bluuebunny/crossref_metadata_2025 huggingface dataset:
Property-toxicity relationships of azaarenes to the green alga Scenedesmus acuminatus
Authors: Van Vlaardingen Peter L. A. , Steinhoff Wilco J. , Admiraal Wim A. , De Voogt Pim
Published: March 2010

The toxicity of three two-ring and five three-ring azaarenes to the green alga Scenedesmus acuminatus and its relationship with molecular structure was investigated. Indole, quinoline, isoquinoline, and carbazole did not inhibit the growth rate of S. acuminatus in 96-h batch culture assays up to 10 mg/L. Chlorophyll-α content appeared to be a more sensitive response parameter than growth for five of six compounds. This parameter showed a relationship with hydrophobicity-related molecular descriptors like molecular surface area. Four benzoquinoline isomers showed notably different effects on growth rate and chlorophyll-α content. Median effect concentration (EC50) values obtained for growth rate were acridine, 0.32 mg/L; benzo[f]quinoline, 1.55 mg/L; phenanthridine, 5.24 mg/L; and benzo[h]quinoline, 6.65 mg/L. Similar differences existed in their EC50 values for chlorophyll-α content. The differences in toxicity between these isomers correlates with two electronical molecular descriptors, viz. the ionization potential and the homo—lumo gap. Several modes of action are put forward and their relative importance discussed.
Accumulation and biotransformation of tri-N-butyltin by isolated rainbow trout hepatocytes
Authors: Reader Stephanie , Louis Richard Saint , Pelletier ÉMilien , Denizeau Francine
Published: March 2010

In the present study, metabolism of tributyltin (TBT) by isolated trout hepatocytes was investigated over a short exposure time. For this, the cells were exposed to TBT, and the determination of TBT and possible metabolites was performed. Cell viability and cytochrome P-450 activity were also measured. After 15 min of exposure to 1 μM TBT, 72 ± 23% of the total tin recovery was observed in the cellular fraction, and about 3 and 4% of the total amount of tin was recovered as dibutyltin (DBT) in the cells and incubation medium, respectively. The amount of DBT leveled off after 15 min, probably because of the inhibition of cytochrome P-450. Thus, TBT is metabolized by fish hepatocytes. However, as it also inhibits cytochrome P-450 activity, it has the potential to alter its own metabolism and that of other environmental pollutants.
Predicting chronic toxicity of sediments spiked with zinc: An evaluation of the acid-volatile sulfide model using a life-cycle test with the midgeChironomus tentans
Authors: Sibley Paul K. , Ankley Gerald T. , Cotter Anne M. , Leonard Edward N.
Published: March 2010

The development of sediment quality criteria for the cationic metals cadmium, copper, lead, nickel, and zinc has focused on the use of acid-volatile sulfide (AVS) as the primary normalization phase for predicting interstitial pore-water concentrations and bioavailability of the metals. To date, most of the research in support of AVS in this context has utilized short-term laboratory exposures, with a relative paucity of information pertaining to long-term exposures. The purpose of this study, therefore, was to investigate the use of AVS as a predictor of metal toxicity to a benthic organism in a long-term laboratory exposure. Clean sediment was spiked with zinc to obtain nominal treatments ranging from −2.34 to 58.5 μg/g dry weight with respect to the molar difference between simultaneously extracted metal (SEM) and AVS. The test was initiated with newly hatched larvae of the midge Chironomus tentans and carried through one complete generation (56 d) during which survival, growth, emergence, and reproduction were monitored. When the molar difference between SEM and AVS (i.e., SEM – AVS) was <0, the concentration of zinc in the sediment interstitial water was low and no adverse effects were observed for any of the biological endpoints measured. Conversely, when SEM – AVS exceeded 0, a dose-dependent increase in the relative concentration of zinc in the pore water was detected. However, the absolute concentration of pore-water zinc at each treatment declined over the course of the study, corresponding to an increase in sediment AVS and to a loss of zinc due to diffusion into the overlying water, which was renewed twice daily. Only when SEM – AVS exceeded 0 were significant reductions in survival, growth, emergence, and reproduction observed. Together, the chemical and biological data from this study compare favorably with observations made in short-term exposures and thus support the use of AVS as a normalization phase for predicting toxicity in metal-contaminated sediments.
Chronic effect of cadmium in sediments on colonization by benthic marine organisms: An evaluation of the role of interstitial cadmium and acid-volatile sulfide in biological availability
Authors: Hansen David J. , Mahony John D. , Berry Walter J. , Benyi Sandra J. , Corbin Jeffrey M. , Pratt Sheldon D. , Di Toro Dominic M. , Abel Mary Beth
Published: March 2010

