Measured and Simulated Nitrous Oxide Emissions from Ryegrass- and Ryegrass/White Clover-Based Grasslands in a Moist Temperate Climate

There is uncertainty about the potential reduction of soil nitrous oxide (N2O) emission when fertilizer nitrogen (FN) is partially or completely replaced by biological N fixation (BNF) in temperate grassland. The objectives of this study were to 1) investigate the changes in N2O emissions when BNF is used to replace FN in permanent grassland, and 2) evaluate the applicability of the process-based model DNDC to simulate N2O emissions from Irish grasslands. Three grazing treatments were: (i) ryegrass (Lolium perenne) grasslands receiving 226 kg FN ha−1 yr−1 (GG+FN), (ii) ryegrass/white clover (Trifolium repens) grasslands receiving 58 kg FN ha−1 yr−1 (GWC+FN) applied in spring, and (iii) ryegrass/white clover grasslands receiving no FN (GWC-FN). Two background treatments, un-grazed swards with ryegrass only (G–B) or ryegrass/white clover (WC–B), did not receive slurry or FN and the herbage was harvested by mowing. There was no significant difference in annual N2O emissions between G–B (2.38±0.12 kg N ha−1 yr−1 (mean±SE)) and WC-B (2.45±0.85 kg N ha−1 yr−1), indicating that N2O emission due to BNF itself and clover residual decomposition from permanent ryegrass/clover grassland was negligible. N2O emissions were 7.82±1.67, 6.35±1.14 and 6.54±1.70 kg N ha−1 yr−1, respectively, from GG+FN, GWC+FN and GWC-FN. N2O fluxes simulated by DNDC agreed well with the measured values with significant correlation between simulated and measured daily fluxes for the three grazing treatments, but the simulation did not agree very well for the background treatments. DNDC overestimated annual emission by 61% for GG+FN, and underestimated by 45% for GWC-FN, but simulated very well for GWC+FN. Both the measured and simulated results supported that there was a clear reduction of N2O emissions when FN was replaced by BNF

Characteristics of ammonia, acid gases, and PM_2.5 for three typical land-use types in the North China Plain

Air pollution is one of the most serious environmental problems in China due to its rapid economic development alongside a very large consumption of fossil fuel, particularly in the North China Plain (NCP). During the period 2011–2014, we integrated active and passive sampling methods to perform continuous measurements of NH3, HNO3, NO2, and PM2.5 at two urban, one suburban, and two rural sites in the NCP. The annual average concentrations of NH3, NO2, and HNO3 across the five sites were in the ranges 8.5–23.0, 22.2–50.5, and 5.5–9.7 μg m−3, respectively, showing no significant spatial differences for NH3 and HNO3 but significantly higher NO2 concentration at the urban sites. At each site, annual average concentrations of NH3 and NO2 showed increasing and decreasing trends, respectively, while there was no obvious trend in annual HNO3 concentrations. Daily PM2.5 concentrations ranged from 11.8 to 621.0 μg m−3 at the urban site, from 19.8 to 692.9 μg m−3 at the suburban site, and from 23.9 to 754.5 μg m−3 at the two rural sites, with more than 70 % of sampling days exceeding 75 μg m−3. Concentrations of water-soluble ions in PM2.5 ranked differently between the non-rural and rural sites. The three dominant ions were NH4 +, NO3 −, and SO4 2− and mainly existed as (NH4)2SO4, NH4HSO4, and NH4NO3, and their concentrations averaged 48.6 ± 44.9, 41.2 ± 40.8, and 49.6 ± 35.9 μg m−3 at the urban, suburban, and rural sites, respectively. Ion balance calculations indicated that PM2.5 was neutral at the non-rural sites but acidic at the rural sites. Seasonal variations of the gases and aerosols exhibited different patterns, depending on source emission strength and meteorological conditions. Our results suggest that a feasible pathway to control PM2.5 pollution in the NCP should target ammonia and acid gases together

