Deposition Of Nitrogen Compounds Research Articles

Modelled atmospheric contribution to nitrogen eutrophication in the English Channel and the southern North Sea

Eutrophication of the coastal waters results in algal blooms which may be harmful to the marine ecosystem and coastal economy. The main sources of nutrients are the rivers but an unquantified amount of nitrogen is also transported from ground sources via the atmosphere and deposited to the sea directly by rain and turbulent diffusion. A Lagrangian Particle Dispersion (LPD) model based on the open source code FLEXPART (http://flexpart.eu) is described that quantifies the dissolved nitrogen coming from the air in the English Channel and Southern North Sea (the ‘2Seas’ geographical region). The model uses meteorological records, emissions data and LPD computations to simulate the motion and deposition of nitrogen compounds. The emission sources contributing to the deposition are individually identified, and calculated concentrations are compared with ground measurements in selected locations. The highest calculated atmospheric depositions to the sea in the considered region are found to be along the Belgium–Netherlands coast.

Thirty Years of Chemical Changes in Alpine Acid-Sensitive Lakes in the Alps

The subalpine and alpine areas in North-Western Italy and Southern Switzerland (Canton Ticino) receive high deposition of atmospheric pollutants transported from emission sources in the Po Valley. Long-term studies on high-altitude lakes in these areas indicate widespread recovery from acidification, even though most of them are still substantially affected, especially by deposition of nitrogen compounds. We analysed long-term trends of the major chemical compounds in a sample (n = 41) of high-altitude lakes, both at the site and regional levels, with the aim to assess the response of water chemistry to changes in atmospheric deposition and climate. These lakes have been studied since the early 1980s in the context of research programmes on acidification and atmospheric pollution. The significant decrease of sulfate and acidity in atmospheric deposition led to acidification recovery in the majority of the lakes. However, some lakes are still acidic or show a high sensitivity to acidification. This sensitivity is particularly evident at the snowmelt, when alkalinity is still fully depleted in some lakes. At present, nitrate is the dominant acidifying agent in the studied lakes, due to the high input of nitrogen compounds from atmospheric deposition. Our study also demonstrated that climatic factors interact with atmospheric deposition affecting the long-term changes in lake water.

The status of wet deposition of nitrogen compounds in an intensive dairy farming area in central Japan

(pp. 47–52) The wet deposition of nitrogen compounds in the intensive dairy farming area and its environs in the northern part of the Kanto region in central Japan was investigated from April 2003 to April 2005. Open-bulk samplers were used to collect open-bulk precipitation, which approximates the sum of wet and dry deposition. Furthermore, wet-only samplers were applied to collect the precipitation for every 1 mm in a rainfall, termed the wet sample. The concentrations of total nitrogen and ammonium ions in the open-bulk precipitation were high in the central part of the dairy farming area and low in the remote mountainous area more than 15 km away the concentrations were generally high during winter and spring, and low during summer and autumn. There was a large difference in the annual deposition of nitrogen between the farming area and the surrounding area. The annual deposition of nitrogen in the farming area was significantly high compared to the values of existing data in Japan and Europe. The concentrations of respective nitrogen compounds in the wet sample, which accounted for 40 of the total rainfalls events, were notably high at the beginning of precipitation and rapidly decreased by 8 mm of continuous precipitation. The nitrogen concentrations at the beginning of precipitation were high in the farming area, and relatively low in the surrounding area. It was thought that the cause of the large wet deposition in the farming area was due to ammonia emissions, mainly from cattle manure produced at dairy farms. The factors of the seasonal changes were considered to be the frequency and the amount of precipitation, and the change in ammonia emissions from manure management performed by dairy farmers.

Calculation and mapping of critical loads of sulphur and nitrogen for forest soils in Galicia (NW Spain)

Calculations of critical loads of acidity within Europe have shown Galicia to be one of the regions in Spain with the highest risk of soil acidification by deposition of atmospheric pollutants. We used the simple mass balance method (SMB) to derive critical loads of sulphur and nitrogen for forest soils in Galicia using available site-specific information. Exceedance of acidic deposition was calculated using the deposition levels of N and S registered in 2001. Most forest ecosystems analysed can support acid loads of more than 2000 eq N ha − 1 year − 1 . The lowest critical loads of acidity (1483 eq ha − 1 year − 1 ) occurred in coniferous forest stands growing on shallow soils developed on slates, in the interior zone. The highest critical load values (9386 eq ha − 1 year − 1 ) were observed in coniferous stands in zones with elevated precipitation rates, in the littoral area. The critical load for acidity was exceeded in 5% of the forest soils. Such exceedances were mainly caused by deposition of nitrogen compounds. The contribution of sulphur deposition to acid exceedance was important in the surroundings of the city of A Coruña. Analysis of rainfall bulk composition revealed that N deposition in Galicia was mainly due to ammonium emissions, probably derived from agricultural and cattle breeding activities.

