The temporal response of dissolved heavy metals to landscape indices in the Le'an river, China.

Heavy metals in watersheds are a serious concern due to their toxicity, abundance, and persistence in the environment, especially in mining areas. Source analyses and exploration of other related factors are one of the most important methods to help with effective prevention and control of heavy metal pollution in watersheds. In this study, the concentrations of Cr, Co, Ni, Cu, Zn, As, Cd, Sb, Ba and Pb were measured in the Le'an River, and PCA (principal component analysis) and APCS-MLR (absolute principal component scores - multivariate linear regression) methods were used to identify the sources of the dissolved heavy metals. Additionally, a CA (correlation analysis) method was used to explore the correlations between landscape indices and concentrations of heavy metals. Results show that the main sources for these dissolved heavy metals are mining activities, fertilizers, pesticides, and natural sources. Specific results of PCA and APCS-MLR suggest that Cu, Zn, Cd, Ba are mainly related to mining activities, Cr and Pb are due to fertilizers and pesticides, and Co and Ni are mainly due to natural sources. Correlations between landscapes and heavy metals revealed significant temporal variations, with the strongest responses of dissolved heavy metals to landscape indices appearing in December and March. The propensity of positive or negative responses of the heavy metals to landscape indices are determined by the sources, and their temporal variations may be related to the seasonal changes of rainfall and plant metabolism.

Heavy metals in the volcanic and peri-urban terrain watershed of the River Yautepec, Mexico.

Thirty-four water samples were collected all along the course of River Yautepec, Morelos State, Central Mexico, in three different zones based on the physical and anthropogenic setting. In situ measurements of physical characteristics (temperature, pH, conductivity, and turbidity) were also performed at each sampling station. Likewise, total/dissolved metal concentrations (Fe, Mn, Cr, Cu, Ni, Pb, Zn, Cd, As, and Pb) were determined using an atomic absorption spectrophotometer. Located in a peri-urban and volcanic zone of Central Mexico, the river system presented impacts of both natural and anthropogenic activities. Results revealed differences in pH values (6.7-8.23) in all the three zones probably due to the influences of volcanic ash and local geological formations, whereas conductivity levels (635-1098 µs/cm) were high indicating the effect of agricultural and industrial activities. The relative order of the concentrations of metals in both the total and dissolved fractions was observed to be in the following order: zone I, Fe > Zn > Mn > Cu > Pb > Ni > Cr > As > Cd > Hg; zone II, Fe > Zn > Pb > Ni > Mn > Cu > Cr > Cd > As > Hg; zone III, Fe > Pb > Zn > Mn > Ni > Cu > As > Cd > Cr > Hg. Calculated heavy metal evaluation index (HEI) values indicated less contamination. However, concentrations of Fe and Pb were observed to be higher than the permissible limits set forth by the Mexican government for human consumption. Henceforth, the prerequisite for maintaining and improving the health of a river system depends on continuous long-term monitoring of the dynamic ecosystem for sustainable management.

An assessment of metal-humus complexes in river waters of the Upper Amur basin, Russia.

The dissolved metal concentrations have been assessed for Co, Cr, Cu, Fe, Mn, Ni, V, Zn, Ca, Mg, and Cd, and their complex compounds with humic substances (Me-HS complexes) in river waters of the Upper Amur basin using the inductively coupled plasma-mass spectrometry technique. The study shows an increase in the amount of Me-HS complexes from the southwestern steppe and forest-steppe to the northeastern mountainous taiga areas. In alkali waters of the steppe and forest-steppe areas with low concentrations of HS, the amount of Zn-HS complexes increases considerably. The observed general regularity in the distribution of metals is as follows: Fe > Cu ≥ Zn > Cr > V > Ni > Ð¡o ≥ Mn > Ca > Mg > Cd. In acidic and neutral waters of the taiga rivers containing high concentrations of HS, 50% of metals are complexed with HS. Metals are arranged in the following order: Fe > Cu > Ni > Cr > V > Zn > Ð¡o > Mn > Ca > Mg > Cd. Quantitative characteristics and a correlation matrix show that Me-HS complexes are dominant among toxic metals (Ni, Cu, Zn, Cr, Fe, and V) and account for 40-55% of total dissolved forms. This allows us to evaluate the important role of Me-HS complexes in satisfactory ecological situation in rivers of the Upper Amur basin. However, toxicity may increase in separate watercourses (Chita and Argun rivers) due to high concentrations of dissolved Zn, Cu, and Cr, which indicate local and transboundary sources of pollution.

