Pollution Characteristics and Evaluation of Heavy Metal Pollution in Surface Soil Around a Municipal Solid Waste Incineration Power Plant

Abstract

To investigate and evaluate the pollution levels of heavy metals in the soil around a large Municipal Solid Waste Incineration power plant (MSWIPP), a total of 29 soil samples were collected around the MSWIPP and away from the power plant area. The contents of 10 selected heavy metals (Cr, Mn, Ni, Cu, Zn, As, Ag, Cd, Hg, and Pb) were analyzed. The results showed that the content of each heavy metal element did not exceed the values for Soil Environmental Quality of Risk Control Standard for Soil Contamination of Agricultural Land (GB15618-2018) and Development Land (GB 36600-2018). The mean contents of Mn, Cu, and As were higher than their respective background values of Anhui Province, where As was 1.03 times the background value, and Cu was 1.07 times. Compared with the control points, the contents of Cr, Ni, Cd, Cu, and As were lower than the control points, and the difference was statistically significant (P ≤ 0.05). The spatial distribution of Hg was more obvious in the soil around the power plant, and other heavy metals were not obvious and uniform. The content of Hg was the highest in the 500 m soil of perennial dominant downwind and sub-dominant downwind. With increasing distance from the power plant, the content gradually decreased and it was lower than the level of the control point. The pollution degree of heavy metal elements in the soil around the power plant and in the plant area was mild. The Nemero comprehensive pollution index (PI) was 1.1-1.2, and the control point had also mild pollution (PI was 1.5). The potential ecological risk was slight, and the comprehensive potential ecological risk index (RI) of various heavy metal elements was 60.2-67.7. The contribution rate of Hg and As to RI were large, and the control point had medium ecological risk (RI was 116.8). Based on the results of principal component analysis, accompanied with the content, spatial distribution characteristics, Pearson's correlation, and hierarchical cluster analysis results, three groups of heavy metals with different spatial distribution were identified:①Ni, Cr, As, and Mn originated from lithological sources; ②Cu, Zn, Ag, Cd, and Pb affected by both lithological and human sources (e.g. agricultural and traffic sources); ③Hg likely originated from the diffusion sedimentation of MSWI flue gas and its accumulation in the soil. The above results indicated that the unique pollution characteristics of Hg deserve serious attention in pollution monitoring in soils surrounding solid waste incinerator.