Detection of naphthenic acids in fish exposed to commercial naphthenic acids and oil sands process-affected water

Naphthenic acids are a complex mixture of carboxylic acids that occur naturally in petroleum. During the extraction of bitumen from the oil sands in northeastern Alberta, Canada, naphthenic acids are released into the aqueous phase and these acids become the most toxic components in the process-affected water. Although previous studies have exposed fish to naphthenic acids or oil sands process-affected waters, there has been no analytical method to specifically detect naphthenic acids in fish. Here, we describe a qualitative method to specifically detect these acids. In 96-h static renewal tests, rainbow trout (Oncorhynchus mykiss) fingerlings were exposed to three different treatments: (1) fed pellets that contained commercial naphthenic acids (1.5mg g(-1) of food), (2) kept in tap water that contained commercial naphthenic acids (3mg l(-1)) and (3) kept in an oil sands process-affected water that contained 15mg naphthenic acids l(-1). Five-gram samples of fish were homogenized and extracted, then the mixture of free fatty acids and naphthenic acids was isolated from the extract using strong anion exchange chromatography. The mixture was derivatized and analyzed by gas chromatography-mass spectrometry. Reconstructed ion chromatograms (m/z=267) selectively detected naphthenic acids. These acids were present in each fish that was exposed to naphthenic acids, but absent in fish that were not exposed to naphthenic acids. The minimum detectable concentration was about 1microg naphthenic acids g(-1) of fish.     

Comparison of GC-MS and FTIR methods for quantifying naphthenic acids in water samples

The extraction of bitumen from the oil sands in Canada releases toxic naphthenic acids into the process-affected waters. The development of an ideal analytical method for quantifying naphthenic acids (general formula C(n)H(2n+Z)O(2)) has been impeded by the complexity of these mixtures and the challenges of differentiating naphthenic acids from other naturally-occurring organic acids. The oil sands industry standard FTIR method was compared with a newly-developed GC-MS method. Naphthenic acids concentrations were measured in extracts of surface and ground waters from locations within the vicinity of and away from the oil sands deposits and in extracts of process-affected waters. In all but one case, FTIR measurements of naphthenic acids concentrations were greater than those determined by GC-MS. The detection limit of the GC-MS method was 0.01 mg L(-1) compared to 1 mg L(-1) for the FTIR method. The results indicated that the GC-MS method is more selective for naphthenic acids, and that the FTIR method overestimates their concentrations.     

Ozonation of oil sands process water removes naphthenic acids and toxicity

Naphthenic acids are naturally-occurring, aliphatic or alicyclic carboxylic acids found in petroleum. Water used to extract bitumen from the Athabasca oil sands becomes toxic to various organisms due to the presence of naphthenic acids released from the bitumen. Natural biodegradation was expected to be the most cost-effective method for reducing the toxicity of the oil sands process water (OSPW). However, naphthenic acids are poorly biodegraded in the holding ponds located on properties leased by the oil sands companies. In the present study, chemical oxidation using ozone was investigated as an option for mitigation of this toxicity. Ozonation of sediment-free OSPW was conducted using proprietary technology manufactured by Seair Diffusion Systems Inc. Ozonation for 50min generated a non-toxic effluent (based on the Microtox bioassay) and decreased the naphthenic acids concentration by approximately 70%. After 130min of ozonation, the residual naphthenic acids concentration was 2mgl(-1): <5% of the initial concentration in the filtered OSPW. Total organic carbon did not change with 130min of ozonation, whereas chemical oxygen demand decreased by approximately 50% and 5-d biochemical oxygen demand increased from an initial value of 2mgl(-1) to a final value of 15mgl(-1). GC-MS analysis showed that ozonation resulted in an overall decrease in the proportion of high molecular weight naphthenic acids (n> or = 22).     

