Toxic effects of animal manures and sewage sludge as supplementary feeds for the common carp, Cyprinus carpio

Activated sludge, chicken manure and pig manure were tested for their toxic effects as supplementary feeds for the common carp, Cyprinus carpio. The acute toxicity test showed that animal manures were more toxic than activated sludge (e.g., 96-h LC₅₀ values for pig manure and chicken manure were 0.55% and 0.29%, respectively, while no effective value was revealed for activated sludge). This may be due to the inadequate processing of the manures which resulted in the release of harmful substances during decomposition.In general, body weights of all the fish fed the wastes decreased during the culture period. High heavy metal concentrations (Pb, Cu, Zn and Mn) were found accumulated in the flesh of the fish fed the wastes. It is suggested that waste materials should be pretreated and detoxified before using them as animal feeds.     

The effect of tetrahydrofuran on the enzymatic activity and microbial community in activated sludge from a sequencing batch reactor

Tetrahydrofuran (THF) is a toxic and carcinogenic compound that is commonly released from pharmaceutical, chemical and related industry wastewater. Currently, the effects of THF contamination on wastewater are unknown and a better understanding of THF toxicity toward biological processes in wastewater treatment is critical. In this study, we firstly investigated the toxic effects of THF on enzymatic activity and the microbial diversity in activated sludge from a sequencing batch reactor during long-term exposure to 10 mM THF. The activity of five enzymes (catalase, dehydrogenase, urease, phosphatase and protease) was remarkably decreased in the presence of 10 mM THF during a period of 85 days. Of these five affected enzymes, dehydrogenase activity was close to detection level limits and was nearly completely inhibited. Analysis of the microbial community demonstrated that THF, at a concentration of 10 mM, altered the distribution of microbes within the community and significantly decreased microbial diversity during long-term contamination, according to denaturing gradient gel electrophoresis (DGGE) analysis. The fraction of Actinobacteria increased in the community, while the fraction of Proteobacteria significantly decreased after THF exposure.     

Stability and surface activity of lactate dehydrogenase in spray‐dried trehalose

The stability of the model protein lactate dehydrogenase (LDH) during spray‐drying and also on subsequent dry storage was examined. Trehalose was used as a carrier. The spray‐drying temperatures T_inlet and T_outlet have a measurable effect on LDH inactivation. Low T_inlet produced the least process inactivation, but gave a high residual moisture content making the protein's storage stability poor. High T_inlet reduced residual moisture and improved storage stability, but at the cost of high process inactivation. As already found for other systems, addition of a surfactant (in this case polysorbate 80) could ameliorate process inactivation of LDH at T_inlet = 150 °C. Surfactant had, however, a deleterious effect on storage stability of LDH, the vital factor being the molar ratio of surfactant/protein in the dried product. By using electron spectroscopy it was shown that LDH has a 10 times higher surface concentration in the dried trehalose particles than expected for a homogeneous distribution. Surface tension measurements at the water/air interface proved that LDH is surface active, although the Gibbs equation appeared to be inapplicable. Calculations of spray‐droplet formation time and drying time indicate than the extent of diffusion‐driven LDH adsorption to the liquid/air interface is sufficient to account for the measured amount of LDH inactivation during spray‐drying. The presence of 0.1% polysorbate 80 to the spray solution prevents LDH from appearing at the surface of the dried particles. As a negative control, the phosphatide Lipoid E 80 does not prevent the appearance of LDH in the surface according to electron spectroscopy and does not therefore prevent LDH inactivation during spray‐drying at T_inlet = 150 °C.     

Mechanism of action of Rhodiola imbricata Edgew during exposure to cold,hypoxia and restraint (C–H–R) stress induced hypothermia and post stress recovery in rats

