The Oxidation of Hydrocarbons on Simple Oxide Catalysts

A simple practical scheme for prediction and control of short duration air pollution maxima from a single source is demonstrated for a particular source-site geometry. The method makes use of a number of traditional semi-empirical atmospheric turbulence and diffusion relations in a different application. The concepts stressed in the current example are: (1) the incorporation of interactions of high frequency turbulence and low frequency meandering of the wind into a concentration forecast and (2) the use of source-site geometry to simplify the practical problem as much as possible.     

Remediation of DDT‐contaminated soil using optimized mixtures of surfactants and a mixing system

Soil contaminated with persistent pesticides, such as DDT, poses a serious risk to humans and to wildlife. A surfactant‐aided soil‐washing technique was studied as an alternative method for remediation of DDT‐contaminated soil. An ex situ soil washing method was investigated using nonionic and anionic surfactants due to the clayey structure of the contaminated soil. A mixture of 1 percent nonionic surfactant (Brij 35) and 1 percent anionic surfactant (SDBS) removed more than 50 percent of DDT from soil in a flow‐through system, whereas individual surfactants or other combinations of the surfactants had a lower removal efficiency. The soil‐washing technique was improved using a mixing system. The mixture of surfactants was optimized in the mixing system, and the combination of 2 percent Brij 35 and 0.1 percent SDBS was found to be optimum, removing 70 to 80 percent of DDT. Prewashing of the soil with tap water decreased the adsorption of surfactants to soil particles by 30 to 40 percent, and postwashing recovered 90 percent of the surfactants. © 2010 Wiley Periodicals, Inc.     

The value of coastal wetlands for hurricane protection

Coastal wetlands reduce the damaging effects of hurricanes on coastal communities. A regression model using 34 major US hurricanes since 1980 with the natural log of damage per unit gross domestic product in the hurricane swath as the dependent variable and the natural logs of wind speed and wetland area in the swath as the independent variables was highly significant and explained 60% of the variation in relative damages. A loss of 1 ha of wetland in the model corresponded to an average USD 33,000 (median = USD 5000) increase in storm damage from specific storms. Using this relationship, and taking into account the annual probability of hits by hurricanes of varying intensities, we mapped the annual value of coastal wetlands by 1 km x 1 km pixel and by state. The annual value ranged from USD 250 to USD 51,000 ha(-1) yr(-1), with a mean of USD 8240 ha(-1) yr(-1) (median = USD 3230 ha(-1) yr(-1)) significantly larger than previous estimates. Coastal wetlands in the US were estimated to currently provide USD 23.2 billion yr(-1) in storm protection services. Coastal wetlands function as valuable, selfmaintaining "horizontal levees" for storm protection, and also provide a host of other ecosystem services that vertical levees do not. Their restoration and preservation is an extremely cost-effective strategy for society.     

Use of toxicity identification evaluations to determine the pesticide mitigation effectiveness of on-farm vegetated treatment systems

Evidence of ecological impacts from pesticide runoff has prompted installation of vegetated treatment systems (VTS) along the central coast of California, USA. During five surveys of two on-farm VTS ponds, 88% of inlet and outlet water samples were toxic to Ceriodaphnia dubia. Toxicity identification evaluations (TIEs) indicated water toxicity was caused by diazinon at VTS-1, and chlorpyrifos at VTS-2. Diazinon levels in VTS-1 were variable, but high pulse inflow concentrations were reduced through dilution. At VTS-2, chlorpyrifos concentrations averaged 52% lower at the VTS outlet than at the inlet. Water concentrations of most other pesticides averaged 20-90% lower at VTS outlets. All VTS sediment samples were toxic to amphipods (Hyalella azteca). Sediment TIEs indicated toxicity was caused by cypermethrin and lambda-cyhalothrin at VTS-1, and chlorpyrifos and permethrin at VTS-2. As with water, sediment concentrations were lower at VTS outlets, indicating substantial reductions in farm runoff pesticide concentrations.     

Uranium removal from groundwater via in situ biostimulation: Field-scale modeling of transport and biological processes

During 2002 and 2003, bioremediation experiments in the unconfined aquifer of the Old Rifle UMTRA field site in western Colorado provided evidence for the immobilization of hexavalent uranium in groundwater by iron-reducing Geobacter sp. stimulated by acetate amendment. As the bioavailable Fe(III) terminal electron acceptor was depleted in the zone just downgradient of the acetate injection gallery, sulfate-reducing organisms came to dominate the microbial community. In the present study, we use multicomponent reactive transport modeling to analyze data from the 2002 field experiment to identify the dominant transport and biological processes controlling uranium mobility during biostimulation, and determine field-scale parameters for these modeled processes. The coupled process simulation approach was able to establish a quantitative characterization of the principal flow, transport, and reaction processes based on the 2002 field experiment, that could be applied without modification to describe the 2003 field experiment. Insights gained from this analysis include field-scale estimates of the bioavailable Fe(III) mineral threshold for the onset of sulfate reduction, and rates for the Fe(III), U(VI), and sulfate terminal electron accepting processes.     

