腾冲热泉中砷的甲基化和巯基化过程

为了研究热泉中砷的形态及其分布、转化规律，针对云南腾冲热泉各种砷形态进行了IC-ICP-MS测试和水文地球化学分析.在91处热泉中检出了11种砷形态，包括（亚）砷酸盐、无机硫代砷和甲基（硫代）砷.其中（亚）砷酸盐含量>无机硫代砷含量>甲基砷含量.热泉中无机硫代砷含量及其巯基化程度与硫/砷比正相关.甲基砷含量低是富硫化物热泉中甲基硫代砷形成的主要限制因素，硫/砷摩尔比、总砷、温度、pH、Eh和TDS可影响甲基硫代砷的形成和转化.甲基硫代砷在热泉地表流径上可经历脱巯基、脱甲基然后被沉积物吸附，也可在流径下游重新形成.砷的巯基化和甲基化形态在热泉中广泛分布，甲基硫代砷在热泉环境中具有高迁移性和重现性，应引起相关研究重视. 

Methylation and Thiolation of Arsenic in Tengchong Hot Springs

In order to study the speciation of arsenic (As) in hot springs and their distribution and transformation patterns, IC-ICP-MS quantification and hydrogeochemical analyses were conducted for various arsenic species in Tengchong hot springs in Yunnan Province. In 91 hot spring samples, 11 As species were detected, which include arsenate, arsenite, inorganic thioarsenates, methylated oxyarsenates and methylated thioarsenates. Arsenate and arsenite were predominate species followed by inorganic thioarsenates, unlike inorganic species, methylated As occurred as minor species in Tengchong hot springs. The content of thioarsenates and their degree of thiolation are positively correlated with S/As molar ratios. The lack of methylated oxyarsenates was probably the reason for low methylated thioarsenate levels, besides, the S/As molar ratio, total As, temperature, pH, Eh and TDS can also affect the formation and transformation of methylated thioarsenates. Methylated thioarsenates may undergo a series of transformations and interfacial reactions on the surface drainage of hot springs such as de-thiolation, de-methylation and then adsorption by sediments. Other As species can be converted to methylated thioarsenate in downstream areas with relatively low temperatures, low flow rates and significant microbial activity. The thiolated and methylated species of As are widely distributed in hot springs, and the highly toxic methylated thioarsenates have high mobility and are likely to reappear in hot spring drainage environment, which should attract the attention of relevant studies.