柴河铅锌矿尾矿库复垦治理中不同覆土与植被措施的效益估算

以铁岭柴河铅锌矿尾矿库复垦治理为例，根据尾矿库“生态封闭”原理，选取表层覆土50cm种植紫穗槐（措施1）、设置土工布隔离后覆土30cm种植紫穗槐（措施2）和厚覆土150cm种植刺槐与紫穗槐（措施3）等3种不同覆土及植被措施，运用影子工程法、替代成本法、恢复费用法和生态价值法等方法，构建尾矿库覆土与植被措施的效益估算模型，估算各措施的深层淋滤污染扩散防治效益、地表径流侵蚀扩散防治效益和风蚀扩散防治效益.效益估算结果表明：措施1、措施2和措施3的深层淋滤污染扩散防治效益分别为2975.24，3449.56，3604.75万元/a；3种措施可在不同程度上减少表层覆土流失、下游河道淤积及水体重金属污染，产生的地表径流侵蚀扩散防治效益分别为1222.66，2585.71，2586.75万元/a；3种覆土及植被措施均可有效抑制重金属风蚀污染扩散，产生的风蚀扩散防治效益分别为1235.45，1235.45，1237.86万元/a. 3种覆土及植被措施在重金属污染防治方面的综合效益分别为5433.35，7270.72，7429.36万元/a. 深层淋滤污染扩散防治效益在综合效益中所占比重最大，尾矿库覆土及植被措施的选择应以控制雨水入渗淋滤为主，结合降雨、蒸发等气象因素和覆盖土壤特性等，考虑治理成本，合理确定覆土厚度以及设置隔离层的必要性.

Benefit estimation of different soil covering and vegetation measures in the reclamation and remediation of the tailings pond of Chaihe lead-zinc mine

Taking the land reclamation and environment remediation of the tailings pond of Chaihe lead-zinc mine for example, according to the ecological closure principle for the tailings pond, three different soil covering and vegetation measures were selected, including 50cm of soil covering with Amorpha fruticosa L. (measure1), 30cm of soil covering after geotextile covering with Amorpha fruticosa L. (measure 2) and150cm of soil covering with Robinia pseudoacacia and Amorpha fruticosa L. (measure 3). Using the shadow engineering method, alternative cost method, restoration cost method and ecological value method, the benefit estimation modelsof the three measures were constructed to estimate the benefits of underground leaching and pollution diffusion prevention, surface runoff erosion and diffusion prevention, and wind erosion and diffusion prevention. The results showed that the benefits of measure1, measure 2 and measure 3 in the underground leaching and pollution diffusion prevention were 29.7524, 34.4956, 36.0475million yuan per year respectively. The three measures could reduce the losses of the surface covering soil, the sediment deposition of downstream rivers and the heavy metal pollution in different degree; their benefits of surface runoff erosion and pollution prevention were 12.2266, 25.8571 and 25.8675 million yuanper yearrespectively. The three kinds of soil covering and vegetation measures could effectively inhibit the diffusion of heavy metalsunder wind erosion; and their benefits of wind erosion prevention were 12.3545, 12.3545, 12.3786 million yuan per year respectively. Comprehensive benefits of the three kinds of soil covering and vegetation measures in heavy metal pollution prevention were 54.3335, 72.7072, 74.2936 million yuan per year respectively. For the three kinds of soil covering and vegetation measures’ comprehensive benefits, the benefit of underground leaching and pollutants diffusion prevention accounted for the largest proportion. The selection of soil covering measures should be based on the prevention of rainwater infiltration and leaching. Combined with meteorological factors such as rainfall, evaporation and covering soil characteristics, the thickness of covering soil and the necessity of setting up isolation layer should be reasonably determined by considering the reclamation and remediation cost.