Emissions nonpoint sources

Nonpoint sources of pollution are more difficult to measure because they often cover large areas or are a composite of numerous point sources. Examples of nonpoint sources include pesticide and fertilizer runoff from agricultural fields, and urban runoff contaminated with pollutants from automobile emissions. Nonpoint sources may not be directly located next to a surface water body pollutants may be transported to surface waters by runoff from the land, by groundwater inflow, or by atmospheric transport. 

Air emissions include point and nonpoint sources (Chapter 4). Point sources are emissions that exit stacks and flares and thus can be monitored and treated. Nonpoint sources are fugitive emissions that are difficult to locate and capture. Fugitive emissions occur throughout refineries and arise from the thousands of valves, pumps, tanks, pressure relief valves, flanges, and so on. Although individual leaks are typically small, the sum of all fugitive leaks at a refinery can be one of its largest emission sources. 

Most agriculturally based pollutants probably return to the environment at points that are difficult to identify and are called nonpoint source emissions. Pesticides leave farms as runoff or leach through the soil. Isolating and treating them is not often possible. While techniques such as ditching and basins are being adopted, the problem of treatment in the dilute state in which pollutants will be isolated is a serious concern. 

The construction of a mass balance model follows the general outline of this chapter. First, one defines the spatial and temporal scales to be considered and establishes the environmental compartments or control volumes. Second, the source emissions are identified and quantified. Third, the mathematical expressions for advective and diffusive transport processes are written. And last, chemical transformation processes are quantified. This model-building process is illustrated in Figure 27.4. In this example we simply equate the change in chemical inventory (total mass in the system) with the difference between chemical inputs and outputs to the system. The inputs could include numerous point and nonpoint sources or could be a single estimate of total chemical load to the system. The outputs include all of the loss mechanisms transport... 

Progress has been made in some areas since 1970. Emissions of pollutants from point sources into air and water have decreased. Toxic releases are decreasing. Some Superfund sites have been cleaned up. Businesses would no longer think of dumping a barrel of waste solvent on the ground at the landfill site so that the barrel could be used again for the same purpose. Control of pollutants from nonpoint sources is still a problem. There is now more international cooperation and discussion of global problems, such as ozone depletion by chlorofluorocarbons and the effect of... 

Nonpoint Source Pollution source that cannot be traced back to a single emission source, such as storm-water runoff. 

The environmental trade-offs between PLA and petro-polymers result from agricultural production of PLA raw materials. Agriculture is one of the major nonpoint source contributors to eutrophication and hypoxia (e.g., within the Gulf of Mexico in the United States) due to the extensive use of fertilizers. Com, which serves as the primary feedstock for PLA in the United States, is one of the worst offenders. Nitrogen and phosphoms are applied as fertilizers to agricultural crops and result in N and P nutrient emissions, which are the primary contributors to hypoxia and eutrophication [29, 30],... 

Stationary point source and nonpoint source inputs to environmental compartments in the coming years will also decline as part of regulatory requirements or simply the size of the remaining lead emission generators in coming years versus their historical impact. For example, only one major primary lead smelter remains in the United States, the facility in Herculaneum, MO. In 1985, there were five major primary lead smelters and refineries (ILZRO, 1982) East Helena, MT Omaha, NE and three in the Missouri Lead Belt. 

The U.S. picture for major point or nonpoint stationary sources for lead emissions has changed in the general direction of significant decline. However, both stationary and mobile sources emitted lead in past decades that remains in receiving environmental compartments. Today, there is only one active primary smelter in the United States, no existing lead additive facility, and a number of the mines have closed. Secondary lead battery... 

It is also important to note that this overview does not deal with every source or possible exposure route. For example, hazardous air emissions, pesticide applications, and many nonpoint waste sources are not... 

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