metals found in the sediment are related to a combination of anthropogenic inputs, specifically those originating from industrial effluents in the area under study. Based on the assessment of enrichment factor, contamination factor, geo-accumulation index, degree of contamination, ecological risk index, and pollution load index, it can be concluded that the metals examined displayed different degrees of sediment contamination, ranging from minimal to severely contaminated.

Exploration of natural processes and anthropogenic inputs by Zn isotopes in suspended particulate matter: A case study from the Lancang River in Southwest China

River is an important pathway for the biogeochemical cycle of Zn. This study reports Zn concentration and δ66Zn composition for suspended particulate matter (SPM) from Lancang River basin in Southwest China, and explore the impact of natural processes and human activities on Zn cycle. The SPM samples have a much higher average Zn content (162 mg kg-1) than that of the upper crust (67.0 mg kg-1), but it is close to the value of the Pearl River (187 mg kg-1). The enrichment factor (EF) values of Zn in SPM range from 1.08 to 6.88, with an average of 2.15, which does not show significant pollution characteristics. The δ66Zn values in SPM range from -0.67‰ to +0.63‰, with an average of +0.13‰. The δ66Zn values showed positive correlation with Ca/Mg ratios while showed little correlation with Zn contents in SPM. It indicated that anthropogenic sources have limited influence on SPM, and the Zn isotope composition in SPM is more likely to be inherited from the weathered rocks materials and influenced by natural fractionation processes in river water. This result contributes to understanding of the geochemical cycling process of Zn and its environmental effects in water.

Potentially toxic metals in seawater, sediment and seaweeds: bioaccumulation, ecological and human health risk assessment

This study assesses the bioaccumulation, ecological, and health risks associated with potentially toxic metals (PTMs), including Pb, Hg, Cd, As, and Cr in Hare Island, Thoothukudi. The results revealed that the concentration of PTMs in sediment, seawater, and S. wightii ranged from 0.095 to 2.81 mg kg-1, 0.017 to 1.515 mg L-1, and 0.076 to 5.713 mg kg-1, respectively. The highest concentrations of PTMs were found in the S. wightii compared to seawater and sediment. The high bioaccumulation of Hg and As in S. wightii suggests that it can be used as a bioindicator for these elements in this region. The ecological risk indices, which include individual, complex, biological, and ecological pollution indices, suggest that Hare Island had moderate contamination with Hg and Cd. However, there are no human health risks associated with PTMs. This study examines the current ecological and health risks associated with PTMs and emphasizes the importance of regular monitoring.

Distribution, contamination assessment, and sources of heavy metals in surface sediments from the south of the North Yellow Sea, China

This paper reports the contents of six heavy metals and particle sizes in the surface sediments of 120 sampling stations in the southern North Yellow Sea to reveal heavy metal distribution characteristics, contamination assessment, and sources. Cu and Cr enrichments were mainly found in coastal areas with high mud content (silt and clay). However, Zn, Cd, Pb, and Hg were enriched in Weihai Bay and Dongpu Bay, which have denser populations, estuaries, and shipyards. The geoaccumulation index and principal component analysis showed that Cu and Cr contamination was low, and the sources were mainly natural processes. In addition, Zn and Cd pollution in the nearshore area was moderate, and its provenance was natural processes and human activity. However, most areas exhibited Pb and Hg contamination due to waterborne traffic and industries, including shipbuilding and gold mining.

Offshore freshened groundwater in the Pearl River estuary and shelf as a significant water resource

Large-river deltaic estuaries and adjacent continental shelves have experienced multiple phases of transgressions and regressions to form interlayered aquifer-aquitard systems and are expected to host vast paleo-terrestrial groundwater hundreds of kilometres offshore. Here, we used offshore hydrogeology, marine geophysical reflections, porewater geochemistry, and paleo-hydrogeological models, and identified a previously unknown offshore freshened groundwater body with a static volume up to 575.6 ± 44.9 km³ in the Pearl River Estuary and adjacent continental shelf, with the freshwater extending as far as 55 km offshore. An integrated analysis of stable isotopic compositions and water quality indices reveals the meteoric origins of such freshened groundwater and its significance as potential potable water or raw water source for desalination. Hotspots of offshore freshened groundwater in large-river deltaic estuaries and adjacent continental shelves, likely a global phenomenon, have a great potential for exploitable water resources in highly urbanized coastal areas suffering from freshwater shortage.