The role of interstitial cadmium and acid-volatile sulfide (AVS) in controlling the bioavailability of sediment-associated metal was examined using the chronic saltwater benthic colonization test. Sediments were spiked to achieve nominal cadmium/ AVS molar ratios of 0.0 (control), 0.1, 0.8, and 3.0 in this 118-d test. Oxidation of AVS in the surficial 2.4 cm within 2 to 4 weeks resulted in sulfide profiles similar to those occurring naturally in local sediments. In the nominal 0.1 cadmium/AVS treatment, measured simultaneously extracted metal (SEMcd) was always less than AVS. Interstitial cadmium concentrations (<3-10 μg/L) were less than those likely to cause biological effects. No significant biological effects were detected. In the nominal 0.8 cadmium/ AVS treatment, measured SEMcd commonly exceeded AVS in the surficial 2.4 cm of sediment. Interstitial cadmium concentrations (24-157 μg/L) were of likely toxicological significance to highly sensitive species. Shifts in the presence or absence over all taxa, and fewer macrobenthic polychaetes (Mediomastus ambiseta, Streblospio benedicti, and Podarke obscurd) and unidentified meio-faunal nematodes, were observed. In the nominal 3.0 cadmium/AVS treatment, concentrations of SEMcd were always greater than AVS throughout the sediment column. Interstitial cadmium ranged from 28,000 to 174,000 μg/L. In addition to the effects above, these sediments were colonized by fewer macrobenthic species, polychaete species, and harpacticoids; had lower densities of diatoms; lacked bivalve molluscs; and exhibited other impacts. Over all treatments, the observed biological responses were consistent with SEMcd/AVS ratios in surficial sediments and interstitial water cadmium concentrations.
Effect of bioturbation on metal-sulfide oxidation in surficial freshwater sediments
Authors: Peterson Gregory S. , Ankley Gerald T. , Leonard Edward N.
Published: March 2010

Recent studies have demonstrated the role of acid-volatile sulfide (AVS) in controlling the bioavailability of several cationic metals in anoxic sediments. However, metal-sulfide complexes can be relatively labile with respect to oxidation associated with factors such as seasonal changes in rates of oxidation/production of AVS. Another potentially important mechanism of AVS oxidation in surficial sediments is bioturbation. We used different densities of the burrowing oligochaete Lumbriculus variegatus in a series of laboratory experiments to evaluate the effect of bioturbation on oxidation of AVS and subsequent bioavailability of cadmium and zinc spiked into freshwater sediments. Metal bioavailability was determined directly by bioaccumulation in the test organisms and indirectly through analysis of interstitial (pore) water metal concentrations. In our studies, horizon-specific sediment analyses were conducted to assess spatial differences in AVS and pore-water metal concentrations specifically related to organism activity. Burrowing activity of the oligochaete significantly reduced AVS concentrations in surficial sediments in a density-dependent manner and resulted in elevated interstitial water concentrations of cadmium but not zinc. Concentrations of cadmium in pore water from deeper horizons (below the zone of active burrowing) were consistently lower than those in the surficial sediments. The bioaccumulation of cadmium and zinc by L. variegatus was reflective of pore-water concentrations of the two metals, i.e., there was significant accumulation of cadmium, but not zinc, by the oligochaetes. Overall, our results indicate that bioturbation can enhance the bioavailability of some cationic metals in surficial sediments, via oxidation of AVS, and demonstrate the importance of analyzing surficial sediments when assessing bioavailability of metals in sediments.
Particle oxidation model of synthetic FeS and sediment acid-volatile sulfide
Authors: Di Toro Dominic M. , Mahony John D. , Gonzalez Adrian M.
Published: March 2010

A model is proposed for the kinetics of the oxidation of acid-volatile sulfide (AVS). It is based on a surface oxidation reaction that erodes the particle surface until the particle disappears. A monodisperse particle size distribution is assumed with a reaction rate that is proportional to the surface area remaining and a dimensional exponent that relates the surface area to the particle volume. The model is fit to time course data from a number of experiments conducted using synthetic FeS at various pHs, oxygen concentrations, and ionic strengths. The reaction rate constants are modeled using a surface complexation model. It is based upon the formation of two activated surface complexes with molecular oxygen, one of which is charged. The complexation model provides a good fit to the variation of the reaction rate constant with respect to O2, pH, temperature, and ionic strength. The dimensional exponent v increases with pH from values characteristic of plates and needles to values reflecting more spherical particles, presumably due to coagulation. However the increase in v with respect to O2 at high concentrations is unexplained.
A laboratory-formulated sediment incorporating synthetic acid-volatile sulfide
Authors: Gonzalez Adrian M.
Published: March 2010

The application of laboratory-formulated sediment (LFS) could be expanded if toxicologically significant characteristics of sediment other than particle-size distribution, organic carbon content, and pH could be manipulated. This report describes the preparation of a LFS containing synthetic acid-volatile sulfide (AVS) and shows its similarity to natural sediment AVS. Several formulations were evaluated with respect to toxicity to Hyalella azteca and chemical stability. Amphipod survival was highest (95%) in LFS formulations in which the molar iron(II)/sulfide ratio was near 1, although amphipod survival was >l80% in six of seven formulations with ≤20% excess metal or sulfide. Synthetic AVS in the test system oxidized rapidly at the sediment surface, but AVS at depth was stable for >30 d when isolated from air or aerated water. Oxidation-reduction potential measurements and AVS analysis of core slices revealed a vertical oxidation profile, apparently established and limited by oxygen diffusion. A formulation consisting of a 1:1 molar ratio of iron and sulfide (FeS) was evaluated with respect to complexation of copper, zinc, and nickel and to the corresponding reduction in toxicity using W-AH. azteca toxicity tests. Amphipod mortality in metal-spiked LFS with metal/AVS molar ratios >1 was high relative to controls. In contrast, amphipod survival in metal-spiked LFS with metal/AVS molar ratios >1 was generally similar to amphipod survival in nonspiked LFS containing synthetic AVS. A few exceptions, where toxicity was noted when metal/AVS ratios were <1, could be explained by high concentrations of dissolved iron, which was released by the metal + AVS displacement reaction. The LFS containing synthetic AVS appears to mimic natural sediment AVS and thus can provide consistent and controlled substrates suitable for investigating metal/sediment chemistry and toxicity and for developing realistic sediment quality criteria for metals.
Choosing a cosolvent: Solubilization of naphthalene and cosolvent property
Authors: Li An , Yalkowsky Samuel H. , Andren Anders W.
Published: March 2010

