Insights into site-specific influences of emission sources on accumulation of heavy metal(loid)s in soils by wheat grains.

Abstract

Excessive accumulation of heavy metal(loid)s in agricultural environment usually originates from anthropogenic activities. Both large diversities of emission sources and complexity of plant accumulation challenge the understanding of the site-specific effects of emission sources on heavy metal(loid)s in wheat grains. Herein, both soil samples and wheat grain samples (n = 80) were collected from the farmland of Jiyuan City, China. Soil and grain burdens of heavy metal(loid)s were determined by inductively coupled plasma mass spectrometry (ICP-MS) and/or X-ray fluorescence spectrometry (XRF). The quotients (Q) were developed to indicate relative impacts of industrial plants and traffic to soil sites. Principal component analysis-absolute principal component scores-multivariate linear regression (PCA-APCS-MLR) analysis was conducted to reveal the source contributions to heavy metal(loid)s in grains, considering Q values, soil, and wheat grain data. Results showed that contributions of main sources and factors drastically varied with soil sites, and usually overlapped to different extents. For grain Cd and grain Pb, natural soil silicate (0.066/0.104mg/kg) and iron-bearing minerals (- 0.044/ - 0.174mg/kg) contributed to high extents, while metal smelting activities (0.018/0.019mg/kg) and agronomic activities (- 0.017/ - 0.019mg/kg) unexpectedly posed low or moderate contributions. The pH-mediated availability of soil Cd (0.035mg/kg) and the sand-dust weather (0.028mg/kg) also made considerable contributions to grain Cd. For grain As, both natural soil iron-bearing (- 0.048mg/kg) and silicate minerals (- 0.013mg/kg) made negative contributions. The results benefit to the decision-making of pollution remediation of farmland soils in the regional scales.