Repository hosted by TU Delft Library

The nitrite equivalent of nitrogen dioxide in its determination in polluted air by means of a Griess type reagent is commonly called the Saltzman factor. Values ranging from 0.5 to 1.000 have been reported, but discussion about the 'right' value continues. The results of experimental calculations are presented to demonstrate that there is no set right value, but that it depends on circumstances and may be more or less chosen at will. No explanation was found for the differences reported. The results are summarized, and illustrate that the Saltzman factor is not a constant, but is inversely related to NO production and varies according to the expectations based on the expounded reaction mechanisms. In practice, a method with a high and therefore more constant factor would be recommended, such as the use of sulfanilamide instead of sulfanilic acid and a NEDA (naphthylethylene diamine dihydrochloride) concentration as low as possible without decreasing the collection efficiency too much with the air flow rate and washing bottle. Chemicals/CAS: nitrogen dioxide, 10102-44-0

In past years, the European limit value for average annual NO2 concentration has been exceeded in city streets and along motorways in the Netherlands. By 2015 the limit value must be adhered to in the Netherlands. Although the total road length for which exceedance is likely is expected to decrease over the coming years, exceedances may still occur by 2015. Future NO2 concentrations not only depend on economic growth, current and proposed policies, and on inevitable meteorological fluctuations, they also depend on the effectiveness of technical measures to reduce emissions. New emission measurements for heavy-duty vehicles in the Euro-V (and Euro-III) emission standard categories, carried out under typical Dutch driving conditions, have revealed that real-world NOx emissions from these trucks are significantly higher than was previously estimated based on the reduction steps in the Euro emission standards. Emission levels were higher, by about a factor of three, along city streets, and 10 to 40% higher along motorways. These higher emission levels resulted in higher estimated national NOx emissions, increasing from 250kt to 264kt, compared with the national emission ceiling of 260kt, to be adhered to by 2010. The higher emissions more than double the total road length with possible exceedance (chance >33%) of the NO2 limit value; from about 100km to about 250km along cities streets and motorways, by 2015. These higher emissions from trucks, therefore, affect the chances of the limit values being adhered to, in time, everywhere in the Netherlands. © 2011 Elsevier Ltd.

The suitability of European networks to check compliance with air quality standards and to assess exposure of the population was investigated. An air quality model (URBIS) was applied to estimate and compare the spatial distribution of the concentration of nitrogen dioxide (NO2) in ambient air in four large cities. The concentrations calculated at the location of the monitoring stations, compared well with the concentrations measured at the stations indicating that the models worked well. Therefore the calculated concentration distributions were used as a proxy for the actual concentration distributions across the cities. The distributions of these proxy concentrations across the city populations was determined and cumulative population distribution curves were estimated. The calculated annual mean values at the monitoring network stations were located on the population distribution curves to estimate the fractions of the populations that the monitoring network stations represent. This macro scale procedure is used to evaluate which subgroups of the monitoring stations can be reliably used to decide on compliance or to estimate the concentration the population is exposed to. In addition, the CAR model and Computational Fluid Dynamics (CFD) models are used to investigate the effect of micro scale siting of the monitoring stations within the streets.The following observations were made:. - Berlin and London networks cover the distribution of concentrations to which the population is exposed rather well, while Stuttgart and Barcelona have stations at sites with mainly the higher concentrations and the exposure is covered less well.- The networks in London and Berlin, with a substantial number of urban background stations, seem fit to monitor the average population exposure, contrary to those in Stuttgart and Barcelona with only a limited number of these stations.- The concentrations measured at street stations hardly reflect the calculated differences in street pollution between the cities. In Stuttgart the stations are, in line with the EU directive, placed in the most polluted streets, while in other cities there are no stations in the streets with the highest pollution levels.- The concentrations measured at street stations - particularly where buildings inhibit ventilation - are very sensitive to the exact location within the street. Different siting choices may have an effect that for NO2 could reach up to 10μg/m3 in realistic conditions. Street stations, representing only a small urban area, are not suitable for characterising the exposure of the general population.It is important to note that epidemiological studies whether investigating short term-effects or those studying long-term effects are potentially affected by the issues raised in the paper. Long-term cumulative exposure estimates that are based rather uncritically on monitoring data may be biased if the stations are not representative. It is recommended to use models to support the interpretation and spatial extrapolation of the results of measurements in existing networks. The use of models also relaxes the need for station relocation in inadequate networks, which often would compromise trend analysis. It also relaxes the importance of exact or detailed, comprehensive, station classifications since all stations can be used in exposure assessments.

