Status, sources, and human health risk assessment of DDT pesticide residues in river sediments in a highly developed agricultural region in the upper Yangtze River in China.

The concentrations of DDT and its metabolites in 19 sediment samples from a highly developed agricultural region in the upper reaches of the Yangtze River were measured. Non-carcinogenic hazard quotient for different age groups was evaluated using reference doses provided by the USEPA, and the excess lifetime cancer risk due to eating fish was assessed based on the local eating habits. The results showed that this region had a high level of residual DDT (12.84 ± 8.97 ng/g), which mainly came from the historically used technical DDT in agriculture. The non-carcinogenic risk was just acceptable in the region, but 11 of the 19 sites showed an unacceptable carcinogenic risk. Although DDT has been banned for decades, there were still notable health risks, especially for children. Special attention should be given to the potential health risks in historically developed agricultural regions.

Potentially Toxic Element Contamination in Soils Affected by the Antimony Mine Spill in Northwest China.

This study provides a comprehensive assessment of the potential ecological and health risks in the area of the antimony mine spill in Longnan, Northwest China, and identifies the sources of potentially toxic elements (PTEs) in the soil as a result of the spill. The geo-accumulation index and enrichment factor show that the study area is highly contaminated with arsenic (As), mercury (Hg) and antimony (Sb). The ecological risk index in the tailings spill area ranged from 320.43 to 5820.46 (mean: 1489.82), indicating a very-high potential ecological risk, with mean values of 104.86, 1118.87 and 248.84 for As, Hg and Sb, respectively. The multivariate statistical analysis suggested that Sb and Hg come from tailings leakage, while copper (Cu), nickel (Ni) and zinc (Zn) may be imported from natural sources, and As and lead (Pb) originate from agricultural activities. In addition As and Sb pose a high health risk. With the exception of the non-carcinogenic risk in adults, all other risks are significantly exceeded in other populations, with children being the highest-risk group. These findings provide important quantitative information for the assessment and management of PTE contamination in other tailings spill areas.

Element partitioning, emissions, and relative risk during disposal processes of diverse litters, fruit tree branches, and crop straws: dry distillation, incomplete combustion, and sufficient combustion.

This study reports the release behaviors, enrichment characteristics, contamination level, and health risk of twenty-one elements in biomass, when dry distillation, incomplete combustion, and sufficient combustion. Results indicate that the element concentration in different kinds of biomass varies greatly. Even for the same kind of biomass, concentration in three products of dry distillation, incomplete combustion, and sufficient combustion is also different: fifteen elements (K, Ca, Mg, Al, Fe, Mn, B, Cu, Zn, Mo, Cd, Cr, Pb, Sb, Sn) have no significant difference in concentration but other six elements (As, Co, Ni, V, Na, P) are the opposite. Multivariate statistical approaches were used to assess five significant factors which affect element concentration, suggesting the contributes from biomass type, moisture content, soil, biomass age or organ, and disposal methods. Disposal methods and biomass type result in significant differences in element enrichment factor. More elements will release during sufficient combustion rather than dry distillation. The increasing of supplied oxygen during disposal process may increase the overall toxicity from elements release. The data of excess lifetime cancer risk (ELCR) suggests that Cr, Ni, Co, Cd, and Pb are the largest contributors to cancer risks during biomass application.