Acute toxicity of cresols, xylenols, and trimethylphenols to Daphnia magna Straus 1820

Twenty-four-hour IC50 values (50% immobilization concentration) for phenol, o-cresol, m-cresol, p-cresol, six xylenols, and three trimethylphenols were determined for Daphnia magna under static conditions. Our results show that cresols are more toxic than phenol, that xylenols do not exhibit significantly higher toxicity than cresols, and that trimethylphenols are less toxic than cresols. Thus, no direct relationship can be found between the number and position of methyl groups on the phenol nucleus and their acute toxicity to the water flea.     

Utilization of organic phosphates by selected bacteria and algae

Studies showed that synthetic phosphates of a surface active nature may become a source of carbon and energy for the Bacillus licheniformis. Bacillus mycoides, Bacillus cougulans and Azotobacter agilis bacteria in spite of the fact they are hardly oxidizable. In addition, it was found that these compounds may also become a source of phosphorus for the Scenedesmus obliquus alga which proves that these algae contain suitable phosphatases permitting utilization of a specific organic compound.     

Estimating the toxicities of organic chemicals to bioluminescent bacteria and activated sludge

Toxicity assays based on bioluminescent bacteria have several advantages including a quick response and an easily measured signal. The Shk1 assay is a procedure for wastewater toxicity testing based on the bioluminescent bacterium Shk1. Using the Shk1 assay, the toxicity of 98 organic chemicals were measured and EC50 values were obtained. Quantitative structure-activity relationship (QSAR) models based on the logarithm of the octanol-water partition coefficient (log(Kow)) were developed for individual groups of organic chemicals with different functional groups. The correlation coefficients for different groups of organic compounds varied between 0.69 and 0.99. An overall QSAR model without discriminating the functional groups, which can be used for a quick estimate of the toxicities of organic chemicals, was also developed and model predictions were compared to experimental data. The model accuracy was found to be one order of magnitude from the observed values.     

Measurement of the adsorption of C-Polyethyleneimine polymers during flocculation of silica, bacteria and algae

¹⁴C-Polyethyleneimine polymers of two different mol. wts have been prepared. These polymers have been used to study the flocculation of silica in water, of the bacterium E. coli in its nutrient and over a range of polymer concentration from about 1 to 1000 ppm. The degree of flocculation, and the amounts of polymer adsorbed on the colloid surface and the corresponding equilibrium concentration of polymer in solution have been measured. The concentration of polymer added to produce flocculation increased in the ratio from 1:30:500 in comparing silica. E. coli and C. ellipsoidia, respectively. However, the amount of polymer adsorbed on the same three colloids labelled with the tagged polymer, increased in the ratio 1:10:20 under comparable conditions. The higher concentrations needed to flocculate the two biocolloids cannot, therefore, be attributed to lack of adsorbed polymer on the surface. It is also true that much higher concentrations of polymer were needed on the surface to reverse the charge on the biocolloids compared with silica in order that flocculation might occur. The results are discussed briefly especially in relation to the need to explain flocculation phenomena in terms of the surface areas of the colloids and surface coverage by the polymers. Experimental results are reported which indicate that interaction of PEI polymers with anions in the algal and E. coli nutrients, and with biopolymers formed in the growth of the latter are important in affecting flocculation.     

Correlating toxicities of organic compounds to select protozoa using the Abraham model

The Abraham solvation parameter model is used to construct mathematical correlations for describing the nonspecific toxicity of organic compounds to three protozoas (Entosiphon sulcantum, Uronema parduczi and Chilomonas paramecium). The derived mathematical correlations describe the observed published toxicity data to within an overall average standard deviation of approximately 0.35 log units. The correlations can be used to estimate aquatic toxicities of organic chemicals to the three aquatic organisms studied, and to help in identifying compounds whose toxic mode of action might involve chemical specific reactivity, rather than nonpolar or polar narcosis. A principal component analysis of the correlation equations found in this work shows that no water-solvent system we have investigated is a good model for nonspecific aquatic toxicity towards the three protozoas. Furthermore, correlation equations for nonspecific aqueous toxicity towards various biological systems, that we have found in this work and in previous studies, cover such a wide range that no single water-solvent system could ever be a good model for all the biological systems.     