Toxicity assessment of collected fractions from an extracted naphthenic acid mixture

Recent expansion within the oil sands industry of the Athabasca Basin of Alberta, Canada has led to increased concern regarding process-affected wastewaters produced during bitumen extraction. Naphthenic acids (NAs) have been identified as the primary toxic constituents of oil sands process-affected waters (OSPW) and studies have shown that with time, microbial degradation of lower molecular weight NAs has led to a decrease in observed toxicity. As earlier studies identified the need for an "unequivocal demonstration" of lower molecular weight NAs being the primary contributors to mixture toxicity, a study was initiated to fractionate an extracted NA mixture by molecular weight and to assess each fraction's toxicity. Successful molecular weight fractionation of a methylated NA mixture was achieved using a Kugelrohr distillation apparatus, in which fractions collected at higher boiling points contained NAs with greater total carbon content as well as greater degree of cyclicity. Assays with Vibrio fischeri bioluminescence (via Microtox assay) revealed that the lowest molecular weight NAs collected had higher potency (EC50: 41.9+/-2.8 mg l(-1)) than the highest molecular weight NAs collected (EC50: 64.9+/-7.4 mg l(-1)). Although these results support field observations of microbial degradation of low molecular weight NAs decreasing OSPW toxicity, it is not clear why larger NAs, given their greater hydrophobicity, would be less toxic.     

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.     

Quantification of polychlorinated biphenyls in plastic granulates from the recycling of cables - Reference materials and interlaboratory comparison

A procedure for the quantification of the PCB marker congeners 28, 52, 101, 138, 153, 180 in plastic waste form the recycling of cables in the range of content between 0.1 mgkg(-1) and 20 mgkg(-1) was validated. Representative reference materials for laboratory analyses were produced using granulates from different recycling processes. The method development included aspects of grinding, sieving, homogenising as well as the comparison of extraction methods and chromatographic conditions. The validated procedure foresees grinding of the technical sample to an upper particle size limit of 0.50mm followed by extraction with an unpolar solvent such as n-hexane and gas chromatographic determination. LOD and LOQ for individual congeners ranged between 0.01 mgkg(-1) and 0.08 mgkg(-1). Electron capture detection (ECD) and mass selective detection (MS) were equivalent if chromatographic conditions were appropriately selected. The application of MS was advantageous in presence of significant amounts of interfering components which have been found in some cables. Three reference materials containing the marker congeners in the range of 0.1 mgkg(-1)-5 mgkg(-1) were submitted to a final validation intercomparison with 23 selected field laboratories using the developed method. Relative reproducibility standard deviations varied between 15% and 33%.     

Elemental and spectroscopic characterization of fractions of an acidic extract of oil sands process water

‘Naphthenic acids’ (NAs) in petroleum produced water and oil sands process water (OSPW), have been implicated in toxicological effects. However, many are not well characterized. A method for fractionation of NAs of an OSPW was used herein and a multi-method characterization of the fractions conducted.     

Structure and origin of the natural halogenated monoterpene MHC-1 and its concentrations in marine mammals and fish

The halogenated natural product previously named mixed-halogenated compound 1 (MHC-1) was isolated from the red seaweed Plocamium cartilagineum harvested in Helgoland, Germany. A total of 1.9mg of pure MHC-1 was obtained from 1g air-dried seaweed. The (1)H and (13)C NMR data matched those reported for a natural monoterpene isolated from this species. Thus, the structure of MHC-1 was established to be (1R,2S,4R,5R,1'E)-2-bromo-1-bromomethyl-1,4-dichloro-5-(2'-chloroethenyl)-5-methylcyclohexane. Moreover, the isolated monoterpene proved to be identical with the compound previously detected in marine mammals and fish from different locations. In addition we examined two samples of P. cartilagineum from Ireland and from the Antarctic; however MHC-1 was only present at low levels. Not only the concentrations were lower but also the pattern of polybrominated compounds differed from MHC-1. A calibrated solution of MHC-1 was used to determine correct concentrations from samples where previously only estimates existed relative to the gas chromatography-electron capture detector (GC/ECD) response of trans-chlordane, which underrated the MHC-1 concentrations by more than factor 2. The highest MHC-1 concentration determined to date in marine mammals is 0.14mgkg(-1) blubber. Significantly higher MHC-1 concentrations were determined in farmed fish with up to 2.2mgkg(-1) lipids. The samples with high concentrations of MHC-1 have in common that they were collected in proximity of the natural habitats of P. cartilagineum.     

