Atmospheric Ammonia Concentrations Research Articles

Symbolic seasonal variation newly found in atmospheric ammonia concentration in urban area of Japan

The NH3(g) concentration measured at multi-site network in Kobe and Kitakyushu, Japan by using passive method continuously for one year in the late 2000s (September 2008–August 2009) and March 2018–February 2019, respectively, was statistically analyzed from the viewpoint of its controlling factors for temporal variation and spatial distribution. Nine survey sites were established in a region of Kobe, where highly urbanized, agricultural and mountainous areas were located within a 20-km x 20-km region; and one site in Kitakyushu, considered as urbanized and industrialized area, was taken into account. In terms of temporal variation, in both areas of Kobe and Kitakyushu, the NH3(g) concentration indicated lower level in the summer than those in other seasons and experienced higher concentration in colder period, which was newly found compared with the conventional wisdom and results in former studies. Regarding spatial distribution, the NH3(g) concentration showed large variations depending on the site, and the annual mean NH3(g) concentration ranged from 0 ppb (not detected: N.D.) to around 5 ppb. The NH3(g) concentration at the mountainous site with high elevation was the lowest, while it was the highest at the site where the contribution of agriculture was noticeably large in the NH3 inventory, followed by commercial and residential areas. The meteorological factors significantly contributed to the specific seasonal variation; moreover, multiple factors such as located situation, acid-base balance in the atmospheric reaction and vehicular emission were mutually related and presumably responsible for the seasonality of higher in the colder season and lower in the warmer season. When the NH3(g) concentration in the urbanized area is discussed, as in our present study area, the proportion of humans and pets (Human&Pet) to the total in the NH3 inventory could be a good parameter to account for the NH3(g) concentration.

Temporal and spatial variability of atmospheric ammonia in the Lombardy region (Northern Italy)

This work investigates the spatial and temporal variability of atmospheric ammonia concentrations in the Lombardy region in Northern Italy, where its continuous measurement at hourly resolution began in 2007 at monitoring sites representative of three different land use areas (urban, rural, and mountain locations). Ammonia concentration data have been jointly analyzed with wind direction and speed to highlight the association between the origin of the air masses and the concentration levels observed at the monitoring sites far from the primary sources, essentially consisting of farming activities and cattle and pigs breeding located in the southeastern part of the Lombardy region. The annual average concentrations of ammonia observed at urban (4.4–13.4 μg m−3 range) and rural (17–35 μg m−3 range) monitoring sites are in substantial agreement with literature data, which are however limited and strongly influenced by the measurement techniques used. The lowest concentration levels (1.1–5.8 μg m−3 range) are observed at the monitoring sites in the mountain areas. Both the seasonal and daily time patterns of the concentrations appear strongly related to some features of the measurement sites, namely with regard to their exposure to agricultural activities, whose seasonal practices arise in emissions responsible for strong variations in the ammonia atmospheric levels. Conversely, in the mountain areas in the north of region, local conditions affecting the atmospheric circulation seem to play a more important role than local sources, with the highest concentrations occurring when the breezes transport NH3-rich air masses from the southern part of the region.

Exploring new methods of estimating deposition using atmospheric concentration measurements: A modeling case study of ammonia downwind of a feedlot

