Precipitation chemistry measurements are essential to estimate the deposition of ionic components that are beneficial or harmful to the ecosystems and quantify the wet scavenging of the atmospheric constituents. A long-term (2006 to 2016) database of the water-soluble inorganic components in the rainwater (RW) at Pune (an urban location) and Sinhagad (a high-altitude rural location) in southwest India was examined to understand the trends in measured anthropogenic components and the factors controlling the chemistry of RW in this region. We observed the long-term increasing trends in NH4+ at Pune and SO42−, NO3¯, and NH4+ at Sinhagad. About 10% of rain samples were acidic (below 5.6). Low pH values were generally measured at Pune (8%) and Sinhagad (9%) stations when the air mass back trajectories (AMBTs) originated from land. This study suggests that NO3¯ plays a vital role in acidifying the rain in both the sampling stations, though SO42− remains the dominant factor. The high concentrations of Ca2+ and NH4+ have played a significant role in neutralizing the acidity of RW. The cluster analysis of AMBTs showed that at Pune 74% and Sinahagd 65% of rain events were associated with oceanic air masses from the Arabian Sea.

中文翻译：

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印度西南降水中次生无机成分湿沉降的长期增长趋势

降水化学测量对于估计对生态系统有益或有害的离子成分的沉积和量化大气成分的湿清除至关重要。研究了印度西南部浦那（城市地区）和辛哈加德（高海拔农村地区）雨水 (RW) 中水溶性无机成分的长期（2006 年至 2016 年）数据库，以了解测量的人为成分和控制该地区 RW 化学的因素。我们观察到 Pune 的 NH4+ 和 Sinhagad 的 SO42−、NO3¯ 和 NH4+ 的长期增加趋势。大约 10% 的雨水样本是酸性的（低于 5.6）。当气团反向轨迹 (AMBT) 源自陆地时，通常在 Pune (8%) 和 Sinhagad (9%) 站测量低 pH 值。这项研究表明，虽然 SO42− 仍然是主导因素，但在两个采样站，NO3¯ 在酸化雨水方面起着至关重要的作用。高浓度的 Ca2+ 和 NH4+ 在中和 RW 的酸度方面发挥了重要作用。AMBT 的聚类分析表明，在浦那 74% 和 Sinahagd 65% 的降雨事件与来自阿拉伯海的海洋气团有关。