Naphthenic acid biodegradation by the unicellular alga Dunaliella tertiolecta

Naphthenic acids (NAs) are a major contributor to toxicity in tailings waste generated from bitumen production in the Athabasca Oil Sands region. While investigations have shown that bacteria can biodegrade NAs and reduce tailings toxicity, the potential of algae to biodegrade NAs and the biochemical mechanisms involved remain poorly understood. Here, we discovered that the marine alga Dunaliella tertiolecta is able to tolerate five model NAs (cyclohexanecarboxylic acid, cyclohexaneacetic acid, cyclohexanepropionic acid, cyclohexanebutyric acid and 1,2,3,4-tetrahydro-2-naphthoic acid) at 300 mg L⁻¹, a level which exceeds that of any single or combination of NAs typically found in tailings ponds. Moreover, we show that D. tertiolecta can metabolize four of the model NAs. Analysis of NA-amended cultures of D. tertiolecta via low resolution gas chromatography-mass spectrometry allowed us to quantify decreasing NA levels, identify metabolites, and formulate putative mechanisms of biodegradation. Degradation of cyclohexanebutyric acid and cyclohexanepropionic acid proceeded via β-oxidation and resulted in the transient accumulation of cyclohexaneacetic acid and cyclohexanecarboxylic acid, respectively. Cyclohexanecarboxylic acid was metabolized via 1-cyclohexenecarboxylic acid suggesting that further degradation may occur by step-wise β-oxidation. When D. tertiolecta was inoculated in the presence of oil sands tailings water from the Athabasca region, biodegradation of single-ring NAs was observed relative to controls. This result corroborates the trend we observed with the single-ring model NAs.     

Occurrence of organic contaminants in sewage sludges from eleven wastewater treatment plants, China

This study presents the occurrence of 43 semi-volatile organic compounds (SVOCs) listed as priority pollutants by both China and the United States Environmental Protection Agency, in sewage sludges collected from eleven wastewater treatment plants (WWTPs) of mainland and Hong Kong, China. Thirty-six SVOCs were detected by gas chromatography coupled with mass spectrometer (GC-MS) and at least 14 in each sample. The most abundant compounds were phthalic acid esters (PAEs) and polycyclic aromatic hydrocarbons (PAHs) with total concentrations ranging from 10 to 114mgkg(-1) dry weight (d.w.) (with a mean of 30mgkg(-1) d.w.) and from 1.4 to 33mgkg(-1)d.w. (with a mean of 16mgkg(-1) d.w.), respectively, followed by chlorobenzenes, nitroaromatics, haloethers and halogenated hydrocarbons which occurred generally at concentrations lower than 10mgkg(-1) d.w. Large variations were observed between the concentrations of individual compounds as well as their total concentrations in sludge samples from different WWTPs. The highest values of sum concentration of 16 PAHs and of 6 PAEs were found in sewage sludge from Beijing. The mean total concentration of each class of SVOCs in sewage sludge from mainland was remarkably higher than that from Hong Kong. The concentrations of di(2-ethylhexyl) phthalate in 91% sludge samples met the limit (100mgkg(-1)d.w.) proposed by the Europe Union for land application, whereas the PAH concentrations of 64% sludge samples exceeded the maximum permissible concentration (6.0mgkg(-1)d.w.). The occurrence of SVOCs in this study are compared with other studies and their sources are discussed.     

In vivo endocrine effects of naphthenic acids in fish

Oil pollution from various sources, including exploration, production and transportation, is a growing global concern. The highest toxicity of hydrocarbon pollutants is associated with the water-soluble phase compounds, including naphthenic acids, a known component found in all hydrocarbon deposits. Recently, naphthenic acids (NAs) have shown estrogenic and anti-androgenic effects in vitro. For this reason we investigated the potential effects of two commercial mixtures of naphthenic acids on fish in vivo, using the three-spined stickleback (Gasterosteus aculeatus) as a model species.     