Ecological risk assessment of dissolved heavy metals in the Yangtze River Estuary and Zhejiang coastal waters, China.

The study applied a tiered ecological risk assessment method to evaluate the long-term status and trend of the ecological risks of dissolved heavy metals from 2011 to 2019 in the Yangtze River Estuary and Zhejiang coastal waters, China. The results for spring, summer, and autumn of 2019 indicated that Pb, Cd, and Zn posed no adverse ecological risk, Cu posed a potential ecological risk, and As posed an ecological risk. The annual results from 2011 to 2019 suggested that Pb, Cd, and Zn posed no adverse ecological risks, and As and Cu posed an ecological risk. The trend analysis in the nine years showed that the ecological risk of Cu is gradually decreasing, while that of As is still a concern. The overall trend is attributed to the environmental protection policies that reduced these contaminants' terrestrial sources and atmospheric sources.

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

Dissolved heavy metals (DHMs) contamination has raised global concern for ecological and human health development. Weathering of sulfide-bearing ore metals can produce acidic, sulfate-rich solutions in the presence of water and oxygen (O2), and DHMs are released to deprave the river water quality. Sulfur and oxygen isotope signatures (δ34SSO4 and δ18OSO4) could identify this pyrite-derived sulfate; however, it is yet not well known whether the δ34SSO4 and δ18OSO4 values could limit the DHMs sources and illustrate anthropogenic impacts on DHMs along the river corridor. We tried to solve this problem through field works in the Luohe River and Yihe River, two tributaries of the Yellow River, China, where metal sulfide mine activities mostly occurred upstream, but agricultural and domestic behaviors concentrated in the lower plain reaches. In the Luohe River upper areas, δ34SSO4 values had negative correlations with concentrations of cadmium (Cd) (p < 0.01), nickel (Ni) (p < 0.05), molybdenum (Mo) (p < 0.01), uranium (U) (p < 0.01), and SO42- (p < 0.01). However, as the δ34SSO4 values increased downstream in the Luohe River, concentrations of copper (Cu) (p < 0.05), mercury (Hg) (p < 0.05), Ni (p < 0.05), and SO42- (p < 0.01) simultaneously elevated. The Bayesian Isotope Mixing Model (BIMM) results via δ34SSO4 values demonstrated 64.3%-65.3% of SO42- from acid mine drainage (AMD) in the Luohe River's upper reaches and 63.5%-67.7% in the Yihe River's upper reaches, and about 33% from sewage and industrial effluents in the Luohe River's lower reaches and 27% in Yihe River's lower reaches. Our results confirmed the different anthropogenic impacts on the DHMs concentrations in Luohe River and Yihe River and provided a robust method for DHMs sources appointment and pollution management in river systems.

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

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

Enhancing the CE-QUAL-W2 to model dissolved lead transport and transformation in dam reservoirs: a case study of Shahid Rajaei Dam reservoir, north part of Iran.

Investigation of heavy metal transport in water bodies such as dam reservoirs due to the environmental hazards and the transformation complexities of heavy metals from dissolved phase to particulate phase and vice versa is of particular importance. The transport process of the dissolved heavy metals such as lead (Pb) in storage dam reservoirs is significantly influenced by the water flow, and ambient parameters such as temperature, total dissolved solids (TDS), dissolved oxygen (DO), and suspended solids (SS). Due to the lack of a suitable model to simulate the heavy metal transport in dam reservoirs, in this study, the hydrodynamics and water quality model, CE-QUAL-W2, was enhanced by developing 2D laterally averaged model for simulating the dissolved phase of Pb contaminant and applied to the Shahid Rajaei Dam reservoir, Sari, Iran. The developed model can describe the advection-dispersion and transformation processes and simulate the temporal and spatial distribution of dissolved phase of Pb concentrations. A new approach was introduced to calculate different reaction coefficients used in the transformation term of the advection-diffusion equation. Comparison of the simulation results of temperature, TDS, DO, SS, and dissolved phase of Pb with the measured values from the Shahid Rajaei Dam reservoir shows a mean percentage error (MPE) of 6.8, 4.7, 11.7, 19.7, and 7.27 respectively. The results of the present study showed that the temperature was the most effective parameter on the transformation of Pb in the Shahid Rajaei Dam reservoir due to large changes of temperature in depth as about 15 °C along with small changes in other ambient parameters in several months of the year. This phenomenon can be expected in many reservoirs that are stratified in a period of the year. However, the effect of other ambient parameters such as TDS, DO, and SS should not be neglected.

