Nitrous Oxide Release Research Articles

A Discounted Threat: Environmental Impacts of the Livestock Industry

This article provides an overview of the environmental effects of the livestock industry. Current industry practice, specifically the proliferation of concentrated animal feeding operations as the primary means of production, has left far-reaching ecological consequences in its wake. Animal agriculture is implicated in numerous environmental threats including rising greenhouse gas emissions (particularly through release of nitrous oxide and methane, in addition to carbon dioxide), overconsumption of water for both live animals and feed crops, and decreased water quality. Furthermore, localized pollution owing to copious animal waste has tainted many regions and compromised human health. Alterations of land use and the resulting loss of biodiversity are also of major concern. The problem has expanded as developing countries’ appetite for these products grows – however, the issue has tended not to be a focal point of environmental debate. The article details the environmental destruction wrought by current practices, while outlining recommendations for reducing the environmental toll, at both the individual and systemic level

Nitrous oxide emissions from a waterbody in the Nenjiang basin, China

Using static, closed chambers and gas chromatography techniques, nitrous oxide (N2O) emissions have been monitored for 1 year (2009–2010) on an inland running waterbody downstream of the Nenjiang basin, China. During the freezing period, holes were dug in the ice in order to obtain nitrous oxide samples. Here, we have focused on water-air gas exchange and factors which might influence N2O emissions and flux. Initial results indicate: (1) N2O flux rates reach peak emission in January and the annual emissions of N2O were low, being estimated at 0.35 ± 0.20 μgm–2 h−1; significant seasonal differences only appeared between January and July; (2) N2O flux rates have strong regularity and ice has been the main barrier to nitrous oxide release during winter; (3) 24-hour monitoring revealed that N2O flux remained steady during 9:00–17:00; (4) N2O emissions have significant relationships with ammonium nitrogen and total phosphorus concentrations in water (r = 0.4467, p = 0.020 and r = 0.4793, p = 0.011, respectively). The N2O flux released from the waterbody is determined by the chemical concentrations in the water. Following these results, we suggest that moderate use of N and P fertilizer at intensive agricultural areas will be beneficial in decreasing greenhouse gas emissions from this waterbody.

Nitrogen dynamics in complex Danube River floodplain systems: effects of restoration

We used a hydromorphological model to assess areas of potential high denitrification rates and nitrous oxide release in a frequently and an infrequently connected fl oodplain system of the Danube River under different river discharge conditions. Based on the model’s projections, the decoupled floodplain was predicted to have more areas of high potential denitrification during mean and elevated discharge, but with more sites dominated by incomplete denitrification, resulting in higher N2O emission. In the restored floodplain, frequently inundated, the model predicted that lower rates of denitrification would occur at lower river discharge levels, dominated by complete denitrification, resulting in N2rather than N2O production. During an annual flood (5300 m3s–1), flooding both floodplains, the restored floodplain was predicted to have more areas of high potential denitrification activity than the decoupled floodplain. The model outputs suggest that floodplains subject to frequent inundations can effectively and efficiently use nitrate input from the main river channel, resulting in complete denitrification. Restoration measures should attempt to promote frequent inundation periods in order to fully realize the high denitrification potential of floodplain systems.

Nitrate removal rate, efficiency and pollution swapping potential of different organic carbon media in laboratory denitrification bioreactors

