Characteristics And Ecological Risk Assessment Of Heavy Metal Pollution In Qianxi Thermal Power Plant In Guizhou Province

In most areas of southwestern China,thermal power generation is still the main method.The construction and operation of coal-fired thermal power plants can pollute surrounding soil,and even damage the ecological environment and diversity of plant species.The impact of the long-term operation of Qianxi coal-fired thermal power plant on the local ecological environment is still unknown.Therefore,this study takes the soil and plants of Qianxi coal-fired thermal power plant as the research objects.Soil samples around the thermal power plant were collected,the total amount,form,source,spatial distribution and pollution situation of heavy metals are analyzed.The human health risk model is used to evaluate the potential harm caused by ingestion of soil.The content and enrichment characteristics of heavy metals in plants corresponding to soil were analyzed.At the same time,the biodiversity,composition of vegetation species and dominant plants in the study area were investigated,and the plants with high accumulation of heavy metals were selected.The main conclusions of this study are as follows:(1)The soil in the study area is currently not contaminated by mercury(Hg).But cadmium(Cd),arsenic(As),chromium(Cr),lead(Pb)and copper(Cu)are all overstandard to some extent,and among which As is the most serious.The As in soil is mainly existing with organic and iron manganese oxidation state,which has higher ecological risk.In addition,the evaluation of single factor pollution index and Nemerow comprehensive pollution index also showed that the pollution of As was the most serious.(2)The spatial distribution characteristics of heavy metals indicate that the content of heavy metals is relatively high in the northeast and southeast regions of the study area.Correlation and PMF source analysis showed that there were five main sources of heavy metals in the soil around the study area.Hg mainly comes from natural sources(soil parent material);Cu mainly originates from agricultural activities(fertilization,etc.);Cd and Cr mainly come from industrial emissions;As mainly comes from the dust emitted from coal combustion;Pb mainly originates from transportation.(3)By evaluating the health risks in the study area,it can be found that the main contributors to non-carcinogenic risk and carcinogenic risk are As,both in adults and children.Children are more vulnerable than adults.(4)From plant enrichment characteristics and metal accumulation index,the plants collected from the study area do not show good enrichment for Cd,Cr,Pb and Cu.Ligustrum lucidum Ait has a good enrichment capacity for As,while Sabina chinensis(L.)Ant.showed a strong enrichment for Hg.(5)From the perspective of dominant species of plant community,the herbaceous plants are mainly Imperata cylindrica(L.)P.Beauv.,the shrub plants are mainly Viburnum dilatatum Thunb.,and the arbor plants are mainly Pinus massoniana Lamb.The mountains with the best diversity are in the northwest and southwest directions of the thermal power plant,while the diversity of the mountains is slightly lower in the northeast and southeast directions,heavy metal pollution caused by thermal power plants may be one of the reasons for low mountain diversity in the northeast and southeast directions.