Environ Int. 2026 May 15;212:110306. doi: 10.1016/j.envint.2026.110306. Online ahead of print.
ABSTRACT
p-Phenylenediamines (PPDs) are widely used as antioxidants in tire formulations and are released to the environment via tire wear, where they can be transformed into more toxic p-phenylenediamine-derived quinones (PPD-Qs). Despite growing recognition of their environmental importance, information on the occurrence and behavior of these compounds in farmland soils remains limited. In this study, 122 surface soil samples were collected from agricultural regions across China to quantify six PPDs and five PPD-Qs and to examine their spatial patterns, sources, transformation drivers, and potential risks. The PPD and PPD-Q compounds were detected in all samples, with national mean concentrations of 1.02 and 0.28 ng/g, respectively. Spatially, the ΣPPD concentrations were 0.19‒4.93 ng/g in southern China and 0.13‒4.13 ng/g in northern China, while the ΣPPD-Q concentrations were 0.06‒1.37 ng/g in southern China and 0.03‒1.48 ng/g in northern China. 6PPD and 6PPD-Q were the dominant congeners, indicating strong inheritance from parent compounds to transformation products. Source apportionment implicates both direct inputs from agricultural rubber materials and indirect inputs via atmospheric transport of industrial rubber-derived emissions. Conventional statistical approaches together with non-linear dependence analyses identified sunshine duration and soil total organic carbon (TOC) as key factors influencing their composition and transformation. Risk assessment showed that current non-carcinogenic human and ecological risks were within acceptable limits. These findings advance understanding of the environmental occurrence and transformation of PPDs and PPD-Qs in agricultural soils and highlight key factors relevant to their management and risk control.
PMID:42172717 | DOI:10.1016/j.envint.2026.110306