Occurrence of phthalates in sediment and biota: relationship to aquatic factors and the biota-sediment accumulation factor

Phthalate compounds in sediments and fishes were investigated in 17 Taiwan's rivers to determine the relationships between phthalate levels in sediment and aquatic factors, and biota-sediment accumulation factor (BSAF) for phthalates. Mean concentrations (range) of di(2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBzP) and di-n-butyl phthalate (DBP) in sediment at low-flow season were 4.1 (<0.05-46.5), 0.22 (<0.05-3.1) and 0.14 (<0.05-1.3)mgkg(-1)dw; those at high-flow season were 1.2 (<0.05-13.1), 0.13 (<0.05-0.27) and 0.09 (<0.05-0.22)mgkg(-1)dw, respectively. Trace levels of dimethyl phthalate (DMP), diethyl phthalate (DEP) and di-n-octyl phthalate (DOP) in sediment were found in both seasons. Concentrations of DEHP in sediments were significantly affected by temperature, suspended solids, ammonia-nitrogen, and chemical oxygen demand. The highest concentration of DEHP in fish samples were found in Liza subviridis (253.9mgkg(-1)dw) and Oreochromis miloticus niloticus (129.5mgkg(-1)dw). BSAF of DEHP in L. subviridis (13.8-40.9) and O. miloticus niloticus (2.4-28.5) were higher than those in other fish species, indicating that the living habits of fish and physical-chemical properties of phthalates, like logKow, may influence the bioavailability of phthalates in fish. Our data suggested that DEHP level in river sediments were influenced by water quality parameters due to their effects on the biodegradation processes, and that the DEHP level in fish was affected by fish habitat and physiochemical properties of polluted contaminants.     

2-chlorophenol induced ROS generation in fish Carassius auratus based on the EPR method

In the present study, a secondary spin trapping technique was used followed by electron paramagnetic resonance (EPR) analysis, to study the potential of reactive oxygen species (ROS) production after fish (Carassius auratus) were injected i.p. with different doses (50, 100, 200, 250, 500mgkg(-1)) of 2-chlorophenol (2-CP). The ROS signal intensity of the EPR spectrum showed a significant increase (p<0.05, compared with the control) when the 2-CP dose was as low as 50mgkg(-1). There is a good relationship between the 2-CP administered doses and ROS generation. Based on the hyperfine splitting constants and shape of the EPR spectrum, the ROS which was generated in fish liver after intraperitoneal (i.p.) injection of 2-CP was identified as ()OH. SOD and CAT activities were found to be induced at lower doses of 2-CP. GSH levels fell below the control level following all treatments with 2-CP, and GSSG levels changed along with those of GSH. These observations indicated that the fish experienced oxidative stress. The strong positive correlation (r=0.966, p<0.005) between ()OH radical and lipid peroxidation suggested that lipid peroxidation was possibly induced by ()OH. The phase II detoxification enzyme glutathione-S-transferase (GST) may play an important role in 2-CP metabolism or excretion and, consequently, reduce ROS production. This study provides strong evidence that level of ROS is significantly increased in 2-CP stressed fish, and ROS may serve as a potential biomarker to indicate 2-CP contamination.     

A review of the occurrence, analyses, toxicity, and biodegradation of naphthenic acids

Naphthenic acids occur naturally in crude oils and in oil sands bitumens. They are toxic components in refinery wastewaters and in oil sands extraction waters. In addition, there are many industrial uses for naphthenic acids, so there is a potential for their release to the environment from a variety of activities. Studies have shown that naphthenic acids are susceptible to biodegradation, which decreases their concentration and reduces toxicity. This is a complex group of carboxylic acids with the general formula CnH(2n+Z)O2, where n indicates the carbon number and Z specifies the hydrogen deficiency resulting from ring formation. Measuring the concentrations of naphthenic acids in environmental samples and determining the chemical composition of a naphthenic acids mixture are huge analytical challenges. However, new analytical methods are being applied to these problems and progress is being made to better understand this mixture of chemically similar compounds. This paper reviews a variety of analytical methods and their application to assessing biodegradation of naphthenic acids.     

