| This paper takes the cultivated land soil of Nankai Township,Shuicheng County,Liupanshui City as the research object,and studies the geochemical characteristics and potential ecological effects of cultivated soil elements in this area.The main research contents include: geochemical characteristics of nutrient elements in surface soil;geochemical characteristics of heavy metal elements in surface soil;and evaluation of soil heavy metal pollution.Research methods: ICP-MS was used to analyze the composition of nutrient elements and heavy metal element in cultivated land,and geochemical maps of nutrient elements and heavy metal elements were respectively drawn.The geochemical characteristics of soil nutrient elements and heavy metal elements were revealed by interpretation of geochemical maps.Multivariate statistical analysis of heavy metal elements was carried out by factor analysis and cluster analysis to investigate the source of heavy metals in surface soil in the study area.The soil environmental quality of the study area was evaluated by single factor index,Nemero comprehensive index method and ground accumulation index method.The potential ecological hazard index of soil heavy metal proposed by Hakanson was used to evaluate the potential ecological hazard of heavy metals in soil,and the ecological environment effects were studied.Through the above research,the following main conclusions are drawn:1.The average value of soil pH is 6.36,ranging from 4.53 to 8.26 in the study area.From the perspective of spatial distribution,the soil in the study area is mainly acidic and neutral,and in the local area was weakly alkaline.The average content of soil organic matter is 6.45%,and the range of variation is 2.11-12.42%.It can be seen from the spatial distribution map that the spatial distribution of organic matter is uneven,and the high value areas are mainly distributed in the northern and southwestern areas of the study area,and the low value areas are more dispersed and widely distributed in the study area.2.The trace elements Se,Ge,Zn and B in soil were significantly correlated with organic carbon(p < 0.01),and the linear regression of Se,Ge,Zn was positively correlated with organic carbon,there was a significant negative correlation between B and organic carbon.The trace element Mo in soil was significantly correlated with organic carbon(p < 0.05),and the linear regression was positively correlated with it;the linear fitting relationship between soil trace element Mn and organic carbon was not significant(p>0.05).The trace elements Se,Ge,Zn,Mn,B in soil were significantly correlated with pH(p < 0.01)and negative correlation was found in linear regression,The linear fitting relationship between soil trace element Mo and pH was not significant(p>0.05).3.The average contents of heavy metals such as As,Cd,Cr,Hg,Pb,Cu,Ni and Zn in the surface soil of the study area were 15.78 mg/kg,0.92 mg/kg,142.38 mg/kg,0.08 mg/kg,33.97 mg/kg,100.62 mg/kg,62.12 mg/kg and 137.30 mg/kg,respectively.Compared with the soil background value of Guizhou Province,the average content of heavy metal elements Cd,Cr,Cu,Ni and Zn is significantly higher than that of Guizhou Province,Ni and Zn is significantly higher than that of Guizhou Province,and as the average content of Hg,Pb elements is lower than the background value,the coefficients of variation were 0.57,0.34,0.26,0.45,0.31,0.66,0.25 and 0.20,respectively,all of which were moderate variations.4.The correlation analysis,cluster analysis and principal component analysis of elements were carried out to classify Cd,Pb,Zn,Hg,Cr,Ni and Cu 7 heavy metal elements and harmful element As sources by SPSS software.According to similar geochemical processes of elements in the soil,the sources are divided into three categories: F1 is a combination of Cd,Pb and Zn elements with a cumulative variance contribution rate of 37.255%.Its average content is higher than the background value of soil in Guizhou Province,and the correlation coefficient is above 0.76.The spatial distribution characteristics are consistent,and the content of these elements is high near residential areas.In addition to inheriting into the parent rock,the distribution characteristics of such elements are greatly affected by human activities.Among them,and F1 is defined as an artificial factor;F2 is the combination of As,Hg,Cr and Ni with a cumulative variance contribution rate of 24.305%.These elements are mainly affected by natural factors such as parent rocks and are defined as natural factors;F3 is the element of Cu with a cumulative variance contribution rate of 18.243%.It is concluded that atmospheric deposition is the main factor affecting Cu distribution,and F3 is defined as atmospheric deposition.The results of cluster analysis are consistent with the results factor analysis.5.The evaluation results of heavy metal pollution in the surface soil in the study area showed that the main pollution elements were Cd and Cu,which reached the level of moderate and light pollution respectively,and the other six heavy metals were relatively clean and pollution-free.The potential ecological risk assessment results show that the potential ecological risk of soil heavy metals in this study area is high,and the comprehensive potential ecological hazard index(RI)of various heavy metals is 146.95,which is a medium ecological hazard,and the contribution rate of Cd and Hg to RI is relatively large,which is 37.09% and 32.09% respectively.The results show that Cd is the most harmful to the ecosystem.Therefore,the ecological risk of surface soil Cd in this area should be given close attention. |
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