Biota sorption processes

The dominant transport process from water is volatilization. Based on mathematical models developed by the EPA, the half-life for M-hexane in bodies of water with any degree of turbulent mixing (e.g., rivers) would be less than 3 hours. For standing bodies of water (e.g., small ponds), a half-life no longer than one week (6.8 days) is estimated (ASTER 1995 EPA 1987a). Based on the log octanol/water partition coefficient (i.e., log[Kow]) and the estimated log sorption coefficient (i.e., log[Koc]) (see Table 3-2), ii-hexane is not expected to become concentrated in biota (Swann et al. 1983). A calculated bioconcentration factor (BCF) of 453 for a fathead minnow (ASTER 1995) further suggests a low potential for -hcxanc to bioconcentrate or bioaccumulate in trophic food chains. 

Processing of the triolein alone (i.e., without analyzing the LDPE as well) is not encouraged for a number of reasons. First of all, the LDPE constitutes a significant part of the total SPMD sorption capacity, in contrast to biota, where the sorption capacity of the non-lipid phase is often considered to be negligible. Data on membrane-lipid partition coefficients (/fmc) is very limited, but the available... 

All natural systems are dynamic, and appropriate attention should be directed to kinetic processes such as sorption and desorption, and to the significance and complexities arising from abiotic transformation and the metabolism of xenobiotics by biota. 

PROBABLE FATE photolysis , no direct photolysis, indirect photolysis is too slow to be important, atmospheric and aqueous photolytic half-life 144-200 days oxidation not an important process, photooxidation half-life in water 44-584 days, photooxidation half-life in air 2.9-29 hrs hydrolysis too slow to be important (half-life of several years) volatilization not a likely transport process, should not evaporate from soil or water sorption sorption onto particles and biota and complexation with humic materials are most important transport processes, attaches strongly to soil particles biological processes bioaccumulation and metabolization by many organisms, and biodegradation are all very important fates... 

PROBABLE FATE photolysis, may be important, but is probably impeded by adsorption, photooxidation by U.V, in aqueous medium (Ty 90-95°C time for the formation of CO, (% of theoretical) 25% 75.3 hr, 50% 160.6 hr, 75% 297.4 hr, photooxidation half-life in air 6.81 hrs-2.i du>s, degrades quickly by photochemically produced hydroxyl radicals, with an estimated half-life of 29 hr oxidation-, chlorine and/or ozone in sufficient quantities may oxidize fluorene hydrolysis, not an important process volatilization probably not an important transport process, volatilization half-lives from a model river and a model pond 15 and 167 respectively sorption adsorption onto particles, biota, and sediments is probably the dominant transport process, half-life in soil ranges from 2-64 days biological processes bioaccumulation is short-term, metabolization and biodegradation are very important fates in estuarine waters 15pg/L, 12% adsorbed on particles after 3 hr... 

PROBABLE FATE photolysis low solubility probably hinders photolysis, relatively unimportant fate, atmospheric and aqueous photolytic half-life 0.68-2.04 hrs oxidation chlorine and/or ozone in sufficient quantities can oxidize dissolved pyrene, photooxidation half-life in air 0.802-8.02 hrs hydrolysis not important volatilization probably not as important as adsorption as a transport process sorption adsorption onto suspended particles, biota, and sediment is probably the dominant transport process biological processes short-term bioaccumulation, metabolization and microbial degradation are the principal fates... 

The transfer of molecules from solution into an environmental solid phase such as a soil or sediment is referred to as sorption, with the reverse process usually called desorption (Karickhoff, 1984 Weber et al., 1991). A variety of solid phases are available in the aquatic environment small suspended particles, both living and nonliving, the anatomical surfaces of larger biota such as fish, and bulk soils and bottom sediments. Even colloidal organic solutes such as humic macromolecules might be thought of as separate phases to which a dissolved molecule could be sorbed. Each of these surfaces may be thought of as a source or a sink for compounds in solution. 

Properties of both the contaminants and the target environmental components determine the effective exposure levels, which in turn depend on several processes, such as propagation, distribution, accumulation, soil/sediment sorption and abiotic (e.g. hydrolysis and photolysis) and biotic (e.g. microbial) transformation. Several models of varying complexity have been developed to calculate and predict the distribution of chemicals in the environment (OECD, 1989a, 1993c). Most of them are derived from the Mackay model (Mackay, 1979 Mackay and Paterson, 1981, 1982, 1990, 1991 Mackay, Paterson and Shiu, 1992) to estimate the environmental compartment (e.g. air, soil, water or biota), in which the chemicals are most likely to be found. Based on the... 

The concentration, behavior, and eventual fate of an organic compound in the aquatic environment are determined by a number of physico-chemical and biological processes. These processes include sorption-desorption, volatilization, and chemical and biological transformation. Solubility, vapor pressure, and the partition coefficient of a compound determine its concentration and residence time in water and hence the subsequent processes in that phase. The movement of an organic compound is largely dependent upon the physico-chemical interactions with other components of the aquatic environment. Such components include suspended solids, sediments, and biota. 

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