北京市土壤Hg污染的区域生态地球化学评价  

Regional eco-geochemical assessment of mercury in soils in Beijing.

作　　者：成杭新[1] 庄广民[2] 赵传冬[2] 杨柯[2] 聂海峰[2] 刘飞[2] 黄宏库[2] 范辉[2] 阮启和 冯辉 

机构地区：[1]北京大学化学与分子工程学院,北京100871 [2]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000 [3]北京地质勘察技术院,北京102218

出　　处：《地学前缘》2008年第5期126-145,共20页Earth Science Frontiers

基　　金：国家重点基础研究发展计划"973"项目(G1999045707);国土资源大调查项目(200420130002;200414200011)

摘　　要：城市土壤Hg异常/污染是中国普遍存在的重大生态环境问题。文章对北京市近1000km^2范围内的地表土壤、壤中气、大气干湿沉降，大气颗粒物、大气中的Hg含量水平和空间分布模式进行了系统研究，查明北京地表土壤Hg平均含量为0．41mg／kg，大气干湿沉降物中的Hg平均含量为0．194mg／kg，壤中气Hg的平均含量为559．65ng／m^3，大气颗粒物PM10和PM2.5中的Hg含量分别为0．59和0．67ng／m^3，大气中的Hg平均含量为3．13ng／m^3。北京市自2000年起实现了由燃煤转变为燃气的减排措施，导致干湿沉降物中的Hg沉降通量显著减少，2006年大气干湿沉降物中Hg的沉降通量1．837mg·m^-2·a^-1,北京市城区（近1000km2）Hg全年沉降为1837kg，空气中总Hg浓度由1998年的8．3～24．7ng／m^3下降到2006年的3．13ng／m^3，大气颗粒物中Hg含量由2003年的1．18ng／m^3下降到2006年的0．59ng／m^3（PM10）和0．67ng／m^3（PM2.5），表明北京市煤改气减排措施的实施显著改善了大气环境质量。通过对土壤中Hg的存在形式研究，发现土壤中有硫化物（辰砂）及各种Hg盐（HgCl2）的含Hg矿物，Hg也可以各种吸附方式或壤中气方式存在。研究证实北京壤中气Hg与大气Hg存在显著的相关性（n=131,R=0．267，p〈O．01），表明壤中气Hg是大气Hg的重要来源之一。利用2005年地表土壤总Hg与Hg释放速率的线性方程估算，土壤Hg平均释放速率为102．42ng·m^-2·h^-1，2005年土壤释放进大气的Hg通量为936．70kg。在查明土壤中存在大量辰砂矿物的同时，还分布有大量具有高温熔融特征的金属微球粒和玻璃质微球粒，证明燃煤和冶金烟尘是地表土壤Hg的主要来源。土壤中Hg、S、pH和辰砂颗粒浓度在空间上的高度耦合性表明，碱性条件下，土壤中高含量的S和Hg是辰砂形成的重要原因。按国家土壤环境质量标准，北京市I级土壤Hg环境质量的面�Mercury enrichments or anomalies in soils in urban and town areas are a general phenomenon in China, and investigation on source, transport cycle and fate of Hg in soil is essential for evaluating environmental risks. Soil Hg may be derived from natural and/or anthropogenic sources and may be deposited by wet or dry processes. Emitted Hg may be also derived from the re-emission of Hg that was previously deposited to the soil from the atmosphere. It is important to understand the relative magnitude of emission, deposition, and reemission of Hg associated with ecosystem of cities with soil Hg anomalies because for these cities being the center districts of human activity, the aggravated Hg pollution would result in serious dangers to environment and human health. The major focus of this paper is to discuss soil-air Hg exchange process, occurrence forms of mercury for high concentration Hg soils in Beijing, China. This information is important for developing eco- geochemical mass balances, assessing the effectiveness of regulatory controls of Hg emission from coal combustion. Data collected from field and laboratory are presented. An extension measurement of mercury in soil covered 1044 km^2 with a density of 1 sample/km^2 were carried out within the Beijing areal 19 samples of dry and wet deposition, and 20 samples of airborne particles （PM10 and PM2.5） with a relatively uniform distribution using a grid design based on 7 km×7 km were collected. 131 atmospheric mercury samples and soil gas mercury samples in mercury enrichments area and 66 samples in mercury background area were sampled. Resuits indicate that the average content of Hg is 0. 410±0. 403 mg/kg in soil, 0. 194±0. 058 mg/kg in dry and wet precipitation, 3.13±2.35 ng/m^3 in atmosphere, 559.65±1177.36 ng/m^3 in soil gas, 0.59±0. 26 ng/m^3 and 0. 67±0. 49 ng/m^3 in PM10 and in PM2.5, respectively. Hg emission from coal combustion has been significantly reduced to 1836 kg in 2006 compared with the emission of 8830 kg in 1999, because the Beijing

关 键 词：城市土壤Hg异常 成因来源 输入输出通量 北京 

分 类 号：X53[环境科学与工程—环境工程]