Influences of nitrogen oxides and isoprene on ozone-temperature relationships in the Amazon rain forest. (1st June 2019)

• Record Type: Journal Article
• Authors: Wei, Dandan; Fuentes, Jose D.; Gerken, Tobias; Trowbridge, Amy M.; Stoy, Paul C.; Chamecki, Marcelo
• Is Part Of: Atmospheric environment. Volume 206(2019)
• Page Start: 280
• Page End: 292
• Publication Date: 2019-06-01
• Subjects: Amazon rain forest -- Urban plumes -- Ozone -- Temperature -- Nitrogen oxides; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2019.02.044
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: As human encroachment increases in the Amazon rain forest, it is important to determine how anthropogenic emissions of reactive gases affect regional atmospheric chemistry. In the present study, we investigate the extent to which urban air plumes modify the levels of ozone (O3 ) and nitrogen oxides (NO X ) in the downwind rain forest. The median mixing ratios of the background O3, NO X, and NO X oxidation products (NO Z ) were 20 (15 parts per billion on a volume basis, ppbv), 0.6 ppbv (0.6 ppbv), and 1.0 ppbv (0.5 ppbv) during the dry (wet) season at the study site. Compared to the background environment, air plumes from the city of Manaus had enhanced median mixing ratios for O3 and NO Z by 30–50% and 40–90%, respectively. However, the enhancements of NO X in the air plumes were less than 20%, indicating that the majority of NO X was chemically converted to O3 and NO Z during transport. Results from a photochemical model showed that an injection of 8 ppbv of NO X into the rain forest can cause up to 260% and 150% increases in O3 and hydroxyl radical (OH) levels compared to the background conditions, indicating the likely extent that NO X can modify the air quality and oxidative capacity in the Amazon rain forest. Slopes of the O3 -temperature linear relationships increased with NO X levels from 3.7 to 6.5 ppbv per degree Kelvin during the dry season and 1.7–5.5 ppbv per degree Kelvin during the wet season. Average rates of change of the slope with respect to NO Z were approximately 1.8 and 2.3 times higher than those with respect to NO X for the dry and wet seasons. One key conclusion of this study is that NO Z substantially contributed to the O3 formation in response to temperature under enhanced NO X conditions in the forested environment. Highlights: Compared to the background environment, air plumes from the city of Manaus, Brazil can enhance median mixing ratios for ozone and products from nitrogen oxides by up to 50 and 90%, respectively. Results from a photochemical model showed that an injection of 8 parts per billion of nitrogen oxides into the rain forest can cause up to 260 and 150% increases in ozone and hydroxyl radical levels compared to the background conditions. This study concludes that additions of nitrogen oxides to the rain forest, which abundantly emits isoprene and monoterpenes, substantially modify the air quality and oxidative capacity in the Amazon rain forest.