Observations of ambient trace gas and PM10 concentrations at Patna, Central Ganga Basin during 2013–2014: The influence of meteorological variables on atmospheric pollutants

Abstract

Atmospheric pollutants including ozone (O3), sulfur dioxide (SO2), oxides of nitrogen (NOx), carbon monoxide (CO), and inhalable particulate matter (PM10) were measured in the central Indo-Gangetic Basin (IGB) at Patna, India, from 1st March 2013 to 31st December 2014, and significant variability was observed in the temporal patterns of these pollutant concentrations. The mean O3, SO2, NO, NO2, CO (trace gases: TG), and PM10 (PM) concentrations were 14.5±4.8, 5.9±4.8, 23.1±22, 20.6±14.6ppb, 1.5±0.7ppm, and 192.0±132.8μg/m3, respectively, over the study period. The highest concentrations of these species were during the post-monsoon and winter seasons except O3 and SO2 that showed the highest concentrations during the pre-monsoon. The lowest concentrations of TG and PM were observed during the monsoon season as a result of scavenging by rain. NO and NO2 along with PM concentrations decreased by ~76, 19, and 63% when the wind speed (WS) was >0.5m/s. However, for O3, an opposite trend was observed with ~14% higher concentrations. The WS was negatively correlated with PM during the winter (−0.48) and post-monsoon (− 0.32) seasons. In order to investigate the source region of TG and PM, 5-day air mass back trajectories were computed. The dominance of the air masses (92, 53, and 49%) were from the IGB is highly polluted during the winter, pre-monsoon, and post-monsoon, respectively. The TG and PM were observed much higher during these periods. During the biomass burning period (post-monsoon), the trajectory analysis showed that the TG and PM concentrations were around three-fold higher (flow from the IGB ) than the other seasons. To improve air quality over IGB, the mitigation measures should be designed to reduce emissions from both local and regional sources.