Emissions Of Primary Pollutants Research Articles

Comparison between weekend and weekday ozone concentration in large cities in France

This paper examines ozone data from five large French cities (Marseilles, Lyon, Paris, Strasbourg and Toulouse) in spring and summer over a three-year period to study the possible influence of local primary pollutant emissions. In these cities the level of traffic emission varies according to the day of the week. There is a decrease of about 25% in traffic emissions between non-consecutive Tuesdays and Sundays. Traffic emissions on Fridays are about 40% more than on non-consecutive Sundays whereas they seem to be similar for non-consecutive Tuesdays and Thursdays. Despite this variation in traffic emissions between Fridays and Sundays, 85% of daily ozone maxima are identical for all days compared; in 15% of cases, percentiles of daily ozone maxima vary by about 20% at the most. This difference is observed for the highest values of daily ozone maxima that we can find both in rural and urban sites. Marseilles is the most pollution-sensitive city; every site of this area is concerned, which gives a regional origin to ozone variability. In the less-populated Toulouse area, differences between ozone on Fridays and Sundays are less significant. Our results show the importance of advection phenomena of ozone. It calls into question strategies of local reductions in traffic during ozone episodes.

Development and regional application of a photochemical oxidant dispersion/reactivity model

In this paper we use the urban airshed model IV, simultaneously including the dispersion and the tropospheric chemistry as described in version IV of the carbon bond (CB-IV). The modelling area covers northern France and a part of Belgium, with a total surface area of 15 000 km2. The wind field is calculated using the Meteo France ALADIN code and temperature vertical profiles from radiosoundings. The primary pollutant emission data are obtained from measurements in industrial sources and from a large amount of experimental data for mobile sources. The photolysis frequencies were calculated using two different spectroradiometers to measure the actinic flux. In this paper we described the ozone date for the episode on 13 May 1998.

Low and high NO x chemical regimes in an urban environment

In this work, a chemistry-transport box model, derived from the CHIMERE model, is used in order to examine the existence of different chemical regimes, known as the low NO x and high NO x regimes, and the existence of multiple equilibria in an urban environment. From an operationnal point of view, the existence of chemical regimes of low NO x and high NO x type and of multiple equilibria is of paramount importance for the effectiveness of the air quality policies. For the urban photochemical system under consideration, we determine the equilibria associated with primary pollutant emissions varying in a range of values typical of the parisian urban area. The influence of several variables on these regimes is also studied, through the following parameters: wind speed, upstream ozone concentration, cloudiness.

Evaluation of urban pollution abatement strategies by a photochemical dispersion model

High ozone levels are regularly reached during the summer period in Italian urban areas, indicating the need for a careful design of primary pollutants emission reduction strategies. In this perspective, the CALGRID-CALMET modelling system has been applied to the Milano metropolitan area and its suburbs, a very industrialised and populated region in the Po Valley. A simulation domain of 100 x 100 km² has been considered and a summer period, characterised by high photochemical activity, has been selected. Hourly emissions have been derived by spatially and temporally disaggregated national inventories data, while standard upper-air and ground based meteorological data have been used as inputs to the CALMET pre-processor. The modelling system has been applied for the evaluation and comparison of different emission control strategies. Since the main source of pollutants in the area is actually traffic, the impact of cleaner fuels and cleaner cars has been investigated.

Measurements of peroxyacyl nitrates (PANS) in Mexico City: implications for megacity air quality impacts on regional scales

