Causes of Large Increases in Atmospheric Ammonia in the Last Decade across North America (original) (raw)
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Trends in atmospheric ammonia at urban, rural and remote sites across North America
Atmospheric Chemistry and Physics Discussions
Interannual variabilities in atmospheric ammonia (NH<sub>3</sub>) during the most recent seven to eleven years were investigated at fourteen sites across North America using the monitored data obtained from NAPS, CAPMoN and AMoN networks. The long-term average of atmospheric NH3 ranged from 0.8 to 2.6 ppb, depending on location, at four urban and two rural/agriculture sites in Canada. The annual average at these sites did not show any deceasing trend with largely decreasing anthropogenic NH<sub>3</sub> emission. An increasing trend was actually identified from 2003 to 2014 at the downtown Toronto site using either the Mann-Kendall or the Ensemble Empirical Mode Decomposition method, but “no” or “stable” trends were identified at other sites. The ~20 % increase during the 11-year period at the site was likely caused by changes in NH<sub>4</sub><sup>+</sup>/NH<sub>3</sub> partitioning and/or air-surface exchange process as a ...
Atmospheric Environment, 2016
Emissions of NH 3 are assessed to be nearly constant in the USA from 2008 to 2014. NH 3 air concentrations and precipitation NH 4 þ show increasing trends over a large area of the USA from 2008 to 2015. Particulate NH 4 þ , NO 3 À and SO 4 2À show decreasing trends in these regions. Declining NOx and SO 2 emissions provide less H 2 SO 4 and HNO 3 for neutralization of NH 3 in the atmosphere. Greater NH 3 concentrations may change the spatial pattern of N deposition.
Interannual Variability of Ammonia Concentrations over the United States: Sources and Implications
Atmospheric Chemistry and Physics Discussions, 2016
The variability of atmospheric ammonia (NH<sub>3</sub>), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM<sub>2.5</sub>) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008–2012). We find that the model generally underrepresents the ammonia concentration near large source regions and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO<sub>2</sub> and NO<sub>...
Biogeosciences, 2013
Weekly/biweekly concentrations of atmospheric NH 3 were collected using passive samplers at 74 sites across southern Ontario, Canada during the period from June 2006 to March 2007 with tens of sites running as early as March 2006. The annual average of NH 3 (AAN) at all the sites across southwestern Ontario was over 1 µg m −3 , a value that was recently proposed as the new critical level for protecting vegetation. High ANN values (3.6-6.1 µg m −3) were observed at eight sites located inside the intensive livestock production zones. The AAN values at the sites across southeastern Ontario were generally less than 1 µg m −3 and the values were less than 0.4 µg m −3 at non-agricultural sites. Regional transport from the southwest region to the southeast region was identified to be the main contributor to the observed NH 3 at the southeastern non-agricultural sites. However, different transport mechanisms were proposed in different seasons. The transport of NH 3 produced through bi-directional air-surface exchange along air mass trajectories was believed to be the main mechanism in the hot seasons while the transport of NH 4 NO 3 produced at source locations followed by its evaporation at receptor sites was thought to be dominant in the cold seasons. A sharp increase in NH 3 concentration was surprisingly observed at 20 out of the 74 sites during the coldest two weeks when ambient temperature was lower than −7 • C, and cannot be explained by known sources or with existing knowledge. Recently developed NH 3 emission inventory for southern Ontario was also evaluated with the measurement data and emissions within two small zones were identified to be potentially underestimated. 1 Introduction Atmospheric ammonia (NH 3) is an important reactive nitrogen compound in the geosphere and biosphere of the earth. NH 3 gas has been found to cause direct adverse effects on plant community composition even at low concentration levels and the value 12774 BGD
Drivers for spatial, temporal and long-term trends in atmospheric ammonia and ammonium in the UK
Atmospheric Chemistry and Physics Discussions, 2017
A unique long-term dataset from the UK National Ammonia Monitoring Network (NAMN) is used here to assess spatial, seasonal and long-term variability in atmospheric ammonia (NH<sub>3</sub>: 1998–2014) and particulate ammonium (NH<sub>4</sub><sup>+</sup>: 1999–2014) across the UK. Extensive spatial heterogeneity in NH<sub>3</sub> concentrations is observed, with lowest annual mean concentrations at remote sites (< 0.2 μg m<sup>−3</sup>) and highest in the areas with intensive agriculture (up to 22 μg m<sup>−3</sup>), while NH<sub>4</sub><sup>+</sup> concentrations show less spatial variability (e.g. range of 0.14 to 1.8 μg m<sup>−3</sup> annual mean in 2005). Temporally, NH<sub>3</sub> concentrations are influenced by environmental conditions and local emission sources. In part...