Laboratory denitrifying bioreactors, which use an organic carbon (C) rich media to enhance microbial reduction of nitrate (NO3−) to nitrogen (N) gases, are used worldwide to protect surface and groundwater. To highlight potential adverse effects of denitrifying bioreactors, NO3− removal rates (gNO3-Nm−3d−1 removed), NO3− removal efficiencies (% removed minus production of other N species) and release of greenhouse gases and solutes (ammonium (NH4+), phosphorus (P) and organic carbon (C)) were compared in this study using different media: lodgepole pine woodchips (LPW), cardboard, lodgepole pine needles (LPN), barley straw (BBS) and a soil control. Results showed that NO3− removals were consistently >99% for all media for initial leaching and steady-state periods. When pollution swapping was considered, this ranged from 67% for LPW to 95% for cardboard. Sustained P releases over the threshold for the occurrence of eutrophication were measured in all media. Greenhouse gas emissions were dominated by carbon dioxide (CO2) and methane (CH4) fluxes with little nitrous oxide (N2O) release due to the anaerobic conditions prevalent within the bioreactors. Comparisons of different media, under steady-state conditions, showed that C fluxes were highest for cardboard and BBS bioreactors. Carbon fluxes from cardboard bioreactors ranged from 11.6gCm−2d−1 to 13.9gCm−2d−1, whilst BBS emissions ranged from 3.9gCm−2d−1 to 4.4gCm−2d−1. These C emissions were correlated with the total surface area exposed within the media. Such investigations highlight the need to consider pollution swapping during the initial leaching period and should improve design criteria for field-scale bioreactors used to mitigate shallow groundwater NO3−.

Meta-Analysis of Environmental Impacts on Nitrous Oxide Release in Response to N Amendment

Atmospheric nitrous oxide (N2O) accounts for approximately 5% of the global greenhouse effect and destroys stratospheric ozone. Soils are the most important source of N2O, which is produced during nitrification and denitrification. To assess the impact of environmental variables and ecosystems on N2O flux, we performed a meta-analysis comparing N2O flux in N amended and matched control plots in non-agricultural soils. We found that N2O release increased with N amendment in the short term. Although there were few studies in shrubland, this ecosystem showed the greatest response. The N2O response to N amendment was greater in year-round studies and in studies with more measurements, but lower in longer studies. The N2O response was greater at higher latitudes and precipitation rates. We also observed an unexpected 55% decline in the N2O response to N amendment over the 23 years covered by the studies. This pattern may reflect a suppression of the N2O response from long-term N deposition accumulation, particularly in temperate regions. Although short term increases in reactive N entering natural systems may cause positive feedbacks to the release of N2O, this effect may diminish over time in locations with high rates of N deposition.

Forest management effects on carbon sequestration and Nitrous Oxide release

Forests not only produce timber and sequestrate carbon dioxide (CO2) but also release nitrous oxide (N2O) to the atmosphere. The sequestration of CO2 and release of N2O plays a crucial role in climate change. The importance of their impact to the environment has been recognised during 1990s and different policies have been formed to reward the benefits of forest resources. Forest management practices are changed to optimise the environmental services of forest resources. Forests in Central Europe have a long and dynamic management history. The litter raking, fuel wood extraction and small diameter timber production in the forest during preindustrial age has been replaced by large diameter timber production due to industrial development. Further, forest management changed to address the climate change issues. In Austria, Quercus rubur/petraea a coppice system with repeated clear cuts at intervals of 20 years was practiced until the end of the 19th century. Later coppice systems were replaced either by high forests or a coppice with standards system. In this study, the Biome BGC model was used to assess the forest dynamics in two forest management systems practiced in Austria. Daily meteorological data and site characteristics were used as model input. Model outputs on net primary production (kgC.ha-1), carbon sequestration (kgC.m-2) and nitrogen volatilisation (kgN.m-2) were analysed. Model results show that high forest and coppice with standards systems significantly vary on production and eventually the contribution to global warming. Increasing production and C sequestration is also linked with increasing N2O emissions from the forest. Only considering the management effects on carbon sequestration will be misleading. Based on this study, it is suggested that trade-off between carbon sequestration and nitrogen volatilisation should be considered to assess the impacts of forest management.

