IDENTIFICATION OF SOURCES OF METAL IN THE AGRICULTURAL SOILS OF THE GUANZHONG PLAIN, NORTHWEST CHINA

A comprehensive survey was conducted to assess the possible sources and distribution of metals in the agricultural soils of the Guanzhong Plain in northwest China. In total, 227 samples of agricultural soil were collected to determine the content of Pb, Cr, Co, V, Ni, Zn, Cu, As, and Mn by X-ray fluorescence spectrometry. The mean concentrations of metals were 26.2 +/- 10.8 mg kg(-1), 71.5 +/- 16.8 mg kg(-1), 12.7 +/- 1.81 mg kg(-1), 85.1 +/- 7.86 mg kg(-1), 30.5 +/- 6.17 mg kg(-1), 71.1 +/- 14.1 mg kg(-1), 25.2 +/- 5.58 mg kg(-1), 12.5 +/- 1.94 mg kg(-1), and 635.4 +/- 84.7 mg kg(-1) for Pb, Cr, Co, V, Ni, Zn, Cu, As, and Mn, respectively-slightly higher than the regional background values. Multivariate analysis was used to identify the metal sources, and it was found that Ni and Cr in the agricultural soils were mainly derived from lithological materials, and Pb, Zn, and Cu were mainly from traffic emissions; however, Zn and Cu also originated from mineral fertilizers or pesticides. The other metals originated from industrial emissions. The Nemerow index coupled with geographic information system technology was applied to assess the degree and spatial distribution of metal contamination; the soils studied were classified as slightly polluted, and the most contaminated regions were concentrated in the area surrounding Xi'an city, as well as areas in the southeast and north of the Guanzhong Plain. (C) 2016 SETAC