Annual Average NO Research Articles

PM2.5 and NOX concentrations decrease as a result of a railway electrification.

This work examines the impact of the electrification of the Holon-Bat Yam passenger train line (central Israel) on air pollutant concentrations using data collected from air quality monitoring stations that operated at the train stations across the electrified train line. We present statistically significant reduction in the annual average NO2, NO and NOX concentrations (29-45%, 79-85% and 65-75%, respectively), attributed to the electrification of the passenger train line. The drop in the NO and NOX concentrations was much stronger than in the NO2 concentrations, since NO is the main nitrogen species emitted by diesel locomotives. PM2.5 concentrations also significantly decreased, but only in two (out of the three) train stations situated along the electrified line. Following various analyses, we conclude that electrification of train lines reduces train locomotive emissions and improves the air quality at the stations, as expected, thus protecting the passengers and reducing their exposure to air pollutants. Although this study presents a specific case, the findings are expected to be applicable, at least quantitatively, to other locations, as railway electrification removes emissions associated with fossil-fuel-powered locomotives. This work supports railway electrification policy, which has the potential to substantially lower air pollution levels and diminish the passengers' exposure to harmful air pollutants.

Traffic NO<sub>x</sub> Pollution Prediction and Health Cost Estimation Using Machine Learning: A Case Study of Toronto, Canada

Road traffic is a significant source of air pollution that has a harmful impact on human health. To reduce the health and environmental impacts of fossil fuel consumption in the transportation sector, many countries have implemented policies to promote the deployment of electric vehicles (EVs). A vital factor to consider when designing policies to support EV use is the monetized health impacts of fossil fuel consumption. This research aims to investigate the health benefit of replacing internal combustion engine vehicles (ICEVs) with zero-emission vehicles in the city of Toronto, Canada. A long short-term memory (LSTM) model is developed in this work to predict future NO<sub>x</sub> concentrations considering the effect of the traffic volume, weather, time of day, and historical NO<sub>x</sub> concentrations. The developed model is then used to predict long-term NO<sub>x</sub> concentrations and annual average NO<sub>x</sub> reduction from zero-emission vehicle deployment in four different scenarios in Toronto. Additionally, interpolation methods are used to predict the pollution reduction in all Dissemination Areas (DA) of Toronto, and a health cost assessment is conducted to estimate the health benefit in all the scenarios. The results of the modeling in this work show that the western areas of Toronto experience higher NO<sub>x</sub> concentration reduction in all scenarios. These reductions are the result of the higher correlation between traffic volume and pollution in those areas. The results also show that with a 10% reduction in ICEV traffic volume, 70 premature deaths can be prevented annually, equivalent to 560 million CAD in health benefits per year.

Analysis of the distributions of hourly NO2 concentrations contributing to annual average NO2 concentrations across the European monitoring network between 2000 and 2014

Abstract. Exposure to nitrogen dioxide (NO2) is associated with negative human health effects, both for short-term “peak” concentrations and from long-term exposure to a wider range of NO2 concentrations. For the latter, the European Union has established an air quality limit value of 40 µg m−3 as an annual average. However, factors such as proximity and strength of local emissions, atmospheric chemistry, and meteorological conditions mean that there is substantial variation in the hourly NO2 concentrations contributing to an annual average concentration. The aim of this analysis was to quantify the nature of this variation at thousands of monitoring sites across Europe through the calculation of a standard set of “chemical climatology” statistics. Specifically, at each monitoring site that satisfied data capture criteria for inclusion in this analysis, annual NO2 concentrations, as well as the percentage contribution from each month, hour of the day, and hourly NO2 concentrations divided into 5 µg m−3 bins were calculated. Across Europe, 2010–2014 average annual NO2 concentrations (NO2AA) exceeded the annual NO2 limit value at 8 % of > 2500 monitoring sites. The application of this “chemical climatology” approach showed that sites with distinct monthly, hour of day, and hourly NO2 concentration bin contributions to NO2AA were not grouped into specific regions of Europe, furthermore, within relatively small geographic regions there were sites with similar NO2AA, but with differences in these contributions. Specifically, at sites with highest NO2AA, there were generally similar contributions from across the year, but there were also differences in the contribution of peak vs. moderate hourly NO2 concentrations to NO2AA, and from different hours across the day. Trends between 2000 and 2014 for 259 sites indicate that, in general, the contribution to NO2AA from winter months has increased, as has the contribution from the rush-hour periods of the day, while the contribution from peak hourly NO2 concentrations has decreased. The variety of monthly, hour of day and hourly NO2 concentration bin contributions to NO2AA, across cities, countries and regions of Europe indicate that within relatively small geographic areas different interactions between emissions, atmospheric chemistry and meteorology produce variation in NO2AA and the conditions that produce it. Therefore, measures implemented to reduce NO2AA in one location may not be as effective in others. The development of strategies to reduce NO2AA for an area should therefore consider (i) the variation in monthly, hour of day, and hourly NO2 concentration bin contributions to NO2AA within that area; and (ii) how specific mitigation actions will affect variability in hourly NO2 concentrations.

