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China's rapid urbanization, large population, and increasing consumption of calorie-and meat-intensive diets, have resulted in China becoming the world's largest source of ammonia (NH 3 ) emissions from livestock production. This is the first study to use provincial, condition-specific emission factors based on most recently available studies on Chinese manure management and environmental conditions. The estimated NH 3 emission temporal trends and spatial patterns are interpreted in relation to government policies affecting livestock production. Scenario analysis is used to project emissions and estimate mitigation potential of NH 3 emissions, to year 2030. We produce a 1 km × 1 km gridded NH 3 emission inventory for 2008 based on county-level activity data, which can help identify locations of highest NH 3 emissions. The total NH 3 emissions from manure generated by livestock production in 2008 were 7.3 Tg NH 3 ·yr − 1 (interquartile range from 6.1 to 8.6 Tg NH 3 ·yr − 1 ), and the major sources were poultry (29.9%), pigs (28.4%), other cattle (27.9%), and dairy cattle (7.0%), while sheep and goats (3.6%), donkeys (1.3%), horses (1.2%), and mules (0.7%) had smaller contributions. From 1978 to 2008, annual NH 3 emissions fluctuated with two peaks (1996 and 2006), and total emissions increased from 2.2 to 7.3 Tg·yr − 1 increasing on average 4.4%·yr − 1 . Under a business-as-usual (BAU) scenario, NH 3 emissions in 2030 are expected to be 13.9 Tg NH 3 ·yr − 1 (11.5–16.3 Tg NH 3 ·yr − 1 ). Under mitigation scenarios, the projected emissions could be reduced by 18.9–37.3% compared to 2030 BAU emissions. This study improves our understanding of NH 3 emissions from livestock production, which is needed to guide stakeholders and policymakers to make well informed mitigation decisions for NH 3 emissions from livestock production at the country and regional levels. [ABSTRACT FROM AUTHOR]

The objective of this research is to quantify NH 3 flux above an intensively managed cornfield in the Midwestern United States to improve understanding of NH 3 emissions and evaluations of new and existing emission models. A relaxed eddy accumulation (REA) system was deployed above a corn canopy in central Illinois, USA (40°3′46.209″N, 88° 11′46.0212″W) from May through September 2014 (day of year 115–273) to measure NH 3 fluxes due to chemical fertilizer application. NH 3 flux was measured in four-hour periods during mornings and afternoons. Mean atmospheric NH 3 concentration during the complete measurement period was 2.6 ± 2.0 μg m −3 . Larger upward fluxes of gaseous NH 3 were measured during the first 30 days after fertilization, with variations observed throughout the field campaign. Measured NH 3 fluxes ranged from −246.0 ng m −2 s −1 during wintertime background measurements to 799.6 ng m −2 s −1 within two weeks of fertilization (where negative flux indicates deposition). Mean positive flux was 233.3 ± 203.0 ng m −2 s −1 in the morning and 260.0 ± 253.3 ng m −2 s −1 in the afternoon while mean negative flux was −45.3 ± 38.6 ng m −2 s −1 in the morning and −78.35 ± 74.9 ng m −2 s −1 in the afternoon. NH 3 volatilization during the first 21 days after fertilization accounted for 79% of total nitrogen loss during the growing season. Such measurements are critical to improve understanding of agricultural NH 3 emissions in managed agricultural ecosystems dominated by rotations of highly fertilized corn and moderately to lightly fertilized soybeans, such as the plot studied herein. These measurements are also important to improve understanding of how managed agricultural ecosystems impact air quality, and contribute to the global nitrogen cycle, and to evaluate current NH 3 emission models. [ABSTRACT FROM AUTHOR]

DeNitrification DeComposition (DNDC) model predictions of NH 3 fluxes following chemical fertilizer application were evaluated by comparison to relaxed eddy accumulation (REA) measurements, in Central Illinois, United States, over the 2014 growing season of corn. Practical issues for evaluating closure were addressed by accounting for fluxes outside the measurement site and differences in temporal resolution. DNDC modeled NH 3 fluxes showed no significant differences in magnitude (at p = 0.05) compared to measurements and replicated trends satisfactorily (r a 2 > 0.74), during the initial 33 days after fertilizer application, when measured fluxes were to the atmosphere, compared to later time periods when depositional fluxes were measured (r a 2 < 0.52). Among the model input parameters, NH 3 fluxes were most sensitive to air temperature, precipitation, soil organic carbon, field capacity, pH, and fertilizer application rate, timing, and depth. By constraining these inputs for conditions in Central Illinois, uncertainty in daily NH 3 fluxes was estimated to vary from 0% to 70% on a daily basis, during the corn growing season, with the highest uncertainty values estimated for the period of highest positive NH 3 fluxes. These results can guide future improvements in DNDC, which is a valuable tool to assist (1) in the development of NH 3 emission inventories with high spatial (constrained by the spatial resolution of input parameters) and temporal resolution (daily) and (2) in upscaling emissions from the site (farm) to the regional scale. [ABSTRACT FROM AUTHOR]

The article discusses how global action for the environmentally sound management (ESM) of chemicals is produced at bilateral, regional, and international levels, and examines the development of three agreements to manage hazardous chemicals, in terms of their scope and effectiveness, within a United Nations framework. Topics include an overview of the fundamentals of International Environmental Governance (IEG), such as its use through legally binding multilateral environmental agreements (MEAs), MEA development, and the challenges to MEA use. A comparison of three MEAs for the management of hazardous chemicals, including those outlined at the Basel Convention in 1989, the Rotterdam Convention in 1998, and the Stockholm Convention in 2001, is presented.