The addition of an organic cosolvent to water can increase the aqueous solubility of many hydrophobic organic compounds (HOCs). This work examines the correlations between the change of naphthalene solubility and various physicochemical properties of the cosolvent added to the system. Results show that the dielectric constant and surface tension do not correlate with the solubilization power of cosolvent toward naphthalene. The solubility parameter correlates well with increases in naphthalene solubility and therefore provides a convenient tool when screening cosolvents for their ability to enhance HOC solubility in various environmental engineering applications. Other properties investigated include the octanol/water partition coefficient, interfacial tension, ET(30), viscosity, and hydrogen bonding capacities.
The effect of enzyme treatment on untreated d-stage effluent: Short-term fish early life-stage toxicity test
Authors: Jacobsen Frank , Folke Jens
Published: March 2010

Short-term early-life-stage toxicity experiments were conducted using zebra fish (Brachydanio rerio) under semistatic conditions. The test parameters studied were percent hatching success, median time from fertilization to hatching, median survival of embryos and larvae, frequency of abnormal larvae, as well as larval growth. Test organisms were exposed to a sample of raw spent bleach liquor from the D-stage of a softwood bleached-kraft pulp mill and the sample after treatment with a peroxidase enzyme, which resulted in a 50% decrease in residual phenolic components (0.123 vs. 0.061mg/L). In the untreated D-stage sample, the median survival of embryos and larvae was calculated to be 151 ml/L; the lowest-observed-effect concentration was 50 ml/L, and the no-observed-effect concentration was 25ml/L. No dose response could be established for fish exposed to peroxidase-treated D-stage liquor; the treated effluent was only minimally toxic in this short-term test.
C-18-coated silica particles as a surrogate for benthic uptake of hydrophobic compounds from bedded sediment
Authors: Lake James L. , Osterman Frank A. , McKinney Richard , Lake Carol A.
Published: March 2010

To simulate the bioaccumulation of neutral organic contaminants by infaunal benthos, the partitioning of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) between a contaminated estuarine sediment and admixed C-18-coated silica particles was measured. The concentrations of lower chlorinated PCB congeners (less than five chlorine atoms per molecule) on the C-18-coated silica particles reached apparent steady state within 300 h while congeners with greater numbers of chlorine atoms required much greater time periods (greater than 1 year) to reach apparent steady state. Polycyclic aromatic hydrocarbons showed less partitioning from sediment to the C-18 particles than PCB congeners, although the log Kow ranges of the compounds in these comparisons were similar. The biota sediment accumulation factors, defined as the lipid-normalized contaminant concentration in an exposed organism divided by the organic carbon-normalized contaminant concentration of the sediment, were calculated for these exposures using the C-18 of the particles as the lipid. The results from these exposures agreed closely with those measured in studies where living benthic organisms were exposed to contaminated sediment.
Biodegradation of thiophene, benzothiophene, and benzofuran with eight different primary substrates
Authors: Dyreborg Søren , Arvin Erik , Broholm Kim , Christensen Jens
Published: March 2010

The aerobic biodegradation of thiophene, benzothiophene, and benzofuran was studied in microcosm experiments using groundwater microorganisms as inoculum. Benzofuran, a heterocyclic aromatic compound containing oxygen, was biodegraded as a sole source of carbon and energy measured by the disappearance of the compound, whereas two heterocyclic aromatic compounds containing sulphur (thiophene and benzothiophene) were not used as growth substrates. Thiophene was biodegraded with benzene, toluene, and to some extent ethylbenzene as primary substrates. Some biodegradation of thiophene was observed when p-xylene, o-xylene, m-xylene, naphthalene, and 1-methylnaphthalene were the primary substrates. Benzothiophene was completely transformed, with all eight primary substrates investigated except for benzene and p-xylene, in which 34 and 6% of benzothiophene, respectively, remained after 40 d of incubation. Although benzofuran could be used as a sole source of carbon and energy, data showed that the biodegradation of benzofuran definitely was enhanced by the biodegradation of the primary substrates used.
Ecotoxicology and pesticides in tropical aquatic ecosystems of Central America
Authors: Castillo Luisa E , de la Cruz Elba , Ruepert Clemens
Published: March 2010