Comparison of the toxicity thresholds of water pollutants to bacteria, algae, and protozoa in the cell multiplication inhibition test

Using analogous methods of the cell multiplication inhibition test, the toxicity threshold (TT) of 156 potential water pollutants was determined for model organisms of biological self-purification, i.e. bacteria of the species Pseudomonas putida, green algae of the species Scenedesmus quadricauda, and flagellate protozoa of the species Entosiphon sulcatum. From the number of 156 inorganic and organic pollutants tested, 23 exhibited a pronounced selective toxic action on bacteria of the species Pseudomonas putida, 47 on algae of the species Scenedesmus quadricauda, and 43 on flagellate protozoa of the species Entosiphon sulcatum. It is seen from the ratios found that a determination of the toxicity threshold of potential water pollutants for these three model organisms from the microbiological spectrum would provide a broader basis for assessing the damaging action of water pollutants to model organisms active in the biological self-purification of water. Ecotoxicological testing of potential water pollutants to evaluate their toxicity involving only one model organism of biological self-purification would give an incomplete and biased picture of the effects of pollutants.     

The effectiveness of five natural products against three species of harmful algae

The effects of five natural products on the growth of three harmful algae species including Chattonella marina Hara et Chihara, Alexandrium tamarense Balech and Karenia mikimotoi (Miyake & Kominami ex Oda) G. Hansen & Ø. Moestrup were observed. Four products including ε‐polylysine, betaine, stachydrine and berberine exhibited selectively inhibitory effects against the three algae. However, the other product chitosan had no obvious inhibition against the above algae. Berberine and ε‐polylysine exhibited relatively higher inhibitory capability against C. marina, and betaine had the highest inhibitory effect against A. tamarense. While only berberine could effectively inhibit the growth of K. mikimotoi with LC_{50, 120} at 3.1 mg/L. The fast inhibitory effect against K. mikimotoi and environmental safety of berberine suggested that it might be a potential algaecide against K. mikimotoi.     

Comparison of the equilibrium sorption of five organic compounds to HDPE, PP, and PVC geomembranes

This experimental investigation quantified the sorption uptake of five commonly encountered organic groundwater contaminants, methyl tertiary-butyl-ether (MTBE), benzene, trichloroethylene (TCE), 1,2-dichorobenzene (1,2-DCB), and trinitrotoluene (TNT), to geomembranes made from high density polyethylene (HDPE), polypropylene (PP), and polyvinylchloride (PVC). The organic compounds were chosen to span a range of aqueous solubilities and chemical properties. The geomembranes tested in this study exhibited sorption capacities that were of similar magnitude for each of the contaminants tested, with the exception of 1,2-DCB to HDPE, which exhibited strong uptake in comparison to the other solute/sorbent combinations. In general, the PVC geomembrane demonstrated the highest sorption capacities, while the HDPE geomembrane demonstrated the lowest sorption capacities. Measured partitioning coefficients for the contaminant/geomembrane combinations ranged from S_gf<1 to 160, but most commonly had values between 10 and 75.     

Measurement of the adsorption of 14C-Polyethyleneimine polymers during flocculation of silica,bacteria and algae