Naar een depositiemonitoring netwerk voor luchtverontreiniging in Europa

In January 1993 within the framework of the LIFE programme a project was financed which aim was to develop a deposition monitoring method for air pollution of Europe. This method should be used to extend existing European monitoring networks of air concentrations to provide deposition inputs on an ecosystem scale. A monitoring station for atmospheric deposition was designed and constructed using existing methods. Three such stations were applied in a pilot project for a year on three sites in different regions in Europe to estimate local inputs and to validate deposition models which are currently developed for estimation of ecosystem-specific deposition in Europe. The results of this project show that the developed deposition monitoring method is successful in determining the deposition of pollutants and can be applied on a routine basis. The equipment for flux measurements provided continuous high quality data for all major gaseous and particulate pollutants throughout the range of pollution climates present in Central and Northern Europe. The monitoring facility was therefore highly successful. The sites selected were representative of the major ecosystems of Europe and the range of air pollution climates (excepting urban areas and Mediterranean regions).In 1993 werd vanuit het LIFE project van de Europese Commissie DG XI het project 'Towards the development of a deposition monitoring network for air pollution of Europe' gefinancierd. Het doel van dit project was het ontwikkelen en implementeren van een depositiemonitoring-methode voor luchtverontreiniging in Europa. Een dergelijke methode zou gebruikt moeten worden als uitbreiding van bestaande Europese monitoring netwerken voor het meten van luchtconcentraties om depositieschattingen op ecosysteem-schaal te kunnen maken. In dit project werd een drietal monitoringstations ontworpen welke op drie plaatsen in Europa gedurende een jaar werden ingezet: Auchencorth, een semi-natuurlijke lage vegetatie in Schotland ; Melpitz, een grasland in Duitsland en Speulder bos, een Douglas sparrenbos in Nederland. Dit rapport beschrijft de eindresultaten van het zogenaamde LIFE project. De resultaten van het project laten zien dat de ontwikkeling van depositiemonitoring-methoden succesvol was en dat routinematige metingen voor de bepaling van de depositie van luchtverontreiniging uitgevoerd kunnen worden. De inzet van de apparatuur op drie lokaties in Europa, representatief voor verschillende condities en ecosystemen, leverde continu hoge kwaliteit gegevens voor de bepaling van de jaargemiddelde deposities. De droge depositie van SO2, NH3 en NOx werd continu gemeten met behulp van de gradientmethode. De evaluaties van parametrisaties voor de uitwisseling van deze componenten met het oppervlak vormden een belangrijk onderdeel van het project, daar deze parametrisaties gebruikt worden voor de bepaling van de depositie van de andere componenten in de zogenaamde inference methode. Er werden systematische afwijkingen gevonden tussen gemodelleerde en gemeten fluxen. Het was echter niet het doel van dit project de modellen te verbeteren. De metingen vormen een goede basis voor modelverbeteringen en zullen in de toekomst daartoe worden geanalyseerd

Naar een depositiemonitoring netwerk voor luchtverontreiniging in Europa

In 1993 werd vanuit het LIFE project van de Europese Commissie DG XI het project 'Towards the development of a deposition monitoring network for air pollution of Europe' gefinancierd. Het doel van dit project was het ontwikkelen en implementeren van een depositiemonitoring-methode voor luchtverontreiniging in Europa. Een dergelijke methode zou gebruikt moeten worden als uitbreiding van bestaande Europese monitoring netwerken voor het meten van luchtconcentraties om depositieschattingen op ecosysteem-schaal te kunnen maken. In dit project werd een drietal monitoringstations ontworpen welke op drie plaatsen in Europa gedurende een jaar werden ingezet: Auchencorth, een semi-natuurlijke lage vegetatie in Schotland ; Melpitz, een grasland in Duitsland en Speulder bos, een Douglas sparrenbos in Nederland. Dit rapport beschrijft de eindresultaten van het zogenaamde LIFE project. De resultaten van het project laten zien dat de ontwikkeling van depositiemonitoring-methoden succesvol was en dat routinematige metingen voor de bepaling van de depositie van luchtverontreiniging uitgevoerd kunnen worden. De inzet van de apparatuur op drie lokaties in Europa, representatief voor verschillende condities en ecosystemen, leverde continu hoge kwaliteit gegevens voor de bepaling van de jaargemiddelde deposities. De droge depositie van SO2, NH3 en NOx werd continu gemeten met behulp van de gradientmethode. De evaluaties van parametrisaties voor de uitwisseling van deze componenten met het oppervlak vormden een belangrijk onderdeel van het project, daar deze parametrisaties gebruikt worden voor de bepaling van de depositie van de andere componenten in de zogenaamde inference methode. Er werden systematische afwijkingen gevonden tussen gemodelleerde en gemeten fluxen. Het was echter niet het doel van dit project de modellen te verbeteren. De metingen vormen een goede basis voor modelverbeteringen en zullen in de toekomst daartoe worden geanalyseerd.In January 1993 within the framework of the LIFE programme a project was financed which aim was to develop a deposition monitoring method for air pollution of Europe. This method should be used to extend existing European monitoring networks of air concentrations to provide deposition inputs on an ecosystem scale. A monitoring station for atmospheric deposition was designed and constructed using existing methods. Three such stations were applied in a pilot project for a year on three sites in different regions in Europe to estimate local inputs and to validate deposition models which are currently developed for estimation of ecosystem-specific deposition in Europe. The results of this project show that the developed deposition monitoring method is successful in determining the deposition of pollutants and can be applied on a routine basis. The equipment for flux measurements provided continuous high quality data for all major gaseous and particulate pollutants throughout the range of pollution climates present in Central and Northern Europe. The monitoring facility was therefore highly successful. The sites selected were representative of the major ecosystems of Europe and the range of air pollution climates (excepting urban areas and Mediterranean regions).DGM EC/DG1