Peroxyacyl nitrates (PANs) were measured using gas chromatography with electron capture detection (GC/ECD) in north central Mexico City during February–March of 1997. Peroxyacetyl nitrate (PAN) was observed to exceed 30 ppb during five days of the study, with peroxypropionyl nitrate (PPN) and peroxybutryl nitrate (PBN) reaching 6 and 1 ppb maximum, respectively. Levels of total PANs typically exceeded 10 ppb during the period of measurement and showed a very strong diurnal variation with PANs maximum during the early afternoon and falling to less than 0.1 ppb during the evening hours. These levels of PANs are the highest reported values in North America (and the world) for an urban center, since levels of approximately 30 ppb were reported during the late 1970s in the Los Angeles area (South Coast Air Basin, Tuazon et al., 1978). Hydrocarbon measurements indicate that the levels of olefins, specifically butenes are significant in Mexico City. A time series taken of source indicator hydrocarbons taken before and during a Mexican National Holiday with reduced automobile traffic clearly show that mobile sources of butenes are as important as liquefied petroleum gas. Observations of 10–40 ppb C methyl- t-butyl ether (MTBE) are consistent with MTBE/gasoline fuel usage as a source of isobutene and formaldehyde. Both these reactive species can lead to increased oxidant and PAN formation. The strong diurnal profiles of PANs are consistent with regional clearing of the Mexico City air basin on a daily basis. Estimates are given using a simple box model calculation for a number of key primary and secondary pollutant emissions from this megacity on an annual basis. These calculations indicate that megacities can be important sources of both primary and secondary pollutants, and that PANs produced in megacity environments are likely to contribute strongly to regional scale ozone and aerosol productions during long range transport.

Application of a photochemical grid model to milan metropolitan area

High ozone levels are regularly reached during summer period in South-European urban areas, calling for careful design of primary pollutants emission reduction strategies. In this perspective the CALGRID modelling system has been applied to Milan metropolitan area, located in the Po Valley, the most industrialised and populated area in Italy. For the first modelling exercise, a simulation domain of 100×100km2 has been considered and a summer period, characterised by high photochemical activity, has been selected. Hourly emissions have been derived by spatially and temporally disaggregating national inventories data, while standard upper-air and ground-based meteorological data have been used as input to the CALMET pre-processor. A careful analysis of simulation results versus local network monitoring data has revealed some critical points, related to both modelling assumptions and practical data availability. A satisfactory reproduction of daytime ozone behaviour has been, in fact, accomplished, both in urban and suburban sites, while nighttime primary pollutants accumulations and consequent ozone consumption simulated by the model have not found correspondence in the measurements. Nitrogen dioxide has been also successfully modelled, mostly in city surroundings, whereas higher discrepancies have been found in some urban stations. Possible explanations of these facts are discussed in the paper, giving an insight for further work.

Parameterization of urban subgrid scale processes in global atmospheric chemistry models

We have derived a parameterization consisting of a set of analytical expressions that approximate the predictions by the California Institute of Technology ‐ Carnegie‐Mellon University (CIT) Urban Airshed Model for the net export to the environment (i.e., effective emissions) of several chemical species, as functions of 14 input parameters. For each species, effective emissions are a function of actual urban emissions of this and other species and of other urban domain properties such as meteorology. Effective emissions may be “aged” emissions of primary pollutants or actual production of secondary pollutants. To develop the parameterization we have applied the probabilistic collocation method, which uses the probability density functions of the inputs to generate a set of orthogonal polynomials. These polynomials are then used as the basis for a polynomial chaos expansion that approximates the actual response of the CIT model to its inputs. We assume that seasonal variations can be represented by sinusoidal functions. The parameterization provides a computationally very efficient simulation of the actual model behavior. We have compared the outputs of the parameterization with the outputs of the CIT model, and we conclude that it gives a quite good approximation for effective emissions, at least in the regions of highest probability of the input parameters. This parameterization is applicable to detailed uncertainty and sensitivity analyses and enables computationally efficient inclusion of urban‐scale processes as subgrid scale phenomena in global‐scale models.