¹⁴C-Polyethyleneimine polymers of two different mol. wts have been prepared. These polymers have been used to study the flocculation of silica in water, of the bacterium E. coli in its nutrient and over a range of polymer concentration from about 1 to 1000 ppm. The degree of flocculation, and the amounts of polymer adsorbed on the colloid surface and the corresponding equilibrium concentration of polymer in solution have been measured. The concentration of polymer added to produce flocculation increased in the ratio from 1:30:500 in comparing silica. E. coli and C. ellipsoidia, respectively. However, the amount of polymer adsorbed on the same three colloids labelled with the tagged polymer, increased in the ratio 1:10:20 under comparable conditions. The higher concentrations needed to flocculate the two biocolloids cannot, therefore, be attributed to lack of adsorbed polymer on the surface. It is also true that much higher concentrations of polymer were needed on the surface to reverse the charge on the biocolloids compared with silica in order that flocculation might occur. The results are discussed briefly especially in relation to the need to explain flocculation phenomena in terms of the surface areas of the colloids and surface coverage by the polymers. Experimental results are reported which indicate that interaction of PEI polymers with anions in the algal and E. coli nutrients, and with biopolymers formed in the growth of the latter are important in affecting flocculation.     

Effects of substrate concentrations on the growth of heterotrophic bacteria and algae in secondary facultative ponds

This paper presents the effect of substrate concentration on the growth of a mixed culture of algae and heterotrophic bacteria in secondary facultative ponds (SFPs) utilizing settled domestic sewage as a sole source of organic carbon. The growth of the mixed culture was studied at the concentrations ranging between 200 and 800 mg COD/l in a series of batch chemostat reactors. From the laboratory data, the specific growth rate (micro) was determined using the modified Gompertz model. The maximum specific growth rate ( micro(max)) and half saturation coefficients (K(s)) were calculated using the Monod kinetic equation. The maximum observed growth rate ( micro(max)) for heterotrophic bacteria was 3.8 day(-1) with K(s) of 200 mg COD/l. The micro(max) for algal biomass based on suspended volatile solids was 2.7 day(-1) with K(s) of 110 mg COD/l. The micro(max) of algae based on the chlorophyll-a was 3.5 day(-1) at K(s) of 50mg COD/l. The observed specific substrate removal by heterotrophic bacteria varied between the concentrations of substrate used and the average value was 0.82 (mg COD/mg biomass). The specific substrate utilization rate in the bioreactors was direct proportional to the specific growth rate. Hence, the determined Monod kinetic parameters are useful for the definition of the operation of SFPs.     

Indoor molds, bacteria, microbial volatile organic compounds and plasticizers in schools--associations with asthma and respiratory symptoms in pupils

We investigated asthma and atopy in relation to microbial and plasticizer exposure. Pupils in eight primary schools in Uppsala (Sweden) answered a questionnaire, 1014 (68%) participated. Totally, 7.7% reported doctor-diagnosed asthma, 5.9% current asthma, and 12.2% allergy to pollen/pets. Wheeze was reported by 7.8%, 4.5% reported daytime breathlessness, and 2.0% nocturnal breathlessness. Measurements were performed in 23 classrooms (May-June), 74% had <1000 ppm CO(2) indoors. None had visible mold growth or dampness. Mean total microbial volatile organic compound (MVOC) concentration was 423 ng/m(3) indoors and 123 ng/m(3) outdoors. Indoor concentration of TMPD-MIB (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Texanol) and TMPD-DIB (2,2,4-trimethyl-1,3-pentanediol diisobutyrate, TXIB), two common plasticizers, were 0.89 and 1.64 microg/m(3), respectively. MVOC and plasticizer concentration were correlated (r = 0.5; P < 0.01). Mold concentration was 360 cfu/m(3) indoors and 980 cfu/m(3) outdoors. At higher indoor concentrations of total MVOC, nocturnal breathlessness (P < 0.01) and doctor-diagnosed asthma (P < 0.05) were more common. Moreover, there were positive associations between nocturnal breathlessness and 3-methylfuran (P < 0.01), 3-methyl-1-butanol (P < 0.05), dimethyldisulfide (P < 0.01), 2-heptanone (P < 0.01), 1-octen-3-ol (P < 0.05), 3-octanone (P < 0.05), TMPD-MIB (P < 0.05), and TMPD-DIB (P < 0.01). TMPD-DIB was positively associated with wheeze (P < 0.05), daytime breathlessness (P < 0.05), doctor-diagnosed asthma (P < 0.05), and current asthma (P < 0.05). In conclusion, exposure to MVOC and plasticizers at school may be a risk factor for asthmatic symptoms in children. PRACTICAL IMPLICATIONS: Despite generally good ventilation and lack of visible signs of mold growth, we found an association between respiratory symptoms and indoor MVOC concentration. In addition, we found associations between asthmatic symptoms and two common plasticizers. The highest levels of MVOC, TMPD-MIB, and TMPD-DIB were found in two new buildings, suggesting that material emissions should be better controlled. As MVOC and plasticizers concentrations were positively correlated, while indoor viable molds and bacteria were negatively correlated, it is unclear if indoor MVOC is an indicator of microbial exposure. Further studies focusing on health effects of chemical emissions from indoor plastic materials, including PVC-floor coatings, are needed.     

