利用SPAMS研究石家庄市冬季连续灰霾天气的污染特征及成因

2014年11月18~26日石家庄市发生了连续的灰霾天气.利用位于石家庄市大气自动监测站(20 m)的单颗粒气溶胶质谱仪(SPAMS)分析了细颗粒物的化学组成,根据石家庄市大气污染物排放源谱库对主要成分进行了来源解析,并结合颗粒物质量浓度和气象条件研究了该地区冬季灰霾天气成因.结果表明,石家庄市大气细颗粒物来源分为7类,各源示踪离子:燃煤源为Al,工业源为OC、Fe、Pb,机动车尾气源为EC,扬尘源为Al、Ca、Si,生物质燃烧源为K和左旋葡聚糖,纯二次无机源为SO-4、NO-2和NO-3,餐饮源为HOC.灰霾期间大气中主要含有OC、HOC、EC、HEC、ECOC、富钾颗粒、矿物质和重金属等8类颗粒,其中OC和ECOC颗粒最多,分别占到总数的50%和20%以上,OC颗粒主要来自燃煤和工业工艺,ECOC颗粒主要来自燃煤和机动车尾气排放.灰霾发生时含有NH+4、SO-4、NO-2和NO-3等二次离子的颗粒物占比升高,其中含NH+4颗粒增幅最大;EC、OC与NO-3、SO-4、NH+4在灰霾天气下的混合程度均比干净天气高,其中与NH+4的混合程度加剧最为明显.冬季采暖期煤炭的大量燃烧、医化行业工艺过程及机动车尾气等污染源排放的一次气态污染物(SO2、NOx、NH3、VOCs)和一次颗粒物在静稳天气中难以扩散而迅速累积,气态污染物发生二次转化形成硝酸铵、硫酸铵,而颗粒物之间通过碰撞形成二次颗粒物并发生不同程度的混合,从而导致大气能见度下降,以上是石家庄市冬季灰霾形成的主要原因.

Characteristics and Formation Mechanism of a Multi-Day Haze in the Winter of Shijiazhuang Using a Single Particle Aerosol Mass Spectrometer(SPAMS)

A multi-day haze episode occurred in Shijiazhuang during November 18-26, 2014. The characteristics were studied based on the data collected by the single particle aerosol mass spectrometer (SPAMS) located in the automatic monitoring station (20 meters) of Shijiazhuang. In accordance with the source spectral library of atmospheric pollutant emissions in Shijiazhuang, the main sources were distinguished and analyzed. The mass concentration of particulate matters and meteorological conditions being taken in account, the causes of haze in winter were also studied. It turned out that fine particulate matters in the Shijiazhuang air were mainly from 7 different sources: the tracer ion of coal source was Al; the tracer ions of industry sources were OC, Fe, and Pb; the tracer ion of motor vehicle tail gas source was EC; the tracer ions of dust source were Al, Ca and Si; the tracer ions of biomass burning source were K and levoglucosan; the tracer ions of pure secondary inorganic source were SO₄^-, NO₂^-, and NO₃^-, and the tracer ion of dining source was HOC. Of the above mentioned, OC, HOC, EC, HEC, ECOC, rich potassium particles minerals and heavy metals were 8 dominant polluting groups in hazy days. OC and ECOC particles were the majority, which accounted for more than 50% and 20% of the overall measured particles. OC particles were mainly discharged from coal combustion and industrial processes, and ECOC particles were mainly from coal combustion and vehicle exhaust emissions. When haze occurred in Shijiazhuang the proportion of pollutant particles of NH₄⁺, SO₄^-, NO₂^- and NO₃^-increased, of which NH₄⁺ was the most sharply increased. The mixed degree between EC, OC and NH₄⁺, SO₄^-, NO₃^-in the haze was higher than usual, of which NH₄⁺ was the most sharply increased. In the static and stable weather gaseous (SO₂, NO_x, NH₃, VOCs) pollutants and particles were difficult to spread and accumulated rapidly, which were discharged from coal combustion, the process of the medical industry and the automobile exhaust. The gaseous pollutants tended to react for the second time and formed the ammonium nitrate and ammonium sulfate particles. Secondary particles were formed by collision and mixed with each other adequately or mildly, which caused the reduction of atmospheric visibility. This was the main cause for the haze during the winter in Shijiazhuang.