GEOCHEMICAL CHARACTERISTICS OF SELENIUM IN THE SOIL-CROP SYSTEM OF KESHAN COUNTY, HEILONGJIANG PROVINCE.

Keshan County in Heilongjiang Province is the place after which the endemic Keshan disease was named. By analyzing 809 topsoil samples (0-20 cm) and 205 deep-soil samples (150-200 cm), the paper studies the characteristics of selenium (Se) content in soil and crop seeds and available Se content by different soil types. The results show that the average Se content in surface soil is 0.249x10^-6, lower than the national average and higher than that of the world and Heilongjiang Province in Northeast China Plain, mainly characterized by Se-sufficiency, with the area accounting for 93.95%. The average Se content in deep soil is 0.167x10^-6, obviously lower than that in surface soil, with the Se-low and Se-deficient soil areas making up 62.62%. The Se content in surface layer of different soil types from high to low is chernozem and meadow soil (the same), followed by black soil and dark brown soil. On the contrary, the Se content in deep layer is dark brown soil, black soil, meadow soil and chernozem in order. The Se content of different land use types show that the Se content in construction land and cultivated land is high, that in forest land and water conservancy land low, indicating the Se content is obviously affected by human activities. The Se content in seeds of main crops such as maize, soybean and rice is 0.033x10^-6 averagely, showing the characteristics of low-Se. [ABSTRACT FROM AUTHOR]