Evaluation of soil solid amendments for TCE biodegradation in a biobarrier system

Permeable biobarrier systems (PBSs) are being recognized as low‐cost passive bioremediation technologies for chlorinated organic contamination. This innovative technology can play a crucial and effective role in site restorations. Laboratory‐scale experiments were conducted to investigate the biodegradation of trichloroethylene (TCE) to ethylene in shallow groundwater through the use of a PBS enhanced by bioaugmentation at the U.S. Department of Energy's Savannah River Site (SRS). Two composts and two plant amendments, eucalyptus mulch (EM) and corncobs (CC), were examined for their effectiveness at creating and maintaining conditions suitable for TCE anaerobic dechlorination. These materials were evaluated for their (1) nutrient and organic carbon content, (2) TCE sorption characteristics, and (3) longevity of release of nutrients and soluble carbon in groundwater to support TCE dechlorination. Native bacteria in the columns had the ability to convert TCE to dichloroethenes (DCEs); however, the inoculation with the TCE‐degrading culture greatly increased the rate of biodegradation. This caused a significant increase in by‐product concentration, mostly in the form of DCEs and vinyl chloride (VC) followed by a slow degradation to ethylene. Of the tested amendments, eucalyptus mulch was the most effective at supporting the reductive dechlorination of TCE. Corncobs created a very acidic condition in the column that inhibited dechlorination. © 2007 Wiley Periodicals, Inc.     

Kinetic studies of the reaction of hydroxyl radicals with trichloroethylene and tetrachloroethylene

Rate coefficients are reported for the gas-phase reaction of the hydroxyl radical (OH) with C2HCl3 (k(1)) and C2Cl4 (k2) over an extended temperature range at 740+/-10 Torr in a He bath gas. These absolute rate measurements were accomplished using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions. The simple Arrhenius equation adequately describes the low temperature data for k1 (<650 K) and the entire data set for k2 and is given by (in units of cm3 molecule(-1) s(-1)): k1(291 - 650 K) = (9.73+/-1.15) x 10(-13) exp (158.7+/-44.0)/T, k2(293 - 720 K ) = (1.53+/-0.14) x 10(-12) exp (-688.2+/-67.5)/T. Error limits are 2sigma values. The room temperature values for k1 and k2 are within +/-2sigma of previous data using different techniques. The Arrhenius activation energies for k1 and k2 are a factor of 2-3 lower than previously reported values. The experimental measurements for both k1 and k2 in conjunction with transition state and variation transition state theory calculations infer an OH addition mechanism. The lack of a measurable kinetic isotope effect for k1 is consistent with this mechanism. Insight into the subsequent reactions of the chemically activated intermediate are presented in the form of potential energy diagrams derived from ab initio calculations.     

Catalytic hydrogenation of polyaromatic hydrocarbon (PAH) compounds in supercritical carbon dioxide over supported palladium

A series of supported palladium catalysts were evaluated for their ability to mediate the complete hydrogenation of polycyclic aromatic hydrocarbon (PAH) compounds. Benzo[a]pyrene (B[a]P) or phenanthrene (Phe) in hexane was merged with a hydrogen-carbon dioxide [5% (w/w) H(2)/CO(2)] stream and transferred to a flow through mini-reactor (capacity ca. 1 g) that was maintained at 90 degrees C under a back-pressure of 20.68 MPa. Effluent from the reactor trapped in hexane was monitored/quantified by gas chromatography-mass spectrometry. Catalyst formulations supported on iron powder, high density polyethylene (HDPE) or gamma-alumina were prepared and compared in terms of hydrogenation activity as measured by the quantity of substrate per unit time that could be perhydrogenated to toxicologically innocuous products. Both of the Pd preparations supported on gamma-alumina were more efficient than a commercial Pd(0) (5% w/w) on gamma-Al(2)O(3) formulation or preparations supported on HDPE or the iron powder. Bimetallic mixtures with Pd increased the hydrogenation activity when co-deposited with Cu or Ni but not with Ag or Co. However, increases in hydrogenation activity by increasing the loading of Pd (or bimetallic mixture) on this surface were limited. Despite using supercritical carbon dioxide (scCO(2)) to swell the surfaces of the polymer, the deposition of nanoparticles within the polyethylene formulation was appreciably less active than either the oxidic or the Fe(0) formulations.     

A Spatial Analysis of the Economic and Ecological Efficacy of Land Retirement

This paper uses a cellular automata simulation model of a hypothetical landscape to investigate the role of location as it relates to the efficacy of land retirement in achieving two environmental goals: hydrological improvement and habitat improvement. Statistical analysis of simulation results is used to show how absolute and relative location relate to achievement of these objectives. Linear and nonlinear compromise programming frameworks then combine these two environmental objectives and a cost minimization objective into a measure that allows decision-makers to rank the desirability of different retirement strategies. These frameworks are explored to determine what each implies about the tradeoffs that must be made among objectives and among the spatial land parcel characteristics that contribute to those objectives.     

A conceptual model and empirical analysis of children's acquisition of spatial knowledge

How adults and children come to understand, represent and behave within their spatial environment are topics of great interest to geographers, psychologists, environmental planners and laypeople. Considerable research and theory has been published on these and related topics. In this paper, we will review some of what is known and theorized about spatial cognition and then consider elements of our research program on the acquisition of spatial knowledge. We focus on two intimately related topics. The first is the development of a conceptual model of the knowledge structures and processes associated with acquiring, representing and accessing knowledge of a given environment. The conceptual model forms the basis for a formal computational process model intended as a simulation of actual knowledge and performance in way finding tasks. The second emphasis is an in-depth case study of the acquisition of spatial knowledge. The case study focuses on a single child acquiring knowledge of a lengthy route through an unfamiliar suburban neighborhood. It is presented as an empirical test of certain assumptions embodied within the conceptual model.Before introducing the conceptual model and the case study, we first review the state of current theory and data on spatial cognition and identify four central issues confronting researchers in this field. This review provides a necessary context for describing and evaluating our program of research. The second section of this paper discusses elements of the conceptual model and its relationship to other formal computational models. The third section considers specific hypotheses about the acquisition and representation of spatial knowledge and tests of these hypotheses from the single in-depth case study. The final discussion section of this paper is a reconsideration of the four issues raised in the first section and necessary and proposed extensions of the current research.     

