The evaluation for alterations of DOM components from upstream to downstream flow of rivers in Toyama (Japan) using three-dimensional excitation-emission matrix fluorescence spectroscopy

The dissolved organic matter (DOM) is one of the important factors for controlling water quality. The behavior and constitutions of DOM is related to the risk of human health because it is able to directly or indirectly affect the behavior, speciation and toxicity of various environmental pollutants. However, it is not easy to know the contents of DOM components without using various complicated and time consuming analytical methods because DOM is a complex mixture and usually exists at low concentration. Here, we describe the fluorescence properties of DOM components in water samples collected from four rivers in Toyama, Japan by means of the three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy. In order to evaluate the alterations of DOM components in each of the river during the flow from upstream to downstream, the patterns of relative fluorescence intensity (RFI) at six peaks which are originated from fluorophores including humic-like and protein-like components were investigated. The changes in the patterns of RFI values at each of the peak and the concentration of dissolved organic carbon (DOC) for each river water sample were discussed in connection with the differences of land use managements and basic water quality parameters, such as pH, EC, turbidity, Fe(3+), T-N, NO(3)-N, T-P, PO(4)-P, chlorophyll a, DOC and N/P ratio. The DOC concentrations in the water samples collected from these rivers were relatively low (0.63-1.16 mg/L). Two main peaks which have a strong RFI value expressed a positive correlation with the DOC concentration (r = 0.557, 0.535). However, the correlations between the RFI values for other four peaks and the DOC concentration were below 0.287. The alterations of DOM components during the flow of a river from upstream to downstream were investigated from the changes in the patterns of RFI values for six fluorescent peaks. It was clarified that the great increase of RFI values in peak A and peak T from river water located in urban area showed high concentration of PO(4)-P and Fe(3+), and low N/P ratio due to the high biological activities. The values of fluorescence index (FIX) and biological index (BIX) were as high as 1.60 and 0.72, respectively.     

Influence of 17β-estradiol binding by dissolved organic matter isolated from wastewater effluent on estrogenic activity

The aims of this study were to determine the sorption coefficient (Log K_DOC) of 17β-estradiol (E2), according to the size and composition of dissolved organic matter (DOM) isolated from wastewater effluent using a fluorescence quenching (FQ) method, and to measure the estrogenic changes due to the extent of E2 sorption onto effluent DOM (EfOM) by using an E-screen bioassay. The highest log K_DOC of E2 for a DOM size fraction less than 0.2 μm was observed by 4.87±1.87 L kg⁻¹_DOC, and its estrogenicity was the lowest among all the size fractions at 1.2 ng-EEQ L⁻¹. However, E2 estrogenicity for a DOM size fraction less than 5 kDa was as high as that for the positive control due to the absence of fulvic acid- and protein-like DOM to bind with E2. The estrogenic activity for the hydrophobic fraction bound with E2 was significantly reduced to 1.6 ng-EEQ L⁻¹, while that for the hydrophilic fraction having no binding with E2 was 2.6 ng-EEQ L⁻¹, which was similar to that of the positive control (i.e., 2.8 ng-EEQ L⁻¹). The results support a conclusion that the change in estrogenicity was due to the strong sorption affinity of E2 onto DOM.     

Relative Contributions of Aqueous and Dietary Uptake of Hydrophobic Chemicals to the Body Burden in Juvenile Rainbow Trout

This study assessed the relative contributions of aqueous versus dietary uptake of three hydrophobic chemicals, 1,2,4-trichlorobenzene (1,2,4-TCB), 1,2,3,4,5-pentachlorobenzene (PeCB), and 2,2′,4,4′,6,6′-hexachlorobiphenyl (HCBP). Juvenile rainbow trout (Oncorhynchus mykiss) were exposed separately to chemically spiked water and food for 4 days and 12 days, respectively. Chemical concentrations were measured in the food, water, and tissues, and this allowed calculation of uptake rate constants (k₁ from water exposure, k_d from food exposure). The k₁ values for the three test chemicals were approximately five orders of magnitude greater than the k_d values. Using these measured uptake rate constants, a simulation model was used to predict the relative aqueous versus dietary uptake when fish were exposed simultaneously to water and food contaminated with these hydrophobic chemicals. The model predicted for all three test chemicals that the two uptake routes would contribute equally to the chemical body burden in fish whenever the food:water chemical concentration ratio was near 10⁵. However, using food:water chemical concentration ratios that might be expected in nature, the model predicted that gill uptake could account for over 98% of fish body burden for both 1,2,4-TCB and PeCB uptake (log K_ow values of 3.98 and 5.03, respectively). For HCBP (log K_ow of 7.55), the model predicted that the dietary uptake could contribute over 85% of the body burden. Thus, depending on the actual food:water chemical concentration ratio, aqueous uptake via the gills can predominate even when the chemicals have a log K_ow value greater than 5.0. In addition, we confirmed that dietary uptake of hydrophobic xenobiotics increases with increasing log K_ow. Received: 30 November 1999/Accepted: 3 May 2000     

