贵阳市生活垃圾卫生填埋场汞的地气交换特征初步研究

城市生活垃圾填埋场是日常生活中许多含汞物质的最终归宿地,这些含汞物质有可能通过"再挥发"途径进入大气,从而增加大气的汞负荷。为了研究垃圾填埋场汞的释放强度,2003年11月底我们用配备有自动测汞仪的动力学通量箱法,对贵阳市的一个垃圾卫生填埋场进行了汞通量测定。结果发现无论是半年期的垃圾还是覆土,汞的释放均具有明显的日变化规律,即白昼明显大于夜晚。半年垃圾和覆土的平均汞释放强度分别为502.4和55.2ng(Hg)·m-2·h-1,远高于国内外背景区的通量值,说明垃圾填埋场已成为一个潜在的大气汞人为释放源。基质中汞含量的差异是造成通量差异的主要因素,而采取覆土措施则可大大减少汞向大气的排放。天气晴朗时光照强度与汞的释放关系密切,是促进气态汞形成的主要驱动力;阴雨初期,降雨则在一定程度上增加了汞的排放。

A PRELIMINARY STUDY ON THE SOIL-AIR EXCHANGE OF MERCURY FROM A SANITARY LANDFILL IN GUIYANG

Landfilling is the most popular method for urban solid waste disposal in China today. Many mercury-bearing materials used daily have been dumped in landfilling sites without pretreatment, which may lead to a great deal of mercury emission into atmosphere. In late November, 2003, we conducted a field investigation on mercury emission from an urban waste landfilling site in Guiyang, using the dynamic flux chamber (DFC) technique coupled with automatic mercury vapor analyzer-TEKRAN 2537A. Two sites with and without soil coverage for half a year were selected, the former site occupies the most part of the landfill. When the DFC covered the waste directly, emission values reached the maximum, the average flux rate was 502.4ng m~(-2) h~(-1) with the range of -286.2～5609.6ng m~(-2) h~(-1)(N=164), which apparently exceeds the average flux of 55.2 ng m~(-2) h~(-1) (N=105) in the case of DFC over the coverage soil. Both fluxes showed obvious variations, with high values in daytime. The differences in mercury contents of the matrix caused the discrepant emission rates. Solar radiation has good correlations with the mercury flux on fine days, indicating solar energy is an important factor affecting the formation of mercury vapor. The precipitation would also stimulate mercury emission after a long time drought. From this study we have recognized that landfilling sites are also a potential anthropogenic mercury source to atmosphere in China, but some measures such as soil covering will reduce the intensity of mercury emission drastically.