Due to the expansion of the Port of Amsterdam, Urban development and the construction of new highways, air pollution levels are about to exceed European guidelines in and around the port region of Amsterdam. To assess the air quality in this region and the impact of theport emissions on its environment, an air quality tool has been developed. It calculates the contribution from the emissions in the port of Amsterdam to the total air pollution for nitrogen dioxide (NO<inf>2</inf>) and particulate matter (PM<inf>10</inf>). The tool is used to calculate annual mean concentrations for actual conditions and future scenario's. It takes into account emissions from traffic, industrial facilities, trans-shipment, navigating ships and ships in the port. For the year 2009, calculations show a relatively small annual mean contribution of the port emissions on the air pollution levels surrounding the port region.

The advent of satellite data has provided a source of independent information to monitor trends in tropospheric nitrogen dioxide levels. To interpret these trends, one needs to know the sensitivity of the satellite retrieved NO2 column to anthropogenic emissions. We have applied a chemistry transport model to investigate the sensitivity of the modeled NO2 column, sampled at the OMI (Ozone Monitoring Instrument) overpass time and location and weighted by the OMI averaging kernel, to emission sources across Europe. The most important contribution (~35%) in Western Europe is made by road transport. Off-road transport and industrial combustion each contribute 10%-15% across continental Europe. In Eastern Europe, power plant contributions are of comparable magnitude as those of road transport. To answer the question if the OMI-NO2 trends can be translated directly into emission changes, we assessed the anticipated changes in OMI-NO2 between 2005 and 2020. Although the results indicated that for many countries, it is indeed possible, for medium- and small-sized coastal countries, the contribution of the increasing shipping emissions in adjacent sea areas may mask a significant part of national emission reductions. This study highlights the need for a combined use of models, a priori emission estimates and satellite data to verify emission trends. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Interannual variability (IAV) in tropospheric species concentrations can be driven by variability in emissions, chemistry, transport and UV radiation. In a 3D CTM study we have found good agreement between the IAV of NO2 columns observed by the GOME satellite instrument and model simulations over Western Europe from 1996 to 2000. We find that meteorological variability is an important factor during this period. Averaged 10 m wind speeds from the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis are a good proxy for the overall meteorology driving the IAV during the studied period of 1996-2000. Copyright © 2008 Royal Meteorological Society.

A novel imaging-DOAS (differential optical absorption spectroscopy) instrument IMPACT (Imaging MaPper for AtmospheriC observaTions) is presented combining full-azimuthal pointing (360◦) with a large vertical coverage (∼41◦). Complete panoramic scans are acquired at a temporal resolution of ∼15min, enabling the retrieval of NO2 vertical profiles over the entire panorama around the measurement site. IMPACT showed excellent agreement (correlation > 99%) with coincident multiaxis DOAS (MAX-DOAS) measurements during the Second Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI-2)campaign. The temporal variability of NO2 slant columns within a typical MAX-DOAS vertical scanning sequence could be resolved and was as large as 20% in a case study under good viewing conditions. The variation of corresponding profiles and surface concentrations was even larger (40%). This variability is missed when retrieving trace gas profiles based on standard MAX-DOAS measurements. The azimuthal distribution of NO2 around the measurement site showed inhomogeneities (relative differences) up to 120% (on average 35%) on short timescales (individual panoramic scans). This is more than expected for the semirural location. We explain this behavior by the transport of pollution. Exploiting the instrument’s advantages, the plume’s trajectory during a prominent transport event could be reconstructed. Finally, the potential for retrieving information about the aerosol phase function from O4 slant columns along multiple almucantar scans of IMPACT is demonstrated, with promising results for future studies.