Ozone distributions over the los angeles basin: Three-dimensional simulations with the smog model

The UCLA Surface Meteorology and Ozone Generation (SMOG) model has been applied to simulate and analyze the distributions of ozone in the Los Angeles basin on 27 and 28 August 1987, during the Southern California Air Quality Study (SCAQS). SMOG is an integrated air pollution modeling system that includes the coupled effects of meteorology, pollutant sources and dispersion, photochemistry and aerosol microphysics, and radiative processes. High surface ozone concentrations are predicted along the slopes of the surrounding mountain barriers and in the eastern basin, as observed. The pattern of surface ozone concentrations is shown to be influenced by the evolution of oxidants within the temperature inversion that typically blankets the Los Angeles basin. In the past, dense layers of ozone have been observed to be embedded within the temperature inversion, but their origin has remained unexplained. The present model simulations reproduce these and other three-dimensional structures in the ozone distribution, as documented by measurements in the basin. The high concentrations of oxidants aloft are explained through a detailed dynamical/chemical mechanism. High mountains surrounding the Los Angeles basin block the dispersion of ozone and other pollutants and generally contain them within the basin. At the same time, vertical circulations associated with the interaction of the sea-breeze and mountain slope winds inject pollutants into the base of the inversion and create high concentrations of ozone, PAN, nitric acid, organic nitrates and a variety of other pollutants, including aerosols. The contrast between ozone concentrations at the surface and in these elevated layers can be enhanced in the evening by NO emissions, which titrate ozone near the surface. The elevated layers act as a reservoir for aged pollutants, which can be mixed downward on subsequent days to enhance surface concentrations. The recirculation of pollutants in the Los Angeles basin is thus reinforced by the presence of these oxidant layers, and may be responsible for the rapid increase in surface ozone concentrations often seen in the morning, particularly in the eastern basin where emissions of primary pollutants are relatively small. The impact on surface ozone concentrations of recirculated photochemically aged air is estimated to be as high as 8 pphmv in the eastern Los Angeles basin. These simulations represent the first quantitative description of the role of pollutants aloft on surface air quality.

Source‐oriented model for air pollutant effects on visibility

A source‐oriented model for air pollutant effects on visibility has been developed that can compute light scattering, light extinction, and estimated visual range directly from data on gas phase and primary particle phase air pollutant emissions from sources. The importance of such a model is that it can be used to compute the effect of emission control proposals on visibility‐related parameters in advance of the adoption of such control programs. The model has been assembled by embedding several aerosol process modules within the photochemical trajectory model previously developed for aerosol nitrate concentration predictions by Russell et al. [1983] and Russell and Cass [1986]. These modules describe the size distribution and chemical composition of primary particle emissions, the speciation of organic vapor emissions, atmospheric chemical reactions, transport of condensible material between the gas and the particle phases, fog chemistry, dry deposition, and atmospheric light scattering and light absorption. Model predictions have been compared to observed values using 48‐hour trajectories arriving at Claremont, California, at each hour of August 28, 1987, during the Southern California Air Quality Study. The predicted fine particle concentration averages 62 μg m−3 compared to an observed value of 61 μg m−3, while predicted PM10 concentrations average 102 μg m−3 compared to an observed average of 97 μg m−3. The size distribution and chemical composition predictions for elemental carbon, sulfate, and sodium ion agree with observations to within plus or minus a few micrograms per cubic meter, while ammonium and nitrate concentrations are underpredicted by the base case model by 3 to 7 μg m−3 on average. Light‐scattering coefficient values are calculated from the predicted aerosol size distribution and refractive index, and the model predictions agree with measured values on average to within 19%. The advantages and limitations of the modeling procedure are discussed.

