VOC characteristics and source apportionment at a PAMS site near an industrial complex in central Taiwan

Abstract

Hourly data of volatile organic compounds (VOCs) were collected for three consecutive years from photochemical assessment monitoring stations (PAMS) in Taixi, Taiwan. Analysis of the VOC data allows for apportionment of the anthropogenic sources of VOCs. The VOC concentrations and characteristics were analyzed for temporal variations over a three-year period 2014 to 2016. Out of 54 VOCs detected, 21 VOC compounds from 55 to 99% were below the method detection level; others ranged from 100% occurrence (ethane) to 56–61% for trimethylbenzene. In order to have meaningful statistical results, this paper only used results from 33 VOCs where they were detected at least 65% of the time. This was a requirement to be able to determine statistical parameters such as means and standard deviations. The highest VOC average concentrations observed for three consecutive years, in order, for the period were toluene (3.7–4.3 μg m−3), then propane (2.5–2.6 μg m−3), ethane (2.2–2.5 μg m−3), ethylene (1.1–1.5 μg m−3) and propylene (0.8–1.1 μg m−3). A positive matrix factorization (PMF) receptor model was used to evaluate VOC sources in the area. Six factors were identified by PMF analysis, including solvent use, vehicle exhaust, diesel exhaust, petrochemical, refinery and aged air mass. The conditional probability function indicates that the VOCs in six factors were emitted from their source locations via different wind directions. The contribution of the northwest industrial complex to the PAMS data is linked to the VOCs observed. Actually, seasonal wind directions having only north and north-northwest directions played an important role.