The development of sensing schemes for the detection of health-threatening gases is an attractive subject for research towards novel integrated autonomous sensor systems. We report here on a novel way of sensing NO\2 by surface plasmon resonance (SPR) using a gas-sensitive layer composed of 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (2H-OHTPP) embedded in a nanoporous silica matrix on top of a gold thin film. The sensing mechanism is based on the modification of the SPR condition due to gas induced changes in the optical properties of the sensing layer. We demonstrate that the use of nanoporous silica as embedding matrix enhances the detection sensitivity compared to a polymer matrix with low porosity. The second important finding of this work is that the active layer thickness plays a significant role in the enhancement of the sensing response. The improvement is explained by the optimization of the overlap between the field of the surface plasmon polariton and the active dielectric layer. © 2011 Elsevier B.V. All rights reserved.

The annual air quality standard of NO2 is often exceeded in urban areas near heavy traffic locations. Despite significant decrease of NOx emissions in 1986-2005 in the industrial and harbour area near Rotterdam, NO2 concentrations at the urban background remain at the same level since the end of the nineties. Trend analysis of monitoring data revealed that the ozone/NOx equilibrium is a more important factor than increasing direct NO2 emissions by traffic. The latter has recently been identified as an additional NO2 source due to the introduction of oxy-catalytic converters in diesel vehicles and the growing number of diesel vehicles. However, in Rotterdam over the period 1986-2005 direct NO2 emissions by road traffic only increased 3-4%. Due to the importance of the ozone/NOx equilibrium, it is concluded that local NOx emissions in Rotterdam need substantial reduction to achieve lower NO2 urban background levels. This is a relatively costly abatement strategy and, therefore, a "hotspot" approach aiming at reducing NOx emissions by local traffic measures is more effective to meet European air quality standards. © 2008 Elsevier Ltd. All rights reserved.

A 14-month data set of MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) tropospheric NO2 column observations in De Bilt, the Netherlands, has been compared with the regional air quality model Lotos-Euros. The model was run on a 7×7 km2 grid, the same resolution as the emission inventory used. A study was performed to assess the effect of clouds on the retrieval accuracy of the MAX-DOAS observations. Good agreement was found between modeled and measured tropospheric NO2 columns, with an average difference of less than 1% of the average tropospheric column (14.5 · 1015 molec cmg-2). The comparisons show little cloud cover dependence after cloud corrections for which ceilometer data were used. Hourly differences between observations and model show a Gaussian behavior with a standard deviation (σ) of 5.5 · 1015 molec cmg-2. For daily averages of tropospheric NO2 columns, a correlation of 0.72 was found for all observations, and 0.79 for cloud free conditions. The measured and modeled tropospheric NO2 columns have an almost identical distribution over the wind direction. A significant difference between model and measurements was found for the average weekly cycle, which shows a much stronger decrease during the weekend for the observations; for the diurnal cycle, the observed range is about twice as large as the modeled range. The results of the comparison demonstrate that averaged over a long time period, the tropospheric NO2 column observations are representative for a large spatial area despite the fact that they were obtained in an urban region. This makes the MAX-DOAS technique especially suitable for validation of satellite observations and air quality models in urban regions.

Background: Air pollution exposure during pregnancy might have trimester-specific effects on fetal growth. Objective: We prospectively evaluated the associations of maternal air pollution exposure with fetal growth characteristics and adverse birth outcomes in 7,772 subjects in the Netherlands. Methods: Particulate matter with an aerodynamic diameter < 10 μm (PM 10) and nitrogen dioxide (NO 2) levels were estimated using dispersion modeling at the home address. Fetal head circumference, length, and weight were estimated in each trimester by ultrasound. Information on birth outcomes was obtained from medical records. Results: In cross-sectional analyses, NO 2 levels were inversely associated with fetal femur length in the second and third trimester, and PM 10 and NO 2 levels both were associated with smaller fetal head circumference in the third trimester [-0.18 mm, 95% confidence interval (CI): -0.24, -0.12 mm; and -0.12 mm, 95% CI: -0.17, -0.06 mm per 1-μg/m 3 increase in PM 10 and NO 2, respectively]. Average PM 10 and NO 2 levels during pregnancy were not associated with head circumference and length at birth or neonatally, but were inversely associated with birth weight (-3.6 g, 95% CI: -6.7, -0.4 g; and -3.4 g, 95% CI: -6.2, -0.6 g, respectively). Longitudinal analyses showed similar patterns for head circumference and weight, but no associations with length. The third and fourth quartiles of PM 10 exposure were associated with preterm birth [odds ratio (OR) = 1.40, 95% CI: 1.03, 1.89; and OR = 1.32; 95% CI: 0.96, 1.79, relative to the first quartile]. The third quartile of PM10 exposure, but not the fourth, was associated with small size for gestational age at birth (SGA) (OR = 1.38; 95% CI: 1.00, 1.90). No consistent associations were observed for NO 2 levels and adverse birth outcomes. Conclusions: Results suggest that maternal air pollution exposure is inversely associated with fetal growth during the second and third trimester and with weight at birth. PM10 exposure was positively associated with preterm birth and SGA.