Highlights • Inter-comparison of relaxed eddy accumulation and flux gradient measurements. • Strong correlation between the two NH 3 flux measurement methods. • Peak NH 3 flux measured with both systems six days after fertilizer application. • Two elevated emission periods influenced by urease inhibitor and environmental conditions. Abstract Studies of NH 3 flux over agricultural ecosystems in the USA are limited by low temporal resolution (typically hours or days) and sparse spatial coverage, with no studies over corn in the Midwest USA. We report on NH 3 flux measurements over a corn canopy in Central Illinois, USA, using the relaxed eddy accumulation (REA) and flux gradient (FG) methods, providing measurements at 4 h and 0.5 h intervals, respectively. The REA and FG systems were operated for the duration of the 2014 corn-growing season. Flux-footprint analysis was used to select data from both systems, resulting in 82 concurrent measurements. Mean NH 3 flux of concurrent measurements was 205 ± 300 ng m−2 s−1 from REA and 110 ± 256 ng m−2 s−1 from FG for all concurrent samples. Results from both methods were not significantly different at a 95% confidence level for all concurrent measurements. The FG system resolved NH 3 emission peaks at 0.5 h averaging time that were otherwise un-observed with 4 h REA averaging. Two early-season peak emission periods were identified (DOY 130-132 and 140-143), where the timing and intensity of such emissions were attributed to a combination of urease inhibitor, applied as a field-management decision, and localized soil temperature and precipitation. Given the dependence of NH 3 fluxes on multiple parameters, this study further highlights the need for increased spatial coverage and high temporal resolution (e.g., <1 h) of measurements to better understand the impact of agricultural NH 3 emissions on air quality and the global nitrogen cycle. Such measurements are also needed for evaluation of models describing surface-atmosphere exchange of NH 3. [ABSTRACT FROM AUTHOR]

Abstract Due to the contributions of nitrous oxide (N 2 O) to global climate change and stratospheric ozone destruction, it is important to understand how climate and agricultural management affect N 2 O emissions. Although the process-based Denitrification Decomposition (DNDC) model is often used for quantifying emissions of N 2 O, the accuracy of these predictions remains in question, and it is not clear which input variables, environmental or field management, have the greatest effect on model performance. In this study, DNDC was evaluated for prediction of N 2 O fluxes from two climatically-different corn-field sites in the United States (a Colorado irrigated field and a Minnesota rainfed field). Besides climate, these sites offer the additional advantage that measurements are available for multiple field management practices, including fertilizer application, tillage, and crop rotation. This evaluation found that DNDC did not consistently, correctly predict daily-scale N 2 O fluxes. Cumulative growing season N 2 O fluxes were significantly under-predicted in Colorado and were both under- and over-predicted in Minnesota. Model calibration of four soil input parameters did not significantly improve N 2 O emission predictions at either site or time scale. Modeled and measured N 2 O fluxes and model error were all strongly correlated with precipitation. Over-predictions of N 2 O fluxes were associated with heavy precipitation and high modeled denitrification. Based on our results, model improvements to decrease model error for corn cropping systems in temperate climate zones should focus on better accounting for the effects of precipitation on denitrification. Despite discrepancies in daily and cumulative growing season N 2 O fluxes, DNDC correctly identified the only field management (fertilizer application rate) that significantly influenced the measured N 2 O fluxes. Graphical abstract Unlabelled Image Highlights • DNDC was evaluated for agricultural N 2 O under different management and climates. • DNDC correctly identified field management that significantly influenced N 2 O fluxes. • DNDC did not predict daily and cumulative N 2 O fluxes well, even after calibration. • N 2 O fluxes and model error correlated with precipitation frequency and intensity. • Model improvements should focus on denitrification surrounding precipitation events. [ABSTRACT FROM AUTHOR]

