Important contributions of alkenes and aromatics to VOCs emissions, chemistry and secondary pollutants formation at an industrial site of central eastern China

Volatile organic compounds (VOCs) play important roles in the tropospheric atmosphere. In this study, VOCs were measured at an urban site of Zibo city in September 2018 using an online gas chromatography-time of flight mass spectrometry instrument (GC-TOFMS). Diurnal profile analysis showed that while the removal of most reactive hydrocarbons such as alkanes, small alkenes, and aromatics was governed by OH chemistry, nighttime removal for several highly reactive alkenes by ozone was also significant. The influence of nighttime removal on emission ratio determinations were further explored by parameterization method based on OH radical chemistry/ozone chemistry and comparison of emission ratios with nearby regions. The results revealed that nighttime removal for several alkenes likely leaded to underestimation of emission ratios in previous studies. The emission ratios of aromatics in Zibo were also unexpectedly higher than those at the receptor site in central eastern China. Detailed source analyses of VOCs using a positive matrix factorization (PMF) method suggested important contributions from both petrochemical emission and vehicle exhaust & LPG usage for measured alkenes and dominant contribution from coal combustion for aromatics. Ozone formation potential (OFP) and secondary organic aerosol potential (SOAP) calculation suggested that alkenes were the dominant contributor to OFP (59.4%); while aromatics could produce large amounts of SOA (1.10 +/- 0.88 mu gm(3)) and naphthalene alone dominated (similar to 43.0%) the total SOA estimated from measured VOCs. The results enable improved mitigation strategies and chemical links between direct emissions and SOA/ozone impacts on climate and health in these regions.