Process-resolved VOC profile and compound-specific APCD performance in rubber manufacturing: Implications for ozone...

Volatile organic compounds (VOCs) are critical precursors of secondary air pollution and pose substantial occupational health threats. This study established an integrated analytical framework to characterize VOCs at a large rubber manufacturing plant in central China, covering unorganized fugitive emissions and organized stack emissions at the inlet and outlet of air pollution control devices (APCDs). Total VOC concentrations (TVOC), chemical profiles, ozone formation potential (OFP), and health risks of hazardous air pollutants (HAPs) were quantified together with compound-specific APCD removal efficiencies. Results showed strong process-dependent emission characteristics. Total VOC (TVOC) concentrations at stack outlets reached 27225 ± 1997 μg/m³ and 13323 ± 1626 μg/m³ for rubber refining and vulcanization, respectively. Alkanes dominated fugitive emissions, whereas halocarbons (50-61%) were dominant in stack emissions, with methylene chloride as the most abundant species. Both processes contributed significantly to regional ozone formation, with aromatics accounting for 37-49% of total OFP. Notably, the vulcanization APCD achieved a much higher VOC removal efficiency (73%) than the refining unit (36%). However, current APCDs exhibited strongly selective removal performance: poor or inefficient removal for high-risk species in rubber refining, and unstable styrene removal in vulcanization. Health risk assessment revealed an obvious spatial gradient in HAP concentrations (stack inlet > stack outlet > plant area > operating area), with extreme carcinogenic and non-carcinogenic risks identified at the stack outlets. This study identifies key limitations of existing end-of-pipe control technologies and supports the development of targeted, cleaner production strategies for the rubber industry.