Four-year measurements of trace gases (SO2, NOx, CO, and O3) at an urban location, Kanpur, in Northern India

• Published in: Journal of atmospheric chemistry Vol. 71; no. 4; pp. 283 - 301
• Main Authors: Gaur, Abhishek, Tripathi, S. N., Kanawade, V. P., Tare, Vinod, Shukla, S. P.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.12.2014; Springer; Springer Nature B.V
• Subjects: Agricultural land; Anthropogenic factors; Atmospheric chemistry; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Boundary layers; Carbon monoxide; Earth and Environmental Science; Earth Sciences; Measurement; Monsoons; Nitrogen oxides; Outdoor air quality; Ozone; Pollution dispersion; Power plants; Relative humidity; Seasonal variations; Seasons; Sulfur; Sulfur compounds; Sulfur dioxide; Summer; Urban areas; Urbanization; Ventilation; Winter; India; Kanpur India; Urbanization; Seasonal variations; Air quality; Surface ozone
• ISSN: 0167-7764; 1573-0662
• DOI: 10.1007/s10874-014-9295-8

In this study, we present long-term near-surface measurements of sulfur dioxide (SO 2 ), oxides of nitrogen (NO x ), carbon monoxide (CO), and ozone (O 3 ) carried out at an urban location, Kanpur (26.46°N, 80.33°E, 125 m amsl), in Northern India from June 2009 to May 2013. The mean concentrations of SO 2 , NO x , CO, and O 3 over the entire study period were 3.0, 5.7, 721, and 27.9 ppb, respectively. SO 2 , NO x and CO concentrations were highest during the winter season, whereas O 3 concentration peaked during summer. The former could be attributed mainly to the near-surface anthropogenic sources (e.g. automobiles, residential cooking, brick kilns, coal-burning power plants, agricultural land-clearing, and biomass burning) and low mixing height in winter, whereas the latter was clearly due to enhanced chemical production of O 3 during the pre-monsoon (i.e. summer) season. The lowest concentration of all trace gases were observed during the monsoon season, due to efficient wet scavenging by precipitation. The averaged diurnal patterns also showed similar seasonal variation. NO x and CO showed peaks during morning and evening traffic hours and a valley in the afternoon irrespective of the seasons, clearly linked to the boundary layer height evolution. Contrarily, O 3 depicted a reverse pattern with highest concentrations during afternoon hours and lowest in the morning hours. The mean rate of change of O 3 concentrations (dO 3 /dt) during the morning hours (08:00 to 11:00 h) and evening hours (17:00 to 19:00 h) at Kanpur were 3.3 ppb h −1 and −2.6 ppb h −1 , respectively. O 3 followed a positive linear relationship with temperature, except in post-monsoon season while the strong negative with the relative humidity in all seasons. The ventilation coefficient was found to be highest in the pre-monsoon season (15,622 m 2  s −1 ) and lowest during winter (2564 m 2  s −1 ), indicative of excellent pollution dispersion efficiency during the pre-monsoon season. However, the low ventilation coefficient during winter and post-monsoon seasons indicated that the high-pollution potential occurs at this site.