Biotransformation and toxicokinetics of trichloroanilines in fish in relation to their hydrophobicity

Biotransformation, bioconcentration, uptake and elimination were studied in guppy (Poecilia reticulata) for a series of trichloranilines and a trichlorobenzene. Experimentally determined bioconcentration (BCF) values for trichloroanilines were less than those calculated based on a relation between BCF and K_ow for chlorobenzenes, and differences between the BCF values of isomers were observed. The uptake rate constants of all chemicals tested were approximately equal. The values of the elimination rate constants of two isomers (2,3,4-trichloroaniline and 3,4,5-trichloroaniline) were higher than calculated values based on a relation between log K_ow and elimination rate constants for chlorobenzenes. These higher elimination rate constants can be explained by a substantial influence of biotransformation. It was shown that these compounds are N-acetylated by the guppy. In contrast, 2,4,5-trichloroaniline also showed a relatively high elimination rate constant; however, no acetylation product was detected. The elimination rate constants of 1,2,3-trichlorobenzene and 2,4,6-trichloroaniline, the isomer with the highest BCF value, were equal to the calculated elimination rate constants indicating that biotransformation does not influence the elimination of these compounds. Biotransformation products for these compounds were not detected.     

Effect of Calcium and pH on Copper Binding and Rhizotoxicity to Pea (Pisum sativum L.) Root: Empirical Relationships and Modeling

The accumulation and toxicity of Cu to pea (Pisum sativum L.) roots were investigated. The root uptake of Cu and Ca varied with Ca and H activities. Calcium, H, and Cu competed for root binding with high pH and low Ca favoring more Cu uptake. Root elongation was highly sensitive to root Ca content and correlated better with root-bound Ca and Cu content than with merely dissolved Cu concentrations. The prediction of root elongation needs to include both the root-bond Cu and Ca as predictor variables whenever environmental conditions (low pH and low Ca) decrease Ca accumulation. A multielement uptake model was developed to describe Cu and Ca accumulation by treating the pea roots as a collection of three biotic ligands with known site densities ( Q_\textLj Q_{{{\text{L}}_{j} }} ) and proton-binding constants ( K_\textHLj K_{{{\text{HL}}_{j} }} ). A series of binding constants were derived. The log K_\textCuLj K_{{{\text{CuL}}_{j} }} (j = 1, 2, 3) values were estimated at pH 6 and 0.2 mM CaCl₂ as 2.36, 4.36, and 0.32, respectively. The derived formation constants can be incorporated into standard solution speciation models to estimate the bioaccumulation of Cu in plant roots under multielement conditions.     

Sorption of Chlorophenolates in Soils and Aquifer and Marine Sediments

This article describes the sorption behavior of 3 hydrophobic ionizable chlorophenols—2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, and pentachlorophenol—in different types of natural sorbents. A series of experiments was carried out with 11 topsoil samples, 9 aquifer sediments, and 12 marine sediments differing in pH, organic-matter content, and mineral composition and presumably also in type of organic matter due to their differing origins. Ionized forms of chlorophenols dominated in almost all sorption experiments. Freundlich isotherm coefficients K_f and 1/n, as well as organic-matter sorption coefficient (log K_om) and free-energy change (G^o), were calculated for all 3 compounds in all sorbents. The sorption intensity of predominantly ionized chlorophenols increased linearly with the increase of sorbent organic-matter content and decreased with the increasing sorbent pH. Different sorption behavior of all 3 compounds in marine sediments with respect to topsoils and aquifer sediments was indicated by significant differences in K_f and 1/n coefficients as well as in log K_om and G^o values. The highest K_f and log K_om values were obtained for sorption of chlorophenolic compounds in topsoils and the lowest in marine sediments, although both groups of sorbents had similar organic-matter content. The 1/n coefficient, reflecting the isotherm nonlinearity, was considerably lower than unity for all compounds in almost all sorbents. The most significant deviation of sorption isotherms from linearity was observed in marine sediments. Only marine sediments showed a linear increase in sorption intensity of all 3 compounds with the increase in sorbent-specific surface area. These results pointed to a different mechanism of sorption in marine and terrestrial sorbents and confirmed that the capacity of sorption was related to amount as well as type and origin of organic matter.     

