Abstract:

To characterize the air pollution relative to season and identify potential pollution sources in Tuanbowa of Tianjin, HYSPLIT model and meteorological data of global data assimilation system (GDAS) were used and the cluster method was applied to invert the tracks of airflows arriving at Tuanbowa of Tianjin during the period from December 2012 to November 2013, and the tracks were classified by season. Moreover, the daily monitoring data of NO₂ and SO₂ during the period were taken into account in analysis of effects of the airflow tracks on concentrations of pollutants in Tuanbowa of Tianjin relative to season. The potential source contribution function (PSCF) analysis method and concentration-weighted trajectory (CWT) analysis method were applied to simulate contributions of the potential sources and CWT of NO₂ and SO₂ relative to season. Results show that airflows coming in from different directions had apparent different impacts on distribution of potential NO₂ and SO₂ sources. The airflow tracks corresponding to the daily mean highest values of NO₂ and SO₂ concentrations were concentrated mainly in winter and autumn. In winter, the daily highest concentration of NO₂ and SO₂ was 115 and 179 μg·m^-3, respectively, with airflows coming mainly from northwest while in autumn, it was 81 and 116 μg·m^-3, respectively, with airflows coming mainly from northwest and southeast. PSCF and CWT of NO₂ and SO₂ in Tuanbohu were distributed in a similar pattern, with the highest concentration of NO₂ and SO₂ appearing in the surroundings of Beijing and Tianjin and areas around the coal industries in Hebei Province, which demonstrate that they are the main potential source areas of the two main pollutants. Compared with the PSCT analysis method, the CWT method may be used to quantitatively simulate concentrations of the pollutants in the potential source area, and the potential source areas simulated with the CWT method are more concentrated than those with the PSCF method, regardless of season, which helps identify potential source areas more accurately.

Key words: backward trajectory model, cluster analysis, potential source, Tuanbowa, environment monitoring site