Toxicological Responses of the Earthworm Eisenia fetida to 18-Crown-6 Under Laboratory Conditions

The earthworm Eisenia fetida was exposed to artificial soil supplemented with 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) to investigate its effects on earthworm mortality, growth, avoidance, burrowing behavior and respiration. The results revealed that 18-crown-6 had the potential to negatively affect the behavior of earthworms. The 7-d LC₅₀ was 585 mg kg^?1 soil. Avoidance behavior was the most sensitive endpoint, with a 48-h EC₅₀ of 120 mg kg^?1 soil. Growth, burrow length and respiration showed general decreases with increasing 18-crown-6 concentrations. Behavioral endpoints and respiration may be regarded as sensitive parameters in evaluating the toxicity of this chemical to earthworms.     

Using Transgenic Caenorhabditis elegans in Soil Toxicity Testing

Soil bioassays are important tools for evaluating toxicological effects within the terrestrial environment. The American Society for Testing and Materials E2172-01 Standard Guide outlines a method for conducting laboratory soil toxicity tests using the nematode Caenorhabditis elegans. This method is an efficient tool for extracting C. elegans from soil samples and can be carried out after a 24-h exposure period using relatively small amounts of soil. Drawbacks of this method include problems with (1) recovery of nematodes from soils containing a high percentage of organic matter, and (2) distinguishing indigenous nematode species from nematodes added for the laboratory test. Due in part to these issues, C. elegans has not been extensively accepted for use in soil testing. To address these concerns and improve upon the American Society for Testing and Materials method, this project focused on using transgenic strains of C. elegans carrying a GFP-expressing element. Lethality and behavior tests revealed that the transgenic nematodes respond similarly to the wild-type N2 strain, indicating that they can be used in the same manner in soil testing. The GFP marker is easily identifiable not only within soils containing a large amount of organic matter, but also in field-collected soils containing indigenous nematodes. These results support the use of transgenic GFP C. elegans in soil bioassays as a tool to further the reliability of laboratory toxicity tests.     

Sensitivity of Lamprey Ammocoetes to Six Chemicals

As part of the ecological risk assessment for Portland Harbor Superfund site, a study was conducted to address the question of whether the use of surrogate species in the risk assessment would be protective of lamprey ammocoetes. The study evaluated the acute toxicity of six chemicals: pentachlorophenol, copper, diazinon, aniline, naphthalene, and lindane; these chemicals represent the toxic modes of action of oxidative phosphorylation uncoupler, gill dysfunction, acetylcholinesterase inhibitor, polar narcosis, narcosis, and central nervous system interference, respectively. Field-collected lamprey ammocoetes were exposed to each of the six chemicals in a definitive 96-h flow-through acute water-only toxicity test. LC₅₀s were calculated for pentachlorophenol at 31 μg/l, copper at 46 μg/l, diazinon at 8.9 mg/l, and aniline at 430 mg/l. Species sensitivity distributions based on LC₅₀s for aquatic organisms indicated that lamprey ammocoetes were relatively sensitive to pentachlorophenol (15th percentile). The sensitivity of lamprey ammocoetes to copper approximated the average of aquatic species tested (46th percentile). Lamprey ammocoetes were relatively insensitive to diazinon and aniline (72th and 90th percentile, respectively). The 96-h LC₅₀ for naphthalene was estimated at 10 mg/l, based on 50% mortality in the highest concentration. Based on a comparison with LC₅₀s for four other fish species, ranging from 2.0 to 6.6 mg/l, lamprey ammocoetes were relatively insensitive to naphthalene. A 96-h LC₅₀ could not be derived for lindane, with 12.5% mortality in the highest test concentration of 2.68 mg/l. LC₅₀s for numerous other fish species ranged from 0.001 to 0.24 mg/l, indicating that lamprey ammocoetes were relatively insensitive to lindane. The study concluded that the use of surrogate species in the ecological risk assessment for Portland Harbor would be protective of lamprey ammocoetes.     

