Aquatic Tests Research Articles

Evaluation of the Biotic Ligand Model relative to other site-specific criteria derivation methods for copper in surface waters with elevated hardness

The goal of this study was to evaluate the reliability of the Biotic Ligand Model to predict Cu toxicity in very hard surface water (>200 mg/L as CaCO 3), relative to current copper criteria methodologies (hardness-based equation and the water-effect ratio; WER). To test these methods, we conducted acute Cu toxicity tests with three aquatic test species ( Ceriodaphnia dubia, Daphnia pulex and Pimephales promelas) in seven surface waters. The sites were representative of effluent-dependent or effluent-dominated streams common to the arid western United States of America (arid West) and a wide range of water quality variables were tested. In addition, concurrent Cu toxicity tests were conducted in laboratory waters that were matched to hardness and alkalinity of the sites to facilitate calculation of WER values. Results were used to characterize empirical relationships between water quality characteristics and Cu toxicity, and to compare measured Cu toxicity with Biotic Ligand Model (BLM) predictions. Acute toxicity tests were also conducted with C. dubia and P. promelas in a range of Ca or Mg-dominated hardness concentrations to determine the independent effects of Ca or Mg on Cu toxicity at high hardness levels. Conclusions from this study suggest that the BLM generates appropriate criteria for the waters tested in this study when compared to the hardness-based equation or WER approach. Although the historical site-specific methods are useful for surface waters with hardness ≤250 mg/L as CaCO 3, the unique conditions of arid West streams require site-specific methods that account for the influences of critical water quality variables (i.e., pH, dissolved organic carbon, alkalinity, Ca, Mg and Na). Therefore, the BLM offers an improved alternative to the hardness-based and WER approaches, particularly for situations where the current methods would be under-protective of sensitive aquatic life.

Effects of seven organic pollutants on soil nematode Caenorhabditis elegans

Caenorhabditis elegans is a free-living soil nematode that is commonly used as a model for toxicity tests. The aim of this study was to investigate the toxicity of seven organic pollutants: four azaarenes (quinoline, acridine, phenazine, and 1,10-phenanthroline), short-chain chlorinated paraffins, and two organochlorinated pesticides (toxaphene and hexachlorobenzene). The exposure to all chemicals was carried out in three test media (soil, agar, and aquatic medium), and adult mortality was evaluated after 24 and 48 h. Toxaphene was the most toxic substance with LC 50 (48 h) of 379 mg/kg in the soil and 0.2 mg/L in the aquatic medium. Quinoline was the most toxic chemical in agar test with LC 50 (48 h) of 10 mg/L. HCB showed a very low toxicity in all tests, maybe due to its very low water solubility. Longer than 24-h test duration was found necessary for getting more correct data on toxicity. In comparison with other studies, C. elegans was less sensitive than other soil invertebrates. Different response might be attributed to different exposure routes and shorter test duration. Equilibrium partitioning theory was used to calculate K oc from results of soil and aquatic tests but this approach was found not working. Our results suggest that the tests with nematode C. elegans should be included to the battery of tests for risk assessment of POPs in soil.

Rapid Screening for Soil Ecotoxicity with a Battery of Luminescent Bacteria Tests

A bacterial test battery, involving i) Microtox, an aquatic test, ii) the Flash assay, a soil-suspension test (with Vibrio fischeri as the test organism), and iii) the Metal Detector assay, a semi-specific aquatic test for heavy metals (with recombinant luminescent Escherichia coli), was used in a combined toxicological and chemical hazard assessment of Estonian soils sampled from a former Soviet military airfield (13 samples) and from traffic-influenced roadsides (5 samples). The soils showed slightly elevated levels of total petroleum hydrocarbons (TPH), but not of heavy metals. In most of the samples, the levels of TPH did not exceed the Estonian permitted limit values set for residential areas. Toxicity testing was performed on both fresh and dried soils, after aqueous extraction for 1 hour and 24 hours. The toxicity results obtained with the Microtox test did not significantly differ in all of the sample treatment schemes; however, it appeared that the drying and sieving of the soils increased the bioavailability of toxicants, probably due to an enlarged reactive soil surface area. According to chemical analysis of the soils and the data from the Microtox test and the Metal Detector assay (performed on aqueous elutriates of the soils), these soils would not be considered to be hazardous. In contrast, the Flash assay performed on soil-water suspensions of dried soils, showed that most of the soils were toxic and thus probably contained undetermined particle-bound bioavailable toxicants. The photobacterial toxicity test (the Flash assay) can be recommended for the rapid screening of soils, as it is sensitive, cheap and inexpensive, and provides valuable information on particle-bound bioavailable toxicants, useful for complementing a chemical analysis and for assessing the risks originating from polluted soils.

