Observations on the methane oxidation capacity of landfill soils

The objective of this study was to determine the role of CH₄ loading to a landfill cover in the control of CH₄ oxidation rate (g CH₄ m⁻² d⁻¹) and CH₄ oxidation efficiency (% CH₄ oxidation) in a field setting. Specifically, we wanted to assess how much CH₄ a cover soil could handle. To achieve this objective we conducted synoptic measurements of landfill CH₄ emission and CH₄ oxidation in a single season at two Southeastern USA landfills. We hypothesized that percent oxidation would be greatest at sites of low CH₄ emission and would decrease as CH₄ emission rates increased. The trends in the experimental results were then compared to the predictions of two differing numerical models designed to simulate gas transport in landfill covers, one by modeling transport by diffusion only and the second allowing both advection and diffusion. In both field measurements and in modeling, we found that percent oxidation is a decreasing exponential function of the total CH₄ flux rate (CH₄ loading) into the cover. When CH₄ is supplied, a cover’s rate of CH₄ uptake (g CH₄ m⁻² d⁻²) is linear to a point, after which the system becomes saturated. Both field data and modeling results indicate that percent oxidation should not be considered as a constant value. Percent oxidation is a changing quantity and is a function of cover type, climatic conditions and CH₄ loading to the bottom of the cover. The data indicate that an effective way to increase the % oxidation of a landfill cover is to limit the amount of CH₄ delivered to it.     

Discharge From the Edwards Aquifer Through the Leona River Floodplain,Uvalde, Texas1

Abstract: Analysis of results from an electrical resistivity survey, a magnetic survey, and an aquifer test performed on the Leona River floodplain in south‐central Texas indicates that ground‐water discharge from the Edwards Aquifer through the Leona River floodplain may be as great as 91.7 Mm³/year. When combined with an estimate of 8.8 Mm³/year for surface flow in the Leona River, as much as 100.5 Mm³/year could be discharged from the Edwards Aquifer through the Leona River floodplain. A value of 11,200 acre‐ft/year (13.82 Mm³/year) has been used as the calibration target in existing ground‐water models for total discharge from Leona Springs and the Leona River. Including ground water or underflow discharge would significantly increase the calibration target in future models. This refinement would improve the conceptualization of ground‐water flow in the western portion of the San Antonio segment of the Edwards Aquifer and would thereby allow for more accurate assessment and management of the ground‐water resources provided by the Edwards Aquifer.     

Fractionation and spectroscopic properties of fulvic acid and its extract

Novel results were obtained when a fulvic acid was isolated from Acros humic acid and fractionated by traditional preparative thin-layer chromatography. Eight colorful bands were directly viewed and analyzed showing very different fluorescence and absorption properties. The fluorescence quantum yield of the bands ranged from 2% to 9.4%, significantly higher than that of natural humic substances. An aqueous fulvic acid solution was also extracted with methylene chloride (CH(2)Cl(2)) by continuous liquid-liquid extraction. The CH(2)Cl(2) extract was further fractionated by thin-layer chromatography. Eleven highly fluorescent colorful bands and six weakly fluorescent bands were observed and examined. UV-vis absorption and fluorescence (including 3D matrix) spectra and fluorescence quantum yields revealed that each band still represented a mixture of compounds. Moreover, substantial differences in optical properties were observed among bands. A single band possessed the highest fluorescence quantum yield (6%) and highest specific fluorescence (fluorescence/mass), and accounted for 21% of the total fluorescence of the extract. The mass of individual bands varied from 1.6% to 14.1% of the total materials recovered. Components of all fractions were grouped into 11 fluorophore families according to their maxima on 3D matrix fluorescence spectra. No component is dominant in the whole fulvic acid or extracted portion in terms of optical properties. Over 40 natural products are proposed for model chromophores.     

Unauthorised development and seismic hazard vulnerability: a study of squatters and engineers in Istanbul, Turkey

Many cities in developing nations have experienced an influx of poor migrants in search of work. This population influx has often been accommodated through land squatting, irregular construction and unauthorised housing. For the urban poor, this has resulted in immediate affordable housing; however, this housing frequently has long-term vulnerability to natural hazards. This article examines the ways in which squatters in Istanbul, Turkey, understand the seismic vulnerability of their unauthorised housing. Distrust of professional engineers and contractors has led Istanbul squatters to believe that self-built housing will not only be less costly but also safer than commercially built housing. The impact of residents' risk perceptions on their vulnerability to natural hazards is examined through a comparison of social attitudes regarding safe housing and the quality of unauthorised construction. This comparison highlights how squatters' risk perceptions necessitate innovative means of reducing vulnerability in unauthorised neighbourhoods of developing cities.     

