Shen Zhenxing, Arimoto Richard, Cao Junji, Zhang Renjian, Li Xuxiang, Du Na, Okuda Tomoaki, Nakao Shunsuke, Tanaka Shigeru
Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an, People's Republic of China.
J Air Waste Manag Assoc. 2008 Dec;58(12):1560-70. doi: 10.3155/1047-3289.58.12.1560.
Total suspended particulate (TSP) and particulate matter less than 2.5 microm in aerodynamic diameter (PM2.5) samples were collected over Xi'an for a 1-yr period to characterize the seasonal variations of water-soluble inorganic ions and to evaluate the effectiveness of the pollution policies and controls during the past 10 yr. Mass concentrations of five cations (sodium [Na+], potassium [K+], ammonium [NH4+], calcium [Ca2+], and magnesium [Mg2+]) and four anions (fluoride [F-], chloride [Cl-], nitrate [NO3-], and sulfate [SO4(2-)]) were determined by ion chromatography. The yearly arithmetic-mean mass concentrations of the total measured water-soluble ions in TSP and PM2.5 were 83.9 +/- 58.4 and 45 +/- 34.3 microg x m(-3). The most abundant ions in TSP were SO4(2-), NO3-, Ca2+, and NH4+; whereas in PM2.5 the dominant ions were SO4(2-), NH4 +, and NO3-. Most of the ions were more concentrated in the PM2.5 than in TSP, but two exceptions were Ca2+ and Mg2+. Comparisons of the molar ratios of Mg2+/Ca2+ in TSP indicated that fugitive dust was the main source for these two ions, and the influence of soil dust from outside of the city was most evident during dust storms. The mass concentrations of SO4(2-), NO3-, , NH4+, and K+ in TSP were highest in winter and lowest in spring, but Ca2+ was much higher in spring than other seasons because of suspended mineral dust. In PM2.5, NO3- and K+ also showed winter maxima, but SO4(2-) and NH4+ were highest in summer. Calculations of ion equivalents showed that TSP samples were more alkaline than PM2.5, the latter being weakly acidic in winter and autumn. High sulfur and nitrogen oxidation ratios occurred in summer and autumn, and there was evidence for the formation of ammonium bisulfate in TSP, ammonium sulfate in PM2.5, and ammonium nitrate in both fractions. Comparisons with the results of prior studies indicate that pollution controls in Xi'an have reduced the levels of air pollution over the past 10 yr. The SO4(2-) concentration during the heating season in 2006 was only about one-eighth of that in 1996, and NH4+ decreased to one-ninth of that in 1996. Seasonal variations in the NO3-/SO4(2-) ratio are different than the patterns observed 10 yr ago, suggesting that emission sources have changed, with those from motor vehicles becoming increasingly important.
在西安采集了为期1年的总悬浮颗粒物（TSP）和空气动力学直径小于2.5微米的颗粒物（PM2.5）样本，以表征水溶性无机离子的季节变化，并评估过去10年污染政策和控制措施的有效性。通过离子色谱法测定了5种阳离子（钠[Na⁺]、钾[K⁺]、铵[NH₄⁺]、钙[Ca²⁺]和镁[Mg²⁺]）和4种阴离子（氟化物[F⁻]、氯化物[Cl⁻]、硝酸盐[NO₃⁻]和硫酸盐[SO₄²⁻]）的质量浓度。TSP和PM2.5中测得的总水溶性离子的年算术平均质量浓度分别为83.9±58.4和45±34.3微克·米⁻³。TSP中含量最高的离子是SO₄²⁻、NO₃⁻、Ca²⁺和NH₄⁺；而PM2.5中的主要离子是SO₄²⁻、NH₄⁺和NO₃⁻。大多数离子在PM2.5中的浓度高于TSP，但Ca²⁺和Mg²⁺是两个例外。TSP中Mg²⁺/Ca²⁺摩尔比的比较表明，扬尘是这两种离子的主要来源，在沙尘暴期间，城外土壤扬尘的影响最为明显。TSP中SO₄²⁻、NO₃⁻、NH₄⁺和K⁺的质量浓度在冬季最高，春季最低，但由于悬浮矿物粉尘，Ca²⁺在春季比其他季节高得多。在PM2.5中，NO₃⁻和K⁺也在冬季出现最大值，但SO₄²⁻和NH₄⁺在夏季最高。离子当量的计算表明，TSP样本比PM2.5碱性更强，后者在冬季和秋季呈弱酸性。高硫和氮氧化率出现在夏季和秋季，有证据表明在TSP中形成了硫酸氢铵，在PM2.5中形成了硫酸铵，在两个组分中都形成了硝酸铵。与先前研究结果的比较表明，西安的污染控制措施在过去10年中降低了空气污染水平。2006年供暖季节的SO₄²⁻浓度仅约为1996年的八分之一，NH₄⁺降至1996年的九分之一。NO₃⁻/SO₄²⁻比值的季节变化与10年前观察到的模式不同，这表明排放源发生了变化，机动车排放源变得越来越重要。
