西宁地区大气中黑碳气溶胶浓度的观测研究

Variation of Black-Carbon Aerosol Concentration Observed in Xining

对2005年9月至2007年7月在西宁获得的黑碳气溶胶（BC）浓度观测资料及气象观测资料进行了分析．结果表明，受当地冬季取暖和冬季逆温出现频率高的影响，BC浓度的月际变化规律明显，且变化幅度大，BC浓度高值出现在每年10月至次年1月；低值出现在5—8月；日平均浓度为4240．1ng·m^-3，其变化范围为957．5～11045．5ng·m^-3．受局地人为活动和大气垂直对流扩散等影响，BC浓度日变化表现出明显的双峰值特征，BC高浓度出现在7：00-12：00和18：00～24：00，而低浓度一般出现在14：00～17：00和02：00～05：00时段．与相距90km的瓦里关全球本底站相比，西宁BC日平均浓度偏高约13倍，且月际变化差异大，但与国内部分城市相比还是较低（除西藏拉萨外）．

The black-carbon （BC） aerosol concen- trations observed in Xining from September, 2005 to July, 2007 are analyzed. It is found that under the influence of winter heating and high frequency of temperature inversion, the monthly concentration of BC varies in evidence, the high BC concentration appears from October to next January, and the lower one appears from May to August. Daily average of the concentration is 4 240.1 ng ·m^-3 with an amplitude ranging from 957.5 to 11 045.5 ng·m^3 . In addition, the daily variation of BC concentration is characterized by a pronounced doublepeak patterns, with the higher concentration dur ing 7：00-12：00 AM and 18：00-24：00 PM. and the lower one during 0：00-5：00 and 14：00-17：00 PM, which is attributed to human activity and atmospheric vertical convection diffusion. The BC concentration in this area is 13 times more than that observed at Waliguan Global Atmospheric Baseline Observatory （90 km apart from Xining）. But it is still lower as compared with some observations at home and abroad. The base BC concentration of this study area is about 2 300 ng·m^-3 based on the maximum frequency of hourly mean concentration.