HISTORICAL CHANGES OF SOIL METAL BACKGROUND VALUES IN SELECT AREAS OF CHINA

In our attempt to assess potential changes in the metal contents of soils in selected areas of China, soil profiles were sampled in three land use classifications: pristine areas represented by the Changbai Mountain Reserve and the prairies in Inner Mongolia; economically-developed areas around Shanghai and Nanjing noted for urbanization and agricultural production; and the suburbs of Shenyang in northeast China noted for heavy industrial activity. Seven metals (Cd, Pb, Cu, Zn, Ni, As and Hg) were analyzed from the same sites over a span of 50 years. It was observed that high coefficients of variation existed particularly for Cd and Hg within a 2 km by 2 km area. The metal contents remained relatively stable during this period in pristine areas that are relatively unimpacted by human activity. However, in urban areas and areas being impacted by industrialization and agricultural production, rather drastic changes in surface soil contents of some of the metals particularly Zn, Pb, Cd, Cu, As and Hg were observed.