Revealing the occurrence characteristics, interaction mechanisms, and health risk of phthalates in agricultural soil of arid regions across Northwest China

Phthalate (PAE) contamination in agricultural soils has attracted global attention. However, the correlation between PAE occurrence and soil properties remains not fully clear, especially in typical arid regions. This study investigated six types of PAE at 19 sites in agricultural soils of arid regions across four Northwest China cities, and the relationship between PAE profiles and soil properties (including pH, total potassium/phosphorus/nitrogen (TK/TP/TN), soil organic matter (SOM), and heavy metals) was explored. Results revealed total PAE concentrations (Σ₆PAEs) ranged from 221.20 to 618.33 μg/kg, and the di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP) dominated Σ₆PAEs, accounting for 75.87% to 83.08%. Regional analysis presented that DBP with TK, dimethyl phthalate (DMP) with SOM, and TP showed significant negative correlations (p ≤ 0.05), indicating that PAEs might influence their own persistence by affecting element cycling and microbial activity during their degradation processes. Although pH showed a consistent positive correlation with DEHP, its correlations with DBP varied regionally, highlighting the complex interactions between pH and PAEs. Multiple heavy metals exhibited significant negative correlations with Σ₆PAEs and DEHP (p ≤ 0.05), which might be attributed to competition between heavy metals and PAEs for adsorption sites on SOM, especially in arid regions with low organic matter conditions. Moreover, health risk assessment indicated that both the carcinogenic (CR < 10⁻⁴) and the non-carcinogenic (HQ < 1) risks were acceptable, but priority attention should be given to children. Overall, these results are expected to provide novel insights into understanding the occurrence characteristics and interaction mechanisms for PAE contamination risk control in arid regions.