Metal(II) complexes of 2,2′-bipyridyl-6-carbothioamide as anti-tumor and anti-fungal agents

Complexes of Fe(II), Co(II), Ni(II), Cu(II), Cd(II), Pd(II), Pt(II) and Zn(II) with the anti-tumor agent 2,2′-bipyridyl-6-carbothioamide (bpyta, 1) were prepared and characterized. All these metal(II) complexes were screened for their cytostatic activities in vitro against murine P388 leukemia. The copper(II) complex 2f was found to be 12-fold more active than ligand 1. bpyta and its complexes were also evaluated for their anti-fungal activities. Some of the studied complexes displayed significant anti-fungal activity which, however, was lower than that of the parent ligand.     

Removal of Mixed Pesticides from Aqueous Solutions using Organoclays: Evaluation of Equilibrium and Kinetic Model

Removal of mixed pesticides, namely alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, p,p′-DDT and two metabolites p,p′-DDE and endosulfan sulphate from aqueous solution by batch adsorption onto three commercial organo-modified montmorillonite clays [modified with octadecylamine (ODA-M), modified with dimethyl- dialkylamine (DMDA-M) and modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M)] were investigated. Effect of process variables, mainly contact time and initial concentration of mixed pesticides, on adsorption phenomenon were evaluated. To understand the adsorption kinetic pseudo-first-order and pseudo-second-order models were tested. The pseudo-second-order model provided the best fit for explaining adsorption kinetics, on the basis of high correlation coefficient (r) and normalized percent deviation values. The adsorption equilibrium was explained by the Freundlich isotherm (r = 0.951–0.992). High values (0.17–0.52 mg g^?1) of Freundlich constant (K_f) indicated higher affinity of pesticides towards all three organoclays, as a result of hydrophobic interaction between the adsorbent/adsorbate systems. Pesticides with high octanol–water partition coefficient (K_ow) and low water solubility showed faster adsorption with higher K_f values as compared to the pesticides with low K_ow and high water solubility. The order of organoclays for removal efficiency of mixed pesticide was ODAAPS-M > DMDA-M > ODA-M. These findings may find application to decontaminate or treat mixed pesticide contaminated industrial/agricultural waste waters.     

Effect of Major Cations and pH on the Acute Toxicity of Cadmium to the Earthworm <Emphasis Type="Italic">Eisenia fetida</Emphasis>: Implications for the Biotic Ligand Model Approach

The purpose of this study was to characterize the individual effect of different cations (Ca²⁺, Mg²⁺, Na⁺, K⁺, and H⁺) on the acute toxicity of Cd to the earthworm Eisenia fetida. Higher activities of the considered cations increased the 48-h LC₅₀ (expressed as Cd²⁺ activities) linearly to different extents in simulated soil solution. The conditional constants for the binding of H⁺ (log K = 5.41), Cd²⁺ (log K = 4.0), Ca²⁺ (log K = 3.35), Mg²⁺ (log K = 2.82), Na⁺ (log K = 1.57), and K⁺ (log K = 2.31) to the biotic ligand (BL) of E. fetida were derived from the toxicity data based on the biotic ligand model (BLM). Furthermore, it was calculated that on average 72% of the BL sites needed to be occupied by Cd²⁺ to induce 50% lethal effect. Autovalidation of the model with the results of the test sets showed that 48-h LC₅₀ could be predicted within a factor of two.     

Development and field validation of a predictive copper toxicity model for the green alga Pseudokirchneriella subcapitata

