Study on accumulation characteristics of heavy metal elements in topsoil of southern Longhai City,Fujian Province

Based on the test data of the heavy metal elements contents and pH values obtained in topsoil of southern Longhai City, Fujian Province in 2004 and 2015, the cumulative change characteristics and influencing factors of Cd, Hg, Pb, As, Cu, Zn and pH values over the past 11 years were analyzed by mathematical statistics method. The result shows that the content of Cd, Cu, As and other heavy metal elements showed a positive accumulation trend to a certain extent in southern surface soil of Longhai City, among which the average relative accumulation rates of As and Cu were 4.943% and 5.486% respectively, Hg showed a significant dilution trend with the average relative accumulation rate was -12.833%. The pH values showed a significant trend of acidification, which showed a certain difference among different soils in the study area. Besides, the changes of Pb and Zn were not significant. It is concluded that elements with high average accumulation rate in basalt background area of the study area are the most, such as Cd, Pb and As, elements with low average accumulation rate in the background area of intermediate-acid volcanic rock are the most, such as Cu, Pb, Zn and As,and elements with higher average soil accumulation rate in the garden are the most, such as Cd, Pb, As and Hg, while elements with low average accumulation rate in cultivated land are the most, such as Cd, Cu, As and Hg. In addition, human activity is also an important factor causing the accumulation or depletion of heavy metals in topsoil of southern Longhai City.