Characteristics of Atmospheric BTX near a Main Road in Hefei City

Abstract

In order to study levels of BTX near a main road in Hefei in March 2016, benzene, toluene, m-xylene, and o-xylene (BTX) and conventional pollutants (such as NO2 and SO2) in the atmosphere were monitored through a home-made differential optical absorption spectroscopy (DOAS) system. Results showed that average concentrations of benzene, toluene, m-xylene, and o-xylene were 21.7, 63.6, 33.9, and 98.7 μg·m-3, respectively. Compared with other cities both in China and elsewhere, benzene and toluene pollution can be considered to be of medium level, while xylene pollution is serious. Wind direction, T/B ratio, and correlation with CO were also analyzed, together with BTX sources. Result showed that the T/B ratio was 0.8-4.5, with correlation coefficients of benzene, toluene, and CO of 0.55 and 0.34, respectively. These values indicate that benzene and toluene are mainly derived from automotive emissions, also affected by surrounding industrial parks. Xylene is mainly derived from a coating industrial park north of the observation site. It was shown that high night-time concentrations of benzene and toulene could be due to industrial emissions from the industrial parks around the observation site. The ozone formation potential is in the order of o-xylene > m-xylene > toulene > benzene at the observation site. The ozone formation potential of xylene accounted for 85% of total ozone formation potential, indicating that emissions from surrounding industrial parks contribute greatly to ozone formation in the area.