Elemental Geochemical Characteristics of Topsoil in Tangchang Town, Chengdu, Sichuan Province and Quality Evaluation

The quality of soil is directly related to human health and the safety of agricultural products, which has important references for agricultural planting and land planning. As an important vegetable basket base in Chengdu, Tangchang Town has developed agricultural planting, but the recent soil quality in the region is still unclear.

In order to accurately understand the current content of nutrient and heavy metal elemental characteristics and soil quality grade of topsoil in the Tangchang agricultural planting area.

According to 1∶50000 soil quality geochemical survey, 810 topsoil samples were collected. The contents of N, P, K, As, Cd, Hg, Pb, Cr, Ni, Cu, Zn, Se and pH in these soil samples were determined by X-ray fluorescence spectrometry, inductively coupled plasma-mass spectrometry, atomic fluorescence spectrometry, element analyzer and ion selective electrode method. The element geochemical characteristics and soil nutrient grade, soil environmental quality grade and comprehensive soil geochemical grade were then evaluated.

(1) Compared with the general topsoil in China, Zn and Pb in the topsoil of the study area are slightly enriched, Se is relatively enriched, N, P, Cd and Hg are strongly enriched. The topsoil is generally weakly acidic. (2) The comprehensive grade of soil nutrients is rich in second grade, accounting for 88.0% of the area, and the soil fertility is rich. The proportion of the first grade soil area in the environmental quality grade of the eight heavy metal elements in the soil is more than 96.0%, and the comprehensive environmental quality grade is dominated by first grade clean type, accounting for 98.06%. The comprehensive quality of soil is mainly grade one, accounting for 85.85%. (3) The area of selenium-rich soil in the region is 2.49km², accounting for 3.7%, sporadically distributed in the central study area. Copper-rich soil area is 63.13km², accounting for 94.0%, and zinc-rich soil area is 63.31km², accounting for 94.17%.

In summary, the nutrients of topsoil in Tangchang Town are rich, the soil environment is clean and the comprehensive quality of the soil is high.