ISSN:0730-7268    

DOI:10.1002/etc.5620090201

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe toxicokinetics and bioavailabilities of 2‐methylnaphthalene (2‐MN), fluorene and pyrene were studied in rainbow trout (Salmo gairdners) implanted with an indwelling cannula in the dorsal aorta. After intraarterial injection of one of the polycyclic aromatic hydrocarbons (PAHs) (10 mg/kg) to trout, chemical concentration in the blood was found to decline triphasically with time. The terminal half‐lives of elimination from the blood for 2‐MN, fluorene and pyrene were 9.6, 10.5 and 12.8 h, respectively. The toxicokinetics of the PAHs in trout were best described by a three‐compartment open model with the central compartment and the deep peripheral compartment representing the blood and fatty tissues of trout, respectively. The PAHs were metabolized by trout mainly to water‐soluble metabolites which were excreted into the urine and bile. When trout were exposed to water containing 2‐MN, fluorene or pyrene (0.5 mg/L), the chemical was detected almost immediately in the blood. The apparent bioavailabilities of 2‐MN, fluorene and pyrene in trout were 20, 36 and 35%, respectively. In contrast, little or no unchanged chemical was detected in the blood of trout following intragastric administration of 2‐MN, fluorene or pyrene (50 mg/kg). These results indicate that the PAHs are absorbed systemically by trout via the branchial route at rates much faster than that

ISSN:0730-7268    

DOI:10.1002/etc.5620090202

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe accumulation of contaminants by free‐living organisms has traditionally been determined with permutations of the deterministic model:Ct=Ce(1 – e−kt). However, studies utilizing a variety of species and exposure scenarios now suggest that significant deviations may occur from this classic form. In many cases noted to date, these deviations have involved a sigmoidal pattern of accumulation. While there may be no one single causal mechanism responsible for the expression of such a pattern in all cases studied, the application of a flexibly shaped Richards sigmoidal model can improve goodness of fit to the data relative to the classic model form. Several examples are presented for use of the Richards model: accumulation of137Cs by free‐living American coots (Fulica americana) and yellow‐bellied turtles (Pseudemys scripta), and Hg accumulation by mosquitofish (Gambusia

ISSN:0730-7268    

DOI:10.1002/etc.5620090203

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractWaterborne xenobiotics enter fish and other aquatic species primarily by transfer across the gill epithelium. Potential barriers to uptake include water flow across the gill, diffusion across the gill epithelium and the overlying aqueous stagnant layer and blood flow through the gill (cardiac output). In general, for any particular chemical, only one of the barriers is operative with the resistance offered by the others being negligible. The rate‐limiting barrier is determined by the physico‐ and biochemical properties of the substance: molecular size, lipophilicity, binding to blood proteins and formed elements. The resistance of each barrier is affected differently by variables such as temperature, molecular size, lipophilicity and body size of the animal. When the resistance offered by the gill barriers is low, uptake may be controlled by transfer to storage tissues, e.g., by blood flow to adipose tis

ISSN:0730-7268    

DOI:10.1002/etc.5620090204

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA mathematical model for the exchange of organic chemicals by fish gills was formulated based solely on the limitations imposed by the flows of water and blood into the gills. For large rainbow trout, this model was found to closely follow the magnitude and trends of observed gill uptake rates over a range of octanol/water partition coefficient from 1 to 106. Observations averaged only about 30% less than model predictions. This modest lack‐of‐fit is presumably due to the effects of diffusional barriers and ionization which would further limit uptake, although uncertainties in model parameters and data are likely also partly responsible. This analysis suggests that these basic physiological parameters are of major importance in the regulation of exchange at fish gills and should be accounted for in more detailed toxicokinetic models. Also, this simple model could by itself be useful for approximate assessments of accumulation of organic chemicals by f

ISSN:0730-7268    

DOI:10.1002/etc.5620090205

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe accumulation kinetics of two waterborne polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene (BAP) and phenanthrene (PHE), were studied in the mayfly nymph (Hexagenia limbata).The uptake clearance decreased while the bioconcentration of BAP increased with an increase in weight of theH. limbatanymph. The relationship between uptake clearance and bioconcentration for PHE was variable, and bioconcentration was greater for the heavier animals.Two kinetic models were used to evaluate the effect of nymph weight on disposition of PAHs: (a) the amount‐uptake clearance model, similar to models most frequently used in environmental toxicology; and (b) a clearance‐volume model, similar to models used in clinical pharmacology. The two models gave similar predictive results but were different in a few cases. These differences in common parameter estimation probably resulted from methodologies used and high data variability rather than the models themselves, since they are mathematically equal. Some of the parameters are unique to each of the models and are defined and described.The clearance of oxygen from water is inversely and linearly related to the weight of the mayfly nymphs, but oxygen clearances were always much less than the uptake clearances of the PAHs. The high PAH uptake clearance compared to oxygen clearance implies a greater surface area or efficiency for PAH accumulation from wa

