School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.
Environ Monit Assess. 2013 Mar;185(3):2795-805. doi: 10.1007/s10661-012-2749-z. Epub 2012 Jun 29.
Atmospheric condensate (AC) and rainwater samples were collected during 2010-2011 winter season from Delhi and characterized for major cations and anions. The observed order of abundance of cations and anions in AC samples was NH (4) (+) > Ca(2+) > Na(+) > K(+) > Mg(2+) and HCO (3) (-) > SO (4) (2-) > Cl(-) > NO (2) (-) > NO (3) (-) > F(-), respectively. All samples were alkaline in nature and Σ (cation)/Σ (anion) ratio was found to be close to one. NH (4) (+) emissions followed by Ca(2+) and Mg(2+) were largely responsible for neutralization of acidity caused by high NO( x ) and SO(2) emissions from vehicles and thermal power plants in the region. Interestingly, AC samples show low nitrate content compared with its precursor nitrite, which is commonly reversed in case of rainwater. It could be due to (1) slow light-mediated oxidation of HONO; (2) larger emission of NO(2) and temperature inversion conditions entrapping them; and (3) formation and dissociation of ammonium nitrite, which seems to be possible as both carry close correlation in our data set. Principal component analysis indicated three factors (marine mixed with biomass burning, anthropogenic and terrestrial, and carbonates) for all ionic species. Significantly higher sulfate/nitrate ratio indicates greater anthropogenic contributions in AC samples compared with rainwater. Compared with rainwater, AC samples show higher abundance of all ionic species except SO(4), NO(3), and Ca suggesting inclusion of these ions by wash out process during rain events. Ionic composition and related variations in AC and rainwater samples indicate that two represent different processes in time and space coordinates. AC represents the near-surface interaction whereas rainwater chemistry is indicative of regional patterns. AC could be a suitable way to understand atmospheric water interactions with gas and solid particle species in the lower atmosphere.
大气凝结物（AC）和雨水样本于 2010-2011 年冬季从德里采集，并对主要阳离子和阴离子进行了表征。在 AC 样本中，阳离子和阴离子的丰度顺序为 NH(4)(+)>Ca(2+)>Na(+)>K(+)>Mg(2+)和 HCO(3)(-)>SO(4)(2-)>Cl(-)>NO(2)(-)>NO(3)(-)>F(-)。所有样本均呈碱性，Σ(阳离子)/Σ(阴离子)比值接近 1。NH(4)(+)的排放以及随后的 Ca(2+)和 Mg(2+)的排放，主要负责中和该地区车辆和火力发电厂高排放的 NO(x)和 SO(2)造成的酸性。有趣的是，与通常在雨水情况下相反，AC 样本中的硝酸盐含量较低，而其前体亚硝酸盐含量较高。这可能是由于 (1) 光介导的 HONO 缓慢氧化；(2) 更多的 NO(2)排放和温度逆温条件导致其被捕获；以及 (3) 铵亚硝酸的形成和分解，这在我们的数据集中似乎是可能的，因为两者相关性很高。主成分分析表明，所有离子种类都有三个因素（海洋混合生物质燃烧、人为和陆地以及碳酸盐）。硫酸盐/硝酸盐比值显著升高表明 AC 样本中人为因素的贡献大于雨水。与雨水相比，AC 样本中的所有离子种类（除 SO(4)、NO(3)和 Ca 外）含量均较高，表明在雨水事件中通过冲刷过程包含了这些离子。AC 和雨水样本中的离子组成及相关变化表明，两者代表了不同时间和空间坐标的过程。AC 代表近地表相互作用，而雨水化学则代表区域模式。AC 可能是理解大气水与低层大气中气体和固体颗粒相互作用的一种合适方法。