Assessing Environmental Impacts of Veterinary Products: Lessons from VICH

In 1996, the Steering Committee of the VICH (International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Products)1 selected ecotoxicity as one of the five initial topics2 for harmonization under this joint government-industry program. This topic was selected for harmonization by the principal parties to VICH (viz., European Union, United States, and Japan) because of the gulf in drug registration requirements that existed among these regions at the time. A working group (VICH Ecotox Working Group or VICH EWG) was formed in 1997 to develop harmonized guidelines, taking into account any existing guidance documents and legislative/regulatory requirements. The VICH EWG included representatives from industry and regulatory authorities from the European Union, United States, Japan, Australia, New Zealand, and Canada. The VICH EWG held nine face-to-face meetings over a 7-year period that ended in 2004. The task of developing the guidelines was split into two phases: phase I and phase II. For drugs that qualify for a VICH phase I assessment only, environmental fate and effects data are not required for evaluation of the potential risk of drug residues on nontarget species in the environment. For products that require a full assessment (VICH phase II), environmental fate and effects study data are required to assess the potential impact of veterinary drug residues (parent and metabolites, in certain situations) on nontarget species in aquatic and terrestrial ecosystems. A phase II assessment of a given veterinary drug residue includes studies of (1) physicochemical properties (eg, water solubility, octanol/water partitioning), (2) binding to soils, (3) biodegradation in soil or aquatic test systems, and (4) effects of the drug residue on select aquatic (algae, daphnia, fish) and terrestrial species (soil microflora, plants, earthworms, and possibly dung beetles and flies). The studies recommended for a phase II assessment are to be done in accordance with Organization for Economic Cooperation and Development (OECD) protocols (found at www.oecdwash.org/PUBS/PERIOD/per-chemical.htm). Alternatively, International Organisation for Standardization (ISO) protocols (found at www.iso.ch/iso/en/CatalogueListPage.CatalogueList) are used if final OECD protocols do not exist. Whether these studies are to be done in accordance with good laboratory practices (GLPs) is a region-by-region matter, and hence it is not recommended in the VICH phase II guidance document. As of 2006, the VICH phase I and II guidelines have been adopted officially in the European Union, United States, Japan, Australia, and New Zealand. They have been formally adopted in the European Union, United States, Australia, and New Zealand.3 These documents are available on various Web sites (Food and Drug Administration’s Center for Veterinary Medicine [FDA/CVM] at www.fda.gov/cvm, European Medicines Agency [EMEA] at www.emea.europa.eu, and VICH4 at www.vichsec.org). Algorithms to calculate worst-case predicted environmental concentrations (PECs) could not be harmonized by the VICH EWG, ostensibly because of the differences in the animal husbandry and land-use practices of the respective VICH regions. Development of PEC calculation algorithms was left to the individual regions5 to develop, and several approaches have emerged that may be used by regulators and applicants alike. The effort to develop harmonized ecotoxicity testing guideines under the VICH program was largely concluded to be successful by regulators and many in the pharmaceutical industry. It opened channels for meaningful dialogue between regulators and industry personnel on appropriate approaches to assessing the potential risks of veterinary drug residues on nontarget species in the environment. But, the true measure of how successful this 7-year effort was will be determined in the coming years as experience is gained using these guidelines in the regions where they were adopted.

Combination effects of herbicides on plants and algae: do species and test systems matter?

