LAUSR

This study characterizes the black carbon in Agra, India home to the Taj Mahal—and situated in the Indo-Gangetic basin. The mean black carbon concentration is 9.5 μg m−3 and, owing to excessive biomass/fossil fuel combustion and automobile emissions, the concentration varies considerably. Seasonally, the black carbon mass concentration is highest in winter, probably due to the increased fossil fuel consumption for heating and cooking, apart from a low boundary layer. The nocturnal peak rises prominently in winter, when the use of domestic heating is excessive. Meanwhile, the concentration is lowest during the monsoon season because of the turbulent atmospheric conditions and the process of washout by precipitation. The ratio of black carbon to brown carbon is less than unity during the entire study period, except in winter (December). This may be because that biomass combustion and diesel exhaust are major black carbon contributors in this region, while a higher ratio in winter may be due to the increased consumption of fossil fuel and wood for heating purposes. ANOVA reveals significant monthly variation in the concentration of black carbon; plus, it is negatively correlated with wind speed and temperature. A high black carbon mass concentration is observed at moderate (1–2 m s−1) wind speed, as compared to calm or turbulent atmospheric conditions.摘 要本研究针对印度恒河盆地阿格拉地区的大气黑炭浓度变化特征进行了分析. 研究表明, 阿格拉地区黑炭的年均浓度为 9.5 µg m−3. 但由于生物质/化石燃料的燃烧, 黑炭浓度季节变化幅度十分剧烈. 由于冬季夜间边界层高度较低, 同时采暖和烹饪燃烧大量的化石燃料, 黑炭浓度通常在这个季节的夜间达到最高. 季风来临季节, 雨水的清洗作用和较好的大气扩散条件导致这一季节黑炭浓度最低. 除了化石燃料燃烧较多的冬季(12 月份)外, 其他季节黑炭和棕炭的比例均低于 1. 这表征了生物质/化石燃料燃烧对黑炭的贡献十分显著. 通过 ANOVA 统计方法研究了黑炭浓度季节变化与气象因子的相关性, 发现黑炭浓度季节变化与风速和温度有明显的负相关关系. 另外, 相对于静风和湍流旺盛时段, 中等风速(1–2 m s‒1)时黑炭浓度更高.