Heavy metals in soils

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.

The dynamic coastal and marine waters are frequently polluted by metals that affect the biota. Metal concentrations in the biota, water and sediments of Ennore estuary were monitored spatially over two years to understand their potential impact and ecological risk. Variations in concentrations of chromium (Cr), copper (Cu), cadmium (Cd), lead (Pb) and nickel (Ni) were observed in water, sediment and marine organisms. The metal concentrations (μg/l) in the water were in the order of Ni (35) > Pb(16.9) > Cu(15.8) > Cr(12.5) > Cd(5.6) and sediment (μg/g) was Cr(390) > Pb(266) > Cu(162) > Ni(125) > Cd(7.6). Elevated metal levels in the ambient water and sediment tend to accumulate in the marine organisms. Average concentrations of Cr, Cu, Cd, Pb and Ni in fish Mugil cephalus measured as 4.6, 2.4, 2.21, 4.9 and 2.6 μg/g, 11.4, 22.1, 3.3, 8.9 and 6 μg/g in Crab Scylla serrata, 13, 20.8, 1.3, 7.9 and 4.8 μg/g in Oyster Crassostrea madrasensis and 18.8, 20.1, 1.0, 12 and 5.6 μg/g in polychaete Eunice spp. Distinct patterns of metal content in crab, oyster and polychaete (Cu > Cr > Pb > Ni > Cd) and in fish (Pb > Cr > Ni > Cu > Cd) are due to differences in their habitat and specific uptake and elimination capacity. Environmental quality indices (EQI) and Potential ecological risk index (PERI) were derived from the metal concentration in sediment. EQI evidenced that the Ennore estuary is highly contaminated by Cd and Pb from anthropogenic sources. PERI implied that the estuary is under considerable ecological risk from metals. Contamination and risk from metals are relatively higher during summer owing to the low influx of water and higher residential period. Metal concentrations are exceeding the guideline values in the ambient water, sediment and biota in Ennore estuary. It is concluded that long-term monitoring of metal distribution, bioaccumulation and risk assessment provides reliable data and valuable information for possible pollution management strategies in Ennore estuary.

Ecological risk from heavy metals in Ennore estuary, South East coast of India

The study area was selected in the Rupsha river basin and the sediment samples were collected to determine trace metal concentrations of As, Pb, Cd, and Cr along with biological effects, and potential ecological and human health hazards for adults and children. The concentrations of trace metals were detected from sixty composite sediment samples using an Atomic Absorption Spectrophotometer (AAS) following some sequential analytical procedures. The mean concentrations of trace metals were organized in the descending order of chromium (Cr) (43.2 mg/kg) > lead (Pb) (29.21 mg/kg) > arsenic (As) (5.18 mg/kg) > cadmium (Cd) (1.8 mg/kg). The current study highlighted that metals were attributed to the riverine sediments from natural sources and other anthropogenic sources, particularly from various industries. Based on the effect-range classifications of threshold effect concentration (TEC) and probable effect concentration (PEC), the trace metal concentrations can impact on the sediment-dwelling organisms occasionally especially for Cr, Cd, and Pb. That is, the concentrations had negative biological consequences on aquatic creatures. The assessed potential ecological risk of Cd offers a significant risk to the aquatic ecosystem, whereas As, Cr, and Cd were in low-risk. Most of the sites of the study area were within the range of moderate risk, indicated by the risk index (RI) values. Furthermore, the applied sediment quality indices, geo-accumulation index (I geo) indicated that sediment was contaminated by Cd whereas contamination factor (CF) denoted that the sediment of the study area was moderately polluted by Pb. However, pollution load index (PLI) revealed that the study area was polluted for cumulative sence especially in winter season. The age-group risk index (HI) was much lower than the threshold limit of 1, showing that the pollution had no non-carcinogenic risk effect. Total carcinogenic risk (TCR) was less than one-tenth of a percentile. For the sake of human and environmental health, proper monitoring of metal element attribution and strict regulation are required to lessen trace metal pollution.

Pollution level of trace metals (As, Pb, Cr and Cd) in the sediment of Rupsha River, Bangladesh: Assessment of ecological and human health risks

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.

