THE NATURAL BACKGROUND VALUES OF SOME TRACE ELEMENTS IN THE IMPORTANT SOIL TYPES OF BEIJING AND NANJING AREAS
The Group of Natural Background Values of Soil, Academia Sinica
The contents of Cu, Be, Zn, Cd, Hg, Se, La, Pb, As, Se, Cr, Mo, Mn, Co, and Ni in the important soil types of Beijing and Nanjing areas were measured by physical and chemical methods. Data concerning the mean value and the standard deviation of these elements both in various soil types and in the different horizons of each soil profile are given in the tables of the Chinese text. Results of present investigation may be summarized as follows. Variations of the content of trace elements of a soil were largely dependent on their parent materials. Soils derived from different parent materials, even belonging to a same soil type, usually show a rather great divergency in background values of trace elements while similarities of the values of trace elements were still perceived in different soil types derived from the same parent material. Present investigation also revealed that soils derived from basic rocks, as a rule, possessed higher background values of trace elements than those from the acidic rocks as shown in the following descending order: basalt, limestone shale granite, sandstone. To soils developed on the recent deposits, greater background values of trace elements often appeared in those soils with a heavier texture. The contents of trace elements in the surface horizon of the soil nearby the city were seriously affected by the urban industrial pollution. However, it is still possible to judge their natural background values by referring to the data obtained in substratum.