Seasonal heavy metal speciation in sediment and source tracking via Cu isotopic composition in Huangpu River, Shanghai, China

The present study systematically analyzed and evaluated the variations in chemical speciation, pollution assessment, and source identification of heavy metals in sediments of Huangpu River. The methods employed included heavy metal concentration, chemical speciation and Cu isotopic compositions analysis. Results showed that the chemical speciation of sediment-bound heavy metals, characterized by significant seasonal variation, shifted from non-residual fractions dominating in spring and summer to residual fractions dominating in autumn and winter. Precipitation was identified as an important factor influencing the chemical speciation of sediment-bound heavy metals. Furthermore, ratio of the secondary phase to the primary phase, RSP (=C_non-residual/C_residual) values in Huangpu River sediments were higher than 1 in spring and summer, indicating that sediment-bound heavy metals in Huangpu River were mainly composed of non-residual fractions and could potentially be released into the river water. Principal component analysis (PCA) revealed that navigation, traffic, agricultural, and industrial activities could be the potential sources of heavy metal pollution. Notably, the δ⁶⁵Cu values in Huangpu River sediments were observed to be isotopically lighter (from -0.37 to +0.18 ‰), suggesting that navigation might be the primary pollution source. These results will not only provide guidance in reducing heavy metal concentrations, but also serve as a crucial basis for policy making regarding heavy metal control.

Effect of river-lake connectivity on ecological stoichiometry of lake and carbon storage status in Eastern Plain, China

C, N, and P in lake sediment are the basis of material and energy cycle, reflecting the economic development, ecological function, and environmental effect. Current research on the effect of lake eutrophication on carbon storage and the river-lake connectivity on nutrient diffusion is lack. This work investigated the accumulation, distribution, correlations, and stoichiometric ratios of C, N, and P of 82 lakes (≥ 10 km²) in Eastern China, analyzed the nutrient limitation, sediment carbon sink, and effect of river-lake connectivity, and discussed the relationships between eutrophication and sediment carbon storage. The average concentrations and ranges of total C, N, and P in lake sediments were (23.26 mg/g, 0.08-153.45 mg/g), (2.32 mg/g, 0.29-14.17 mg/g), and (0.86 mg/g, 0.23-2.64 mg/g), respectively. The ecological stoichiometry of C: N: P in lake sediments was 32: 3.2: 1. P can be easily accumulated in lakes connected from the Yangtze River, while C and N can be easily accumulated in disconnected lakes. The soil-water erosion in runoff is an important factor for P diffusion. The C/N and C/N/P weren't affected by the river-lake connectivity but depended on the plant type. The Eastern Plain Lake Region of China is C and N co-depletion, and P enrichment. The lake eutrophication leading to algal bloom is unfavorable to the goal of carbon storage and carbon neutrality. Outcome of this study will provide a significant reference and strategies for carbon sequestration research, eco-environmental protection, and watershed nutrient management.

Heavy metals in the sediments of urban sinkholes in Cancun, Quintana Roo

Soils in urban areas can accumulate heavy metals as a result of anthropogenic inputs. This research focuses on a young coastal tourist city that has been urbanized over the last 52 years and shows accelerated demographic growth and urban development. Deposition of heavy metals in soils is caused by human economic activities, which has significant implications for the environment. We evaluated heavy metal concentrations in urban sinkholes, which are sites for the natural accumulation of water and sediments. These locations also receive rainfall runoff or have been used as unregulated dumps. By performing a multistage extraction to address availability and risk, we found that Zn, Fe and Al were the predominant metals; Cu, Pb and Ni were only detected in some sinkholes. The contamination factor was high for Zn and moderate for Pb. The geoaccumulation index showed that Zn is the most abundant and available metal in urban sinkholes and the metal with the highest potential ecological risk. Between 12 and 50% of the total concentration of all metals was extracted from the organic matter phase. Correlations were found between the degree of urbanization of the city and the degree of pollution, and the trends were stronger in older sections of the city. Zn is the most prevalent element and has high concentrations. The metal concentrations in the sediments can be used as warning signs for their potential risk to environmental and human health, and these results can be compared with those of other tourist cities in karstic environments around the world.