Risk assessment of herbicides towards non-target plants in Europe is currently based solely on tests on algae and floating aquatic plants of Lemna sp. Effects on terrestrial non-target species is not systematically addressed. The purpose of the present study was to compare combination effects of herbicide mixtures across aquatic and terrestrial test systems, and to test whether results obtained in the traditional aquatic test systems can be extrapolated to the terrestrial environment. This was done by evaluating ten binary mixtures of nine herbicides representing the seven most commonly used molecular target sites for controlling broadleaved weeds. Data were evaluated statistically in relation to the concentration addition model, and for selected concentrations to the independent action model. The mixtures were tested on the terrestrial species Tripleurospermum inodorum (L.) Schultz-Bip. (Scentless Mayweed) and Stellaria media (L.) Vill. (Common Chickweed), and on the aquatic species Lemna minor L. (Lesser duckweed) and the alga Pseudokirchneriella subcapitata (Korschikov) Hindak. For the two mixtures of herbicides with the same molecular site of action, the joint effect was additive. For the eight mixtures of herbicides with different sites of action, two of the mixtures were consistently antagonistic across species, while for the remaining six mixtures the joint effect depended on the species tested. This dependence was, however, not systematic, in the sense that none of the species or test systems (terrestrial versus aquatic) had a significantly higher probability of showing synergistic or antagonistic joint effects than others. Synergistic interactions were not observed, but approximately 70% of the mixtures of herbicides with different sites of action showed significant antagonism. Hence, the concentration addition model can be used to estimate worst-case effects of mixtures of herbicides on both terrestrial and aquatic species. Comparing the sensitivity of the species to a 10% spray drift event showed that the terrestrial species were more vulnerable to all herbicides compared with the aquatic species, emphasising the importance of including terrestrial non-target plants in herbicide risk assessment.

Reproducibility of binary‐mixture toxicity studies

Binary-mixture studies often are conducted with the aim of elucidating the effect of one specific chemical on the biological action of another. The results can be interpreted in relation to reference models by the use of response-surface analyses and isobolograms. The amount of data needed for these analyses is, however, extensive, and the experiments therefore rarely are repeated. In the present study, we investigate the reproducibility of isobole shapes of binary-mixture toxicity experiments in terms of deviation from the reference model of concentration addition (CA), dose-level dependence, and isobole asymmetry. We use data from four herbicide mixtures tested in three to five independent experiments on the aquatic test plant Lemna minor and the terrestrial plant Tripleurospermum inodorum. The results showed that the variation both within and among experiments was approximately half the size for the aquatic test system compared to the terrestrial system. As a consequence, a consistent deviation from CA could be obtained in three of four herbicide mixtures for L. minor, whereas this was only the case for one or two of the herbicide mixtures tested on T. inodorum. For one mixture on T. inodorum, both CA synergism and antagonism were detected. Dose-dependent effects could not be repeated consistently, just as the asymmetry found in some isoboles could not. The study emphasizes the importance of repeating mixture toxicity experiments, especially for test systems with large variability, and using caution when drawing biological conclusions from the test results.

Daphnia magna and ecotoxicogenomics: Gene expression profiles of the anti-ecdysteroidal fungicide fenarimol using energy-, molting- and life stage-related cDNA libraries

In the present study, the existing life stage-specific cDNA library was extended with energy- and molting-related genes using Suppression Subtractive Hybridization PCR and a microarray for the aquatic test organism Daphnia magna was created. A gene set of 2455 fragments was produced belonging to different pathways such as carbohydrate and lipid metabolism, O 2 transport and heme metabolism, immune response, embryo development, cuticula metabolism and visual perception pathways. Using this custom microarray, gene expression profiles were generated from neonates exposed to three concentrations of the anti-ecdysteroidal fungicide fenarimol (0.5, 0.75, 1 μg/ml) during 48 h and 96 h. In total, 59 non-redundant genes were differentially expressed, of which more genes were down- than up-regulated. The gene expression data indicated a main effect on molting specific pathways. At the highest concentration, a set of proteolytic enzymes – including different serine proteases and carboxypeptidases – were induced whereas different cuticula proteins were down-regulated (48 h). Moreover, effects on embryo development were demonstrated at the gene expression as well as at the organismal level. The embryo development related gene vitellogenin was differentially expressed after 96 h of exposure together with a significant increase in embryo abnormalities in the offspring. This study suggests that this Daphnia magna microarray is of great further value for the elucidation of molecular mechanisms of toxicity and for the future development of specific biomarkers for hazard characterization.