Mechanism of rhodiola root extract adaptogenic activity was studied in rats. The extract was orally administered in rats (100 mg/kg body weight), 30 min prior to cold (5 °C)-hypoxia (428 mmHg)-restraint (C-H-R) exposure up to fall of T_rec23 °C and recovery (T_rec37 °C) from hypothermia. In untreated control rats serum lactate and non-esterified fatty acids (NEFA) increased on attaining T_rec23 °C with decreased blood enzyme activities hexokinase (HK), phosphofructokinase (PFK), citrate synthase (CS) and glucose-6-phosphate dehydrogenase (G-6-PD), on attaining T_rec23 °C and T_rec37 °C. Decreases were also observed in liver and muscle tissues HK and G-6-PD enzyme activities and liver glycogen and CS on attaining T_rec23 °C and recovery; muscle PFK during recovery; muscle CS on attaining T_rec23 °C. Single and five doses of extract administration restricted increase in serum lactate values of rats on attaining T_rec23 °C and maintained blood NEFA in single dose extract treated animals, indicating improved utilization of NEFA as energy fuel. The single and five doses extract treatment decreased or better maintained tissue glycogen and enzyme activities, viz. HK, PFK, CS and G-6-PD, in blood, liver and muscle, on attaining T_rec23 °C and recovery. The results suggest that rhodiola extract treatment in rats shifted anaerobic metabolism to aerobic, during C-H-R exposure and post stress recovery.     

Stability of β-Galactosidase,a Model Protein Drug,Is Related to Water Mobility as Measured by 17O Nuclear Magnetic Resonance (NMR)

The inactivation of freeze-dried -galactosidase during storage was studied, focusing on the effect of water mobility as measured by the spin-lattice relaxation time, T ₁, of water using ¹⁷O NMR. Inactivation of -galactosidase lyophilized from phosphate buffer solution was studied as a function of water content, which in turn affected the T _l of water. An increase in the water content of freeze-dried -galactosidase brought about an increase in the T _l of water, as well as a rise in pH. For the freeze-dried enzyme with sufficient water content to be dissolved, the inactivation rate was related to the T _l of water rather than to the pH change. It is suggested that as the water content increases, the mobility of water around the enzyme increases, resulting in enhanced enzyme inactivation. The freeze-dried samples with limited moisture showed inactivation rates faster than those expected from the pH and water mobility, suggesting that the inactivation mechanism is different from that for the freeze-dried enzyme with a larger amount of water. Inactivation of -galactosidase in solutions was also studied as a function of phosphate buffer and sodium chloride concentrations, which in turn affected the T _l of water. Because the inactivation rate increased with increasing salt concentrations and the rate extrapolated to zero concentration was negligible, inactivation of the freeze-dried enzyme was apparently induced by the salts used as additives for lyophilization. The enhancing effect of phosphate buffer components, however, was reduced at higher concentrations, an effect related to the decrease in the T _l of water. This result may be ascribed to the decrease in water mobility caused by phosphate buffer components and is consistent with the observation that the inactivation rate of the freeze-dried enzyme with a relatively large amount of water decreased with decreasing T ₁ of water.     

The effect of toxic discharges on ATP content in activated sludge

ATP measured by the luciferin-luciferase bioluminescence assay was used to examine the effect of toxic substances on whole microbial communities in activated sludge mixed liquor samples. The response of the microorganisms to toxicants is rapid using ATP reduction as the criterion. The sensitivity of the mixed populations to various toxicant types (e.g., organic material and heavy metals) is lower than when using single species toxicity tests such as the Microtox bioassay. The differences in sensitivity is considered a function of acclimatization, modification of the toxicant by the waste physicochemical environment, and the predominance of less sensitive organisms than those used in the Microtox bioassay (Photobacterium phosphoreum). ATP bioluminescence is, however, considered an important rapid test utilizing natural waste treatment microorganisms in determining the toxicity of wastes discharged to sewer. It can detect whether wastewater will have an effect on the biodegradation capability of the resident population of microrganisms. © 1997 by John Wiley & Sons, Inc. Environ Toxicol Water Qual 12: 23–29, 1997     

Assessment of the acute toxic effects of the fungicide Ridomil plus 72 on aquatic organisms and soil micro‐organisms

