Effects of watershed configuration and composition on downstream lake water quality

We evaluated the relationships between landscape characteristics and lake water quality in receiving waters by regressing four water quality responses on landscape variables that were measured for whole watersheds and three different buffer distances (30, 60, and 120 m). Classical percolation theory was used to conceptualize nutrient pathways and to explain nonlinear responses. The response variables were total nitrogen (TN), total phosphorus (TP), chlorophyll-a (Chl-a), and Secchi transparency (SD). Landscape data were obtained from satellite image-derived maps of 130 watersheds in Iowa using geographic information systems software. We developed regression models with a stepwise protocol selecting the optimal number of significant explanatory variables. Configuration variables such as contagion, the cohesion of cropland and urban land, and the aggregation index of forest were very important and more important than variables assessing landscape composition (e.g., percentage farmland). Whole watershed models predicted between 15 and 67% of the variability in TN, TP, Chl-a, and SD. Proximity-explicit data offered only slightly improved statistical power over land cover data derived from the entire watershed for variables TN, Chl-a. and SD, but not for TP.     

Quantifying phosphorus retention and release in rivers and watersheds using extended end-member mixing analysis (E-EMMA)

Extended end-member mixing analysis (E-EMMA) is presented as a novel empirical method for exploring phosphorus (P) retention and release in rivers and watersheds, as an aid to water-quality management. E-EMMA offers a simple and versatile tool that relies solely on routinely measured P concentration and flow data. E-EMMA was applied to two river systems: the Thames (U.K.) and Sandusky River (U.S.), which drain similar watershed areas but have contrasting dominant P sources and hydrology. For both the Thames and Sandusky, P fluxes at the watershed outlets were strongly influenced by processes that retain and cycle P. However, patterns of P retention were markedly different for the two rivers, linked to differences in P sources and speciation, hydrology and land use. On an annual timescale, up to 48% of the P flux was retained for the Sandusky and up to 14% for the Thames. Under ecologically critical low-flow periods, up to 93% of the P flux was retained for the Sandusky and up to 42% for the Thames. In the main River Thames and the Sandusky River, in-stream processes under low flows were capable of regulating the delivery of P and modifying the timing of delivery in a way that may help to reduce ecological impacts to downstream river reaches, by reducing ambient P concentrations at times of greatest river eutrophication risk. The results also suggest that by moving toward cleaner rivers and improved ecosystem health, the efficiency of P retention may actually increase.     

The Route to Best Science in Implementation of the Endangered Species Act’s Consultation Mandate: The Benefits of Structured Effects Analysis

The Endangered Species Act is intended to conserve at-risk species and the ecosystems upon which they depend, and it is premised on the notion that if the wildlife agencies that are charged with implementing the statute use the best available scientific information, they can successfully carry out this intention. We assess effects analysis as a tool for using best science to guide agency decisions under the Act. After introducing effects analysis, we propose a framework that facilitates identification and use of the best available information in the development of agency determinations. The framework includes three essential steps—the collection of reliable scientific information, the critical assessment and synthesis of available data and analyses derived from those data, and the analysis of the effects of actions on listed species and their habitats. We warn of likely obstacles to rigorous, structured effect analyses and describe the extent to which independent scientific review may assist in overcoming these obstacles. We conclude by describing eight essential elements that are required for a successful effects analysis.     

Modelling the Transport of Oil–Mineral-Aggregates (OMAs) in the Marine Environment and Assessment of Their Potential Risks

Spilled oil can interact with suspended particles in marine environments and form oil–mineral aggregates (OMAs). Some OMAs with densities higher than seawater density can settle to the seedbed to pose potential risks to benthic organisms. To understand the transport and fate of oil associated with OMAs and evaluate their potential risks, an integrated hydrodynamic and fate/transport model has been used in a hypothetical case study of 1,000 tonnes of South Louisiana oil spilled in the Bristol Channel. Several scenarios have been simulated under different wave and current conditions. By using OMA properties derived from laboratory measurements reported in literature, it has been found that the risk to the benthos is unlikely for the two hypothetical cases with strong currents, but it is likely for the wave only (weak current) case. The effects of other factors such as OMA properties and sediment concentration were also examined in terms of their effects on the transport process and risks.     