Controls on the production of organohalogens by phytoplankton: Effect of nitrate concentration and grazing

Using a number of laboratory culture experiments we have been able to show that trace gas release by phytoplankton is affected by changes in ambient nitrate conditions. Nutrient concentrations are fundamentally important to phytoplankton community structure and primary production, so it is important to understand if changes in nitrate levels are likely to affect metabolic processes. Recent human activities have added a large quantity of atmospheric nitrogen to the open ocean and this, in turn, will affect both carbon dioxide drawdown and nitrous oxide release. In contrast, ocean prediction models tell us that large parts of the ocean are going to become more oligotrophic. How these changes will affect other climatically active gases, e.g., organohalogens, is unclear. In this study we look at the effect of varying the nitrate to phosphate ratio on the release of three methyl halides. Some attention is also given to the effects of grazing as a means of gas release. Assuming that a 16:1 nitrate:phosphate ratio is the norm, we show that increasing the nitrate level above 16 μmol L−1 can lead to up to an 85% increase in trace gas production per unit cell while lowering the concentration can result in up to a 65% reduction. This is the first time that such a nutrient effect has been observed. Grazing by the microzooplankton Oxyrrhis marina also increases release, but whether this is due to enhanced metabolic processes caused by stress or the breaking down of cells due to grazing is unclear.

Grazing-induced reduction of natural nitrous oxide release from continental steppe

Atmospheric concentrations of the greenhouse gas nitrous oxide (N(2)O) have increased significantly since pre-industrial times owing to anthropogenic perturbation of the global nitrogen cycle, with animal production being one of the main contributors. Grasslands cover about 20 per cent of the temperate land surface of the Earth and are widely used as pasture. It has been suggested that high animal stocking rates and the resulting elevated nitrogen input increase N(2)O emissions. Internationally agreed methods to upscale the effect of increased livestock numbers on N(2)O emissions are based directly on per capita nitrogen inputs. However, measurements of grassland N(2)O fluxes are often performed over short time periods, with low time resolution and mostly during the growing season. In consequence, our understanding of the daily and seasonal dynamics of grassland N(2)O fluxes remains limited. Here we report year-round N(2)O flux measurements with high and low temporal resolution at ten steppe grassland sites in Inner Mongolia, China. We show that short-lived pulses of N(2)O emission during spring thaw dominate the annual N(2)O budget at our study sites. The N(2)O emission pulses are highest in ungrazed steppe and decrease with increasing stocking rate, suggesting that grazing decreases rather than increases N(2)O emissions. Our results show that the stimulatory effect of higher stocking rates on nitrogen cycling and, hence, on N(2)O emission is more than offset by the effects of a parallel reduction in microbial biomass, inorganic nitrogen production and wintertime water retention. By neglecting these freeze-thaw interactions, existing approaches may have systematically overestimated N(2)O emissions over the last century for semi-arid, cool temperate grasslands by up to 72 per cent.

Hydrogen production by nitrogenase as a potential crop rotation benefit

Hydrogen production by nitrogenase as a potential crop rotation benefit

Potential of Municipal Solid Waste for Renewable Energy Production and Reduction of Greenhouse Gas Emissions in South Korea

Energy from waste (EfW) for nonrecyclable wastes is a suitable method of waste management and is important for renewable energy production. South Korea currently recycles 57% of household waste and landfills 26%. The remaining 17% is incinerated, mainly for heat production. In this study, the potential for energy production and reduction of corresponding greenhouse gas (GHG) emissions from municipal solid waste (MSW) in Korea was estimated without accounting for the lifecycle impact of waste management. The properties of the MSW were established from data available in national-scale waste surveys and reports. The potential of EfW for GHG emission reduction was calculated considering (1) the direct release of anthropogenic carbon, nitrous oxide (N2O), and methane (CH4); and (2) the reduction in indirect GHG emissions by fossil fuel displacement. CH4 emissions from landfilling were also estimated from biogenic carbon in waste. Applying the resulting emission factors to various EfW cases suggests that the current level of GHG emissions is significant but can be substantially reduced by increased use of EfW. A net reduction in GHG emissions can be achieved only by EfW with combined heat and power (CHP).