Spatio-temporal patterns in county-level incidence and reporting of Lyme disease in the northeastern United States, 1990–2000

We present an exploratory analysis of reported county-specific incidence of Lyme disease in the northeastern United States for the years 1990–2000. We briefly review the disease ecology of Lyme disease and the use of risk maps to describe local incidence as estimates of local risk of disease. We place the relevant elements of local environmental and ecological variables, local disease incidence, and (importantly) local disease reporting in a conceptual context to frame our analysis. We then apply hierarchical linear models of increasing complexity to summarize observed patterns in reported incidence, borrowing information across counties to improve local precision. We find areas of increasing incidence in the central northeastern Atlantic coast counties, increasing incidence branching to the north and west, and an area of fairly stable and slightly decreasing reported incidence in western New York.     

A technique for collection of particulate organic matter in situ

A technique is described for concentrating and collecting particulate organic matter from water with minimal disturbance. This involves exposing in situ the surface of a Millipore^® filter monitor mounted on a simple vacuum flask assembly.     

Carbon Monitoring Costs and their Effect on Incentives to Sequester Carbon through Forestry

Technically, forestry projects have thepotential to contribute significantly tothe mitigation of global warming, but manysuch projects may not be economicallyattractive at current estimates of carbon(C) prices. Forest C is, in a sense, a newcommodity that must be measured toacceptable standards for the commodity toexist. This will require that credible Cmeasuring and monitoring procedures be inplace. The amount of sequestered C that canbe claimed by a project is normallyestimated based on sampling a number ofsmall plots, and the precision of thisestimate depends on the number of plotssampled and on the spatial variability ofthe site. Measuring C can be expensive andhence it is important to select anefficient C-monitoring strategy to makeprojects competitive in the C market. Thispaper presents a method to determinewhether a forestry project will benefitfrom C trading, and to find the optimalmanagement strategy in terms of forestcycle length and C-monitoring strategyA model of an Acacia mangiumplantation in southern Sumatra, Indonesiais used to show that forestry projects canbe economically attractive under a range ofconditions, provided that the project islarge enough to absorb fixed costs.Modeling results indicate that between 15and 38 Mg of Certified Emission Reductions(CERs) per hectare can be captured by thesimulated plantation under optimalmanagement, with optimality defined asmaximizing the present value of profitsobtained from timber and C. The optimalcycle length ranged from 12 to 16 years andthe optimal number of sample plots rangedfrom 0 to 30. Costs of C monitoring (inpresent-value terms) were estimated to bebetween 0.45 (Mg C)^-1 to 2.11 (MgC)^-1 depending on the spatialvariability of biomass, the variable costsof C monitoring and the discount rate.     

Systems approaches to integrated solid waste management in developing countries

Solid waste management (SWM) has become an issue of increasing global concern as urban populations continue to rise and consumption patterns change. The health and environmental implications associated with SWM are mounting in urgency, particularly in the context of developing countries. While systems analyses largely targeting well-defined, engineered systems have been used to help SWM agencies in industrialized countries since the 1960s, collection and removal dominate the SWM sector in developing countries. This review contrasts the history and current paradigms of SWM practices and policies in industrialized countries with the current challenges and complexities faced in developing country SWM. In industrialized countries, public health, environment, resource scarcity, climate change, and public awareness and participation have acted as SWM drivers towards the current paradigm of integrated SWM. However, urbanization, inequality, and economic growth; cultural and socio-economic aspects; policy, governance, and institutional issues; and international influences have complicated SWM in developing countries. This has limited the applicability of approaches that were successful along the SWM development trajectories of industrialized countries. This review demonstrates the importance of founding new SWM approaches for developing country contexts in post-normal science and complex, adaptive systems thinking.     

Effects of oxidants on soybean growth and yield in the Pakistan Punjab.

Plants of soybean (Glycine max L.) were grown with and without the ozone protectant EDU (N-[2-(2-oxo-1-imidazolidinyl)ethyl]-n2 phenylurea) at a suburban site, a remote rural site and a rural roadside site around the city of Lahore, Pakistan. The development and yield of the plants was determined in two experiments--one immediately post-monsoon and one in the following spring (pre-monsoon). Concentrations of nitrogen dioxide and photochemical oxidants were measured at each site. The effect on yield of EDU at the suburban site (47 and 113% increase in seed weight per plant relative to the untreated plants in the post- and pre-monsoon experiments, respectively) was similar to the effects of filtration on yield on soybean in a parallel open-top chamber study at the same site (77% increase relative to plants subjected to unfiltered air for the pre-monsoon experiment). Effects of EDU on yield were greater at both rural sites than at the suburban site in both experiments, and greater in the spring experiment (182% at the remote rural site and 285% at the rural roadside site) than in the post-monsoon experiment (94% at the remote rural site and 170% at the rural roadside site); oxidant concentrations were also greater at the rural sites than at the suburban site, and greater in the spring experiment than the post-monsoon experiment. The results imply that ozone may be causing significant crop losses in rural areas around Lahore; however, the geographical extent of the problem, and the implications for peri-urban agriculture around other cities of south Asia are uncertain.