Influence of papermill sludge on growth of Medicago sativa, Festuca rubra and Agropyron trachycaulum in gold mine tailings: a greenhouse study

A greenhouse study was undertaken to determine the suitability of adding papermill sludge to neutral/alkaline gold mine tailings to improve the establishment of Festuca rubra, Agropyron trachycaulum and Medicago sativa. Festuca rubra root and shoot biomass and A. Trachycaulum shoot biomass were increased with papermill sludge amendment. The addition of papermill sludge and fertilizer drastically increased the shoot and root biomass of M. sativa (20-30 times) while A. trachycaulum and F. rubra showed a more moderate increase in growth. Photosynthetic pigment content of the leaves was higher in papermill sludge treatments than in the treatments without papermill sludge. The organic carbon content, macro-aggregate content and field capacity of the gold mine tailings were increased while the bulk density was decreased by the addition of papermill sludge. This study suggests that addition of papermill sludge and adequate fertilization can alleviate some of the adverse conditions of neutral/alkaline gold mine tailings.     

Production of polyhydroxyalkanoate during treatment of tomato cannery wastewater.

Polyhydroxyalkanoate (PHA) production was achieved using tomato cannery waste coupled with a mixed microbial culture during wastewater treatment. The two-stage PHA production process comprised a sequencing batch reactor (SBR), operating under a periodic feast-famine regime, to accomplish simultaneously wastewater treatment and selection of PHA-accumulating microbes, followed by a batch reactor for the production of PHA-rich biomass. The SBRs were efficient at removing soluble carbon (84%), ammonia (100%), and phosphorus (76%). Meanwhile, PHA-accumulating microbes were enriched under the SBR operating conditions, and PHA content on a cell-weight basis was within the range 7 to 11% in nonfiltered wastewater and 2 to 8% in filtered wastewater. Subsequently, batch studies were implemented with varying loading rates, ranging from 0.4 to 3.2 food-to-microorganism ratios. A maximum 20% PHA content on a cell-weight basis was obtained. Based on the experimental results, a PHA biosynthesis-degradation kinetic model was developed to (1) aid in the design of a pilot- or full-scale PHA production process coupled with wastewater treatment and (2) determine optimal conditions for harvest of PHA-rich biomass.     

The effect of storage and processing on radionuclide content of fruit

After harvesting, the activity content of fruits may still be affected by the manner in which they are treated. Long storage times will reduce the activity contents of short-lived radionuclides; preparation and/or processing may cause activity to be physically removed. This paper presents the results of a review of the available literature on these effects. Data are scarce for both storage and processing, the majority of information on the latter being for 137Cs and 90Sr. For cautious general assessments, it should be assumed that there is no delay and that no activity is lost on processing, especially if the fruits can be eaten raw. However, individual cases may require specific data if available. The use of storage of processing as specific counter-measures to reduce activity concentrations in fruits may not be acceptable to the consumer, especially where alternative, non-contaminated, foodstuffs are readily available.     

An improved dual channel PERCA instrument for atmospheric measurements of peroxy radicals

This paper describes a new dual-channel PEroxy RadiCal Amplification (PERCA) instrument, which has been designed to improve the time resolution and signal to noise and to reduce the interference caused by variations in ambient ozone concentrations. The instrument was run at the Weybourne Atmospheric Observatory (WAO), North Norfolk, during WAOWEX (Weybourne Atmospheric Observatory Winter Experiment) in January/February 2002 and INSPECTRO (Influence of clouds on the spectral actinic flux in the lower troposphere) in September 2002. The performance of the instrument is assessed and compared to that of a single channel instrument. In particular, it is shown how the precision is greatly improved in fluctuating background ozone conditions. In addition the improved time response of the instrument allows changes in peroxy radical concentrations to be related to rapid changes in nitric oxide concentrations and the ozone photolysis frequency, j(O(1)D).     

Distributional analysis of regional benefits and cost of air quality control

The methodology and results of an analysis of benefits and costs of air quality control for an urban region in Florida are given. The machinery used considers the spatial distribution of (a) emission sources, (b) the ambient levels resulting from local meteorological conditions and geographic features, and (c) the socioeconomic characteristics of the impacted population groups. This facilitates an examination of the distributional aspects of costs and benefits associated with various control scenarios. With appropriate adaptation and inputs the steps in our analysis should apply to a distributional benefit/cost analyses for any region.