Nitrous oxide and xenon increase noradrenaline release in the cerebral cortex in vivo and in vitro

Noradrenaline in the central nervous system plays an important role in regulating physiological functions, and is a key mechanistic component of general anesthesia. The purpose of this present study was to determine if nitrous oxide and xenon modulate noradrenaline release in the cerebral cortex. We performed a series of in vivo and in vitro experiments in rats. For the in vivo experiments, noradrenaline release was measured by microdialysis in the prefrontal cortex with exposure to 0, 30 or 60% nitrous oxide. For the in vitro experiments, noradrenaline release was measured from cerebrocortical slices before and after incubation with 0, 15, 30, or 60% nitrous oxide in Ca 2+-containing buffer, Ca 2+-free buffer, or in Ca 2+-containing buffer with 10 −6 M tetrodotoxin (TTX). For the in vivo and in vitro experiments 60% xenon was also used. In the in vivo experiment, following exposure to nitrous oxide, noradrenaline release concentration-dependently increased. In the in vitro experiment, under Ca 2+-containing conditions, noradrenaline release from cerebrocortical slices increased significantly during exposure to nitrous oxide in a concentration-dependent manner. Under Ca 2+-free conditions, 60% nitrous oxide produced a significant release of noradrenaline. There were no significant differences in nitrous oxide-increased noradrenaline release between with and without TTX. Xenon also significantly increased noradrenaline release in the prefrontal cortex and from the cerebrocortical slices. The nitrous oxide-induced increase in noradrenaline release may be due to both excitation of the locus coeruleus-noradrenergic neuron and direct stimulation of its axon terminals.

Nitrifier dominance of Arctic soil nitrous oxide emissions arises due to fungal competition with denitrifiers for nitrate

Arctic soils emit nitrous oxide, which is a potent greenhouse gas and also represents an important loss of nitrogen to oligotrophic Arctic ecosystems. However, little is known about the temperature sensitivity of nitrous oxide release in Arctic soils or the organisms mainly responsible for it. We investigated controls on nitrous oxide emissions in an Arctic soil across a typical temperature range (between 4 and 13 °C) on Truelove Lowland, Devon Island, Canada (75°40′N 84°35′W) at two different moisture contents. When fertilized with ammonia or nitrate, nitrous oxide emissions and temperature dependence of nitrous oxide emissions were insensitive to soil moisture content but linked to nitrification rates. Stable isotope analysis revealed that nitrous oxide was predominantly released by nitrifiers. However, nitrous oxide emissions were not linked to nitrifier prevalence with an insignificant ( P < 0.219) increase in amoA genes and a ( P < 0.01) decrease in archaeal nitrifiers. In contrast, denitrifier nosZ prevalence was 10,000 times greater than that of nitrifiers and was related to nitrous oxide emission potential when soils were fertilized with nitrate. Manipulating water-filled pore space should have changed the pattern of N 2O emissions. We used selective inhibitors to further explore why denitrification did not occur under field conditions when we manipulated water-filled pore space or when we used 15N analysis. When fungi were inhibited in the soil, nitrous oxide emissions from denitrifiers increased with no change in nitrous oxide released by nitrifiers. When fungi were active in the soil, there was little available nitrate but when fungi were inhibited, available soil nitrate increased over the incubation period. The dominance of nitrifiers in nitrous oxide emissions from Arctic soils under field conditions is linked to the competition for nitrate between fungi and denitrifiers.

Small scale controls of greenhouse gas release under elevated N deposition rates in a restoring peat bog in NW Germany

