Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, India; APTL at Centre for Environmental Science and Engineering (CESE), Indian Institute of Technology Kanpur, Kanpur 208 016, India.
Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, India; APTL at Centre for Environmental Science and Engineering (CESE), Indian Institute of Technology Kanpur, Kanpur 208 016, India.
Sci Total Environ. 2021 Apr 1;763:143032. doi: 10.1016/j.scitotenv.2020.143032. Epub 2020 Oct 20.
Measurements of water-soluble total nitrogen (WSTN), water-soluble inorganic nitrogen (WSIN), water-soluble organic nitrogen (WSON) and ẟN (total N) was carried out on PM aerosol samples during wintertime to understand the major sources of ambient nitrogenous species at a heavily polluted location of Kanpur in north India. During the nighttime sampling campaign, WSON and NH_N contributed dominantly to the WSTN. Ammonium-rich condition persisted during sampling (NH/SO average equivalent mass ratio = 3.1 ± 0.7), suggesting complete neutralization of SO and formation of NHNO, which is stable in winter due to low temperature and high relative humidity (RH). Stagnant atmospheric conditions during wintertime enhanced concentrations of ionic species (SO, NH, and NO) at this location. Good correlations between NO_N, NH_N and biomass burning tracer K (and also between NO_N, NH_N and SO) suggests a strong impact of biomass burning activities. Multi-linear regression (MLR) analysis shows a strong dependence of ẟN on NO_N, SO and WSON in night-1 (10:00 pm to 2:00 am) and on NO_N and SO in night-2 (2:00 am to 6:00 am) depicting different formation and removal mechanism of aerosols during both the time-periods. ẟN in PM varied from +8.8 to +15.5‰ (10.8 ± 1.3), similar to the variability observed for many urban locations in India and elsewhere. NH_N and WSON control the final ẟN value of nitrogenous aerosols. High relative humidity during nighttime enhanced the secondary organic aerosols formation due to aqueous-phase formation and gas to particle-phase partitioning. Isotopic fractionations associated with multi-phase reactions during gas to particle conversion of NH would result in an increase in ẟN by ~48‰ to 51‰ (at T of 5.4 °C to 15.4 °C) than that of the emission source(s), which indicates the most likely N-emission sources at Kanpur to be from agriculture activities and waste generation.
在印度北部坎普尔的一个重度污染地区，冬季对 PM 气溶胶样本进行了水溶性总氮（WSTN）、水溶性无机氮（WSIN）、水溶性有机氮（WSON）和 ẟN（总氮）的测量，以了解环境含氮物种的主要来源。在夜间采样期间，WSON 和 NH₃-N 对 WSTN 的贡献最大。采样期间存在富铵条件（NH₄+/SO₄²⁻平均当量质量比=3.1±0.7），表明 SO 完全中和形成 NH₄NO₃，由于低温和高相对湿度（RH），NH₄NO₃ 在冬季稳定。冬季大气停滞条件增强了该地区离子物种（SO₄²⁻、NH₄⁺和 NO₃⁻）的浓度。NO₃-N、NH₃-N 和生物质燃烧示踪剂 K 之间（以及 NO₃-N、NH₃-N 和 SO₄²⁻之间）存在良好的相关性，表明生物质燃烧活动的强烈影响。多元线性回归（MLR）分析表明，ẟN 在夜间 1（晚上 10 点至凌晨 2 点）对 NO₃-N、SO₄²⁻和 WSON 以及夜间 2（凌晨 2 点至早上 6 点）对 NO₃-N 和 SO₄²⁻的依赖性很强，描绘了两个时间段内气溶胶的不同形成和去除机制。PM 中的 ẟN 变化范围为+8.8 至+15.5‰（10.8±1.3），与印度和其他地方许多城市地区观察到的变化相似。NH₃-N 和 WSON 控制含氮气溶胶的最终 ẟN 值。夜间高相对湿度增强了二次有机气溶胶的形成，这是由于水相形成和气到颗粒相分配。NH 气到颗粒相转化过程中多相反应相关的同位素分馏会导致 ẟN 增加约 48‰至 51‰（在 5.4°C 至 15.4°C 的 T 下），比排放源的 ẟN 值高，这表明坎普尔最有可能的 N 排放源来自农业活动和废物产生。