Quantifying and reducing the water footprint of rain-fed potato production part II: a hydrological assessment using modelling supported by measurements

Abstract Water footprinting (WF) is mooted to quantify the impacts of production on water resources. The impact of the rain-fed potato ( Solanum tuberosum) production on water resources was assessed for a kilogram of potatoes at the packhouse gate. The hydrological water-balance method was used and this accounts for all inflows and outflows to quantify the net use of groundwater as the blue WF, and that of the soil-water store as the green WF. The green WF was found to be negligible. The blue WF was negative at −67 L/kg. Thus rain-fed potato production here has no deleterious impacts on the water quantity. The grey WF, the water required to ‘dilute’ NO 3 –N in the drainage to meet the drinking water standard, was 61 L/kg, of which 56 L/kg was from the cropping stage. The impact of the packhouse phase and the background system was found to be small. However, the average leached NO 3 –N concentration of 11.3 mg/L, which is just at the drinking water standard, and the loading of 27.8 kg-N/ha/y during cultivation indicate that a single application of fertilizer at the time of planting has impacts on water quality. Our modelling of different fertilizer application scenarios of two splits, three splits and a late application at 55 days after planting reduced the annual average NO 3 –N concentrations to 10.5, 10.3 and 9.5 mg/L respectively. Potato yield was not compromised. The grey WF would be reduced to 50.6, 50.9 and 48.9 L/kg respectively for these fertilizer scenarios.

Long-term effects on the nitrogen budget of a short-rotation grey alder ( Alnus incana (L.) Moench) forest on abandoned agricultural land

Short-rotation energy forestry is one of the potential ways for management of abandoned agricultural areas. It helps sequestrate carbon and mitigate human-induced climate changes. Owing to symbiotic dinitrogen (N 2) fixation by actinomycetes and the soil fertilizing capacity and fast biomass growth of grey alders, the latter can be suitable species for short-rotation forestry. In our study of a young grey alder stand ( Alnus incana (L.) Moench) on abandoned arable land in Estonia we tested the following hypotheses: (1) afforestation of abandoned agricultural land by grey alder significantly affects the soil nitrogen (N) status already during the first rotation period; (2) input of symbiotic fixation covers an essential part of the plant annual N demand of the stand; (3) despite a considerable N input into the ecosystem of a young alder stand, there will occur no significant environmental hazards (N leaching or N 2O emissions). The first two hypotheses can be accepted: there was a significant increase in N and C content in the topsoil (from 0.11 to 0.14%, and from 1.4 to 1.7%, respectively), and N fixation (151.5 kg N ha −1 yr −1) covered about 74% of the annual N demand of the stand. The third hypothesis met support as well: N 2O emissions (0.5 kg N ha −1 yr −1) were low, while most of the annual gaseous N losses were in the form of N 2 (73.8 kg N ha −1 yr −1). Annual average NO 3–N leaching was 15 kg N ha −1 yr −1 but the N that leached from topsoil accumulated in deeper soil layers. The soil acidifying effect of alders was clearly evident; during the 14-year period soil acidity increased 1.3 units in the upper 0–10 cm topsoil layer.

