Contamination pathway

Aqueous trip blanks sometimes accompany soil samples collected into metal liners or glass jars. In this capacity they do not provide any meaningful information. Soil samples do not have the same contamination pathway as water samples because they are not collected in 40-milliliter (ml) VOA vials with PTFE-lined septum caps. In addition, soil does not have the same VOC transport mechanism as water does (adsorption in soil versus dissolution in water). There are other differences that do not permit this comparison different sample handling in the laboratory different analytical techniques used for soil and water analysis and the differences in soil and water MDLs. That is why the comparison of low-level VOC concentrations in water to VOC concentrations in soil is never conclusive. 

Trip blanks prepared in vials and containing aliquots of methanol or analyte-free water accompany soil samples collected in a similar manner for low concentration VOC analysis according to EPA Method 5035. In this case, field samples and trip blanks have the same contamination pathway when exposed to airborne contaminants and the same VOC transport mechanism. These trip blanks provide important information, which may enable us to recognize the artifacts of improper sample handling, storage, or shipping. 

On the other hand, public or private well water supplies in close proximity to existing or abandoned landfills are placed in the highest priority category because the potential for a more direct contamination pathway is obvious. 

There is a disadvantage with the use of environmental samples to assess the radionuclide concentrations in the environment. This arises since there is the potential for contamination of such samples from previously deposited material. This material may or may not originate from the source of interest and there may be significant contributions from Chernobyl and weapons fallout. Such contamination pathways include soil splash, the deposition of resuspended material and root uptake. 

The Pollutant Linkage Concept. A further concept within the definition—the contaminant-pathway-receptor approach—is elaborated in the statutory guidance. This concept has, in recent years, come to represent the predominant intellectual framework for risk assessment in general20 21 and has underpinned the development of contaminated land technical thinking. Unless a particular receptor could be harmed, through a defined pathway, by an identified contaminant, then land cannot be considered to meet the definition of contaminated land. 

The UK follows the widely recognised contaminant-pathway-receptor concept for assessing risks from contaminated land.4-8 This contaminant-pathway-receptor relationship is called a pollutant linkage.7 Receptors may, for example, be humans, surface water, groundwater, buildings, protected ecosystems or property, including livestock and crops. 

Connected with the adoption of a risk-based methodology is the source-pathway-target or contaminant-pathway-receptor philosophy. This philosophy states that, in order for harm to have occurred, or for there to be a risk of harm occurring, contaminants must have been able to reach relevant receptors via specific environmental migration pathways. Where such a relationship exists between a contaminant, a pathway and a receptor at a site, a pollutant linkage is said to exist. 

In the initial stages of assessing a site, the contaminant-pathway-receptor philosophy can be used to exclude the site from further consideration on qualitative grounds when one or more of the three components is missing. For example, if the contamination is encapsulated in a sealed on-site cell which prevents the ingress or egress of precipitation, vapours and leachate, and animal or plant contact cannot occur, then no pathways exist and hence no pollutant linkages exist. The land cannot, therefore, be classified as contaminated land. 

Figure 5.6 BIOPATH compartment structure for the Ranstad Site, together with the major contamination pathways for uranium.

Figure 13.3. a) Contamination pathways with and without contact and b) transfers between packaging and food... 

Macdonald RW, Hamer T, Fyfe J Recent climate change in the arctic and Its impact on contaminant pathways and interpretation of temporal trend data, Sci Total Environ 342(l-3) 5-86, 2005. 

Fig. 3 Contaminant pathways summary. Contaminants are generically identified as X, X, Xj, and X (a molecule), X + (a cation), and X (a radical). The arrows for both unit cell and catalyst layer levels refer to species movements. At the catalyst level, arrows indicate either species adsorption/desorption or reactions between species. BP bipolar plate, CL catalyst layer, FFC flow-field channel, GDL gas-diffusion layer, M membrane...

For a health hazard to exist, there must be a contaminant pathway from the soil to the biota. Firstly the contaminant must reach the location of the target biota, and secondly, it must be able to enter the target biota. Both mobility and bioavailability depend strongly on chemical speciation (the chemical form in which the contaminant metal is present). Hazard via aqueous pathways will be low where contaminants are only released slowly from particles, or in non-bioavailable dissolved forms. However, poorly soluble metal compounds are often chronically toxic by inhalation, because particles have a long residence time in the lungs. 

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