Diffuse source pollution

Gunningham N, Sinclair D (2005) Policy instrument choice and diffuse source pollution. J Environ Law 17(1) 51—81... 

Diffuse Sources Pollution that comes from a wide range of sources, not from a single source, is said to come from a diffuse source. (See Figure 9.7.) A heavy downpour can cause run-off from farm fields to enter rivers and lakes. This run-off often carries undesirable pollutants, including fecal matter, pesticides, and fertilizer compounds, such as nitrates and phosphates. 

Diffuse Source Pollution Associated with widespread multiple sources, such as those derived from many agricultural practices (e.g. excessive or inappropriate use of fertilisers and/or pesticides), often generating pollutants in moderate to somewhat elevated concentrations in the soils and in the unsaturated zone over large areas, which eventually migrate down to the water table with infiltration fronts during or after rainfall events. 

Fig. 5. Diffusion of pollutants from a point source. PoUutant concentrations have separate Gaussian distributions in both the horizontal (j) and vertical directions. The spread is parameterized by the standard deviations ( O ) which are related to the diffusivity (fQ.

The mechanisms by which a jurisdiction develops its air pollution control strategies and episode control tactics are outlined in Fig. 5-1. Most of the boxes in the figure have already been discussed—sources, pollutant emitted, transport and diffusion, atmospheric chemistry, pollutant half-life, air quality, and air pollution effects. To complete an analysis of the elements of the air pollution system, it is necessary to explain the several boxes not vet discussed. 

Cons - Different models may render very different results - Models are strongly dependent on parameter and data input - Diffuse sources of pollution may be very difficult to model... 

Water resource management strategies need to balance water supply and demand, particularly in the context of droughts or floods, and contend with problems such as diffuse and point source pollution, poor water quality and ecosystem degradation, all within local political and socio-economic frameworks. As water use in one location may influence water quality and availability in another, it is becoming... 

Chemical pollution From a qualitative point of view, an important common issue is the excess of chemicals (fertilisers and pesticides) associated with agrarian and livestock farming diffuse sources and the point-source discharge of (treated and untreated) sewage water. Industrial point-source pollution is not addressed as a relevant issue, but it is assumed that industries operate following the legal rules and only the incomplete elimination of industrial chemicals in urban wastewater treatment plants is perceived as a problem. 

Related to chemical pollution - referring to all kind of contamination (mineral and organic) - there is a clear distinction between point-source pollution and diffuse pollution. It appears that it is easier to take measures for point-source pollution, for instance, the improvement of the wastewater treatment plants, even if the treatments for specific compounds (pesticides, emerging compounds, etc.) still need further research. Measures for diffuse pollution can be more complex because some of them require real political decisions, for instance to interfere on agricultural practices to reduce inorganic and organic fertilisers. 

Egan, B. A., and J. R. Mahon. Numerical modeling of advection and diffusion of urban area source pollutants. J. Appl. Meteorol. 11 312-322, 1972. 

In alpine rivers, dilution will govern the impairment from pollution loads by point or diffuse sources such as treated wastewaters or runoff from agricultural lands. This dilution effect decreases gradually when rivers enter the lower altitude range of a watershed. 

The most abundant hydrocarbon in the atmosphere is methane, CH4. This gas is released from underground sources as natural gas and produced by the fermentation of organic matter. Methane is one of the least reactive atmospheric hydrocarbons and is produced by diffuse sources, so that its participation in the formation of pollutant photochemical reaction products is minimal. 

Landfill leachate is rainwater that has percolated through landfill wastes. It dissolves numerous compounds, many of them toxic. Modern landfills have containment and treatment procedures to prevent this diffuse source of pollution from contaminating ground water. 

Since the 1990s, diffuse sources of pollution have been increasingly contributing to synthetic chemicals present in environmental media. From a review of the literature, diffuse emissions originate from three major sources ... 

Pollution from diffuse sources can be effectively tackled by taxing polluting products and wastes [216, 245]. Examples of chemical taxes include chlorinated solvents in Denmark and Norway [246] and phthalates in articles on the Danish market [269]. The European Environment Agency [245] and the EIK Royal Commission for Environmental Pollution (RCEP) [180] suggest developing new tax bases for hazardous chemicals. The European Commission s Integrated Product Policy also proposes taxation to promote environmentally sound practices through supply chains [247]. 

The approach to considering each pollution source is slightly different, although there will, of course, be circumstances where there is overlap between the categories. In general, diffuse sources of pollution are more difficult to control than point sources, particularly where systems such as pit latrines and septic tanks are established. 

Each country has its own set of requirements for reporting. However, releases from nonpoint sources, although contributing a large share to any industrialized country s pollution burden, are so far included only in a limited number of PRTR systems. These nonpoint, or diffuse, sources include area sources (e.g., residential wood combustion, dry cleaners), mobile sources (e.g., automobiles, aircrafts, trains), biogenic sources (e.g., vegetation and microbial activity), and geogenic sources (e.g., soil erosion and volcanoes). 

The problem of diffuse-source agricultural and mbano-industrial pollution should command special attention, in part because of the complex role played by the unsaturated zone, which can encompass a mix of both contaminant attenuation and contaminant accumulation, with periodic release into the aquifer system. River beds can play a similar role in the case of many industrial pollutions. 

Dijfuse sources are highly dynamic, spread out pollution sources and their magnitude is closely related to meteorological factors such as precipitation. Major diffuse sources under this definition include surface runoff (load from atmospheric deposition), groundwater, erosion (load from eroded material), diffuse loads of paved urban areas (atmospheric deposition, traffic, corrosion) including combined sewer overflows, since these events occur discontinuously over time and are closely related to precipitation (it has to be pointed out that emissions from urban areas are also partly involved in the point source term, so these discharges are not constant in reahty). Both point and diffuse sources contribute to the total contaminant load of rivers. 

The behavior of MTBE through the different environmental compartments has been investigated using various modelling approaches. For example, the EU risk assessment used the simplest type of fugacity models (a Level 1 model) and concluded that from diffuse sources 93.9% of MTBE is in the air phase, 6.0% in the water phase, and 0.05% in the soil phase [2]. However, another study by Environment Canada for Southern Ontario [61] used the Level III model and predicted 56% of MTBE in the air, 42% in surface water, and 0.5% in soil and sediment. As can be observed, models developed so far differed in their predictions of relative MTBE concentrations for relevant environmental compartments and of seasonal concentration variations further, they have hardly considered the formation of transformation products [62]. Moreover, limitations in pollutant environmental data or key physicochemical parameters often make it difficult to validate model predictions. 

For each facility, information is provided concerning the amounts of pollutant releases to air, water and land as well as off-site transfers of waste and of pollutants in wastewater from a list of 91 key pollutants including heavy metals, pesticides, greenhouse gases and dioxins for the year 2007. Some information on releases from diffuse sources is also available and will be gradually enhanced. 

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