Spatial distribution and quantitative identification of contributions for nutrient and beneficial elements in top- and sub-soil of Huairou District of Beijing, China

Abstract

To control agricultural and ecological risk, it is significant to monitor the quality of nutrient and beneficial elements (NBEs) in soils, particularly in agricultural area. For this purpose, it is important to clarify NBEs content and distribution, potential sources, and enrichment or depletion mechanism in soils. However, in present studies, the sources identification for soil NBEs and quantification of contributions for multiple sources, remains controversial. In order to solve these problems, in this case, a total of 977 topsoil samples and 258 subsoil samples were collected at Huairou District of Beijing. The content of some NBEs (K, Ca, Mg, V, Mn, F, Ge, N, Se, P, Zn, and S) were analyzed for each sample, and spatial distribution were presented with some values indicating soil properties (TFe2O3, Al2O3/SiO2, total organic carbon (TOC), and pH). The main influence factors of NBEs distibutions in soils were determined by the methods of principal component analysis (PCA), redundancy analysis (RDA), and positive matrix factorization (PMF) analysis. Combined with analysis result and geochemical process, it suggested the enrichment mechanism of NBEs in soils mainly impacted by soil parent material, the local external sources, and elements migration of eluviation in study area. Furthermore, the major contribittions of each NBEs either in topsoil or in subsoil were quantitatively determined. Generally both in topsoils and in subsoils, the source inherited from soil parent material account for 34.65–58.97% contribution to Zn, Mn, Mg, V, F, Ca, K, and Ge; the local external sources accounted 40.66–68.99% for N, S, Se, and Zn; and eluviation contributed 37.45–67.07% of Ca, P, and K. The enrichment degree of NBEs in topsoils were processed by standardized concentration ratio model, which effectively demonstrated elements inheritance from subsoils to topsoils. In addition, the soil quality evaluation was conducted on the basis of NBEs concentration classificaiton. This study quantitatively estimated NBEs sources in soils and their quality, which provided a basis for agricultural activities and ecological environment protection in typical suburban area.