In this study, the combined effects of pH, water hardness, and dissolved organic carbon (DOC) concentration and type on the chronic (72-h) effect of copper on growth inhibition of the green alga Pseudokirchneriella subcapitata were investigated. Natural dissolved organic matter (DOM) was collected at three sites in Belgium and The Netherlands using reverse osmosis. A full central composite test design was used for one DOM and a subset of the full design for the two other DOMs. For a total number of 35 toxicity tests performed, 72-h effect concentration resulting in 10% growth inhibition (EbC10s) ranged from 14.2 to 175.9 micrograms Cu/L (factor 12) and 72-h EbC50s from 26.9 to 506.8 micrograms Cu/L (factor 20). Statistical analysis demonstrated that DOC concentration, DOM type, and pH had a significant effect on copper toxicity; hardness did not affect toxicity at the levels tested. In general, an increase in pH resulted in increased toxicity, whereas an increase of the DOC concentration resulted in decreased copper toxicity. When expressed as dissolved copper, significant differences of toxicity reduction capacity were noted across the three DOM types tested (up to factor 2.5). When expressed as Cu2+ activity, effect levels were only significantly affected by pH; linear relationships were observed between pH and the logarithm of the effect concentrations expressed as free copper ion activity, that is, log(EbC50Cu2+) and log(EbC10Cu2+): (1) log(EbC50Cu2+)= - 1.431 pH + 2.050 (r2 = 0.95), and (2) log(EbC10cu2+) = -1.140 pH -0.812 (r2 = 0.91). A copper toxicity model was developed by linking these equations to the WHAM V geochemical speciation model. This model predicted 97% of the EbC50dissolved and EbC10dissolved values within a factor of two of the observed values. Further validation using toxicity test results that were obtained previously with copper-spiked European surface waters demonstrated that for 81% of tested waters, effect concentrations were predicted within a factor of two of the observed. The developed model is considered to be an important step forward in accounting for copper bioavailability in natural systems.     

A QICAR approach for quantifying binding constants for metal-ligand complexes

Relative metal-ligand complex stability is predicted by evaluating the relationships between physicochemical properties of metal ions and their experimental biotic and abiotic binding constants, K. Linear regression analysis showed that the softness index (σ_p) and the covalent index (χ²_mr) were especially useful in model construction for rainbow trout (Oncorhynchus mykiss), fathead minnows (Pimephales promelas) and crustaceansaquatic (Daphnia magna) based on RMSE and F-ratio criterion (F_observed/F_critical of ≥4). The absolute value of the log of the first hydrolysis constant |log K_OH| correlated best with log K values for barley (R²=0.74, p=0.02) and earthworm (R²=0.82, p=0.01). In contrast, the ionic index Z²/r explained most of the variability of log K values for the two clays kaolinite and montmorillonite, while |log K_OH| was a better predictor of the generic NICA-Donnan parameters for HA and FA (0.67<R²<0.80, 0.002<p<0.01). This implies dissimilarity of the nature of the binding sites on biotic and chemical ligands and the different binding mechanisms between metal and ligands.     

Predicting the Toxicity of Substituted Phenols to Aquatic Species and Its Changes in the Stream and Effluent Waters

The changes in the acute toxicity of 16 phenols toward Selenastrum capricornutum and Daphnia magna were examined as a function of their physical/chemical properties. The results demonstrated that phenols with a higher octanol-water partition coefficient (K_ow) had a higher toxicity toward aquatic organisms. The toxicity of phenols was closely related to the log K_ow values, with correlation coefficients of 0.93 (except for the nitrophenols) and 0.89 for S. capricornutum and D. magna, respectively. The changes in the phenols toxicities in the site waters (i.e., stream and effluent waters) were investigated by calculating the water effect ratios (WER) from the results of the toxicity tests in the site waters using D. magna. The results showed that the degree of ionization for each phenolic compound was altered by the differences in the dissociation constant (pK_a), and the change in the toxicity could be predicted. Therefore, the WER should be considered when the toxicity of phenolic compounds is estimated in site waters. The quantitative structure-activity relationships (QSAR) study showed that the toxicity of the phenols to D. magna could be predicted by the hydrophobicity (log K_ow) alone and by combining the log K_ow with pK_a, while the toxicity to S. capricornutum was predicted by a combination of hydrophobicity (log K_ow) and E_LUMO (or pK_a).     

Occurrence and Partitioning of Phenolic Endocrine-Disrupting Chemicals (EDCs) Between Surface Water and Suspended Particulate Matter in the North Tai Lake Basin, Eastern China

Concentrations and distribution of octylphenol (OP), nonylphenol (NP), and bisphenol A (BPA) in surface water and suspended particulate matter (SPM) from the north Tai Lake basin, China were studied. Aqueous and particulate (dry weight) concentrations for OP, NP, and BPA varied from 10.5–1,175 ng/L to <1.52–5,365 ng/g, respectively. The spatial distribution of endocrine-disrupting chemicals (EDCs) in dissolved and particulate phases showed that the amount of EDCs in water that were adsorbed to SPM gradually increased from upstream to downstream. There were good correlations between particulate EDCs and particulate organic carbon, with correlation coefficients of 0.46–0.57. Regression analysis of in situ SPM–water partition coefficients (log K’ _oc) and log K _ow for EDCs indicated that the hydrophobicity of chemicals greatly contributed to their SPM–water partitioning. Strong positive correlations (r = 0.68–0.82) among in situ log K’ _oc of OP, NP, and BPA and flow velocity of water were observed, indicating the critical importance of riverine hydrodynamics on the sorption of these compounds.     