The hidden cost of using low-resolution concentration data in the estimation of NH3 dry deposition fluxes

Abstract Long-term monitoring stations for atmospheric pollutants are often equipped with low-resolution concentration samplers. In this study, we analyse the errors associated with using monthly average ammonia concentrations as input variables for bidirectional biosphere-atmosphere exchange models, which are commonly used to estimate dry deposition fluxes. Previous studies often failed to account for a potential correlation between ammonia exchange velocities and ambient concentrations. We formally derive the exact magnitude of these errors from statistical considerations and propose a correction scheme based on parallel measurements using high-frequency analysers. In case studies using both modelled and measured ammonia concentrations and micrometeorological drivers from sites with varying pollution levels, we were able to substantially reduce bias in the predicted ammonia fluxes. Neglecting to account for these errors can, in some cases, lead to significantly biased deposition estimates compared to using high-frequency instrumentation or corrected averaging strategies. Our study presents a first step towards a unified correction scheme for data from nation-wide air pollutant monitoring networks to be used in chemical transport and air quality models

Land Use Specific Ammonia Deposition Velocities: a Review of Recent Studies (2004–2013)

Abstract Land use specific deposition velocities of atmospheric trace gases and aerosols—particularly of reactive nitrogen compounds—are a fundamental input variable for a variety of depositionmodels. Although the concept is known to have shortcomings—especially with regard to bi-directional exchange—the often limit-ed availability of concentration data and meteorological input variables make it a valuable simplification for regional modeling of deposition fluxes. In order to meet the demand for an up-to-date overview of recent publi-cations on measurements and modeling studies, we compiled a database of ammonia (NH3) deposition ve-locities published from 2004 to 2013. Observations from a total of 42 individual studies were averaged using an objective weighing scheme and classified into seven land use categories. Weighted average and median de-position velocities are 2.2 and 2.1 cm s−1 for coniferous forests, 1.5 and 1.2 cm s−1 for mixed forests, 1.1 and 0.9 cm s−1 for deciduous forests, 0.9 and 0.7 cm s−1 for semi-natural sites, 0.7 and 0.8 cm s−1 for urban sites, 0.7 and 0.6 cm s−1 for water surfaces, and 1.0 and 0.4 cm s−1 for agricultural sites, respectively. Thus, values present-ed in this compilation were considerably lower than those found in former studies (e.g., VDI 2006). Reasons for the mismatch were likely due to different land use classification, different averaging methods, choices of measurement locations, and improvements in measure-ment and in modeling techniques. Both data and code used for processing are made available as supplementa-ry material to this article

Ammonia deposition in the neighbourhood of an intensive cattle feedlot in Victoria, Australia

Intensive cattle feedlots are large emission sources of ammonia (NH(3)), but NH(3) deposition to the landscape downwind of feedlots is not well understood. We conducted the first study in Australia to measure NH(3) dry deposition within 1 km of a commercial beef cattle feedlot in Victoria. NH(3) concentrations and deposition fluxes decreased exponentially with distance away from the feedlot. The mean NH(3) concentrations decreased from 419 μg N m(−3) at 50 m to 36 μg N m(−3) at 1 km, while the mean NH(3) dry deposition fluxes decreased from 2.38 μg N m(−2) s(−1) at 50 m to 0.20 μg N m(−2) s(−1) at 1 km downwind from the feedlot. These results extrapolate to NH(3) deposition of 53.9 tonne N yr(−1) in the area within 1 km from the feedlot, or 67.5 kg N ha(−1) yr(−1) as an area-weighted mean, accounting for 8.1% of the annual NH(3)-N emissions from the feedlot. Thus NH(3) deposition around feedlots is a significant nitrogen input for surrounding ecosystems. Researches need be conducted to evaluate the impacts of NH(3) deposition on the surrounding natural or semi-naturals ecosystems and to reduce N fertilizer application rate for the surrounding crops by considering nitrogen input from NH(3) deposition