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Water uptake routes

Timmerman K, Andersen O. 2003. Bioavailability of pyrene to the deposit-feeding poly-chaete Arenicola marina importance of sediment versus water uptake routes. Mar Ecol Prog Ser 246 163-172. [Pg.361]

To determine acceptable contaminant levels in soils, two primary exposure routes are usually considered (1) inlialation of gases, vapors, or airborne particulate emanating from the site, and (2) ingestion of contamimtted drinking water. Other routes that can contribute to e.xposure include absorption of pollutants tluough direct skin contact and uptake of wtiter or soil contantinants by plants that are part of the food chain. [Pg.364]

In metabolic studies with animals it is often difficult to distinguish between processes carried out by the animal and those performed by resident microorganisms, such as the gut microflora. In the following, the transformations refer to those taking place within the marine animal, whether microbially mediated or otherwise. Metabolic studies with marine animals are faced with further complications because water can be an important uptake route. A chemical, in this instance arsenic in its various forms, may undergo microbial conversions in the water, and the resultant metabolites may be accumulated by the marine animal. Thus, careful experimentation may be required to determine what is occurring inside rather than outside the animal. [Pg.178]

Another important uptake route for chemicals by terrestrial plants and organisms living in soils (e.g., earthworms) is uptake from soil interstitial water and/or by ingestion of soil particles. In particular, uptake of contaminants from soils by certain plant species is of great interest, because this process, which is referred to... [Pg.365]

An important consideration is the relative importance of the water and the diet as a source of chemical uptake in the organism. Equation (30) illustrates that, to a large degree, the relative concentrations of the chemical substance in the water and the diet of the organism control the BAF. In laboratory experiments where bioaccumulation factors are measured, it is therefore important to choose appropriate concentrations CWD and CD, because they affect conclusions drawn about the relative importance of the diet and water as routes of chemical intake. Under field conditions, the bioaccumulation factors in organisms can vary, depending on the relationship between the chemical concentrations in the water and the diet, especially if the chemical is very hydrophobic (log Kow > 5). If the BAF measured in one ecosystem is used to assess the BAF in another ecosystem, an error could be made if this diet/ water concentration relationship or values of kD vary between the ecosystems. [Pg.229]

Perhaps the most difficult aspect of organism behavior to include in media extrapolation procedures is that relating to avoidance. Different species exhibit a diverse array of avoidance behaviors, which they may display in response to natural biotic or abiotic factors in their environment and in response to chemical exposure. Some of the most common include avoidance responses of fish to heavy metals and other contaminants (Sandheinrich 2003), aversion of contaminant-treated diets by birds (Hooper 2003), and drift in stream invertebrates (Sibley et al. 1991 Davies and Cook 1993). Such avoidance behaviors would act to reduce exposure, but are generally ignored in extrapolation approaches. Changes in behavior could potentially have importance in media extrapolation in that they could alter the relative importance of different uptake routes. For example, if a contaminant is partitioned between diet and water, and an exposed species is able to detect and avoid the contaminated food, the relative importance of water as an exposure route could be increased even though total exposure may decrease. [Pg.46]

There is no mechanistic equilibrium-partitioning model for toxic metals available for the soil and sediment compartments. However, the free metal ion concentration in pore water that is considered relevant for uptake in biota (water exposure route) may experimentally or empirically be related to the total metal content of the soil, according to equation 2.1 (above). [Pg.51]

In catfish aquaculture, offensive odors can be rapidly absorbed in the flesh of the fish. The major uptake route for geosmin and MIB is across the gills [18], and these compounds are primarily stored in the adipose tissue [29]. Elimination of these odorous compounds is much slower than the uptake rate, and elimination rate decreases as water temperature decreases and adipose tissue content of the catfish increases [30]. [Pg.354]

The most important uptake route for uranium is ingestion of food and drinking water, as shown in Table 26.1-2 (see Chapter 26.1, Section 26.1.7). The daily dietary intake of U for Ukrainian males is estimated at 7.8 mBq (Shiraishik et al. 1997), with typical daily intake values being 0.16 Bq for 0.0005 Bq for U, and 0.16 Bq for U. Military use of depleted uranium led to inhalation during combat and to shrapnel contamination (Bleise... [Pg.1160]

Exposure pathways for adult amphibians include soils (dermal contact, liquid water uptake), water (dermal contact with surface water), air (cutaneous and lung absorption), and diet (adults are carnivores). All routes of exposure are affected by various physical, chemical, and other factors. Dietary exposure in adults, for example, is related to season of year, activity rates, food availability, consumption rate, and assimilation rates. Knowledge of these modifiers is necessary for adequate risk assessment of mercury as a possible factor in declining amphibian populations worldwide. [Pg.445]

The major route of uptake for PAHs has been debated for years. For the more water-soluble PAHs, it is believed that the main route of uptake is through ventilated water and that the more hydrophobic compounds are taken in mainly through ingestion of food or sediment. There are many variables, such as chemical hydrophobicity, uptake efficiency, feeding rate, and ventilatory volume, which may affect the outcome. The route of uptake may be an important issue for short-term events however, under long-term exposure and equilibrium conditions between water, prey, and sediment, the route of uptake may be immaterial because the same tissue burdens will be achieved regardless of uptake routes. The key assumption of equilibrium between these different compartments may, however, rarely occur for PAHs. [Pg.146]

One route to improve the ionic conductivity of these polymers is to increase the lEC. The presence of a large number of sulfonic groups on the polymer chain has, however, a detrimental effect on the swelling properties of the membrane as an excessive water uptake leads to a lower conductivity and weaker mechanical properties. To overcome such a problem, the idea of cross-linking the membranes seems particularly attractive, as far as they do not become brittle. [Pg.212]


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