Although pesticide use is high in the Central American region, few studies concerning environmental levels and effects of pesticides in aquatic ecosystems have been conducted. In this review 18 studies were identified, most of which deal exclusively with organochlorine residues, but other chemical groups also were studied and found in tropical aquatic ecosystems. Only five studies considered effects of pesticides on aquatic organisms; four of these examined both the presence of pesticides in environmental substrates and field effects. Major research needs include studies on fate and degradation in tropical conditions; acute and chronic toxicity to native species; effects of temperature, humidity, and other characteristics of tropical conditions on toxicity, as well as effects of pesticides on tropical ecosystems.
Sediment contamination problems in the Caribbean islands: Research and regulation
Authors: Ross Philippe , DeLorenzo Marie E
Published: March 2010

Sediment contamination in the Caribbean has not been extensively studied. This review article outlines known cases of sediment contamination in the Caribbean and their impacts on Caribbean ecosystems. It also discusses regulation and remediation of contaminated sediments in the Caribbean and speculates on what the future holds regarding sediment toxicity. Existing information suggests that sediment contamination may be widespread, although not severe in most areas. Puerto Rico and the U.S. Virgin Islands contain two National Priority List sites and one candidate site under U.S. Superfund jurisdiction. These territories will be more extensively studied under the U.S. Environmental Monitoring and Assessment Program. Regulation of sediment contamination is difficult within the Caribbean region because jurisdiction is shared by 27 independent countries and a number of territories and dependencies. In addition to establishing control of natural resources within a 200–mile offshore limit for each Caribbean nation, the recently created Exclusive Economic Zone contains provisions for environmental protection and management, but many governments in the region lack the resources to implement them. The Caribbean Action Plan formalizes international cooperation and assistance to overcome some of these limitations. Many Caribbean countries have experienced a strong industrial expansion and a rapid population growth during the last 30 to 40 years, and there is potential for further contamination as these islands develop.
Ecotoxicology of pesticides in the tropical paddy field ecosystem
Authors: Abdullah Abdul R , Bajet Cristina M , Matin Malek A , Nhan Duc D , Sulaiman Abdul H
Published: March 2010

In tropical countries rice has been identified as one of the crops that is particularly susceptible to the negative impacts of pesticide use. In addition to the physicochemical nature of the pesticide, tropical climatic conditions and agricultural practices play important roles in determining the fate and distribution of pesticides in the tropical paddy field ecosystem. The assessment of ecotoxicological effects of pesticides in the tropical paddy field ecosystem has been based primarily on acute lethality tests conducted on fish species commonly found in paddy fields. The effects of pesticides in the paddy field ecosystem on other nontarget organisms ranging from microalgae and cyanobacteria to paddy field crabs have also been investigated, although such studies are limited. As a means to promote a more judicious use of pesticides in the paddy field, the adoption of integrated pest management strategies have resulted in varying degrees of success. The most widely accepted form of control measure is the integration of multiresistant cultivars with reduced use of pesticides. Effective training of the paddy farmer has been identified as the key to successful implementation of integrated pest management strategies.
Fish and wildlife resources in the pantanal wetlands of Brazil and potential disturbances from the release of environmental contaminants
Authors: Alho Cleber J R , Vieira Luiz M
Published: March 2010

The Pantanal is one of the world's largest wetland ecosystems, encompassing 140,000 km2. The region is a breeding ground for waterfowl, and enormous rookeries of storks, herons, egrets, and ibises indicate a vast abundance of birds. The Pantanal is also one of the most important refuges for many of Brazil's threatened or endangered species, such as jaguars, giant anteaters, and swamp deer. The productive web of waters supports an important fishery industry. The Pantanal, with its extraordinary diversity and abundance of wildlife, is a threatened region. Deforestation, expanding agriculture, illegal hunting and fishing, unplanned tourism, and pollution with pesticides have caused a progressive deterioration of the natural environment, placing one of Brazil's most important ecosystems at risk. Gold mining is still common in the northern Pantanal. Along the Cuiabá river are 700 functional gold-mining dredges. In the town of Poconé, unregulated gold mines have also contaminated the area with mercury, which is used during the processing of gold. Approximately 50% of the fishes from the Cuiabá River and 35% from the Bento Gomes River have mercury levels higher than 0.5 μg/g, which is beyond the international standard for contamination. Fishes from the Paraguay River have levels below 0.5. Birds like Phalacrocorax olivaceus, Aramus guarauna, and Rosthramus sociabilis were also contaminated. No research has been conducted on the fate of pesticides in the Pantanal. However, because of the huge demand for soybean plantations on the upland areas surrounding Pantanal, the application of toxic agricultural chemicals is very common.
Deficiencies and toxicities of trace elements and micronutrients in tropical soils: Limitations of knowledge and future research needs
Authors: Davies Brian E
Published: March 2010

This article reviews present knowledge concerning deficiencies and toxicities of trace elements and micronutrients in tropical soils. The myth that all tropical soils are highly leached and nutrient-poor is challenged. Continuing use of the term “laterite” by ecologists and geologists is criticized and adoption of “plinthite” is urged. The trace element content of plinthite and its possible influence on micronutrient availability are described. Micronutrient limitations of tropical agriculture are related to soil type and formation, and the special problem of aluminum toxicity in acid soils is discussed in both agricultural and ecological contexts. Studies of micronutrient cycling in tropical forests or savannas are needed to supplement the emerging picture of the complexities of major element cycles in these ecosystems. Interest in gold mining has stimulated studies of the element in tropical soils, and mining of the metal is leading to mercury pollution in Amazonia.
Degradation of pesticides applied to banana farm soil: Comparison of indigenous bacteria and a microbial mat
Authors: Murray Reynold , Phillips Peter , Bender Judith
Published: March 2010