Atmospheric dry deposition in the vicinity of the Salton Sea, California—I: Air pollution and deposition in a desert environment

Abstract Air pollutant concentrations and atmospheric dry deposition were monitored seasonally at the Salton Sea, southern California. Measurements of ozone (O3), nitric acid vapor (HNO3), ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2) and sulfur dioxide (SO2) were performed using passive samplers. Deposition rates of NO3−, NH4+, Cl−, SO42−, Na+, K+ and Ca2+ to creosote bush branches and nylon filters as surrogate surfaces were determined for one-week long exposure periods. Maximum O3 values were recorded in spring with 24-h average values of 108.8 μg m−3. Concentrations of NO and NO2 were low and within ranges of the non-urban areas in California (0.4–5.6 and 3.3–16.2 μg m−3 ranges, respectively). Concentrations of HNO3 (2.0–6.7 μg m−3) and NH3 (6.4–15.7 μg m−3) were elevated and above the levels typical for remote locations in California. Deposition rates of Cl−, SO 4 2 – , Na+, K+ and Ca2+ were related to the influence of sea spray or to suspended soil particles, and no strong enrichments caused by ions originated by human activities were detected. Dry deposition rates of NO 3 – and NH 4 + were similar to values registered in areas where symptoms of nitrogen saturation and changes in species composition have been described. Deposition of nitrogenous compounds might be contributing to eutrophication processes at the Salton Sea.

Past Changes in Arctic Terrestrial Ecosystems, Climate and UV Radiation

At the last glacial maximum, vast ice sheets covered many continental areas. The beds of some shallow seas were exposed thereby connecting previously separated landmasses. Although some areas were ice-free and supported a flora and fauna, mean annual temperatures were 10-13 degrees C colder than during the Holocene. Within a few millennia of the glacial maximum, deglaciation started, characterized by a series of climatic fluctuations between about 18,000 and 11,400 years ago. Following the general thermal maximum in the Holocene, there has been a modest overall cooling trend, superimposed upon which have been a series of millennial and centennial fluctuations in climate such as the "Little Ice Age spanning approximately the late 13th to early 19th centuries. Throughout the climatic fluctuations of the last 150,000 years, Arctic ecosystems and biota have been close to their minimum extent within the most recent 10,000 years. They suffered loss of diversity as a result of extinctions during the most recent large-magnitude rapid global warming at the end of the last glacial stage. Consequently, Arctic ecosystems and biota such as large vertebrates are already under pressure and are particularly vulnerable to current and projected future global warming. Evidence from the past indicates that the treeline will very probably advance, perhaps rapidly, into tundra areas, as it did during the early Holocene, reducing the extent of tundra and increasing the risk of species extinction. Species will very probably extend their ranges northwards, displacing Arctic species as in the past. However, unlike the early Holocene, when lower relative sea level allowed a belt of tundra to persist around at least some parts of the Arctic basin when treelines advanced to the present coast, sea level is very likely to rise in future, further restricting the area of tundra and other treeless Arctic ecosystems. The negative response of current Arctic ecosystems to global climatic conditions that are apparently without precedent during the Pleistocene is likely to be considerable, particularly as their exposure to co-occurring environmental changes (such as enhanced levels of UV-B, deposition of nitrogen compounds from the atmosphere, heavy metal and acidic pollution, radioactive contamination, increased habitat fragmentation) is also without precedent.

Determination of the nitrogen compound balance between the atmosphere and a Norway spruce forest ecosystem

Wet, throughfall and stemflow deposition measurements of nitrogen compounds (NH4 +- and NO3 –-ions) were carried out in a Norway spruce forest in Hungary, together with direct dry deposition and emission estimates (NH3, NO, NO2, HNO3, N2O gases, NH4 + and NO3 – particles). The total deposition of nitrogen compounds from the atmosphere to the forest ecosystem, estimated as the sum of the wet deposition and the measured dry flux, was 1.9 g N m–2 yr–1 for the examined period (1996–1998). The net deposition (difference of the deposition and the emission) was 1.8 g N m–2 yr–1. About 61% of the deposition is due to dry deposition processes. Ammonia gas dominates in the dry deposition (48%). Soil emission of nitric oxide (NO) and nitrous oxide (N2O) constitutes only 5% of the total (wet and dry) deposition. From the comparison of directly measured dry deposition figures and the dry deposition calculated as the difference of the throughfall plus stemflow and wet deposition, it is probable that around 60% of the dry deposited nitrogen compounds (36% of the total, dry and wet deposition) are taken up by stomata, mostly in gaseous form. The remaining part (64%) of the deposited nitrogen compounds is leached to the ground where it is partly taken up by the root system, takes part in the soil mineralisation processes, or leaves the ecosystem by ground or surface water run-off.

