Long-Term Measurements of SO2 Over Delhi, India
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Long-term measurements (2011–2018) of ambient sulphur dioxide (SO2) and meteorology were carried out at an urban site of Delhi, India, to study the seasonal and inter-annual variations of SO2 over Delhi. The average mixing ratio of SO2 was estimated as 2.26 ± 0.48 ppb for the entire study period. Mixing ratio of ambient SO2 was estimated as 2.19 ± 0.64 ppb, 2.07 ± 0.89 ppb, 2.49 ± 1.05 ppb and 2.27 ± 0.71 ppb during winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. SO2 mixing ratio was recorded maxima during monsoon (2.49 ± 1.05 ppb) season, whereas minima during pre-monsoon season (2.07 ± 0.89 ppb). The mixing ratio of SO2 showed slightly increase in the trend during observational period. Surface wind speed and wind directions analysis indicates the influence of local sources on the mixing ratio of SO2 at the study site. Backward trajectories and potential source contributing factor (PSCF) analysis also showed the local as well as the regional sources (industrial activities, coal burning and thermal power plants etc.,) influencing the mixing ratio of SO2 over Delhi.
KeywordsAmbient SO2 Seasonal variation Trajectory analysis PSCF analysis
The authors are thankful to the Director, CSIR-National Physical Laboratory, New Delhi, and Head, Environmental Sciences and Biomedical Metrology Division, CSIR-NPL, New Delhi, for their encouragement and support for this study. The authors thankfully acknowledge the NOAA for downloading the trajectories datasets (ftp://arlftp.arlhq.noaa.gov/pub/archives/gdas1) and HYSPLIT model. The authors are thankful to the anonymous reviewers for their constructive suggestions to improve the manuscript.
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