Emission of nitric oxide (NO) from tropical forest soils and exchange of NO between the forest canopy and atmospheric boundary layers

Abstract

Emissions of NO from soils in the Amazon rain forest were measured at 66 locations (224 measurements) using an enclosure technique, and continuous vertical profiles of NO and 03 were measured between the ground and 41-m altitude. Fluxes of NO averaged 8.9 (+1.5) x 109 molecules crn -2 s -1 from the dominant (yellow clay) soils of the region, with larger fluxes (33.7 (_+6.5) x 109 molecules cm -2 s -1) observed from adjacent white sand softs. Fluxes from clay softs were lower by more than a factor of 5 than fluxes observed during the dry season at a nearby site. Low soil emission rates were reflected in lower concentrations of NO at the top of the forest canopy in the wet season, only 30-50 pptv (parts per trillion by volme) during the daytime. The measured fluxes are consistent with chemical mass balances for NO within the forest canopy, calculated from the NO and 03 profiles taken at night, and with observations of NO between 150 and 5000 m altitude (A. L. Torres and K. R. Hooks, unpublished manuscript, 1989). Measurements of NO emission rates from soil plots fertilized using NaNO3, NH4C1 or sucrose indicated that a reducfive pathway (alenitrification) may have been primarily responsible for production of the NO released by both clay and sand softs.

Isoprene photochemistry over the Amazon rainforest

“…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).…”

Influence of urban pollution on the production of organic particulate matter from isoprene epoxydiols in central Amazonia

“…Nitric oxide concentrations characteristic of central Amazonia range from 20 to 70 ppt (Torres and Buchan, 1988;Bakwin et al, 1990;Levine et al, 2015). Daytime maximum ozone concentrations are 10 to 15 ppb (Rummel et al, 2007).…”

An automated dynamic chamber system for surface exchange measurement of non-reactive and reactive trace gases of grassland ecosystems

“…Bargsten et al, 2008). For vegetation higher than about 30 cm, the chamber height can easily be extended by an additional cylinder module (similar to Bakwin et al, 1990;Suh et al, 2006). Finally, the chamber system may also be used for indoor applications with a controlled environment, e.g.…”

“…after rain events (Meixner et al, 1997), after cutting (Davison et al, 2008) or fertilisation (Bakwin et al, 1990). A variable number of individual chambers (e.g.…”