The acute toxic effects of Ridomil plus 72 (Ridomil), used as a fungicide in agriculture, were studied under laboratory conditions. These effects on freshwater cladoceran (Chydorus eurynotus) and freshwater fish (Oreochromis niloticus) were determined using standard bioassay procedures. The 4 h LC₅₀ for Chydorus eurynotus was 6.9 mg/L and the 96 h LC₅₀ for Oreochromis niloticus was 1.1 mg/L. The toxicity of Ridomil to a mixed population of soil micro‐organisms was measured using oxygen uptake and growth as measured by turbidity. At short‐term exposure (48 min), Ridomil was moderately toxic to the culture at 5000 mg/L and above, based on an activity quotient (AQ) of 0.50–0.70. For longer exposure periods (up to 6 h), Ridomil was slightly toxic to the culture at 200 to 500 mg/L. At 1000 mg/L, Ridomil was moderately toxic and at 3000 mg/L and above, Ridomil was extremely toxic to soil microorganisms. The toxicity of metalaxyl (one of the two active ingredients of Ridomil) to these micro‐organisms was measured using growth as measured by the turbidity change. The average toxic endpoint (16 h IC₅₀) was 1100 mg/L. The acute toxic values of Ridomil found in these studies were much below the expected environmental concentrations resulting from normal applications of the chemical on a cocoa tree as a fungicide. ©2000 John Wiley & Sons, Inc. Environ Toxicol 15: 65–70, 2000     

Inhibition of respiration of activated sludge: Variability and reproducibility of results

Assessment of the toxicity of chemicals to the respiration of activated sludge microorganisms is a relatively simple and reproducible method when applied to a standard population of bacteria. However, activated sludge is, by nature, a variable commodity, and varying results are often reported. Within-plant variations can occur from day to day as a result of shifts in the bacterial population, probably caused by changes in the strength of components of the sewage feed. Between-plant variations can be considerably greater. Factors such as differing operating conditions and presence of industrial waste waters in the sewage can result in differing species composition of the sludge, which, in turn, may account for differing biooxidation rates of components of the waste water and thus different respiration rates. Sludge from different sources, and/or grown under different conditions, may also vary in response to inhibitors, because of varying degrees of reaction of some inhibitors with non-living sludge components. Therefore, in practice, it has been usual to consider EC₅₀ values from the inhibition of respiration of activated sludge test in terms of order of magnitude. Variations in EC₅₀ results of the ‘ISO’ inhibition of respiration test have been quantified for a number of chemicals, both within and between batches of sludge, and with sludges from different sources. The coefficient of variation of EC₅₀ results within batches of sludge was found to be approximately 9%. Between batch and between source variations were 28–76% depending on the test chemical.     

Soil microbial community responses to contamination with silver,aluminium oxide and silicon dioxide nanoparticles

Soil microorganisms are key contributors to nutrient cycling and are essential for the maintenance of healthy soils and sustainable agriculture. Although the antimicrobial effects of a broad range of nanoparticulate substances have been characterised in vitro, little is known about the impact of these compounds on microbial communities in environments such as soil. In this study, the effect of three widely used nanoparticulates (silver, silicon dioxide and aluminium oxide) on bacterial and fungal communities in an agricultural pastureland soil was examined in a microcosm-based experiment using a combination of enzyme analysis, molecular fingerprinting and amplicon sequencing. A relatively low concentration of silver nanoparticles (AgNPs) significantly reduced total soil dehydrogenase and urease activity, while Al₂O₃ and SiO₂ nanoparticles had no effect. Amplicon sequencing revealed substantial shifts in bacterial community composition in soils amended with AgNPs, with significant decreases in the relative abundance of Acidobacteria and Verrucomicrobia and an increase in Proteobacteria. In particular, the relative abundance of the Proteobacterial genus Dyella significantly increased in AgNP amended soil. The effects of Al₂O₃ and SiO₂ NPs on bacterial community composition were less pronounced. AgNPs significantly reduced bacterial and archaeal amoA gene abundance in soil, with the archaea more susceptible than bacteria. AgNPs also significantly impacted soil fungal community structure, while Al₂O₃ and SiO₂ NPs had no effect. Several fungal ribotypes increased in soil amended with AgNPs, compared to control soil. This study highlights the need to consider the effects of individual nanoparticles on soil microbial communities when assessing their environmental impact.     

