摘要:

AbstractThis study describes the formation of slowly reversible sorbed fractions of various halogenated alkanes and alkenes in two surface soils. After the initial sorption equilibration period, the compounds were desorbed by one of two methods. The first used repetitive batch extraction with water. After 16 extractions of 24 to 72 h each, concentrations in the aqueous phase reached low values and a slow desorbing, residual fraction remained in the soil. The residual fraction in the soil was determined independently after extraction with hot acetone, whose efficacy was demonstrated. During desorption, apparent soil‐water distribution coefficients increased progressively to as much as 200 times greater than equilibrium sorption coefficients,Kd, obtained separately from sorption isotherms. With increasing sorption equilibration time, the residual became greater in magnitude and less mobile. The second desorption method simulated desorption to infinite dilution over a 96 h period by using Tenax GC polymeric adsorbent beads included in the suspension as a sink for desorbed chemical. Control experiments proved the usefulness of Tenax and showed that desorption from the soil was rate limiting. All compounds studied formed slowly reversible fractions in the soils. This fraction amounted to several percent of the total sorbed from solution. The results indicate that formation of slowly reversible fractions is probably typical of nonpolar organic compounds, including those with weak sorbing tendencie

ISSN:0730-7268    

DOI:10.1002/etc.5620090901

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe mechanism of formation and release of highly immobilized residues of some small nonpolar halogenated hydrocarbons in two surface soils, a stream sediment and an aquifer sediment was investigated. The labile sorbed fractions of compound were removed from treated soils by purging to infinite dilution in aqueous suspensions for 96 h. The remaining slowly reversible (residual) fraction of compound in the soil was quantitated as a function of prepurge sorption conditions. The residual increased nonlinearly with sorption equilibration time and applied concentration. Residuals in whole soils and whole soils pretreated with H2O2were correlated with soil organic carbon. Among wet‐sieved particle size fractions, however, the organic carbon‐based concentrations followed the order, sand>silt>>clay. Also, some residual was associated with undecomposed plant matter. Release of the residual into water was greatly increased by pulverization of the soil and by acidification of the soil suspension. The results indicate that the slow release of the residual fraction is caused by molecular diffusion from remote sites in the soil organic matter matrix. Mineral surface and clay interlayer adsorption were ruled out by the finding of low residuals in the clay‐sized particles. However, the mineral fraction plays an important role by shielding some of the organic matter in interstitial pores of particle aggregates from equilibrium with bulk sol

ISSN:0730-7268    

DOI:10.1002/etc.5620090902

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractAbout 25 to 30% of all United States (U.S.) publicly owned treatment works (POTW) discharges enter estuaries and coastal waters. An expert system has been developed to model the fate and transport of chemicals discharged from POTWs into estuaries. Each POTW has been classified as one of four groups: primary, trickling filter, lagoon and activated sludge in terms of treatment level. The system is designed to calculate concentrations under 7‐d 10‐year low flow, summer low flow and annual mean flow conditions. To account for varying mixing characteristics and salinity distributions observed in a given estuary, the system includes one‐dimensional and two‐dimensional (longitudinal and vertical) mass transport algorithms. To date, the modeling framework has been applied to nine estuaries. For validation purposes, biochemical oxygen demand (BOD) concentrations are also predicted based on industrial as well as municipal organic carbon loads. In several estuaries, predicted in‐stream BOD levels have been compared to measured BOD data resulting in successful model validation. The validated models are then used to predict linear alkylbenzene sulfonate (LAS) concentrations in estuaries. These LAS concentrations are found to be less than 20 μg/L in these estuaries under the three flow

