A pilot study of gaseous pollutants' measurement (NO2, SO2, NH3, HNO3 and O-3) in Abidjan, Cote d'Ivoire: contribution to an overview of gaseous pollution in African cities

摘要

This work is part of the DACCIWA FP7 project (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) in the framework of the Work Package 2 "Air Pollution and Health". This study aims to characterize urban air pollution levels through the measurement of NO2, SO2, NH3, HNO3 and O-3 in Abidjan, the economic capital of Cote d'Ivoire. Measurements of inorganic gaseous pollutants, i.e. NO2, SO2, NH3, HNO3 and O-3 were performed in Abidjan during an intensive campaign within the dry season (15 December 2015 to 16 February 2016), using INDAAF (International Network to study Deposition and Atmospheric chemistry in AFrica) passive samplers exposed in duplicate for 2-week periods. Twenty-one sites were selected in the district of Abidjan to be representative of various anthropogenic and natural sources of air pollution in the city. Results from this intensive campaign show that gas concentrations are strongly linked to surrounding pollution sources and show a high spatial variability. Also, NH3, NO2 and O-3 gases were present at relatively higher concentrations at all the sites. NH3 average concentrations varied between 9.1 +/- 1.7 ppb at a suburban site and 102.1 +/- 9.1 ppb at a domestic fires site. NO2 mean concentration varied from 2.7 +/- 0.1 ppb at a suburban site to 25.0 +/- 1.7 ppb at an industrial site. Moreover, we measured the highest O-3 concentration at the two coastal sites of Gonzagueville and Felix-Houphouet-Boigny International Airport located in the southeast of the city, with average concentrations of 19.1 +/- 1.7 and 18.8 +/- 3.0 ppb, respectively. The SO2 average concentration never exceeded 7.2 +/- 1.2 ppb over all the sites, with 71.5% of the sampling sites showing concentrations ranging between 0.4 and 1.9 ppb. The HNO3 average concentration ranged between 0.2 and 1.4 ppb. All these results were combined with meteorological parameters to provide the first mapping of gaseous pollutants on the scale of the district of Abidjan using geostatistical