北京市土壤重金属潜在风险预警管理研究

EARLY WARNING OF HEAVY METALS POTENTIAL RISK GOVERNANCE IN BEIJING

区域土壤重金属的潜在环境质量风险预警研究是区域土壤重金属管理研究的热点之一。以北京市为研究区,在镇域尺度上建立土壤重金属输入-输出通量模型和重金属年累积率模型,计算2006年北京市各乡镇Cr、Ni、Zn、Hg、Cu、As、Cd、Pb八种重金属的通量和累积量。以2006年作为基期年,采用指示克里格法预测北京市未来30 a土壤重金属含量变化趋势和环境质量风险。研究表明,在当前发展趋势下,未来30a北京市Pb、Cr和Ni土壤环境污染风险较小,含量均处于国家土壤环境质量二级标准以下;Cu、As和Zn最高达到中警级别,Hg和Cd的污染风险变异较大,各预警级别均有出现,但概率大小不等,其中Cd的环境风险最为严重,高风险区部分位于北京市东部,呈带状分布;Hg的环境高风险区域随城市的扩张而蔓延。采用地统计学与区域物质流通量模型结合的方法,可为区域土壤重金属的宏观预警研究提供技术支撑。

The probability of heavy metal potential risk is gradually increased with the development of industry, agriculture and urbani2ation. Early warning of heavy metal potential risk becomes one of the hot topics of the land environmental risk management. The methods and strategies for risk countermeasures of heavy metal pollution was developed in Beijing study area, and the prediction of variation trend and environmental quality risk was calcalated for the next 30 years. In Beijing study area, input-output flux model and heavy metals accumulation rate model were established at town-wise units by taking into account the datasets acquired from the literatures, statistical yearbooks and field survey. Fluxes and accumulation of Cr, Ni, Zn, Hg, Cu, As, Cd and Pb were calculated following the material balance principle in 2006. 2006 results as a reference base, the trend and environmental quality risk of each heavy metal was estimated based on criteria of the early warning： system for the next 30 years. The spatial pattern of the trend and early warning for each heavy metal was interpolated by the probability model of Kriging. Results show in the next 30 years, （ 1 ） the risk of Pb, Cr, and Ni were relative lower, and their concentrations will linger below Grade II criteria of the national standard for soil environmental quality, and the other metals will be over Grade II criteria of the national standard with ,：lifferent degrees of environmental risk. （ 2 ） Compared with Ni and Cr, the high risk values ofPb are mainly distributed in the urban area, where primary atmospheric deposition. Cr and Ni content are higher in the northeast of Beijing, where the corresponding control measures should be taken. （ 3 ） Cu, As and Zn will maybe reach medium level, while Hg and Cd may be up to alarm level three and level four. As and Zn have low potential risk with the similar tendency of heavy metal potential risk early warning, indicating their homology sources from soil parent materials. The risk of Hg and Cd will vary spatially in warning levels and probability. Among the 8 heavy metals, Cd will be highest in environmental risk with the large areas, and some of the risk will mainly spread in the far-reaching suburban related to agricultural activities. The high Hg risk areas will expand with the urban sprawl largely by human influence. Firstly, eight heavy metals show different environmental risk levels, relevant departments should make difference control measures for different regions according to specific environment risk levels and types of soil heavy metal pollution. Secondly, the geostatistics technology coupled with the regional flux model could provide an excellent technical tool for macro-scaled early-warning of regional soil heavy metals pollution.