2013年南昌市区PM_(2.5)的浓度水平及时空分布特征与来源

Concentrations and Spatial-Temporal Characteristics and Source Analysis of PM_(2.5) in Nanchang City in 2013

对2013年南昌市区9个自动空气质量监测点的ρ(PM_(2.5))数据进行分析,探讨了PM_(2.5)浓度水平及时空分布特征,并采用轨迹聚类、PSCF(潜在源贡献因子)、CWT(浓度权重轨迹分析)进行了大气PM_(2.5)的来源分析.结果显示:2013年南昌市区ρ(PM_(2.5))年均值为69.1μg/m^3,超过GB 3095—2012《环境空气质量标准》二级标准限值(35μg/m^3)的97%;ρ(PM_(2.5))昼夜变化呈双峰型分布,峰值位于09:00—11:00和20:00—22:00;月际变化呈两边高、中间低的"V"型趋势;ρ(PM_(2.5))有明显的季节性变化特征,由高到低依次为冬季、春季、秋季和夏季;ρ(PM_(2.5))空间分布呈由东南至西北递减的分布特征.气流轨迹聚类结果表明,南昌市气流输送季节性变化特征明显,夏季来自南方或东南方向的气流比例高达65.6%,而在另外三个季节,东北和偏北方向的气流分别占62.0%(冬)、59.6%(春)、54.7%(秋),对南昌市ρ(PM_(2.5))影响较大;夏季南方或东南方向的气流所占比例较高,为65.6%;PM_(2.5)的PSCF和CWT的高值主要集中在南昌本地和邻近的浙江省及福建省北部地区,但周边的河南南部、江苏中部也是南昌市PM_(2.5)的潜在来源地.

PM_2.5 data from nine automatic air quality monitoring stations in Nanchang City in 2013 were analyzed to examine the spatial and temporal characteristics of PM_2.5. The potential sources of PM_2.5 were explored by trajectory cluster, potential source contribution function （PSCF） and concentration-weighted trajectory （ CWT）. The results showed that the annual average PM_2.5 concentration was 69.1 μg/m3 in 2013, exceeding the secondary national standard （35 μg/m3 ） by 97%. The diurnal variation curve showed a bimodal distribution with peaks at 09：00-11：00 and 20：00-22：00. The monthly average concentration of PM_2.5 at each station showed a ‘V＇- shaped trend, i. e. , higher on both sides while lower in the middle. The seasonal variation of PM_2.5 was significant with the sequence of winter 〉 spring 〉 autumn 〉 The temporal characteristics of PM_2.5 showed a significant decreasing trend from the southeast to the northwest. There was an obvious difference in the potential source area distribution of PM_2.5 owing to the airflow in different directions. The airflow trajectories were mainly from the south and the southeast in summer, with contribution of 65.6%. However, the inland airflow trajectories were mainly from the northeast and the north in winter, spring and autumn, with contributions of 62.0% , 59.6% and 54.7% , respectively, which greatly affected the PM_2.5 level in Nanchang City. The higher PM_2.5 values analyzed by PSCF and CWT were in Nanchang City, Zhejiang Province and northern Fujian Province, while southern Henan province and central Jiangsu province were also potential source areas of PM_2.5 in Nanchang City.