Petroleum hydrocarbons depuration

Nunes, P., Benville, P.E., Jr. (1979) Uptake and depuration of petroleum hydrocarbons in the Manila clams, Tapes semidecussata Reeve. Bull. Environ. Contam. Toxicol. 21, 719-724. 

Rice, S., R.E. Thomas and J.W. Short. Effects of petroleum hydrocarbons on breathing and coughing rates and hydrocarbon uptake-depuration in pink salmon fry. In Physiological Responses of Marine Biota to Pollutants, edited by F. Vernberg, A. Calabrese, F. Thurberg and W. Vemberg, New York, Academic Press, pp. 259-278, 1977. 

The bioaccumulation of a xenobiotic usually involves an initial high linear rate of uptake, followed by the eventual reaching of a maximal tissue equilibrium concentration (Burns and Smith 1981 Hawker and Connell 1986). In some cases clearly biphasic or multiphasic uptake have been observed, e.g. petroleum hydrocarbons (Stegeman and Teal 1973) and picric and picramic acids (Burton et al. 1984) taken up by C. virginica, which, as for depuration processes (see below), can be interpreted in terms of equilibration of the xenobiotic into multiple compartments within the organism. In other cases tissue equilibrium concentrations have not been reached after long periods of exposure, e.g. various bivalves exposed to hydrocarbons for up to 6 months (Clement et al. 1980 Widdows et al. 1982). The initial rate of uptake and equilibrium biotic concentration depends on the xenobiotic exposure concentration (Burns and Smith 1981 Hawker and Connell 1986). 

Typical of many organic pollutants, petroleum hydrocarbons are sorbed rapidly by aquatic invertebrates until a steady state or equilibrium in concentrations is achieved. The rate of uptake depends primarily on the exposure concentration, but temperature and other environmental factors may alter the metabolic rate of the animal and hence rate of uptake. Most petroleum hydrocarbons are lipophilic and thus the maximum level achieved during the steady-state phase depends on the body lipid content, as well as exposure concentration (Figure 7.7). Depuration from tissues is generally rapid but once again depends on temperature. Bums and Smith (1981), working in relatively warm Australian waters, found that 90% of hydrocarbons in the mussel Mytilus was eliminated within 3 weeks. By contrast, the same species required 14 weeks for 90% clearance of fuel oil under European winter conditions (Blackman and Law, 1980). 

Fish absorb hydrocarbons primarily from the water, although ingestion of tainted food also leads to tissue contamination. Rate of uptake depends directly upon exposure concentration and lipid content of the fish. Apparently, the various components of petroleum hydrocarbons are sorbed at different rates and are also selectively deposited in specific tissues. For example. Whittle etaL (1977) treated juvenile herring with " C-hexadecane and C-benzo[a]pyrene to determine the sites of deposition of these compounds. It was then shown that 59% of the hexadecane was found in the muscle, whereas 8% and 3% occurred in the mesenteric fat and stomach fat, respectively. By contrast, the corresponding values for benzo[a]pyrene were 0.1, 0.02, and 87.1%, respectively. In most cases, the rate of depuration is rapid but once again depends on the chemical composition of the oil, lipid content of the fish, and environmental factors such as temperature. Although the maximum half-life of /2-alkanes in kerosene-tainted mullet was 18 days, the concentration of naphthalenes in gulf killifish exposed to No. 2 fuel oil declined to nondetectable levels within 15 days (Connell and Miller, 1981). 

The intent of this study was to derive rate constants describing uptake and depuration of some forest pesticides using fish (rainbow trout, Salmo gairdneri) and an aquatic macrophyte (duckweed, Lemna minor) in laboratory tests. Since some formulations of forest pesticides also contain solvents of petroleum distillates, experiments were also carried out with a hydrocarbon, fluorene, which is a component of fuel oil (16). 

---