Indigenous bacteria from St. Vincent (West Indies) banana farm soil, enriched cultures of three isolates, and a microbial mat were tested for their ability to degrade carbofuran, chlordane, paraquat, and prophos. In single-pesticide application experiments, only 35.0% of the parent carbofuran was recovered after 21 d; paraquat recovery was 40.0%, and chlordane, 91.0%. In a mixture containing each pesticide, 42.0% of the parent carbofuran was recovered, and paraquat and chlordane recoveries were 52.0% and 94.0%, respectively. A microbial mat and the isolates were shown to mineralize [14C]carbofuran. Best results (93.11 μg [14C]carbofuran/kg dry microbial mat) were from a 15-d dark soil experiment. In field trials, the concentration of carbofuran decreased 82% with microbial mat treatment, and control plot concentrations actually increased 26%, The concentration of prophos decreased significantly after 4 d (0–6 mg/kg) in the plots with a microbial mat, whereas in control plots it increased from 7 to 12 mg/kg at day 0 to 180 mg/kg at day 4. After 60 d prophos was not detected in any microbial mat plot, whereas all but one control plot had it (0–12 mg/kg) in the soil.
Tropical ecotoxicology: Status and needs
Authors: Lacher Thomas E , Goldstein Michael I
Published: March 2010

Ecotoxicology has focused almost exclusively on countries and ecosystems in temperate zones. Tropical ecosystems, which combined contain as much as 75% of the global biodiversity, have been neglected. Tropical ecosystems are under increasing threat of development and habitat degradation from population growth and urbanization, agricultural expansion, deforestation, and mining. Some of these activities also lead to the release of toxic substances into the environment. Little research in ecotoxicology has been carried out in tropical environments. Techniques and procedures developed for temperate environments are often applied, even though physical and chemical environmental parameters in the tropics can be very different. Most research has focused on water quality and aquatic toxicology. The regulatory environment also varies among countries. We present a review of the literature on tropical ecotoxicology, with an emphasis on Latin America and the Caribbean. We also address priority areas for immediate research in the tropics. These include large-scale agricultural activities, especially banana, pineapple, and soybean farming, and gold mining with the associated heavy use of mercury. We outline the special issues that must be addressed as the field of tropical ecotoxicology progresses.
Extrapolating mineralization rates from the ready Co2 screening test to activated sludge, river water, and soil
Authors: Federle Thomas W , Gasior Sally D , Nuck Barbara A
Published: March 2010

The objective of this research was to derive empirical extrapolation factors by concurrently measuring mineralization rates of nine diverse chemicals in a Ready CO2 test (modified Sturm) and realistic 14C tests using activated sludge, river water, and sludge-amended soil while holding other variables constant. All nine chemicals were mineralized in the Ready test and each of the compartments, but no significant statistical relationships existed between biodegradation rates in the various tests. Mineralization rates in the Ready test were on average 8.1, 2.5, and 1.2 times lower than the rates in realistic activated sludge, river water, and soil tests, but variability in the scaling factors spanned up to 1.5 orders of magnitude. The scaling factors for extrapolating from ready CO2 data ranged from 1.7 to 19 for activated sludge, from 0.1 to 5.6 for river water, and from 0.3 to 2.8 for soil. Correlation analysis revealed that the scaling factors from the CO2 test to activated sludge and river water were related to the quantitative structure-activity relationship based solubility and log Kow estimates for the test chemicals.
Influence of pH on the toxic effects of zinc, cadmium, and pentachlorophenol on pure cultures of soil microorganisms
Authors: van Beelen Patrick , Fleuren-Kemilä Arja K
Published: March 2010

In this study the effect of the acidification of soil pore water on the uptake and toxicity of cationic and anionic pollutants was measured in an experimental model system. The influence of pH on the toxic effects of zinc, cadmium, and pentachlorophenol was studied in buffered suspensions of pure cultures of soil microorganisms. In this system the speciation of the toxicant, the pH, and the biomass are defined, constant, and thus easier to study than in a system with the solid soil matrix and pore water. The mineralization of [14C]acetate to 14CO2 was used to measure the toxic effects of pollutants on a fungus (Aspergillus niger CBS 121.49), an actinomycete (Streptomyces lividans 66), two Gram-negative Pseudomonas putida strains (MT-2 and DSM 50026), and a Gram-positive strain (Rhodococcus erythropolis A177). Large differences in sensitivity were observed between the species. For pentachlorophenol the highest EC50 was 81 mg/L for Pseudomonas putida at pH 8, whereas the lowest was 0.13 mg/L for Aspergillus niger at pH 6. Aspergillus niger was not sensitive to 1,000 mg Zn/L, whereas Pseudomonas putida at pH 7.8 showed the lowest EC50, 0.14 mg Zn/L. When pH was increased, pentachlorophenol became less toxic and showed less sorption to the biomass, whereas zinc and cadmium became more toxic and showed more sorption to the biomass. The results indicate that higher pore-water concentrations due to acidification of zinc- and cadmium-polluted soils may not be accompanied by increased toxic effects on microorganisms because of the relatively low toxicity of these metals in pore water at low pH.
Measurements of pesticide spray drift deposition into field boundaries and hedgerows: 1. Summer applications
Authors: Longley Martin , Čilgi Tamer , Jepson Paul C , Sotherton Nicolas W
Published: March 2010

