Partitioning gas tracer tests for measurement of water in municipal solid waste

A key component in the operation of almost all bioreactor landfills is the addition of water to maintain optimal moisture conditions. To determine how much water is needed and where to add it, in situ methods are required to measure water within solid waste. Existing technologies often result in measurements of unknown accuracy, because of the variability of solid waste materials and time-dependent changes in packing density, both of which influence most measurement methods. To overcome these problems, a new technology recently developed by hydrologists for measuring water in the vadose zone--the partitioning gas tracer test--was tested. In this technology, the transport behavior of two gas tracers within solid waste is used to measure the fraction of the void space filled with water. One tracer is conservative and does not react with solids or liquids, while a second tracer partitions into the water and is separated from the conservative tracer during transport. This technology was tested in four different solid waste packings and was capable of determining the volumetric water content to within 48% of actual values, with most measurement errors less than 15%. This technology and the factors that affect its applicability to landfills are discussed in this paper.     

Determination of atrazine in rainfall and surface water by enzyme immunoassay

Rainwater and surface water from four sites in Germany (Bavaria and Lower Saxony) were analyzed for atrazine by enzyme immunoassay from June 1990 until October 1992. The limit of quantification of the immunoassay was 0.02 μg/L with a middle of the test at 0.2 μg/L. About 60 % of the samples contained measurable amounts of atrazine. Seasonal trends were observed, with the highest concentration in the summer months of up to 4 μg/L for rainwater and up to 15 μg/L for surface waters. The highest concentrations were found in agricultural areas, while in the investigated national parks up to 0.56 μg/L could be detected in rain water. This points to long-range atmospheric transport from agricultural areas to pristine national parks. Samples from forest stands usually showed higher atrazine concentrations than samples from open fields. Deposition rates of 10 – 50 μg/m² · yr were observed in the national parks and 10–180 μg/m² · yr at the agricultural sites. Comparison of results obtained by enzyme immunoassay and GC/MS showed a good correlation of r = 0.95.     

4-n-Nonylphenol and 17-beta estradiol may induce common DNA effects in developing barnacle larvae

There is a growing concern over the potential effects of environmental endocrine disrupters on both human and wildlife populations. However, to date, minimal research has been conducted to determine the effect of estrogens and xenoestrogens at the DNA level. In this study, we used the random amplified polymorphic DNA (RAPD) assay to evaluate the effects on the genomic DNA of barnacle larvae that had been exposed to 17beta-estradiol (E2) and low concentrations of 4-n-nonylphenol (NP). DNA effects include DNA damage as well as mutations and possibly other effects at the DNA level that can be induced by chemical or physical agents that directly and/or indirectly interact with genomic DNA. Not only did exposure to NP and E2 induce changes in RAPD profiles in the exposed barnacle larvae when compared to control patterns, but also, and more importantly, there were similarities in the RAPD modifications in the exposed populations that had been treated to either chemical. We propose that NP and E2 induced some common DNA effects in barnacle larvae and that these specific modifications in RAPD patterns may arise as a consequence of hot spot DNA damage (e.g. DNA adducts) and/or mutations (point mutations or genomic rearrangements). This could help to explain how xenoestrogens mimic the effects produced by natural estrogens. In conclusion, in the field of endocrine disruption, the study of DNA effects induced by estrogens and/or xenoestrogens warrants further investigation. Indeed, changes at the DNA levcl may be the precursors of some of the numerous effects reported at higher levels of biological organisation such as the feminization of males, developmental abnormalities, and infertility.     

Nitrogen fluxes on an intensive investigation plot in the North Tyrolean limestone Alps

In the framework of this study, nitrogen fluxes on a limestone site are investigated. The major goals are the assessment of the nitrogen status, the estimation of the nitrogen budget and the evaluation of the nitrogen saturation. The investigation area, the intensive investigation plot and the research equipment are described.     

Atrazine induction of a family 4 cytochrome P450 gene in Chironomus tentans (Diptera: Chironomidae)

Cytochrome P450-dependent microsomal monooxygenase (P450) activity was measured in control and atrazine-exposed third instar midge larvae, Chironomus tentans. Significantly elevated O-demethylase activity was observed in gut homogenates taken from midges exposed to atrazine concentrations from 1 to 10 ppm for 90 h. No significant induction was observed at atrazine concentrations below 1 ppm. A region of a cytochrome P450 family 4 gene was amplified and sequenced from C. tentans larvae. Alignments of inferred amino acid sequences with other insect CYP4 gene homologues indicate a high degree of similarity. Northern blot analysis employing the CYP4 gene fragment as a probe showed an over-expression in C. tentans exposed to atrazine. The results support the previously identified inducibility of cytochrome P450-dependent activity and provide insight into the potential consequences of atrazine exposure to aquatic organisms.     

The influence of humic acids on the phytoextraction of cadmium from soil

Cadmium poses a major environmental and human health threat because of its constant release through anthropogenic activities. A need, therefore, exists for cost-effective remediation procedures. Phytoremediation, the use of plants to extract contaminants from soils and groundwater, has revealed great potential. However, it is limited by the fact that plants need time, nutrient supply and, moreover, have a limited metal uptake capacity. Synthetic chelators have shown positive effects in enhancing heavy metal extraction through phytoremediation, but they have also revealed a vast number of negative side-effects. The objective of this research was to investigate the use of humic acids as an alternative to synthetic chelators. Humic acids were applied to a cadmium-contaminated soil at various dosages, and the uptake of cadmium into Nicotiana tabacum SR-1 was determined in relation to the amounts of total and bioavailable cadmium in the soil. It was found that the theoretical bioavailability of cadmium, as determined by diethylenetriaminepentaacetic acid (DTPA) extraction, did not change, but its plant uptake was enhanced significantly, in some cases up to 65%. Humic acids added at a rate of 2 g kg(-1) soil increased the cadmium concentration in the shoots from 30.9 to 39.9 mg kg(-1). A possible reason for this enhancement is the decrease in pH, resulting in higher cadmium availability. Another possibility taken into account is that plants may take up cadmium complexes with humic acid fragments, which result from microbiological degradation or, self-dissociation.     

