Observations of particulate matter, NO 2 , SO 2 , O 3 , H 2 S and selected VOCs at a semi-urban environment in the Amazon region.

This research aims to assess air quality in a transitional location between city and forest in the Amazon region. Located downwind of the Manaus metropolitan region, this study is part of the large-scale experiment GoAmazon2014/5. Based on their pollutant potential, inhalable particulate matter (PM2.5 ), nitrogen dioxide (NO2 ), sulfur dioxide (SO2 ), ozone (O3 ), hydrogen sulfide (H2 S), benzene, toluene, ethylbenzene and meta-, orto-, para-xylene (BTEX) were selected for analysis. Sampling took place during the wet season (March-April 2014) and dry season (August-October 2014). The number of forest fires in the surroundings was higher during the dry wet season. Results show significant increase during the dry season in mass concentration (wet: <0.01-10 μg m-3 ; dry: 9.8-69 μg m-3 ), NH4 + soluble content (wet: 13-125 μg m-3 ; dry: 86-323 μg m-3 ) and K+ soluble content (wet: 11-168 μg m-3 ; dry 60-356 μg m-3 ) of the PM2.5 , and O3 levels (wet: 1.4-14 μg m-3 ; dry: 1.0-40 μg m-3 ), indicating influence of biomass burning emissions. BTEX concentrations were low in both periods, but also increased during the dry season. A weak correlation in the time series of the organic and inorganic gaseous pollutants indicates a combination of different sources in both seasons and NO2 results suggest a spatial heterogeneity in gaseous pollutants levels beyond initial expectations.