[Geochemical characteristics of nitrogen in core sediments from Sishili Bay, China].

A sequential extraction technique was applied to gain the information about the fractionation of nitrogen in four core sediments from Sishili Bay, China. Based on the binding strength of different nitrogen compounds to the sediment matrix, ranging from easy to more difficult, four forms of labile nitrogen, i. e. nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidant extractable form (SOEF-N), were extracted. The results showed that the content of labile nitrogen averagely accounted for about 26.14% of total nitrogen in the surface (0-10 cm) of core sediments and decreased gradually with depth, which implied that under natural geochemical conditions only a small part of sedimentary nitrogen could participate in recycling in a short time scale. The SOEF-N was the predominant form. The average percentages of the four labile nitrogen forms were 89.7% for SOEF-N, 7.97% for IEF-N, 1.19% for WAEF-N, and 1.14% for SAEF-N, respectively. The contents of nitrogen in different labile forms at different sampling sites are influenced by the combination of environmental factors such as sediment pH, redox potential and particle size.

[Migration and transformation of anthropogenic platinum group elements in environment: a review].

Anthropogenic platinum group elements (PGEs) are widely applied in vehicle exhaust catalytic converters (VECs), industrial catalysts, and pharmaceutics, making the PGEs, especially Pt, Pd, and Rh, become the newly environmental pollutants in some fields. Given the positive correlations between the Pt/Pd and Pt/Rh ratios in various environmental samples and the active components of VECs, the VECs containing PGEs as catalysts are regarded as the primary source of PGEs pollution. Sufficient reports indicated that in the past three decades, there was a significant increase of PGEs concentrations in diverse environmental matrices like airborne particulate matters, aquatic ecosystem components (e.g., river water, rain water, groundwater, seawater, and sediments), soils, road dusts, and organisms. It was generally assumed that anthropogenic PGEs behave in inert manner, and the health risks associated with the environmental exposures to PGEs are minimal. However, the recent studies on PGEs toxicity and environmental bioavailability indicated that once entering environment, anthropogenic PGEs might easily be mobilized and transformed into more toxic forms under the actions of various biogeochemical processes, and thereby, enhanced their bioavailability and posed potential health risks to human beings through food chain. This paper summarized the research results about the sources, distribution, and biogeochemical behaviors of PGEs in various environmental media, and it was considered that to establish the standards of PGEs for human health risks, to develop standard substances of PGEs for environmental measurements, to study the PGEs in the sediments of marginal seas, and to assess the toxicity of PGEs to marine mollusks, the present contamination status of PGEs in foods, and the risks of PGEs to human health would be the hot research topics in the future.