北京冬季PM_(10)中有机碳与元素碳的高分辨率观测及来源分析

运用先进的RP5400碳颗粒物连续分析仪和TEOM1400a气溶胶质量测量仪于2004年冬季对北京大气PM10及碳气溶胶进行了连续观测,得到了PM10、有机碳(OC)、无机碳(EC)和总碳(TC)的日变化特征。观测期间OC、EC、TC、PM10的浓度和OC/EC比值分别为(21.2±16.0)、(8.9±5.1)、(30.2±20.4)、(172.6±98.3)μg.m-3和2.3±0.9。OC,EC和总碳(TC=OC+EC)分别占PM10质量的(12.4±6.4)%、(5.6±2.3)%和(18±9.2)%。OC,EC和PM10浓度变化范围较大,变化趋势相似,明显受风速影响,风速较大时浓度较小。PM10和OC浓度在夜间明显高于白天,但是EC浓度白天和夜间差别不大。EC在早上交通高峰期间达到最高值,显示了机动车排放源的明显贡献。OC/EC比值在夜间(2.4～2.7)明显高于白天(1.9～2.0),这主要是由于机动车白天排放较多,而夜间机动车相对较少以及燃煤排放较多。北京观测到的TC浓度和OC/EC比值均高于美国、日本的同期观测结果。分析表明北京冬季PM10中有机碳和无机碳以一次性排放为主。应用比值法估算出北京冬季PM10中碳气溶胶的来源主要是机动车(75%贡献)和燃煤(25%)。由此可见,北京PM10中碳污染较为严重,且机动车排放占了较大贡献,需要引起重视。

High Resolution Observation and Source Identification of Carbonaceous Aerosols in PM10 in Beijing in Winter

A continuous observation of organic carbon(OC),elemental carbon(EC) and PM10 was conducted in Beijing in January 2004 in order to study the daily variation characteristics of OC and EC in PM10,OC,EC,TC,PM10 concentration and OC/EC ratio were(21.2±16.0),(8.9± 5.1),(30.2±20.4),(172.6±98.3) μg·m-3 and 2.3±0.9,respectively.OC,EC,and total carbon(TC=OC+EC) account for(12.4±6.4)%,(5.6± 2.3)%,and(18 ±9.2)% of PM10,respectively.The variation concentration of OC,EC and PM10 were much influenced by wind: they were low asso ciated with strong wind,but high with weak wind.Average OC concentrations in night time were 40% higher than that in daytime.Averaged EC concentrations in daytime were close to that in night time.OC concentrations reached peak in night time due to pollution accumulation and stable atmosphere.EC reached peak in the morning corresponds to traffic rush time.The OC/EC ratio in nighttime ranging from 2.4 to 2.7 was higher than that in daytime ranging from 1.9 to 2.0.The organic pollution level and OC/EC ratio in Beijing was higher than other observation results in Japan and USA.A simple ratio method was used to estimate the contribution of sources of carbonaceous aerosols in Beijing PM10.The results show that the motor vehicle source and coal combustion account 75% and 25% respectively for the carbonaceous aerosol in winter in Beijing.It indicates that the motor vehicle is dominant sources for heavy pollution of carbonaceous aerosol in winter in Beijing,which should be paid much attention in PM10 pollution control.