PM2.5-bound PAHs during a winter haze episode in a typical mining city, central China: Characteristics, influencing parameters, and sources

Abstract

Huangshi City in Hubei Province, Central China is one of the most important mineral cities in the middle reaches of the Yangtze River, where haze occurred frequently in recent years due to coal-based metalsmelting. A haze was observed from January 13 to January 25, 2018 in Huangshi. To understand the levels, compositions, influencing parameters, and sources of PAHs during a process of haze generation and elimination, fine particulate matter (PM2.5) -bound polycyclic aromatic hydrocarbons (PAHs) were high-time-resolution measured (four samples per day) by gas chromatograph-mass spectrometry (GC-MS). The episode divided into three periods including before haze episode (BHE, 10 samples), during haze episode (DHE, 33 samples) and after haze episode (AHE, 4 samples) based on PM2.5 concentration. The average concentrations of Σ15PAHs at three different periods decreased as follows: DHE (30.52 ng m−3) > BHE (29.99 ng m−3) > AHE (14.24 ng m−3). 4- and 5-ring PAHs were the dominant species, and the proportion of 5- and 6-ring PAHs significantly increased DHE probably due to the local emissions (e.g., vehicle emissions) and the poor atmospheric dispersion conditions. PM2.5-bound PAHs were affected by gaseous pollutants (NO2, SO2, O3, and CO) and meteorological parameters (pressure, temperature, wind speed, wind direction, and relative humidity). Results of source apportionment indicated that PM2.5-bound PAHs were similar for three stages of this haze, mainly including vehicle exhaust emission, coal/biomass combustion, industrial process, and coke oven.