Edward F. Neuhauser

Bioconcentration and biokinetics of heavy metals in the earthworm

This study examines the steady state and non-steady state kinetics of five metals, cadmium, copper, lead, nickel, and zinc in earthworms. The steady state kinetics are based on field studies in which worms from contaminated and uncontaminated sites were collected and measurements were made of concentrations in the earthworms and soils. For each of the metals, evidence suggests that bioconcentration depends on the metal concentrations in the soil; bioconcentration is greater at lower soil concentrations. The studies of non-steady state kinetics involve uptake and elimination experiments in which worms are transferred from an uncontaminated soil to a contaminated soil (uptake studies) or from a contaminated soil to an uncontaminated soil (elimination studies). The voiding time is shown to be an important experimental variable in determining the measured levels of metal in earthworms because experimental measurements are usually made on a worm-soil complex (i.e. the soft tissue of the worm and the soil in the gut of the worm). Thus, for metals that are bioconcentrated in worm tissue, increasing the voiding period increases the concentration of the metal in the worm-soil complex. Conversely, for metals that are not bioconcentrated, increasing the voiding time leads to a decrease in concentrations in the worm-soil complex.

PAH loss during bioremediation of manufactured gas plant site soils

Abstract This research investigated loss of polynuclear aromatic hydrocarbons (PAH) while attempting to bioremediate soils from a manufactured gas plant (MGP) site. Laboratory microcosms using site soils were used to evaluate how environmental factors, such as temperature, pH and nutrients affected PAH loss. Results indicated that: (a) PAH in the MGP site soil resisted mineralization by microorganisms; (b) test soils were non-toxic before and after testing; (c) significant populations of bacteria were present in the microcosms during the degradation studies; (d) addition of free naphthalene and phenanthrene to the soils resulted in rapid loss of the added chemicals while the concentrations of indigenous chemicals were unchanged; (e) PAH were not soluble in a water extract of these soils; and (f) the PAH in these soils were unavailable for microbial degradation.

Growth and reproduction of the earthworm Eisenia fetida exposed to sublethal concentrations of organic chemicals.

Abstract The determination of a short-term LC 50 toxicity value for a chemical is a useful indicator of the potential biological effect of the chemical if released into the environment. However, it is possible that adverse effects of the chemical may occur at sublethal concentrations far below LC 50 values. Using the earthworm Eisenia fetida (Savigny) as an indicator organism for soil ecosystems, concentrations of 10 organic chemicals were evaluated for sublethal effects on earthworm growth and reproduction. Following short-term exposure to sublethal concentrations of carbaryl and dicldrin, E. fetida was allowed to resume growth and reproduction to determine whether such effects were permanent. The effect on earthworm populations as a representative soil organism could be a sentinel for the effects of more destructive soil processes.

Subsurface ecosystem resilience: long-term attenuation of subsurface contaminants supports a dynamic microbial community

The propensity for groundwater ecosystems to recover from contamination by organic chemicals (in this case, coal-tar waste) is of vital concern for scientists and engineers who manage polluted sites. The microbially mediated cleanup processes are also of interest to ecologists because they are an important mechanism for the resilience of ecosystems. In this study we establish the long-term dynamic nature of a coal-tar waste-contaminated site and its microbial community. We present 16 years of chemical monitoring data, tracking responses of a groundwater ecosystem to organic contamination (naphthalene, xylenes, toluene, 2-methyl naphthalene and acenaphthylene) associated with coal-tar waste. In addition, we analyzed small-subunit (SSU) ribosomal RNA (rRNA) genes from two contaminated wells at multiple time points over a 2-year period. Principle component analysis of community rRNA fingerprints (terminal-restriction fragment length polymorphism (T-RFLP)) showed that the composition of native microbial communities varied temporally, yet remained distinctive from well to well. After screening and analysis of 1178 cloned SSU rRNA genes from Bacteria, Archaea and Eukarya, we discovered that the site supports a robust variety of eukaryotes (for example, alveolates (especially anaerobic and predatory ciliates), stramenopiles, fungi, even the small metazoan flatworm, Suomina) that are absent from an uncontaminated control well. This study links the dynamic microbial composition of a contaminated site with the long-term attenuation of its subsurface contaminants.

