Emission of NO and deposition of O<sub>3</sub> in a tropical forest system

Kaplan, Warren; Wofsy, Steven C.; Keller, Michael; Costa, Jorge de Assis

doi:10.1029/jd093id02p01389

Cited by 186 publications

(80 citation statements)

References 40 publications

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“…Underpredicted NO and NO y concentrations in the model might, in turn, be related to underestimated NO emissions from tropical forests. Flux measurements have shown that soils have high emissions of NO x in the forested regions of both central Amazonia (40)(41)(42)(43) and southeast Asia (44). The above-soil NO x emission modeled in the CTM for the wet season of central Amazonia was 10 times lower than the observations reported in the literature (SI Appendix).…”

Section: Discussioncontrasting

confidence: 49%

Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

106

165

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Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO 2 ) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO 2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.isoprene photochemistry | Amazon | organic hydroperoxides

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Section: Discussioncontrasting

confidence: 49%

Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

106

165

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“…219 and Rennenberg 1996). The range of NO 2 compensation points measured for leaves in this study (0.52-1.60 ppbv) is comparable to the value of 1.15 ppbv reported in a past study of wheat leaves and 1.60-1.90 in beech trees (Gessler et al 2000;Kaplan et al 1988), but is somewhat higher than the range reported for coniferous trees (0.1-0.7 ppbv; Rondon et al 1993;Rondon and Granat 1994). NO 2 compensation points were generally related to leaf N concentration with the highest compensation points corresponding to the highest leaf N concentrations (Table 1).…”

Section: Discussionsupporting

confidence: 72%

“…Soil fluxes of NO and within-canopy NO y concentrations have been reported to be higher in the dry season than during the wet season in tropical wet forests (Bakwin et al 1990;Kaplan et al 1988). We therefore investigated if tropical tree leaves take up NO 2 at a higher rate in the dry season compared to the wet season.…”

Section: Discussionmentioning

confidence: 99%

Leaf uptake of nitrogen dioxide (NO2) in a tropical wet forest: implications for tropospheric chemistry

et al. 2001

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Tropical forest soils are known to emit large amounts of reactive nitrogen oxide compounds, often referred to collectively as NO y (NO y = NO + NO 2 + HNO 3 + organic nitrates). Plants are known to assimilate and emit NO y and it is therefore likely that plant canopies affect the atmospheric concentration of reactive nitrogen compounds by assimilating or emitting some fraction of the soil-emitted NO y . It is crucial to understand the magnitude of the canopy effects and the primary environmental and physiological controls over NO y exchange in order to accurately quantify regional NO y inventories and parameterize models of tropospheric photochemistry. In this study we focused on nitrogen dioxide (NO 2 ), which is the component of NO y that most directly catalyzes the chemistry of O 3 dynamics, one of the most abundant oxidative species in the troposphere, and which has been reported as the NO y species that is most readily exchanged between plants and the atmosphere. Leaf chamber measurements of NO 2 flux were measured in 25 tree species growing in a wet tropical forest in the Republic of Panama. NO 2 was emitted to the atmosphere at ambient NO 2 concentrations below 0.53-1.60 ppbv (the NO 2 compensation point) depending on species, with the highest rate of emission being 50 pmol m -2 s -1 at <0.1 ppbv. NO 2 was assimilated by leaves at ambient NO 2 concentrations above the compensation point, with the maximum observed uptake rate being 1,550 pmol m -2 s -1 at 5 ppbv. No seasonal variation in leaf NO 2 flux was observed in this study and leaf emission and uptake appeared to be primarily controlled by leaf nitrogen and stomatal conductance, respectively. When scaled to the entire canopy, soil NO emission rates to the atmosphere were estimated to be maximally altered ±19% by the overlying canopy.

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“…Andreae et al (1992) came to a similar result for their early night experiment in the Congo (see Table 1). They estimated the chemical contribution to O 3 deposition as only about 35% by assuming the relatively high NO dry season soil emissions measured by Kaplan et al (1988) in central Amazonia. In both cases, a significant additional sink is necessary to close the early night ozone budget.…”

Section: Ozone Deposition Mechanismsmentioning

confidence: 99%

Seasonal variation of ozone deposition to a tropical rain forest in southwest Amazonia

et al. 2007

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Abstract. Within the project EUropean Studies on Trace gases and Atmospheric CHemistry as a contribution toLarge-scale Biosphere-atmosphere experiment in Amazonia (LBA-EUSTACH), we performed tower-based eddy covariance measurements of O 3 flux above an Amazonian primary rain forest at the end of the wet and dry season. Ozone deposition revealed distinct seasonal differences in the magnitude and diel variation. In the wet season, the rain forest was an effective O 3 sink with a mean daytime (midday) maximum deposition velocity of 2.3 cm s −1 , and a corresponding O 3 flux of −11 nmol m −2 s −1 . At the end of the dry season, the ozone mixing ratio was about four times higher (up to maximum values of 80 ppb) than in the wet season, as a consequence of strong regional biomass burning activity. However, the typical maximum daytime deposition flux was very similar to the wet season. This results from a strong limitation of daytime O 3 deposition due to reduced plant stomatal aperture as a response to large values of the specific humidity deficit. As a result, the average midday deposition velocity in the dry burning season was only 0.5 cm s −1 . The large diel ozone variation caused large canopy storage effects that masked the true diel variation of ozone deposition mechanisms in the measured eddy covariance flux, and for which corrections had to be made. In general, stomatal aperture was sufficient to explain the largest part of daytime ozone deposition. However, during nighttime, chemical reaction with nitrogen monoxide (NO) was found to contribute substantially to the O 3 sink in the rain forest canopy. Further contributions Correspondence to: U. Rummel (udo.rummel@dwd.de) were from non-stomatal plant uptake and other processes that could not be clearly identified.Measurements, made simultaneously on a 22 years old cattle pasture enabled the spatially and temporally direct comparison of O 3 dry deposition values from this site with typical vegetation cover of deforested land in southwest Amazonia to the results from the primary rain forest. The mean ozone deposition to the pasture was found to be systematically lower than that to the forest by 30% in the wet and 18% in the dry season.

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Emission of NO and deposition of O₃ in a tropical forest system

Cited by 186 publications

References 40 publications

Isoprene photochemistry over the Amazon rainforest

Isoprene photochemistry over the Amazon rainforest

Leaf uptake of nitrogen dioxide (NO2) in a tropical wet forest: implications for tropospheric chemistry

Seasonal variation of ozone deposition to a tropical rain forest in southwest Amazonia

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Emission of NO and deposition of O3 in a tropical forest system

Cited by 186 publications

References 40 publications

Isoprene photochemistry over the Amazon rainforest

Isoprene photochemistry over the Amazon rainforest

Leaf uptake of nitrogen dioxide (NO2) in a tropical wet forest: implications for tropospheric chemistry

Seasonal variation of ozone deposition to a tropical rain forest in southwest Amazonia

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Emission of NO and deposition of O₃ in a tropical forest system