Acute and Chronic Toxicity of Copper to the Euryhaline Rotifer, <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> (“L” Strain)

This article presents data from original research, intended for the use in the development of copper (Cu) criteria for the protection of estuarine and marine organisms and their uses in the United States. Two 48-h static-acute toxicity tests—one with and one without added food—and a 96-h static multigeneration life-cycle test (P1–F2 generations) were performed concurrently using the euryhaline rotifer Brachionus plicatilis (“L” strain) to develop a Cu acute-to-chronic ratio (ACR) for this species. Tests were performed at 15 g/L salinity, at 25°C, and the exposure concentrations of dissolved Cu were verified. Supplemental chemical analyses were performed and reported for the development of a Cu–saltwater biotic ligand model (BLM). Supplemental analyses included alkalinity, calcium, chloride, dissolved organic carbon (DOC), hardness, magnesium, potassium, sodium, and temperature. The acute toxicity test measurement end points were the dissolved Cu median lethal concentration (LC₅₀) values based on rotifer survival. The chronic measurement end points were the dissolved Cu no-observed-effect concentration (NOEC), lowest-observed-effect concentration (LOEC), EC₂₅, EC₂₀, and EC₁₀ based on the intrinsic rate of rotifer population increase (r). The 48-h LC_50Fed, 48-h LC_50Unfed, 96-h NOEC, 96-h LOEC, EC₂₅, EC₂₀, and EC₁₀ were 20.8, 13.4, 6.1, 10.3, 11.7, 10.9, and 8.8 μg Cu/L, respectively. The ACRs were calculated as ratios of each 48-h LC₅₀ value [fed and unfed) and each of the 96-h chronic values (ChV; geometric mean of NOEC and LOEC)], EC₁₀, EC₂₀, and EC₂₅. The ACRs ranged from 1.15 to 2.63.     

The Effect of Tributyltin-Oxide on Earthworms, Springtails, and Plants in Artificial and Natural Soils

Chemical bioavailability in Organisation for Economic Co-operation and Development (OECD) artificial soil can contrast with bioavailability in natural soils and produce ecotoxicologic benchmarks that are not representative of species’ exposure conditions in the field. Initially, reproduction and growth of earthworm and Collembolan species, and early seedling growth of a dicotyledonous plant species, in nine natural soils (with a wide range of physicochemical properties) and in OECD soil were evaluated. Soils that supported reproduction and growth of the test species were then used to investigate the toxicity of tributyltin-oxide (TBT-O). Natural soils caused greater toxicity of TBT-O to earthworms (EC₅₀ values varied from 0.5 to 4.7 mg/kg soil dry weight [dw]) compared with toxicity in OECD soil (EC₅₀ = 13.4 mg/kg dw). Collembolans were less sensitive to TBT-O than earthworms in natural soils, with EC₅₀ values ranging from 23.4 to 177.8 mg/kg dw. In contrast, the toxicity of TBT-O to collembolans in OECD soil (EC₅₀ = 104.0 mg/kg dw) was within the range of EC₅₀ values in natural soils. Phytotoxicity tests revealed even greater difference between the effects in natural soils (EC₅₀ values ranged from 10.7 to 189.2 mg/kg dw) and in OECD soil (EC₅₀ = 535.5 mg/kg dw) compared with results of the earthworm tests. Studies also showed that EC₅₀ values were a more robust end point compared with EC₁₀ values based on comparisons of coefficients of variation. These results show that toxicity testing should include studies with natural soils in addition to OECD soil to better reflect exposure conditions in the field.     

