Human and animal wastes: Implications for atmospheric N₂O and NO_x

Abstract

[1] More than 220 Tg N are processed annually through the global agriculture/animal/ human food chain. It is suggested that aerobic denitrification, reduction of nitrite formed in the first stage of nitrification, is an important source not only of global N 2 O but also of NO x . A simple top-down method indicates a globally averaged yield of 2% for N 2 O emitted as a consequence of human disturbances to the global nitrogen cycle. This yield can account not only for the contemporary budget of atmospheric N 2 O but also for trends observed over the past 1000 years. The associated microbial source of NO x is estimated assuming a NO x /N 2 O ratio of 3, consistent with results from a variety of laboratory and field studies. This source is significant, particularly for large developing countries such as China and India for which its contribution is comparable to that from fossil fuel.

Seasonal variability of NOx emissions over east China constrained by satellite observations: Implications for combustion and microbial sources

“…Although these errors are within the uncertainty range assigned below for top‐down emissions, they are nontrivial suggesting the need of better understanding lightning NO x over China. It has been suggested further that the microbial source of NO x at northern midlatitudes should be increased by a factor of 2 in GEOS‐Chem [ McElroy and Wang , 2005; Jaeglé et al , 2005], corresponding to about a 30% increase in total NO x sources over the same region. Another sensitivity test was implemented in which the background columns over east China assumed in GOME TVCs were increased by 30% relative to the GEOS‐Chem simulation.…”

“…Our focus on the seasonal variability of emissions was framed in order to refine our understanding of the microbial source of NO x over China. McElroy and Wang [2005] proposed that reduction of nitrite by nitrifying bacteria under low oxygen conditions could provide a significant source of NO x and suggested that this source had been significantly underestimated in contemporary models of tropospheric chemistry. The temporal coverage of their study, however, was limited to spring [ Wang et al , 2004].…”

Summertime influence of Asian pollution in the free troposphere over North America

“…Figure 8 shows that the model significantly underestimates the magnitude of the enhancements observed by MOPITT, in particular in the plume associated with export in the typhoon. Second, the model might be underestimating Asian anthropogenic and soil NO x emissions [ Wang et al , 2004; McElroy and Wang , 2005; Martin et al , 2006]. Jaeglé et al [2005] found that during summer, emissions from soils over Asia account for almost as much NO x as emissions from anthropogenic combustion sources, and that the inventory used by GEOS‐Chem underestimates this soil source by a factor of 2.…”

Constraint of anthropogenic NO<sub>x</sub> emissions in China from different sectors: a new methodology using multiple satellite retrievals

“…NO x emissions from biomass burning and aircraft are held constant given their relatively small contribution. Soil NO x emissions specified using the Yienger and Levy (1995) scheme are thought to be too low by a factor of 2-3 (Wang et al, 2004Jaégle et al, 2005;Zhao and Wang, 2009) in China, due likely to an underestimate of the sources associated with fertilization and human/animal food chain (Wang et al, 2004;McElroy and Wang, 2005). They are doubled therefore for purposes of the top-down constraint.…”