ISSN:0730-7268    

DOI:10.1002/etc.5620090903

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe fertilized eggs, embryos and larvae of the California mussel (Mytilus californianus) were used to develop methods for assessing fertilization and larval development rates, and for conducting toxicity tests in standard exposure chambers and small volume (3 ml) chambers. Because the sperm/egg ratio resulting in high monospermic fertilization rates varied among females, the “optimal” ratio for each female was predetermined in an aliquot of eggs prior to fertilizing the entire batch for bioassay use. The fluorescent DNA probe Hoechst 33342 was used to rapidly differentiate unfertilized, monospermic and polyspermic eggs. Following fertilization of entire batches of eggs based on the predetermined sperm/egg ratio, monospermic fertilization rates of>90% were readily achieved. Fertilized embryos were then used in bioassays conducted in beakers or tissue‐culture chamber slides (mini chambers), which could be viewed directly on the microscope. The response of the embryos and larvae to the metabolic inhibitor sodium azide was assessed in both types of test chambers. At 96 h postinsemination at 12°C, veliger or nonveliger larvae were assessed using polarization microscopy to determine the presence or absence of a complete shell. No significant difference in the response to sodium azide was detected between the beakers and mini chambers. This study demonstrates thatM. californianusis suitable for static embryo/larval toxicity tests, and that small volume chambers allow successful larval development and eliminate the need for subsampling of larger test chambers. We also demonstrated the value of assessing fertilization rates prior to conducting the bioassay, and present an improved method for examining larval shell development using polarization micr

ISSN:0730-7268    

DOI:10.1002/etc.5620090904

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractSediment reworking rate, mortality and organism dry weight were measured forStylodrilus heringianusin laboratory microcosms. The experiments were designed to identify potential population‐specific response differences to mixed (stirred to obtain a more uniform particle size distribution over depth) and unmixed (passively settled) microcosm sediments. Lake Michigan sediments and worms were collected offshore Benton Harbor, Michigan and Grand Haven, Michigan.The mixed Benton Harbor sediments were toxic toS. heringianuscollected from Grand Haven, whereas there were no significant differences in measured responses between mixed and unmixed sediment microcosms for Grand Haven‐collected worms exposed to Grand Haven sediments or Benton Harbor‐collected worms exposed to Benton Harbor sediments. Note that the mixing of sediments resulted in increased availability of contaminants sorbed to the fine sediment fraction.Because contaminant and oligochaete population density data suggest that Grand Haven sediments are less contaminated, the population‐specific response suggests thatS. heringianusmay adapt to the low level long‐term stressful conditions (chemical or otherwise). Results also suggest caution and consideration of the history of test organisms in the design and interpretation of toxic

ISSN:0730-7268    

DOI:10.1002/etc.5620090905

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractAdult, male mallards (Anas platyrhynchos) were given a choice between a control diet and a diet containing 5, 10 or 20 ppm selenium as selenomethionine dissolved in water and mixed into the diet. At 10 and 20 ppm, selenium‐treated diets were avoided. Avoidance appeared to be caused by a conditioned response, probably to illness caused by the selenium and not to an aversion to the taste of the seleniu

ISSN:0730-7268    

DOI:10.1002/etc.5620090906

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractEmbryos of the Japanese medaka were individually exposed to varying concentrations of [3H]2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) in a static, nonrenewal system. The EC50 with 95% confidence interval (C.I.) to prevent hatching was 14 (11–17) nanograms (ng) of TCDD equivalents per liter (L) of water (parts per trillion). The LC50 with 95% C.I. for survival to 3 d posthatch was 9 (6–12) ng TCDD equivalents/L. The EC50 with 95% C.I. for embryos with minor lesions and severe, life‐threatening lesions were 3.5 (1.3–5.7) ng TCDD equivalents/L and 14 (12.4–15.6) ng TCDD equivalents/L, respectively. In a separate experiment that was terminated prior to the embryos hatching or dying, the EC50 for lesions was calculated to be 2.2 (1.4–3.0) ng TCDD equivalents/L. Based on the amount of TCDD equivalents recovered from dechorionated embryos, the ED50 with 95% C.I. for lesions was calculated to be 0.24 picograms of TCDD equivalents per milligram of dechorionated embryo weight (parts per billion). When the embryos were exposed to [3H]TCDD within 1 to 2 h after fertilization, no concentration dependent increase in visible lesions was observed until after the formation of the liver rudiment (day 4 of development). By exposing Japanese medaka embryos to lethal concentrations of TCDD beginning on different days of embryonic development, it was demonstrated that the sensitive period for toxicity was during liver formation on day 4 or 5 of development. The sensitive period for development was not caused by differences in TCDD absorption across the chorion. When embryos were exposed to [3H]TCDD prior to, during or after liver formation, there was no statistical difference in the dose of TCDD equivalents that crossed the chorion and entered th