The drift of fluorescent tracer in water and formulated pesticide sprays was measured at different heights and distances within 6-m-wide buffer strips (“Conservation Headlands”) and field boundaries surrounding mature winter cereal fields. Spray deposits were taken from artificial collectors. There was a diminution in deposition at the hedgerow, where a 6-m-wide buffer strip of unsprayed crop was employed between the sprayer and the hedgerow compared to where the entire crop edge was fully sprayed. There was some evidence that a mature crop would absorb some of this spray drift, reducing deposition on the hedge flora below crop level and, therefore, the nature of the buffer strip as well as it's width were thought to be important in determining hedgerow deposition rates. Frequency distributions of deposition along strips of hedgerow revealed that the unsprayed buffer zone also served to reduce the peaks in drift that might occur as a result of the pitch and yaw of travelling tractor booms. The vegetational complexity of the hedge bottom was also shown to determine spray deposition within field boundaries. Larvae of the cabbage white butterfly (Pieris brassicae[L.]) showed higher mortalities when exposed to hedgerow grasses adjacent to conventionally sprayed headlands compared to those adjacent to a Conservation Headland. A simple methodology for spray deposition studies is outlined, and implications of pesticide drift into field boundaries discussed.
Organic pollutants in the coastal marine environment off San Diego, California. 3. Using linear alkylbenzenes to trace sewage-derived organic materials
Authors: Zeng Eddy Y , Khan Azra R , Tran Kim
Published: March 2010

Linear alkylbenzenes (LABs) were detected in the Point Loma Wastewater Treatment Plant (PLWTP) effluent, Tijuana River runoff, microlayer, water column particulates, and sediments collected off the coast of San Diego in 1994. The distributions of LABs in various media and sampling locations suggested that these compounds were essentially derived from domestic waste discharges. The PLWTP outfall is a major source for LAB inputs, while the Tijuana River runoff discharges much lower amounts of LABs. However, the contents of sewage-derived organics can be enhanced in the sea surface microlayer near the mouth of the Tijuana River. In addition, the I/E ratios indicated that 30-55% of the LABs were degraded in the water column particulates and sediments. Other processes (e.g., dilution, evaporation, bioaccumulation, etc.) may also be important in removing LABs from the discharge zone. Sewage-derived organic materials can be carried into remote areas via suspension of fine particulates.
Effects of cations, temperature, and creosote on degradation of indole by Desulfobacterium indolicum (DSM 3383)
Authors: Licht Dorthe , Arvin Erik , Ahring Birgitte K
Published: March 2010

This work describes the activity of Desulfobacterium indolicum under different conditions. Hydroxylation of indole by the sulfate-reducing marine bacterium D. indolicum was related to the concentration of Na+ and Mg2+, whereas K+ and Ca2+ had no influence. Hydroxylation of indole by D. indolicum was possible in normal medium with cation concentrations corresponding to seawater at low temperatures (10-26°C). The effect of reduced cation concentrations was most pronounced at high temperatures (29 and 36°C) where only an incomplete hydroxylation was observed in the medium with reduced cation concentrations. Desul-fobacterium indolicum was more sensitive to the presence of an artificial creosote mixture when depleted for cations. Sixty milligrams of artificial creosote per liter inhibited hydroxylation of indole by 30% in a normal growth medium compared to an 86% inhibition in a medium with low concentrations of cations. Indole and quinoline were the only compounds degraded from a creosote mixture consisting of 25 compounds. It was concluded that D. indolicum is active towards indole and quinoline under growth conditions quite distinct from its optimal laboratory conditions.
Effect of copper chloride in vitro and in vivo on the hepatic erod activity in the fishDicentrarchus labrax
Authors: Stien Xavier , Risso Christine , Gnassia-Barelli Mauricette , Roméo Michèle , Lafaurie Marc
Published: March 2010

The effect of copper chloride was studied on the hepatic microsomal 7-ethoxyresorufin-O-deethylase (EROD) activity of the fish Dicentrarchus labrax intraperitoneally injected with benzo[a]pyrene (BaP). In vitro experiments showed that copper significantly decreased EROD activity, and IC50 was estimated at 50 μg Cu/L. The apparent Michaelis constant (Km) of cytochrome P4501A was constant, whereas maximum velocity (Vmax) decreased as a function of copper added to the incubation medium. (Km) of nicotinamide adenine dinucleotide phosphate [NADPH]-cytochrome P450 reductase increased as a function of copper concentration, whereas Vmax remained constant. Absorption spectra showed that the amount of cytochrome P420s increased as a function of copper concentrations added to the medium at the expense of cytochrome P450s. The injection of copper and BaP (in vivo experiments) to fish decreased EROD activity compared with the injection of BaP alone. An increase of immunoquantified CYP1A content measured by Western blotting (intense band of 55–60 kDa molecular weight) was noted in microsomes of fish injected with BaP compared with controls. In the case of fish treated with copper and BaP, the band was less intense and accompanied by another band of lower molecular weight. The destruction of the native P450s spectrophotometrically measured in the presence of copper implied that the catalytic activity would be diminished. This was confirmed by decreased EROD activity after either in vitro additions or in vivo treatment with copper. Moreover, immunodetection experiments suggested that the decrease of the catalytic activity resulted more from cytochrome P450s loss than from direct inhibition of EROD activity by copper.
Effects of free Cu2+ and Zn2+ ions on growth and metal accumulation in freshwater algae
Authors: Knauer Katja , Behra Renata , Sigg Laura
Published: March 2010