Assessing the toxicity of contaminated soils using the nematode Caenorhabditis elegans as test organism

In this study, nine uncontaminated reference soils and 22 contaminated soils with different physico-chemical properties and contamination patterns were tested with a standardized toxicity test, using the nematode, Caenorhabditis elegans, as test organism. Fertility, growth and reproduction of C. elegans in the soils were compared with the exposure in standard soil Lufa St.2.2. C. elegans showed 100% fertility and a very low variability of growth in the reference soils. Although, reproduction varied considerably between the various reference soils, validity criteria (>30 offspring per test organism) were met in all reference soils. Moreover, Lufa St. 2.2 turned out to be a suitable and representative control soil. In order to clearly classify the effects of the polluted soils on C. elegans, toxicity thresholds were derived for nematode fertility (20% inhibition), growth (10% inhibition) and reproduction (40% inhibition) on the basis of the test inherent variability (MDD=minimal detectable difference), as well as their variability between the uncontaminated reference soils (MTI=maximal tolerable inhibition). The contaminated soils showed clear toxic effects on the nematodes, whereas the toxicity was better correlated to organic than to heavy metal contamination in bulk soil. Interestingly, the results of the nematode toxicity test were not well correlated with those of tests with oligochaetes, collembolans and plants, performed with the same soils, showing that the results are not redundant. The toxicity test using C. elegans turned out to be suitable for testing the toxicity of field collected soils and might by a valuable addition to soil test batteries.     

Bioavailability of Copper and Zinc in Mining Soils

The soil-contact exposure pathway can be the main driver of ecological risk assessments. There is currently no standard method to measure bioavailability of metals in soil to ecological receptors, yet the influence of metal bioavailability on toxicity has been known for decades and is a major factor influencing risk to ecological receptors. Bioavailability is to a large degree governed by varying soil characteristics within and among sites, yet ecological screening benchmarks are often derived on a total-concentration basis. We compared a calcium chloride (CaCl₂) extraction, cyclodextrin extraction, simulated earthworm gut (SEG) test, earthworm kinetic bioaccumulation test, and metal residues in plant tissues with a battery of invertebrate and toxicity tests using mining soils consisting of high organic-matter content cocontaminated with copper (Cu) and zinc (Zn). Earthworm (Eisenia andrei) tissue concentrations of Cu and Zn were regulated and were not predictive of invertebrate toxicity. All chemical measures of bioavailability correlated with several biological responses; however, CaCl₂-extractable Cu and SEG-extractable Cu and Zn best predicted effects to E. andrei. Total Cu concentrations in soil best correlated with effects to plants. Overall, a chemical measure was the best predictor of toxicity to each organism compared with biological measures, although the exact measure was dependent on organism and end point. Chemical-extraction techniques provide relatively quick, inexpensive indicators of essential metal bioavailability compared with biological measures; however, no single measure was indicative of all effects to all organisms.     

Patterns of sensitivity to cadmium and pentachlorophenol among nematode species from different taxonomic and ecological groups

The variation of acute toxicity data among nematode species belonging to different taxonomic and ecological groups was investigated. Twelve different nematode species were extracted from the soil and directly exposed to cadmium and pentachlorophenol. LC₅₀-values were estimated after 24, 48, 72, and 96 h of exposure in aqueous solutions. The species exhibited large differences in sensitivity. LC₅₀-values (72 h) for pentachlorophenol ranged from 0.5 to more than 34.5 mol/L and for cadmium from 29 to more than 800 mol/L. These toxicity data could be described by a log-logistic distribution function.LC₅₀-values for cadmium were not correlated with those for pentachlorophenol. Species of the subphylum Secernentia were less sensitive to pentachlorophenol than species of the subphylum Penetrantia, while no differences were observed for cadmium. In addition, no relationship was found between toxicity data and life-history strategies. Slow colonizers (K-strategists, sensu lato) were not more sensitive to cadmium and pentachlorophenol than opportunistic species (r-strategists, sensu lato). Nematodes appeared to be as sensitive to pentachlorophenol as other soil invertebrates. Nematodes were generally tolerant to cadmium.     

