Characteristics and source apportionment of black carbon the urban and desert underlying surfaces

The spatial distribution of black carbon (BC) concentrations was highly variable across different underlying surfaces. Differences in meteorological conditions and emission sources led to great temporal and spatial variations in BC characteristics. As the most important absorbing aerosol, BC can affect radiation, clouds, and surface snow. BC mass concentrations were measured using a seven channel aethalometer (AE-33) in the Urumqi and Taklimakan Deserts from January to December 2022. The aethalometer data, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) models were used to analyse the variation characteristics, potential sources, and affected areas. Results showed that the BC concentrations in the Taklamakan Desert and Urumqi were in the range of 0–500 ng·m−3, accounting for 66.20 % and 59.50 % of the total, respectively. The backward trajectory simulation of BC mass concentration in the tower and Urumqi using the HYSPLIT model found that the airflow trajectories in the tower in summer corresponded to the BC concentration in the following order: trajectory 4 > trajectory 3 > trajectory 2 > trajectory 1, and trajectory 4 originated from the Turpan airflow accounting for 46.19 % of the total, which corresponded to the highest BC concentration of 621.73 ng·m−3. The trajectories of the airflow in Urumqi in summer corresponded to the BC concentration in the order of high to low, and the BC concentration in summer corresponded to the highest concentration in the Turpan airflow. BC concentrations arranged from high to low were trajectory 1 > trajectory 5 > trajectory 3 > trajectory 4 > trajectory 2. Trajectories 3, 4, and 5 airflow directions were the same, and the airflow trajectory accounted for 47.48 %, corresponding to BC concentrations of 599.82 ng·m−3, 579.99 ng·m−3, and 555.85 ng·m−3, respectively. Tower in the spring compared with other seasons of the CWT value of >400 ng·m−3 had the widest coverage, and Urumqi had more source areas contributing to moderate pollution concentration weights in winter (400 ng·m−3