Five species of unicellular green algae were exposed to a broad range of Cu2+ and Zn2+ concentrations to examine the relationship between the free Cu2+ and Zn2+ ion concentrations and algal growth at metal concentrations relevant for freshwater phytoplankton. We estimated extra- and intracellular metal concentrations and characterized the adsorption of copper and zinc on algal surfaces. The optimal growth rate of Scenedesmus subspicatus occurred in a broad range of Cu2+ and Zn2+ concentrations (from 10−15 to 10−7 and from 10−12 to 10−55 M, respectively). Chlamydomonas reinhardtii reacted more sensitively toward copper, optimal growth was achieved only at a pCu (= -log[Cu2+]) around 11, whereas growth was optimal over a broad range of free Zn2+ concentrations (from 10−12 to 10−6 M). The optimal range for growth of Chlorella fusca occurred over about three orders of magnitude of the free Cu2+ concentration (from 10−13 to 10−10 M). Chlamydomonas cultures isolated from Lake Constance tolerated Cu2+ concentrations over seven orders of magnitude (pCu = 7 to 14). The growth of algae showed a high tolerance toward high intracellular copper and zinc concentrations. This suggests that the cells may immobilize the metals intracellularly. The affinity of copper for algal surfaces is higher than that of zinc in the experimental concentration range: adsorption constants log KCu (11.06) > log KZn (6.49) (pH = 7.9). These freshwater algae tolerate higher Cu2+ and Zn2+ concentrations than marine algal species. In comparison to our lake data, the results obtained from the culture algae indicate a possible role for copper as a limiting factor for certain algal species in eutrophic lakes.
Interactive effects on the erod-inducing potency of polyhalogenated aromatic hydrocarbons in the chicken embryo hepatocyte assay
Authors: Verhallen Eeske Y , van den Berg Martin , Bosveld A T C
Published: March 2010

The chicken embryo hepatocyte-7-ethoxyresorufin O-deethylase (EROD) assay is used as a method to measure the amount of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) equivalents (TEQs) in environmental samples. A common feature of EROD-induction assays in vertebrates is that they generate biphasic dose-response relationships that show dose-related increases of the EROD induction to a maximum activity, followed by a dose-related decrease at higher concentrations. In general, the maximum achievable enzyme activity decreases with increasing median effective concentration (EC50). This suggests that aryl hydrocarbon (Ah)-receptor binding affinity is not the only factor determining the enzyme activity. An additional factor can obscure the maximum EROD activity (Ymax) and EC50 of the enzyme activity. Cytotoxicity and competitive inhibition are ruled out as possible influencing factors. Coadministration of 2, 2′, 4, 4′, 5, 5′-hexachlorobiphenyl (PCB 153) and 2, 3, 7, 8-TCDD significantly reduces the EC50 value compared to administration of TCDD alone. The dose-related decrease at higher concentrations has been suggested to be induced by mechanisms other than the Ah-receptor-related mechanism responsible for the observed increases at low concentrations. These interactive effects have serious consequences for risk assessment based on bioassay-derived TEQs.
Persistence and fate of 2,3,4,6-tetrachlorophenol and pentachlorophenol in limnocorrals
Authors: Liber Karsten , Solomon Keith R , Carey John H
Published: March 2010

Three separate limnocorral experiments were conducted to assess the fate and effects of a commercial 2,3,4,6-tetrachlorophenol (TeCP) formulation (DIATOX®; 19.4% TeCP, 4.8% pentachlorophenol [PCP], 75.8% “inert” buffers) in an aquatic ecosystem. Nominal treatment concentrations for experiments 1 and 2 were 0.075 and 0.75 mg active ingredient (a.i.)/L and 0.75 and 1.50 mg a.i./L DIATOX®, respectively, with three replicates of each treatment. Pesticide was applied in the morning for experiment 1 and in the evening for experiment 2. For Experiment 3, unreplicated concentrations of 0.1, 0.25, 0.5, 1.0, 2.0, 4.0, and 7.3 mg a.i./L DIATOX® were chosen; pesticide was applied in the evening. In all three experiments, the pesticide was applied as a single, uniform surface treatment. Both TeCP and PCP dissipated rapidly from the water of treated limnocorrals. Times to 50% dissipation for TeCP and PCP in the integrated water column were generally similar within experiments but ranged from 0.4 to 1.1 d following the morning application of experiment 1 to 3.4 to 7.3 d following the evening applications of experiments 2 and 3. The faster initial dissipation of TeCP and PCP from the water following the morning application implicated photolysis as the primary degradation mechanism, as did the faster dissipation of chlorophenols from the surface layer than from other water depths during experiment 2. Aqueous dissipation rates for both compounds from the integrated water column were similar in all three experiments after the initial mixing period (1–4 d); the three-experiment average first-order rate coefficient for either compound after day 4 was 0.09/d. From a mass balance perspective, the majority of the chlorophenols remained in the water column. Neither compound accumulated in the sediments to any significant extent (< 0.1% of applied mass), but sediment-associated residues did dissipate at a considerably slower rate than residues in the water column. From 97 to >99% of the applied chlorophenols had dissipated from the water of treated enclosures by the end of the various experiments (42–63 d).
Toxicity and bioaccumulation of a mixture of heavy metals inChironomus tentans(Diptera: Chironomidae) in synthetic sediment
Authors: Harrahy Elisabeth A , Clements William H
Published: March 2010