Abstract. In Central Europe, most bogs have a history of drainage and many of them are currently being restored. Success of restoration as well as greenhouse gas exchange of these bogs is influenced by environmental stress factors as drought and atmospheric nitrogen deposition. We determined the methane and nitrous oxide exchange of sites in the strongly decomposed center and less decomposed edge of the Pietzmoor bog in NW Germany in 2004. Also, we examined the methane and nitrous oxide exchange of mesocosms from the center and edge before, during, and following a drainage experiment as well as carbon dioxide release from disturbed unfertilized and nitrogen fertilized surface peat. In the field, methane fluxes ranged from 0 to 3.8 mg m−2 h−1 and were highest from hollows. Field nitrous oxide fluxes ranged from 0 to 574 μg m−2 h−1 and were elevated at the edge. A large Eriophorum vaginatum tussock showed decreasing nitrous oxide release as the season progressed. Drainage of mesocosms decreased methane release to 0, even during rewetting. There was a tendency for a decrease of nitrous oxide release during drainage and for an increase in nitrous oxide release during rewetting. Nitrogen fertilization did not increase decomposition of surface peat. Our examinations suggest a competition between vascular vegetation and denitrifiers for excess nitrogen. We also provide evidence that the von Post humification index can be used to explain nitrous oxide release from bogs, if the role of vascular vegetation is also considered. An assessment of the greenhouse gas release from nitrogen saturated restoring bogs needs to take into account elevated release from fresh Sphagnum peat as well as from sedges growing on decomposed peat. Given the high atmospheric nitrogen deposition, restoration will not be able to achieve an oligotrophic ecosystem in the short term.

Group 8 and 10 hyponitrite and dinitrosyl complexes

cis-Hyponitrite complexes L n M(N 2O 2) (M = Ni, Pt; L n = PPh 3, PPh 2Me, dppe, and dppf) of divalent group 10 metals have been previously shown to be readily prepared by treating the corresponding L n MCl 2 derivatives with sodium-( Z)-1-{4-(2,6-di- tert-butyl-4-methoxycyclohexadienonyl)}diazen-1-ium-1,2-diolate. These complexes adopt a diamagnetic square planar geometry with oxygen bound chelating planar cis-hyponitrite ligands. They are readily prepared at room temperature but thermally decompose above 90 °C with release of nitrous oxide. Electrophiles such as iodine, methyltriflate, and hydrochloric acid also react rapidly with the cis-hyponitrite complexes to give nitrous oxide. The structure of one of these previously prepared complexes, (PPh 3) 2Pt(N 2O 2), has been redetermined at −100 °C as a dichloromethane solvate with improved precision. The related tetrahedral group 8 dinitrosyl complexes, (PPh 3) 2M(NO) 2 (M = Ru, Os; L n = PPh 3, dppe, and dppf) have been reexamined and new derivatives with chelating phosphines have been prepared by ligand substitution on the corresponding (PPh 3) 2M(NO) 2. The structures of Ru(dppf)(NO) 2 and Os(dppe)(NO) 2 have been determined. These two analogous families of cis-hyponitrite and dinitrosyl complexes illustrate the balance of metal d n electron count and nitrosyl redox state with one having linear nitrosyls bound to low valent metal centers, and the former having coupled N 2 O 2 2 - ligands bound to a higher oxidation state metal center.

Degradation of CL-20 by white-rot fungi

In previous studies, we found that the emerging energetic chemical, CL-20 (C 6H 6N 12O 12, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), can be degraded following its initial denitration using both aerobic and anaerobic bacteria. The C and N mass balances were not determined due to the absence of labeled starting compounds. The present study describes the degradation of the emerging contaminant by Phanerochaete chrysosporium using ring-labeled [ 15N]-CL-20 and [ 14C]-CL-20. Ligninolytic cultures degraded CL-20 with the release of nitrous oxide (N 2O) in amounts corresponding to 45% of the nitrogen content of CL-20. When ring-labeled [ 15N]-CL-20 was used, both 14N 14NO and 15N 14NO were observed, likely produced from –NO 2 and N–NO 2, respectively. The incubation of uniformly labeled [ 14C]-CL-20 with fungi led to the production of 14CO 2 (>80%). Another ligninolytic fungus, Irpex lacteus, was also able to degrade CL-20, but as for P. chrysosporium, no early intermediates were observed. When CL-20 was incubated with manganese peroxidase (MnP), we detected an intermediate with a [M−H] − mass ion at 345 Da (or 351 and 349 Da when using ring-labeled and nitro-labeled [ 15N]-CL-20, respectively) matching a molecular formula of C 6H 6N 10O 8. The intermediate was thus tentatively identified as a doubly denitrated CL-20 product. The concomitant release of nitrite ions ( NO 2 - ) with CL-20 degradation by MnP also supported the occurrence of an initial denitration prior to cleavage and decomposition.