Background: Exposure to air pollution has been associated with higher C-reactive protein (CRP) levels, suggesting an inflammatory response. Not much is known about this association in pregnancy. Objectives: We investigated the associations of air pollution exposure during pregnancy with maternal and fetal CRP levels in a population-based cohort study in the Netherlands. Methods: Particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10) and nitrogen dioxide (NO 2) levels were estimated at the home address using dispersion modeling for different averaging periods preceding the blood sampling (1 week, 2 weeks, 4 weeks, and total pregnancy). High-sensitivity CRP levels were measured in maternal blood samples in early pregnancy (n = 5,067) and in fetal cord blood samples at birth (n = 4,450). Results: Compared with the lowest quartile, higher PM10 exposure levels for the prior 1 and 2 weeks were associated with elevated maternal CRP levels (> 8 mg/L) in the first trimester [fourth PM10 quartile for the prior week: odds ratio (OR), 1.32; 95% confidence interval (CI): 1.08, 1.61; third PM10 quartile for the prior 2 weeks: OR, 1.28; 95% CI: 1.06, 1.56]; however, no clear dose-response relationships were observed. PM10 and NO2 exposure levels for 1, 2, and 4 weeks preceding delivery were not consistently associated with fetal CRP levels at delivery. Higher long-term PM10 and NO 2 exposure levels (total pregnancy) were associated with elevated fetal CRP levels (> 1 mg/L) at delivery (fourth quartile PM10: OR, 2.18; 95% CI: 1.08, 4.38; fourth quartile NO 2: OR, 3.42; 95% CI: 1.36, 8.58; p-values for trend < 0.05). Conclusions: Our results suggest that exposure to air pollution during pregnancy may lead to maternal and fetal inflammatory responses.

A speed limit of 80km/h with "strict enforcement" has been introduced in 2005 on zones of urban motorways in The Netherlands with the aim to improve air quality of NO₂ and PM₁₀ along these motorways. Strict enforcement means speed control by camera surveillance over the whole trajectory of 2-4km combined with licence plate recognition and automatic fining in case of exceeding the speed limit. Traffic data measured in Rotterdam and Amsterdam at the zones without and with speed management showed that traffic dynamics have been significantly reduced as a result of speed management with strict enforcement. Reduction of traffic dynamics results in more free-flowing traffic with relatively less NO_x and exhaust PM₁₀ emissions compared to congested traffic, i.e., stop-and-go traffic.The actual effect on NO_x and PM₁₀ emissions at these speed management zones was studied in the cities Rotterdam and Amsterdam. The study was performed in two different ways: firstly by measurements and by modelling the contribution to NO_x and PM₁₀ concentrations on both sides of the motorways, and secondly by estimating the change in traffic dynamics and the effect on emissions. From the results of both approaches in this study, it was concluded that in our case study in the Netherlands emission reduction by speed management is in the range of 5-30% for NO_x and 5-25% for PM₁₀. Actual emission reductions by speed management at a specific motorway mainly depend on the ratio of congested traffic prior and after implementation of speed management. The larger this ratio, the larger is the relative emission reduction. The impact on air quality of 80km/h for NO_x and PM₁₀ is largest on motorways with a high fraction of heavy-duty vehicles. © 2010 Elsevier B.V.

