Two Pilot Plant Reactors Designed for the In Situ Bioremediation of Chlorobenzene-contaminated Ground Water: Hydrogeological and Chemical Characteristics and Bacterial Consortia

The SAFIRA in situ pilot plant in Bitterfeld, Saxonia-Anhalt, Germany, currently serves as the test site for eight different in situ approaches to remediate anoxic chlorobenzene (CB)-contaminated ground water. Two reactors, both filled with originallignite-containing aquifer material, are designed for themicrobiological in situ remediation of the ground water bythe indigenous microbial consortia. In this study, thehydrogeological, chemical and microbiological conditions of theinflowing ground water and reactor filling material are presented,in order to establish the scientific basis for the start of thebioremediation process itself. The reactors were put intooperation in June 1999. In the following, inflow CB concentrationsin the ground water varied between 22 and 33 mg L^-1; achemical steady state for CB in both reactors was reachedafter 210 till 260 days operation time. The sediments werecolonized by high numbers of aerobic, iron-reducing anddenitrifying bacteria, as determined after 244 and 285 days ofoperation time. Furthermore, aerobic CB-degrading bacteria weredetected in all reactor zones. Comparative sequence analysis of16S rDNA gene clone libraries suggest the dominance of Proteobacteria (Comamonadaceae, Alcaligenaceae, Gallionella group, Acidithiobacillus) and members of theclass of low G+C gram-positive bacteria in the reactorsediments. In the inflowing ground water, sequences withphylogenetic affiliation to sulfate-reducing bacteria andsequences not affiliated with the known phyla of Bacteria, were found.     

General equilibrium benefits for environmental improvements: projected ozone reductions under EPA's Prospective Analysis for the Los Angeles air basin

This research demonstrates how locational equilibrium models can be used for benefit measurement with the detail required to match EPA's benefit analysis for the first Prospective Analysis. Using the projected changes in ozone concentrations for 2000 and 2010 together with the Sieg et al. (Int. Econ. Rev., forthcoming) estimates for household preferences for housing, education, and air quality, this paper measures general equilibrium willingness to pay for the policy scenarios developed for the Prospective study as they relate to households in the Los Angeles area. Benefits are evaluated taking account (at the household level) of initial air quality conditions, relocation based on changes in ozone, and price changes. The framework generalizes the partial equilibrium/general equilibrium comparisons available with conventional computable general equilibrium and property capitalization models. Estimated general equilibrium gains from the policy range from $33 to $2400 annually at a household level (in 1990 dollars).     

Sorption of naphthalene derivatives to soils from a long-term field experiment

The influence of long-term farming practices on the soil's behaviour to adsorb hydrophobic organic compounds (HOCs) over long times was investigated. Adsorption of five naphthalene derivatives (naphthalene, 1-naphthol, 1-naphthylamine, 1-hydroxy-2-naphthoic acid, 1,4-naphthoquinone) was examined on soils with varying amounts and origins of soil organic matter obtained after amendment with different organic materials over more than 40 years. Soil organic matter, pore sizes and aggregate stability were significantly altered influencing the adsorption behaviour of the soils. Samples of soil amended with peat having an organic carbon content of 3.4% sorbed naphthalene derivatives stronger than the soil treated with sewage sludge (2.6% C(org)). All other treatments, calcium nitrate, plots without nitrogen fertilizers, grassland, animal manure, green manure and the fallowed soil sorbed less and no significant difference was found between them although the organic carbon content ranged from 1.0% to 2.6%. Thus, a decrease of the carbon content of a soil does not necessarily imply a reduction of sorption capacities for hydrophobic compounds such as naphthalene derivatives. Furthermore, the importance of protonation of HOCs for the adsorption on soil surfaces was shown. Different polarities of electronic structures of HOCs distinctly influence their adsorption behaviour.     

Estimating reduction of nitrogen leaching from arable land and the related costs

The EU Water Framework Directive will require river-basin management plans in order to achieve good ecological status and find the most cost-efficient nitrogen (N) leaching abatement measures. Detailed scenario calculations based on modeling methods will be valuable in this regard. This paper describes the approach and an application with a coefficient method based on the simulation model SOILNDB for quantification of N leaching from arable land and for prediction of the effect of abatement scenarios for the R?nne? catchment (1900 km2) in southern Sweden. Cost calculations for the different measures were also performed. The results indicate that the individual measures-cover crop and spring plowing, late termination of ley and fallow, and spring application of manure-would only reduce N leaching by between 5% and 8%. If all measures were combined and winter crops replaced by their corresponding spring variants, a 21% reduction in N leaching would be possible. However, this would require total fulfillment of the suggested measures.     

Tympanal mechanics and neural responses in the ears of a noctuid moth

Ears evolved in many groups of moths to detect the echolocation calls of predatory bats. Although the neurophysiology of bat detection has been intensively studied in moths for decades, the relationship between sound-induced movement of the noctuid tympanic membrane and action potentials in the auditory sensory cells (A1 and A2) has received little attention. Using laser Doppler vibrometry, we measured the velocity and displacement of the tympanum in response to pure tone pulses for moths that were intact or prepared for neural recording. When recording from the auditory nerve, the displacement of the tympanum at the neural threshold remained constant across frequencies, whereas velocity varied with frequency. This suggests that the key biophysical parameter for triggering action potentials in the sensory cells of noctuid moths is tympanum displacement, not velocity. The validity of studies on the neurophysiology of moth hearing rests on the assumption that the dissection and recording procedures do not affect the biomechanics of the ear. There were no consistent differences in tympanal velocity or displacement when moths were intact or prepared for neural recordings for sound levels close to neural threshold, indicating that this and other neurophysiological studies provide good estimates of what intact moths hear at threshold.     