Atmospheric ammonia is an important compound in the atmosphere because of its role in aerosol formation and its importance to the global nitrogen cycle. Livestock feeding operations are a major source of ammonia emissions to the atmosphere, and ammonia concentrations near these large feedlots can be many orders of magnitude higher than background. These feedlots can impact regional ecology and air quality, but uncertainty in the ammonia surface fluxes adjacent to these major sources can make the extent of the feedlot's impact difficult to determine. Ammonia surface fluxes are generally challenging to quantify with direct flux measurement techniques due to the challenges in conducting ammonia measurements with sufficient temporal resolution. Feedlots housing ruminant livestock such as cattle are also sources of methane. Because methane does not undergo appreciable dry deposition and is chemically inert on relevant spatial scales, we can use it as a tracer to constrain the downwind dilution of feedlot ammonia emissions. The ratio of atmospheric ammonia to methane has been shown to decrease with increasing distance downwind of a feedlot due to deposition and aerosol partitioning of gas-phase ammonia. In atmospheric conditions where inorganic aerosol formation is slow, the ratio of ammonia to methane can be used to estimate of the fraction of ammonia that has undergone deposition downwind of the feedlot. We use a Large-Eddy Simulation turbulent dispersion model to generate realistic concentration fields of atmospheric ammonia and methane concentrations downwind of a feedlot, and we sample the model output to produce synthetic measurements of these tracers. We then use the synthetic observations of background-corrected the ammonia:methane concentration ratio to derive the ammonia deposition rate. In this study, we explore conducting measurements from two platforms: sensors deployed on a small unmanned aerial vehicle and on a surface-based mobile observation platform. We find that the surface-based platform overestimates of ammonia deposition by a factor of 1.5 due to sampling near the surface where ammonia concentrations are depleted. However, use of the aerial platform allows more accurate estimation of the deposition fraction (relative error <0.09).

Optimal Interpolation for Infrared Products from Hyperspectral Satellite Imagers and Sounders

Thermal infrared remote sensing measurements have greatly improved in terms of spectral, spatial, and temporal resolution. These improvements are producing a clearer picture of the land surface and Earth atmospheric composition than ever before. Nevertheless, the analysis of this big quantity of data presents important challenges due to incomplete temporal and spatial recorded information. The aim of the present paper is to discuss a methodology to retrieve missing values of some interesting geophysical variables on a spatial field retrieved from spatially scattered infrared satellite observations in order to yield level 3, regularly gridded, data. The technique is based on a 2-Dimensional (2D) Optimal Interpolation (OI) scheme and is derived from the broad class of Kalman filter or Bayesian estimation theory. The goodness of the approach has been tested on 15-min temporal resolution Spinning Enhanced Visible and Infrared Imager (SEVIRI) emissivity and surface temperature (ST) products over South Italy (land and sea), on Infrared Atmospheric Sounding Interferometer (IASI) atmospheric ammonia () concentration over North Italy and carbon monoxide (), sulfur dioxide () and concentrations over China. All these gases affect air quality. Moreover, sea surface temperature (SST) retrievals have been compared with gridded data from MODIS (Moderate-resolution Imaging Spectroradiometer) observations. For gases concentration we have considered data from 3 different emission inventories, that is, Emissions Database for Global Atmospheric Research v3.4.2 (EDGARv3.4.2), the Regional Emission inventory in ASiav3.1 (REASv3.1) and MarcoPolov0.1, plus an independent study. The results show the efficacy of the proposed strategy to better capture the daily cycle for surface parameters and to detect hotspots of severe emissions from gas sources affecting air quality such as and and, therefore, to yield valuable information on the variability of gas concentration to complete ground stations measurements.

Performance of the MAN ammonia monitoring network in the Netherlands

Abstract Since 2005, the Measuring Ammonia in Nature network (MAN, man.rivm.nl) has monitored atmospheric ammonia concentrations monthly in nature reserves in The Netherlands, particularly in Natura2000 areas. Measurements are taken on a hybrid basis using commercial Gradko passive samplers at 280 locations that are calibrated monthly against high-performance instruments at 6 locations. Here we present the calibration procedure, an evaluation of the influence of meteorology on the measurements and how the passive samplers perform in the field. The design was demonstrated to be effective as it combines the strengths of the two measurement methods. The low cost and easy applicability of the samplers allow for the creation of a very extensive network, even covering locations that are difficult to reach. Owing to the calibration with the reference instrument, the accuracy of the passive samplers was considerably improved. Here we update the uncertainty due to the calibration procedure as presented by Lolkema et al. (2015) by including the leave-one-out method. For yearly values this uncertainty becomes [ 0.30 2 + ( 0.06 ⋅ conc ) 2 ] μg/m3.