Supercritical carbon dioxide extraction as a predictor of polycyclic aromatic hydrocarbon bioaccumulation and toxicity by earthworms in manufactured-gas plant site soils

The toxicity and uptake of polycyclic aromatic hydrocarbons (PAHs) by earthworms were measured in soil samples collected from manufactured-gas plant sites having a wide range in PAH concentrations (170-42,000 mg/kg) and soil characteristics. Samples varied from vegetated soils to pure lampblack soot and had total organic carbon contents ranging from 3 to 87%. The biota-soil accumulation factors (BSAFs) observed for individual PAHs in field-collected earthworms (Aporrectodea caliginosa) were up to 50-fold lower than the BSAFs predicted using equilibrium-partitioning theory. Acute toxicity to the earthworm Eisenia fetida was unrelated to total PAH concentration: Mortality was not observed in some soils having high concentrations of total PAHs (>42,000 mg/kg), whereas 100% mortality was observed in other soils having much lower concentrations of total PAHs (1,520 mg/kg). Instead, toxicity appeared to be related to the rapidly released fraction of PAHs determined by mild supercritical CO2 extraction (SFE). The results demonstrate that soils having approximately 16,000 mg rapidly released total PAH/kg organic carbon can be acutely toxic to earthworms and that the concentration of PAHs in soil that is rapidly released by SFE can estimate toxicity to soil invertebrates.

Greatly reduced bioavailability and toxicity of polycyclic aromatic hydrocarbons to Hyalella azteca in sediments from manufactured‐gas plant sites

The toxicity of polycyclic aromatic hydrocarbons (PAHs) to Hyalella azteca, was measured in 34 sediment samples collected from four manufactured-gas plant (MGP) sites ranging in total PAH16 (sum of 16 U.S. Environmental Protection Agency priority pollutant PAHs) concentrations from 4 to 5700 mg/kg, total organic carbon content from 0.6 to 11%, and soot carbon from 0.2 to 5.1%. The survival and growth of H. azteca in 28-d bioassays were unrelated to total PAH concentration, with 100% survival in one sediment having 1,730 mg/kg total PAH16, whereas no survival was observed in sediment samples with concentrations as low as 54 mg/kg total PAH16. Twenty-five of the 34 sediment samples exceeded the probable effects concentration screening value of 22.8 mg/kg total PAH13 (sum of 13 PAHs) and equilibrium partitioning sediment benchmarks for PAH mixtures (on the basis of the measurement of 18 parent PAHs and 16 groups of alkylated PAHs, [PAH34]); yet, 19 (76%) of the 25 samples predicted to be toxic were not toxic to H. azteca. However, the toxicity of PAHs to H. azteca was accurately predicted when either the rapidly released concentrations as determined by mild supercritical fluid extraction (SFE) or the pore-water concentrations were used to establish the bioavailability of PAHs. These results demonstrate that the PAHs present in many sediments collected from MGP sites have low bioavailability and that both the measurement of the rapidly released PAH concentrations with mild SFE and the dissolved pore-water concentrations of PAHs are useful tools for estimating chronic toxicity to H. azteca.

Acute Effects of Potassium on Filtration Rates of Adult Zebra Mussels, Dreissena polymorpha

Valve response and filtration rates of adult zebra mussels, Dreissena polymorpha, exposed to elevated levels of K+ were assessed to determine the efficacy of using K+ in conjunction with a biocide to control mussel infestations. Mussels, 10 to 15 mm total shell length, were exposed to K+ at concentrations ranging from ambient to 2.00 mmol/L for 3, 6, 12, and 24 h at temperatures of 12 and 22°C. After exposure, each mussel was tested for valve response by tactile stimulation and filtration rate was estimated by clearance of latex microspheres from test solutions during a 30 minute period. Responsiveness was not affected in mussels exposed to ″ 1.00 mmol/L K+ for up to 24 h. Valve closure, however, was inhibited in ≥ 92% of the mussels after exposure to 2.00 mmol/L K+ for ≥ 12 h. Thus, the use of K+ to inhibit valve closure in mussels during the application of some biocides may increase contact time between the biocide and the soft tissues of mussels. Filtration rates of mussels, however, decreased as the K+ concentration increased from 0.50 to 2.00 mmol/L. At the K+ concentration that inhibited valve closure (2.00 mmol/L), filtration rates of mussels were > 90% lower than mussels at ambient K+ levels suggesting less biocide may be drawn in the mantle cavity to act on susceptible tissues. Therefore, use of K+ to prevent valve closure during the application of a biocide may not enhance the efficacy of the biocide due to the inhibitory effects of K+ on filtration. Furthermore, facilities treated with K+ at levels necessary to prevent valve closure may threaten native bivalve populations.

