水溶性离子是PM(2.5)和PM(10)中的重要组分,其在大气中的直接和间接辐射能够对全球气候变化产生十分重要的影响.于2013年夏季采集黄海渤海上空大气PM(2.5)和PM(10)样品,采用离子色谱法分析其中主要水溶性离子(Cl^-、NO3^-、SO4^2-、Na^+、K^+、NH4^+、Mg^2+和Ca^2+)及痕量有机酸离子〔CH3SO3-(MSA)、CH3COO-和HCOO-〕浓度,研究其化学特性及主要来源.结果表明:PM(2.5)和PM(10)中主要水溶性离子总质量浓度分别为21.16-25.07和24.14-29.45μg/m^3,平均值分别为(23.16±3.16)和(26.83±4.22)μg/m3,PM(2.5)和PM(10)中二次离子〔nss-SO42-(非海盐硫酸盐)、NO3-和NH4^+〕的质量浓度较高,对总离子质量浓度的贡献分别为90.65%和79.87%.PM(2.5)和PM(10)中酸性离子与碱性离子当量浓度基本中和,呈现中性.气溶胶中nss-SO42-/NO3-(质量浓度比)有一定下降趋势,表明近年来我国燃煤SO2排放得到了一定控制.此外,ρ(MSA)、ρ(CH3COO^-)和ρ(HCOO^-)在PM(2.5)中的平均值分别为(0.006 2±0.002 3)(0.005 2±0.002 4)(0.000 9±0.000 3)μg/m~3,而在PM(10)中分别为(0.008 3±0.002 5)(0.008 5±0.002 4)和(0.001 3±0.000 5)μg/m3,并且ρ(MSA)、ρ(CH3COO^-)、ρ(HCOO^-)与ρ(NO3^-)的线性关系较好,表明有机酸离子的浓度变化受人类活动影响较为显著.
Water-soluble ions are important constituents of PM(2.5)and PM(10),which play an important role in global climate change through their direct and indirect radiative forcing. A series of PM(2.5)and PM(10) samples were collected over the Yellow Sea and the Bohai Sea in summer 2013. The distributions and sources of the main water-soluble ions( Cl^-,NO^3-,SO4^2-,Na^+,K^+,NH^4+,Mg^2 +and Ca^2 +) and organic acid ions( CH3SO3-( MSA),CH3COO^-and HCOO^-) in the samples were analyzed by ion chromatography. The concentrations of the total water-soluble ions ranged from 21. 16 to 25. 07 μg/m3in PM(2.5)and from 24. 14 to 29. 45 μg/m3in PM(10),with the average values of( 23. 16 ±3. 16) and( 26. 83 ± 4. 22) μg/m3respectively. The concentrations of the secondary ions( nss-SO42-,NO3-and NH4+) were extremely high,accounting for 90. 65% and 79. 87% of the total determined ions in PM(2.5)and PM(10),respectively. The calculated results of equivalent concentrations of anions and cations indicated that acid and alkaline compositions were neutralized completely. The ratio of nssSO42-/NO3-decreased greatly in recent years,due to the decrease of SO2 from coal combustion. The average concentrations of MSA,CH3COO^-and HCOO-were( 0. 0062 ± 0. 0023)( 0. 0052 ± 0. 0024) and( 0. 0009 ± 0. 0003) μg/m3in PM(2.5),and were( 0. 0083 ±0. 0025)( 0. 0085 ± 0. 0024) and( 0. 0013 ± 0. 0005) μg/m3in PM(10),respectively. In addition, the concentrations of MSA,CH3COO^-and HCOO-correlated well with NO3-in the samples,exhibiting the effect of human activities on the concentration changes of organic acid ions.