This research investigated toxicity and bioaccumulation of a mixture of Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (BAFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 μg/g Cd, 10 μg/g Cu, 70 μg/g Pb, and 300 μg/g Zn) in synthetic sediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 × the base concentration for a period of up to 14 d in two uptake tests. Bioaccumulation of all four metals increased over the 14-d uptake phases. Concentrations of metals in chironomids were significantly correlated with exposure time in the uptake phases. Only concentrations of copper approached background levels after 7 d depuration. Uptake rate coefficients and elimination rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of Pb, steady-state BAFs were within a factor of about two of those calculated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies comparing toxicity and bioaccumulation of natural and synthetic sediments are necessary before the use of synthetic sediments is widely adopted.
Evidence that variability in ambient fathead minnow short-term chronic tests is due to pathogenic infection
Authors: Kszos Lynn Adams , Stewart Arthur J , Sumner James R
Published: March 2010

An examination of results from ambient fathead minnow subchronic toxicity tests identified a common characteristic of the tests, which manifests itself as a large among-replicate and between-test variance in survival. The unusual replicate-specific mortality in tests with ambient water appears to be due to pathogenic bacteria or fungi. This finding is based on the following facts: a comparison of survival among replicates in effluents and ambient waters showed that when mean survival was low (40-70%), among-replicate variation for ambient tests was greater than it was for the effluent tests; in 63 tests conducted at three locations over nearly 3 years, treating the water with ultraviolet (UV) light improved survival; a seasonal pattern to survival was present at ambient sites; survival was higher when minnows were separated by using 1 minnow/beaker rather than the standard system of 10 minnows/beaker; and survival tended to be higher in ambient sites contaminated with low levels of chlorine. The existence of the pathogen(s) does not mean that the test cannot be used effectively to assess toxicity of ambient waters; instead, it indicates that factors other than toxicity may need to be taken into consideration when interpreting the results.
Quantitative structure-activity relationships for weak acid respiratory uncouplers to Vibrio fisheri
Authors: Schultz T Wayne , Cronin Mark T D
Published: March 2010

Acute toxicity values (5- and 30-min Vibrio fisheri 50% luminescence inhibition) of 16 organic compounds thought to elicit their response via the weak acid respiratory uncoupling mechanism of toxic action were secured from the literature. Regression analysis of toxicities revealed that a measured 5-min V. fisheri potency value can be used as a surrogate for the 30-min value. Regression analysis of toxicity (30-min for potency [log pT 30−1]) versus hydrophobicity, measured as the 1-octanol/water partition coefficient (log Kow), was used to formulate a quantitative structure-activity relationship (QSAR). The equation log pT 30−1 = 0.489(log Kow) + 0.126 was found to be a highly predictive model (r2 adj. = 0.848). This V. fisheri QSAR is statistically similar to QSARs generated from weak acid uncoupler potency data for Pimephales promelas survivability and Tetrahymena pyriformis population growth impairment. This work, therefore, suggests that the weak acid respiratory uncoupling mechanism of toxic action is present in V. fisheri, and as such is not restricted to mitochondria-containing organisms.
Demonstration of a toxicological risk ranking method to correlate measures of ambient toxicity and fish community diversity
Authors: Hartwell S Ian
Published: March 2010

The goal of this study was to assess a new toxicological risk ranking model, field validate it with results from a battery of sediment and water column bioassays, and identify correlations of model output with fish community and population metrics. The model has five components: severity of effect, degree of response, bioassay variability, consistency, and number of measured endpoints. The model can reliably reduce an array of ambient toxicity data into a site-specific metric that is appropriate for comparisons with other metrics, such as Index of Biotic Integrity (IBI) or community diversity indices. The model is tolerant of variable amounts of data between stations. It does not generate probability limits without repeated sampling. The model can identify trends between sampling stations and document where chemical contamination is contributing to community impacts as well as where toxicological impacts are not likely to be contributing to observed population level impairment. The model was evaluated with field/laboratory data. Test sites were located in tributaries of Chesapeake Bay watersheds that are impacted by industrial, urban, and agricultural land use patterns. The toxicological risk scores correlate with fish community health metrics. The strongest correlations were between sediment toxicity risk and bottom trawl fish community diversity index.