南京北郊黑碳气溶胶污染特征及影响因素分析

Characteristics of Black Carbon Aerosol and Influencing Factors in Northern Suburbs of Nanjing

利用2015年1~10月黑碳小时平均质量浓度、PM2.5浓度、污染气体及常规气象观测资料,对南京北郊黑碳气溶胶的时间序列演变特征、污染特征及其影响因子进行了分析.结果表明,观测期间南京北郊黑碳浓度均值为(2 524±1 754)ng·m^(-3).黑碳浓度具有明显的季节变化,冬季最高,平均值达到(3 468±2 455)ng·m^(-3),春季平均值最低,为(2 142±1 240)ng·m^(-3);其日变化也具有明显的双峰结构,峰值出现在上午07:00~08:00和夜间21:00~22:00.黑碳气溶胶与NOx的相关性较好,说明黑碳浓度受机动车尾气排放的影响较大;但观测期间ΔBC/ΔCO比值较低,表明生物质燃烧可能是黑碳气溶胶的又一个重要来源.黑碳浓度随风速增加呈下降趋势,所有季节中小于2 000 ng·m^(-3)的低黑碳浓度主要集中在正西风及相邻风向上,秋冬季大于6 000 ng·m^(-3)的高黑碳浓度则多出现在偏东风下.灰霾和重度霾天气下的黑碳浓度平均值呈较高水平,是非霾天气下的2~2.3倍.

Based on the hourly averaged data of black carbon（ BC） aerosol,PM2. 5,gaseous pollutants,and meteorological data in the northern suburb of Nanjing from January to October 2015,characteristics and influencing factors of BC concentration variation were analyzed. The mean concentration of BC was found to be（ 2 524 ± 1 754） ng·m^-3 during the observation period. BC concentrations in Nanjing showed strong seasonality,the highest mean concentration of BC occurred during winter reaching（ 3 468 ± 2 455） ng·m^-3,and the lowest mean BC concentration was found during spring being（ 2 142 ± 1 240） ng·m^-3; a distinct diurnal variation of BC with two high peaks occurred,one in the morning during 07： 00 to 08： 00 and the other in late evening during 21： 00 to 22： 00 local time.The strong correlation between BC and NOxindicated a greater impact of vehicle emissions on BC concentration,while a lower rate ofΔBC /ΔCO was found in the northern suburb of Nanjing,suggesting that biomass burning emission might be another important source of BC in here. BC concentration increased with decreasing wind speed. BC concentration lower than 2 000 ng·m^-3mainly occurred in westerly wind and adjacent wind in all seasons,whereas BC concentration higher than 6 000 ng·m^-3more frequently appeared in easterly winds in autumn and winter. BC concentration was higher in hazy and heavy hazy weather,which were 2 and 2. 3 times as large as that in non-hazy weather,respectively.