A modified introduction device and a preconcentration method were developed to enhance the sensitivity of the Hg isotopic analysis method.

No abstract

Variations in the composition of stable isotopes of mercury contained in tissues (root, stem, leaf, and hypocotyl or flower) of three typical mangrove plants (Kandelia candel, Aegiceras corniculata, and Bruguiera gymnorhiza), collected from the mangrove wetland of Jiulong estuary, SE China, were used to investigate the sources and transformation of mercury in the mangrove plants. Tissue samples from the plants were digested and mercury in the solution was pre-concentrated with purge-trap method and then analyzed by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed that the mass dependent fractionation (MDF) of mercury ranged from -2.67 to -0.87 ‰ for δ Hg while the mass independent fractionation (MIF) of mercury isotopes ranged from -0.16 to 0.09 and -0.19 to 0.05 ‰ for ΔHg and ΔHg, respectively, relative to the standard NIST SRM 3133. The ratio of ΔHg/ΔHg was 0.991, indicating that the mercury had been photo-reduced before being accumulated in mangrove plants. Analyses of the data from MIF studies revealed that the major portion of the mercury measured in leaves (∼90 %) originated from the atmosphere while the source of over half of the mercury present in roots was the surficial sediment. This study, the first of its kind investigating the variations in isotopic composition of mercury in the tissues of mangrove plants, could be helpful to identify the source of mercury contamination in mangroves and understand the biogeochemical cycle of mercury in the estuarine mangrove wetlands.

A high concentration of dissolved gaseous mercury (DGM) was detected in post-desulfurized waste seawater, which was discharged from a coal-fired power plant equipped with a seawater desulfurization system and which was located in a coastal area. A large amount of DGM was converted from other forms of mercury during transformation processes, such as photo-reduction. The present study targeted the photo-reduction of mercury and the effects of various environmental parameters on DGM production in the post-desulfurized seawater discharged. The results suggested that the photoreduction of mercury was significantly induced under UV radiation, especially with UVB. The particulate mercury on suspended solids was easily photo-reduced and considered as an important source of DGM. It was confirmed that the suspended solids in postdesulfurized seawater could enhance the reduction process of mercury under UV radiation. The pseudo-firstorder rate constants of DGM production, which were determined through the concentration gradient and trial methods, were 1.39×10 −3 min −1 and 1.45×10 −3 min −1 , respectively. The values showed no significant difference and were both much higher than the reported results, indicating that the photo-reduction of mercury in post-desulfurized seawater deserved more attention. In addition, the initial mercury level was observed when mixing the post-desulfurized seawater with fresh seawater, and this suggested that a significant amount of initial mercury would be produced when the post-desulfurized seawater was discharged into the adjacent sea area and thus becomes another considerable source of DGM.