Filtration increases the correlation between water extractable organic carbon and soil microbial activity

A study was carried out in order to establish the relationship between the water extractable organic carbon (WEOC) content of soils and soil microbial activity, and to determine how variations in the extraction procedure might influence the quantity of WEOC recovered. Concentrations of WEOC were determined in soils taken from 12 different sites in the south east of Scotland, using a procedure in which samples were shaken with distilled water, centrifuged at 5000 g and then filtered through 0.45 μm Millipore filters. Filtration resulted in between 30 and 400 μg C g −1 being extracted using this procedure and the concentration of WEOC in the resultant extracts correlated with soil microbial production of CO 2 and dehydrogenase activity ( P<0.001). Without filtration, although more WEOC was extracted (between 31 and 716 μg C g −1), there was no significant correlation with biological activity. There was also no correlation between WEOC and nitrous oxide release during the incubations. Centrifugation at 20,000 g for at least 10 min prior to filtration was required to remove particulate organic materials. Storage of samples at 4 °C or for up to 1 week or freezing for up to 3 months was not found to have a large influence on the concentration of WEOC in extracts, although amounts increased with soil:extractant ratio and increasing extraction time (from 15 to 60 min).

The release of nitrous oxide from the intertidal zones of two European estuaries in response to increased ammonium and nitrate loading

Nitrous oxide (N2O) release and denitrification rates were investigated from the intertidal saltmarsh and mudflats of two European river estuaries, the Couesnon in Normandy, France and the Torridge in Devon, UK. Sediment cores and water were collected from each study site and incubated for 72 h in tidal simulation chambers. Gas samples were collected at 6 and 12 h intervals from the chambers during incubation. From these N2O emission rates were calculated. The greatest rates for both N2O production and denitrification were measured from saltmarsh cores. These were 1032 µmol N2O m−2 day−1 and 2518 µmol N2 m−2 day−1, respectively, from the Couesnon and 109 µmol N2O m−2 day−1 and 303 µmol N2 m−2 day−1 from the Torridge. A strong positive correlation was apparent with N2O emission rates and ammonium concentration in the sediment, nitrate concentration in floodwater and sediment aerobicity.

The Release of Nitrous Oxide from the Intertidal Zones of Two European Estuaries in Response to Increased Ammonium and Nitrate Loading

The Release of Nitrous Oxide from the Intertidal Zones of Two European Estuaries in Response to Increased Ammonium and Nitrate Loading

Greenhouse Gas Fluxes in Tropical and Temperate Agriculture: The need for a Full-Cost accounting of Global Warming Potentials

Agriculture's contribution to radiative forcing is principally through its historical release of carbon in soil and vegetation to the atmosphere and through its contemporary release of nitrous oxide (N2O) and methane (CHM4). The sequestration of soil carbon in soils now depleted in soil organic matter is a well-known strategy for mitigating the buildup of CO2 in the atmosphere. Less well-recognized are other mitigation potentials. A full-cost accounting of the effects of agriculture on greenhouse gas emissions is necessary to quantify the relative importance of all mitigation options. Such an analysis shows nitrogen fertilizer, agricultural liming, fuel use, N2O emissions, and CH4 fluxes to have additional significant potential for mitigation. By evaluating all sources in terms of their global warming potential it becomes possible to directly evaluate greenhouse policy options for agriculture. A comparison of temperate and tropical systems illustrates some of these options.

Theoretical analysis of the mechanism of nitrous oxide release upon the UV irradiation of binuclear sulfur-containing nitrosyl iron complexes

The B3LYP calculations of binuclear sulfur-containing nitrosyl iron complexes reveal the possibility of photochemical NO ligand 'coupling', which results in the N–N bond formation followed by N2O release in subsequent transformations.