Assessing toxicities of industrial effluents and 1,4‐dioxane using sulphur‐oxidising bacteria in a batch test

In this study, the qualities of the final effluents from nine different industries (A, B, C, D, E, F, G, H and I) discharging 1,4‐dioxane mainly as effluents were assessed using sulphur‐oxidising bacteria (SOB) as a test micro‐organism in batch mode. Results showed that effluent from industry ‘B’ was the most toxic of all the effluents tested, followed by E, C and A effluents. An EC₅₀ value of 13% was obtained for effluent from B, whereas with E, C and A effluents, the EC₅₀ values of 23%, 25% and 29% were found, respectively. Similarly, batch tests were performed in order to evaluate the potential for 1,4‐dioxane to inhibit growth on SOB. The lowest test concentration of 1,4‐dioxane (12 μg/L) resulted in 17% of inhibition of SOB, whereas the highest test concentration (3.125 mg/L) resulted in > 75% of the inhibition. An EC₅₀ value of 0.105 mg/L was obtained for 1,4‐dioxane.     

Release of antibiotic resistant bacteria and genes in the effluent and biosolids of five wastewater utilities in Michigan

The purpose of this study was to quantify the occurrence and release of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) into the environment through the effluent and biosolids of different wastewater treatment utilities including an MBR (Membrane Biological Reactor) utility, conventional utilities (Activated Sludge, Oxidative Ditch and Rotatory Biological Contactors-RBCs) and multiple sludge treatment processes (Dewatering, Gravity Thickening, Anaerobic Digestion and Lime Stabilization). Samples of raw wastewater, pre- and post-disinfected effluents, and biosolids were monitored for tetracycline resistant genes (tetW and tetO) and sulfonamide resistant gene (Sul-I) and tetracycline and sulfonamide resistant bacteria. ARGs and ARB concentrations in the final effluent were found to be in the range of ND(non-detectable)-2.33 × 10⁶ copies/100 mL and 5.00 × 10²-6.10 × 10⁵ CFU/100 mL respectively. Concentrations of ARGs (tetW and tetO) and 16s rRNA gene in the MBR effluent were observed to be 1-3 log less, compared to conventional treatment utilities. Significantly higher removals of ARGs and ARB were observed in the MBR facility (range of removal: 2.57-7.06 logs) compared to that in conventional treatment plants (range of removal: 2.37-4.56 logs) (p < 0.05). Disinfection (Chlorination and UV) processes did not contribute in significant reduction of ARGs and ARB (p > 0.05). In biosolids, ARGs and ARB concentrations were found to be in the range of 5.61 × 10⁶-4.32 × 10⁹ copies/g and 3.17 × 10⁴-1.85 × 10⁹ CFU/g, respectively. Significant differences (p < 0.05) were observed in concentrations of ARGs (except tetW) and ARB between the advanced biosolid treatment methods (i.e., anaerobic digestion and lime stabilization) and the conventional dewatering and gravity thickening methods.     