Population Growth Kinetics of Tetrahymena pyriformis Exposed to Selected Nonpolar Narcotics

This study describes effects of selected nonpolar narcotics of varying hydrophobicity (quantified by the 1-octanol-water partition coefficient, log K_ow) and molecular structure on the population growth kinetics of the freshwater ciliate Tetrahymena pyriformis. The response of Tetrahymena exposed to different nonpolar narcotics varied from a change in generation time to a change in lag phase with similar generation time compared to control. Two narcotics with high (>3.00), intermediate (>0.00 and <3.00), and low log K_ow (<0.00) values were tested. Growth of Tetrahymena inhibited up to 85% by the high log K_ow toxicants (2-decanone and butylbenzene) grew with similar rates as the control, but exhibited increased lag time, suggesting that the protozoan became acclimated to toxicant stress. Results from growth of Tetrahymena in the low log K_ow toxicants (ethanol and acetone) indicate an increased generation time with increasing concentration. Cells inhibited by the intermediate log K_ow chemicals, 1-pentanol and anisole, exhibited a response that was a combination of the previously mentioned two contrary responses. Cells inhibited <35% with 1-pentanol and <50% with anisole grew with similar generation times as control flasks, whereas in cells inhibited >35% or >50%, respectively, the doubling times were longer than control growth. Received: 30 October 1996/Accepted: 12 May 1997     

Aqueous Solubility, n-Octanol–Water Partition Coefficient, and Sorption of Five Selective Serotonin Reuptake Inhibitors to Sediments and Soils

Aqueous solubilities (S _w) and n-octanol–water partition coefficients (K _ow) of five selective serotonin reuptake inhibitors (SSRIs) were measured and sorption to two sediments and three soils with organic matter contents ranging from 0.16% to 1.77% and pH ranging between 5.0 and 7.8 was investigated using a batch equilibrium method. SSRIs had high S _w (3,022–15,460 mg/l) and relatively low log K _ow (1.12–1.39). Sorption isotherms followed the Freundlich equation. All SSRIs had sorption capacities of greater than 91% except fluvoxamine with a minimum capacity of 73%. Organic matter contents partly affected sorption, however no correlation between sorption characteristics and cation exchange capacity (CEC) or clay content was observed for any SSRI or adsorbent. Values of K _f, K _d, and log K _oc ranged from 39 to 18,342, from 60 to 42,579, and 3.35 to 6.02 for the SSRIs. SSRIs likely exhibit mixed mechanisms of sorption such as ionic binding in addition to hydrophobic interactions.     

Relation between physicochemical properties of phenols and their toxicity and accumulation in fish

The 96-hr LC₅₀ values of 21 substituted phenols for the guppy (Poecilia reticulata) were determined at pH levels 6–8 and related to the lipophilicity defined as log P from the 1-octanol/water system, and to the ΔpK_a value (pK_a of phenol −pK_a). Log P was the more important parameter and exhibited a good correlation with log(1/LC₅₀) at all pH levels. The contribution of ΔpK_a when introduced as a second parameter into the regression equation was dependent on the pH of water: at pH 6 it was positive but turned negative as the pH was raised to 8. If the LC₅₀ values were corrected for ionization using an empirically formulated relation between toxicity and pH, the resulting regression equation could be used to predict the toxicity at any pH from 6 to 8. When corrected for ionization, log BCF (the bioconcentration factor) of 8 phenols was highly correlated with Log P but not with ΔpK_a. The regression of log BCF on Log P sufficed to explain the regression of toxicity on lipophilicity.     

Quantitative structure-activity relationships and mixture toxicity studies of chloro- and alkylanilines at an acute lethal toxicity level to the guppy (Poecilia reticulata)

Quantitative structure-activity relationships (QSARs) were calculated for the acute lethal toxicities (14-day LC₅₀) to the guppy (Poecilia reticulata) of anilines, with several hydrophobicity characteristics and the Hammett σ constant as parameters. Calculated and experimental P_oct values and II constants were used as hydrophobicity characteristics. Introduction of Hammett constants improved the quality of the QSARs. Together with the QSAR studies the toxicities of mixtures of the anilines were determined. The toxicities of three mixtures did not deviate from concentration addition.     

