THESIS
2023
1 online resource (xi, 66 pages) : color illustrations
Abstract
Volatile organic compounds (VOCs) are important for mitigating the ozone pollution as its major precursors. This study compares VOC characteristics of roadside, suburban and rural sites in Hong Kong based on their compositions, concentrations, and source contributions. Here we show that the sum-up VOC concentrations were 23.05±13.24, 12.68±15.36, 5.16±5.48 ppbv for roadside, suburban and rural site, respectively. Vehicular related species dominated ambient VOCs in the roadside site while the rural site had larger influence from industrial sources than expected. Moreover, a gnificant decreasing trend for VOCs species only existed in roadside site. Obvious seasonal trend was discovered in all three sites over the five years with 0.52 ppbv in winter and 0.11 ppbv in summer as an average, y...[
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Volatile organic compounds (VOCs) are important for mitigating the ozone pollution as its major precursors. This study compares VOC characteristics of roadside, suburban and rural sites in Hong Kong based on their compositions, concentrations, and source contributions. Here we show that the sum-up VOC concentrations were 23.05±13.24, 12.68±15.36, 5.16±5.48 ppbv for roadside, suburban and rural site, respectively. Vehicular related species dominated ambient VOCs in the roadside site while the rural site had larger influence from industrial sources than expected. Moreover, a gnificant decreasing trend for VOCs species only existed in roadside site. Obvious seasonal trend was discovered in all three sites over the five years with 0.52 ppbv in winter and 0.11 ppbv in summer as an average, yet roadside site had a higher concentration in summer as 0.22 ppbv due to the canyon effect. By using PMF model, six sources were resolved for the roadside site, including LPG usage, gasoline evaporation, fuel filling, aged air mass, gasoline exhaust and diesel exhaust. Likewise, six factors were distinguished for suburban site containing LPG usage, biogenic emission, gasoline evaporation, diesel exhaust, solvent usage and aged air mass while four factors for the rural site including solvent usage, biogenic emission, vehicular emission and aged air mass. LPG usage dominated the contribution in the roadside station, followed by aged air mass and gasoline evaporation. The main contributor were LPG usage, solvent usage and diesel exhaust in the suburban site and aged air mass for rural site. Finally, the ozone formation potential and OH loss rates of each source were calculated accordingly. For the roadside site, the major contributor in OFP was fuel filling and LPG usage for the OH reactivity. Yet in suburban and rural site, solvent usage and biogenic emission accounted for almost half in OFP and OH reactivity, respectively. This study revealed the difference in characteristics between archetypal sites, which could help the policymakers to better control the pollution case by case.
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