Distribution Characteristics Of Water-soluble Inorganic Ions In Atmospheric Aerosols And Source Apportionment Of Aerosols In Qingdao Coastal Region

The atmospheric aerosols samples were collected in Qingdao coastal region fromMarch to November2011. The average mass concentration of total suspendedparticulate（TSP） was226.93μg/m³. NO₃^-, SO₄^2-and NH4⁺were the dominant ions,accounting for78.9%of total water soluble inorganic ions. The TSP concentrations indifferent weather conditions were in the order of dust> fog/haze> sunny> rainy days.The mass concentration of total water-soluble inorganic ions in fog and haze days washigher than those in any other weather conditions, and the concentration of secondaryions had the highest level. The concentration of SO₄^2-increased to a great extent infog days, while NO₃^-in haze days. The ratio of NO₃^-/SO₄^2-decreased in fog days andincreased in haze days. The concentrations of Ca2+, Mg2+, Na⁺and Cl^-reached thehighest in dust days. The concentrations of Ca2+, K⁺and F^-were the lowest after wetdeposition and Ca2+had the highest decline.Na⁺, Mg2+, Ca2+, F^-and Cl^-mainly existed in the coarse particles （>2.1μm） whileNH4⁺, K⁺, NO₃^-and SO₄^2-in the fine mode. The size distributions of Na⁺, Cl^-and F^-were bimodal with a minor peak at0.43⁰.65μm and a major one at3.3⁴.7μm. Ca2+and Mg2+exhibited unimodal distribution, peaking at3.3⁷.0μm. K⁺and NH4⁺had apeak at0.43¹.1μm in size distribution. SO₄^2-had a unimodal distribution with apeak at0.65¹.1μm. NO₃^-had a bimodal distributions with a major peak at0.43¹.1μm and a minor one at3.3⁴.7μm.In fog/haze days, the peak of secondary ions moved to a large size of dropletmode （0.65².1μm）. And the percentage of secondary ions in total ions concentrationof fine particles increased higher than that in coarse particles. The peak of Na⁺incoarse particles increased higher than that in fine particles. The concentration of K⁺at0.65¹.1μm and1.1².1μm increased higher than other sizes, while the peak of Mg²⁺and Ca²⁺at3.3⁷.0μm decreased. In dust days, the major peak of NO₃^-changedto3.3⁴.7μm. The concentrations of Cl^-, Ca²⁺, Mg²⁺, Na⁺, K⁺, F^-at3.3⁴.7μmremarkably increased. Compared with sunny days, the proportion of ionsconcentrations distributed in coarse particles increased, and NO₃^-increased thehighest, followed by Ca²⁺and Cl^-. The concentrations of SO₄^2-and NH4⁺in fineparticles increased larger than in coarse mode. After wet deposition, theconcentrations of ions at different size ranges decreased except for SO₄^2-and NH4⁺.Among all the ions, concentration of Ca²⁺reduced the maximum.The positive matrix factorization （PMF） receptor model was used to identify thesources of dust and non-dust aerosols in Qingdao. The contributed sources in dustdays were soil dust, coal combustion, vehicle exhaust, biomass burning and industry.In contrast, the sources in non-dust days were soil dust, oil combustion, vehicleexhaust, biomass burning, industry and sea salt. The results showed that the majorsource of both dust and non-dust aerosols was soil dust. The contribution of soil dustwas dramatically increased in dust days, while the contributions of localanthropogenic sources decreased. Pollutants of coal combustion in dust days weremainly from the mixture of soil dust and pollutants along the transmission path, whilebiomass burning pollutants from both local emission and dust long-rangetransportation.PMF was used to identify the sources of particulate matter over the NorthernYellow Sea. The identified six factors were secondary aerosols （sulfate and nitrate）,soil dust, biomass burning, oil combustion, sea salt, and metal smelting. Secondaryaerosol formation contributed the most to the atmospheric particle content, followedby soil dust. The results also suggested that the aerosols over the North Yellow Seawere heavily influenced by ship emission over the local sea area and continentalagricultural activities in the northern China. The contribution of each factor variedgreatly over the different seasons. In spring and autumn, soil dust and biomassburning were the dominant factors. In summer, heavy oil combustion contributed themost among these factors. In winter, secondary aerosols were major sources. Backward trajectories analysis indicated the66%of air mass in summer was from theocean, while the air mass is mainly from the continent in other seasons.