中国主要红树植物中汞含量特征与沉积物汞形态之间的关系

Distribution of Hg in Mangrove Plants and Correlation with Hg Speciation in Sediments

为了解红树植物对汞的富集能力和影响因素,对我国几种主要的红树植物的汞含量、沉积物总汞含量和形态进行了研究.结果表明,几种主要红树植物的总汞含量范围为817.5～3 197.6 ng/g,具有明显的种间差异和器官差异.秋茄汞含量为(1 579.4±1 326.8)ng/g,桐花树为(2 115.1±1 892.3)ng/g,白骨壤为(2 159.3±1 678.7)ng/g,木榄为(2 566.5±821.6)ng/g,海漆为(2 104.3±1 661.8)ng/g,无瓣海桑为(3 197.6±2 782.8)ng/g,老鼠簕为817.5±632.3 ng/g,红海榄为(1 801.8±1 255.4)ng/g.各种红树植物对汞的吸收能力的顺序为:无瓣海桑>木榄>白骨壤>桐花树>海漆>红海榄>秋茄>老鼠簕.我国主要红树林地区表层沉积物的汞形态主要为易挥发态,其次为硫化物及有机结合态或可交换离子态,少量为碳酸盐结合态和铁锰氧化物结合态,残渣态少量甚至没有.只有深圳红树林沉积物中的汞以残渣态为主,其次为硫化物及有机物结合态.无瓣海桑的茎和叶,海漆叶的汞含量与易挥发态汞、可交换态汞具有显著正相关关系,而大多数红树植物的茎汞和叶汞含量与沉积物的总汞含量、不同形态汞之间并没有明显的相关性.红树植物富集的汞来源多样,且这些不同来源的汞在植物体内可能是能够迁移的.

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.