Comparative acute toxicity of potassium permanganate to nontarget aquatic organisms

Potassium permanganate (KMnO4) is used worldwide in freshwater pond aquaculture for treatment and prevention of waterborne external parasitic, bacterial, and fungal diseases. Nevertheless, KMnO4 has not been approved by the U.S. Food and Drug Administration, and insufficient information exists to allow evaluation of the environmental risk of KMnO4 exposures. Limited data exist concerning KMnO4 toxicity to nontarget species in systems receiving aquaculture effluent from treated ponds. The goal of this research is to generate effects data for use in developing an ecological risk assessment of KMnO4. Toxicity tests were used to compare the relative sensitivities of five standard aquatic test species to KMnO4. Acute toxicity test results using synthetic moderately hard water show static 96-h mean median lethal concentration (LC50) values +/- standard deviation (SD) of 0.058 +/- 0.006 mg/L for Ceriodaphnia dubia, 0.053 +/- 0.009 mg/L for Daphnia magna, 2.13 +/- 0.07 mg/L for Pimephales promelas, 4.74 +/- 1.05 mg/L for Hyalella azteca, and 4.43 +/- 0.79 mg/L for Chironomus tentans. Most of these values are below the recommended KMnO4 treatment rate of at least 2.0 mg/L or 2.5 times the water's potassium permanganate demand (PPD; an estimation of the available reducing agents in the exposure water), suggesting significant environmental risk. However, repeating these laboratory tests using pond water resulted in significantly reduced toxicity, with static 96-h mean LC50 values (+/-SD) of 2.39 +/- 0.36 mg/L for C. dubia, 1.98 +/- 0.12 mg/L for D. magna, 11.22 +/- 1.07 mg/L for P. promelas, 13.55 +/- 2.24 mg/L for H. azteca, and 12.30 +/- 2.83 mg/L for C. tentans. The PPD of synthetic moderately hard water was 0.329 +/- 0.114 mg/L; however, pond water PPD was 5.357 +/- 0.967 mg/L. The effective disease-treating dose based on 2.5 times the PPD would thus be 0.823 and 13.392 mg KMnO4/L, respectively, exceeding the LC50 for most of these nontarget organisms, even in pond water, immediately after treatment.

A simple model to predict compound loss processes in aquatic ecotoxicological tests: calculated and measured triphenyltin levels in water and biota

A new simple model, based on the fugacity approach, has been developed to provide a predictive tool useful in the planning phase of aquatic ecotoxicological tests for assessing the actual daily concentrations in water. In our experiments, three nominal concentrations (100, 225, and 500 ng L−1) of triphenyltin chloride (TPT-Cl) were employed for an exposure period of 28 days in 50 L aquaria with the echinoderm Antedon mediterranea as test species. Extracts from water and biota samples collected during the experiments were analysed by GC-MS/MS, after the extraction/derivatization step. An indicative mean BCF (V/V) on a fresh weight base of 3.5 × 104 ± 0.8 × 104 (standard deviation) could be calculated for A. mediterranea. Three different compartments (air, water and biota) and main advection/reaction processes are taken into account in the model design, and the comparison between predicted and measured concentrations in both water and biota for the three concentrations tested confirmed that the assumptions given in our model application were valid and useful for further applications.

