天津市市郊社区不同采暖期昼夜PM2.5成分及来源差异

  目的  了解在采暖和非采暖期天津市周边区域居民社区不同时段空气中细颗粒物（fine particulate matter，PM_2.5）的污染和来源差异。  方法  采集市郊某社区2015-2016年间每日昼夜两时段的PM_2.5样品，分别检测PM_2.5样品的质量浓度，金属元素，多环芳烃和无机水溶性离子浓度，并运用正矩阵因子分解模型分析社区不同时段空气中PM_2.5的金属元素，多环芳烃和无机水溶性离子的来源差异。  结果  在采暖期城市周边居民社区部分金属元素日间时段浓度高于夜间时段，在非采暖期部分多环芳烃和无机水溶性离子浓度夜间时段高于日间时段，而部分金属元素日间时段浓度高于夜间时段，采暖期城市周边居民社区空气PM_2.5日间时段的主要来源为燃煤排放，来源贡献率为50.1%，夜间时段的主要来源分别为二次气溶胶和汽、柴油车燃料燃烧排放，来源贡献率分别为41.0%和35.9%。非采暖期城市周边居民社区空气PM_2.5日间时段的主要来源为室内活动排放，夜间时段主要来源为二次气溶胶，来源贡献率分别为29.8%和31.1%。  结论  城市周边区域居民社区空气PM_2.5的污染状况较为严重，不同采暖期和不同时段的污染来源均存在差异。

Composition and source apportionment differences of daytime and nighttime samples of PM2.5 in the community of suburb in Tianjin during different heating periods

  Objective  To study the pollution and source apportionment differences of different periods PM_2.5 in the residential community of suburb in Tianjin City during heating and non-heating periods.  Methods  From 2015 to 2016, daytime and nighttime PM_2.5 samples were collected at a community in the suburb of Tianjin. The mass concentration of PM_2.5 samples and major chemical components in PM_2.5, including metal elements, polycyclic aromatic hydrocarbons (PAHs) and inorganic water-soluble ions were monitored. Positive matrix factorization (PMF) model was used to apportion potential sources of metal elements, PAHs and inorganic water-soluble ions in daytime and nighttime PM_2.5.  Results  In the heating period, the concentrations of some metal elements of suburban residential community were higher in the daytime than in the nighttime. In the non-heating period, the concentrations of some PAHs and inorganic water-soluble ions of suburban residential community were higher in the nighttime than in the daytime. Meanwhile, the concentrations of some metal elements were greater in the daytime than in the nighttime. When in heating period, the main source of PM_2.5 in the suburban residential community was coal combustion during daytime and its source contribution rate was 50.1% while secondary aerosol and fuel combustion emissions of gasoline and diesel vehicles were main sources during nighttime and their source contribution rates were 41.0% and 35.9%. The principal source of daytime PM_2.5 in the suburban residential community was indoor activity emissions during non-heating period, and secondary aerosol was main source during nighttime and their source contribution rates were 29.8% and 31.1%.  Conclusions  The pollution status of PM_2.5 in residential communities of suburban is serious, and the source apportionment of day and night PM_2.5 samples has different in different heating periods.