Abstract:
The characteristics of PM
10 and its chemical composition from December 2015 to December 2017 are studied at three regional atmospheric background stations (Longfengshan, Lin'an, and Jinsha) in central and eastern China. The water-soluble ions (F
-, Cl
-, NO
3-, SO
42-, PO
43-, Na
+, K
+, NH
4+, Ca
2+, Mg
2+), carbon-containing compounds (OC, EC) and main elements in PM
10 samples are analyzed. The average PM
10 concentration at Lin'an (62.2±36.6 μg·m
-3) during the whole period is the highest, followed by Jinsha (57.6±31.8 μg·m
-3), and that at Longfengshan (57.5±55.3 μg·m
-3) is the lowest. At those stations, the annual PM
10 mass concentrations are lower than the national second-level air quality standard. The concentrations of PM
10 in 2016-2017 show a downward trend, with the reductions of concentrations about 29.3% at Lin'an and 26.2% at Jinsha compared with the results during the year of 2013.The concentrations of SO
42-, NO
3-, and NH
4+ during the whole period are 9.9, 8.2 μg·m
-3 and 3.7 μg·m
-3 at Lin'an, and 10.2, 6.7 μg·m
-3 and 2.6 μg·m
-3 at Jinsha, respectively, which are all higher than those at Longfengshan, with the average concentrations of 5.9 μg·m
-3 for SO
42-, 4.9 μg·m
-3 for NO
3-, and 2.1 μg·m
-3 for NH
4+. However, the ratio of NO
3-/SO
42- at Longfengshan and Lin'an are relatively higher. The concentrations of OC and EC during the whole period are 10.1 μg·m
-3 and 2.7 μg·m
-3 at Longfengshan, 6.1 μg·m
-3 and 3.1 μg·m
-3 at Lin'an, and 4.7 μg·m
-3 and 2.3 μg·m
-3 at Jinsha. Compared to the year of 2013, the concentrations of SO
42-, NH
4+ and OC during the whole period decrease by 38.1%, 26.0%, and 55.6% at Lin'an, respectively, and decrease by 46.3%, 51.9%, and 44.7% at Jinsha, while the concentrations of NO
3- increase by 12.3% and 15.5% at Lin'an and Jinsha, respectively. The concentrations of EC decreases by 27.9% at Lin'an, but increases by 4.5% at Jinsha. The ratio of NO
3-/SO
42- increase obviously at all the stations, which indicates the increases of nitrate aerosols, due to the continuously control of coal combustion emissions and increase of car ownership.The seasonal concentrations of PM
10, NO
3-, EC and the ratio of NO
3-/SO
42- are lowest in summer at three stations. Meanwhile, the mass concentrations of SO
42-, NO
3- and NH
4+ are basically higher in winter than in other seasons.