Fractionation of heavy metals in different particle-size sediments and its relationship with heavy metal pollution

Potentially Toxic Elements and Pb Isotopes in Mine-Draining Meža River Catchment (NE Slovenia)

In the present study it was observed that Pb, Zn, Cd and As are still present at elevated concentrations in the environment of the upper Meža Valley. In particular, the concentrations of Pb indicate possible new sources have emerged. The main objective of this study was to determine the Pb isotope composition in both the water and the sediments (fractions < 0.150 and <0.063 mm) from the Meža River and its tributaries for the first time and then use them as identifiers of Pb pollution sources. In addition, by calculating the PEC-Q values, the potential hazard of the present concentrations of Pb, Zn, Cd and As to the river environment was evaluated. The results showed elevated Pb and Zn concentrations in the water and sediments at the majority of sampling sites. In general, higher concentrations of Pb, Cd and As were determined in the <0.063 mm fraction, while Zn was higher in the <0.150 mm fraction. The isotope composition of Pb in both fractions differed slightly, indicating an additional Pb source.

Relationship between magnetic properties and heavy metal contamination of street dust samples from Shanghai, China

In this study, for exploring the relationship between selected magnetic properties and heavy metal contamination of street dust in Shanghai, China, 160 samples from five different functional areas (industrial, high traffic density, commercial, residential and "clean" area) were collected and investigated by magnetic and geochemical analyses. It is found that the street dust exhibits a high concentration of ferrimagnetic minerals, which are predominantly coarse-grained. Meantime, the magnetic properties of the street dust samples exhibit significant differences between the five functional areas, namely, the values of χ_lf, SIRM, χ_ARM, and S_- 300 mT in the five functional areas all decrease in the following order: industrial > commercial > high traffic density > residential > clean. Calculation of enrichment factors (EF) and the Tomlinson pollution load index (PLI) indicates that the street dust samples are highly polluted in terms of their degree of heavy metal contamination. The values of χ_lf, SIRM, and χ_ARM are significantly correlated with Pb, Cu, Zn, Ni, Mn, Cr, Ba, and Fe concentrations as well as PLI. In accordance with similar findings in other urban areas, these results indicate that magnetic parameters, such as χ_lf, SIRM, χ_ARM, can be used as an efficient proxy for heavy metal pollution and anthropogenic activities in Shanghai. In addition, the results demonstrate that it is possible to distinguish different heavy metal pollution sources using a combination of magnetic measurements and geochemical analysis.

Assessment of labile Zn in reservoir riparian soils using DGT, DIFS, and sequential extraction

The middle route of the South-to-North Water Diversion project alleviates drought in northern China, especially reducing water shortage pressure in Beijing. However, after submersion, the potential release risk of metals in newly submerged soils into the water in the receiving reservoir remains unclear. Here, we assess the labile Zn in the riparian soils of Miyun Reservoir (MYR) using the diffusive gradients in thin films (DGT), DGT-induced fluxes in soils (DIFS) model, and Community Bureau of Reference (BCR) sequential extraction. The results showed that the average Zn concentrations at three sampling sites (S2, S3, and S5) exceeded soil background value (74.8 mg/kg), indicative of Zn accumulation in the MYR. The concentrations of DGT-labile Zn varied within 39.7-62.4 μg/L (average: 56.7 μg/L), with the greatest value observed at 145 m at sampling site S3, attributed to anthropogenic activities in recreational areas. The DGT-labile Zn showed no correlation with classes of land, elevations, or soil properties. Sequential extraction results demonstrated that Zn predominantly existed in the residual fraction, but still showed a strong capability for resupply from the solid phase (R >1). The DIFS model simulation results showed that Zn underwent irreversible diffusion of intra-particle metals from the solid phase to the soil solution. Therefore, the potential release risk of labile Zn in riparian soils in MYR cannot be ignored, especially for areas experiencing human disturbance.

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.

The Research Progress of Heavy Metals in PM2.5

PM2.5 is one of the most important components in air pollution. It is also the focus of the most closely watched at home and abroad. Based on its small size, complex components, and strongenvironmental activity, it can be used as a carrier for chemicals, heavy metals, bacteria, toxins and carcinogens into the body. Then, as a result, it will affect Human Body Health. Heavy metals are important components of PM2.5, and the long-term accumulation of heavy metals in PM2.5 poses a great threat on human health and the environment. This paper reviewed the sources, distribution methods,chemical form, detection methods, disposal way, research progress of heavy metals in PM2.5. As a result, it provided a reference for in-depth study on the future.

Trace metals biogeochemistry of Kumaun Himalayan Lakes, Uttarakhand, India

The increasing urbanization, along with tourism, has posed a major threat to the Kumaun Himalayan Lakes, Uttarakhand, India. The total metal concentration in the water, interstitial water, and sediments along with the metal fractionation studies were carried out to understand the remobilization of the trace metals from the sediments of the lakes. The high concentration of the metals in the water column of the lakes generally decreases with depth and the metals release from the sediment is mainly due to the prevalence of anoxic condition at the sediment-water interface and sediment column. The sediment shows that metals Fe and Cr are derived from detrital source, whereas Co, Ni, and Zn are derived mainly from the organic matter dissolution. The sparse correlation of the trace metals with Ti shows most of the metals have chiefly re-precipitated from the water column. The metals speciation studies also supports that metals experience a high rate of anoxic dissolution and their precipitation onto the sediments are determined by the sediment composition and organic matter content. The high concentration of manganese in the interstitial water in the lakes indicates dissolution of organic matter. The released manganese is adsorbed/precipitated as carbonate phase (Nainital Lake) and oxide pahse (in other lakes). The study shows that the trace metals are regenerated from the sediments due to oxyhydroxide dissolution and organic matter decomposition.

Distribution of mercury and organic matter in particle-size classes in sediments contaminated by a waste water treatment plant: Vidy Bay, Lake Geneva, Switzerland

In Lake Geneva, Switzerland, the most Hg-contaminated sediments have been found in the Vidy Bay where high Hg contents largely exceeds the background levels of Lake Geneva sediments. This contamination has been attributed to the discharge of a waste water treatment plant (WWTP). Total Hg (THg) and monomethylmercury (MMHg) were determined in bulk sediment and in three different grain size fractions (i: clay and silt, ii: fine-coarse sand, iii: and very coarse sand and gravel) collected close to the outlet pipe of a WWTP in order to verify whether the standardized procedures of sediment treatment is adequate for this setting and, by extension, for similar contaminated sites. THg was homogeneously distributed in the different grain size fractions and was correlated to organic matter content (R(2) = 0.6). MMHg was homogeneously distributed in the two finer grain fractions (Φ < 0.063 mm; 0.063 mm < Φ <1 mm). The results of this study suggested that the analysis of the bulk sediment seems to be more appropriate for the assessment of the content and spatial distribution of Hg in freshwater sediments contaminated by WWTPs.

Distribution and enrichment of silver and cadmium in coastal sediments from Bahía Todos Santos, Baja California, México

Silver, cadmium and iron were studied in sediment from Bahia Todos Santos, Baja California, México during 2004. Results showed that the spatial distributions of these metals were very similar to that of organic carbon and fine grain size, with values increasing from the inner to the outer parts of the bay. High concentrations and enrichments of silver (0.051-0.071 μg g⁻¹ dry weight) and cadmium (1.9 μg g⁻¹ dry weight) in Bahía Todos Santos were associated to harbor dredging activities and to coastal upwelling, respectively. However, the distribution of silver and cadmium in most of the study area is controlled by grain size and organic carbon content.