Fathead minnow (Pimephales promelas) reproduction is impaired when exposed to a naphthenic acid extract.

Previous studies have demonstrated that oil sands process-affected water (OSPW) impairs the reproduction of fish and that naphthenic acids (NAs), a natural constituent of oil sands, are suspected of being responsible. This study evaluates the potential impact of NAs on the reproduction of adult fathead minnows (Pimephales promelas) under laboratory conditions. Fathead minnows exposed to a 10 mg/l naphthenic acid extract (NAE) for 21 days spawned fewer eggs and males had reduced expression of secondary sexual characteristics. Male fathead minnows exposed to a 5 mg/l NAE had lower plasma levels of 11-ketotestosterone whereas those exposed to a 10 mg/l NAE had lower concentrations of both testosterone and 11-ketotestosterone. Since OSPW also contains high concentrations of salts, this study also investigated whether they modify the toxicity of NAEs. Spawning was significantly reduced in fathead minnows exposed to a 10 mg/l NAE alone and in combination with NaHCO3 (700 mg/l), typical of concentrations in OSPW(.) Interestingly, the addition of NaHCO3 reduced the inhibitory effects of the NAE on the numbers of reproductive tubercles and plasma testosterone levels. Further studies showed that NaHCO3 acted by reducing the uptake of the NAE to the fish. NaHCO3 but not NaCl or Na2SO4 reduced the acute toxic effects of the NAE on fathead minnow embryo and larvae mortality. Collectively, these studies show that the NAs in OSPW have the potential to negatively affect reproduction in fathead minnows and that HCO3⁻ reduces the acute and chronic toxicity of NAs.

Use of a (quantitative) structure-activity relationship [(Q)SAR] model to predict the toxicity of naphthenic acids.

Naphthenic acids (NA) are a complex mixture of carboxylic acids that are natural constituents of oil sand found in north-eastern Alberta, Canada. NA are released and concentrated in the alkaline water used in the extraction of bitumen from oil sand sediment. NA have been identified as the principal toxic components of oil sands process-affected water (OSPW), and microbial degradation of lower molecular weight (MW) NA decreases the toxicity of NA mixtures in OSPW. Analysis by proton nuclear magnetic resonance spectroscopy indicated that larger, more cyclic NA contain greater carboxylic acid content, thereby decreasing their hydrophobicity and acute toxicity in comparison to lower MW NA. The relationship between the acute toxicity of NA and hydrophobicity suggests that narcosis is the probable mode of acute toxic action. The applicability of a (quantitative) structure-activity relationship [(Q)SAR] model to accurately predict the toxicity of NA-like surrogates was investigated. The U.S. Environmental Protection Agency (EPA) ECOSAR model predicted the toxicity of NA-like surrogates with acceptable accuracy in comparison to observed toxicity values from Vibrio fischeri and Daphnia magna assays, indicating that the model has potential to serve as a prioritization tool for identifying NA structures likely to produce an increased toxicity. Investigating NA of equal MW, the ECOSAR model predicted increased toxic potency for NA containing fewer carbon rings. Furthermore, NA structures with a linear grouping of carbon rings had a greater predicted toxic potency than structures containing carbon rings in a clustered grouping.

Detecting oil sands process-affected waters in the Alberta oil sands region using synchronous fluorescence spectroscopy.

Large volumes of oil sands process-affected waters (OSPW) are produced during the extraction of bitumen from oil sand. There are approximately 10(9) m(3) of OSPW currently being stored in settling basins on oil sands mining sites in Northern Alberta. Developers plan to create artificial lakes with OSPW and it is expected that this water may eventually enter the environment. This study was conducted in order to determine if synchronous fluorescence spectroscopy (SFS) could detect OSPW contamination in water systems. Water samples collected from ponds containing OSPW and selected sites in the Alberta oil sands region were evaluated using SFS with an offset value of 18 nm. OSPW ponds consistently displayed a minor peak at 282.5 nm and a broad major peak ranging between 320 and 340 nm. Water from reference sites within the oil sands region had little fluorescence at 282.5 nm but greater fluorescence beyond 345 nm. Naphthenic acids are the major toxic component of OSPW. Both a commercial naphthenic acid and a naphthenic acid extract prepared from OSPW had similar fluorescent spectra with peaks at 280 nm and 320 nm and minor shoulders at approximately 303 and 331 nm. The presence of aromatic acids closely associated with the naphthenic acids may be responsible for unique fluorescence at 320-340 nm. SFS is proposed to be a simple and fast method to monitor the release of OSPW into ground and surface waters in the oil sands region.