Combined use of heat and oxidants for controlling adult zebra mussels

Abstract The results of an experimental study are presented that demonstrate the use of chlorine or ozone to control zebra mussels at temperatures from 30 to 36°C. Control studies were conducted with no oxidant present. Three acclimation temperature ranges were tested: 0–5, 10–15, and 20–25°C. Chlorine was tested at 0.1 and 0.5 mg/L; ozone at 0.5 mg/L. Mortality was described by a cumulative normal distribution, from which times to 95% mortality were estimated and used as a dependent variable for hypothesis testing. Study results showed that the addition of chlorine or ozone was more effective than heat alone at test temperatures above 30°C. Compared to heat alone, the combined use of heat and oxidants decreased the time to 95% mortality by more than 95% at 30°C. Above 30°C, the benefits of the combined treatment strategy decreased with increasing test temperature. At 36°C, the benefits of the combined treatment strategy over heat alone were minimal. Acclimation temperature was important only for heat alone and for mussels acclimated at 0–5°C. The addition of chlorine or ozone at elevated temperatures can reduce mortality times by as much as three orders of magnitude compared to oxidant addition at ambient temperatures. The results of the study should be of significance to power plants or industries where excess heat is available to raise water temperatures.

An evaluation of the ability of chemical measurements to predict polycyclic aromatic hydrocarbon‐contaminated sediment toxicity to Hyalella azteca

The present study examined the ability of three chemical estimation methods to predict toxicity and nontoxicity of polycyclic aromatic hydrocarbon (PAH) -contaminated sediment to the freshwater benthic amphipod Hyalella azteca for 192 sediment samples from 12 field sites. The first method used bulk sediment concentrations of 34 PAH compounds (PAH34), and fraction of total organic carbon, coupled with equilibrium partitioning theory to predict pore-water concentrations (KOC method). The second method used bulk sediment PAH34 concentrations and the fraction of anthropogenic (black carbon) and natural organic carbon coupled with literature-based black carbon-water and organic carbon-water partition coefficients to estimate pore-water concentrations (KOCKBC method). The final method directly measured pore-water concentrations (pore-water method). The U.S. Environmental Protection Agencys hydrocarbon narcosis model was used to predict sediment toxicity for all three methods using the modeled or measured pore-water concentration as input. The KOC method was unable to predict nontoxicity (83% of nontoxic samples were predicted to be toxic). The KOCKBC method was not able to predict toxicity (57% of toxic samples were predicted to be nontoxic) and, therefore, was not protective of the environment. The pore-water method was able to predict toxicity (correctly predicted 100% of the toxic samples were toxic) and nontoxicity (correctly predicted 71% of the nontoxic samples were nontoxic). This analysis clearly shows that direct pore-water measurement is the most accurate chemical method currently available to estimate PAH-contaminated sediment toxicity to H. azteca.

Land treatment of an aged oily sludge-organic loss and change in soil characteristics

Abstract Land treatment of an aged oily sludge was investigated to determine the loss of organic constituents. The oily sludge was applied to field plots of a moderately permeable silt loam soil. The plots consisted of four replicates each of natural controls, rototilled controls and several application rates. Sludge was applied at three different timers over a two-year period and at seven sludge application rates that ranged from 0.09 to 5.25% oil and grease by weight in the soil zone of incorporation. Application of the sludge increased the pH, temperature and volatile matter of the soil. The half-life of the total oil and grease ranged from about 260 to about 400 days. Naphthalenes, alkanes and specific aromatics were rapidly lost from the soil. The half-life of these compounds generally was less than 30 days. Not all of the applied organics were lost. A refractory component of about 20–25% of the applied oil and grease accumulated in the soil. Based on laboratory earthworm studies, the residual organics did not appear to have a permanent adverse impact to the soil biota.