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

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

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

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

[Spatial Distribution and Pollution Assessment of Dissolved Heavy Metals in Chaohu Lake Basin During the Wet Season].

The spatial distribution characteristics of the mass concentration of V, Cr, Mn, Ni, Cu, Zn, Pb, Cd, Fe, and Sb in the Chaohu Lake basin and ten surrounding rivers during the wet season were explored. The results showed that the average mass concentration of heavy metals in the western and northwestern Chaohu Lake surrounding rivers was higher than that in the central and eastern regions. The correlation analysis showed a significant positive correlation between the concentrations of Cu, Ni, Zn, Pb, and Cd, which indicated a similarity of spatial distribution among the five elements. The single-factor pollution index evaluation results classified Cr in the ten surrounding rivers as Grade I based on the Environmental Quality Standards for Surface Water. Pb was classified as Grade Ⅰ-Ⅱ; Cu and Zn as Grade Ⅰ-Ⅴ; Fe, Sb, and V were far below the standard limit; Ni slightly exceeded the standard at some sampling points of the Nanfei River; Mn slightly exceeded the standard at some points of the Shiwuli and Pai River; Cd exceeded the standard at some points of the Nanfei River. Except Mn at one point of the Tangxi River, V, Cr, Ni, Cu, Zn, Pb, and Fe were all<1, which indicated clean and pollution-free level. The integrated pollution index of the rivers surrounding the lake in the northwestern part was the highest compared to the southwestern, central, and eastern parts.

Geochemical characteristics of dissolved heavy metals in Zhujiang River, Southwest China: spatial-temporal distribution, source, export flux estimation, and a water quality assessment.

To investigate the sources and spatial-temporal distribution of dissolved heavy metals in river water, and to evaluate the water quality, a total of 162 water samples were collected from 81 key sampling points in high and low flow seasons separately in the Zhujiang River, Southwest China. Ten dissolved heavy metals (V, Cr, Mn, Co, Ni, Cu, Mo, Cd, Ba, and Pb) in the Zhujiang River water exhibit little variation at temporal scale, but vary with a significant spatial heterogeneity. Furthermore, different metals present different variation trends along the main channel of the Zhujiang River. Our results suggest that Ba (14.72 µg L-1 in low flow season and 12.50 µg L-1 in high flow season) and Cr (6.85 µg L-1 in low flow season and 7.52 µg L-1 in high flow season) are consistently the most abundant metals in the two sampling periods. According to the water quality index (WQI values ranged from 1.3 to 43.9) and health risk assessment, metals investigated in Zhujiang River are below the hazard level (all hazard index (HI) < 1). Application of statistical approaches, including correlation matrix and principal component analysis (PCA), identify three principal components that account for 61.74% of the total variance, the results conclude that the anthropogenic heavy metals (V, Cr, Ni, and Cu) are greatly impacted by the dilution effect, and the heavy metals in Zhujiang River are mainly presented a natural sources signature from the perspective of entire basin. Moreover, our results reveal that the estimated export budget of several heavy metals including V (735.6 t year-1), Cr (1,561.1 t year-1), Ni (498.2 t year-1), and Mo (118.9 t year-1) to the ocean are higher than the world average.

Distribution, Sources, and Water Quality Assessment of Dissolved Heavy Metals in the Jiulongjiang River Water, Southeast China.