Past Changes in Arctic Terrestrial Ecosystems, Climate and UV Radiation

At the last glacial maximum, vast ice sheets covered many continental areas. The beds of some shallow seas were exposed thereby connecting previously separated landmasses. Although some areas were ice-free and supported a flora and fauna, mean annual temperatures were 10–13°C colder than during the Holocene. Within a few millennia of the glacial maximum, deglaciation started, characterized by a series of climatic fluctuations between about 18 000 and 11 400 years ago. Following the general thermal maximum in the Holocene, there has been a modest overall cooling trend, superimposed upon which have been a series of millennial and centennial fluctuations in climate such as the “Little Ice Age spanning approximately the late 13th to early 19th centuries. Throughout the climatic fluctuations of the last 150 000 years, Arctic ecosystems and biota have been close to their minimum extent within the most recent 10 000 years. They suffered loss of diversity as a result of extinctions during the most recent large-magnitude rapid global warming at the end of the last glacial stage. Consequently, Arctic ecosystems and biota such as large vertebrates are already under pressure and are particularly vulnerable to current and projected future global warming. Evidence from the past indicates that the treeline will very probably advance, perhaps rapidly, into tundra areas, as it did during the early Holocene, reducing the extent of tundra and increasing the risk of species extinction. Species will very probably extend their ranges northwards, displacing Arctic species as in the past. However, unlike the early Holocene, when lower relative sea level allowed a belt of tundra to persist around at least some parts of the Arctic basin when treelines advanced to the present coast, sea level is very likely to rise in future, further restricting the area of tundra and other treeless Arctic ecosystems. The negative response of current Arctic ecosystems to global climatic conditions that are apparently without precedent during the Pleistocene is likely to be considerable, particularly as their exposure to co-occurring environmental changes (such as enhanced levels of UV-B, deposition of nitrogen compounds from the atmosphere, heavy metal and acidic pollution, radioactive contamination, increased habitat fragmentation) is also without precedent.

Seasonal NH3 emission estimates for the eastern United States based on ammonium wet concentrations and an inverse modeling method

Significant uncertainty exists in the magnitude and variability of ammonia (NH3) emissions. NH3 emissions are needed as input for air quality modeling of aerosols and deposition of nitrogen compounds. Approximately 85% of NH3 emissions are estimated to come from agricultural nonpoint sources, which are suspected to have a strong seasonal pattern. Because no seasonal information is available in current NH3 emission inventories for air quality modeling, the emissions are often distributed evenly over the year by default. Doing so can adversely affect air quality model‐predicted concentrations of nitrogen‐containing compounds, as shown here. We apply a Kalman filter inverse modeling technique to deduce monthly 1990 NH3 emissions for the eastern United States. The U.S. Environmental Protection Agency (USEPA) Community Multiscale Air Quality (CMAQ) model and ammonium (NH4+) wet concentration data from the National Atmospheric Deposition Program network are used. The results illustrate the strong seasonal differences in NH3 emissions that were anticipated, where NH3 emissions are more than 75% lower during the colder seasons fall and winter as compared to peak emissions during summer. The results also suggest that the current USEPA 1990 National Emission Inventory for NH3 is too high by at least 20%. This is supported by a recent USEPA study of emission factors that proposes lower emission factors for cattle and swine, which are two of the largest sources of NH3 emissions in the inventory.

An integrated biogeochemical model system for the Baltic Sea

The Swedish Meteorological and Hydrological Institute (SMHI) is developing an integrated biogeochemical model system for the Baltic Sea. It consists of three coupled models; a marine biogeochemical-hydrodynamical model (SCOBI), a continuous riverine nitrogen transport model (HBV-N) and an atmospheric transport and chemical model (MATCH). It is supplied with a tool for presentation and analysis. The SCOBI model is a coupled one-dimensional model with high vertical resolution. Horizontal variations are taken into account by dividing the area into smaller boxes. The model includes primary phytoplankton production, nitrogen fixation and secondary zooplankton production. Nitrogen load from land is obtained through the HBV-N model, which simulates organic and inorganic nitrogen separately in catchments. The model is based on the hydrological model HBV, and the subbasin runoff is simulated on a daily basis. The HBV-N model is calibrated and validated against measured concentrations and water flow in rivers. The atmospheric input of oxidised and reduced nitrogen is taken from the annual assessments carried out with the MATCH-Sweden modelling system. MATCH-Sweden combines model calculations, using an atmospheric transport and chemical model, with observations of air- and precipitation chemistry data to give a detailed mapping of concentrations and deposition of nitrogen compounds over Sweden. Supplemented with monitoring data for the specific area of interest, the integrated biogeochemical model system makes a useful tool for environmental protection analyses; e.g. for interpretation of monitoring data as well as creating scenarios for studies of effects in changes of the nutrient loads.