Degradation and detoxification of hexachlorocyclohexane isomers by Pseudomonas aeruginosa ITRC-5

Abstract Technical-hexachlorocyclohexane (t-HCH) consists of four major isomers i.e. α -, β -, γ - and δ -HCH. The insecticidal γ -HCH is separated from it by solvent extraction, and the remaining ‘muck’ is discarded. HCH-isomers from the ‘muck’ can potentially enter the environment and impart toxicity. For its biological treatment, biodegradation of HCH-isomers by the isolated bacterium Pseudomonas aeruginosa ITRC-5 was evaluated. In its presence, from 1.7 mM ‘muck’, >98% α - and >80% β -, γ - and δ -HCH were degraded after 24 days of incubation. The degradation was optimal at 1.7 mM input concentration of ‘muck’, pH 9.0, and temperature 20–30 °C. Under these conditions, from 2 g ‘muck’, >90% Σ-HCH, i.e. the sum of α , β , γ , and δ -HCH, were degraded in a 1.0-liter batch-reactor after incubation for 4 cycles of 5 weeks each. The degradation was accompanied with 90% reduction in the toxicity of ‘muck’ to the aquatic test organism Daphnia magna . The isolated bacterium ITRC-5 can therefore be used for the degradation and detoxification of HCH-wastes, prior to their disposal.

Biotests and biosensors in ecotoxicological risk assessment of field soils polluted with zinc, lead, and cadmium

The combined chemical and ecotoxicological hazard evaluation study was conducted on 60 smelter-influenced soils containing 1 to 13, 50 to 653, and 100 to 1,198 mg/kg of Cd, Pb, and Zn, respectively. For these soils (liquid-to-soil ratio = 10), water extractability of Zn, Cd, and Pb was less than 0.19% (median values). Acetic acid (0.11 M) extracted 23, 9.7, and 0.7% of Cd, Zn, and Pb, respectively. Although heavy metal concentrations in the studied soils were high, the toxic effects of water extracts were observed only in few samples and in few biotests (algae Selenastrum capricornutum and metal detector assay). For most of the aquatic test organisms (e.g., crustaceans, photobacteria), the bioavailable concentrations of metals in soil-water extracts were either subtoxic, or the adverse effects were compensated by soil nutrients, etc. However, analysis of the soils with recombinant Cd sensor Bacillus subtilis (pTOO24) showed that about 65% of these apparently subtoxic samples contained bioavailable Cd when analyzed in the suspension assay (detection limit 1.5 mg Cd/kg soil), indicating the desorption of Cd induced by direct contact of bacteria with soil particles. The median bioavailable fraction of Cd (1%) was 23-fold lower than the fraction extracted by acetic acid. The Pb-Cd sensor Staphylococcus aureus (pT0024) detected bioavailable Pb only in the suspensions of five of the most lead-polluted soils (>417 mg Pb/kg): the median bioavailability of Pb was 0.42%. Consequently, the hazard assessment relying on total metal levels in soils should be revised by critical comparison with data obtained from bioassays. Development and use of biosensors (excellent tools for mechanistic studies and signaling hazard already at subtoxic level) should be encouraged.

Application of frog embryo teratogenesis assay‐Xenopus to ecological risk assessment

An expert workshop recently was convened to consider the frog embryo teratogenesis assay-Xenopus (FETAX) as a screening method for identifying the potential developmental toxicity of single chemicals and chemical mixtures. One recommendation from the workshop was that, in order to determine the utility of FETAX for ecological risk assessments, additional consideration of how the assay is conducted is necessary. In addition, a comparative evaluation would be useful of FETAX endpoints (i.e., survival, malformations, growth) versus each other, endpoints from aquatic toxicity tests using more commonly tested species of cladocerans and fish, and tests with other amphibian species. This review provides an evaluation and critique of the current FETAX protocol from two perspectives: Practical considerations relative to conducting the test and sensitivity of the assay (and associated endpoints) compared to tests with other species. Several aspects of the current standard protocol, including test temperature, diet, loading rates, and chemical exposure options, need to be modified to ensure that the assay is robust technically. Evaluation of FETAX data from the open literature indicates that growth is the most sensitive endpoint in the assay, followed by malformations and then survival; unfortunately, the growth endpoint often is not considered or reported in the assay. Comparison of FETAX data with acute toxicity data from tests with other amphibians or traditional aquatic test species indicates FETAX is relatively insensitive. This suggests that environmental risk assessments using acute hazard data from tests with traditional aquatic test species usually would be more protective of native amphibian species than risk assessments that use hazard data from FETAX.