Flammability limits of five selected compounds each mixed with HFC-125

Flammability limits of five selected combustible gases each mixed with 1,1,1,2,2-pentafluoroethane (HFC-125) were investigated. Actually, the investigation was made for methane, propane, propylene, methyl formate, and 1,1-difluoroethane (HFC-152a). The observed data were analyzed using the extended Le Chatelier's formula. As a result, the HFC-125 mixing effect on the flammability limits of individual gases was found to be adequately interpreted using the extended Le Chatelier's formula. However, contrary to the cases of nitrogen and carbon dioxide dilutions, it was not possible to appropriately interpret the HFC-125 mixing effects on all five gases simultaneously using a common set of parameter values. This fact suggests that the reaction of HFC-125 in flame is different if the coexisting fuel is different.     

Adverse effects of organic arsenical compounds towards Vibrio fischeri bacteria

The most frequently encountered forms of organic arsenic, namely, dimethylarsinic acid, monomethylarsonic acid, arsenobetaine, arsenocholine and Roxarsone (4-hydroxy-3-nitrobenzene arsonic acid) were tested for toxicity either by using the Microtox bioassay, based on the rapid (within 15 min) fading of luminescence emitted by Vibrio fischeri marine bacteria, or by monitoring growth rate of the same bacteria for 3 days. Organic arsenic was generally found to be less toxic to these biological models than inorganic arsenic. In many cases, EC50 values for DMA, MMA or HNAA when using luminescence or growth inhibition assays could not be determined because of the low toxicity of the compounds. Nevertheless, results from the luminescence inhibition assay, which was found to be more sensitive than the growth inhibition assay, allowed to rank toxicity as follows: arsenate at pH 8>HNAA at pH 5>arsenate at pH 5>MMA at pH 5>HNAA at pH 8>DMA at pH 5. Arsenobetaine and monomethylarsonic acid were unexpectedly found to stimulate bacterial growth (hormesis effect). pH was found to have a strong influence on the observed toxicity as a consequence of the pH-induced changes in the chemical speciation of the tested molecules. In most cases it appeared that negatively charged forms were less toxic than the uncharged ones.     

Acute toxicity tests with Daphnia magna straus and Pimephales promelas rafinesque in support of national pollutant discharge elimination permit requirements

The purpose of this study was to determine the static acute toxicity of aniline, p-chloro-m-cresol and 2(2,4,5-trichlorophenoxy) propionic acid (silvex) to daphnids (Daphnia magna) and bis(2-chloroethoxy)methane and 2-sec-butyl-4,6-dinitrophenol (dinoseb) to both daphnids and fathead minnows (Pimephales promelas). These data were needed to fulfill requirements established in the NPDES Permit (National Pollutant Discharge Elimination System) issued to the Michigan Division of The Dow Chemical Co. (Midland, Mich., U.S.A.) by the State of Michigan. Where appropriate, water quality-based effluent limitations could be recommended based on the acute toxicity data generated during this study. The results of the acute toxicity tests indicated that bis(2-chloroethoxy)methane was practically non-toxic to both daphnids and fathead minnows (LC₅₀ values of 201 and 184 mg l⁻¹, respectively); additionally, silvex was also found to be practically non-toxic to daphnids (LC₅₀ value > 140 mg l⁻¹). Aniline was highly toxic and p-chloro-m-cresol moderately toxic to daphnids, with calculated LC₅₀ values of 0.17 and 2.0 mg l⁻¹, respectively. Dinoseb was highly toxic both to daphnids and fathead minnows, with reported LC₅₀ values of 0.24 and 0.17 mg l⁻¹, respectively.     

Diterpenes of marine brown algae of the family Dictyotaceae: their possible role as defense compounds and their use in chemotaxonomy

Marine brown algae of the family Dictyotaceae are protected against predation. Their survival strategy is, at least in part, based on the production of chemical defenses. These compounds are diterpenes that seem to establish a specific predator-prey relationship, and which are found as food-chain markers. The use of Dictyotaceae diterpenes in chemotaxonomy is briefly discussed.     

