Tree species classification improves the estimation of BVOCs from urban greenspace

Accurate estimation of biogenic volatile organic compounds (BVOCs) emissions from urban plants is important as BVOCs affect the formation of secondary pollutants and human health. However, uncertainties exist for the estimation of BVOCs emissions from urban greenspace due to the lack of tree species classification with high spatial resolution. Here, we generated a tree species classification dataset with 10 m resolution to estimate tree species-level BVOCs emissions and quantify their impact on air quality in Shenzhen in southern China. The results showed that for the entire city, the BVOCs emissions based on traditional plant functional types (PFTs) dataset were substantially underestimated compared with the tree species classification data (6.37 kt versus 8.23 kt, with 22.60 % difference). The underestimation is particularly prominent in urban built-up areas, where our estimation was 1.65 kt, nearly twice of that based on PFTs data (0.86 kt). BVOCs estimation in built-up areas contributed approximately 20.07 % to the total. These BVOCs contributed substantially to the increase of ambient O3, but had limited impacts to ambient fine particulate matter (PM2.5). Our results underscore the importance of high spatial resolution tree species-level classification in more accurate estimation of BVOCs, especially in highly developed urban areas. The enhanced understanding of the patterns of BVOCs emissions by urban trees and the impact on secondary pollutants can better support fine-scale tree planning and management for livable environments in urban areas.