Nationwide Occurrence of Multiple Classes of Emerging Vulcanization Accelerators in Municipal Sludge from 30 Provincial-Level Regions across China

Abstract

Vulcanization accelerators (VAs) are additive chemicals used in synthetic rubber, yet knowledge of their occurrence in municipal sludge on a large geographical scale remains lacking. Here, we implemented the first nationwide survey of eight classes of VAs in municipal sludge from 30 provincial-level regions across China. All eight classes of VAs were detected, with thiazoles, guanidines, and xanthates identified as the predominant groups, followed by thiurams, dithiocarbamates, thioureas, sulfenamides, and others. A total of 42 out of 44 target VAs were detected, with 32 being newly identified and 20 exhibiting a detection frequency exceeding 60%. The total concentrations of all detectable VAs (∑VAs) in the nationwide sludge samples ranged from 333 to 8040 ng/g, with a median value at 799 ng/g. A clear geographical distribution trend was observed, with significantly higher levels of ∑VAs in East China than Central and West China (p < 0.05). The national annual emission flux of ∑VAs into sludge in China is estimated at 21.7 tons/year, with 3.47 tons/year being directly released into sludge-amended farmland soils. Our study comprehensively revealed nationwide occurrence and prevalence of multiple classes of VAs in Chinese municipal sludge, highlighting the emerging concern on these new pollutants.