青藏高原瓦里关站黑碳气溶胶长期演变特征及来源分析

Long-term evolution and sources of the black carbon at Waliguan station over the Qinghai-Tibetan Plateau

为了解青藏高原黑碳气溶胶的长期演变特征及来源,使用1994年7月至2017年7月共24 a的中国瓦里关全球大气本底站等效黑碳浓度地面观测数据,1994年8月至2004年6月的风向、风速地面观测数据,美国国家环境预测中心/国家大气研究中心全球再分析气象数据,分析了青藏高原中国瓦里关全球大气本底站测量的等效黑碳浓度的长期演变特征及输送特征。在此基础上利用拉格朗日混合单粒子轨道模型、浓度权重轨迹分析方法分析了黑碳污染气团的区域输送路径及潜在来源。结果表明,瓦里关站的等效黑碳浓度在24 a间先升后降,在2012年达到浓度高值,随后降低。24 a月平均浓度最高值出现在4月,最低值出现在11月。等效黑碳浓度的日变化特征在不同季节表现不同,春、夏、秋季均为双峰特征,峰值出现在凌晨和午后,冬季日变化较为平缓。等效黑碳浓度与风向密切相关,年均浓度最高值出现在东东北风向,次高值出现在东风向。通过浓度权重轨迹方法对黑碳污染气团的潜在来源分析可以看出,污染物主要来自瓦里关站的西南和东南方向。

To understand the long-term evolution characteristics and sources of black carbon in Qinghai-Tibetan Plateau,the ground observation data of equivalent Black Carbon(eBC)concentration from July 1994 to July 2017 and wind direction and wind speed from August 1994 to June 2004 collected at the Global Atmospheric Background Station in Waliguan and the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR)global reanalysis meteorological data are used to analyze the long-term evolution and transmission characteristics of the eBC at the Global Atmospheric Background Station in Waliguan.On this basis,the regional transport pathways and potential sources of black carbon pollution air masses are analyzed by using the Hybrid Single-Particle Lagrangian Integrated Trajectory method and the concentration-weighted trajectory analysis method.The results show that the equivalent black carbon concentration at the Waliguan station increases first and then decreases,and the maximum value appeared in 2012.The maximum value of the 24-month average concentration appears in April,and the lowest value appears in November.The diurnal variation of equivalent black carbon concentration is different in different seasons with bimodal characteristics in spring,summer and autumn,and the peak appears in the early morning and afternoon.The diurnal variation is relatively gentle in winter.The equivalent black carbon concentration is closely related to wind direction.The highest average annual concentration occurs when easterly-northeasterly winds prevail,and the second highest concentration occurs when easterly winds prevail.Based on the analysis of the potential sources of black carbon pollution air masses by the concentration weight trajectory method,it can be seen that the pollutants mainly come from the regions to the southwest and southeast of Waliguan station.