Distribution of PM2.5 and Gaseous Species in Central Taiwan During two Chinese Festival Periods

Abstract

Measurements of PM2.5 and acidic gases were conducted at an inland site of Taichung basin. The sampling site was Nantou, which is located at a distance of 25 km from the Taichung city. Nantou represents an inland area surrounded by Central Mountain Ranges and Baqua Hill. The sampling timings were in the month of April (during Tomb-Sweeping Festival) and in September (during Mid-Autumn Festival). PM2.5 samples were collected with an annular denuder system. Aerosol ionic species including sulfate (SO42−), nitrate (NO3−), ammonium (NH4+), chloride (Cl−), calcium (Ca2+), potassium (K+), and sodium (Na+) and gaseous nitric acid (HNO3), hydrochloric (HCl), and sulfur dioxide (SO2) were analyzed. Results showed that the average PM2.5 concentration were 41.3 μg m−3 during the Tomb-Sweeping Festival period and 65.3 μg m−3 during the Mid-Autumn Festival period. The major particle-phase ionic species was sulfate (SO42−) during both the Chinese Festival periods. Ozone concentration was higher during the Mid-Autumn Festival. Sulfate (SO42−) and nitrate (NO3−) concentrations were well correlated with daily maximum ozone (O3) concentration. The time weight mean concentration data showed that the increased concentration of gas-phase sulfur dioxide (SO2) and sulfate (SO42−) were transported from Taichung City, which is located close to the sampling site. Based on our above obtained results, the Mid-Autumn Festival period showed more anthropogenic impact on the aerosol and gaseous distribution favored by meteorological factors, higher ambient temperature, and wind direction.