Effects of sedimentary heavy metals on meiobenthic community in tropical estuaries along eastern Arabian Sea

The central west coast of India comprises the 720 km long coastline of Maharashtra state and houses widespread industrial zones along the eastern Arabian Sea. Sediments from seven industrial-dominated estuaries along the central west coast were studied for metal enrichment and benthic assemblages to determine sediment quality status and ecological effects in these areas. The suit of geochemical indices highlighted the contamination of sediment in the estuaries concerning heavy metals. Positive correlations of Hg with Co, Zn, Ni, Cr, and Pb indicated the source similarity and effect of anthropogenic activity. non-Metric Multidimensional Scaling (n-MDS) based on meiofaunal abundance showed a cleared separation of clusters through the gradient of heavy metal concentrations. The Canonical Correspondence Analysis (CCA) results with the Monte Carlo test signified those heavy metals influenced the meiobenthic community. Heavy metals (Cr, Ni, Zn, Cd, Pb, and Hg) were the main drivers shaping the meiofaunal community with a significant (p < 0.05) reduction in taxa richness, diversity, and evenness. Dominant meiofaunal assemblages evidence the tolerance of foraminiferans and nematodes. However, these taxa were affected by decreased abundance at impacted sites compared to other fauna. In conclusion, results demonstrated that impairment occurred in the meiofaunal community in most estuaries (except AB and KK).

Spatiotemporal variations of heavy metal historical accumulation records and their influencing mechanisms in the Yangtze River Estuary

Complex transformations of heavy metals in the mega-river-estuary continuum limit our understanding of their pollution history. This study investigated sedimentary compositions of heavy metals, major elements, total organic carbon, grain size, and radionuclides to study spatiotemporal variations in heavy metal accumulation patterns and their controlling mechanisms in four sediment cores (E1-E4) from the Yangtze River Estuary (YRE). Results show that only E3 in the distal YRE front mirrors well the heavy metal pollution history due to its continuous deposition in a stable sedimentary environment, while E1 and E2 record the influence of riverine and estuarine projects and processes apparently. E1 in the proximal YRE front registers intense human disturbance through sediment dredging and dumping activities to produce a thick layer of abnormal low 210Pbex and minor heavy metal concentrations. E2 in the intermediate YRE front demonstrates the recently increasing influence of reduced sediment discharge by its upcore coarsening trend with decreased heavy metal concentrations. Flood and storm events left different imprints in core sediments of E2 and E3 by their coarse stratal units with fewer heavy metal concentrations. The source analysis indicates that heavy metals in estuarine sediments mainly come from natural processes but are significantly affected by human activities. A direct linkage of the heavy metal accumulation history with the socioeconomic development in recent decades is found by a comparison study of core data from the tidal river to the estuary, albeit with a remarkable spatiotemporal difference, which is jointly determined by grain size, offshore distance, hydrodynamic condition, depositional status, and sedimentation rate besides estuarine processes. This warns us to carefully interpret the heavy metal history from single or sparse core data in a mega estuary system with intense natural forces and human disturbances analogous to the YRE.

Significance of the great protection of the Yangtze River: Riverine input contributes primarily to the presence of PAHs and HMs in its estuary and the adjacent sea

The Yangtze River protection strategies are expected to improve the water quality and ecological function of the Yangtze River Estuary (YRE). The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 heavy metals (HMs) in the YRE were measured and the riverine fluxes were calculated subsequently. In particular, the concentrations of low molecular weight PAHs (LMW-PAHs), arsenic (As) and mercury (Hg) in seawater decreased over time, while those of other studied pollutants did not change a lot. In sediments, the concentration changes for all the pollutants were insignificant. For the present pollutants, the river input is the dominant source, and the flux decreased after the protection. The contribution of the discharge from wastewater treatment plants (WWTPs) was quantified. Its influence cannot be ignored. The seafood quality remained stable and the risk via diet was insignificant. Long-term monitoring is necessary, and the positive impact of the Protection Strategy is gradually emerging.