Toxicities of triclosan, phenol, and copper sulfate in activated sludge

The effect of toxicants on the BOD degradation rate constant was used to quantitatively establish the toxicity of triclosan, phenol, and copper (II) against activated sludge microorganisms. Toxicities were tested over the following ranges of concentrations: 0-450 mg/L for phenol, 0-2 mg/L for triclosan, and 0-35 mg/L for copper sulfate (pentahydrate). According to the EC(50) values, triclosan was the most toxic compound tested (EC(50) = 1.82 +/- 0.1 mg/L), copper (II) had intermediate toxicity (EC(50) = 18.3 +/- 0.37 mg/L), and phenol was the least toxic (EC(50) = 270 +/- 0.26 mg/L). The presence of 0.2% DMSO had no toxic effect on the activated sludge. The toxicity evaluation method used was simple, reproducible, and directly relevant to activated sludge wastewater treatment processes.     

Alternative inocula as activated sludge surrogate culture for a toxicity test

The use of activated sludge to assess the potential toxicity and environmental impact of chemicals and wastewaters suffers from several drawbacks related to the heterogeneity, absence of standardization, and health risk associated with this mixed-sewage population. To search for reliable testing inoculum alternatives, the performance of two commercial inocula (BI-CHEM and BIOLEN M112), a garden-soil inoculum and a pure culture of Pseudomonas sp., was compared with an activated sludge inoculum (AS) in the inhibition respiration test ISO 8192-1986 (E). The respiration rates of microbial inocula were assayed for the reference compound 3,5-dichlorophenol. The acute toxicity values (IC(50)) ranged from 6.7 mg/L (Pseudomonas sp.) to 22.7 mg/L (garden soil), overlapping the expected values for activated sludge microorganisms despite the bacterial diversity. The assayed microbial inocula also showed higher reproducibility than AS and an overall similarity of catabolic profiles obtained with Biolog EcoPlates was observed between AS and some mixed inocula. These results point to the potential ability of such inocula as surrogate cultures in relevant activated sludge-based bioassays. New, well-defined, standardized, and safe tools will then be available for monitoring the ecological impact of hazardous substances and effluents, thus providing environmental protection.     

Effect of Activated Charcoal on Apixaban Pharmacokinetics in Healthy Subjects

Background

Activated charcoal is commonly used to manage overdose or accidental ingestion of medicines. This study evaluated the effect of activated charcoal on apixaban exposure in human subjects.

Methods

This was an open-label, three-treatment, three-period, randomized, crossover study of single-dose apixaban (20 mg) administered alone and with activated charcoal given at 2 or 6 h post-dose to healthy subjects. Blood samples for assay of plasma apixaban concentration were collected up to 72 h post-dose. Pharmacokinetic parameters, including peak plasma concentration (C _max), time to C _max (T _max), area under the concentration–time curve from time 0 to infinity (AUC_INF), and terminal half-life (T _½), were derived from apixaban plasma concentration–time data. A general linear mixed-effect model analysis of C _max and AUC_INF was performed to estimate the effect of activated charcoal on apixaban exposure.

Results

A total of 18 subjects were treated and completed the study. AUC_INF for apixaban without activated charcoal decreased by 50 and 28 %, respectively, when charcoal was administered at 2 and 6 h post-dose. Apixaban C _max and T _max were similar across treatments. The mean T _½ for apixaban alone (13.4 h) decreased to ~5 h when activated charcoal was administered at 2 or 6 h post-dose. Overall, apixaban was well tolerated in this healthy population, and most adverse events were consistent with the known profile of activated charcoal.

Conclusion

Administration of activated charcoal up to 6 h after apixaban reduced apixaban exposure and facilitated the elimination of apixaban. These results suggest that activated charcoal may be useful in the management of apixaban overdose or accidental ingestion.     

An in vitro microcalorimetric method for studying the toxic effect of cadmium on microbial activity of an agricultural soil

Using TAM III multi-channel thermocalorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the two methods showed that growth rate constant (k), peak-heat output power (P _max) and the number of living microorganisms decreased with increasing concentration of Cd. Anncrease in Cd concentration resulted in the decrease of the peak-heat output power and increase in the time of the peak of power. However, the relationships between the thermokinetic parameters (k and P _max) and the number of microorganism were not linear, but the trend was similar. Our research also suggests that microcalorimetry is a very sensitive, simple and useful technique for in vitro investigation of the effects of toxic heavy metals on soil microbial activity.     

Cyclophosphamide, 2,2-dimethylaziridines and other alkylating agents as inhibitors of serum cholinesterase.

