Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089, China; Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, China Meteorological Administration, Beijing 100089, China.
Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, China Meteorological Administration, Beijing 100089, China.
Sci Total Environ. 2017 Feb 15;580:1340-1350. doi: 10.1016/j.scitotenv.2016.12.097. Epub 2016 Dec 21.
Understanding the trend of chemical composition of precipitation is of great importance for air pollution control strategies in Northern China. A comprehensive study on the long-term chemical compositions of precipitation was carried out from 2003 to 2014 at the Shangdianzi (SDZ) regional background station in northern China. All samples were analyzed for pH, electrical conductivity and major ions (F, Cl, NO, SO, NH, Mg, Ca, K and Na). The average pH during this period was 4.53±0.35, which is considerably lower than those reported in other background stations in China (Linan, Waliguan and Longfengshan). NH, SO, Ca and NO were the dominant ions in precipitation, with concentrations (volume-weighted mean) of 212.99μeqL, 200.20μeqL, 116.88μeqL and 98.56μeqL, respectively. The ion concentrations at SDZ were much higher than those of other background stations and megacities in China. A significantly increasing trend was observed for NO (7.26%year), and a decreasing trend was observed for SO/NO, suggesting that the precipitation of SDZ evolved from a sulfuric acid type to a mixed type dominated by both sulfuric and nitric acid. The source identification indicated that SO, NO, NH and F were dominated by secondary sources, Mg, Ca and Na mostly originated from natural sources, and K and Cl probably associated with anthropogenic sources. Long-range transport of air masses could influence the acidity, electrical conductivity and ion concentrations of precipitation at SDZ. The higher acidity and ion concentrations mainly occurred in the southerly and westerly trajectory pathways and partially in northwest pathways. Anthropogenic pollutants and crustal sources along these pathways were significant contributors to the chemical composition of precipitation in SDZ.
了解降水化学组成的趋势对于中国北方的空气污染控制策略非常重要。本研究于 2003 年至 2014 年在中国北方的上甸子（SDZ）区域背景站对降水的长期化学组成进行了综合研究。所有样品均分析了 pH 值、电导率和主要离子（F、Cl、NO、SO、NH、Mg、Ca、K 和 Na）。在此期间，平均 pH 值为 4.53±0.35，明显低于中国其他背景站（临安、望关和龙凤山）的报道值。NH、SO、Ca 和 NO 是降水的主要离子，浓度（体积加权平均值）分别为 212.99μeqL、200.20μeqL、116.88μeqL 和 98.56μeqL。SDZ 的离子浓度远高于中国其他背景站和特大城市的浓度。NO 呈显著增加趋势（7.26%/年），而 SO/NO 呈下降趋势，表明 SDZ 的降水由硫酸型向硫酸和硝酸混合型转变。来源识别表明，SO、NO、NH 和 F 主要来源于二次源，Mg、Ca 和 Na 主要来源于自然源，K 和 Cl 可能与人为源有关。气团的长距离输送可能会影响 SDZ 降水的酸度、电导率和离子浓度。较高的酸度和离子浓度主要出现在南风和西风轨迹路径中，部分出现在西北路径中。这些路径上的人为污染物和地壳源是 SDZ 降水化学组成的重要贡献者。