Application of air pollution dispersion modeling for source-contribution assessment and model performance evaluation at integrated industrial estate-Pantnagar

Source-contribution assessment of ambient NO 2 concentration was performed at Pantnagar, India through simulation of two urban mathematical dispersive models namely Gaussian Finite Line Source Model (GFLSM) and Industrial Source Complex Model (ISCST-3) and model performances were evaluated. Principal approaches were development of comprehensive emission inventory, monitoring of traffic density and regional air quality and conclusively simulation of urban dispersive models. Initially, 18 industries were found responsible for emission of 39.11 kg/h of NO 2 through 43 elevated stacks. Further, vehicular emission potential in terms of NO 2 was computed as 7.1 kg/h. Air quality monitoring delineates an annual average NO 2 concentration of 32.6 μg/m 3. Finally, GFLSM and ISCST-3 were simulated in conjunction with developed emission inventories and existing meteorological conditions. Models simulation indicated that contribution of NO 2 from industrial and vehicular source was in a range of 45–70% and 9–39%, respectively. Further, statistical analysis revealed satisfactory model performance with an aggregate accuracy of 61.9%.

Comparison of the performances of land use regression modelling and dispersion modelling in estimating small-scale variations in long-term air pollution concentrations in a Dutch urban area

The performance of a Land Use Regression (LUR) model and a dispersion model (URBIS – URBis Information System) was compared in a Dutch urban area. For the Rijnmond area, i.e. Rotterdam and surroundings, nitrogen dioxide (NO 2) concentrations for 2001 were estimated for nearly 70 000 centroids of a regular grid of 100 × 100 m. A LUR model based upon measurements carried out on 44 sites from the Dutch national monitoring network and upon Geographic Information System (GIS) predictor variables including traffic intensity, industry, population and residential land use was developed. Interpolation of regional background concentration measurements was used to obtain the regional background. The URBIS system was used to estimate NO 2 concentrations using dispersion modelling. URBIS includes the CAR model (Calculation of Air pollution from Road traffic) to calculate concentrations of air pollutants near urban roads and Gaussian plume models to calculate air pollution levels near motorways and industrial sources. Background concentrations were accounted for using 1 × 1 km maps derived from monitoring and model calculations. Moderate agreement was found between the URBIS and LUR in calculating NO 2 concentrations ( R = 0.55). The predictions agreed well for the central part of the concentration distribution but differed substantially for the highest and lowest concentrations. The URBIS dispersion model performed better than the LUR model ( R = 0.77 versus R = 0.47 respectively) in the comparison between measured and calculated concentrations on 18 validation sites. Differences can be understood because of the use of different regional background concentrations, inclusion of rather coarse land use category industry as a predictor variable in the LUR model and different treatment of conversion of NO to NO 2. Moderate agreement was found between a dispersion model and a land use regression model in calculating annual average NO 2 concentrations in an area with multiple sources. The dispersion model explained concentrations at validation sites better.

The effects of congestions tax on air quality and health

The “Stockholm Trial” involved a road pricing system to improve the air quality and reduce traffic congestion. The test period of the trial was January 3–July 31, 2006. Vehicles travelling into and out of the charge cordon were charged for every passage during weekdays. The amount due varied during the day and was highest during rush hours (20 SEK = 2.2 EUR, maximum 60 SEK per day). Based on measured and modelled changes in road traffic it was estimated that this system resulted in a 15% reduction in total road use within the charged cordon. Total traffic emissions in this area of NO x and PM10 fell by 8.5% and 13%, respectively. Air quality dispersion modelling was applied to assess the effect of the emission reductions on ambient concentrations and population exposure. For the situations with and without the trial, meteorological conditions and other emissions than from road traffic were kept the same. The calculations show that, with a permanent congestion tax system like the Stockholm Trial, the annual average NO x concentrations would be lower by up to 12% along the most densely trafficked streets. PM10 concentrations would be up to 7% lower. The limit values for both PM10 and NO 2 would still be exceeded along the most densely trafficked streets. The total population exposure of NO x in Greater Stockholm (35 × 35 km with 1.44 million people) is estimated to decrease with a rather modest 0.23 μg m −3. However, based on a long-term epidemiological study, that found an increased mortality risk of 8% per 10 μg m −3 NO x , it is estimated that 27 premature deaths would be avoided every year. According to life-table analysis this would correspond to 206 years of life gained over 10 years per 100 000 people following the trial if the effects on exposures would persist. The effect on mortality is attributed to road traffic emissions (likely vehicle exhaust particles); NO x is merely regarded as an indicator of traffic exposure. This is only the tip of the ice-berg since reductions are expected in both respiratory and cardiovascular morbidity. This study demonstrates the importance of not only assessing the effects on air quality limit values, but also to make quantitative estimates of health impacts, in order to justify actions to reduce air pollution.