Monthly Patterns of Ammonia Over the Contiguous United States at 2‐km Resolution
Geophysical Research Letters
Atmospheric NH 3 emissions are principally from agricultural activities, including the volatilization of agricultural waste and fertilizer application in managed croplands (Bouwman et al., 1997; Paulot et al., 2014). Agricultural NH 3 emissions significantly degrade air quality with impacts on human health through ammoniated aerosol formation (Hill et al., 2019; Paulot & Jacob, 2014). With respect to climate, ammonium nitrate (NH 4 NO 3) aerosols have a direct radiative forcing of −0.5 W m −2 over the central United States (Hauglustaine et al., 2014) and are increasingly important at the global scale (Paulot et al., 2018). Despite the recognized importance of NH 3 , observations of the spatiotemporal variabilities of NH 3 are limited, largely due to the extreme difficulties of measuring gas-phase NH 3 (Fehsenfeld et al., 2002; von Bobrutzki et al., 2010). The Ammonia Monitoring Network (AMoN) (NADP, 2020; Puchalski et al., 2015) consists of the only routine measurements of biweekly NH 3 across the United States (19 sites in 2010; 107 sites in January 2020). Large differences of NH 3 magnitudes and seasonalities exist at short distances between Abstract Monthly, high-resolution (∼2 km) ammonia (NH 3) column maps from the Infrared Atmospheric Sounding Interferometer (IASI) were developed across the contiguous United States and adjacent areas. Ammonia hotspots (95th percentile of the column distribution) were highly localized with a characteristic length scale of 12 km and median area of 152 km 2. Five seasonality clusters were identified with k-means++ clustering. The Midwest and eastern United States had a broad, spring maximum of NH 3 (67% of hotspots in this cluster). The western United States, in contrast, showed a narrower midsummer peak (32% of hotspots). IASI spatiotemporal clustering was consistent with those from the Ammonia Monitoring Network. CMAQ and GFDL-AM3 modeled NH 3 columns have some success replicating the seasonal patterns but did not capture the regional differences. The high spatialresolution monthly NH 3 maps serve as a constraint for model simulations and as a guide for the placement of future, ground-based network sites. Plain Language Summary Ammonia (NH 3) contributes to the formation of particulate matter, which is known to degrade air quality and human health. The major source of NH 3 is from agricultural activities, yet observational constraints on NH 3 are limited, particularly at both monthly resolution and high spatial resolution. We have developed high spatial resolution (2 km) satellite maps of NH 3 on a monthly scale in the United States. Areas with the highest NH 3 are generally very localized with typical length scales of ∼12 km. The seasonal patterns varied dramatically based upon the underlying agricultural activities. These high-resolution satellite maps can be used as observational constraints on the seasonalities and spatial patterns for modeling of atmospheric NH 3. WANG ET AL.
Environmental Research Letters, 2021
Excess atmospheric ammonia (NH3) leads to deleterious effects on biodiversity, ecosystems, air quality and health, and it is therefore essential to monitor its budget and temporal evolution. Hyperspectral infrared satellite sounders provide daily NH3 observations at global scale for over a decade. Here we use the version 3 of the Infrared Atmospheric Sounding Interferometer (IASI) NH3 dataset to derive global, regional and national trends from 2008 to 2018. We find a worldwide increase of 12.8 ± 1.3 % over this 11-year period, driven by large increases in east Asia (5.80 ± 0.61% increase per year), western and central Africa (2.58 ± 0.23 % yr−1), North America (2.40 ± 0.45 % yr−1) and western and southern Europe (1.90 ± 0.43 % yr−1). These are also seen in the Indo-Gangetic Plain, while the southwestern part of India exhibits decreasing trends. Reported national trends are analyzed in the light of changing anthropogenic and pyrogenic NH3 emissions, meteorological conditions and the ...
Atmospheric Environment, 2008
Accurate estimates of ammonia (NH 3) emissions are needed for reliable predictions of fine particulate matter (PM 2.5) by air quality models (AQMs), but the current estimates contain large uncertainties in the temporal and spatial distributions of NH 3 emissions. In this study, the US EPA Community Multiscale Air Quality (CMAQ) modeling system is applied to study the contributions of the agriculture-livestock NH 3 (AL-NH 3) emissions to the concentration of PM 2.5 and the uncertainties in the total amount and the temporal variations of NH 3 emissions and their impact on the formation of PM 2.5 for August and December 2002. The sensitivity simulation results show that AL-NH 3 emissions contribute significantly to the concentration of PM 2.5 , NH 4 + , and NO 3 À ; their contributions to the concentrations of SO 4 2À are relatively small. The impact of NH 3 emissions on PM 2.5 formation shows strong spatial and seasonal variations associated with the meteorological conditions and the ambient chemical conditions. Increases in NH 3 emissions in August 2002 resulted in 410% increases in the concentrations of NH 4 + and NO 3 À ; reductions in NH 3 emissions in December 2002 resulted in 420% decreases in their concentrations. The large changes in species concentrations occur downwind of the high NH 3 emissions where the ambient environment is NH 3-poor or neutral. The adjustments in NH 3 emissions improve appreciably the model predictions of NH 4 + and NO 3 À both in August and December, but resulted in negligible improvements in PM 2.5 in August and a small improvement in December, indicating that other factors (e.g., inaccuracies in meteorological predictions, emissions of other primary species, aerosol treatments) might be responsible for model biases in PM 2.5 .