燃煤电厂重金属排放与周边土壤重金属污染评价

Heavy metal emission of coal-fired power plant and assessment of heavy metal pollution in surrounding soil

为研究燃煤电厂重金属排放对周边土壤重金属污染的影响,测定了某燃煤电厂烟囱入口烟气中Cd、Cr、Hg、Ni、Pb、As含量,同时根据当地气象及地形条件,在燃煤电厂周边采集19个土壤样品,分析了土壤中重金属含量及分布情况,并对其污染程度进行评价。结果表明,燃煤电厂烟气中6种重金属元素的质量浓度为0.02~2.00μg/m^(3),向大气中排放各种重金属元素为0.18~19.08 kg/a,单位发电量的重金属排放量满足美国环境保护署对火电厂重金属排放的要求。Cr、Hg在燃煤电厂常年主导风向下风向含量较高,与周边土壤中含量呈正相关关系,是燃煤电厂气态污染排放的特征元素。燃煤电厂周边各个方向土壤中重金属元素含量随烟气排放距离增加呈先增大后减小的趋势。燃煤电厂周边土壤中Cd、Hg、Ni、As处于中度污染水平,Cr、Pb处于轻微污染水平,需进一步加强烟气中重金属脱除的技术手段。

In order to investigate the effect of heavy metal emission from coal-fired power plant on surrounding soil heavy metal pollution,the concentration of Cd,Cr,Hg,Ni,Pb and As in inlet flue gas of a coal-fired power plant chimney was determined,19 soil samples around the coal-fired power plant were collected according to local meteorological and landform condition.The content and distribution characteristic of heavy metals in soil were analyzed,and the pollution degree was also evaluated.The results showed that the emission concentrations of six heavy metals in flue gas of coal-fired power plant ranged from 0.02μg/m^(3) to 2.00μg/m^(3),and the emissions to the atmosphere ranged from 0.18 kg/a to 19.08 kg/a.The heavy metal emissions per unit of power generation could meet the requirements of United States Environmental Protection Agency for heavy metal emissions from coal-fired power plant.The contents of Cr and Hg were higher in the downwind direction of the dominant wind direction,and they were positively correlated with the content of Hg and Cr in the surrounding soil.Cr and Hg were the characteristic elements of gaseous pollution emission from the coal-fired power plant.The contents of heavy metal elements in soils around coal-fired power plant increased firstly and then decreased with the increase of flue gas emission distance.Cd,Hg,Ni and As in the soil around the coal-fired power plant were at moderate pollution level,while Cr and Pb were at slight pollution level.It was necessary to further strengthen the heavy metals removal technology from flue gas.