Social networks and the cognitive motivation to realize network opportunities: a study of managers' information gathering behaviors

Information gathering is central to a variety of organizational behavior theories, but researchers have suggested that our understanding of the actual information gathering behaviors of managers is underdeveloped. Social network characteristics are theorized to be a key determinant of information gathering behaviors, but social network research has been criticized for: (1) not measuring the intervening mechanisms by which network characteristics are theorized to have their effects and (2) not considering how actors' motivation affects what network benefits are realized. This article addresses these concerns through an empirical study of the actual information gathering behaviors of managers. It posits that individual differences in a personality variable called need for cognition capture differences in actors' cognitive motivation to realize the potential information benefits that exist in their social networks. Results show that network characteristics do affect information benefits, but these effects are stronger for managers motivated to take advantage of them. These findings both support social capital theory and suggest the important role that personality can play in augmenting social network analyses. Copyright © 2007 John Wiley & Sons, Ltd.     

Minimizing life-cycle costs of gun propellant selection through model-based decision making: a case study in environmental screening and performance testing

The work presented here demonstrates the first phases of a newly-proposed gun propellant formulation process that will minimize life-cycle costs through science-based design. This new approach to gun propellant formulation proposes maximal use of modeling and simulation in the earliest phases of the developmental cycle to screen candidate formulations, resulting in the elimination of probable poor performers and the identification of the most promising candidates for further study and testing. The screening and identification of promising candidate formulations is demonstrated in the study presented here under the assumption of a specific weapon platform and user requirements. The process of selecting a propellant for the assumed gun system application has been distilled into a series of measurable steps leading from a set of candidate materials, through logical and numerical filters, to a shorter list of energetic materials demonstrated as viable choices for the weapon platform. Environmental filtering and performance modeling are used to screen propellants through a well-defined sequence of tests designed to weed out materials that do not meet standards in terms of safety, energy, or manufacturability. Because much of the testing is performed by computer modeling, the gun systems and energetic materials need not be present (nor even existent) in order to be described and matched against performance requirements for future applications. The calculations presented here demonstrate that utilizing computer models in the early developmental stages of the formulation process rather than physical testing produces enormous savings in labor, material, and environmental costs, along with a tremendous reduction in the time required to select a "best candidate" propellant.     

A comparison of temperate reef fish assemblages recorded by three underwater stereo-video techniques

Three underwater stereo-video techniques were used to sample the relative densities and species richness of temperate reef fish assemblages at three reef locations and two habitats (high- and low-relief reef) within Hamelin Bay, south-western Australia. The three techniques compared were diver-operated stereo-video strip transects, baited remote stereo-video and unbaited remote stereo-video. While unbaited remote stereo-video and diver-operated stereo-video transects recorded greater species richness at high compared to low-relief reefs, baited remote stereo-video recorded similar species richness at the two habitat types. The diver-operated stereo-video system was manoeuvred through caves and under overhangs recording small, cryptic, cave-dwelling species that were not recorded by either remote video techniques (Trachinops noarlungae, Trachinops brauni, Chromis klunzingeri, Trachichthys australis). Both remote video techniques recorded greater species richness and relative density of the most common species of Labridae, Ophthalmolepsis lineolatus. Baited remote video recorded the rarer, large predatory fish species (e.g. Seriola hippos, Glaucosoma hebraicum, Heterodontus portusjacksoni). None of the techniques sampled small cryptic fish families such as Gobiidae or Blenniidae. A combination of survey techniques is recommended for comprehensive fishery-independent studies that aim to sample broad components of fish assemblages.An erratum to this article can be found at     

Assessment of aquatic plants in the reservoirs of AES-tietê and development of an integrated control model for the most important species

The general objective of this work was to develop a monitoring and management model for aquatic plants that could be used in reservoir cascades in Brazil, using the reservoirs of AES-Tietê as a study case. The investigations were carried out at the reservoirs of Barra-Bonita, Bariri, Ibitinga, Promiss?o, and Nova-Avanhandava, located in the Tietê River Basin; Agua Vermelha, located in the Grande River Basin; Caconde, Limoeiro, and Euclides da Cunha, which are part of the Pardo River Basin; and the Mogi-Gua?u reservoir, which belongs to the Mogi-Gua?u River basin. The main products of this work were: development of techniques using satellite-generated images for monitoring and planning aquatic plant control; planning and construction of a boat to move coating plant masses and an airboat equipped with a DGPS navigation and application flow control system. Results allowed to conclude that the occurrence of all types of aquatic plants is directly associated with sedimentation process and, consequently, with nutrient and light availability. Reservoirs placed at the beginning of cascades are more subject to sedimentation and occurrence of marginal, floating and emerged plants, and are the priority when it comes to controlling these plants, since they provide a supply of weeds for the other reservoirs. Reservoirs placed downstream show smaller amounts of water-suspended solids, with greater transmission of light and occurrence of submerged plants.