In this study, the concentration of eight dissolved heavy metals (Ti, Cr, Mn, Fe, Ni, Mo, Sb, and Ba) in 42 water samples from the Jiulongjiang River, southeast China, were determined by inductively coupled plasma mass spectrometry (ICP-MS). Multivariate statistical methods, including correlation analysis (CA) and factor and principal component analysis (FA/PCA), were analyzed to identify the sources of the elements. Water quality index (WQI) and health risk assessment, including hazard quotient (HQ) and hazard index (HI), were used to evaluate water quality and the impacts on human health. Our results were compared with the drinking water guidelines reported by China, the World Health Organization (WHO), and the United States Environmental Protection Agency (US EPA), revealing that Ti, Mn, and Sb were not within approved limits at some sites and might be the main pollutants in the drainage basin. Based on the spatial distributions, Ti, Mn, Fe, Ni, and Mo showed good similarity, indicating that they might come from similar sources along the river. The CA results also showed that Ti, Mn, Fe, Ni, and Mo had a high correlation coefficient. The FA/PCA results identified three principal components (PC) that accounted for 79.46% of the total variance. PC 1 suggested that a mixed lithogenic and urban land source contributed to Ti, Mn, Fe, Ni, and Mo; PC 2 showed that Cr, Ni, and Mo were influenced by the discharge of industrial effluents; Sb had a strong loading on PC 3, which was controlled by mining activities. The results of the WQI indicated that the water in the Jiulongjiang River was basically categorized as excellent water, but the water quality levels in site W5 and N4 were poorer due to urban land use. Hazard quotient and HI values showed that Sb was a potential threat to human health, indicating that preventive actions should be considered in regard to mining activities in the upper reaches of Beixi stream.

Critical review of heavy metal pollution of traffic area runoff: Occurrence, influencing factors, and partitioning.

A dataset of 294 monitored sites from six continents (Africa, Asia, Australia, Europe, North and South America) was compiled and evaluated to characterize the occurrence and fate of heavy metals in eight traffic area categories (parking lots, bridges, and three types each of both roads and highways). In addition, site-specific (fixed and climatic) and method-specific (related to sample collection, preparation, and analysis) factors that influence the results of the studies are summarized. These factors should be considered in site descriptions, conducting monitoring programs, and implementing a database for further research. Historical trends for Pb show a sharp decrease during recent decades, and the median total Pb concentrations of the 21st century for North America and Europe are approximately 15 µg/L. No historical trend is detected for Zn. Zn concentrations are very variable in traffic area runoff compared with other heavy metals because of its presence in galvanized structures and crumbs of car tire rubber. Heavy metal runoff concentrations of parking lots differ widely according to their use (e.g., employee, supermarket, rest areas for trucks). Bridge deck runoff can contain high Zn concentrations from safety fences and galvanizing elements. Roads with more than 5000 vehicles per day are often more polluted than highways because of other site-specific factors such as traffic signals. Four relevant heavy metals (Zn, Cu, Ni, and Cd) can occur in the dissolved phase. Knowledge of metal partitioning is important to optimize stormwater treatment strategies and prevent toxic effects to organisms in receiving waters.

Dissolved heavy metal concentrations of the Kralkizi, Dicle and Batman dam reservoirs in the Tigris River basin, Turkey.

Water samples were collected at monthly intervals during 1 year of monitoring from Kralkizi, Dicle and Batman dam reservoirs in the Tigris River basin to assess the concentrations of dissolved heavy metals and to determine their spatial and seasonal variations. The results indicated that dissolved heavy metal concentrations in the reservoirs were very low, reflecting the natural background levels. The lowest total metal concentrations in the three dam reservoirs were detected at sampling sites close to the dam wall. However, the highest total concentrations were observed at sites, which are located at the entrance of the streams to the reservoirs. Fe, Cr and Ni were the most abundant elements in the reservoirs, whereas Cd and As were the less abundant. The mean concentrations of dissolved metals in the dam reservoirs never exceeded the maximum permitted concentrations established by EC (European Community), WHO and USEPA drinking water quality guidelines. All heavy metals showed significant seasonal variations. As, Cd, Cr, Cu, Fe, Ni and Pb displayed higher values in the dry season, while higher values for Zn in the wet season. Cluster analysis grouped all ten sampling sites into three clusters. Clusters 1 and 2, and cluster 3 corresponded to relatively low polluted and moderate polluted regions, respectively. PCA/FA demonstrated the dissolved metals in the dam reservoirs controlled by natural sources.