In this study trends in the tropospheric NO2 concentrations during 2005-2010 across Europe were derived from the synergistic use of OMI NO2 tropospheric columns and the chemistry transport model LOTOS-EUROS and were compared to reported NOx emissions. The chemistry transport model captures a large fraction of the variability in NO2 columns at a synoptic timescale, although a seasonal signal in the bias between the modelled and retrieved column data remains. Using a simulation with constant emissions in time, trends were derived on the basis of the systematically changing bias between the modelled and retrieved columns. Significant negative trends of 5-6%a-1 were found in highly industrialized areas across Western Europe. Strongest decreases in NO2 concentrations are observed over a region with many power plants in Northern Spain (10-20%a-1) and over the Po Valley (11%a-1). A source apportionment simulation was performed to evaluate the sensitivity of the Ozone Monitoring Instrument (OMI) to NOx emission sources across Europe, identifying the importance of changes in the energy sector in Northern Spain. A comparative study on in-situ NO2 measurements shows that annual reductions at the surface are of 2-3%a-1. This trend increases from rural polluted sites to remote areas (~4.5%a-1). The observed variability with station type may be explained by the increase in primary NO2 emissions combined with the representativeness of the measurement sites. Comparing country average trends in NO2 columns with national NOx emission totals shows that these are generally within a factor 2 of each other. A better agreement was found for western European countries than for eastern European countries. The method described here is a promising methodology to complement and evaluate trends in NO2 columns and indirectly emission strengths. A strong advantage is the fact that the methodology using satellite data is in principle consistent throughout the entire domain. © 2014 Elsevier Inc.

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 (NO₂) 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 NO₂ 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 NO₂ 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 NO₂.Moderate agreement was found between a dispersion model and a land use regression model in calculating annual average NO₂ concentrations in an area with multiple sources. The dispersion model explained concentrations at validation sites better. © 2010 Elsevier Ltd.

The spatial distributions of sulphur dioxide (SO2) and nitrogen oxides (NO(x)) emissions are essential inputs to models of atmospheric transport and deposition. Information of this type is required for international negotiations on emission reduction through the critical load approach. High-resolution emission maps for the Republic of Ireland have been created using emission totals and a geographical information system, supported by surrogate statistics and landcover information. Data have been subsequently allocated to the EMEP 50 x 50-km grid, used in long-range transport models for the investigation of transboundary air pollution. Approximately two-thirds of SO2 emissions in Ireland emanate from two grid-squares. Over 50% of total SO2 emissions originate from one grid-square in the west of Ireland, where the largest point sources of SO2 are located. Approximately 15% of the total SO2 emissions originate from the grid-square containing Dublin. SO2 emission densities for the remaining areas are very low, < 1 t km-2 year-1 for most grid-squares. NO(x) emissions show a very similar distribution pattern. However, NO(x) emissions are more evenly spread over the country, as about 40% of total NO(x) emissions originate from road transport. (C) 2001 Elsevier Science Ltd.

This paper presents the results of a series of experiments on the condensed phase decomposition and the gas phase combustion of hydrazinium nitroformate (HNF). The experiments include SEM analysis of quenched samples that showed evidence of the formation of a foam layer. FTIR spectrometry and mass spectrometry provide details on species formation during decomposition and combustion. The analysis of the results led to the identification of probable overall reactions in the low pressure regime around 0.1 MPa. It is found that decomposition of HNF takes place through formation of ammonium nitroformate, and through dissociative vaporisation. The gas phase near the surface of burning HNF is expected to contain a large amount of hydrazine, ammonia and nitrogen dioxide (as a decomposition product of nitroform). The primary reaction zone of the HNF flame is then associated with the exothermic reactions of these species. The resulting nitrogen oxide is subsequently reduced to molecular nitrogen in the secondary flame. © 2009 The Combustion Institute.

