Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study
Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study
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DOI：
10.5194/acp-19-6843-2019
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发表时间：
2019-05-22
影响因子：
6.3
通讯作者：
Apte, Joshua S.
中科院分区：
文献类型：
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作者：
Gani, Shahzad;Bhandari, Sahil;Apte, Joshua S.
印度德里经常经历世界上最高的城市颗粒物浓度。我们建立了德里气溶胶Supersite研究，以提供德里环境亚微米气溶胶成分的长期表征。在这里，我们报告了1.25年的高度时间分辨的亚微米颗粒物（PM 1）数据，包括黑碳（BC）和非耐火PM 1（NR-PM 1），我们联合收割机开发了一个基于成分的PM 1（“C-PM1”= BC + NR-PM1）我们观察到PM 1浓度和组成的显著季节和日变化，由于源的相互作用，和大气过程。冬季是一年中污染最严重的时期，平均C-PM 1质量浓度接近210 μ g m（-3）。季风炎热多雨，因此使其成为污染最少的时期（C-PM 1类似于50 μ g m（-3））。有机物构成了一天中所有季节和时间的C-PM 1的一半以上。虽然铵，氯化物和硝酸盐各自占C-PM 1的10%，但BC和硫酸盐各自占5%。对于较暖的时期，BC和硫酸盐对C-PM 1的贡献增加，而氯化物的贡献降低到小于2%。绝对质量负荷的季节和日变化一般与通风系数的变化一致，在不利气象条件下（低行星边界层高度和低风速），浓度较高。然而，在C-PM 1组合物的变化的影响，随时间变化的来源，光化学，和气体-颗粒分区。在凉爽的时期，当风是从西北方向，情节小时平均氯化物浓度达到50-100 μ g m（-3），排名在世界上任何地方报道的最高氯化物浓度。在冬季和春季，二级物种贡献了德里C-PM 1质量的近50%-70%，在温暖的夏季和季风月份，二级物种贡献了德里C-PM 1质量的60%-80%。对于较冷的月份，有最高的C-PM 1浓度，夜间来源偏向于主要来源，而白天的C-PM 1是次要物种占主导地位。总的来说，这些研究结果指出了一次排放和更多区域大气化学对影响德里大城市地区的极端颗粒物浓度的重要影响。未来的空气质量战略考虑到德里在区域和地方背景下的情况，将比仅针对当地主要空气污染物的政策更有效。
Delhi, India, routinely experiences some of the world's highest urban particulate matter concentrations. We established the Delhi Aerosol Supersite study to provide long-term characterization of the ambient submicron aerosol composition in Delhi. Here we report on 1.25 years of highly time-resolved speciated submicron particulate matter (PM1) data, including black carbon (BC) and nonrefractory PM1 (NR-PM1), which we combine to develop a composition-based estimate of PM1 ("C-PM1" = BC + NR-PM1) concentrations.We observed marked seasonal and diurnal variability in the concentration and composition of PM1 owing to the interactions of sources and atmospheric processes. Winter was the most polluted period of the year, with average C-PM1 mass concentrations of similar to 210 mu g m(-3). The monsoon was hot and rainy, consequently making it the least polluted (C-PM1 similar to 50 mu g m(-3)) period. Organics constituted more than half of the C-PM1 for all seasons and times of day. While ammonium, chloride, and nitrate each were similar to 10% of the C-PM1 for the cooler months, BC and sulfate contributed similar to 5% each. For the warmer periods, the fractional contribution of BC and sulfate to C-PM1 increased, and the chloride contribution decreased to less than 2 %. The seasonal and diurnal variation in absolute mass loadings were generally consistent with changes in ventilation coefficients, with higher concentrations for periods with unfavorable meteorology - low planetary boundary layer height and low wind speeds. However, the variation in C-PM1 composition was influenced by temporally varying sources, photochemistry, and gas-particle partitioning. During cool periods when wind was from the northwest, episodic hourly averaged chloride concentrations reached 50-100 mu g m(-3), ranking among the highest chloride concentrations reported anywhere in the world.We estimated the contribution of primary emissions and secondary processes to Delhi's submicron aerosol. Secondary species contributed almost 50 %-70% of Delhi's C-PM1 mass for the winter and spring months and up to 60 %-80% for the warmer summer and monsoon months. For the cooler months that had the highest C-PM1 concentrations, the nighttime sources were skewed towards primary sources, while the daytime C-PM1 was dominated by secondary species. Overall, these findings point to the important effects of both primary emissions and more regional atmospheric chemistry on influencing the extreme particle concentrations that impact the Delhi megacity region. Future air quality strategies considering Delhi's situation in both a regional and local context will be more effective than policies targeting only local, primary air pollutants.