Abstract
VOCs have been one of the important limiting factors of O3 photochemical production in the urban tropical region. This study aims to determine the variation and composition of aromatic VOCs as well as their contribution to the O3 formation. The hourly data of benzene, toluene, ethylbenzene and xylenes (BTEX) and ozone (O3) were retrieved from January until December 2019 at three continuous air quality monitoring stations (S1, S2 and S3) operated by the Malaysian Department of Environment (DOE). Aromatic VOCs is detected by using an online gas chromatography analyser (GC 5000BTX). The annual average ΣBTEX concentrations ranged from 14.53 ± 12.43 μg m-3 to 25.04 ± 24.04 μg m-3 during the observation period, with toluene as the most dominant species with an average concentration of 10.65 ± 12.12 μg m-3. The O3 formation potential (OFP) was calculated and the results indicated that toluene is the highest contributor of O3-forming potential, followed by m, p-xylene, o-xylene, ethylbenzene and benzene with the value of 127.8 μg m-3 (40.90 %), 103.0 μg m-3 (32.97 %), 48.66 μg m-3 (15.58 %), 26.17 μg m-3 (8.38 %) and 6.74 μg m-3 (2.15 %), respectively. Since the study of VOCs in Malaysia is quite limited, a more comprehensive study is currently underway to integrate the research on variation of VOCs in ambient air and its impact on the environment and human health.
Highlights
Volatile organic compounds (VOCs) have been one of the important limiting factors of ozone (O3) photochemical production in the urban tropical region
A previous study in India demonstrated that the average concentration of BTEX was between 186 ± 107 μg m-3 and 456 ± 224 μg m-3, with toluene accounting for 42-50 % and benzene accounting for 26-30 % of the total BTEX [24]
Other similar findings by Cruz et al [25] stated that toluene was the most abundant species amongst the BTEX compounds with the average level ranging from 2.47 ± 1.49 μg m-3 to 3.18 ± 0.97 μg m-3 in the tropical urban area of Brazil
Summary
Volatile organic compounds (VOCs) have been one of the important limiting factors of ozone (O3) photochemical production in the urban tropical region. Considerable efforts have been expended in recent times to understand the tropospheric O3 formation mechanism, which is usually produced from photochemical reactions involving VOCs with various atmospheric radicals (i.e., OH radicals, HO2 radicals, etc.) [1,2,3,4]. Anthropogenic VOCs, generally referred to as aromatic hydrocarbons, are the most frequently measured by previous studies. Aromatic VOC, benzene, toluene, ethylbenzene and xylenes (BTEX) partitions is of great concern as it may cause a detrimental impact on human health [8,9,10,11]. According to Ran et al [13], atmospheric VOCs may exacerbate both respiratory and cardiovascular disease, congestive heart failure (CHF) and chronic obstructive pulmonary disease (COPD)
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