Effect of carboxylic acid content on the acute toxicity of oil sands naphthenic acids.

Fractions of methylated naphthenic acids (NAs) isolated from oil sands process-affected waterwere collected utilizing Kugelrohr distillation and analyzed by proton nuclear magnetic resonance (1H NMR) spectroscopy. 1H NMR analysis revealed that the ratio of methyl ester hydrogen atoms to remaining aliphatic hydrogen atoms increased from 0.130 to 0.214, from the lowest to the greatest molecular weight (MW) fractions, respectively, indicating that the carboxylic acid content increased with greater MW. Acute toxicity assays with exposure to monocarboxyl NA-like surrogates demonstrated that toxicity increased with increasing MW (D. magna LC50 values of 10 +/- 1.3 mM and 0.59 +/- 0.20 mM for the respective lowest and highest MW NA-like surrogates); however, with the addition of a second carboxylic acid moiety, the toxicity was significantly reduced (D. magna LC50 values of 10 +/- 1.3 mM and 27 +/- 2.2 mM forthe respective monocarboxyl and dicarboxyl NA-like surrogates of similar MW). Increased carboxylic acid content within NA structures of higher MW decreases hydrophobicity and, consequently, offers a plausible explanation as to why lower MW NAs in oil sands process-affected water are more toxic than the greater MW NAs.

Cadmium accumulation in zebrafish (Danio rerio) eggs is modulated by dissolved organic matter (DOM).

Experiments were conducted to investigate factors influencing the accumulation of cadmium (Cd(2+)) into zebrafish (Danio rerio) eggs. The accumulation of (109)Cd was affected by: (1) concentration, (2) time, (3) presence of dissolved organic material (DOM), (4) different origin of DOM and (5) different parts of fish eggs. Over a 5-h exposure, zebrafish eggs showed a steady increase in Cd-accumulation. DOM-concentrations over 15ppm carbon (C) decreased Cd-uptake significantly. Both samples of DOM, brown water marsh (LM) and a eutrophic pond (SP), at 16.9ppmC, reduced the Cd-accumulation in the chorion, perivitelline liquid and the embryo. Cd was mainly accumulated in the egg's outer shell chorion (61%) and only small amounts passed through the chorion into the perivitelline liquid (38%) and embryo (1%). In the presence of LM-DOM, the accumulation of Cd into the egg components was decreased by 43% (chorion), 52% (perivitelline liquid) and 52% (embryo), respectively, compared with the control group. Similarly, the presence of SP-DOM reduced the Cd-accumulation by 29% (chorion), 61% (perivitelline liquid) and 60% (embryo), respectively, compared with the controls. DOM-concentration should be taken into consideration when determining ecotoxicological effects of Cd on fish populations.

Diethylaminoethyl-cellulose clean-up of a large volume naphthenic acid extract.

The Athabasca oil sands of Alberta, Canada contain an estimated 174 billion barrels of bitumen. During oil sands refining processes, an extraction tailings mixture is produced that has been reported as toxic to aquatic organisms and is therefore collected in settling ponds on site. Investigation into the toxicity of these tailings pond waters has identified naphthenic acids (NAs) and their sodium salts as the major toxic components, and a multi-year study has been initiated to identify the principal toxic components within NA mixtures. Future toxicity studies require a large volume of a NA mixture, however, a well-defined bulk extraction technique is not available. This study investigated the use of a weak anion exchanger, diethylaminoethyl-cellulose (DEAE-cellulose), to remove humic-like material present after collecting the organic acid fraction of oil sands tailings pond water. The NA extraction and clean-up procedure proved to be a fast and efficient method to process large volumes of tailings pond water, providing an extraction efficiency of 41.2%. The resulting concentrated NA solution had a composition that differed somewhat from oil sands fresh tailings, with a reduction in the abundance of lower molecular weight NAs being the most significant difference. This reduction was mainly due to the initial acidification of tailings pond water. The DEAE-cellulose treatment had only a minor effect on the NA concentration, no noticeable effect on the NA fingerprint, and no significant effect on the mixture toxicity towards Vibrio fischeri.

Estrogenic activity of dicofol with the human estrogen receptor: Isomer- and enantiomer-specific implications.

