The Distribution And Ecological Risk Assessment Of Soil Magnetic Susceptibility And Heavy Metals From Different Functional Areas In Linfen

In this paper,the soil of Linfen is divided into five functional areas according to land use mode.A total of 217 soil samples were collected.From October2016 to October 2017,the soil heavy metal content such as Cr,Ni,Cu,Zn,As,Pb,Mn,pH value,organic matter and magnetic susceptibility?of all samples were measured in the laboratory,analyzed the spatial distribution characteristics of soil heavy metal content in Linfen,and studied the correlation of various indicators.At the same time,the single factor pollution index method?P_i?,Nemerow comprehensive pollution index method?P_N?,pollution load index method?PLI?and Hakanson potential ecological hazard index method?RI?,were used to evaluate the ecological risk status of soil heavy metals in the five functional areas of Linfen.Finally,principal components analysis?PCA?,scanning electron microscopy?SEM?and X-ray energy dispersive spectrometer analysis?EDS?were used to infer the sources of heavy metal elements and magnetic particles in the soil of Linfen.The main findings were as follows:?1?In the soil samples collected in the five functional areas of Linfen,except for Ni,the measured content of Cr,Cu,Zn,As,Pb and Mn in the industrial area were the highest in the five functional areas,they were 43.92,23.38,127.37,18.22,44.91,and 581.42 mg/kg,respectively,the content of Cu,Zn,As,Pb and Mn exceeded the soil background value of Shanxi Province.And the Ni content in the commercial area was the highest,it was 38.77 mg/kg,the content also exceeded the soil background value of Shanxi Province.The highest ecological risk level in the five functional areas of Linfen was Pb,which was 3.05 times the background value.According to the spatial variability map of soil heavy metal elements in Linfen,it could be seen that the measured seven heavy metal elements were relatively high in the central part of Linfen.Through Pearson correlation analysis,there was no obvious correlation between Ni and Cu,Zn and Pb,the correlation between several other heavy metals was more significant.?2?The high value of low frequency magnetic susceptibility?_lf in Linfen mainly distributed in industrial areas,which was consistent with the high value range of heavy metals in Linfen.The positive correlation between?_lf and Cu,Zn,As,Pb and Mn was better in Linfen,this correlation indicated that the magnetic susceptibility values could be used as a quick indicator for judging the accumulation of heavy metals in cities,factories,mining areas,and farmland.?3?According to the soil background value of Shanxi Province,the results of single factor pollution index method?P_i? showed that the accumulation of four heavy metal elements such as Pb,As,Zn and Ni in the five functional areas of Linfen were serious,especially the accumulation of Pb.Most of the industry,culture and education,commerce,parks,residents,five functional areas P_i were higher,the industrial area was in a state of heavy pollution,and the cultural and educational areas,commercial areas,park areas,and residential areas were lightly polluted;Nemerow comprehensive pollution index method?P_N? showed that the five major functional areas soil heavy metal P_Nsize:industrial area?2.43?>cultural and educational district?1.65?>commercial area?1.54?>residential area?1.45?>park area?1.43?,the industrial area had reached a moderate level of environmental ecological hazard under the strong influence of various human activities,and the other four functional areas environmental ecological risk status was very slight.?4?According to the pollution load index method that could determine the pollutant carrying capacity,the size of the pollution load index PLI_zone of Linfen's five major functional areas:industrial area,cultural and educational district,commercial area,park area and residential area:industrial area ?1.25?>commercial area?1.09?>cultural and educational district ?1.08?>residential area ?0.99?>park area?0.93?,industrial,commercial and cultural and educational areas had medium-level ecological risks,most cities residential areas and urban park areas such as Fenhe Park and Gucheng Park were characterized by good ecological environment conditions;According to the Hakanson potential ecological hazard index method,the polymetallic potential ecological risk index RI indicated:industrial area?50.96?>commercial area?40.37?>cultural and educational area?39.32?>park area?35.79?>residential area?35.67?,the RI of the five functional areas were all less than 150,the environmental and ecological hazards of human and nature were relatively light in the RI of 7 heavy metals in Linfen.?5?Principal Component Analysis?PCA?was used to explore the main sources of seven heavy metals such as Cr,Cu,Zn,As,Pb,Mn and Ni in the five functional areas of Linfen,Ni was mainly derived from the natural environment,and Cr,Cu,Zn,As,Pb,and Mn were strongly interfered and affected by humans such as industrial activities,transportation,and littering.The combination of observation and scanning of X-ray penetrating photoelectron spectroscopy by electron microscopy showed that irregular ferromagnetic particles related to metal casting and transportation were analyzed.The pollution assessment and source analysis of soil heavy metals in different functional areas of Linfen could provide a scientific basis for the treatment and improvement of soil ecological environment based on the leading causes of soil pollution.