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

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

Effect of loading density on the acute toxicities of surfactants,copper, and phenol toDaphnia magna straus

The effects of various densities ofDaphnia magna on the acute toxicities of three surfactants, and copper, and phenol were evaluated in 48-hr static toxicity tests. LC₅₀ values were determined at six loading densities for each of the test materials. The mean LC₅₀ values (±1 SD) were 4.8 (0.29) mg/L, 0.62 (0.16) mgL and 0.24 (0.10) mg/L for the anionic, nonionic, and cationic surfactants, respectively. Toxicity values for copper averaged 0.026 (0.01) mg/L and those for phenol, 7.7 (2.2) mg/L. For the nonionic surfactant, copper and phenol there was a trend of increasing toxicity with decreasing density. The differences in LC₅₀ values were not biologically significant with the maximum difference being approximately three-fold.     

Toxicity of Select Beta Adrenergic Receptor-Blocking Pharmaceuticals (B-Blockers) on Aquatic Organisms

One class of pharmaceutical compounds identified in U.S. and European waters are the B-adrenergic receptor blocking compounds (B-blockers). However, little information is available on the potential aquatic toxicity of these compounds. Therefore, Hyalella azteca, Daphnia magna, Ceriodaphnia dubia, and Oryias latipes (Japanese medaka) were exposed to metoprolol, nadolol, and propranolol to determine potential toxicity. Average 48-h LC₅₀ for propranolol to H. azteca was 29.8 mg/L. The no-observed-effects concentration (NOEC) and lowest-observed-effects concentration (LOEC) for propranolol affecting reproduction of H. azteca were 0.001 and 0.1 mg/L, respectively. The average propranolol and metoprolol 48-h LC₅₀s for D. magna were 1.6 and 63.9 mg/L, respectively. C. dubia 48-h LC₅₀s were 0.85 and 8.8 mg/L for propranolol and metoprolol, respectively. The NOEC and LOEC of propranolol affecting reproduction in C. dubia were 0.125 and 0.25 mg/L, respectively. In O. latipes, the propranolol 48-h LC₅₀ was 24.3 mg/L. Medaka growth was decreased at 0.5 mg/L propranolol. A 2-week medaka reproductive study indicated significant changes in plasma steroid levels; however, no changes in the average number of eggs produced or number of viable eggs which hatched was observed. In a 4-week follow-up propranolol exposure, the total number of eggs produced by medaka and the number of viable eggs that hatched were decreased at concentrations as low as 0.5 μg/L. Based on this study and the expected aqueous environmental exposure levels, adverse effects of propranolol to invertebrate populations is unlikely; however, further reproductive studies are need to elucidate the risk to teleosts. Received: 14 August 2001/Accepted: 4 March 2002     

Acute Toxicity and Effects Analysis of Endosulfan Sulfate to Freshwater Fish Species

Endosulfan sulfate is a persistent environmental metabolite of endosulfan, an organochlorine insecticide–acaricide presently registered by the United States Environmental Protection Agency. There is, however, limited acute fish toxicity data for endosulfan sulfate. This study determines the acute toxicity (LC₅₀s and LC₁₀s) of endosulfan sulfate to three inland Florida native fish species (mosquitofish [Gambusia affinis]; least killifish [Heterandria formosa]; and sailfin mollies [Poecilia latipinna]) as well as fathead minnows (Pimephales promelas). Ninety-six-h acute toxicity tests were conducted with each fish species under flow-through conditions. For all of the above-mentioned fish species, 96-h LC₅₀ estimates ranged from 2.1 to 3.5 μg/L endosulfan sulfate. The 96-h LC₁₀ estimates ranged from 0.8 to 2.1 μg/L endosulfan sulfate. Of all of the fish tested, the least killifish appeared to be the most sensitive to endosulfan sulfate exposure. The above-mentioned data were combined with previous acute toxicity data for endosulfan sulfate and freshwater fish for an effects analysis. The effects analysis estimated hazardous concentrations expected to exceed 5, 10, and 50% of the fish species’ acute LC₅₀ or LC₁₀ values (HC₅, HC₁₀, and HC₅₀). The endosulfan sulfate freshwater-fish acute tests were also compared with the available freshwater-fish acute toxicity data for technical endosulfan. Technical endosulfan is a mixture of α- and β-endosulfan. The LC₅₀s had a wider range for technical endosulfan, and their distribution produced a lower HC₁₀ than for endosulfan sulfate. The number of freshwater-fish LC₅₀s for endosulfan sulfate is much smaller than the number available for technical endosulfan, reflecting priorities in examining the toxicity of the parent compounds of pesticides. The toxicity test results and effects analyses provided acute effect values for endosulfan sulfate and freshwater fish that might be applied in future screening level ecologic risk assessments. The effects analyses also discussed several deficiencies in conventional methods for setting water-quality criteria and determining ecologic effects from acute toxicity tests.     

