Distribution of heavy metals in the topsoil of agricultural land in Nam Dinh Province, Vietnam

Surface soil samples were collected from different land use types of the agricultural land in Nam Dinh province, Vietnam to determine the level of heavy metal contamination and identifying potential sources. The farming areas of rice and cereal show similar heavy metal contents, however, the index shows that the content of heavy metals in the aquacultural area is lower compared to the other types. The mean enrichment factor (EF) values of Cr, Cu, Pb, and Zn are less than 1.5, suggesting that these are not a major concern in the research area; whereas, the mean EF values for Cd is higher than 2 and As varies from 5-20 suggest that the pollution of these heavy metals is present in agricultural soil. The data analysis indicates that Cr mainly originates from a natural source; Cd and As have a significant anthropogenic input; Cd, Pb and Zn have a mixed source.