Unprecedented Atmospheric Ammonia Concentrations Detected in the High Arctic From the 2017 Canadian Wildfires

AbstractFrom 17–22 August 2017 simultaneous enhancements of ammonia (NH3), carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were detected from ground‐based solar absorption Fourier transform infrared (FTIR) spectroscopic measurements at two high‐Arctic sites: Eureka (80.05°N, 86.42°W) Nunavut, Canada, and Thule (76.53°N, 68.74°W), Greenland. These enhancements were attributed to wildfires in British Columbia and the Northwest Territories of Canada using FLEXPART back‐trajectories and fire locations from Moderate Resolution Imaging Spectroradiometer (MODIS) and found to be the greatest observed enhancements in more than a decade of measurements at Eureka (2006–2017) and Thule (1999–2017). Observations of gas‐phase NH3 from these wildfires illustrate that boreal wildfires may be a considerable episodic source of NH3 in the summertime high Arctic. Comparisons of GEOS‐Chem model simulations using the Global Fire Assimilation System (GFASv1.2) biomass burning emissions to FTIR measurements and Infrared Atmospheric Sounding Interferometer (IASI) measurements showed that the transport of wildfire emissions to the Arctic was underestimated in GEOS‐Chem. However, GEOS‐Chem simulations showed that these wildfires contributed to surface layer NH3 and NH enhancements of 0.01–0.11 ppbv and 0.05–1.07 ppbv, respectively, over the Canadian Archipelago from 15–23 August 2017.

Spatioseasonal Variations of Atmospheric Ammonia Concentrations Over the United States: Comprehensive Model‐Observation Comparison

AbstractAtmospheric ammonia plays an important role in a number of environmental issues, including new particle formation and aerosol indirect radiative forcing. Over the United States, atmospheric ammonia has seen an increasing trend due in most part to the declining SO2 and NOx emissions. We conduct the first comprehensive assessment of multiyear Goddard Earth Observing System (GEOS)‐Chem simulated ammonia concentration ([NH3]) over conterminous United States along with surface observations from all 90 National Atmospheric Deposition Program Ammonia Monitoring Network (AMoN) sites that have at least 2 years of continuous measurements. Model‐simulated [NH3] is along empirically expected lines with regard to temporal trends, seasonal variations, and spatial distribution. GEOS‐Chem‐simulated [NH3], compared to AMoN observed values, has weighted average correlation (τ) of 0.50 ± 0.15 and mean fractional bias (MFB) of −8.8 ± 56%. Most sites (63 out of 90) have −60% &lt; MFB &lt; +60%. The deviations from observed values vary spatially and seasonally, and there is significant wintertime underestimation (−44 ± 58%) across most of conterminous United States (except the Pacific states). The largest positive deviations occur in the Pacific states (101 ± 46%) and the largest negative deviations in the Southern Plain states (−73 ± 39%) and the Mountain states (−73 ± 84%), both in the winter months. Over the Great Plains region, GEOS‐Chem simulated [NH3] shows a much stronger dependence to emissions than AMoN observed [NH3], indicating scope for improved representation of emissions for the region. Over Southeast United States, there appears to be the strong effect of the changing emissions of SO2 and NOx in both modeled and observed [NH3].

Effects of Low-level Occupational Exposure to Ammonia on Hematological Parameters and Kidney Function.