In Situ Bioreactors and Deep Drain‐Pipe Installation to Reduce Nitrate Losses in Artificially Drained Fields

Nitrate in water removed from fields by subsurface drain ('tile') systems is often at concentrations exceeding the 10 mg N L(-1) maximum contaminant level (MCL) set by the USEPA for drinking water and has been implicated in contributing to the hypoxia problem within the northern Gulf of Mexico. Because previous research shows that N fertilizer management alone is not sufficient for reducing NO(3) concentrations in subsurface drainage below the MCL, additional approaches are needed. In this field study, we compared the NO(3) losses in tile drainage from a conventional drainage system (CN) consisting of a free-flowing pipe installed 1.2 m below the soil surface to losses in tile drainage from two alternative drainage designs. The alternative treatments were a deep tile (DT), where the tile drain was installed 0.6 m deeper than the conventional tile depth, but with the outlet maintained at 1.2 m, and a denitrification wall (DW), where trenches excavated parallel to the tile and filled with woodchips serve as additional carbon sources to increase denitrification. Four replicate 30.5- by 42.7-m field plots were installed for each treatment in 1999 and a corn-soybean rotation initiated in 2000. Over 5 yr (2001-2005) the tile flow from the DW treatment had annual average NO(3) concentrations significantly lower than the CN treatment (8.8 vs. 22.1 mg N L(-1)). This represented an annual reduction in NO(3) mass loss of 29 kg N ha(-1) or a 55% reduction in nitrate mass lost in tile drainage for the DW treatment. The DT treatment did not consistently lower NO(3) concentrations, nor reduce the annual NO(3) mass loss in drainage. The DT treatment did exhibit lower NO(3) concentrations in tile drainage than the CN treatment during late summer when tile flow rates were minimal. There was no difference in crop yields for any of the treatments. Thus, denitrification walls are able to substantially reduce NO(3) concentrations in tile drainage for at least 5 yr.

Spatial analysis of annual air pollution exposure and mortality

The aim of this study was to relate ambient air pollution levels to mortality in Auckland, New Zealand. We used urban airshed modelling and GIS-based techniques to quantify long-term exposure to ambient air pollution levels and associated mortality. After adjusting for age, sex, ethnicity, socio-economic status, and urban/rural domicile there was a 1.3% (95%CI: 1–1.5%) increase in non-external cause mortality, and 1.8% (95%CI: 1.5–2.1%) increase in circulatory and respiratory causes per 1 μg/m 3 increase in annual average NO 2 . Based on these exposure–response relationships and applying an annual average threshold of 13 μg/m 3 , the average annual (for 1996–1999) number of people estimated to die from non-external causes and circulatory and respiratory causes attributable to air pollution in Auckland is 268 (95% range: 227–310) (3.9% of total all cause deaths) and 203 (95% range: 169–237) (5.9% of total circulatory and respiratory deaths) per year, respectively. The number of attributable deaths found in this study are consistent with a previous New Zealand risk assessment using a different methodology, and is approximately twice the number of people dying from motor vehicle accidents in the region, which is on average (1996-1999) 103 per year. The GIS-based exposure maps identify high exposure areas for policy developers and planners in a simple and realistic manner. Taken together with overseas studies the study provides additional evidence that long-term exposure to poor air quality, even at levels below current standards, is a hazard to the public health.