ISSN:0730-7268    

DOI:10.1002/etc.5620090206

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractIn spite of their hydrophobicity, not all polychlorinated dibenzo‐p‐dioxin (PCDD) and dibenzofuran (PCDF) congeners accumulate significantly in fish or other aquatic organisms. This is found both in laboratory experiments and in organisms that are sampled in the natural environment. Hitherto, this congener‐specific accumulation could not adequately be explained or predicted.Many PCDDs and PCDFs with four or more chlorine atoms, such as octachlorodibenzo‐p‐dioxin, are taken up very slowly, if at all, during aqueous exposure. Furthermore, the uptake rates after dietary exposure of these congeners are significantly less than those of other chlorinated aromatic hydrocarbons with comparable hydrophobicity, such as polychlorinated benzenes and biphenyls. A lack or a low rate of membrane permeation may help to explain this phenomenon.For several higher chlorinated congeners and for most of the lower chlorinated dioxins and furans, the rates of uptake after dietary and aqueous exposure are comparable to those of other hydrophobic aromatic hydrocarbons. The relatively low bioconcentration and biomagnification factors of these lower chlorinated PCDDs and PCDFs should thus be explained by high rates of excretion, probably by biotransformation. In several studies, polar metabolites have been identified. Furthermore, in fish in which the cytochrome P‐450 system was inhibited with piperonylbutoxide, the bioconcentration factor of 2,8‐dichlorodibenzo‐p‐dioxin was significantly higher than that in fish which were not pretreated with the blocking agent. These results support the hypothesis that biotransformation is of paramount importance for the bioaccumulation of severa

ISSN:0730-7268    

DOI:10.1002/etc.5620090207

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe fate of 14 polycyclic aromatic hydrocarbon (PAH) compounds was evaluated with regard to interphase transfer potential and mechanisms of treatment in soil under unsaturated conditions. Volatilization and abiotic and biotic fate of the PAHs were determined using two soils not previously exposed to these compounds. Volatilization accounted for approximately 30 and 20% loss of naphthalene and 1‐methylnaphthalene, respectively; for the remaining compounds, volatilization was negligible. Abiotic reactions accounted for approximately 2 to 20% of the reduction in concentration in solvent extracts for two‐ and three‐ring PAH compounds; no statistically significant reduction was observed for PAH compounds containing greater than three aromatic rings. Biotic mechanisms were quantified as first‐order rate constants corrected for volatilization and abiotic mechanisms. Half‐life values increased from approximately 2 to 60 to more than 300 d for two‐, three‐ and four‐ and five‐ring PAH compounds, respectively. In general, biological degradation rates were not significantly different between the two soils. Information concerning interphase transfer potential and mechanisms of treatment provides the basis for a rational approach to remediation of soil contaminated w

ISSN:0730-7268    

DOI:10.1002/etc.5620090208

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA laboratory sediment–water microcosm experiment for a Rocky Mountain subalpine lake was conducted over a 35‐d incubation period. Three sets of treatments were acidified to a pH of 4.3 and compared with a set of control microcosms. Treatments included additions of nitric acid, sulfuric acid and both acids combined. All treatment microcosms demonstrated rapid pH recovery to near that of the controls (e.g., 6.2) and changes in ion concentration suggested that over 90% of this recovery could be accounted for by cation exchange and microbial reduction of sulfates and nitrates. Denitrification appeared to predominate in both sets of treatments that involved nitric acid while cation exchange (mostly calcium) was more important in the sulfuric acid treatment. These results are consistent with published findings for both laboratory and field studies and demonstrate the potential importance of sediments for acid neutralization in a Rocky Mountain l

ISSN:0730-7268    

DOI:10.1002/etc.5620090209

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe 5‐methyl deoxycytidine (m5‐dCyd) content of DNA from bluegill sunfish chronically exposed to benzo[a]pyrene at a concentration of 1 μg/L in their water for a period of 40 d was quantified by cation exchange chromatography. Hypomethylation, as measured by the loss of m5‐dCyd from the DNA, occurred shortly after benzo[a]pyrene (BaP) exposure and continued even upon termination of exposure conditions. The onset and persistence of hypomethylation was found to be correlated with other types of DNA‐damaging events such as strand breaks and DNA adduct formation. These observations suggest that changes in DNA integrity, including hypomethylation, are indicative of a biological response to genotoxi

ISSN:0730-7268    

DOI:10.1002/etc.5620090210

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY