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The study focuses on the application of a dynamic ammonia emission into the Weather Research and Forecasting Chemistry model (WRF-Chem) and the influence on the simulated ammonia concentrations and the overall model performance. We have focused on agricultural ammonia sources and have analysed both hourly and daily patterns of ammonia emissions and concentrations at measurement sites located in agricultural areas or influenced by this activity. For selected episodes, we have also investigated the 3-D patterns of the ammonia concentrations in the atmosphere. The application of the dynamic ammonia emission into the WRF-Chem model (the "DYNAMIC" simulation) results in an improvement of the modelled daily ammonia concentrations in comparison to a static approach (the "BASE" simulation), which is currently widely used in chemical transport models. In the case of hourly resolution, we have observed an improvement for the DYNAMIC approach for the winter and autumn seasons, but for the entire year the modelled hourly ammonia peaks are shifted toward the afternoon hours if compared with measurements. This study indicates that the current description of the diurnal cycle of the ammonia concentration from fields is not accurate and more research is needed in order to improve the processes that describe the emission from fertilised fields. The results suggest that the governing processes in relation to the diurnal cycle are the atmospheric mixing and the emission strength. Therefore, an improved description of the diurnal profile of ammonia concentrations within atmospheric models requires a better description of the planetary boundary layer height and a stronger daily pattern of ammonia emission, e.g. through increased evaporation or increased fluxes from the surface. [ABSTRACT FROM AUTHOR]

Semi-parameterized street canyon models, as e.g. the Operational Street Pollution Model (OSPM®), have been frequently applied for the last two decades to analyse levels and consequences of air pollution in streets. These models are popular due to their speed and low input requirements. One often used simplification is the assumption that emissions are homogeneously distributed in the entire length and width of the street canyon. It is thus the aim of the present study to analyse the impact of this assumption by implementing an inhomogeneous emission geometry scheme in OSPM. The homogeneous and the inhomogeneous emission geometry schemes are validated against two real-world cases: Hornsgatan, Stockholm, a sloping street canyon; and Jagtvej, Copenhagen; where the morning rush hour has more traffic on one lane compared to the other. The two cases are supplemented with a theoretical calculation of the impact of street aspect (height = width) ratio and emission inhomogeneity on the concentrations resulting from inhomogeneous emissions. The results show an improved performance for the inhomogeneous emission geometry over the homogeneous emission geometry. Moreover, it is shown that the impact of inhomogeneous emissions is largest for near-parallel wind directions and for high aspect ratio canyons. The results from the real-world cases are however confounded by challenges estimating the emissions accurately. [ABSTRACT FROM AUTHOR]

This study estimates the effect on air quality of retrofitting SCRT on about 300 urban buses in Copenhagen from September 2015 to March 2016. The retrofitted buses were of Euro III, Euro IV and EEV emission standards. The specific SCRT technology applies ammonia as injected into the exhaust as a gas as opposed to normally as a liquid (urea). This technology is more efficient in reducing NO x emissions, especially under urban driving conditions with relatively low exhaust temperatures. The estimation of the effect is based on air quality model calculations for 98 selected busy streets in Copenhagen for 2015 based on, among others, information from the Zealand public transport agency about buses with and without retrofitted SCRT. More detailed analyses were conducted for two of the streets where fixed air quality measuring stations are located in Copenhagen. Furthermore, a before-after analysis of the development of measured concentrations at fixed measuring stations was carried out to isolate the effect of the retrofitted SCRT. The model calculations showed substantial reductions in emissions of NO x and exhaust particles from each bus (90%) but low reductions in concentrations of NO 2 , PM 2.5 and PM 10 , respectively 3% for 98 streets on average for NO 2 , and 0.1%[0.2%] for PM 2.5 and 0.07%[0.1%] for PM 10 for H.C. Andersen Boulevard and [Jagtvej]. Based on the analysis of trends in the measurements it was not possible to isolate an effect of SCRT on urban buses in Copenhagen probably due to the large variations in meteorology affecting the variations in concentrations.

High-resolution air quality (AQ) maps based on street-by-street measurements have become possible through large-scale mobile measurement campaigns. Such campaigns have produced data-only maps and have been used to produce empirical models [i.e., land use regression (LUR) models]. Assuming that all road segments are measured, we developed a mixed model framework that predicts concentrations by an LUR model, while allowing road segments to deviate from the LUR prediction based on between-segment variation as a random effect. We used Google Street View cars, equipped with high-quality AQ instruments, and measured the concentration of NO 2 on every street in Amsterdam ( n = 46.664) and Copenhagen ( n = 28.499) on average seven times over the course of 9 and 16 months, respectively. We compared the data-only mapping, LUR, and mixed model estimates with measurements from passive samplers ( n = 82) and predictions from dispersion models in the same time window as mobile monitoring. In Amsterdam, mixed model estimates correlated r s (Spearman correlation) = 0.85 with external measurements, whereas the data-only approach and LUR model estimates correlated r s = 0.74 and 0.75, respectively. Mixed model estimates also correlated higher r s = 0.65 with the deterministic model predictions compared to the data-only ( r s = 0.50) and LUR model ( r s = 0.61). In Copenhagen, mixed model estimates correlated r s = 0.51 with external model predictions compared to r s = 0.45 and r s = 0.50 for data-only and LUR model, respectively. Correlation increased for 97 locations ( r s = 0.65) with more detailed traffic information. This means that the mixed model approach is able to combine the strength of data-only mapping (to show hyperlocal variation) and LUR models by shrinking uncertain concentrations toward the model output.

We conduct the first 4D-Var inversion of NH 3 accounting for NH 3 bi-directional flux, using CrIS satellite NH 3 observations over Europe in 2016. We find posterior NH 3 emissions peak more in springtime than prior emissions at continental to national scales, and annually they are generally smaller than the prior emissions over central Europe, but larger over most of the rest of Europe. Annual posterior anthropogenic NH 3 emissions for 25 European Union members (EU25) are 25% higher than the prior emissions and very close (<2% difference) to other inventories. Our posterior annual anthropogenic emissions for EU25, the UK, the Netherlands, and Switzerland are generally 10%-20% smaller than when treating NH 3 fluxes as uni-directional emissions, while the monthly regional difference can be up to 34% (Switzerland in July). Compared to monthly mean in-situ observations, our posterior NH 3 emissions from both schemes generally improve the magnitude and seasonality of simulated surface NH 3 and bulk NH x wet deposition throughout most of Europe, whereas evaluation against hourly measurements at a background site shows the bi-directional scheme better captures observed diurnal variability of surface NH 3 . This contrast highlights the need for accurately simulating diurnal variability of NH 3 in assimilation of sun-synchronous observations and also the potential value of future geostationary satellite observations. Overall, our top-down ammonia emissions can help to examine the effectiveness of air pollution control policies to facilitate future air pollution management, as well as helping us understand the uncertainty in top-down NH 3 emissions estimates associated with treatment of NH 3 surface exchange., (© 2022. The Authors.)

Road transport is the main anthropogenic source of NOx in Europe, affecting human health and ecosystems. Thus, mitigation policies have been implemented to reduce on-road vehicle emissions, particularly through the Euro standard limits. To evaluate the effectiveness of these policies, we calculated NO 2 and NOx concentration trends using air quality and meteorological measurements conducted in three European cities over 26 years. These data were also employed to estimate the trends in NOx emission factors (EF NOx , based on inverse dispersion modeling) and NO 2 :NOx emission ratios for the vehicle fleets under real-world driving conditions. In the period 1998-2017, Copenhagen and Stockholm showed large reductions in both the urban background NOx concentrations (-2.1 and -2.6% yr -1 , respectively) and EF NOx at curbside sites (68 and 43%, respectively), proving the success of the Euro standards in diminishing NOx emissions. London presented a modest decrease in urban background NOx concentrations (-1.3% yr -1 ), while EF NOx remained rather constant at the curbside site (Marylebone Road) due to the increase in public bus traffic. NO 2 primary emissions -that are not regulated- increased until 2008-2010, which also reflected in the ambient concentrations. This increase was associated with a strong dieselization process and the introduction of new after-treatment technologies that targeted the emission reduction of other species (e.g., greenhouse gases or particulate matter). Thus, while regulations on ambient concentrations of specific species have positive effects on human health, the overall outcomes should be considered before widely adopting them. Emission inventories for the on-road transportation sector should include EF NOx derived from real-world measurements, particularly in urban settings., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This cross-sectional study investigated the relationship between exposure to airborne indoor and outdoor particulate matter (PM) and cardiovascular and respiratory health in a population-based sample of 58 residences in Copenhagen, Denmark. Over a 2-day period indoor particle number concentrations (PNC, 10-300 nm) and PM2.5 (aerodynamic diameter<2.5 μm) were monitored for each of the residences in the living room, and outdoor PNC (10-280 nm), PM2.5 and PM10 (aerodynamic diameter<10 μm) were monitored at an urban background station in Copenhagen. In the morning, after the 2-day monitoring period, we measured microvascular function (MVF) and lung function and collected blood samples for biomarkers related to inflammation, in 78 middle-aged residents. Bacteria, endotoxin and fungi were analyzed in material from electrostatic dust fall collectors placed in the residences for 4 weeks. Data were analyzed using linear regression with the generalized estimating equation approach. Statistically significant associations were found between indoor PNC, dominated by indoor use of candles, and lower lung function, the prediabetic marker HbA1c and systemic inflammatory markers observed as changes in leukocyte differential count and expression of adhesion markers on monocytes, whereas C-reactive protein was significantly associated with indoor PM2.5. The presence of indoor endotoxin was associated with lower lung function and expression of adhesion markers on monocytes. An inverse association between outdoor PNC and MVF was also statistically significant. The study suggests that PNC in the outdoor environment may be associated with decreased MVF, while PNC, mainly driven by candle burning, and bioaerosols in the indoor environment may have a negative effect on lung function and markers of systemic inflammation and diabetes., (Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.)