Analysis of Gaseous Hydrogen Peroxide Concentrations in Raleigh, North Carolina

Gas-phase total peroxides and hydrogen peroxide (H2O2) were monitored in the ambient air in downtown Raleigh, North Carolina as part of the Southern Oxidant Study-Southern Oxidants Research Programs on Ozone Non-Attainment (SOS-SORP/ONA). These measurements were made during September 8–16, 1991, using the continuous dual-channel fluorometric analyzer based on the horseradish peroxidase method. Measurements were also made of other photochemical oxidants and trace gases (O3, NO, NO2) NOX SO2, CO, HCHO) and meteorological parameters. Concentrations of H2O2 showed a diurnal variation with maximum concentrations in the afternoon (1400-1800) EST. The mean of all observations was 0.2 ppbv and the range measured was below the level of detection (~0.05 ppbv) to about 1 ppbv. An observational-based statistical analysis utilizing Multivariate Principal Component Analysis (PCA) was applied to the data to determine the underlying processes. Four physicochemical components were found to account for ~86 percent of the variability of all the parameters. Application of Kaiser’s Varimax orthogonal rotation on the four retained principal components allowed in the physical interpretation of the first four Principal Components as being: photochemical processes, primary pollutant concentrations, emission and transport of SO2, and air mass type. A multiple linear regression analysis was carried out by regressing H2O2 on all the other physicochemical air quality variables and/or a combination of these. It was found that all the variables put together account for 53 percent of the variability in M202 concentrations. Ozone alone accounts for 11 percent of the variability, and this value increased to 33 percent when temperature, relative humidity and solar radiation were added to ozone. PCA was applied again to the data set (excluding H2O2) and the principal components obtained were used as independent variables for the regression analysis of H2O2. It was found that photochemical activity and primary pollutant concentrations were the most significant factors in controlling gaseous H2O2 concentrations in Raleigh during the measurement period.

The impact of motor vehicles on air pollutant emissions and air quality in the UK — An overview

This paper will attempt to summarise the contribution of motor vehicles to the emissions and air quality in terms of the more important air pollutants in the UK. It is important in this context to distinquish between primary pollutants which may affect a given target in the form in which they are emitted, and secondary pollutants which undergo or are formed by, reactions in the atmosphere between source and target. In the motor vehicle context one may list the more important primary pollutants as CO, CO 2, NO, NO 2, SO 2, smoke and particulate material, lead and the range of organic compounds known generally as volatile organic compounds (VOCs). Secondary pollutants in this context are ozone, PAN (peroxyacetyl nitrate), NO 2, sulphate and nitrate aerosols and the end products of atmospheric oxidation and rain chemistry H 2 SO 4 and HNO 3 and others implicated in the “acid rain” issue. This paper will discuss the estimates of UK emissions of primary pollutants and the precursors of secondary pollutants (where data are available) and will give an indication of the methods used in their calculation. A brief discussion will be given of how vehicular contributions to measured air quality can be quantified using numerical modelling and air quality data and finally some indication of future trends in vehicle emissions will be given.

A methodology for the cost/health-benefit analysis of photochemical smog control

A methodology for the analysis of the costs and health-related benefits of photochemical smog control is presented. This methodology combines information on the cost of primary pollutant emission control, the effects of emission control on ambient concentrations of air pollutants, and the health effects of these air pollutants. The application of the methodology is illustrated for the control of ozone (O 3) and nitrogen dioxide (NOO 2) short-term concentrations in the Los Angeles metropolitan area.

Seasonal variations in light scattering in the New York region and their relation to sources

Light scattering data collected during two periods of intensive sampling in New York City (one during summer months and one during winter months) are discussed and analyzed for diurnal patterns, their relationship to pollutant emission sources, meteorological parameters, and the size distribution and chemical composition of the ambient aerosol. The lack of a diurnal pattern for light scattering in summer in combination with a strong positive association with ozone and wind direction dependency suggests that in summer the transport of an aged aerosol in photochemically rich air masses rather than local emissions of primary pollutants is largely responsible for the observed levels of light scattering in New York City. Winter levels of light scattering observed in New York City, while approx. 50% lower than summer levels, were much less dependant on wind direction and closely related to pollutant emissions from local sources. This suggests that locally generated aerosol dominates light scattering in the winter. Particles 0.1–1.3 μm in diameter were strongly correlated with light scattering in New York City during both summer and winter periods. However, a given volume of aerosol between 0.1 and 1.3 μm scattered more light in summer than in winter, indicating the fresher nature of the winter aerosol. Variance in dry particulate light scattering was found to principally account for light extinction variance (calculated from airport visibility observations) in summer and winter. Sulfate aerosol was strongly correlated with light scattering during both summer and winter periods.