Spatial variation of long term annual precipitation volume weighted concentrations of major chemical constituents (SO4−2, NO3−, Cl−, NH4+, Ca+2, Mg+2, Na+ and K+ ) at all the ten Global Atmospheric Watch (GAW) stations in India for the period from 1981 to 2012 is studied in this paper. Ionic abundance and balance is studied as well. The range of long term annual mean pH at ten stations was 5.25 ± 0.82 to 6.91 ± 0.76, lowest at Mohanbari and highest at Jodhpur. The long term annual mean pH for the period 1981–2012 showed decreasing trend at all the stations (significant at 5 % level). Decadal mean pH among ten stations for 1981–1990, 1991–2000 and 2001–2012 ranged between 7.31 to 5.76, 7.45 to 4.92 and 6.16 to 4.77 respectively and showed decreasing trend at all the stations during 1981–1990 to 2001–12. The percentage occurrence of acidic pH (<5.65) at ten stations ranged from 3 to 72 %, lowest at Jodhpur and highest at Mohanbari and it increased from 1981–1990 to 2001–2012 almost at all the stations. Temporal variation of annual mean values of nssSO4−2, NO3−, Ca+2 and pH for the study period were attempted. Variation of nss K (non sea salt Potassium) at all the stations was studied to assess the biomass burning contribution in different regions. Non-marine (terrestrial) contribution dominated for majority of ionic constituents at most of the stations. However marine contribution was found to be dominant for Mg at Port Blair and Minicoy. Also sea salt fraction of SO4 was higher than terrestrial at Minicoy. Sources of measured ionic constituents in rain water are assessed through correlation analysis. The concentrations of all the ionic species were lowest at Kodaikanal, a high altitude hill top station and the total ionic mass was 136.0 μeq/l. Jodhpur, an arid station not only had highest concentrations of Ca+2, SO4−2 and K+ but also had highest total ionic content (1051.8 μeq/l) among all the stations. At Srinagar, Jodhpur, Allahabad, Nagpur and Pune stations Ca+2 was the dominant cation while dominant anion was NO3− for Srinagar, Allahabad, and Nagpur and Cl− for Jodhpur and Pune; at Mohanbari NO3− and Ca+2; at Visakhapatnam, Port Blair and Minicoy Na+ and Cl− were abundant. Temporal variation had shown an increasing trend for nssSO4−2 and NO3− and obviously decreasing trend for pH at all the stations. However, Ca+2 showed a decreasing trend at all the stations except at Port Blair. With the exception of Pune and Jodhpur stations, nssK showed a decreasing trend at all the stations revealing decreasing influence of soil/biomass burning over Indian GAW stations. Negative correlation of pH with SO4−2 was found to be weak compared to NO3–.

中文翻译：

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印度所有 10 个 GAW 站雨水化学成分的年度和十年变化

全球 10 个全球大气监视网 (GAW) 站的主要化学成分（SO4−2、NO3−、Cl−、NH4+、Ca+2、Mg+2、Na+ 和 K+）的长期年降水量加权浓度的空间变化本文研究了印度 1981 年至 2012 年期间的情况。离子丰度和平衡也被研究。十个站点的长期年平均 pH 值范围为 5.25 ± 0.82 至 6.91 ± 0.76，Mohanbari 最低，焦特布尔最高。1981-2012 年期间所有站点的长期年平均 pH 值呈下降趋势（在 5% 水平上显着）。1981-1990年、1991-2000年和2001-2012年10个站的年代际平均pH值分别在7.31～5.76、7.45～4.92和6.16～4.77之间，1981～2009年各站均呈下降趋势。酸性 pH (<5. 65) 在 10 个站点的范围从 3% 到 72%，在 Jodhpur 最低，在 Mohanbari 最高，并且从 1981-1990 到 2001-2012 几乎所有站点都增加了。尝试了研究期间 nssSO4-2、NO3-、Ca+2 和 pH 的年平均值的时间变化。研究了所有站点的 nss K（非海盐钾）的变化，以评估不同区域的生物质燃烧贡献。在大多数站点，非海洋（陆地）贡献占大多数离子成分的主导地位。然而，在布莱尔港和米尼科伊发现海洋贡献对镁占主导地位。在 Minicoy，SO4 的海盐比例也高于陆地。通过相关性分析评估雨水中测量离子成分的来源。所有离子物质的浓度在 Kodaikanal 处最低，高海拔山顶站，总离子质量为 136.0 μeq/l。焦特布尔，一个干旱的站点，不仅 Ca+2、SO4-2 和 K+ 的浓度最高，而且在所有站点中总离子含量也最高（1051.8 μeq/l）。在斯利那加、焦特布尔、阿拉哈巴德、那格浦尔和浦那站，Ca+2 是主要阳离子，而主要阴离子是 NO3−，对于斯利那加、阿拉哈巴德和那格浦尔，以及 Cl−对于焦特布尔和浦那；在 Mohanbari NO3− 和 Ca+2；在维沙卡帕特南、布莱尔港和 Minicoy Na+ 和 Cl− 含量丰富。所有站点的 nssSO4−2 和 NO3− 的时间变化均呈上升趋势，而 pH 值呈明显下降趋势。但除布莱尔港外，所有站点的Ca+2均呈下降趋势。除了浦那和焦特布尔车站，nssK 在所有站点均呈下降趋势，表明土壤/生物质燃烧对印度 GAW 站点的影响正在减小。与 NO3- 相比，pH 值与 SO4-2 的负相关性较弱。