Dimeric phenanthrenoids from Juncus acutus

Two new dimeric phenanthrenoids have been isolated by the methanol extract of rhizomes of Juncus acutus. The structures have been determined on the basis of their spectroscopic properties and by chemical correlation. The compounds showed in vitro phytotoxicity against Selenastrum capricornutum, a microalga used in aquatic tests.

Population Consequences of Fipronil and Degradates to Copepods at Field Concentrations: An Integration of Life Cycle Testing with Leslie Matrix Population Modeling

The predominant data used in ecological risk assessment today are individual-based rather than population-based; yet environmental policies are usually designed to protect populations of threatened species or communities. Most current methods in ecotoxicology are limited by largely logistic/ technology-driven requirements that yield data for a relatively small number of test species and end points that focus on acute lethality or sublethal nonproduction-based parameters (e.g., biomarkers, mutagenesis, genetic change, physiological condition). A contrasting example is presented here showing the predictive ability of meiobenthos-based full life cycle toxicity testing to extrapolate multi-generational effects of chemicals on variables of import to population growth and maintenance. Less than 24-h-old larvae of a meiobenthic copepod were reared individually in 96-well microplate exposures to parent and degradates of the phenylpyrazole insecticide fipronil. Survival, development rates, sex ratio change, fertility, fecundity, and hatching success were tracked daily for 32 d through mating and production of three broods in spiked seawater. These data were then inserted in a Leslie (Lefkovitch) matrix stage-based population growth model to predict relative rates of population increase (lambda) and changes in net population growth with time and toxicant concentration. Field-reported test concentrations produced strong reproductive (52-88%) and net production (40-80%) depressions for parent (at 0.25 and 0.5 microg/L), desthionyl (0.25 and 0.5 microg/L), and sulfide (0.15 microg/L) moieties as compared to controls. Spiked sediment exposures of 65-300 ng of fipronil/g of dry sediment yielded significantly reduced production rates per female that were 67-50% of control production. The consistent reproductively linked impacts of fipronil and its degradation products at the population maintenance levels suggest risks to sediment-dwelling crustaceans at concentrations well below noneffects for most aquatic test species based on risk assessment data from primarily acute and sub-life cycle toxicity tests.

Biological degradation of PVA/CH blends in terrestrial and aquatic conditions

A new material, the water soluble blend of poly-vinylalcohol and collagen hydrolysate (PVA/CH) was developed in Slovakia. Results from a recent biodegradation study including three blend variants differing in the collagen content are presented. Two different biodegradation tests, one in compost environment, the other at aquatic conditions and additional compost analysis after degradation of the polymer have been done. Degradation rates were determined for both test systems and the carbon conversion rates were calculated by drawing up a carbon balance out of the aquatic test. The results proofed positive influence of collagen hydrolysate on degradation but also show a relatively low biological degradability of PVA under the applied test conditions. At least, no negative influence on the compost composition was detected.

Results of Long‐term Sediment Quality Studies on the River Elbe

AbstractThe results of long‐term studies in the Upper and Middle Elbe River between 1991 and 2001 are presented and the temporal and spatial trends in sediment contamination and toxicity are studied. Although the concentrations of heavy metals and arsenic have significantly decreased in the last 10 years for most of the toxic elements they are still far from natural background values. For organic priority pollutants increasing as well as decreasing trends are observed, depending on the Elbe reach and/or the parameter under consideration. Elbe sediments have a permanent measurable toxicity. It is usually low in terms of aquatic tests as far as the persisting hot spots are not considered. Whole sediment testing with nematode Caenorhabditis elegans which was started in 1997 revealed clear toxic effects. In contrast to the priority pollution situation, no significant trend could be found in general sediment toxicity between 1992 and 2001.