Reconstruction, assessment, and calibration of potential toxic elements (PTEs) in a 3500-year-long sedimentary record off the northern coast of Shandong Peninsula, China

The marine environment of coastal Shandong Peninsula has been significantly influenced by anthropogenic activities due to the rapid industrialization and economic development in the past decades. However, the sedimentary records of PTEs in the North Yellow Sea have rarely been reported. In this study, a 209-cm-long sediment core was collected off the northern coast of Shandong Peninsula, analyzed for grain size and elemental compositions, and assessed using EF, I_geo and several numerical Sediment Quality Guidelines (SQGs). The EF and I_geo results suggested that sediment profile could be slightly to moderately polluted with As and Sb, while ecological risk assessment using SQGs showed that As, Cr, Sb and Ni in the sediment profile may have a moderate incidence of toxicity. Our results highlighted the nonnegligible ecological risk of Sb in sediments of North Yellow Sea, and great importance should be attached to the fact that many PTEs may also pose a potential ecological risk to the aquatic organisms, even though their concentrations meet the standards of the Marine Sediments Quality (MSQ). Moreover, the reconstructed PTEs record showed a dramatic increase over the past 250 years, which could be related to the intense anthropogenic activities since the Industrial Revolution. The multivariate statistical analysis results indicated that Co, Cr, Cu, Pb, Ni and Zn may be mainly related to the natural origin, while As and Sb could be influenced by both natural weathering sources and anthropogenic activities. This study provides more insights into the historical record of PTEs in the North Yellow Sea, and lays foundation for future comparison of PTEs sedimentary records.

Research on the geochemical background values and evolution rules of lake sediments for heavy metals and nutrients in the Eastern China Plain from 1937 to 2017

For the first time, background quality guidelines have been developed for lake sediments along the Yangtze River. Evolution Rules of watershed environment in Eastern China were analyzed in 1937-2017. These methods of ¹³⁷Cs and ²¹⁰Pb radionuclide, 75% cumulative frequency, and background method were applied to calculate the sediment geochemical backgrounds (GB). The average GB values of Cu, Zn, Cd, Pb, Cr, total carbon (TC), total nitrogen (TN) and total phosphorus (TP) are 45.14 mg/kg, 86.99 mg/kg, 0.29 mg/kg, 33.71 mg/kg, 110.90 mg/kg, 17.20 mg/g, 1.60 mg/g, and 665.78 mg/kg, respectively. The radionuclide methods indicated that the sediment rate of 34 cm corresponding to 1963 is 0.63 cm yr^-1. The risk and accumulation of the sediment metals and nutrients in Yangtze Plain were uncontaminated levels before 1960, raised since 1980, and increased significantly in 2000. The Cd, TC, and TN in lake sediment were at low to moderate pollution, and few lakes are at high pollution. Sediment background values of the plain are different from soil background values in China and Consensus-Based Sediment Quality Guidelines in Europe/America. Results of sediment quality guidelines provide an important guidance for pollution prevention, environmental management, and risk assessment, especially the formulation of environmental laws.

Distribution and ecological risk of metals in an urban natural protected area in the Riviera Maya, Mexico

Urbanization can negatively impact natural protected areas near or surrounded by cities, and such impacts include untreated wastewater discharge, leachates from dumpsters, e-waste, and road dust. In this research, we show that not only large cities with industry are prone to be polluted, but also young touristic cities with high population increase rate can suffer from urban contamination. We evaluated metal pollution in a natural protected area within a 50-year-old city without conventional industry that was likely contaminated by the urban sprawl around the protected area. We tested water, zooplankton, sediment and plant samples for metallic elements to evaluate their bioaccumulation in zooplankton, enrichment factors and geoaccumulation index values in sediments, and translocation factors in plants. Finally, we evaluated the ecological risk due to metal contamination. Metals at levels above our detection limit (20 µg/L) were not found in the water and zooplankton samples. The sediments and plants in the storm drain section of the protected area had a greater concentration of metals and wastewater indicators (coliforms) than those in the rest of the lagoon. Moreover, signs of Al, Cu, Ni, Zn, Cr, Pb, and Ti contamination were found in the plant tissues. We estimated that the ecological risk of this natural protected area surrounded by the city of Cancun (Mexico) ranged from mild to strong, with Zn being the metal of most concern. The results highlight that young touristic cities around the world will endure contamination from urban sources; signs or early warnings of contamination must be identified to prevent and resolve such issues.