Determination of PCDD/Fs and dioxin-like PCBs in fish oils for feed ingredients by congener-specific chemical analysis and CALUX bioassay

The present research was intended to determine the suitability of the CALUX assay as a screening method for dioxins in fish oil used as a feed ingredient in Japan. Alteration of TEQ in fish oil according to newly proposed toxic equivalency factors (TEF) is also discussed. In the analysis, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in 41 fish oil samples were determined by using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) and CALUX bioassay. The mean TEQ values derived from 1998 WHO-TEF of PCDD/Fs and DL-PCBs were 2.6 and 9.9 pg g(-1) (ww), respectively. The levels of TEQ derived from the recently re-evaluated 2005 WHO-TEF were slightly lower than those of the former in both groups. Notably, the contribution of mono-ortho DL-PCBs to total 2005 WHO-TEQ was considerably decreased compared to the case of 1998 WHO-TEQ, resulting from the reduction in its TEF values, while the non-ortho DL-PCBs contribution was increased. The mean TEQ determined by CALUX assay for PCDD/Fs was approximately three times higher, whereas DL-PCBs was approximately two times lower than WHO-TEQ determined by HRGC/HRMS; the sum of PCDD/Fs and DL-PCBs was very similar by both methods. The correlation coefficients of TEQ between the CALUX assay and HRGC/HRMS analysis were 0.84, 0.89, and 0.90 for PCDD/Fs, DL-PCBs, and the sum, respectively. These results suggest that the CALUX assay is a very useful method for the screening of dioxin-related compounds in fish oils.     

The effect of oil sands process-affected water and naphthenic acids on the germination and development of Arabidopsis

Oil sands mining in the Athabasca region of northern Alberta results in the production of large volumes of oil sands process-affected water (OSPW). We have evaluated the effects of OSPW, the acid extractable organic (AEO) fraction of OSPW, and individual naphthenic acids (NAs) on the germination and development of the model plant, Arabidopsis thaliana (Arabidopsis). The surrogate NAs that were selected for this study were petroleum NAs that have been used in previous toxicology studies and may not represent OSPW NAs. A tricyclic diamondoid NA that was recently identified as a component of OSPW served as a model NA in this study. Germination of Arabidopsis seeds was not inhibited when grown on medium containing up to 75% OSPW or by 50 mg L⁻¹ AEO. However, simultaneous exposure to three simple, single-ringed surrogate NAs or a double-ringed surrogate NA had an inhibitory effect on germination at a concentration of 10 mg L⁻¹, whereas inhibition of germination by the diamondoid model NA was observed only at 50 mg L⁻¹. Seedling root growth was impaired by treatment with low concentrations of OSPW, and exposure to higher concentrations of OSPW resulted in increased growth inhibition of roots and primary leaves, and caused bleaching of cotyledons. Treatment with single- or double-ringed surrogate NAs at 10 mg L⁻¹ severely impaired seedling growth. AEO or diamondoid NA treatment was less toxic, but resulted in severely impaired growth at 50 mg L⁻¹. At low NA concentrations there was occasionally a stimulatory effect on root and shoot growth, possibly owing to the broad structural similarity of some NAs to known plant growth regulators such as auxins. This report provides a foundation for future studies aimed at using Arabidopsis as a biosensor for toxicity and to identify genes with possible roles in NA phytoremediation.     

A detailed field-based evaluation of naphthenic acid mobility in groundwater

An anaerobic plume of process-affected groundwater was characterized in a shallow sand aquifer adjacent to an oil sands tailings impoundment. Based on biological oxygen demand measurements, the reductive capacity of the plume is considered minimal. Major dissolved components associated with the plume include HCO₃, Na, Cl, SO₄, and naphthenic acids (NAs). Quantitative and qualitative NA analyses were performed on groundwater samples to investigate NA fate and transport in the subsurface. Despite subsurface residence times exceeding 20 years, significant attenuation of NAs by biodegradation was not observed based on screening techniques developed at the time of the investigation. Relative to conservative tracers (i.e., Cl), overall NA attenuation in the subsurface is limited, which is consistent with batch sorption and microcosm studies performed by other authors. Insignificant biological oxygen demand and low concentrations of dissolved As (< 10 µg L^− 1) in the plume suggest that the potential for secondary trace metal release, specifically As, via reductive dissolution reactions driven by ingress of process-affected water is minimal. It is also possible that readily leachable As is not present in significant quantities within the sediments of the study area. Thus, for similar plumes of process-affected groundwater in shallow sand aquifers which may occur as oil sands mining expands, a reasonable expectation is for NA persistence, but minimal trace metal mobilization.     