Sequencing Batch Reactor Biodegradation of Hydrolyzed Sarin as Sole Carbon Source

The chemical nerve agent sarin (o-isopropyl methylphosphonofluoridate) was hydrolyzed at 7.18 weight percent in aqueous sodium hydroxide yielding primarily o-isopropyl methylphosphonic acid (IMPA). This hydrolysate was diluted and fed as sole carbon source to activated sludge in an aerobic sequencing batch reactor. Feed chemical oxygen demand (COD) concentrations ranged from approximately 2500 mg/L (initial) to 5000 mg/L (final). The reactor was operated essentially on a 15-day hydraulic residence time. Overall COD removal efficiency was 86.2% and the IMPA in the feed was converted to methylphosphonic acid. MICROTOX® and Daphnia magna aquatic toxicity testing showed the effluent to be of very low toxicity to aquatic test organisms. The final MPA product was effectively absorbed by Phoslock™, which is a lanthanide modified clay.

Using rotifer population demographic parameters to assess impacts of the degradation products from trinitrotoluene phytoremediation

The objective of this study was to evaluate the chronic lethal and sublethal aquatic toxicity effects associated with the phytoremediation of water contaminated with 2,4,6-trinitrotoluene (TNT) by the wetland plant species Myriophyllum aquaticum (parrot feather). Rotifers ( Brachionus calyciflorus) feeding on an algal species ( Nannochloropsis spp.) were used as the aquatic test organisms. Continuous flow laboratory microcosms were used to quantify effects on rotifer populations from TNT and the primary degradation product aminodinitrotoluene (ADNT) during and after phytoremediation. Rotifer demographic parameters from life tables, including survivorship, fecundity, reproductive values, net reproductive rate, generation time, intrinsic growth rate, and life expectancy, were used as measures of treatment effects. High-performance liquid chromatography analyses were performed to determine nitroaromatic concentrations. Results from this study have revealed significant differences in rotifer demographic parameters between microcosms with elevated initial TNT concentrations. Significant differences in demographic parameters also existed between the microcosms that did and did not receive phytoremediation treatment and the control microcosms. Study results have indicated that TNT phytoremediation via artificial wetlands not only may clean up hazardous waste at munitions sites but also may encourage the growth of aquatic populations such as rotifers.

Sensitivity of aquatic plants to the herbicide metsulfuron-methyl

The sensitivity of 12 aquatic plant species to the herbicide metsulfuron-methyl was tested in microcosm experiments under two growth conditions. As reference species, barley ( Hordeum vulgare) and oil-seed rape ( Brassica napus) were grown with their roots submerged in the microcosms. Two response variables were chosen: relative growth rate and specific leaf area (SLA). SLA was the most sensitive response variable, with 11 of the 12 aquatic species responding to the herbicide. EC 50 values varied 56-fold between species, with the commonly used aquatic test species Lemna minor being one of the most sensitive. Fast-growing species with a small exposed leaf area proved to be more sensitive to the herbicide than slow growing species with a large exposed leaf area, which was believed to be primarily due to variations in growth rates rather than to variations in exposed leaf area. The aquatic plants displayed high tolerance in growth to metsulfuron compared with the sensitive crop oil-seed rape. Hence, possible spray-drift events and leaching of the herbicide applied at agricultural rates are not considered to have a large impact on the growth of the aquatic flora tested.

Investigation of the biodegradability of water-insoluble materials in a solid test based on the adaptation of a biological oxygen demand measuring system

The usual BOD measuring systems used for monitoring the degradation of biodegradable materials are applied for the assessment of biodegradation exclusively in aquatic tests by detecting the amount of O 2 consumed during degradation. In our study, a new, solid test application of a BOD system optionally capable to detect CO 2 evolved during degradation is presented. After the optimisation of sample concentration and test temperature, the measurement set-up possessing relatively small reaction vessels of 250 ml with 80 g of soil mix proved to supply reliable and reproducible results. The system was optimised with microcrystalline cellulose—used as reference material in aquatic and solid test as well—showing 89.3±3.2% degree of degradation after 21 days, and it was applied for the assessment of biodegradation of commercially available non-powdered (films and kraft-paper) samples indicating degrees of degradation between 24.9 and 55.4%.