[Distribution of Hg in mangrove plants and correlation with Hg speciation in sediments].

Plant is an important role in biogeochemical cycle of Hg. The aim of this study is to ascertain Hg accumulation in several kinds of mangrove plants, and to discuss relationship among Hg concentrations in mangrove plants and different Hg speciation in sediments. Contents of total mercury (THg) in mangrove plants and sediments were determined. Hg speciation was determined with a modified Tessier's method. Contents of THg of the mangrove plants were in the range of 817.5-3 197.6 ng/g. In detail, Hg concentration was (1 579.4 +/- 1 326.8) ng/g in Kandelia candel, (2 115.1 +/- 1 892.3) ng/g in Aegiceras corniculatum, (2 159.3 +/- 1 678.7) ng/g in Avicennia marina, (2 566.5 +/- 821.6) ng/g in Bruguiera gymnorrhiza, (2 104.3 +/- 1 661.8) ng/g in Excoecaria agallocha, (3 197.6 +/- 2 782.8) ng/g in Sonneratia apetala, (817.5 +/- 632.3) ng/g in Acanthus ilicifolius, (1 801.8 +/- 1 255.4) ng/g in Rhizophora. stylosa, respectively. There are obvious interspecific variation, and organic variation in THg contents of mangrove plants, which is closely related to environment and physiological characteristics of mangrove plants. Enrichment of THg in mangrove plants was inhomogeneous, following the order of Sonneratia apetala > Bruguiera gymnorrhiza > Avicennia marina > Aegiceras corniculatum > Excoecaria agallocha > Rhizophora stylosa > Kandelia candel > Acanthus ilicifolius. Mercury exists mainly in volatile form in most mangrove wetlands, but mainly in the form of residue in sediments from Shenzhen mangrove wetlands. Significantly positive correlations were found among Hg concentrations in leaves and stems of Sonneratia apetala and volatile Hg, exchangeable Hg of sediments. Significantly positive correlations were also found among Hg concentrations in leaves of Excoecaria agallocha and volatile Hg, exchangeable Hg of sediments. But, there is no significant correlation between Hg concentrations of most mangrove plants and different Hg speciation in sediments. It showed that plants assimilate Hg from different sources, such as water, sediment and air, and that Hg assimilated by plants could transfer among different plant organics.

[Distribution of mercury in surficial sediments from main mangrove wetlands of China].

Surficial sediment samples were collected from main mangrove wetlands of China, mercury, pH, salinity, organic matters, grain size, Fe/Hg, Mn/Hg were analyzed. Mercury content ranges from 2.3 to 903.6 ng x g(-1), with a average of (197 +/- 137.6) ng x g(-1). Compared with local background level, serious Hg pollution with high Hg content was found in 7 areas, including Luoyangqiao [(467.5 +/- 68.8) ng x g(-1)], Fugong [(438.2 +/- 147.0) ng x g(-1)], Ewan [(264.3 +/- 89.2) ng x g(-1)], Yaojiayu [(125.4 +/- 27.1) ng x g(-1)], Fujian Province; Sanya [(164.8 +/- 143.9) ng x g(-1)], Dongzhaigang [(314.1 +/- 335.7) ng x g(-1)], Hainan Province, Shenzhen [(179.9 +/- 7.7) ng x g(-1)], Guangdong Province. Hg content was similar with background value in the other 6 areas, including Yunxiao [(63.3 +/- 43.9)ng x g(-1)], Fujian Province; Gaoqiao [(178.6 +/- 127.0) ng x g(-1)], Guangdong Province; Daguansha [(26.1 +/- 18.8) ng x g(-1)], Shankou [(73.8 +/- 21.1) ng x g(-1)], Beilun estuary [(117.8 +/- 51.4) ng x g(-1)], Qinzhou Bay [(147.5 +/- 107.6) ng x g(-1)], Guangxi Autonomous Region. Discrepancy of total Hg concentrations in mangrove wetlands is due to many environmental factors and human activities. Parameters such as grain size, pH, organic matter, Fe/Hg, Mn/Hg are significantly correlated with total Hg respectively. Clay and Fe/Hg are obvious factors influencing total Hg concentration. Impact of environmental factors on mercury can be showed by regression equation.