Demobilisation of critical contaminants in four typical waste-to-energy ashes by carbonation

Two bottom ashes, one air pollution control (APC) residue and one fly ash from three different Swedish municipal solid waste incineration (MSWI) plants were characterised regarding the leaching of environmentally relevant components. Characterisation was performed using a diffusion tank leaching test. The impact of carbonation on the release of eight critical components, i.e., Cl(-), Cr, Cu, Mo, Pb, Sb, Se, SO(4)(2-) and Zn, was assessed at a lab-scale and showed carbonation to have a more pronounced demobilising effect on critical components in bottom ashes than in APC residue and fly ash. From grate type incinerator bottom ash, the release of Cr decreased by 97%, by 63% for Cu and by 45% for Sb. In the investigated APC residue, the releases of Cr, Se and Pb were defined as critical, although they either remained unaffected or increased after carbonation. Cl(-) and SO(4)(2-) remained mobile after carbonation in all investigated residues.     

Concentrations and speciation of arsenic in groundwater polluted by warfare agents

Groundwater polluted with phenylarsenicals from former warfare agent deposits and their metabolites was investigated with respect to the behavior of relevant arsenic species. Depth profiles at the estimated source and at about 1 km downgradient from the source zone were sampled. The source zone is characterized by high total arsenic concentrations up to 16 mg L⁻¹ and is dominated by organic arsenic compounds. The concentrations in the downgradient region are much lower (up to 400 μg L⁻¹) and show a high proportion of inorganic arsenic species. Iron precipitation seems to be an effective mechanism to prevent dispersion of inorganic arsenic as well as phenylarsonic acid. Reductive conditions were observed in the deeper zone with predominant occurrence of trivalent arsenic species. The inorganic species are in redox equilibrium, whereas the phenylarsenic compounds have variable proportions. Methylphenylarsinic acid was identified in groundwater in traces which indicates microbial degradation activity.     

Sorption of thallium(I) onto geological materials: influence of pH and humic matter

The sorption behaviour of the severely toxic heavy metal thallium (Tl) as a monovalent cation onto three representative materials (goethite, pyrolusite and a natural sediment sampled from a field site) was examined as a function of pH in the absence and presence of two natural humic acids (HAs), using ²⁰⁴Tl(I) as a radiotracer. In order to obtain a basic understanding of trends in the pH dependence of Tl(I) sorption with and without HA, sorption of HAs and humate complexation of Tl(I) as a function of pH were investigated as well. In spite of the low complexation between Tl(I) and HAs, the presence of HAs results in obvious alterations of Tl(I) sorption onto pyrolusite and sediment. An influence on Tl(I) sorption onto goethite was not observed. Predictions of K_d (distribution coefficient) for Tl(I) on goethite in the presence of HAs, based on a linear additive model, agree well with the experimental data, while a notable disagreement occurs for the pyrolusite and sediment systems. Accordingly, it is suggested that HAs and goethite may act as a non-interacting sorbent mixture under the given conditions, but more complex interactions may take place between the HAs and the mineral phases of pyrolusite or sediment.     

Is colloid-facilitated phosphorus leaching triggered by phosphorus accumulation in sandy soils?

The leaching of colloidal phosphorus (P(coll)) contributes to P losses from agricultural soils. In an irrigation experiment with undisturbed soil columns, we investigated whether the accumulation of P in soils due to excess P additions enhances the leaching of colloids and P(coll) from sandy soils. Furthermore, we hypothesized that large concentrations of P(coll) occur at the onset of leaching events and that P(coll) mobilized from topsoils is retained in subsoils. Soil columns of different P saturation and depth (0-25 and 0-40 cm) were collected at a former disposal site for liquid manure and at the Thyrow fertilization experiment in northeastern Germany. Concentrations of total dissolved P, P(coll), Fe(coll), Al(coll), optical density, zeta potential, pH, and electrical conductivity of the leachates were determined. Colloidal P concentrations ranged from 0.46 to 10 micromol L(-1) and contributed between 1 and 37% to total P leaching. Large P(coll) concentrations leached from the P-rich soil of the manure disposal site were rather related to a large P-content of colloids than to the mobilization of additional colloids. Concentrations of colloids and P(coll) in leachates from P-poor and P-rich columns from Thyrow did not differ significantly. In contrast, accumulation of P in the Werbellin and the Thyrow soil consistently increased dissolved P concentrations to maximum values as high as 300 micromol L(-1). We observed no first-flush of colloids and P(coll) at the beginning of the leaching event. Concentrations of P(coll) leached from 40-cm soil columns were not smaller than those leached from 25-cm columns. Our results illustrate that an accumulation of P in sandy soils does not necessarily lead to an enhanced leaching of colloids and P(coll), because a multitude of factors independent from the P status of soils control the mobility of colloids. In contrast, P accumulation generally increases dissolved P concentrations in noncalcareous soils due to the saturation of the P sorption capacity. This indicates that leaching of dissolved P might be a more widespread environmental problem in areas with P-saturated sandy soils than leaching of P(coll).