Spatial distribution and source identification for heavy metals in surface sediments of East Dongting Lake, China

Dongting Lake is one of the most important inland freshwater lakes in China. To investigate the spatial distribution and seasonal variation characteristics of heavy metals (Cr, Co, Cu, Zn, Cd, and Pb) in the lake, 53 surface sediment samples were collected in the East Dongting Lake (ED Lake) in the wet and dry seasons. Results show Cr, Co, Cu, Zn, Cd, and Pb contents were 1.7 (1.9), 1.8 (2.0), 2.9 (3.0), 1.9 (1.9), 11.7 (13.1), and 2.0 (2.2)-fold of their geochemical soil background values of Hunan province (China) in the wet (dry) season. Spatial and seasonal heterogeneity could be found in the distribution of Cr, Co, Cu, Zn, and Pb in the surface sediments. The enrichment factor (EF) suggested that Cd has reached severe enrichment in the sediment. The result of the geo-accumulation index (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${I}_{geo}$$\end{document}Igeo) indicated that Cr, Co, Cu, Zn, and Pb were at levels corresponding to low contamination, and moderately to highly polluted with Cd. Multivariate statistical analysis including pearson correlation analysis and principal component analysis was used for the identification of potential sources of the heavy metals in the sediments. The results showed that Cu, Zn, and Pb from the sediments of the East Dongting Lake in the wet and dry seasons were possibly anthropogenic sources, such as emissions from mining and smelting while Al, Fe, and Cr are attributed for natural sources. Cd enrichment in the sediments is influenced by both natural factors, and human activities in local areas.

Pollution, risks, and sources of heavy metals in sediments from the urban rivers flowing into Haizhou Bay, China

The Haizhou Bay in eastern China, for a long time, is seriously polluted with heavy metals (HMs) due to intensive anthropic pressure. The river runoff is the dominant pathway of HM transport in the coastal region. However, the information on HM pollution in coastal rivers flowing into Haizhou Bay was still limited, and potential risks and possible sources raised by HMs in this area were neglected up to now. To fully understand the distribution and ecological risks of sediments in seven rivers along the bay, surface sediments were collected and seven HMs (Cr, Mn, Ni, Cu, Zn, Cd, and Pb) were investigated. The results showed that HM concentrations generally met the primary standard criteria of China (marine sediment quality), except for Cu and Zn. On the other hand, Zn and Cu tended to exhibit probable adverse biological effects in the Shawang River comparison with some sediment quality guidelines (SQGs). Moreover, the enrichment factor and geo-accumulation index demonstrated that there was no or slight contamination to be found for Cr, Mn, Ni, Cu, Zn, and Pb and moderate pollution for Cd. The contamination factor (C_fⁱ), integrated contamination degree (CF), modified degree of contamination (_mC_d), and modified pollution index (MPI) revealed individual metal contamination in localized areas. In these river sediments, the potential ecological risk (RI) was low to moderate, except Cd posted a considerable ecological risk because of its high enrichment. Furthermore, the Shawang River and Linhong River were seriously polluted with HMs among seven rivers. These results provided a new direction for controlling HM pollution in Haizhou Bay which suggested substantial measures should be implemented to alleviate the potential risk of HMs, to these rivers sediments.

Effect of river-lake connectivity on heavy metal diffusion and source identification of heavy metals in the middle and lower reaches of the Yangtze River

Metal pollution poses a significant threat to ecological security and human health. Current research on the causes, sources and distribution of metal pollution in the Yangtze River plain is lacking. This study investigated the accumulation, risk, distribution, and sources of heavy metals in 62 lakes along the Yangtze River, and analyzed the relationship between river-lake connectivity, economic structure, population and metal diffusion. The mean concentrations of Cr, Cu, Hg, Zn, Cd, Pb and As in the surface sediments of these lakes were 90.8, 60.1, 0.06, 102, 0.89, 42.7, and 6.01 mg/kg, respectively. Most (99%) of the lake sediments were contaminated with Cd, and the lakes in the middle reach and southern bank of the Yangtze River had a higher ecological risk. Cr originated from the natural environment, whereas Zn, Cu, Pb, Cd and As were affected by human activities. The lakes disconnected from the Yangtze River had higher concentrations of Cu, Zn, Pb and As, while the lakes connected to the river had higher concentrations of Cd and Cr. This comprehensive analysis determined the pollution characteristics of heavy metals, illustrated the causes of non-point pollution in the Yangtze River plain, and showed that soil-water erosion is important in metal diffusion.