Interclonal Variation in the Acute and Delayed Toxicity of Cadmium to the European Prosobranch Gastropod Potamopyrgus antipodarum (Gray)

The lethal responses of three European clones—A, B, and C—of the prosobranch snail Potamopyrgus antipodarum to acute cadmium exposure were examined by the use of a conventional LC₅₀ test and a delayed toxicity test. The questions addressed were: (1) Are there differences in susceptibility (LC₅₀ values and uniformity of response) among the three European clones of P. antipodarum? (2) Are the patterns of differences in susceptibility among clones observed in the LC₅₀ test also observed for the delayed toxicity test? (3) Is there concordance in the ranking of susceptibility among clones under acute cadmium exposure and under chronic cadmium exposure? The results showed that the widths of the tolerance distribution differed among clones. Clones A and B had a steeper slope than clone C (for clone A the difference was marginally significant), which indicates that individuals from clones A and B showed a more uniform response to acute lethal cadmium stress than individuals from clone C. On the basis of the measured differences in LC₅₀ values, clone A individuals showed the highest tolerance to acute cadmium (LC₅₀ value: 1.92 mg Cd L^?1) followed by clone B (LC₅₀ value: 1.29 mg Cd L^?1) and clone C (LC₅₀ value: 0.56 mg Cd L^?1). Clone C was significantly less tolerant than clones A and B. The delayed toxicity test showed a similar pattern to the LC₅₀ test with regard to tolerance differences among clones; however, mortality continued following transfer to clean water, indicating that cadmium was lethal at much lower concentrations than indicated by the conventional LC₅₀ test. Results of the LC₅₀ test and the delayed toxicity test in the present study were in general agreement with results from chronic cadmium exposure experiments (Jensen et al.[2000]Ecol Appl[submitted]), i.e., the least susceptible clone A in the acute cadmium exposure test was also the least susceptible clone in the chronic cadmium exposure test. Based on the dramatic differences between the LC₅₀ and the cadmium exposure concentrations causing delayed toxicity, we suggest that the potential for delayed toxicity should be given greater consideration in ecotoxicity testing.     

A Study of the Lethal and Sublethal Toxicity of Polyphase P-100, an Antisapstain Fungicide Containing 3-Iodo-2-Propynyl Butyl Carbamate (IPBC), on Fish and Aquatic Invertebrates

The acute toxicity of Polyphase P-100, an antisapstain wood preservative that contains 97% 3-iodo-2-propynyl butyl carbamate (IPBC), was determined for three species of fish (coho salmon, rainbow trout, and starry flounder) and three species of aquatic invertebrates (Daphnia magna, Hyalella azteca, and Neomysis mercedis). The 96-h LC₅₀ values for the various fish species exposed to Polyphase P-100 ranged from 95 ppb for coho smolts (Oncorhynchus kisutch) to 370 ppm for juvenile starry flounder (Platichthys stellatus). The sensitivity of coho to Polyphase P-100 was altered by their developmental stage. Coho embryos were six to nine times more tolerant of Polyphase P-100 than coho alevins, which were twice as tolerant as coho smolts. The 48-h LC₅₀ values for the invertebrates D. magna, H. azteca, and N. mercedis were 40 ppb, 500 ppb, and 2,920 ppb, respectively. In addition to a wider range of sensitivity to Polyphase P-100 compared with the fish species, the invertebrate species were characterized by a shallower concentration-response. In acute, 24-h sublethal tests with juvenile starry flounder and rainbow trout, there was no primary or secondary stress response (changes in hematocrit, leucocrit, hemoglobin concentration, plasma lactate concentration, and plasma cortisol concentration) at concentrations up to 50% of the 96-h LC₅₀ value. The acute toxicity of a 1:8 mixture of Polyphase P-100 and Bardac 2280 (another antisapstain compound that contains didecyldimethylammonium chloride [DDAC] as the active ingredient) was close to additive for fish, but not for invertebrate species. The acute toxicity of the mixture was seven to eight times more than additive for H. azteca, but two to three times less than additive for D. magna. Some sublethal stress responses were revealed with the mixture that were not observed with the test chemicals alone. Received: 10 October 1997/Accepted: 28 March 1998     

