Fluxes of nitrogen oxides over a temperate deciduous forest

Abstract

[1] Eddy covariance flux measurements of NO, NO 2 , and O 3 were obtained above the mixed deciduous canopy at Harvard Forest in central Massachusetts from April to November 2000. Net deposition of NO x was observed throughout the measurement period, with average velocity of $0.2 cm s À1 . At night, NO 2 is deposited at a rate that depends nonlinearly on NO 2 concentration and cannot be explained by N 2 O 5 hydrolysis, suggesting HONO formation by heterogeneous disproportionation of NO 2 . During the day, photochemically driven NO x fluxes conform to the predicted behavior based on gradients of light and eddy diffusivity through the canopy, with residual net flux attributable to both stomatal and nonstomatal processes. The results were consistent with a compensation point for NO 2 near 1.5 nmol mol À1 . These results were confirmed by independent evidence from NO, NO 2 , and O 3 profiles acquired at the site over several years. If the rate of NO x deposition observed at this site in April through November continues during the winter, it would have a larger potential impact on tropospheric chemistry because mixing depths are shallow and chemical NO x oxidation is slow during winter; the impact at night is important for the same reasons. The results contradict widely used parameterizations of NO 2 deposition that both overestimate stomatal uptake and do not allow for surface uptake when stomates are closed.

TRANC – a novel fast-response converter to measure total reactive atmospheric nitrogen

“…McCalley and Sparks (2009), for example, report on 86 % for NH 3 measured with their converter system and 100 % for NO 2 . Horii et al (2004) compared concentrations of NO 2 obtained by TDLAS versus photolysis-chemiluminescence instruments and found a slope of 1.1 ± 0.2 with a R 2 of 0.91. The TD-LIF instrument presented by Farmer et al (2006) was tested by Thornton et al (2003) and Rosen et al (2004) with a conversion efficiency of >95 % for NO 2 and >94 % for PN using photolysis-chemiluminescence and gas chromatographs equipped with electron capture detectors, respectively, for comparative measurements.…”

“…Shaw et al, 1998). Further problems in measuring N r compounds are the lack of capable techniques for fastresponse detection, issues regarding inlet design, sampling losses and air column chemical reactions for highly reactive and soluble N r species (Horii et al, 2004(Horii et al, , 2006. Hence, the establishment of large-scale dry deposition monitoring networks of total N r remains nearly impracticable.…”

“…In the last decade, substantial progress has been made in the use of tunable diode laser absorption spectroscopy (TDLAS) and quantum cascade lasers (QCL) as well as devices originating from individual applications such as Fourier transform infrared (FTIR) spectrometers. The precision and fast response of these approaches has allowed first EC measurements of field scale N 2 O and CH 4 fluxes (Rinne et al, 2005;Denmead et al, 2010;Kroon et al, 2010;Neftel et al, 2010;Tuzson et al, 2010) as well as first NO 2 fluxes (Horii et al, 2004), whereas measurements of NH 3 fluxes by EC have been extremely limited (Famulari et al, 2004;Sutton et al, 2007;Sintermann et al, 2011), and are subject to substantial uncertainty (e.g. Shaw et al, 1998).…”

Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest

“…Emissions of NO from soils at HFEMS are negligible (Horii et al, 2005). But Horii et al (2004) observed bi-directional fluxes of NO 2 and suggested a compensation point for NO 2 near 1.5 ppbv at HFEMS, the ambient concentration below which NO 2 is emitted from stomata. Given that [NO 2 ] approached this level occasionally during the daytime within the selected period (Fig.…”

Application of thermal-dissociation laser induced fluorescence (TD-LIF) to measurement of HNO<sub>3</sub>, Σalkyl nitrates, Σperoxy nitrates, and NO<sub>2</sub> fluxes using eddy covariance

“…EC flux measurements of NO y , NO, and NO 2 fluxes have been reported (e.g. Delany et al, 1986, Horii et al, 2004Munger et al, 1996;Rummel et al, 2002). Most other studies of N fluxes have used enclosure or indirect estimation techniques, including gradient measurements or resistance modeling (Hanson and Lindberg, 1991;Wesely and Hicks, 2000).…”