镇江谏壁热电厂煤灰库对周边土壤硒的环境影响

镇江谏壁热电厂始建于1959年,是华东电网的主力电厂之一,已创下发电量连续26年超100亿kW/h的非凡业绩,产生了大量的粉煤灰.选取龙山煤灰库和贞观山煤灰库作为研究对象,对煤灰库区的粉煤灰、地表水及其周边水系沉积物、岩石、土壤、水稻籽实等不同类型样品进行分析,发现表层土壤受粉煤灰影响存在Se富集,按照谭见安的划分标准,足Se和富Se土壤分别占总面积的32.96%和43.08%;Se不足和Se缺乏土壤分别占总面积的7.86%和6.76%%;Se过剩土壤占总面积的9.34%,主要分布在煤灰库下游附近,最大值达14.7×10-6.调查表明,离煤灰库较远的农田Se主要来自高Se含量灌溉水,离煤灰库较近的农田除受高Se含量灌溉水影响外,同时还受到随水迁移的粉煤灰沉积物的叠加影响.根据Se与重金属元素聚类树状图判断,土壤在输入Se的同时亦输入了一定量的Cd、Hg和Pb,从输入量看Hg>Cd>Pb.总体上,表层土壤As、Cd、Cr、Cu、Hg、Ni、Pb和Zn等重金属元素含量多小于相应的土壤环境质量一级标准(自然背景值),浓度未达到污染水平,只有Cd和Hg的最大值接近农田土壤二级标准.受土壤环境影响,区内存在富Se大米,且大米中As、Cd、Cr、Hg、Pb等重金属元素的含量没有出现超标现象,表明该地区具备生产富Se大米的潜力.建议在该区域利用不同水源进行灌溉,从而调整土壤中Se含量,即对土壤Se缺乏区域灌溉高Se含量水,使富Se土壤区域扩大,对已存在Se过剩的土壤引用一般水源灌溉,使之范围缩小,含量降低.通过该项研究得出一个结论:粉煤灰中含有较高的Se,而有害重金属含量甚少,因此可提取Se或将粉煤灰直接添加到肥料中制成富Se肥.

The effects of coal ash storage of Zhenjiang Jianbi Power Plant on the selenium concentration of the surrounding soil environment

Built in 1959,the Zhenjiang Jianbi Power Plant is one of the main power plants in the power grid of East China.Its total power generation has hit over 100 billion kWh in the past twenty-six years.Nevertheless,a significant amount of coal ash has also been generated.To investigate the environmental effects of coal ash,the authors selected Longshan Ash Mountain and Zhenguan Ash Mountain as the study objects.Testing the samples of coal ash,surface water and its surrounding sediments,rocks,soil,and rice seed around the coal ash mountain areas,the authors have found that the topsoil in the study area is rich in selenium (Se) due to the influence of coal ash.According to the classification criteria set by Tan Jianan,32.96% of the soil contains a medium level of Se,43.08% is rich in Se,7.86% is low in Se concentration,6.76% is very low in Se concentration,and 9.34% contains excessive Se.The soil with excessive Se is mainly located around the downstream coal ash area,with a maximum amount of 14.7× 10-6.It is found that the richness of Se in the farmland far away from coal ash areas mainly stems from high Se concentration in the irrigation water,while the richness of Se in the farmland close to coal ash areas is attributed not only to irrigation but also to the sediments of coal ash brought by the water flow.The dendrogram analysis of Se and heavy metals shows that the region affected by Se is also affected by Cd,Hg and Pb.The richness of these heavy metals is ranked as Hg > Cd > Pb.The topsoil is generally not contaminated by As,Cd,Cr,Cu,Hg,Hi,Pb,Znand other heavy metals because the concentration of these heavy metals is less than the natural amount.Only the concentration of Cd and Hg is close to the maximum of the second degree in the national farmland standard.Affected by soil environment,the study area has Se-rich flee,whose concentration of As,Cd,Cr,Hg,Pb and other heavy metals does not exceed the food contamination standard.Based on these findings,the authors suggest using different irrigation sources in the study area.Specifically,we should use Se-rich water to irrigate the Se-insufficient soil so as to expand the area with Se-rich soil,and use the average water to irrigate the Se-excessive soil so as to reduce Se concentration.The results of the study also imply that coal ash is rich in Se and contains very little harmful heavy metals.Therefore,it may be profitable to extract Se from coal ash and produce Se-rich fertilizers.