| Due to the increasingly serious heavy metal pollution in our country,It is necessary to carry out the investigation,risk assessment and source analysis of heavy metals and ammonia nitrogen in agricultural land,which has certain theoretical and practical significance.In this paper,heavy metals and ammonia nitrogen in the soil of Xuzhou City were selected as the research objects.The heavy metals and ammonia nitrogen were analyzed by using the methods of statistics and image interpolation.At the same time,the heavy metals were analyzed by using the methods of semi-variance parameter model fitting,risk assessment and pollution source analysis.It shows the content and distribution characteristics of heavy metals and ammonia nitrogen in Xuzhou agricultural land,and reveals the risk and source of heavy metals.The main achievements are as follows:(1)There exists accumulation of Cu and Cd in soil while other heavy metals are not founded accumulation phenomenon.Cd presents the highest variability and worst normality.In heavy metal normality test,Cd does not conform to normal distribution and it is the most severely affected heavy metal by human activities.(2)The soil ammonia nitrogen in region Y and region H shows poor normality,thus the fertilizer plant and treatment plant site might have more serious influence on the surrounding soil ammonia nitrogen.Moreover,the correlation between ammonia nitrogen,p H and water content is not obvious.(3)The linear model,exponential model,spherical model and Gaussian model were used to perform semi-variance parameter fitting for soil heavy metals in each region,and the linear model was the best fitting for most heavy metals.In some areas,copper and lead showed strong spatial correlation,while heavy metals had a relatively high spatial correlation with weak spatial correlation.(4)The distribution of Kriging interpolation mainly focuses on rationality,but it may ignore the existence of high points.The gradient of some adjacent points in the inverse distance weight method is larger.It can be seen from the distribution map that the pollutants in the soil are easily blocked by highways,resulting in the reduction of the migration speed of pollutants.(5)The risk assessment results of different heavy metals are different,and copper and cadmium in the index evaluation method are more serious.The soil environmental quality assessment method indicated that there were strictly controlled areas in the region.The human health risk assessment method found that the carcinogenic and non-carcinogenic risks of cadmium and copper were the most serious.Children have a higher risk of non-cancer than adults,who have a higher risk of cancer than children.There was an acceptable carcinogenic risk,but no obvious carcinogenic risk.(6)The sources of soil pollutants in the study area mainly include soil parent material,traffic pollution,industrial pollution and pesticide and chemical fertilizer pollution.The cluster analysis of region 1 is the same as that of the tending,and the cluster analysis of region 3 is the same as that of region 4.Correlation analysis showed that a few heavy metals had correlation,while chromium and nickel had antagonistic effect.Through factor analysis,the number of pollution sources in each region is 2,and the contribution rate of pollution factors is determined.Through PMF model analysis,the number of pollution sources in Region 1,Region 2 and Region 3is 3.The number of pollution sources in Region 4 is 2.The types of pollution sources and their contribution rate are determined. |