Emission factors (EFs) of particulate matter with aerodynamic diameter ≤10 µm (PM10) from the open burning/open detonation (OB/OD) of energetic materials were measured using a hybrid-optical remote sensing (hybrid-ORS) method. This method is based on the measurement of range-resolved PM backscattering values with a micropulse light detection and ranging (LIDAR; MPL) device. Field measurements were completed during March 2010 at Tooele Army Depot, Utah, which is an arid continental site. PM10EFs were quantified for OB of M1 propellant and OD of 2,4,6-trinitrotoluene (TNT). EFs from this study are compared with previous OB/OD measurements reported in the literature that have been determined with point measurements either in enclosed or ambient environments, and with concurrent airborne point measurements. PM10mass EFs, determined with the hybrid-ORS method, were 7.8 × 10−3kg PM10/kg M1 from OB of M1 propellant, and 0.20 kg PM10/kg TNT from OD of TNT. Compared with previous results reported in the literature, the hybrid-ORS method EFs were 13% larger for OB and 174% larger for OD. Compared with the concurrent airborne measurements, EF values from the hybrid-ORS method were 37% larger for OB and 54% larger for OD. For TNT, no statistically significant differences were observed for the EFs measured during the detonation of 22.7 and 45.4 kg of TNT, supporting that the total amount of detonated mass in this mass range does not have an effect on the EFs for OD of TNT. [ABSTRACT FROM AUTHOR]

Cover cropping is beneficial for reducing soil erosion and nutrient losses, but there are conflicting reports on how cover cropping affects emissions of nitrous oxide (N 2 O), a potent greenhouse gas. In this study, we measured N 2 O fluxes over a full year in Illinois corn plots with and without rye cover crop. We compared these year-round measurements to N 2 O emissions predicted by the Intergovernmental Panel on Climate Change (IPCC) Tier 1 equation and the Denitrification-Decomposition (DNDC) model. In addition, we measured potential denitrification and N 2 O production rates. The field measurements showed typical N 2 O peaks shortly after fertilizer application, as well as a significant late-winter peak. Cover cropping significantly reduced all peak N 2 O fluxes, with decreases ranging from 39 to 95%. Neither model was able to accurately predict annual N 2 O fluxes or the decrease in N 2 O emissions from cover-cropped fields. In contrast to field measurements, lab assays found that cover cropping significantly increased potential denitrification by 90–127% and potential N 2 O production by 54–106%. The rye cover-cropped plots had lower soil nitrate and higher soil carbon. When limiting nitrate and excess carbon were provided in lab assays, the proportion of N 2 O resulting from denitrification decreased. These results suggest that the discrepancy between the observed decrease in field N 2 O emissions and the increase in denitrification potential may be due to the difference in available nutrients between the field and laboratory measurements. Overall, these results suggest the importance of late-winter peaks in N 2 O emissions and the potential of rye cover cropping to reduce N 2 O emissions from agricultural fields. Unlabelled Image • Assessed cover cropping effects on agricultural nitrous oxide emissions • Conducted field and laboratory measurements of soils and gases and modeling • Rye cover cropping showed potential to reduce nitrous oxide emissions. • Models did not consistently predict the observed decrease in emissions. • Cover cropping increased denitrifying and nitrous oxide production potential in lab. [ABSTRACT FROM AUTHOR]

Highlights • Modeling the bi-directional NH 3 exchange at the field scale using SURFATM-NH 3. • Integrating an operational parameterization of emission potentials in the model. • Parameterizing the effect of urease inhibitor on NH 3 volatilization. • Satisfactory simulations of NH 3 fluxes by integrating the effect of urease inhibitor. • Good predictions of dynamic and order of magnitude of emission potentials by the model. Abstract Agriculture is the main source of ammonia (NH 3) emissions in the atmosphere. NH 3 is precursor to secondary fine particulate matter, which is of concern for its impacts on health and visibility. There are a limited number of field measurements of NH 3 emissions from fertilizer application in the US, and this limits our understanding of the importance of individual NH 3 source and sink processes in controlling timing and magnitude of NH 3 emissions. In this study, a new parameterization of the effect of urease inhibitor on NH 3 emissions from urea-based fertilizer was developed on the basis of experimental results found in the literature. This parameterization was combined with an existing operational parameterization of soil and stomatal emission potentials (Γ g , Γ s) and was implemented in a surface-atmosphere transfer model for NH 3 (SURFATM-NH 3) in order to evaluate the bi-directional fluxes of NH 3 at the field scale. The model was evaluated with field measurements obtained by the flux-gradient (FG) and relaxed eddy accumulation (REA) methods in a fertilized corn field in central Illinois. By integrating the effect of urease inhibitor, the timing of the highest NH 3 emission peak was successfully predicted and its magnitude was close to that measured (predicted 2106 ng m−2 s−1, measured by FG 2312 ± 582 ng m−2 s−1). Based on the model results, urease inhibitor has a considerable effect on the dynamics and order of magnitude of NH 3 fluxes. Furthermore, the model simulated the inhibiting action of N- (n -butyl) thiophosphoric (nBTPT) and suggests that it can reduce NH 3 volatilization by 32%. The model also successfully predicted environmental parameters, such as soil temperature. Finally, this new version of SURFATM-NH 3 is a valuable tool to estimate the NH 3 bi-directional fluxes at the field scale, which describes dynamic modeling of Γ s and Γ g by taking into account the effect of urease inhibitor which is commonly used in the US to improve the efficiency of urea fertilizers. [ABSTRACT FROM AUTHOR]