Background: Many workers, particularly those working in manufacture of fertilizers, explosives, rubber, pesticides, textiles, and employees of petrochemical industries are exposed to ammonia in their workplaces. Toxic responses of hematopoietic system and kidney following occupational exposure to this chemical have not been thoroughly investigated. Objective: To determine the relationship between long-term occupational exposure to low levels of ammonia and hematological parameters and kidney function. Methods: In this cross-sectional study, 119 randomly selected, male petrochemical workers and 131 office employees (comparison group) were examined. Urine and blood samples were taken from all participants for urinalysis, complete blood count (CBC), serum calcium level, and blood urea nitrogen (BUN) and plasma creatinine. Personal, environmental, and peak ammonia exposure were also measured. Results: The median personal, environmental, and peak occupational exposure to ammonia were 0.23, 0.16, and 65.50 mg/m3, respectively, among the exposed group. No significant difference was observed between the exposed and unexposed participants in terms of hematological parameters and urinalysis. Conversely, calcium and BUN, while within the normal range, were significantly higher in the exposed than in the comparison group. Conclusion: Occupational exposure to low atmospheric concentrations of ammonia was associated with subtle, sub-clinical, pre-pathologic changes in kidney function. Possible longterm consequences and ramifications of these effects require further investigation.

Bacillus amyloliquefaciens spray improves the growth performance, immune status, and respiratory mucosal barrier in broiler chickens

Studies have shown that supplementing probiotics in a nasal spray can provide prophylaxis against upper respiratory tract infections. Previously, we found that spraying with Bacillus reduced the concentration of atmospheric ammonia and airborne microbiological aerosols in broiler houses. In the present study, we evaluated the effects of spraying with Bacillus amyloliquefaciens on the respiratory mucosal barrier in broilers. Two trails were conducted simultaneously in four environmentally controlled chambers. In each trail, 320 1-d-old male broilers were randomly assigned to control (CON) and B. amyloliquefaciens (BAQ) group. Eight cages containing 20 birds per cage were placed in two chambers. The BAQ group chambers were sprayed with B. amyloliquefaciens at 4 × 109 CFU/m2 each day for 42 d. Spraying with B. amyloliquefaciens increased average daily gain and average daily feed intake in broilers (P < 0.01), but had no effects on FCR (P > 0.05). The relative weights of the bursa (21 d) and spleen (42 d) were higher in the BAQ group (P < 0.05). The serum IgG, IgM (21 d), and IgA, Ig M (42 d) levels were improved in BAQ group (P < 0.05). The sIgA levels in tracheal lavage fluid were significantly higher in the BAQ group than the CON group (P < 0.05). Furthermore, treatment with BAQ downregulated IL-6 and IFN-γ (P < 0.05), but upregulated IL-2, occludin, and mucin-2 (P < 0.05). In addition, the number of acidic goblet cells was significantly higher in the tracheas of treated broilers than untreated broilers (P < 0.05). In conclusion, spraying with B. amyloliquefaciens may help to enhance the growth performance and improve the respiratory mucosal barrier in broiler chickens.

Trends in Atmospheric Ammonia and Particulate Ammonium Concentrations in Japan

Trends in Atmospheric Ammonia and Particulate Ammonium Concentrations in Japan

Long-Term Trend of Gaseous Ammonia Over the United States: Modeling and Comparison With Observations.

The concentrations of atmospheric ammonia ([NH3]) have been observed to be increasing over the United States in the last decade, especially in Eastern United States. It is important to understand this temporal trend and variation due to the role of NH3 in particle formation and its ecological effects. Here the long‐term trend of [NH3] over the United States is investigated using GEOS‐Chem, a global 3‐D tropospheric chemistry model, and is corroborated with empirical evidence from the Ammonia Monitoring Network. Model simulations, consistent with observations, show increase in [NH3] over the United States from 2001 to 2016, with magnitude largest in the East (~5% to 12%/year) and smallest in the West (~0% to 5%/year). Reasons for this are examined, and evidence for the role of decreasing SO2 and NOx emissions in increasing [NH3] is provided. The contributions of meteorology and NH3 emission changes to the [NH3] increase appear to be small during the period. Our sensitivity study suggests that decreasing SO2 and NOx emissions over the United States owing to stringent regulations explain about 2/3 and 1/3 of the increase in [NH3], respectively. This effect is different for various NH3 and SO2 and NOx regimes. Given the continued reduction of SO2 and NOx emissions due to U.S. regulations mainly aimed at PM2.5 reduction, the present results are important towards better assessing the environmental impact of emission controlling policies.