Dicofol is a non-systemic acaricide/miticide currently registered in the US and Canada for use on a wide variety of crops. This agrochemical has been identified as a potential candidate substance for the United Nations Economic Commission for Europe (UN-ECE) Persistent Organic Pollutant (POP) Protocol and implicated as a potential "endocrine disrupting compound". The technical product is usually synthesized from technical DDT and consists of approximately 80% and 20% of p,p'- and o,p'-dicofol isomers. The o,p'-substituted isomer of dicofol is chiral and may have enantiomer-specific activity; however, the stereospecific activity of o,p'-dicofol has not been reported. In this study, we examined the isomer- and enantiomer-specific endocrine disruption potential of dicofol using yeast-based steroid hormone receptor gene transcription assay designed with the human estrogen receptor (hER). Estrogenic activity of (+)-17-beta estradiol (positive control), p,p'-dicofol, racemic o,p'-dicofol [(+/-)-o,p'-dicofol] and the individual o,p'-dicofol enantiomers was measured via quantification of beta-galactosidase. The (+/-)-o,p'- and p,p'-dicofol were weak estrogen mimics (EC(50): 4.2 x 10(-6) and 1.6 x 10(-6)M, respectively) relative to estradiol (3.7 x 10(-10)M). For o,p'-dicofol, the beta-galactosidase induction by (-)-o,p'-dicofol (EC(50): 5.1 x 10(-7)M) was greater than the racemic mixture. However, the (+)-o,p'-dicofol enantiomer was found to have negligible estrogenic activity. These data indicate that dicofol is a weak hER agonist due to activity of the achiral p,p'-isomer and (-)-o,p'-substituted enantiomer and emphasizes the influence of chemical structure and configuration on biological responses to exposure from chiral compounds.

Photogeneration of singlet oxygen by humic substances: comparison of humic substances of aquatic and terrestrial origin.

The singlet oxygen (1(O2)) luminescence of 27 isolated humic substances (HS), natural organic matter, ultrafiltrates, and the synthetic fulvic acid HS1500 has been investigated by time-resolved spectroscopy in buffered D(2)O. The samples include both reverse osmosis isolates from lakes in Scandinavia, Canada, and Germany, and IHSS fulvic and humic acids of aquatic and terrestrial origin. The quantum yields of 1(O2) formation (PhiDelta) obtained on laser excitation at 480 nm ranged between 0.06 (HS1500) and 2.7%(fulvic acid from soil, IHSS). In our study, a general trend towards higher PhiDelta in terrestrial HS was observed. The comparison of reverse osmosis isolates from surface waters collected during fall 1999 and spring 2000 from five Scandinavian sites yielded, in all cases, higher PhiDelta for the spring samples. For the aquatic sampling sites Hietajarvi and Birkenes, PhiDelta even exceeded values of 0.6%, which were found to be typical for terrestrial or soil water material. Investigation of the excitation wavelength dependence of PhiDelta in the spectral range 355-550 nm yielded different spectral shapes for aquatic HS and "non-aquatic" HS, respectively. On the basis of these excitation spectra, 1(O2) production rates were calculated for eight representative HS.

A toxicity identification evaluation approach to studying estrogenic substances in hog manure and agricultural runoff.

Spreading liquid manure on agricultural fields is a routine way of disposing of animal manure and optimizing the use of nutrients for crops. Limited studies suggest that these wastes may contain a variety of endocrine-disrupting compounds (EDCs) that may be released into aquatic environments through runoff. The purpose of this study was to apply a toxicity identification and evaluation approach to isolate and identify estrogenic compounds in hog manure. A recombinant yeast estrogen screen bioassay was used to detect estrogenicity of high-performance liquid chromatography--separated hog manure fractions. Further analytical analyses of the fractions and comparison to authentic standards resulted in the identification of the endogenous estrogens 17 beta-estradiol (E2) and estrone, and the phytoestrogen metabolite, equol. High levels of equol (6.9-16.6 ppm) were found to be present in manure that was stored for several months. The endocrine-disrupting potential of equol was characterized further by using fish hormone estrogen receptor (ER), sex hormone binding protein (SSBP), and goldfish androgen receptor (AR) radioligand binding assays. Equol was found to be approximately 1,000- and 200-fold less potent that E2 in competing for binding sites of the SSBP and ER, respectively. Equol's potency was 2,200-fold less than testosterone for the AR. Additional studies confirmed the presence of compounds with estrogenic activity in tile drain water after application of hog manure to an agriculture field. In this case, the contribution of equol to the total estrogenicity of the tile drain water was minimal relative to that of natural estrogens. Overall, this study indicates that further work is warranted to assess the impact that EDCs that originate from agricultural runoff may have on the ecology or physiology of exposed biota.