Ion-selective electrode measurements of copper(II) activity in contaminated soils

A method is presented for the use of a cupric ionselective electrode to determine the free copper activity in 0.01 M CaCl₂ soil solution extracts. Ionic strength variations and the presence of aluminum caused no significant interferences. The method was applied to 18 soils with wide-ranging copper levels. The pCu²⁺ varied between 6.33 and 12.20. Acidic soils have a very high cupric ion activity even though they are not considered to be contaminated with copper. Soils considered contaminated with respect to total copper also have free pCu²⁺ activities below 10, which is close to the toxicity threshold determined in aquatic ecotoxicological studies. All mineral soils have free copper activities close to or below the values expected from pH-dependent soil equilibration studies.     

Utility of Caenorhabditis elegans for Assessing Heavy Metal Contamination in Artificial Soil

There is an increasing need for the development of soil bioassay protocols. Currently the only internationally standardized soil test organism is the lumbricid earthworm Eisenia fetida. Many alternate soil test organisms have been proposed. This work compares Caenorhabditis elegans to several other test organisms, including E. fetida, for heavy metals in soil. In this evaluation, such factors as ease of testing and culturing, duration of testing, soil volume needed, and the sensitivity of the organism were considered. Results show that C. elegans is more sensitive than most other organisms evaluated and is similar in response to E. fetida. The second issue compares C. elegans LC₅₀ values to heavy metals criteria specified in the US EPA regulations for land application of sewage sludge. Currently, the regulations are set on total metals in the soil and do not consider bioavailability of the metals. Regulations do not consider soil physiochemical properties, such as organic matter content, clay content, and cation exchange capacity, which have been shown to affect the availability of metals to soil organisms. While the C. elegans LC₅₀ values are above standard values in artificial soil, work in our lab indicates that the LC₅₀s are below regulation values for other soil types. Due to the ease of culturing and testing, good sensitivity, along with the wealth of biological information and ecological relevance, C. elegans is a good organism for use in soil bioassays. Received: 2 June 1999/Accepted: 13 January 2000     

Comparison of Diazinon Toxicity to Embryos of <Emphasis Type="Italic">Xenopus laevis</Emphasis> and <Emphasis Type="Italic">Danio rerio</Emphasis>; Degradation of Diazinon in Water

The aim of this study was to determine the toxic effect of diazinon (organophosphate insecticide) to embryos of Xenopus laevis and Danio rerio. The 96-h LC₅₀ values showed higher toxicity of diazinon for X. leavis in standard solution (9.84 mg/L) compared to the pond water (12.64 mg/L). Teratogenic index for diazinon was 1.3 and 1.6, respectively. The 96-h LC₅₀ diazinon values demonstrated similar sensitivity of embryos D. rerio (8.21–9.34 mg/L) and X. laevis in standard test solutions. Our results reflect that direct application of diazinon into the water can be associated with significant risks to aquatic organisms.     

