区域水体中汞的质量平衡与生物地球化学循环

本文是几年来在蓟运河下游对汞的地球化学行为进行综合研究的结果.通过箱式模型的方法,利用质量平衡公式对各流量进行定量计算,结果表明:排入河流的汞,绝大部分很快沉积入水底沉积物中;而存在于河水中的汞,水迁移是最主要的,气迁移很少,生物迁移微乎其微.本文提出了水体中汞的生物地球化学循环模型.汞循环途径主要有两条:无机汞被生物甲基化后的生物小循环和汞在水体与大气之间的地球化学循环.这两种循环主要是由沉积物中的无机泵被生物转变成甲基汞或元素汞之后完成的.因此,存在于沉积物中的无机汞的甲基化能力与转化为元素汞的量,决定了这两种循环过程的汞通量问题.

MASS BALANCE AND BIOGEOCHEMICAL CYCLE OF MERCURY IN A REGIONAL WATER BODY

This paper is written of comprehensive research on biogeochemical behavior of mercury in the lower reaches of Jiyun River for recent years. Quantitative computation for influx is done by means of a box model and mass balance equation: Computed results are shown thus mercury precipitation occurs quickly on bottom sediment of the case after it is discharged into the river. So far as waterborne mercury is concerned, aquatic transport is most important in terms of transport capacity, while air transport is infrequent and biological migration is almost negligible.Two ways of circulation concerning model of biogeochemical cycle of mercury are suggested in this paper, namely, the biological small cycle of mercury in which mercury follows the path biological methylation, and the geochemical cycle which corresponds to circulation of mercury between water body and atmosphere. Both cycles are in relation mainly with inorganic mercury in the sediment which has been converted into methylmer-cury or elemental mercury by microbe. Therefore, capability of methylation and the amount of elemental mercury transformed are related with mercury contained in sediments and become decisive factors to mercury flux of the two cycles.