The effects of cyclophosphamide (CTX) and of alkylating agents containing aziridine or 2,2-dimethylaziridine moieties on the procaine esterase activity of horse serum cholinesterase were investigated. The results indicated that CTX is a competitive, reversible inhibitor of the enzyme, while all the other agents studied caused irreversible inhibition. However, there was no over-all correlation between the cholinesterase inhibitory activities of these agents and their alkylating reactivities toward the model nucleophile 4-(p-nitrobenzyl)pyridine (NBP). The kinetics of inhibition were consistent with the formation of a reversible enzyme alkylating agent complex prior to the irreversible inactivation of the enzyme. In the case of the ring-C-unsubstituted aziridines (TEM. TEPA and AB-100), the inactivation process could be described by the Main equation from which a dissociation constant (K_d) and a reaction rate constant (k₂)wcre calculated. The 2,2-dimethylaziridines(AB-132. AB-163 and TEPA-132) readily hydrolyzed. with rapid loss of alkylating activity (vs NBP). Simultaneously, the cholinesterase inhibitory activities of AB-132 and AB-163 significantly increased, reached a maximum and then gradually decreased on further hydrolysis; in contrast, TEPA-132 showed progressive loss of inhibitory activity. These results indicate that both AB-132 and AB-163 (but not TEPA-132) hydrolyze with the formation of an unstable intermediate(s) having little or no alkylating activity but acting as a potent, irreversible cholinesterase inhibitor(s).     

The Inhalation Hazard Test; principle and method

The Inhalation Hazard Test (IHT) measures the hazard rather than the toxicity of volatile substances. Generation methods for saturated vapor atmospheres and exposure systems are described. The determination of the nominal concentration gives in most cases sufficient information on the concentration in the inhalation atmosphere. The temperature at which the saturation occurs and the exposure time are parameters which influence the test results. The determination of the LT₀ (the exposure time at which no animals die) is used to compare substances with different inhalation hazards. A classification system is proposed to differentiate the toxic hazard of volatile substances. The IHT is an appropriate method to characterize the acute inhalation hazard of volatile substances. It requires fewer animals and is less elaborate than the LC₅₀.     

Trichloroethylene inhibits nitrogen transformation and microbial community structure in Mollisol

Trichloroethylene (TCE) is the most ubiquitous halogenated organic pollutant in the environment, it is one of the 129 priority control pollutants. In order to clarify the influence of TCE on microorganisms and nitrogen transformation in Mollisol is the core purpose of this study. Results showed that 10 mg kg⁻¹ TCE is the concentration limit of ammonification in Mollisol. When the concentration of TCE reached 10 mg kg⁻¹ and the effect lasted for over 7 days, the process of ammonia oxidation to nitric acid in Mollisol will be affected. TCE affected the process of nitrate (NO₃⁻) transformation into nitrite (NO₂⁻) by affecting the activity of nitrate reductase, thereby affected the denitrification process in soil. When the concentration of TCE is more than 10 mg kg⁻¹ it reduced the ability of soil microorganisms to obtain nitrogen, thereby affecting soil nitrogen transformation. RDA (Redundancy analysis) showed that the activity of nitrate reductase and the number of nitrifying bacteria and denitrifying bacteria in soil was negatively correlated with the incubation of TCE. In addition, soil nitrate reductase, nitrite reductase, peroxidase activity, ammonifying bacteria, nitrifying bacteria and denitrifying bacteria were negatively correlated with TCE concentration. Beyond that PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) of functional gene structure depend on KEGG (Kyoto Encyclopedia of Genes and Genomes) showed that 20 mg kg⁻¹ TCE significantly inhibited the metabolism of energy and other substances in Mollisol. Based on the above, it is found that TCE significantly affected nitrification and denitrification in Mollisol, thus the nitrogen transformation in Mollisol was affected by TCE contamination.

