西安大气黑碳气溶胶的观测和分析

Measurement and Analysis of Black Carbon Aerosol in Xi'an

2004年在西安站点利用黑碳测量仪(Aethalometer)获得了10个月大气中每5min黑碳气溶胶(BC)浓度的演化特征,最大值出现在12月11日,为124.5mg/m3,最小值出现在7月11日为0.2mg/m3.每日的最大值为12月15日,BC日平均浓度为63.1mg/m3,最小值在7月22日,为2.0mg/m3.11月BC平均浓度达到最高,为21.8mg/m3,在4月达到最低值,为9.0mg/m3.获得了BC浓度周变化模式,秋冬2季浓度明显高于春夏,并且变化趋势相似,都表现为双峰,从周一和周五开始BC浓度升高,自周六则表现为下降趋势.各季周末BC浓度均较低.一日内BC的浓度变化趋势在不同季节基本相似,春、夏、秋的最高值出现在23点,冬季出现在21点,下午BC浓度明显降低.和下午相比,早上(6～9点)和晚上(19～23点)都出现明显的峰值.和国内、外城市相比,西安市BC浓度较高,机动车、燃煤和生物质燃烧是主要贡献源.

Black carbon(BC) aerosol was measured using an aethalometer at Xi'an station for 10 months in 2004.Every 5 min BC concentrations ranged from 0.2 to 124.5 mg/m3.Average daily BC concentrations were found to be the highest in December 15 with 63.1 mg/m3,the lowest in July 22 with 2.0 mg/m3.The average monthly BC concentrations were from 9.0 mg/m3 in April to 21.8 mg/m3 in November.The weekly patterns of BC concentrations appeared to be dual-peak distributions.The value of BC in autumn and winter was higher than that of spring and summer.The BC concentrations became higher on Monday and Friday.Significant reduction in BC values was observed on Saturday.The diurnal variation pattern of BC was similar for all seasons.BC concentrations found to be the highest at 23:00 h in spring,summer and autumn,at 21:00 h in winter.Low value has been observed in afternoon.BC concentrations are high during morning(06:00 to 09:00 h) and evening hours(19:00 to 23:00 h) compared with afternoon hours.Compared with BC concentrations of other cities and background stations in the world,BC over Xi'an atmosphere was higher.Motor vehicle exhaust,coal combustion emissions and biomass burning contributed to the highest BC concentrations in Xi'an.