2013—2017年天津市大气自净能力与大气颗粒物质量浓度特征分析

基于经验公式分析了天津市2013-2017年大气自净能力，以及PM_2.5和PM₁₀质量浓度的时空分布特征，并探讨了大气自净能力与大气颗粒物PM_2.5质量浓度的关系，以期更好的理解大气环境对污染物浓度变化的影响。结果表明：时间变化上，天津市大气自净能力在午后13-14时最大，夜间最低，一年之中在采暖季（10月至翌年3月）要小于非采暖季，与之相反，天津市PM_2.5和PM₁₀质量浓度在采暖季均高于非采暖季。2017年相对于2013年，大气自净能力增加了5%，而PM_2.5质量浓度下降了34%，PM₁₀质量浓度则减少了47%。空间分布上，大气自净能力各季节均表现为沿海高于内陆，城区低于郊区的分布，天津市的PM_2.5和PM₁₀质量浓度的高值也主要集中在中南部地区，尤其是城区。大气自净能力与颗粒物浓度的分布在空间分布上有着一定的对应关系。分析表明，天津市大气自净能力日均值与PM_2.5质量浓度日均值呈负相关，两者的相关系数为-0.34，在采暖季，相关系数有所提高。通过大气自净能力与PM_2.5质量浓度变化的分析可知，重污染事件大多数发生在低大气自净能力时。

Feature analysis of atmospheric self-purification capability and atmospheric particulate concentration in Tianjin during 2013-2017

Based on the empirical formula,the spatial and temporal characteristics of atmospheric self-purification capability (APC) and concentrations of PM_2.5 and PM₁₀ were analyzed in this paper.Meanwhile,the relationship between APC and particulate concentrations were also analyzed to well understand the impact of the atmospheric environment on the pollutant concentrations.Results reveal that the highest value of the APC appears from 13:00 to 14:00 and the lowest one appears at night during a day.During the year,the APC is relatively lower during the building heating seasons from October to March than that during the non-heating seasons.Conversely,the particulate concentrations are higher during the building heating season than those during the non-heating seasons.Compared with 2013,the annual APC increased 5%,and the concentrations of PM_2.5 and PM₁₀ decreased 34% and 47%,respectively,in 2017.The APC value in the coastal area is higher than that in the inland area,and that in the urban area is lower than that in the surrounding areas.The high value of the particulate concentrations concentrates on the south-central area,especially in urban region.The spatial distributions of APC have a good relationship with that of particulate concentrations.There is a negative correlation between the daily averaged values of the APC and PM_2.5 concentration.The correlation coefficient is about -0.34,and it increases during the heating season.The heavy pollution incidents mostly happen during the low APC periods.