GEOCHEMICAL EVALUATION OF LAND QUALITY IN GAOQIAO TOWN, CENTRAL YUNNAN

A total of 453 topsoil samples are collected at a density of 1.12 cores per square kilometer in Gaoqiao Town of Wuding County. The heavy metal elements such as As, Cr, Cd, Cu, Hg, Pb, Ni and Zn are evaluated for soil environment geochemistry. The soil quality is assessed as first and second grades, with the first-grade area of 350 km², accounting for 84.95%, and the second-grade area of 62 km², making up 15.05%. Cu and Cd in some parts of the area show abnormal but do not reach pollution levels. The contents of nutrient elements such as N, P and K are evaluated for soil nutrient geochemical grading, with about 378 km² above medium level, occupying 91.74%. The nutrient-deficient parts are close to densely-populated area, therefore it is inferred that the evaluation unit is seriously affected by human activities. From the above, the land quality geochemical evaluation for Gaoqiao Town shows a relative balance, with high-quality area about 101 km², accounting for 24.51%, good area 224 km² (54.37%), medium area 80 km² (19.42%), and no inferior area.