Geochemical Characteristics and Environmental Significance of Heavy Metals in Urban Topsoil from Industrialized Regions of Central China: A Case Study of the Yangtze River Middle Reaches

Abstract:

This study investigates the geochemical characteristics, sources, and environmental risks of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in urban topsoil (0–20 cm) from three industrialized cities (Wuhan, Changsha, Xiangtan) in the Yangtze River Middle Reaches, Central China. A total of 324 topsoil samples were collected across industrial, residential, commercial, and green space areas between 2021–2023. Results show that Cd, Pb, Zn, and Cu concentrations exceed local background values by 2.3–7.8 times, with industrial areas having the highest contamination levels. Multivariate statistical analysis and positive matrix factorization (PMF) identify four primary sources: industrial emissions (38%), traffic activities (27%), agricultural inputs (21%), and natural weathering (14%). Environmental risk assessment indicates moderate to high ecological risk in industrial zones (RI=320–480) and low to moderate risk in residential/commercial areas (RI=120–240). Cd and Hg pose the greatest non-carcinogenic and carcinogenic risks to human health, particularly for children. This study provides critical insights for heavy metal pollution control and soil environmental management in industrialized urban regions.