PTR-QMS observation of OVOCs in an urban suburb of Guangzhou: seasonal characterization, source apportionment and regional transport

Abstract

Understanding pollution, source and effect of oxygenated volatile organic compounds (OVOCs) is crucial for improving air quality in urban suburbs. This study utilized a proton-transfer-reaction quadrupole mass spectrometer to investigate OVOC pollution characteristics and environmental impacts across four seasons (2022–2023) in an urban suburb of Guangzhou. Results showed that OVOCs dominated total VOCs (averaging 75.4 %), with methanol, acetone, formaldehyde, and carboxylic acids as predominant species. These compounds significantly contributed to ozone formation potential (40.6 %–60.3 %) and OH reactivity. OVOC concentrations exhibited a distinct seasonal pattern (spring > autumn > winter > summer), influenced by photochemical processes and regional transport. Diurnal variations indicated that methanol peaked in the morning and evening linked to primary emissions, while aldehydes and ketones peaked in the afternoon due to secondary formation. Carboxylic acids displayed complex multi-peak patterns with significant nighttime accumulation, correlating with PM_2.5 and suggesting a key role in secondary organic aerosol formation. Photochemical age-based source apportionment revealed diverse contributions: primary emissions were crucial for methanol, methyl ethyl ketone, and acetic acid; secondary formation was important for acetaldehyde, methyl ethyl ketone, and acetic acid; biogenic emissions contributed to formic acid, acetaldehyde, acrolein, and acetone; and background sources impacted methanol in colder seasons. Trajectory clustering and potential source contribution function analyses identified seasonally modulated transport patterns influencing the source areas of OVOCs, PM_2.5 and O₃. The study highlights OVOCs as key drivers of O₃ and SOA formation in urban suburb, while effective mitigation of photochemical pollution in such area requires a multi-faceted control strategy that not only targets local primary precursors (e.g., from traffic and solvents) but also incorporates regionally coordinated efforts to address seasonally varying transboundary pollution.