Seasonal volatile organic compound dynamics in urban and forest environments in Thailand: Implications for air...

Volatile organic compounds (VOCs) notably influence air quality, climate and secondary pollutant formation, particularly regions in where urban emissions interact with natural biogenic sources at the interface of urban and natural ecosystems. This study examined the VOC profiles in the Sakaerat dry evergreen forest and the urban area of Nakhon Ratchasima, Thailand, throughout 2023, focusing on seasonal and spatial variations in biogenic and anthropogenic VOCs (BVOCs and AVOCs, respectively). Hydrocarbons, mainly alkanes, dominated VOC compositions, contributing 43.74-47.44% of the total detected VOCs in the forest and 44.89-66.35% in urban areas. Aromatic hydrocarbons accounted for 7.63-10.36% in the forest but increased to 11.80-34.56% in urban areas, peaking in winter. BVOCs, such as isoprene and D-limonene, were more prevalent in the forest (4.41-12.67%) than in urban areas (0.75-4.65%). Meanwhile, oxygenated VOCs (OVOCs) displayed considerable seasonal contributions, ranging from 30.24 to 42.62% in the forest to 9.14-16.78% in urban areas. Seasonal trends exhibited elevated BVOC emissions in the forest during the rainy season and higher AVOC levels in urban areas during summer. Negative and positive correlations with relative humidity were observed in the forest and in urban areas, respectively. Diurnal variations revealed that isoprene emissions in the forest increased with rising daytime temperatures, while VOC concentrations in urban areas showed little to no fluctuation throughout the day. Temperature, humidity and atmospheric transport were key drivers shaping VOC dynamics, highlighting distinct patterns of biogenic and anthropogenic emissions. This study highlights the importance of long-term VOC monitoring to evaluate the environmental impacts of urbanisation on natural ecosystems. These findings provide valuable insights to support air quality management and the mitigation of pollution at the interface of urban and natural environments.