Spatial analysis of annual air pollution exposure and mortality

The aim of this study was to relate ambient air pollution levels to mortality in Auckland, New Zealand. We used urban airshed modelling and GIS-based techniques to quantify long-term exposure to ambient air pollution levels and associated mortality. After adjusting for age, sex, ethnicity, socio-economic status, and urban/rural domicile there was a 1.3% (95%CI: 1–1.5%) increase in non-external cause mortality, and 1.8% (95%CI: 1.5–2.1%) increase in circulatory and respiratory causes per 1 μg/m 3 increase in annual average NO 2. Based on these exposure–response relationships and applying an annual average threshold of 13 μg/m 3, the average annual (for 1996–1999) number of people estimated to die from non-external causes and circulatory and respiratory causes attributable to air pollution in Auckland is 268 (95% range: 227–310) (3.9% of total all cause deaths) and 203 (95% range: 169–237) (5.9% of total circulatory and respiratory deaths) per year, respectively. The number of attributable deaths found in this study are consistent with a previous New Zealand risk assessment using a different methodology, and is approximately twice the number of people dying from motor vehicle accidents in the region, which is on average (1996-1999) 103 per year. The GIS-based exposure maps identify high exposure areas for policy developers and planners in a simple and realistic manner. Taken together with overseas studies the study provides additional evidence that long-term exposure to poor air quality, even at levels below current standards, is a hazard to the public health.

Atmospheric concentrations of ammonia and ammonium at an agricultural site in the southeast United States

In this study, we present ∼1 yr (October 1998–September 1999) of 12-hour mean ammonia (NH 3), ammonium (NH 4 +), hydrochloric acid (HCl), chloride (Cl −), nitrate (NO 3 −), nitric acid (HNO 3), nitrous acid (HONO), sulfate (SO 4 2−), and sulfur dioxide (SO 2) concentrations measured at an agricultural site in North Carolina's Coastal Plain region. Mean gas concentrations were 0.46, 1.21, 0.54, 5.55, and 4.15 μg m −3 for HCl, HNO 3, HONO, NH 3, and SO 2, respectively. Mean aerosol concentrations were 1.44, 1.23, 0.08, and 3.37 μg m −3 for NH 4 +, NO 3 −, Cl −, and SO 4 2−, respectively. Ammonia, NH 4 +, HNO 3, and SO 4 2− exhibit higher concentrations during the summer, while higher SO 2 concentrations occur during winter. A meteorology-based multivariate regression model using temperature, wind speed, and wind direction explains 76% of the variation in 12-hour mean NH 3 concentrations ( n=601). Ammonia concentration increases exponentially with temperature, which explains the majority of variation (54%) in 12-hour mean NH 3 concentrations. Dependence of NH 3 concentration on wind direction suggests a local source influence. Ammonia accounts for >70% of NH x (NH x =NH 3+NH 4 +) during all seasons. Ammonium nitrate and sulfate aerosol formation does not appear to be NH 3 limited. Sulfate is primarily associated ammonium sulfate, rather than bisulfate, except during the winter when the ratio of NO 3 −–NH 4 + is ∼0.66. The annual average NO 3 −–NH 4 + ratio is ∼0.25.

Regional estimation of pollutant gas dry deposition in the UK: model description, sensitivity analyses and outputs

A “big-leaf” resistance analogy model for dry deposition of sulphur dioxide, nitrogen dioxide, ammonia and nitric acid is described with a stomatal compensation point included to allow bi-directional exchange of ammonia. The model derivation is constrained by measurement data and it is parameterized for UK conditions. Monthly average dry deposition estimates are provided at the 5 km×5 km spatial scale. The model uses data available nationally at the appropriate spatial and temporal scales, such as gas concentration, land use, wind speed, temperature, rainfall and vapour pressure. A method is presented to overcome the lack of suitable solar radiation data. The effect of uncertainty in model inputs and in model parameterization is explored using sensitivity analyses. SO 2 deposition is sensitive to variation in gas concentration, wind speed and wet surface uptake parameters. NO 2 deposition is sensitive to parameters and inputs regulating stomatal behaviour, including solar radiation and temperature, as well as to gas concentration. The use of monthly or annual average NO 2 concentrations may underestimate deposition substantially in some areas. HNO 3 dry deposition is sensitive to wind speed and concentration. NH 3 dry deposition to moorland and forest land uses, where the majority of deposition occurs, is sensitive to concentration, wind speed and choice of canopy resistance parameters. For arable and grassland areas, with both deposition and emission of NH 3, the model is sensitive to all the model inputs and parameter choices. A full uncertainty analysis requires further work on the reliability of input variables and model parameter choices but these results quantitatively focus on the important areas of the model for each gas. Estimated dry deposition to the UK (excluding Northern Ireland) of SO 2 is 135 Gg S yr −1 for 1996, for NH 3 is 97 Gg N yr −1, for NO 2 is 26 Gg N yr −1 and the preliminary estimate for HNO 3 is 42 Gg N yr −1. For sulphur and reduced nitrogen, estimated dry deposition accounts for 40% of total deposition, including wet and cloud droplet deposition. NO 2 dry deposition only accounts for 15% of total oxidised nitrogen deposition, but another 25% may come from the dry deposition of HNO 3, giving a similar 40% overall by dry deposition. The sensitivity of the model to parameter values and the comparisons of modelled output with measurements show that parameter choices may be valid only at the scale of European countries rather than the whole continent.