Background: Long-term exposure to particulate matter air pollution has been associated with increased cardiopulmonary mortality in the USA. We aimed to assess the relation between traffic-related air pollution and mortality in participants of the Netherlands Cohort study on Diet and Cancer (NLCS), an ongoing study. Methods: We investigated a random sample of 5000 people from the full cohort of the NLCS study (age 55-69 years) from 1986 to 1994. Long-term exposure to traffic-related air pollutants (black smoke and nitrogen dioxide) was estimated for the 1986 home address. Exposure was characterised with the measured regional and urban background concentration and an indicator variable for living near major roads. The association between exposure to air pollution and (cause specific) mortality was assessed with Cox's proportional hazards models, with adjustment for potential confounders. Findings: 489 (11%) of 4492 people with data died during the follow-up period. Cardiopulmonary mortality was associated with living near a major road (relative risk 1.95, 95% CI 1.09-3.52) and, less consistently, with the estimated ambient background concentration (1.34, 0.68-2.64). The relative risk for living near a major road was 1.41 (0.94-2.12) for total deaths. Non-cardiopulmonary, non-lung cancer deaths were unrelated to air pollution (1.03, 0.54-1.96 for living near a major road). Interpretation: Long-term exposure to traffic-related air pollution may shorten life expectancy.

Background: Several studies have found an effect on mortality of between-city contrasts in long-term exposure to air pollution. The effect of within-city contrasts is still poorly understood. Objectives: We studied the association between long-term exposure to traffic-related air pollution and mortality in a Dutch cohort. Methods: We used data from an ongoing cohort study on diet and cancer with 120,852 subjects who were followed from 1987 to 1996. Exposure to black smoke (BS), nitrogen dioxide, sulfur dioxide, and particulate matter ≤ 2.5 μm (PM2.5), as well as various exposure variables related to traffic, were estimated at the home address. We conducted Cox analyses in the full cohort adjusting for age, sex, smoking, and area-level socioeconomic status. Results: Traffic intensity on the nearest road was independently associated with mortality. Relative risks (95% confidence intervals) for a 10-μg/m3 increase in BS concentrations (difference between 5th and 95th percentile) were 1.05 (1.00-1.11) for natural cause, 1.04 (0.95-1.13) for cardiovascular, 1.22 (0.99-1.50) for respiratory, 1.03 (0.88-1.20) for lung cancer, and 1.04 (0.97-1.12) for mortality other than cardiovascular, respiratory, or lung cancer. Results were similar for NO2 and PM2.5, but no associations were found for SO2. Conclusions: Traffic-related air pollution and several traffic exposure variables were associated with mortality in the full cohort. Relative risks were generally small. Associations between natural-cause and respiratory mortality were statistically significant for NO2 and BS. These results add to the evidence that long-term exposure to ambient air pollution is associated with increased mortality.

Nitrous oxide (N2O) is a potent greenhouse gas produced in soils and aquatic systems. The UNFCCC requires participants to report 'indirect' N2O emissions, following from agricultural N losses to ground- and surface water and N deposition on (other) ecosystems due to agricultural sources. Indirect N2O emission due to atmospheric N deposition is presently not reported by the Netherlands. In this paper, we quantify the consequences of various tiers to estimate indirect N2O due to deposition for a country with a high agricultural N use and discuss the reliability and potential errors in the IPCC methodology. A literature review suggests that the current IPCC default emission factor for indirect N 2O from N deposition is underestimated by a factor ∼2. Moreover, considering anthropogenic N emissions from agriculture only and not from e.g., traffic and industry, results in further underestimation of indirect N 2O emissions. We calculated indirect N2O emissions due to Dutch anthropogenic N emissions to air by using official Dutch N emission data as input in an atmospheric transport and deposition model in combination with land use databases. Next, land use-specific emission factors were used to estimate the indirect N2O emission. This revealed that (1) for some countries, like the Netherlands, most agricultural N emitted will be deposited on agricultural soils, not on natural ecosystems and, (2) indirect N 2O emissions are at least ∼20% higher because more specific emission factors can be applied that are higher than the IPCC default. The results suggest that indirect N2O emission due to deposition is underestimated in current N2O budgets. © 2005 Elsevier Ltd. All rights reserved. Chemicals/CAS: nitrogen dioxide, 10102-44-0; nitrogen, 7727-37-9