Exploring the Spatial Distribution and Sources of OVOCs in Shenzhen Using an Optimized Source Apportionment Method

Oxygenated volatile organic compounds (OVOCs) are key precursors to atmospheric ozone (O3) and secondary organic aerosols (SOA). However, research on the sources of OVOCs is still limited, particularly in terms of multi-point observations at urban sites. This study conducted a one month continuous enhanced observation at an urban site (BA) and a suburban site (DP) in December 2024. During the study period, the average total VOCs concentration at the BA site was 29.9 ± 6.5 ppbv, significantly higher than that at the DP site (6.4 ± 1.3 ppbv). To enhance the representation of the biogenic fraction in OVOCs, isoprene was employed as a biogenic tracer; prior to source apportionment, its anthropogenic components were subtracted based on local emission ratio coefficients, thereby providing a more representative basis for biogenic source attribution. The optimized source apportionment results show that the contribution ratio of biogenic sources had decreased significantly, with a particularly noticeable decline at the urban site. Among these, the contribution rates of acetaldehyde and acetone had decreased significantly: by 14.7% and 12.2%, respectively. Based on the improved source apportionment method, the source apportionment of OVOCs at the urban site showed that methanol, acetone, and MEK were primarily dominated by anthropogenic primary sources (accounting for 44.5% to 68.5%), while acetaldehyde was primarily dominated by secondary anthropogenic generation (37.1%), indicating its key role as a photochemical product. In contrast, at the suburban site, the biogenic source contribution to acetaldehyde (37.8%) was significant. This difference highlights the necessity of optimizing biogenic source tracers and conducting OVOC source apportionment studies at multiple locations.