Nationwide monitoring of mercury in wild and farmed fish from fresh and coastal waters of Korea

Mercury (Hg) concentrations were monitored in wild and cultured fish collected from fresh and coastal waters in the Korean peninsula from April 2006 to August 2008 nationwide. Total Hg concentrations were reported for 5043 fish samples, including 78 species from 133 locations. Significant interspecies variation was noted in the Hg levels. The average Hg concentration in each fish species ranged from 6.31 μg kg⁻¹ for mullet (Mugil cephalus) to 200 μg kg⁻¹ for mandarin fish (Siniperca scherzeri). Among the species collected, the maximum concentration of Hg, 1720 μg kg⁻¹, was measured in an Amur catfish (Silurus asotus). Only wild freshwater fish exceeded the WHO ingestion standard. Wild freshwater piscivorous fish samples from a large artificial upstream lake contained the highest Hg levels. Hg concentrations were compared between fish groups categorized as wild and farmed fish from freshwater and coastal waters. Although the wild freshwater fish had similar size ranges, their Hg concentrations were higher than those of the other groups. Compared to the feed of farmed marine and freshwater fishes, the prey of wild freshwater fish had a higher Hg concentration, and the total Hg concentrations in freshwater and associated sediment samples were higher than those in coastal water and associated sediment samples. In the freshwater environment, piscivorous fish bioaccumulated two times more Hg than carnivorous and omnivorous fish and four times more than planktivorous fish. The difference in Hg concentrations among trophic groups might have been due to differences in the size of fish, in addition to the variations among different trophic groups. These data will be useful for developing the fish consumption advisory as a management measure to reduce Hg exposure.     

Diastereoisomer- and enantiomer-specific determination of hexabromocyclododecane in fish oil for food and feed

Fish oils are one of the main sources of ω-3 fatty acids. However, they can present elevated levels of some lipophilic pollutants, such as hexabromocyclododecanes (HBCDs). Since data about HBCDs in fish oil samples are very limited, in this study, 25 samples of fish oil for feed and food have been analyzed. Total HBCDs, as well as, α-, β- and γ-diastereoisomers have been determined. Total HBCDs ranged from 0.09 to 26.8 ng g⁻¹, with higher concentrations in fish oil for feed (average value of 9.69 ng g⁻¹) than those for food (1.14 ng g⁻¹). Concentrations of α-HBCD (average value of 4.12 ng g⁻¹ in feed samples and 0.48 ng g⁻¹ in food samples) and γ-HBCD (5.05 and 0.43 ng g⁻¹ respectively) were higher than that of β-HBCD (0.52 and 0.19 ng g⁻¹ respectively) in most of the samples. However, none of them was predominant in the samples. Concentrations of HBCDs were compared to concentrations of other pollutants and correlation between dioxin and dioxin-like PCBs levels and HBCDs levels were observed. Intake of HBCDs was calculated for fish oil with human consumption purposes and it ranged from 0.08 to 5.38 ng HBCDs d⁻¹, which could contribute significantly to HBCDs total intake. Enantiomeric fractions were also determined. No clear enrichment was observed for γ-HBCD, while (−)-α-HBCD enrichment was detected in some samples.     

Volatile compounds in flavor-tainted fish from the Upper Wisconsin River

Fillets from Walleye pike (Stizostedion vitreum) and Northern pike (Esox lucius) captured from the Upper Wisconsin River were analyzed for volatile components using simultaneous steam distillation-extraction and GC-MS techniques. Based on comparative odor assessments of eluting GC fractions and GC-MS analysis between control and tainted fish, trace amounts (ppb) of alkylphenols (2-isopropyl-, 4-isopropyl-, 2,4-diisopropyl-, 2,5-diisopropyl-, 2,6-diisopropyl-, 3,5-diisopropyl-, 5-methyl-2-isopropyl-, and 2-methyl-5-isopropyl-) and thiophenol were identified as the principal contributors to flavor-tainting found in fish during the spring of the year. Geosmin and 2-methylisoborneol were major contributors to mustiness flavor-tainting occurring in fish captured in the late summer and were more abundant in downstream fish than in upstream control fish.