     

Using dextran of different molecular weights to achieve faster freeze-drying and improved storage stability of lactate dehydrogenase

Freeze-drying of protein formulations is frequently used to maintain protein activity during storage. The freeze-drying process usually requires long primary drying times because the highest acceptable drying temperature to obtain acceptable products is dependent on the glass transition temperature of the maximally freeze-concentrated solution (T_g′). On the other hand, retaining protein activity during storage is related to the glass transition temperature (T_g) of the final freeze-dried product. In this study, dextrans with different molecular weight (1 and 40?kDa) and mixtures thereof at the ratio 3:1, 1:1, and 1:3 (w/w) were used as cryo-/lyoprotectant and their impact on the stability of the model protein lactate dehydrogenase (LDH) was investigated at elevated temperatures (40?°C and 60?°C). The dextran formulations were then compared to formulations containing sucrose as cryo-/lyoprotectant. Because of the higher T_g′ values of the dextrans, the primary drying times could be reduced compared to freeze-drying with sucrose. Similarly, the higher T_g and T_g′ of dextrans relative to sucrose led to benefits during storage which was shown through improved protection of LDH activity.     

MODIFICATION OF LIPOXYGENASE BY HYDROGEN PEROXIDE AND PHOTOOXIDATION

The kinetic study of fluorescence stopped-flow method suggested that the interaction between lipoxygenase and H₂O₂ is consistent with a simple irreversible one-step mechanism. The activation energy of the reaction was 7.2 kcal/mol. Participation of an ionizable group with pK about 8.8, possibly a histidine residue, was suggested from the pH-dependence of the rate constant. No further fluorescence quenching of lipoxygenase was observed when the product was added to the lipoxygenase solution before mixing the lipoxygenase and H₂O₂ solutions. The fluorescence quenching of lipoxygenase by H₂O₂ was in parallel with the inactivation of the enzyme. Hydroperoxylinoleic acid strongly protects the inactivation of lipoxygenase caused by H₂O₂. These results are consistent with an interpretation that OH and/or O^- are produced when the iron of the enzyme is oxidized by H₂O₂, which in turn will attack some amino acid essential for the enzyme activity. The pH-dependence of the inactivation rate constant of photooxidation of lipoxygenase sensitized by methylene blue indicated that an ionizable group with pK about 8.8 is concerned with the enzymatic activity. In contrast to the inactivation of lipoxygenase by H₂O₂, the product protected the inactivation of the enzyme by photooxidation only at high concentration.     

Antioxidant properties of humic substances isolated from peloids

The antioxidant properties of humic substances of low-mineralization sulfidic muds (peloids) were investigated using initiated oxidation of 1,4-dioxane as a model reaction. Four groups of substances including humic, himatomelanic, fulvic, and humus acids were studied. Kinetic characteristics of the oxidation of humic substances were determined in terms of effective inhibition rate constants fk _In . It is established that himatomelanic acids of peloids exhibit the maximum antioxidant activity among the studied substances.     

Metabolic inhibition by transition metal ions in a slow-growing,toluene-enriched microbial population

We studied the effects of common first-row transition metal ions, Mn(II), Fe(III), Co(II), Cu(II), Zn(II), on the respiration of a mixed microbial population enriched for toluene degradation. Dissolved oxygen consumption, i.e., respiration rate, was used to measure metabolic activity of a slow-growing consortium of toluene-enriched microorganisms. Respiration rates decreased within 30 s of exposure to the metal ions and did not measurably recover during observation times (<80 min.). Metal ion toxicity increased with metal-phosphate binding affinities, consistent with cell damage by conformational changes in the phospholipid bilayer membrane to accommodate geometry requirements of complexes with transition metal ions. Changes in normalized metabolic activity (A_N) with aqueous composition were compared with an equilibrium free-ion toxicity mechanism relating the fraction of membrane phosphatic ligands affected by metal ion chemisorption to diminished metabolic activity. A_N measurements agreed with model predictions that the toxicity function (A_N⁻¹−1) is proportional to the free metal ion concentration when hydrogen ions do not compete with metal ions for the phosphatic membrane sites and proportional to the square root of the free metal ion concentration if hydrogen ions effectively compete with metal ions for membrane phosphate ligands. Transition metal ion uptake and toxicity were diminished by concentrations of competing Ca(II) and Mg(II) metal ion concentrations an order of magnitude larger than concentrations of transition metal ion. The Cu(II)-EDTA complex was nontoxic compared to Cu(II) ions. Metabolic inhibition produced by Cu(II) ions was not significantly reversed by sequestering Cu(II) ions using EDTA, suggesting that membrane damage is irreversible. Published 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 249–261, 1998