Are tissue concentrations of Hylocomium splendens a good predictor of nitrogen deposition?

Emissions from fossil fuel combustion and intensive agriculture have led to a significant increase in global atmospheric concentrations of reactive nitrogen (Nr). Traditional monitoring networks do not capture the high spatial variability of Nr emissions sources; as such, pleurocarpous moss species have been used as a biomonitor for Nr deposition. Tissue concentrations of nitrogen (%N) in the moss species Hylocomium splendens at more than 100 locations in Ireland were used in conjunction with environmental variables (e.g., mean temperature (°C), sun hours, rain (mm), distance to coast) to determine predictive models of total nitrogen (N) deposition (kg N ha −1 yr −1 ) and atmospheric ammonia (NH 3 ) concentrations (μg m −3 ). Tissue N concentrations ranged from 0.5 to 1.2%, with an average of 0.8%; concentrations showed a (low−high) gradient from the west (Atlantic) coast to the east coast. Univariate regression analysis showed that %N tissue concentrations and environmental variables had similar spatial trends and associations. Tissue N concentrations had a stronger relationship with total N deposition compared with atmospheric NH 3 (R 2 = 0.2, p < 0.001; R 2 = 0.1, p < 0.001, respectively). The best predictive model (based on backwards stepwise multiple regression, with model selection based on corrected Akaike Information Criterion) for total N deposition included tissue N concentrations; however, the model for atmospheric NH 3 only included environmental variables (Total N deposition: R 2 = 0.61, p < 0.001; atmospheric NH 3 : R 2 = 0.73, p < 0.001). Sampling strategies involving pleurocarpous moss species have the potential to inform traditional monitoring networks towards improved spatial mapping of N deposition. • Hylocomium splendens was evaluated as a biomonitor of reactive nitrogen deposition. • Tissue N concentrations showed a significant positive relationship with total N deposition. • Moss biomonitoring could improve the spatial analysis of N deposition from traditional networks.

Model Evaluation based on a Relationship Analysis between the Emission and Concentration of Atmospheric Ammonia in the Kanto Region of Japan

Model Evaluation based on a Relationship Analysis between the Emission and Concentration of Atmospheric Ammonia in the Kanto Region of Japan

Analysis of atmospheric ammonia concentration from four sites in Quebec City region over 2010–2013

This study presents an analysis of atmospheric ammonia (NH3) concentration from four different sites located in the Portneuf municipality and Quebec City over 2010–2013 years. The determination of NH3 concentration was performed using passive samplers. Seasonal Mann-Kendall test at 5% significance level was used to analyse the trend in each of the sites. Results showed slight increases and decreases in NH3 concentration, but the trend was not significant (α = 0.05) from 2010 to 2013 in all the evaluated sites. The annual average concentration of the evaluated sites fluctuated from 0.35 to 17.51 μg/m3. Thus, due to that the annual average concentration of NH3 in sites 1 to 3 was higher than 1 μg/m3, which is considered as the critical value for protecting of sensible vegetation close to emission source of NH3. It is suggested to extend the measurements for a longer period and increase the number of sites in order to follow the trends of atmospheric NH3 concentration at local and regional scale and have information about the NH3 concentration trend in Quebec.

Eco-physiological response of Hypnum cupressiforme Hedw. to increased atmospheric ammonia concentrations in a forest agrosystem

