Trace element behavior in phosphate materials and environmental impact through INAA
摘要
Instrumental neutron activation analysis (INAA) was used to determine concentrations of 35 chemical elements in phosphorite raw material, ammophos, phosphogypsum, soils, and plants from the Central Kyzylkum region. Measured concentrations ranged from 10−4 to 105 mg/kg. The results show that during ammophos production, several trace elements are preferentially concentrated in the final product: uranium increases from 63 ± 4 to 105 ± 5 mg/kg, thorium from 5.0 ± 0.2 to 6.1 ± 0.2 mg/kg, copper from 33 ± 1 to 42 ± 3 mg/kg, and zinc from 55 ± 4 to 85 ± 3 mg/kg. In phosphogypsum, concentrations of most impurities are substantially lower, indicating selective redistribution along the technological chain. Assessment of soils and plants reveals that elevated concentrations of Cu, Zn, and U occur exclusively near the industrial complex, with enrichment factors reaching 80–100 for Cu. In contrast, agricultural sites with over 40 years of phosphate fertilizer application show concentrations indistinguishable from background, indicating that industrial emissions—rather than fertilizer use—are the primary source of contamination. Statistical analysis of the plant tissue data (Pearson correlation, PCA, and hierarchical cluster analysis) confirmed strong inter-element associations among industrial emission indicators (Cu–As: r = 0.95; Cu–Sb: r = 0.97) and between phosphate-chain tracers (U–Th: r = 0.96, p < 0.01). Principal component analysis (PC1: 65.4%, PC2: 23.6%) clearly separated the FAC industrial site from all other locations, while hierarchical cluster analysis grouped the agricultural sites (GEN, ICF) together, confirming the absence of a fertilizer-specific elemental signature.