CH4/CO2 ratios indicate highly efficient methane oxidation by a pumice landfill cover-soil

Landfills that generate too little biogas for economic energy recovery can potentially offset methane (CH₄) emissions through biological oxidation by methanotrophic bacteria in cover soils. This study reports on the CH₄ oxidation efficiency of a 10-year old landfill cap comprising a volcanic pumice soil. Surface CH₄ and CO₂ fluxes were measured using field chambers during three sampling intervals over winter and summer. Methane fluxes were temporally and spatially variable (?0.36 to 3044 mg CH₄ m^?2 h^?1); but were at least 15 times lower than typical literature CH₄ fluxes reported for older landfills in 45 of the 46 chambers tested. Exposure of soil from this landfill cover to variable CH₄ fluxes in laboratory microcosms revealed a very strong correlation between CH₄ oxidation efficiency and CH₄/CO₂ ratios, confirming the utility of this relationship for approximating CH₄ oxidation efficiency. CH₄/CO₂ ratios were applied to gas concentrations from the surface flux chambers and indicated a mean CH₄ oxidation efficiency of 72%. To examine CH₄ oxidation with soil depth, we collected 10 soil depth profiles at random locations across the landfill. Seven profiles exhibited CH₄ removal rates of 70–100% at depths <60 cm, supporting the high oxidation rates observed in the chambers. Based on a conservative 70% CH₄ oxidation efficiency occurring at the site, this cover soil is clearly offsetting far greater CH₄ quantities than the 10% default value currently adopted by the IPCC.     

Refinery evaluation of optical imaging to locate fugitive emissions

Fugitive emissions account for approximately 50% of total hydrocarbon emissions from process plants. Federal and state regulations aiming at controlling these emissions require refineries and petrochemical plants in the United States to implement a Leak Detection and Repair Program (LDAR). The current regulatory work practice, U.S. Environment Protection Agency Method 21, requires designated components to be monitored individually at regular intervals. The annual costs of these LDAR programs in a typical refinery can exceed US$1,000,000. Previous studies have shown that a majority of controllable fugitive emissions come from a very small fraction of components. The Smart LDAR program aims to find cost-effective methods to monitor and reduce emissions from these large leakers. Optical gas imaging has been identified as one such technology that can help achieve this objective. This paper discusses a refinery evaluation of an instrument based on backscatter absorption gas imaging technology. This portable camera allows an operator to scan components more quickly and image gas leaks in real time. During the evaluation, the instrument was able to identify leaking components that were the source of 97% of the total mass emissions from leaks detected. More than 27,000 components were monitored. This was achieved in far less time than it would have taken using Method 21. In addition, the instrument was able to find leaks from components that are not required to be monitored by the current LDAR regulations. The technology principles and the parameters that affect instrument performance are also discussed in the paper.     

An Automated Technique for Delineating and Characterizing Valley-Bottom Settings

Accurate delineation and characterization of valley-bottom settings is crucial to the assessment of the biological and geomorphological components of riverine systems; yet, to date, most valley-bottom mapping endeavors have been done manually. To improve this situation, we developed automated techniques in a Geographic Information System (GIS) for delineating and characterizing valley-bottom settings in river basins ranging in size from approximately 1,000–10,000 km². All procedures were developed with ARC/INFO GIS software and fully automated in Arc Macro Language (AML). The GRID module is required for valley-bottom delineation and slope calculations; whereas characterization (i.e., measuring the width of the valley-bottom zone) requires Coordinate Geometry (COGO) in the ARCEDIT module. The process requires three inputs: a polygon coverage of the analysis area; an arc coverage of its hydrography, and a grid representing its digital elevation. The AML is designed to operate within a wide range of computer memory/disk space options, and it allows users to customize several procedures to match the scale and complexity of a given analysis area with available computer hardware.     

Solubility of toluene, benzene and TCE in high-microbial concentration systems

We report measurements of solubility limits for benzene, toluene, and TCE in systems that contain varying levels of biomass up to 0.13 g mL⁻¹ for TCE and 0.25 g mL⁻¹ for benzene and toluene. The solubility limit increased from 21 to 48 mM when biomass (in the form of yeast) was added to aqueous batch systems containing benzene. The toluene solubility limit increased from 4.9 to greater than 20 mM. For TCE, the solubility increased from 8 mM to more than 1000 mM. Solubility for TCE (trichloroethylene) was most heavily impacted by biomass levels, changing by two orders of magnitude as the microbial concentrations approach those in biofilms.     

Effects of short-term pH fluctuations on cadmium, nickel, lead, and zinc availability to ryegrass in a sewage sludge-amended field

In this field experiment, sewage sludge was applied at 0, 5, 10, and 50tha(-1), and the availability of Cd, Ni, Pb, and Zn was assessed both by ryegrass uptake and by DTPA extractions. The aim was to investigate the role of important soil parameters, particularly pH, on heavy metal availability. It was found that metal uptake and extractability increased significantly in the 50tha(-1) treatment. In the 16th week of the experiment there was a significant, although temporary, increase in DTPA-extractable Cd, Ni, and Zn concentrations. Metal concentrations in ryegrass were also significantly elevated in week 20 compared to the subsequent cuttings. These fluctuations in both DTPA and ryegrass uptake occurred only at 50tha(-1) and were probably induced by a sudden pH decrease measured in the same treatment in week 16. This suggests that soils which have received high applications of sewage sludge may be prone to fluctuations in metal availability.     

The impact of the 2004 tsunami on coastal Thai communities: assessing adaptive capacity

The suddenness and scale of the 26 December 2004 tsunami and the challenges posed to affected communities highlighted the benefits of their members having a capacity to confront and adapt to the consequences of such a disaster. Research into adaptive capacity or resilience has been conducted almost exclusively with Western populations. This paper describes an exploratory study of the potential of a measure of collective efficacy developed for Western populations to predict the capacity of members of a collective society, Thai citizens affected by the 2004 tsunami, to confront effectively the recovery demands associated with this disaster. Following a demonstration that this measure could predict adaptive capacity, the role of religious affiliation, ethnicity and place of residence in sustaining collective efficacy is discussed. The implications of the findings for future research on, and intervention to develop, adaptive capacity among Thai citizens in particular and collectivist societies in general are discussed.     

Regulation of honey bee age polyethism by juvenile hormone

Summary Previous studies suggested that juvenile hormone (JH) is involved in the regulation of physiological processes that are associated with division of labor in honey bees but the effects of JH on behavior were not clear. The hypothesis that JH affects worker age polyethism was tested by observing individually marked bees topically treated with different doses of the JH analog methoprene. Methoprene caused dose-dependent changes in the timing and frequency of occurrence of four important age-dependent tasks: brood and queen care, food storage, nest maintenance, and foraging. Weak or no effects were observed for social interactions, self-grooming, and other non-task behaviors that were not performed in an age-dependent manner. These results support the hypothesis that JH is involved in the control of age polyethism. A model is presented that explains the role of JH in regulating division of labor. JH may regulate the colony's allocation of labor by altering the probabilities of response to tasks. According to this model, hormone titers increase with age according to a genetically determined pattern of development, but this rise may be modulated by environmental and colony factors such as food availability and population structure. Extrinsic regulation of JH may be a mechanism underlying the ability of workers to respond to changing colony needs.