Source apportionment of heavy metals in sediments of the urban rivers flowing into Haizhou Bay, Eastern China: using multivariate statistical analyses and Pb-Sr isotope fingerprints

Urban river runoff carrying various anthropogenic sources of heavy metals (HMs) is the most important input pathways for HM pollutions in the coastal region, apportioning sources of environmental pollutants is key to controlling coastal HM pollution. In the study, surface sediments were collected from seven urban rivers flowing through Lianyungang City and discharging into Haizhou Bay, Eastern China. The concentrations of HMs of the river sediments were, in mg/kg (mean value ± standard deviation): Mn (550 ± 227) > Zn (67 ± 61) > Cr (33 ± 12) > Ni (21 ± 8.5) > Cu (16 ± 7.6) > Pb (15 ± 5.6) > Cd (0.11 ± 0.06), which were slightly to moderately polluted. As important outlets for municipal and industrial sewages, the Shawang River and Linhong River were the most polluted. Based on the multivariate statistical analysis, HMs were attributed to anthropogenic source (industrial, domestic, and agricultural discharges) and natural source (soil parent materials and atmospheric deposition). Based on isotope source apportionment, Pb was mainly from natural source, exhausts of leaded gasoline vehicles, and coal combustion, with the mean contributions of 39.3%, 23.7%, and 37.0%, respectively, and Sr originated from natural source and anthropogenic source, with mean contributions of 31.8% and 68.2%, respectively. Pb-Sr isotopes illustrated that anthropogenic inputs were the dominant source for HMs in urban river sediments flowing into Haizhou Bay, and the isotope tracing results make up the discriminating deficiency of the multivariate statistical analysis.

Ecological Risk Assessment and Contamination History of Heavy Metals in the Sediments of Chagan Lake, Northeast China

The study deals with the spatio-temporal distribution of heavy metals in the sediments of Chagan lake, Northeast China. The pollution history of heavy metals is studied simultaneously through the 210Pb dating method by analyzing the characteristic of As, Hg, Cd, Cr, Ni, Cu, Pb, and Zn concentration-depth profiles. The potential ecological risk index (RI) and geo-accumulation index (Igeo) were used to evaluate the contamination degree. Principal component analysis (PCA), based on the logarithmic transformation and isometric log-ratio (ilr) transformed data, was applied with the aim of identifying the sources of heavy metals. The element concentrations show that the heavy metals are enriched in the surface sediment and sediment core with a varying degree, which is higher in the surficial residue. The results of Igeo indicate that the Cd and Hg in the surface sediment have reached a slightly contaminated level while other elements, uncontaminated. The results of RI show that the study area can be classified as an area with moderate ecological risk in which Cd and Hg mostly contribute to the overall risk. For the sediment core, the 210Pb dating results accurately reflect the sedimentary history over 153 years. From two evaluation indices (RI and Igeo) calculated by element concentration, there is no contamination, and the potential ecological risk is low during this period. The comparative study between raw and ilr transformed data shows that the closure effect of the raw data can be eliminated by ilr transformation. After that, the components obtained by robust principal component analysis (RPCA) are more representative than those obtained by PCA, both based on ilr transformed dataset, after eliminating the influence of outliers. Based on ilr transformed data with RPCA, three primary sources could be inferred: Cr, Ni, As, Zn, and Cu are mainly derived from natural sources; the main source of Cd and Hg are associated with agricultural activities and energy development; as for Pb, it originated from traffic and coal-burning activities, which is consistent with the fact that the development of tourism, fishery, and agriculture industries has led to the continuous increasing levels of anthropogenic Pb in Chagan Lake. The summarized results and conclusions will undoubtedly enhance the governmental awareness of heavy metal pollution and facilitate appropriate pollution control measures in Chagan Lake.

Exploring the dynamics of Cu transported from the Yangtze River to the East China Sea

We used a section-segment method to determine the copper (Cu) fluxes from the Yangtze River to the East China Sea during 2012-2016 in this study, including the maximum, minimum and mean annual fluxes of dissolved and suspended Cu. The Cu fluxes exhibited a pronounced inter-annual variability. June was characterized with the highest monthly dissolved and suspended Cu fluxes, while the lowest monthly Cu fluxes was in February. The monthly Cu concentration and Cu fluxes both increased from January to June and decreased from July to December. The monthly Cu fluxes showed a positive correlation with the water flux and monthly mean Cu concentration; however, it had a negative correlation with the ratio of tidal flux to river runoff flux. Both natural (53%) and anthropogenic inputs (32.8%) were the main sources of Cu. The discharges of industrial and domestic sewage wastewater were the main anthropogenic factors affecting the entry of Cu.