Atmospheric nitrogen input to the Kattegat

Abstract An overview is given of the processes involved in the atmospheric deposition of nitrogen compounds. These processes are incorporated in an atmospheric transport model that is used to calculate the nitrogen input to the Kattegat, the sea area between Denmark and Sweden. The model results show that the total atmospheric nitrogen input to the Kattegat is approximately 960 kg N km2 yr1. The nitrogen input to the Kattegat is dominated by the wet depositions of NHx (42%) and NOy (30%). The contribution from the dry deposition of NHx is 17% and that of the dry deposition of NOy is 11 %. The contribution of the atmospheric input of nitrogen to the Kattegat is about 30% of the total input including the net transport from other sea areas, runoff etc.

Input of atmospheric precipitation nitrogen to the Baltic sea from its catchment

Input of atmospheric precipitation nitrogen (N) to the Baltic sea aquatorium from its drainage basin has been estimated. The deposition of nitrogen compounds on the catchment has been shown to be 5 times higher than their enter directly into the sea. An assessment of this input has been carried out by two methods (direct and indirect) and the results of calculations showed relatively high similarity. It has been demonstrated that the main source of data uncertainty is related to the values of nitrogen runoff and retention in different landuse types. Depending on the subregions the values of atmospheric nitrogen deposition runoff to the Baltic sea changed from 5 up to 16%, the minimum values were obtained for northern subregions and the maximum — for south-western ones. For the whole basin of the Baltic Sea during the 1987–1991 period these runoff values were 8–10% from the total amount of atmospheric nitrogen deposition input (1341–1401 kt) at catchment. The mean value was 122 kt in 1990 yr or 14% of total nitrogen input into the Baltic Sea from all sources. The given values must undoubtedly be taken into account in various scenarios of Transboundary Air Abatement Strategy.

Remarks on the effects of nitrogen deposition to forest ecosystems

The effects of increased deposition of nitrogen compounds on forest sites are discussed based on literature data and own results from both earlier fertilization experiments and the ARINUS study area in the Black Forest. The influence on mycorrhiza is stated suppressive as well as stimulating so that no general conclusion can be drawn. The nitrogen nutrition status of coniferous forests is still sub-optimal over wide areas with a yearly deposition of 10–20 kg N ha-1. Under considerable higher input rates the insufficient supply of other nutrients and imbalances in the nutritional status of trees are possible. When discussing ‘nitrogen saturation’ of ecosystems, the nitrogen storage capacity of soils has to be considered as a decisive factor which varies from site to site. Any actual input/output balance is strongly influenced by the internal turnover processes resulting from former land use.

Temporal evolution of nitrogen compounds in Swedish precipitation since 1955

Nitrate (NO3−) and ammonium (NH4+) ions are important determinants of the ionic strength and pH of precipitation1. The deposition of these ions on vegetation and on the ground also constitutes a significant source of nutrients for plants. This is particularly the case in polluted regions, for example, Europe, where the deposition of nitrogen compounds is enhanced2. There are indications (for example, increased run-off of nitrogen3) that forests in some parts of Europe have reached saturation levels with respect to nitrogen deposition; and excessive wet and dry deposition of nitrogen compounds has been suggested as a possible cause of the extensive damage to forests in Europe4. Data from Rothamsted, UK, indicate that the mean concentration of NO3− in precipitation doubled between the 1850s and I960 (ref. 5); similarly, the NH4+ concentration probably increased between the 1880s and 1960. A review of precipitation chemistry data from Europe indicates an approximately threefold increase in NO3− deposition between the 1890s and the late 1970s6. The present analysis of data from the European Air Chemistry Network reveals that the NO3− concentration at most stations approximately doubled between the late 1950s and early 1970s, with a less pronounced increase in NH4+. Detailed analysis of data from 12 Swedish stations showed no further increase of NO3− or NH4+ between 1972 and 1984. In contrast, the sulphate concentration decreased by ∼30% for the same locations and time period.