Spatial distribution and source apportionment of heavy metal(loid)s in urban topsoil in Mianyang, Southwest China

Abstract

Spatial distributions and sources of some commonly concerned heavy metal(loid)s (HMs, As, Ba, Cr, Co, Cu, Ni, Pb, Mn, Zn, and V) in topsoil of Mianyang city, a typical medium-sized emerging industrial city in Southwest China, were determined to explore the influences of anthropogenic activities on the urban environment. The contents of the 10 HMs in 101 topsoil samples were analyzed using an X-ray fluorescence spectrometer, and their sources were analyzed by positive matrix factorization and statistical analysis. The spatial distributions of the HMs and the source contributions were mapped using GIS technology. The results showed that the mean contents of Ba, Cr, Cu, and Zn in the topsoil were significantly higher than their background values. Industrial activities resulted in high contents of Ba, Zn, Cu, and Cr. As, Co, Ni, and V that primarily came from natural sources; Pb, Cr, Cu, and Zn were chiefly derived from a mixed source of industry and traffic; and Ba and Mn primarily originated from industrial sources. Natural sources, mixed sources, and industrial sources contributed 32.6%, 34.4%, and 33.0% of the total HM contents, respectively. Industrial sources and mixed sources of industry and traffic were the main anthropogenic sources of HMs in the urban topsoil and should be the focus of pollution control.

Contamination and Probabilistic Ecological–Health Risk of Heavy Metal(loid)s in Urban Topsoil of Mianyang, SW China

“…The gross domestic product of Mianyang reached CNY 1592 billion in 2020, and there was an excess of 1.01 × 10 6 motor vehicles in Mianyang urban area in 2020 [ 24 ]. With the rapid expansion of built-up areas in Mianyang, the city has gradually become a major area for education, residence, commerce, and industry [ 20 ]. The eastern part of the urban region is an industrial zone, the region close to the river junction is the historic center district with intensive residential and commercial activities, the northwest is a science and technology industrial zone, the western part is a high-tech industrial zone, and the central part is an educational and residential zone [ 20 ].…”

“…A 5 g milled soil sample and a plastic ring with an inner diameter of 34 mm were put into the mold. The tablet was pressed using the tablet press under 30-ton pressure, and then the concentrations of 10 HMs (Ba, As, Cr, Co, Pb, Mn, Cu, Ni, Zn, and V) were determined via X-ray fluorescence spectrometer (XRF, Bruker, S8 Tiger, Germany) [ 20 , 28 ]. The standard sample (GSS-2) and 10% repeated samples were used for quality control.…”

“…Their industrial productions are characterized by high-value-added products. Industrial activities not only increase the consumption of energy resources but also continuously generate industrial waste in the production process, which is not conducive to the healthy development of urban environments [ 20 ]. In particular, the use of HMs and chemical materials in the production of electronics, automobiles, and mechanical products leads them to enter the soil directly or indirectly during production, recovery, and treatment, which may cause HM pollution in urban topsoil [ 21 ].…”

“…As an emerging industrialized city and an important node city for the comprehensive development of the Chengdu–Chongqing urban agglomeration [ 22 ], Mianyang City has formed a new industrial economic system with medicine, electronics, the chemical industry, machinery, new energies, and automobile manufacturing as the main components in recent years with the acceleration of urbanization [ 22 ]. At the same time, it has also brought great challenges to environmental protection [ 20 ]. The results of spatial distribution and source apportionment indicate that local industrial production and traffic emissions caused the spatial heterogeneity of HMs in the urban topsoil of Mianyang [ 20 ].…”

“…At the same time, it has also brought great challenges to environmental protection [ 20 ]. The results of spatial distribution and source apportionment indicate that local industrial production and traffic emissions caused the spatial heterogeneity of HMs in the urban topsoil of Mianyang [ 20 ]. However, the pollution levels and ecological–health risks of HMs in the urban topsoil of Mianyang are still unclear.…”