Modeling the long-term frequency distribution of regional ozone concentrations

Efficient methods are developed for modeling emissions – air quality relationships that govern ozone and NO 2 concentrations over very long periods of time. A baseline model evaluation study is conducted to assess the accuracy and speed with which the relationship between pollutant emissions and the frequency distribution of O 3 concentrations throughout the year can be computed along with annual average NO 2 values using a deterministic photochemical airshed model driven by automated objective analysis of measured meteorological parameters. Methods developed are illustrated by application to the air quality situation that exists in Southern California. Model performance statistics for O 3 are similar to the results obtained in previous short-term episodic model evaluation studies that were based on hand-crafted meteorological inputs that are supplemented by expensive field measurement campaigns. Model predictions at one of the highest NO 2 concentration sites in the US indicate that measured violation of the US annual average NO 2 air quality standard at that site occurs because other species such as HNO 3 and PAN are measured as if they were NO 2 by the chemiluminescent NO x monitors in current use.

Atmospheric deposition of nitrogen compounds in the Czech Republic

This study presents estimates of dry and wet deposition of nitrogen compounds in the Czech Republic. Deposition has been estimated from monitored and modelled concentrations in the atmosphere and in precipitation, where the most important nitrogen compounds are nitrogen oxides and ammonia, and their reaction products. Measured atmospheric concentrations of NO x, NH 3 and of aerosol particles (NO 3 − and NH 4 +), along with measured concentrations of NO 3 − and NH 4 + in precipitation, weighted by precipitation amounts, were interpolated with a properly used Kriging technique on a 10 × 10 km grid covering the whole Czech Republic. Wet deposition was derived from concentration values for NO 3 − and NH 4 + in precipitations and from precipitation amounts. Dry deposition was derived from concentrations of gaseous components and aerosol in the air, and from their deposition velocities. A resistance model was used for calculating NO x, NH 3 deposition velocities; deposition velocities of HNO 3 were derived from the literature and deposition velocities of particles were parameterized. The annual average NO y deposition in the Czech Republic in 1994 was estimated at 972 eq H + ha −1 a −1 and the annual average NH x deposition at 887 eq H + ha −1 a −1.

Urban NO 2 concentrations in the U.K. in 1987

A mational air quality monitoring network has been established in the U.K. by Warren Spring Laboratory, on behalf of the U.K. Department of the Environment, to determine compliance with the European Community Directive for nitrogen dioxide. Data from the six network sites for 1987 are presented and analysed. No site in the U.K. breached the NO 2 Directive Limit Value during this year, though the closest approaches were at the two London stations. Annual average NO 2 concentrations, which varied from 23 to 39 ppb, were consistent with the top five percentile of long-term measurements from a national survey of over 360 U.K. urban areas carried out in 1986. The temporal variability of NO 2 concentrations was substantially lower over all time scales than that for NO: winter/summer ratios for all sites averaged 2.9 for NO and 1.3 for NO 2. Most sites showed strong diurnal variations for NO which were primarily influenced by traffic emissions during rush hours, although these variations were less marked for NO 2. A markedly non-proportional relationship between annual and daily average NO 2 and NO x levels was observed, and this has important implications for its efficacy of possible NO x emission control strategies. An analysis of measured NO 2/NO x ratios over weekends and weekday periods demonstrates, for instance, that a 20% emission cutback may result, typically, in a corresponding NO 2 reduction of 12% at urban locations in the U.K. NO x reductions, however, exert a more proportional effect on NO 2 concentrations at kerbside and rural locations.

