Spatial Distribution and Pollution Source Analysis of Heavy Metals in Cultivated Soil in Ningxia

This study collected 820 topsoil samples from cultivated lands across Ningxia, covering the Yellow River irrigation area, the central arid zone, and the southern mountainous region. The concentrations of Arsenic (As), mercury (Hg), cadmium (Cd), chromium (Cr), and lead (Pb) were analyzed to evaluate the pollution levels and spatial distribution patterns of heavy metals, which were interpolated using Kriging. Pollution status was assessed via the Nemerow composite index and the geoaccumulation index (Igeo). Source identification and contribution quantification were performed using Pearson correlation analysis, principal component analysis (PCA), and positive matrix factorization (PMF). Results indicated that the cultivated soils in Ningxia are generally clean, with isolated instances of warning and light pollution. Ecological risk assessment revealed differential risk levels among elements, with Hg and Cd presenting the highest ecological risks. Geospatially, regions with higher pollution probabilities for Cd, Cr, Pb, Hg, and As were concentrated in the northern and central parts of Ningxia, whereas the southern region exhibited lower pollution probabilities.pH significantly influences the accumulation and spatial distribution of heavy metals in soil. Source apportionment identified three primary contributors: transportation and natural parent materials (As, Pb, Cr), industrial activities (Hg), and agricultural practices (Cd). Hg and Cd were identified as the key risk elements requiring prioritized management.