宝鸡市一次污染过程黑碳气溶胶的变化特征及潜在源解析

利用 AE-31 型黑碳仪于 2019年 2 月 4–26 日对宝鸡市的黑碳 (BC) 气溶胶进行了在线连续监测, 并结合 PM2:5 质量浓度、风速风向等数据, 采用聚类分析研究了该地区污染期间 BC 质量浓度的变化及来源。结果表明, 观测期间 BC 平均质量浓度为 2.8 µg·m−3, 范围为 0.4∼8.0 µg·m−3; PM2:5 平均质量浓度为 119.9 µg·m−3, 范围为 17.3∼221.9 µg·m−3; 重度污染期间 BC 和 PM2:5 平均质量浓度分别为 3.4 µg·m−3 和 176.4 µg·m−3。空气质量为“良”, BC 质量浓度日变化有 明显峰值; 空气质量为“ 轻度污染”时, BC 质量浓度日变化呈“双峰双谷”型; 当空气质量为“中度和重度污染”时, BC 质 量浓度呈现白天低夜间高的变化趋势。研究结果还发现东南和东北风向对 BC 影响较大。在静风和非静风条件下, 当 空气质量为“良、轻度、中度和重度污染”时, BC 质量浓度分别为 1.9 µg·m−3 和 1.5 µg·m−3、 2.4 µg·m−3 和 2.2 µg·m−3、 3.5 µg·m−3 和 3.0 µg·m−3、 3.7 µg·m−3 和 3.3 µg·m−3, 表明污染越重 BC 浓度越大, 静风条件下, 污染物易累积。进一步 的后向轨迹聚类分析表明, 来自宝鸡东部的气团以及秦岭的阻挡效应对宝鸡 BC 的浓度影响较大。

Variation Characteristics and Potential Source Apportionment of Black Carbon Aerosol During Primary Pollution Process in Baoji

The black carbon (BC) aerosol data of Baoji City, China were continuously monitored online from February 4 to 26, 2019 using AE-31 Aethalometer in this work, and then combined with the data of PM2:5 mass concentration, wind speed and direction, the variation of BC mass concentration and its sources during the pollution in this region were investigated by cluster analysis. The results shows that the average mass concentration of BC during the observation period is 2.8 µg·m−3, ranging from 0.4 to 8.0 µg·m−3, the average mass concentration of PM2:5 is 119.9 µg·m−3, ranging from 17.3 to 221.9 µg·m−3, and the average mass concentrations of BC and PM2:5 during heavy pollution are 3.4 µg·m−3 and 176.4 µg·m−3, respectively. When the air quality is ”good”, the daily variation of BC mass concentration has obvious peak; when the air quality is ”light pollution”, the daily variation of BC mass concentration is ”double peak and double valley” type; when the air quality is ”moderate and heavy pollution”, the daily variation of BC mass concentration shows a trend of low during the day and high at night. It is also shown that southeast and northeast wind directions have a strong influence on BC. Under gusty and non-gusty conditions, when the air quality is good, light, moderate and heavy pollution, the BC mass concentrations are 1.9 and 1.5 µg·m−3, 2.4 and 2.2 µg·m−3, 3.5 and 3.0 µg·m−3, 3.7 and 3.3 µg·m−3, respectively. It shows that the heavier the pollution, the greater the BC concentration, and the pollutants tend to accumulate under static wind conditions. Furthermore, backward trajectory clustering analysis shows that the air mass from the east of Baoji and the blocking effect of Qinling Mountains have a greater influence on the concentration of BC in Baoji.