The acute toxicity of pulse-dosed, para-substituted phenols to larval American flagfish (Jordanella floridae): a comparison with toxicity to photoluminescent bacteria and predicted toxicity using log Kow

The acute toxicity of nine para-substituted phenols was determined using a pulse-exposure testing protocol and 8-day-old larval American flagfish (Jordanella floridae). Relative tolerance was assessed by determining the 2-h pulse exposure concentration causing 20 and 50% mortality (PE LC20 and PE LC50) over the subsequent 94 h. Four bioassays were run for each phenol and yielded the following mean PE LC20 values (mg 1(-1)) in descending order of toxicity: p-aminophenol, 0.06; hydroquinone, 0.13; phenol, 0.70; p-nitrophenol, 0.81; p-cyanophenol, 3.0; p-chlorophenol, 3.3; p-hydroxyacetophenone, 4.2; p-hydroxybenzyl alcohol, 6.4; and p-hydroxybenzoic acid, 170. These toxicities did not correlate significantly with either previously reported toxicity values for the photoluminescent bacteria Photobacterium phosphoreum, or with the log octanol-water partition coefficient. For some of the compounds, however, sensitivities were quite close to previously reported rainbow trout chronic no-observed-effect concentrations based on continuous exposure. Caution is urged with respect to applying "low-level" biota techniques or simple quantitative structure-activity correlations such as Kow when attempting to predict the toxicity of specific chemicals to fish.     

The relative importance of Lemna gibba L., bacteria and algae for the nitrogen and phosphorus removal in duckweed-covered domestic wastewater

To arrive at detailed nutrient balances for duckweed-covered wastewater treatment systems, five laboratory-scale experiments were carried out in shallow (3.3 cm), 1 l batch systems to assess separately the contributions of duckweed itself, attached and suspended bacteria as well as algae to N- and P-removal in domestic wastewater. Depending on the initial concentrations, our duckweed-covered systems removed 120–590 mg N m⁻² d⁻¹ (73–97% of the initial Kjeldahl-nitrogen) and 14–74 mg P m⁻² d⁻¹ (63–99% of the initial total phosphorus) in 3 days. Duckweed (Lemna gibba L.) itself was directly responsible for 30–47% of the total N-loss by uptake of ammonium and, probably dependent on the initial P-concentrations, for up to 52% of the total P-loss. The indirect contribution of duckweed to the total nutrient removal was also considerable and included the uptake (and adsorption) of ammonium and ortho-phosphate by algae and bacteria in the attached biofilm and the removal of N through nitrification/denitrification by bacteria attached to the duckweed. Together these accounted for 35–46 and 31–71% of the total N- and P-loss, respectively. Therefore, approximately of the total N- and P-loss could be attributed to the duckweed mat. The remaining quarter is due to non-duckweed related components: uptake and nitrification/denitrification by algae and bacteria attached to the walls and the sediment of the system (including sedimentation). Other processes, like NH₃-volatilisation, N-fixation and nutrient uptake as well as nitrification/denitrification by suspended microorganisms did not influence the N- and P-balance of our systems, but could become important with increasing water depths and retention times.     

Bioaccumulation of zinc in two freshwater organisms (Daphnia magna,crustacea and Brachydanio,rerio, pisces)

Daphnia magna and Brachydanio rerio are important test organisms in toxicity tests. The bioaccumulation of zinc in these species was investigated in two semistatic experiments in synthetic freshwater with a zinc concentration of 250 μg 1⁻¹. Fishes were fed with polluted or unpolluted Daphnia magna to determine the significance of zinc accumulation from contaminated natural food.Daphnia magna accumulates zinc to a high extent within days. Uptake from food particles substantially contributes to the zinc accumulation in filter-feeding Daphnia; their zinc content strongly depends on the total but not on the dissolved zinc concentration in water.Zinc concentration of Brachydanio rerio increases only to a small extent during the 5 weeks accumulation time. They accumulate no additional zinc from the food source. In unpolluted and polluted Brachydanio a significant negative correlation exists between whole body zinc concentration and body dry weight.