中国土壤环境质量标准中重金属指标的筛选研究

SCREENING OF CRITERIA FOR HEAVY METALS FOR REVISION OF THE NATIONAL STANDARD FOR SOIL ENVIRONMENTAL QUALITY OF CHINA

我国土壤重金属污染问题十分严重,但目前国家的土壤环境质量标准已不适应当前土壤环境管理的需求,在指标体系上主要体现在重金属污染物项目过少,对一些新出现的污染问题无法有效监管。本研究通过深入调研美国、加拿大、荷兰、德国、澳大利亚、日本、中国台湾和香港等发达国家和地区的土壤环境标准,并将他们的重金属指标与我国现行的土壤环境质量标准中的重金属指标进行系统比较分析,提出我国土壤环境质量标准中重金属指标的修订建议。主要是要补充六价铬、有机汞等高毒害重金属价态和形态的标准;新增铍、锑、铊、钒等新型重金属污染物的土壤环境质量标准;同时,结合石灰(岩)土高背景区土壤,探索建立基于有效性的土壤重金属浸提态标准体系;为实现我国土壤重金属污染的风险管理提供科学依据。

Soil pollution,in particular,soil heavy metal pollution is a severe problem in China,which has now come to the extent of threatening food security of the nation, for heavy metals accumulate in edible parts of the crops produced in some severely contaminated areas. However the currently used standard for soil environmental quality does not fit the de- mands of the soil environmental management today, which manifested in the index system is that the number of indices cov- ering heavy metals pollution is limited. So far the standard of China has only eight heavy metals covered, much fewer than that of the USA, Canada, the Netherland etc. , which has led to inefficient management of some soil pollution problems popped up recently with the development of economy in China. Therefore, the objective of this study is to find the gaps be- tween China and those developed countries and regions in the establishment of soil standard for heavy metals, and to pro- vide some proposal for the revision of China＇s soil environment quality standard in the future. A worldwide investigation has been conducted on the soil environmental standard of those developed counties and re- gions, such as USA, Candia, the Netherland, Germany, Australia, Japan, Taiwan （China） and so on. The item counts, kinds and species of the heavy metals involved in these soil standards were mainly concerned of. Meanwhile, in depth study and systematic analysis was conducted of indices of heavy metals in the standards for soil environment of some developed coun- tries and regions for comparisons with ours. Similarity and difference were both found based on tbe comparison. The similar- ity is that the high toxic elements such as Cd, Hg and As are contained in the soil standards of most countries and re- gions. The differences are mainly in relation to the speciation of the elements. The hexavalent chromium and organic mercu- ry are contained in the soil standard of some developed countries and regions due to their high toxicities. However,stand- ards of chromium and mercury are simply provided based on the total content in China＇s Soil Environmental Quality Stand- ard. Another difference is the usage of extractable speciation in addition to the total content of heavy metals in the standard of some developed countries such as Germany, Switzerland and Japan while not in the standard of China. This could be ow- ing to the large diversity of soil types in China and be difficult to find a common extracting agent for all the soil types. Meanwhile, China has its own characteristics in soil heavy metal pollution, which includes beryllium, antimony, thal-lium and vanadium pollution as a result of high geochemical background in the calcareous rock soil or some mining areas that mainly located in the south China. These heavy metals pollution have threatened to human health of local residents. On such a basis, suggestions are put forth for revising the current standard of the country,including amendment of the criteria for valences and forms of highly toxic heavy metals,like hexavalent chromium and organic mercury; setting up of criteria for newly emerged heavy metal pollutants,like beryllium, antimony, thallium, vanadium, etc. ; and exploration for establish- ment of a bioavailability-based index system for extractable forms of heavy metals,by taking into account soils or rocks in calcareous regions with high heavy metals background values, so as to provide some scientific basis for management of soil heavy metal pollution risks in China.