Transport modeling particulate

Examination of equation 5 shows that if there are no chemical reactions, (R = 0), or if R is linear in and uncoupled, then a set of linear, uncoupled differential equations are formed for determining poUutant concentrations. This is the basis of transport models which may be transport only or transport with linear chemistry. Transport models are suitable for studying the effects of sources of CO and primary particulates on air quaUty, but not for studying reactive pollutants such as O, NO2, HNO, and secondary organic species. 

The catalyst and particulate filter models were developed individually with different university partners. They are described in the following sections. A key issue for all models is robustness and scalability as the applications range from passenger cars to heavy-duty commercial vehicles. The models are physical and chemically based, consisting of a transport model for heat and mass transfer phenomena in the monolith in gas and solid phases, cf. Fig. 6. The monolith reactor modeling is discussed in more detail in Section III. 

The Atmospheric Chemistry Transport modelling system used is based on the off-line coupled CAMx and HIRLAM models has been developed to simulate particulate and gas-phase air pollution on different scales. It has been used to simulate short and longterm releases of different chemical species and air pollution episodes. At present it is run in a pre-operational mode 4 times per day based on 3D meteorological fields produced by the HIRLAM NWP model. Currently this modelling system is setup to perform chemical weather forecasts for a series of chemical species (such as O3, NO, NO2, CO and SO2) and forecasted 2D fields at surface are available for each model as well as an ensemble of models (based on 12 European regional air quality models). The simulated output is publicly available and it is placed at the ECMWF website (http //gems.ecmwf.int/d/products/raq/forecasts/) of the EC FP6 GEMS project. 

It is a promising perspective to integrate the sediment transport model described in Kuhrts et al. (2004) into the biogeochemical model components of Neumann et al. (2002) to identify the transport paths of organic and inorganic particulate matter from the sources (rivers and primary production in the surface layer) to the deposition areas in the deep basins, where accumulation of new sediment is observed. 

Meixner, F. X., K. P. Muller, G. Aheimer, and K. D. Hofken (1985). Measurements of gaseous nitric acid and particulate nitrate. In Physico-chemical Behaviour of Atmospheric Pollutants , (F. A. A. M. De Leeuw and N. D. Van Egmond, eds.) COST Action 611, Proc. Workshop Pollut. Cycles Transport-Modelling Field Experiments, Bilthoven, The Netherlands, pp. 103-114. 

Modeling particulate transport, or various process phases, has been attempted only relatively recently. Sayre (20) gave a very sound basis for further work by using a momentum solution of the two-dimensional convection-diffusion equation characterizing particle transport when additional terms for sedimentation, bed adsorbance, and re-entrainment (erosion) are included. He showed, with extensive hypothetical calculations, which hydrodynamic parameters are important and how they could be quantified. He was also able to show that his concept of bed adsorbance and re-entrainment requires further elucidation and indicated that there might be a turbulence effect on the sedimentation step. Hahn et al. 

A Physicochemical and Hydromechanic Concept for Modeling Particulate Transport and Deposition... 

Figure 1, Building blocks of the particulate transport model representing the most important physical and chemical processes. Control variables and interrelationships are indicated.

Particle characterisation can be applied to both core samples and surface sediments to obtain information on the impacts of changes through time at a site or the impacts of contemporary emissions across a region, respectively. Such information is useful for policy formulation and in terms of targeted emission reductions, whether to protect a sensitive environment or the health of a population, source identification for airborne pollutants is vital. Supporting evidence can also be provided for long-range transport models as particulate sources may be identified from external sources (e.g. Davies et al., 1984). 

Particle Transport. Because many organic chemicals bind with aquatic particulate matter, particle transport can determine the fate of compounds. Sediment transport has been of interest to the engineering profession for many years. Many discussions of the dynamics of fluvial sediment transport have appeared in the literature (11, 12). As with hydrodynamic transport, one strategy for environmental modeling is to "piggy-back the transport of sorbed chemicals on a model of transport of the sediment phase. 

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