沈阳黑炭气溶胶浓度的观测研究分析

Online measurement of atmospheric black carbon aerosol concentration in Shenyang in autumn and winter

对2008年3月至2009年2月沈阳黑炭气溶胶(BC)质量浓度观测资料进行了研究分析。结果表明,沈阳黑炭质量浓度平均值为6.143μg/m^3,每小时平均质量浓度最大值达51.426 μg/m^3。黑炭质量浓度日变化有明显的双峰特征,最高值一般出现在7:00—9:00和18:00—20:00,低值出现在2:00—4:00和13:00—15:00。黑炭质量浓度具有明显的季节变化,并且与近地层大气温度垂直梯度有着较好的对应关系。夏季黑炭平均质量浓度最低,最高值出现在1月份,这与冬季取暖和近地层经常出现逆温等有关。与国外城市和国内拉萨与西宁相比,沈阳黑炭质量浓度明显偏高,但与北京和西安的黑炭质量浓度大致相当。

The paper is intended to present its observation and analysis results on the black carbon （BC） aerosol concentrations observed during the period from March, 2008 to February, 2009 in Shenyang. The results show that the mean concentration of the atmospheric BCaerosols in Shenyang is 6.143 μg/m3, with hourly minimal concentration of 0.347 μg/m3 and maximal concentration at 51.426μg/m3. The hourly BC concentration mainly lies in 1 μg/m3 to 7 μg/m3, with all the observed data at a rate of 70.1%, and the occurring frequency of BC concentration are smaller than 1 μg/m3 and higher than 25 μg/m3, which proves to be much lower, with the separately ratio being 1.7 % and 1.3 % of all the observed data. Daily variation of BC concentration tends to be characterized by a remarkable double-peak pattern, with its peak concentration taking place during the period from 7：00 to 9：00 and that from 18：00 to 20：00. However, the lower concentration would come out during the period from 2 ： 00 to 4 ： 00 and that from 13：00 to 15：00, as a result of meteorological conditions and daily variation of the pollution emission. Moreover, the peak concentration tends to be much higher in winter than in other seasons, due to the influence of the winter house-heating, meteorological conditions and human activities. The AM peak concentration in winter takes place later than in other seasons. On the other hand, due to the influence of winter house-heating and very often occurring temperature inversion at the higher atmospheric strata, the concentration of BC tends to vary greatly from season to season. To be exact, the highest BC concentration appears in January with the concentration value of 10.485 μg/m3, and the lowest in summer being 4.903 μg/m3. The vertical gradient of the atmospheric temperature in upper strata proves to vary roughly in the same way as with the BC concentration. Thus, our measurements show that the BC concentration in Shenyang is much higher as compared with that in some foreign cities and domestic cities such as Lhasa and Xining, but keeps roughly at the same level as those in Beijing and Xi＇an.