Sediments core within the Yangtze River Estuary was collected for metal and grain size analysis. The vertical distribution characteristics of eight metals along the core were investigated based on 137Cs and 210Pb radionuclide dating. The sediment was mainly composed of sand and silt. The metals concentrations were Al, 4.67–6.83; Fe, 2.3–3.94; Mn, 0.046–0.07; Cr, 69.5–103; Cu, 14.3–32.1; Zn, 47.3–96.7; Cd, 0.037–0.212; Pb, 13.7–23; Ni, 18.8–38.9 (mg·kg−1, except Al, Fe, and Mn as %), respectively. Geoaccumulation indexes (Igeo) indicated that Cu, Zn, and Pb were of pollution-free level; Cd, Cr, and Ni were in a slight polluted level. Based on potential ecological risk factors (EI), Cd posed a moderate risk to the local environment. Correlation analysis showed that Fe, Al, and Mn had a close association with Cu, Zn, Pb, and Ni at p < 0.01. Clay was significantly correlated with other metals except Cr and Cd.

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

The remediation of dredged marine sediments contaminated by metals has drawn increasing attention globally. Immobilization was regarded as a promising method for reducing adverse impacts on marine ecosystems. In this study, kaolinite and limestone were used as amendments to immobilize Zn, Pb, and Cu in dredged marine sediments, which were collected from the coastal zone adjacent to Tianjin Port in Bohai Bay. The sequential extraction procedure was applied to identify the mobility of metals and, further, to evaluate the immobilization effect of the amendments. The physical–chemical properties of the sediments, such as the pH, electrical conductivity (EC), salinity, and total organic carbon (TOC), were also measured to better understand their influence on the three metals’ mobility. The results of the sequential extraction procedure indicated that the mobile fractions of the metals were converted into relatively stable fractions because of the two amendments. In addition, the EC, salinity, and TOC decreased moderately, while no obvious variations in the pH of the sediments were observed with the addition of kaolinite and limestone. It was confirmed that both kaolinite and limestone can effectively reduce the mobility and bioavailability of metals, particularly Zn, and limestone generally has a better immobilization effect, compared with kaolinite.

An Ex-Situ Immobilization Experiment with Zn, Pb, and Cu in Dredged Marine Sediments from Bohai Bay, China

The remediation of dredged marine sediments contaminated by heavy metals has drawn increasing attention worldly. The immobilization was regarded as a promising method to reduce adverse impacts on marine ecosystem. In this study, kaolinite and limestone were used as amendments to immobilize heavy metals (e.g. Zn, Pb and Cu) respectively in dredged marine sediments collected from the coastal zone adjacent to Tianjin Port in Bohai Bay. The sequential extraction procedure was applied to identify the mobility of heavy metals and further to evaluate the immobilization effect of amendments. The physical-chemical properties of sediments, such as pH, electrical conductivity (EC), salinity, and total organic carbon (TOC), were also measured to better understand their influence on heavy metals’ mobility. In addition, the compositions of clay minerals were also analyzed to identify the transformation process of minerals in the sediments. The results of sequential extraction procedure indicated that mobile fractions of heavy metals were converted into relatively stable fractions because of the two amendments. In addition, EC, salinity and TOC decreased moderately while no obvious variations of pH in the sediments were observed with the addition of the the kaolinite and the limestone. The percentage of montmorillonite decreased to minimum value while that of chlorite increased gradually during the experimental periods for 40 days probably due to complexation reaction. It was confirmed that both kaolinite and limestone can effectively reduce the mobility and bioavailability of heavy metals, particularly for Zn, generally, limestone has a better immobilization effect compared with kaolinite.

/pdf/the-ex-situ-immobilization-experiment-of-heavy-metals-in-38uwp1l6ka.pdf

The ex-situ immobilization experiment of heavy metals in dredged marine sediments from Bohai Bay, China

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

An Ex-Situ Immobilization Experiment with Zn, Pb, and Cu in Dredged Marine Sediments from Bohai Bay, China

The ex-situ immobilization experiment of heavy metals in dredged marine sediments from Bohai Bay, China