【摘要】 为研究典型物流城市临沂市冬季重污染天气过程中PM_2.5化学组分特征,探讨污染成因,于2016年12月～2017年1月在6个采样点连续采集28 d的PM_2.5样品,并对其离子、元素、碳组分进行分析.采样期间PM_2.5质量浓度均值（145. 2±87. 8）μg·m^-3,日均值超标率为82%; 2次污染过程中PM_2.5均值浓度分别为（187. 3±79. 8）μg·m^-3和（205. 3±92. 0）μg·m^-3,为《环境空气质量标准》（GB 3095-2012）年均二级标准的5. 4和5. 9倍.化学组分质量重构结果显示二次无机离子（SNA）是冬季PM_2.5的主要组分（所占质量分数为51. 2%）,其次为有机物OM（23. 8%）,再次为矿物尘MIN（12. 7%）.结合污染过程中化学组分的变化趋势和累积速率发现,第1个污染过程中SNA和OM是引起PM_2.5浓度增加的原因之一,第2个污染过程中SNA是导致污染的主因,硫氧化率（SOR）、氮氧化率（NOR）和OC/EC比值的日均变化趋势进一步验证了该结论. PMF源解析结果表明,临沂市冬季大气PM_2.5的首要源类为二次颗粒物和生物质燃烧混合源（分担率50. 0%）,其次为燃煤源（16. 8%）、机动车（12. 9%）和城市扬尘（10. 0%）,再次为工业源（5. 3%）和土壤尘（5. 0%）. 2次污染过程中二次颗粒物的贡献较之冬季平均有明显增加,说明不利气象条件下二次颗粒物的生成、累积是导致重污染期形成的主因.更多还原

【Abstract】 To characterize the chemical composition of PM_2.5 and the formation of pollution during a heavy pollution episode in the winter in a typical logistics city,PM_2.5 samples were collected from December 2016 to January 2017 at six sampling sites,and the water-soluble ions,elements,and carbon components were determined. The results showed that the average concentration of PM_2.5 was（ 145. 2 ± 87. 8） μg·m^-3 during the whole sampling period,of which 82% of daily average concentrations were above class II of the national standards. The average concentrations of PM_2.5 during the two heavy pollution episodes were（ 187. 3 ± 79. 8） and（ 205. 3 ±92. 0） μg·m^-3,which were 5. 4 and 5. 9 times,respectively,as high as class II of the national standard. The results of the chemical composition of the PM_2.5 showed that secondary water-soluble inorganic ions( SO₄^2-,NO₃^-,and NH₄⁺) were the main components of PM_2.5 in winter( 51. 2% of PM_2.5 mass concentration),followed by organic matter（ OM,23. 8%）,and mineral dust（ 12. 7%）.Combined with the change trend and accumulation rate of chemical components during the pollution episode,we discovered that the increasing of SNA and OM led to PM_2.5 pollution in the first episode,while the growth of SNA caused the second pollution episode.This was further verified by the synchronous change of SOR,NOR,and the OC/EC ratio. PMF analysis indicated that mixed sources of secondary particulate matter and biomass combustion（ 50. 0%）,coal combustion（ 16. 8%）,vehicles（ 12. 9%）,fugitive dust（ 10. 0%）,industry（ 5. 3%） and soil dust（ 5. 0%）,were the main sources of PM_2.5 of Linyi city in the winter. Compared with the average concentration over the whole sampling period,the contribution of secondary particles during the two pollution episodes was significantly increased. This indicates that the formation and accumulation of secondary particulate matter under static and humid meteorological conditions were the main influencing factors during the heavy pollution episodes.更多还原