Effects of Al-Doura Thermal Power Plant Emissions on Soil Quality: A Multivariate Assessment with Long-Term Environmental Projections

Abstract

This study determined the effects of industrial pollution from the Al-Doura Thermal Power Station, south of Baghdad, Iraq, on the physicochemical properties and contamination gradient of adjacent soils. A distance-based sampling design was used across three sites: Site A (high pollution, <100 m), Site B (moderate pollution, 300–500 m), and Site C (control, >800 m). Thirty soil samples collected at two depths (0–10 cm and 10–30 cm) were analysed for pH, electrical conductivity (EC), salinity, organic matter, total petroleum hydrocarbons (TPH), heavy metals (Ni, Pb, Cd, and Zn), and soil temperature. All parameters differed significantly among the sites, with Site A showing the highest values and a progressive decline with increasing distance from the pollution source. One-way analysis of variance confirmed significant between-site differences (p < 0.05), and Tukey’s post-hoc test separated Site A from Sites B and C. Pearson correlation analysis, computed using the full sample-level dataset, showed strong associations between TPH and EC (r = 0.87, p < 0.01), and between soil temperature and Ni (r = 0.75, p < 0.05). Principal component analysis (PCA) identified a primary axis (PC1, 52.8% of the total variance) dominated by TPH, EC, and soil temperature, and a secondary axis (PC2, 23.4%) dominated by heavy metals. A separate controlled biochar-amendment experiment conducted on heavily contaminated soil markedly reduced TPH, EC, and Ni while restoring soil-enzyme activity and crop performance. A conceptual, scenario-based projection suggested accelerated soil degradation and contaminant mobility by 2050, broadly consistent with global estimates indicating 15–17% cropland degradation. These findings provide a multivariate framework for understanding soil degradation under combined industrial and climatic pressures in semi-arid environments.