Spatial distribution mapping of Hg contamination in subclass agricultural soils using GIS enhanced multiple linear regression

Abstract

Abstract In order to accurately determine the spatial distribution of soil Hg pollution in one agricultural land, 104 topsoil samples were studied by means of three subclass agricultural lands, including vegetable field, paddy field and orchard field in the southeast of China. The method of multiple linear regression modeling combined with the spatial analysis is adopted to recognize the driving factors of soil Hg contamination in each subclass agricultural land. Consequently, corresponding spatial distribution maps of estimated soil Hg concentrations in vegetable field and paddy field are plotted. Results demonstrate greater mean soil Hg concentrations in vegetable field and paddy field over orchard field, but both of them are lower than the maximum permissible concentration in the Chinese Environmental Quality Standard for agricultural soils. In vegetable field, soil Hg concentrations are closely interrelated with chimneys which have the least distances to their around soil samples. In paddy field, both the soil sampling slopes and distances from soil samples to the nearest roads are the dominant driving factors of soil Hg concentration variance. The spatial distribution of soil Hg concentrations reveals several localized hotspots in the north for the vegetable field, while in the paddy field, spreads evenly across the space. These results suggest that while the exhaust emission from industrial chimneys might drive the contamination difference of soil Hg in vegetable field in the study area, surface runoff and traffic contamination from the roads might be other factors causing those spatial variances of soil Hg contamination in paddy field. Quantification of soil Hg concentrations in agricultural lands at subclass level may provide a more accurate basis for taking appropriate prevention and controlling action to protect agricultural soil quality and human health.