The focus in the present study is the spatialvariation of anthropogenic volatile organic carbon compounds (VOC), mainly benzene and toluene, in parks and their built-up surroundings. Case studies were located in two large Scandinavian cities and measurements were made two meters aboveground level in maximum traffic periods. The results showedlarge variations in time and space but despite high pollutionlevels in the streets the air in parks and non-traffickedbuilt-up areas are substantially cleaner. The pollutantconcentration inside a large park decreased to a low level(i.e. 1/3 to 1/9 the concentration at the source) in a shortdistance (<40 m). An analysis showed that measured VOC wasassociated with fresh emissions, suggesting that the localtraffic intensity was the main governing parameter. It is,however, obvious that the spatial pattern of pollution is theresult of a combination of many different factors and variablesincluding traffic intensity, weather, local climate, land useand the character of park border.

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described using a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent-scale management and regulatory strategies for chemicals.

Ongoing deliberations on the regulation of semivolatile organic chemicals require the assessment of chemical transport in atmospheric and marine systems. The characteristic travel distance was proposed as a measure for the transport potential in air and water. However, the existing definition treats the transport processes separately. It is shown that combined transport in coupled air-ocean systems can accelerate the overall transport into remote regions. Concentration ratios in air and water change with distance from sources depending on the initial concentration ratio and on the difference between the transport velocities. A measure is suggested facilitating the chemical screening with respect to transport potentials in such air-ocean systems. A case study for α and γ-hexachlorocyclohexane shows that the suggested measure qualitatively reveals the transport potentials of these chemicals and exemplifies possible concentration patterns.

Although confined animal production generates enormous per-unit-area quantities of waste, wastewater from dairy and swine operations has been successfully treated in constructed wetlands. However, solids removal prior to wetland treatment is essential for long-term functionality. Plants are an integral part of wetlands; cattails and bulrushes are commonly used in constructed wetlands for nutrient uptake, surface area, and oxygen transport to sediment. Improved oxidation and nitrification may also be obtained by the use of the open water of marsh-pond-marsh designed wetlands. Wetlands normally have sufficient denitrifying population to produce enzymes, carbon to provide microbial energy, and anaerobic conditions to promote denitrification. However, the anaerobic conditions of wetland sediments limit the rate of nitrification. Thus, denitrification of animal wastewaters in wetlands is generally nitrate-limited. Wetlands are also helpful in reducing pathogen microorganisms. On the other hand, phosphorus removal is somewhat limited by the anaerobic conditions of wetlands. Therefore, when very high mass removals of nitrogen and phosphorus are required, pre- or in-wetland procedures that promote oxidation are needed to increase treatment efficiency. Such procedures offer potential for enhanced constructed wetland treatment of animal wastewater.