Ammonia (NH3) emissions are linked to eutrophication, plant toxicity and ecosystem shifts from N to P limitation. Bryophytes are key components of terrestrial ecosystems, yet highly sensitive to N deposition. Hence, physiological responses of mosses may be indicative of NH3-related impacts, and thus useful to foresee future ecosystem damages and establish atmospheric Critical Levels (CLEs). In this work, samples of Hypnum cupressiforme Hedw. were seasonally collected along a well-defined NH3 concentration gradient in an oak woodland during a one-year period. We performed a comprehensive evaluation of tissue chemistry, stoichiometry, metabolic enzymes, antioxidant response, membrane damages, photosynthetic pigments, soluble protein content and N and C isotopic fractionation. Our results showed that all the physiological parameters studied (except P, K, Ca and C) responded to the NH3 gradient in predictable ways, although the magnitude and significance of the response were dependent on the sampling season, especially for enzymatic activities and pigments content. Nutritional imbalances, membrane damages and disturbance of cellular C and N metabolism were found as a consequence to NH3 exposure, being more affected the mosses more exposed to the barn atmosphere. These findings suggested significant implications of intensive farming for the correct functioning of oak woodlands and highlighted the importance of seasonal dynamics in the study of key physiological processes related to photosynthesis, mosses nutrition and responses to oxidative stress. Finally, tissue N showed the greatest potential for the identification of NH3-related ecological end points (estimated CLE=3.5μgm−3), whereas highly scattered physiological responses, although highly sensitive, were not suitable to that end.

Atmospheric ammonia concentration modulates soil enzyme and microbial activity in an oak forest affecting soil microbial biomass

The present work was carried out to assess the effect of atmospheric ammonia (NH3) on soil physicochemical properties, soil enzymatic activities (β-glucosidase -β-GLU-, nitrate reductase –NR-, urease –UR-, protease –PRO-, acid phosphatase –PHO-, dehydrogenase –DHA-), soil microbial biomass and soil respiration. The study was conducted along a NH3 gradient in a Q. pubescens Milld. forest in the vicinity of two livestock farms. Because of NHy (NHy: NH3 and NH4+) deposition, N saturation was detected up to 330 m from the farms. This excess of N led to a decrease in soil C:N and an increase in soil nitrification processes, which resulted in an accumulation of the heavy N isotope (15N) in the soil. N saturation was also reflected in the activity of NR enzyme, which was inhibited. On the other hand, while UR enzyme was inhibited close to the farms possibly due to the high amount of N-NH4+ resulting from the hydrolysis of NH3, PRO activity was stimulated by the presence of organic nitrogen compounds and the need of soil organisms to meet the C demand. In addition, the activity of PHO and β-GLU enzymes was regulated by the relative amount of C and P that organisms need. Regarding biological variables, enhanced NH3 reduced soil microbial biomass and biomass respiratory efficiency. Finally, soil enzyme activities and soil microbial biomass have proved to be good biological indicators of soil quality.

A volatile discourse – reviewing aspects of ammonia emissions, models and atmospheric concentrations in The Netherlands

AbstractIn the Netherlands, there is a vigorous debate on ammonia emissions, atmospheric concentrations and deposition between stakeholders and research institutions. In this article, we scrutinise some aspects of the ammonia discourse. In particular, we want to improve the understanding of the methodology for handling experimentally determined ammonia emissions. We show that uncertainty in published results is substantial. This uncertainty is under‐ or even unreported, and as a result, data in national emission inventories are overconfident by a wide margin. Next, we demonstrate that the statistical handling of data on atmospheric ammonia concentrations to produce national yearly atmospheric averages is oversimplified and consequently atmospheric concentrations are substantially overestimated. Finally, we show that the much‐discussed ‘ammonia gap’ – either the discrepancy between calculated and measured atmospheric ammonia concentrations or the difference observed between estimated NH3 emission levels and those indicated by atmospheric measurements – is an expression of the widespread overconfidence placed in atmospheric modelling.

Increased atmospheric ammonia over the world's major agricultural areas detected from space.

This study provides evidence of substantial increases in atmospheric ammonia (NH3) concentrations (14-year) over several of the worlds major agricultural regions, using recently available retrievals from the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. The main sources of atmospheric NH3 are farming and animal husbandry involving reactive nitrogen ultimately derived from fertilizer use; rates of emission are also sensitive to climate change. Significant increasing trends are seen over the US (2.61% yr-1), the European Union (EU) (1.83% yr-1), and China (2.27% yr-1). Over the EU, the trend results from decreased scavenging by acid aerosols. Over the US, the increase results from a combination of decreased chemical loss and increased soil temperatures. Over China, decreased chemical loss, increasing temperatures, and increased fertilizer use all play a role. Over South Asia, increased NH3 emissions are masked by increased SO2 and NOx emissions, leading to increased aerosol loading and adverse health effects.