A Preliminary Assessment of Polycyclic Aromatic Hydrocarbon Distribution in the Kenting Coral Reef Waters of Southern Taiwan

This distribution and variation of 45 polycyclic aromatic hydrocarbons (PAHs) in the waters of Kenting coral reefs were investigated by using sensitive research-grade sampling and analytical methods. The concentration levels of total PAHs (including particulate and dissolved PAHs) in the Kenting waters were relatively low, ranging from 2.2 to 34.4 ng/L. There was no significant spatial difference in PAH concentrations among the sampling stations, even between the surface and bottom waters. The fraction of dissolved PAHs on average was greater than that of particulate PAHs due to the small amount of total suspended particles. The partition coefficients between the particulate and dissolved phase (log K _oc) were positively correlated with their log K _ow values (r ² = 0.67, n = 80), except for the more hydrophobic PAHs with log K _ow values greater than 5.91. Results of principal component analysis indicate that the patterns of particulate PAH compositions were similar through the Kenting waters in the fall and winter, whereas there was a significant spatial difference between the spring and summer samples, which might be affected by a combination of land runoff and coastal currents. PAHs along the Kenting coasts were dominated by low-molecular PAHs, which have higher solubility than high-molecular PAHs. Based on isomer ratios, analysis of the source of PAHs in the Kenting coastal waters demonstrated that the PAHs come mostly from petroleum and, to a lesser degree, from combustion.     

Quantitative structure-toxicity relationships and volume fraction analyses for selected esters

The acute toxicity of aliphatic and aromatic mono and diesters in two eucaryotic organisms was compared. The test systems were the static 2-d Tetrahymena pyriformis 50% population growth impairment (IGC ₅₀ ^–1 ) assay, and the flow-through 4-d Pimephales promelas 50% mortality (LC ₅₀ ^–1 ) assay. In ciliates, esters act via the nonpolar narcosis mechanism of toxic action. This was indicated by: the high quality 1-octanol/water partition coefficient (log K_ow) dependent quantitative structure-activity relationship (QSAR), log IGC ₅₀ ^–1 =0.79 (log K_ow)–1.93, n=15, r²=0.945, s=0.22, f=222.37 Pr>f=0.0001); volume fraction (V_f) (0.8e-02); and a coefficient (0.3) which are not different from other nonpolar narcotics. In vivo hydrolysis in Tetrahymena appears to be insignificant. However, in fish, presumably because of more active esterases, in vivo hydrolysis is significant and leads to greater toxicity of esters than observed for nonpolar narcotics. Moreover, it leads to a unique high quality QSAR, log LC ₅₀ ^–1 =0.64 (log K_ow)–0.64, n=14, r²=0.945, s=0.22, f=207.08, Pr>f=0.0001). Due to in vivo hydrolysis, a nonreducing concentration gradient is formed between water and fish. Therefore, the fish take up more toxicant as compared to a situation that leads to thermodynamic equilibrium. Additional information about the mechanism of ester toxicity in fish was gained by applying corrections for hydrolysis in volume fraction analyses. The corrected V_f (0.6e-02) is very close to the one found for nonpolar narcotics (0.7e-02). These analyses suggest that esters which hydrolyze to an acid and aliphatic alcohol act as nonpolar narcotics. Moreover, the mechanism of toxic action of esters that yield a phenol upon hydrolysis is mixed and represents polar and nonpolar narcoses.     

Quantitative Biomonitoring of PAHs Using the Barnes Mussel (<Emphasis Type="Italic">Elliptio complanata</Emphasis>)

The elimination rate constants (k ₂) of nine polycyclic aromatic hydrocarbons (PAHs) were examined for the freshwater mussel Elliptio complanata. The concentrations of fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and indeno[1,2,3-c,d]pyrene revealed a significant inverse relationship with time and their k ₂ values ranged from 0.10 to 0.22 day⁻¹. The k ₂ values of these significantly cleared PAHs were similar to k ₂ values observed for nonmetabolized organochlorines in mussels previously reported in the literature. The inverse relationship between k ₂ and K _ow provides evidence that the nine PAHs were being passively eliminated from the mussels and that they can be used to calibrate the mussel as a quantitative biomonitor. A general expression relating elimination rate constants and chemical K _ow is derived for hydrophobic contaminants in E. complanata. The k ₂ versus log K _ow regression equation for mussels developed herein was similar to other studies documenting the elimination of PCBs and PAHs in a number of bivalve species. Received: 13 August 2001/Accepted: 25 April 2002