ISSN:0730-7268    

DOI:10.1002/etc.5620090907

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractElevated concentrations of selenium (Se) have been previously measured in biota sampled from the Kesterson National Wildlife Refuge (KNWR) in the San Joaquin Valley of central California. We conducted acute and chronic toxicity tests with the cladoceranDaphnia magnaand the midgeChironomus ripariusto determine the toxicity or bioaccumulation of waterborne Se in a reconstituted water similar to the San Joaquin River. Daphnids were more acutely sensitive than midges to the toxic effects of inorganic Se. An organic form of Se (seleno‐[L]‐methionine) was extremely toxic to daphnids, but was relatively nontoxic to midges. In long‐term exposure to a 6:1 mixture of selenate to selenite (a mixture representative of KNWR), the emergence time of adult midges was delayed at Se concentrations ≥ 837 μg/L. Daphnid reproduction and intrinsic rate of natural increase (r) were reduced at Se concentrations ≥ 348 μg/L and growth of adults was reduced at ≥ 156 μg/L. Whole body Mg, K and Na concentrations in daphnids were not affected by chronic Se exposure; however, whole body Ca concentration increased at intermediate Se exposure concentrations. In addition, whole body Cl concentration was reduced at 711 μg Se/L. Daphnids accumulated potentially toxic concentrations of Se from water that may adversely affect fish or waterfowl through

ISSN:0730-7268    

DOI:10.1002/etc.5620090908

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA poikilothermic metabolic activation system developed from liver homogenate of rainbow trout (Oncorhynchus mykiss, formerlySalmo gairdneri) was used in the AmesSalmonella/Mammalian Microsome Mutagenicity Test. Postmitochondrial fractions (S9) mediated four model promutagens – 2‐aminoanthracene (2AA), 2‐aminofluorene (2AF), benzo[a]pyrene (BaP) and 3‐methylcholanthrene (3MC)–that require two different exogenous metabolic activation routes to form mutagens withSalmonellaTA98 and TA100. The enzymatic activity of trout S9 was cytochrome P‐450‐like; it was heat labile and oxygen‐ and cofactor‐dependent. Preincubation temperature significantly influenced the sensitivity of the fish‐activated Ames test. Bacterial mutagenesis with trout activation significantly decreased as preincubation temperature increased; the optimum S9 activation temperature range for trout was 10 to 15°C compared with 37°C for the rat. The liquid‐preincubation test was best adapted to the trout poikilothermic activation system; it was significantly more sensitive than the plate‐incorporation test in detecting histidine revertants. The S9 activity of trout and rat was qualitatively similar in the Ames test: that is, both fractions metabolically activated 2AA, 2AF, BaP and 3MC to produce bacterial mutagenesis withSalmonellaTA98 and TA100. The use of this ecologically relevant exogenous activation system in the short‐term predictive genotoxicity testing of freshwater ecosystems is helpful in the assessment of potential hazards of chemical contam

ISSN:0730-7268    

DOI:10.1002/etc.5620090909

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe relative sensitivity, analytical precision, discriminatory power and concordance among endpoints and with sediment chemistry were compared among five sediment toxicity tests. The tests were performed with aliquots of 15 composited, homogenized sediment samples. Survival and a variety of sublethal endpoints were determined in tests performed with the amphipodsRhepoxynius abroniusandAmpelisca abdita, embryos of the musselMytilus edulis, embryos of the urchinStrongylocentrotus purpuratus, and the polychaeteDinophilus gyrociliatus.Each sample was also tested for trace metal and organic compound concentrations, organic carbon content and texture. Two of the five tests (survival amongM. edulisand survival amongR. abronius) were highly sensitive to the samples and had relatively high precision, but the results were correlated most highly with sedimentological variables. One of the tests (survival amongA. abdita) was relatively insensitive, but the results were highly correlated with only the concentrations of toxic chemicals. The test withS. purpuratusindicated mutagenicity in several samples that had high hydrocarbon concentrations. The test of pore water withD. gyrociliatuswas intermediate in sensitivity and precision and not correlated highly with the results from the other tests.

ISSN:0730-7268    

DOI:10.1002/etc.5620090910

出版商:Wiley Periodicals, Inc.    

年代:1990

数据来源: WILEY