Availability of metals to the nematode Caenorhabditis elegans: toxicity based on total concentrations in soil and extracted fractions

Current regulation of metals in soils is based on total metal concentrations rather than on actual exposure concentrations. Considering the extreme variation in soil physicochemical properties, total concentrations are not reflective of the availability and resultant toxicity of metals in different soils. In this study, the availability of Cd, Cu, Ni, Pb, and Zn to the free-living soil nematode Caenorhabditis elegans was assessed after 24-h exposures in three soils using a sequential soil extraction procedure. Albany soil, sampled from southern Georgia, USA, is characterized by a high sand content, whereas Cecil soil from the Piedmont region of Georgia contains higher fractions of clay and organic matter. The final soil was an American Society for Testing and Materials (ASTM) artificial medium composed of peat, kaolin clay, sand, and calcium carbonate. Based on their composition, ASTM medium would sorb metals most strongly and Albany soil the least strongly. In fact, 24-h lethal concentrations to 50% (LC50s) of nematodes for the five metals as determined by the total metal concentration followed this trend. In addition, water-extractable metals were lowest in ASTM medium and highest in Albany soil when spiked at the same concentrations. Our data show the need to consider soil type when performing toxicological tests and establishing site-specific allowable metal concentrations in soil.     

Uptake and toxicity of spiked nickel to earthworm Eisenia fetida in a range of Chinese soils

Bioavailability and toxicity of metals to soil organisms varies among different soils, and knowledge of this variance is useful for the development of soil environmental quality guidelines. In the present study, laboratory experiments were performed to investigate the effects of variations in nickel (Ni) uptake and toxicity on growth, cocoon output, and juvenile production in the earthworm Eisenia fetida in 13 Chinese soils spiked with nickel chloride. Body weight development of E. fetida was rather insensitive to Ni, and significant inhibition of growth was observed only at high Ni concentrations, such as 560 and 1000 mg/kg. The 50% inhibition effect concentrations (EC50s) for cocoon and juvenile production, based on measured Ni concentrations in soils, varied from 169 to 684 mg/kg and from 159 to 350 mg/kg, respectively. The EC50s represented approximately fourfold variation for cocoon output and twofold variation for juvenile production among 13 Chinese soils. Juvenile production, compared to cocoon output, was a more sensitive endpoint parameter to Ni. Nickel uptake in E. fetida increased as simple linear functions of increasing soil Ni concentrations. Tissue Ni-based EC50s (based on Ni concentrations in earthworm tissues) for cocoon production varied from 37 to 121 mg/kg (threefold variation) in 12 of 13 soils, suggesting a similar variation to that of soil Ni-based EC50s. Relationship analysis between soil properties and Ni toxicity showed that neither the EC50s for cocoon output nor those for juvenile production presented significant correlation with soil properties (pH, organic matter content, cation exchange capacity, clay content, Ca2? and Mg2?). This may be ascribed to the narrow range of properties of selected soils. The soil factors that determined Ni toxicity to earthworm reproduction remain undetermined in the present study, and these data should be used cautiously when developing toxicity prediction models because of the narrow selection of soil properties.     

Monitoring the sensitivity of the oligochaete Tubifex tubifex in laboratory cultures using three toxicants

Acute toxicity tests were conducted to assess the sensitivity of laboratory cultured Tubifex tubifex (Annelida, Clitellata), as an intralaboratory quality assurance requirement for the test organisms used in sediment chronic bioassays. Worms were exposed to cadmium, copper, and chromium in water-only 96-h tests, in single metal exposure, over a three-year period. The lethal concentration for the x% of the exposed population (LC_x), the No-Observable-Effect Concentration (NOEC) and the Lowest-Observable-Effect Concentration (LOEC) were estimated. Based on LC₅₀ values, the rank of toxicity was Cu⁺²>Cd⁺²>Cr⁺⁶. Sensitivity remained relatively constant during the research period and was comparable with the sensitivity of the same culture stock examined more than 10 years ago. This observed consistency in sensitivity indicates that comparisons between different sediment chronic bioassays conducted during the study period, using T. tubifex worms from the same culture stock, was appropriate. It is necessary to control both worm biomass and age for the acute test in order to standardize the test-organism conditions in intralaboratory quality assurance programs.