Regional scale

Problems of air pollution exist on all scales from extremely local to global. These are divided in this chapter into five different scales local, urban, regional, continental, and global. The local scale includes up to about 5 km. The urban scale extends to the order of 50 km. The regional scale is from 50 to 500 km. Continental scales are from 500 to several thousand km. Of course, the global scale extends worldwide. 

At least three types of problems contribute to air pollution problems on the regional scale. One is the carryover of urban oxidant problems to the regional scale. With the existence of major metropolitan areas in close proximity, the air from one metropolitan area, containing both secondary pollutants formed through reactions and primary pollutants, flows on to the adjacent metropolitan area. The pollutants from the second area are then added on top of the "background" from the first. 

In a relatively small continental area such as Europe, there is not much difference between what would be considered the regional scale and the continental scale. However, on most other continents there would be a difference between what is considered regional and what continental. Perhaps of greatest concern on the continental scale is that the air pollution policies of a nation are likely to create impacts on neighboring nations. Acid rain in Scandanavia has been considered to have had impacts from Great Britain and Western Europe. Japan has considered that part of their air pollution problem, especially in the western part of the country, has origins in China and Korea. Cooperation in the examination of the North American acid rain problem has existed for a long time between Canada and the United States. 

The harmful effects of air pollutants on human beings have been the major reason for efforts to understand and control their sources. During the past two decades, research on acidic deposition on water-based ecosystems has helped to reemphasize the importance of air pollutants in other receptors, such as soil-based ecosystems (1). When discussing the impact of air pollutants on ecosystems, the matter of scale becomes important. We will discuss three examples of elements which interact with air, water, and soil media on different geographic scales. These are the carbon cycle on a global scale, the sulfur cycle on a regional scale, and the fluoride cycle on a local scale. 

The spatial scale of a stationary network is determined by monitoring objectives. Spatial scales include microscale (1-100 m), middle scale (100 m-0.5 km), neighborhood scale (0.5-4.0 km), urban scale (4-50 km), and regional scale (tens to hundreds of km). Table 15-1 shows the relationship between spatial scale and monitoring objectives (1). 

Lamb, R. G., "A Regional Scale (1000 km) Model of Photochemical Air Pollution. Part... 

Certainly, photochemical air pollution is not merely a local problem. Indeed, spread of anthropogenic smog plumes away from urban centers results in regional scale oxidant problems, such as found in the NE United States and many southern States. Ozone production has also been connected with biomass burning in the tropics (79,80,81). Transport of large-scale tropospheric ozone plumes over large distances has been documented from satellite measurements of total atmospheric ozone (82,83,84), originally taken to study stratospheric ozone depletion. 

Budgets and cycles can be considered on very different spatial scales. In this book we concentrate on global, hemispheric and regional scales. The choice of a suitable scale (i.e. the size of the reservoirs), is determined by the goals of the analysis as well as by the homogeneity of the spatial distribution. For example, in carbon cycle models it is reasonable to consider the atmosphere as one reservoir (the concentration of CO2 in the atmosphere is fairly uniform). On the other hand, oceanic carbon content and carbon exchange processes exhibit large spatial variations and it is reasonable to separate the... 

To this point, direct human impacts on the hydrosphere have remained restricted to the regional scale. Although they can still be important, particularly in terms of water supply, these direct manipulations of the hydrologic cycle are unlikely to affect the global water balance significantly. However, this is not to suggest that the global water cycle is immune to human influence its close ties to other physical and... 

Platt, T. and Sathyendranth, S. (1988). Oceanic primary production Estimation by remote sensing at local and regional scales. Science 241,1613-1620. 

Ropelewski, C. F. and Halpert, M. S. (1987). Global and regional scale precipitation patterns associated with the El Nino/Southem Oscillation. Mon. Wea. Rev. 115,1606-1626. 

Another problem of EGAs is that they are non-site-specific. The reasons for this lie in the fact that they include the whole life cycle of systems with resources which may originate in different countries and waste products and emissions which may distribute globally. They deal with factual inputs, outputs and the environmental impact potentials of the system under investigation on a global, and, in some cases, regional scale. Yet, they do not address the intrinsic risks resulting from the system itself. However, a combination with risk assessment methods can be used to close this gap. 

The second process, that of RGHg deposition together with particulate matter, has been addressed in various regional scale modeling studies for some time, but only recently has it been considered for direct measurement. Reactive gaseous Hg exhibits the characteristics of a so-called sticky gas and is cotmnonly modeled in the same fashion as nitric acid vapor (e.g., USEPA 1997 Bullock and Brehme 2002). 

Frescholtz 2002). Although ongoing and new planned field and laboratory studies are designed to further test this hypothesis, we feel that it is warranted at this time to develop a pilot-scale network of aimual ecosystem fluxes of THg in TF and LF as indicators of total atmospheric deposition. These fluxes can then be compared with measured wet plus modeled diy deposition based on both inferential and regional-scale models to develop independent estimates of total atmospheric deposition for forested catchments. We also believe that this approach could eventually be applied to a national network, such as the MDN. Although this method is best aimed at forested sites, ongoing research will address methods appropriate for other ecosystems. 

Larsen DP, Kincaid TM, Jacobs SE, Urquhart NS. 2001. Designs for evaluating local and regional scale trends. Bioscience 51 1069-1078. 

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