Assessment of contaminant lability during phytoremediation of polycyclic aromatic hydrocarbon impacted soil

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant compounds, some of which are known carcinogens, often found in high residual soil concentrations at industrial sites. Recent research has confirmed that phytoremediation holds promise as a low-cost treatment method for PAH contaminated soil. In this study, the lability of soil bound PAHs in the rhizosphere was estimated using solid phase extraction resin. An extraction time of 14 days was determined to be appropriate for this study. Resin-extractable PAHs, which are assumed to be more bioavailable, decreased during plant treatments. Significant reductions in the labile concentrations of several PAH compounds occurred over 12 months of plant growth. The differences in concentration between the unplanted and the planted soil indicate that the presence of plant roots, in addition to the passage of time, contributes to reduction in the bioavailability of target PAHs.     

Hydrochemical and isotopic effects associated with petroleum fuel biodegradation pathways in a chalk aquifer

Hydrochemical data, compound specific carbon isotope analysis and isotopic enrichment trends in dissolved hydrocarbons and residual electron acceptors have been used to deduce BTEX and MTBE degradation pathways in a fractured chalk aquifer. BTEX compounds are mineralised sequentially within specific redox environments, with changes in electron acceptor utilisation being defined by the exhaustion of specific BTEX components. A zone of oxygen and nitrate exhaustion extends approximately 100 m downstream from the plume source, with residual sulphate, toluene, ethylbenzene and xylene. Within this zone complete removal of the TEX components occurs by bacterial sulphate reduction, with sulphur and oxygen isotopic enrichment of residual sulphate (epsilon(s) = -14.4 per thousand to -16.0 per thousand). Towards the plume margins and at greater distance along the plume flow path nitrate concentrations increase with delta15N values of up to +40 per thousand indicating extensive denitrification. Benzene and MTBE persist into the denitrification zone, with carbon isotope enrichment of benzene indicating biodegradation along the flow path. A Rayleigh kinetic isotope enrichment model for 13C-enrichment of residual benzene gives an apparent epsilon value of -0.66 per thousand. MTBE shows no significant isotopic enrichment (delta13C = -29.3 per thousand to -30.7 per thousand) and is isotopically similar to a refinery sample (delta13C = -30.1 per thousand). No significant isotopic variation in dissolved MTBE implies that either the magnitude of any biodegradation-induced isotopic fractionation is small, or that relatively little degradation has taken place in the presence of BTEX hydrocarbons. It is possible, however, that MTBE degradation occurs under aerobic conditions in the absence of BTEX since no groundwater samples were taken with co-existing MTBE and oxygen. Low benzene delta13C values are correlated with high sulphate delta34S, indicating that little benzene degradation has occurred in the sulphate reduction zone. Benzene degradation may be associated with denitrification since increased benzene delta13C is associated with increased delta15N in residual nitrate. Re-supply of electron acceptors by diffusion from the matrix into fractures and dispersive mixing is an important constraint on degradation rates and natural attenuation capacity in this dual-porosity aquifer.     

Characterization of metal adsorption kinetic properties in batch and fixed-bed reactors

Copper adsorption kinetic properties in batch and fixed-bed reactors were studied in this paper. The isothermal adsorption experiments showed that the copper adsorption capacity of a granular activated carbon (Filtrasorb 200) increased when ionic strength was higher. The presence of EDTA diminished the adsorption. An intraparticle diffusion model and a fixed-bed model were successfully used to describe the batch kinetic and fixed-bed operation behaviors. The kinetics became faster when the solution pH was not controlled, implying that the surface precipitation caused some metal uptake. The external mass transfer coefficient, the diffusivity and the dispersion coefficient were obtained from the modeling. It was found that both external mass transfer and dispersion coefficients increased when the flow rate was higher. Finally effects of kinetic parameters on simulation of fixed-bed operation were conducted.     

Mechanism of effective nocardioform foam control measures for non-selector activated sludge systems.

Solids retention time (SRT), biological scum trapping and recycle, and the dynamic equilibrium between Nocardioform populations in the foam and the mixed liquor are the controlling factors in activated sludge foaming events caused by Nocardioform bacteria. For the operating modes described in this paper, a cured mixed liquor foaming condition (filament counts of approximately 10(5) intersections/g volatile suspended solids) was only achieved when SRT control, selective wasting, and polymer addition were in effect. Solids retention time control, with the SRT remaining below 1.5 days, and selective wasting will cure a severely foaming mixed liquor, but effects will only be observed after 3 or 4 months after implementation. The combined wastage of Nocardioform bacteria from selective wasting and SRT control can ensure long-term foam control to the operation of a pure-oxygen activated sludge system with foam-trapping features. An SRT of 0.3 days will result in the complete washout of Nocardioform bacteria from the activated sludge system, which can then operate at an SRT of 3 days free of Nocardioform. Polymer addition to mixed liquor is only effective for foam control when a large portion of the system biomass exists as a heavy layer of foam above the mixed liquor.