Nitrate Leaching Losses from Monolith Lysimeters as Influenced by Nitrapyrin

AbstractThree monolith lysimeters, each with a surface area of 8.1 m2 and a depth of 2.4 m, were planted to no‐till corn (Zea mays L.) for 6 consecutive years. The lysimeters contained a Rayne silt loam (Typic Hapludult), a well‐drained residual soil. Urea was placed in a slot approximately 10‐cm deep and 10 to 15 cm from the corn row at a rate of 336 kg N/ha. The urea applied to two of the lysimeters was treated with nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine], a nitrification inhibitor, and applied untreated on the third lysimeter. Two years of unfertilized meadow immediately preceded the corn. Concentrations of NO−3; in the leachate from the lysimeters were higher during the corn years than during the meadow period. Concentrations showed seasonal variations during the last 3 yr of the study, but showed no increasing trend. The leachate from the lysimeters receiving the nitrapyrin treated urea had seasonally flow‐weighted NO−3; concentrations ranging from 6 to 40 mg/L, while the leachate from the lysimeter receiving untreated urea had seasonally flow‐weighted NO−3;‐N concentrations ranging from 20 to 54 mg/L. Nitrate‐N losses showed a similar treatment difference. The 6‐yr annual average NO−3; loss was 117 and 160 kg/ha from the lysimeters with the treated urea and untreated urea, respectively. This study demonstrates that nitrification inhibitors such as nitrapyrin, have a potential to reduce NO−3; leaching when applied with ammoniacal fertilizers.

Anthropogenic nitrogen oxide transport and deposition in Eastern North America

A long-range atmospheric transport and transformation model is presented for nitrogen oxides emitted by man-made sources. The model parameters are optimized by matching the model output—annual average nitrate (NO − 3) wet deposition—to observed deposition at 109 precipitation sampling stations in eastern N America that operated continuously in the years 1980–1982. The root-mean-square residual between observations and predictions is 2.9 kg NO − 3 ha −1 y −1 or 19.7% of the root-mean-square observed value. The trend of estimated annual average NO − 3 concentrations in precipitation at Hubbard Brook, New Hampshire compares well with the observations from 1964 to 1981. Transfer coefficients decay nearly exponentially with distance with length scales of 200–800 km, depending on source-receptor orientation with respect to the resultant annual wind direction. The model is used for source apportionment of NO − 3 wet deposition at several receptors and for estimating a nitrogen budget for eastern N America, including the transboundary fluxes between the U.S. and Canada.

An appraisal of emissions control requirements in the California South Coast Air Basin

The purpose of this study is to evaluate the effect of reductions of reactive organic gases (ROG) and NO x emissions on short-term O 3 and NO 2 concentrations and annual average NO 2 concentrations in the California South Coast Air Basin. Short-term air quality predictions were obtained by applying the Systems Applications Airshed Model to summer O 3 and autumn NO 2 episodes. Effects of emission controls on annual NO 2 concentrations were estimated using CDM and a new parcel tracking model NOXTRAK. Results for the summer O 3 episode indicate that ROG emission reduction in an effective means for reducing peak O 3 concentrations. NO x emission reduction imposed in addition to ROG emission reductions are counterproductive in reducing peak O 3 concentrations. The modeling results also suggest that attainment of the 1-h federal O 3 standard requires ROG emission reductions on the order of 80% from 1987 levels. Results for the autumn NO 2 episode indicate that NO x emission reductions approximating those recommended in a proposed Air Quality Management Plan (about 22%) will result in only small (about 5%) reductions in the peak NO 2 concentrations. ROG emission reduction may be more effective than NO x emission reduction in reducing the peak NO 2 concentration. For the episode studied, a reduction of 36% in ROG emissions is estimated to result in a reduction in peak NO 2 concentrations commensurate with that required to attain the 1-h state NO 2 standard. Model calculations also indicate that the federal NO 2 standard may not be meet by 1987 at one or two stations, but may blosely approached.