Modelling trends in ammonia in the Netherlands over the period 1990–2014

This study investigates to what extent emissions of ammonia, physicochemical processes and meteorology affect the trend in the atmospheric ammonia in the Netherlands between 1993 and 2014. Two distinct periods were distinguished: a period of declining ammonia concentrations between 1993 and 2004 and a period of slightly increasing ammonia concentrations between 2005 and 2014. In the first period, large emission reductions were reported, while the second period is characterized by smaller emission reductions. The Operational Priority Substances (OPS) model was used to quantify the effects of meteorology and physicochemical processes on atmospheric ammonia concentrations. The general performance of the OPS model for ammonia concentration, ammonium concentration and wet deposition of ammonia/ammonium is quite good when evaluated with observations over the whole period. For the period 1993–2004, model sensitivity runs show that the change in atmospheric chemical conditions and specific meteorological conditions can largely explain the smaller decline in ammonia concentrations compared with the decline in ammonia emissions. Uncertainties in emissions such as changes in the timing of manure applications and uncertainties in the estimated excretion and grazing emissions might partly explain remaining differences at the beginning of the period. Low-emission manure spreading techniques have an important reducing effect on the atmospheric ammonia concentration. Without these techniques, the ammonia concentrations at the measurement stations would have been about 3.5–4 μg m−3 higher in recent years. In the period between 2005 and 2014 emissions declined at a much lower rate, but the observed concentrations increased slightly. One third of the observed difference in trends can again be explained by the changed chemical conditions while no explanation has yet been found for the rest.

Trends in ammonia measurements in the Netherlands over the period 1993–2014

We present measurements of atmospheric concentrations of ammonia and ammonium in the Netherlands over the period 1993–2014 and measurements of wet deposition of ammonium for 1985–2014. The various time series have been obtained at 16 monitoring stations from the Dutch National Air Quality Monitoring Network. The monitoring stations are geographically homogenously spread over the Netherlands and are equally distributed over regions with relatively low, moderate and high ammonia emission.During the period covered, changes in the monitoring have occurred. To obtain consistent time series, data are revalidated or corrected when necessary, according to current validation procedures or latest technical insights. The time series of ammonia concentrations are gap filled and time series corrected for meteorological influences are constructed.The course in the ammonia concentrations shows roughly two periods. For 1993–2004, the ammonia concentrations show a downward trend of 36%, which is statistically significant with a confidence interval (CI) of 99%. For 2005–2014, an upward trend of 19% (CI 90%) is reported. Correcting time series of ammonia concentrations for meteorological influences enhances the statistical reliability of the derived trends. This resulted in trends of −40% (CI 99%) and 24% (CI 95%) respectively. For the full period there exists no trend in ammonia concentrations due to a trend in atmospheric conditions. For 2005–2014 ammonia concentrations increased especially in springtime, while showing no change in winter months. After correcting for meteorological influences, all seasons in this period show an increase in ammonia concentrations although the increase in the spring months is still the largest.For 1993–2014 the reported ammonia emissions in the Netherlands declined in both periods with respectively 51% and 22%. The trends in emissions and ammonia concentrations correspond in the period 1993–2004 whilst over the period 2005–2014, the trends in emissions and concentrations of ammonia diverge. This divergence is for roughly a third accounted for by processes related to changes in chemical climate (see accompanying modelling paper by Wichink Kruit et al., 2016) but it is not clear what explains the remaining difference in trends.For 1993–2014, downward trends of wet deposition of ammonium and ammonium in aerosol are found to be 47% and 68%, respectively. A split into two periods is not found as is the case with the ammonia concentration. However, although statistically not significant, both wet deposition of ammonium and ammonium in aerosol show a leveling off in decline between 2005 and 2014.