Screening, contaminants

Figures 16-3 through 16-5 present the decision network for screening contaminant fate in air, surface water, ground water, and biota. Pathways must be further evaluated to determine the likelihood of population exposure.

Mycotoxicoses are common problems for the poultry industry in warm moist climates and in developing countries in the tropics. Aflatoxins are the most commonly involved mycotoxins. Poultry are normally exposed by consumption of contaminated feed, especially corn. Some developing countries lack the resources to adequately screen contaminated corn. In other instances poultry feed is made from the poor-quality (and contaminated) corn that has been rejected for human consumption. 

Activity (in the body) (Bq) or equivalent Intanal contamination screening Contamination monitors or dose-rate instruments Thyroid monitor Quick and very portable Equipment inexpensive and can be used for other purposes Results available immediately Large throughput possible Not radionuclide-specific No automatic storage of information ... 

Locational considerations include both surficial location and screened interval, ie, the sampling depth. The surficial location is selected based on whether the sample is to represent background quaUty or quaUty at the location of contamination, or potential leak location. In selecting the surficial location, the groundwater flow parameters, velocity and direction, are assumed to be known from other monitoring wells or borings already completed. 

After acid removal, scrap batteries are fed to a hammer mill in which they are ground to <5 cm particles. The ground components are fed to a conveyor and passed by a magnet to remove undesirable contamination. The lead scrap is then classified on a wet screen through which fine particles of lead sulfate and lead oxide pass, and the large oversize soHd particles are passed on to a hydrodynamic separator. The fine particles are settled to a thick slurry and the clarified washwater recirculated to the wet screen. 

Biosensors ai e widely used to the detection of hazardous contaminants in foodstuffs, soil and fresh waters. Due to high sensitivity, simple design, low cost and real-time measurement mode biosensors ai e considered as an alternative to conventional analytical techniques, e.g. GC or HPLC. Although the sensitivity and selectivity of contaminant detection is mainly determined by a biological component, i.e. enzyme or antibodies, the biosensor performance can be efficiently controlled by the optimization of its assembly and working conditions. In this report, the prospects to the improvement of pesticide detection with cholinesterase sensors based on modified screen-printed electrodes are summarized. The following opportunities for the controlled improvement of analytical characteristics of anticholinesterase pesticides ai e discussed ... 

Figure 16-1 and 16-2 present the decision networks that guide contaminant release screening analysis. Figure 16-1 deals with contaminants in or under the soil and Fig. 16-2 addresses aboveground wastes. Any release mechanisms evident at the site will require a further screening evaluation to determine the likely environmental fate of the contaminants involved. 

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