Dividing disasters in Aceh, Indonesia: separatist conflict and tsunami, human rights and humanitarianism

This paper examines the interface between human rights and humanitarian action in the context of the conflict and tsunami in Aceh, Indonesia, between 1998 and 2007. It looks at the challenges international humanitarian non-governmental organisations (NGOs) faced as they engaged in human rights work in the conflict period and in conflict-related activities in the post-tsunami period. The paper argues that many large NGOs may have compromised what some would hold to be essential principles for humanitarian action because of domestic political concerns, donor restrictions and resistance among certain NGO chiefs. In contrast with the pre-tsunami period, in which NGOs worked for years amid military operations, in the post-tsunami period NGOs were decidedly apolitical, neglecting the conflict in their tsunami response--despite significant developments that permitted greater political engagement in Aceh's post-conflict transformation. The evidence suggests that NGOs are challenged in contextualising humanitarian responses and that there is a need to underscore donor flexibility and independence in humanitarian action.     

A coffee agroecosystem model: I. Growth and development of the coffee plant

This paper is the first of three on the coffee production system consisting of (1) the coffee plant, (2) coffee berry borer (CBB) and (3) the role of CBB parasitoids. A previous simulation model of the coffee plant was developed using data from Brazil where coffee phenology is characterized by distinct seasonal flowering (Gutierrez et al., 1998). In contrast, flowering in Colombia is continuous with low seasonality. To capture the differences in coffee phenology and growth in the two climatic regions, the Gutierrez et al. (1998) model was modified using new data from Colombia.The modifications to the model include:

(1)

The effect of solar radiation on floral buds initiation;

(2)

An age structure population model to track the daily input and development of the floral buds;

(3)

The effect of leaf water potential on breaking dormancy in flower buds, and hence on the timing and intensity of flowering;

(4)

The incorporation of both the vegetative and the reproductive demands to predict the photosynthetic rate.

(5)

The effect of low temperature on photosynthesis and defoliation.

Other aspects of the model were re-interpreted and refinements made to generalize its structure for use across coffee varieties and geographic areas. The model, without modification, realistically simulates field data from Brazil and two Colombian locations having different varieties, patterns of rainfall and hence flowering phenology.The model will be used as the base trophic level for incorporating CBB and high tropic levels effects, and for the analysis of management options in the coffee production system.     

Characterization of the ignition by repetitive streamer discharges using laser diagnostics

Repetitive streamer discharges caused by transients, e.g. due to high frequency overvoltages, can ignite combustible mixtures, which has to be taken into account concerning the safety assessment of electrical apparatus for usage in hazardous areas. Hydrogen/air mixtures were ignited inside a closed vessel using a rod/plane electrode configuration. Alternating voltage with a frequency between 600 and 750 kHz and amplitudes of up to 20 kV was used to produce streamer discharges. The ignition process and the subsequent flame front propagation were examined with respect to mixture composition and several electrical parameters using time-resolved measurements of planar laser-induced fluorescence (PLIF) of OH radicals. A multiple pulse laser and detection system was used to assemble four images during one experiment. These measurements have given detailed information about the point of ignition and flame velocities. The experimental results will be used to validate numerical simulations of ignition by streamer discharges, which will yield deep insights into this specific ignition process.     

The overgeneralized validity of validity generalization

This Incubator contends that the concept of validity generalization has been overgeneralized in its capacity to predict work performance for three reasons: sampling bias in the occupations selected for analysis, the prediction of acceptable performance to the exclusion of superior performance, and the conflation of statistical prediction and psychological meaning. Copyright © 2013 John Wiley & Sons, Ltd.     

Explosibility of micron- and nano-size titanium powders

Explosibility of micron- and nano-titanium was determined and compared according to explosion severity and likelihood using standard dust explosion equipment. ASTM methods were followed using a Siwek 20-L explosion chamber, MIKE 3 apparatus and BAM oven. The explosibility parameters investigated for both size ranges of titanium include explosion severity (maximum explosion pressure (P_max) and size-normalized maximum rate of pressure rise (K_St)) and explosion likelihood (minimum explosible concentration (MEC), minimum ignition energy (MIE) and minimum ignition temperature (MIT)). Titanium particle sizes were ?100 mesh (<150 μm), ?325 mesh (<45 μm), ≤20 μm, 150 nm, 60–80 nm, and 40–60 nm. The results show a significant increase in explosion severity as the particle size decreases from ?100 mesh with an apparent plateau being reached at ?325 mesh and ≤20 μm. Micron-size explosion severity could not be compared with that for nano-titanium due to pre-ignition of the nano-powder in the 20-L chamber. The likelihood of an explosion increases significantly as the particle size decreases into the nano range. Nano-titanium is very sensitive and can self-ignite under the appropriate conditions. The explosive properties of the nano-titanium can be suppressed by adding nano-titanium dioxide to the dust mixture. Safety precautions and procedures for the nano-titanium are also discussed.