Selecting objectively defined reference sites for stream bioassessment programs

Our study develops and demonstrates an objective method for selecting reference sites for the assessment of ecological condition in freshwater ecosystems. The method uses widely available GIS data to group potential sites based on their natural environments. It then establishes the degree and types of human activities each site is exposed to prior to scoring the sites in each group by the relative amount of human activity present. Finally, the sites in each group with the least amount of human activity are categorized as reference sites, with the boundary between reference and test sites defined to maximize the distinctiveness of the two categories with respect to human activity. Application of this technique for the purpose of identifying headwater reference basins in rural areas of southwestern Ontario resulted in the classification of basins into six natural groups based on the dominant texture of the surface geology. Development of a human activity gradient indicated that basins varied according to the amount of exposure to agricultural activities with most basins having at least moderate exposure. Establishment of the reference test boundary indicated that the selected reference basins exhibited substantively lower extents of agricultural activity than test sites for most groups. Because this method uses only widely available GIS data, it enables rapid and cost-effective identification of candidate reference sites, even for large, remote, and understudied regions.     

Persistence of the sulfonylurea herbicides thifensulfuron-methyl, ethametsulfuron-methyl, and metsulfuron-methyl in farm dugouts (ponds)

Sulfonylurea herbicides are applied at relatively low rates (3 to 40 g ha(-1)) to control weeds in a variety of crops across the Canadian prairies. Because of their high phytotoxicity and the likelihood of their transport in surface runoff, there is concern about their possible impact to aquatic ecosystems. Little is known, however, about their persistence and behavior in aquatic ecosystems. To assess persistence in aquatic ecosystems, three prairie farm dugouts (ponds) were fortified with either thifensulfuron-methyl {methyl 3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]-2-thiophenecarboxylate}, ethametsulfuron-methyl {methyl 2-[[[[[4-ethoxy-6-(methylamino)-1,3,5-triazin-2-yl]amino]carbonyl]amino]sulfonyl]benzoate} or metsulfuron-methyl {methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazinyl)amino]carbonyl]amino]sulfonyl]benzoate}. The decreasing order of persistence of environmentally relevant concentrations (1 to 4.6 microg L(-1)) of these herbicides in dugout water over the June to October period was metsulfuron-methyl>ethametsulfuron-methyl>thifensulfuron-methyl. The corresponding dissipation half-lives (DT(50)) of 84, 30, and 16 d, respectively, are in the same relative order as the recropping intervals for these herbicides. Thifensulfuron-methyl showed a biphasic dissipation with slower dissipation during the winter months. In contrast, the dissipation of metsulfuron-methyl, the sulfonylurea herbicide with the longest DT(50), was somewhat enhanced under winter conditions. One of the major routes of sulfonylurea herbicide dissipation was removal from the water column when dugout water was lost during hydrological discharge. The relatively long persistence of these herbicides in water indicates that partitioning into sediments was minimal, the sulfonylurea and methyl ester linkages in these compounds were resistant to hydrolysis in weakly alkaline waters, and that microbial and photolytic degradation in dugout waters were slow.     

Competition,Sustainability and Packaging Policy in the UK

This paper examines the use of economic instruments in the implementation of environmental policy, based upon a recent study into the European Union Packaging and Packaging Waste Directive (94/62/EC). It explores the introduction of competitionbased models in the UK implementation of the Directive, and assesses their ability to achieve positive environmentaloutcomes in a cost-efficient manner. Several problems for the competition model are discussed, particularly the fear of profiteering within marketbased systems by some economic operators; the behaviour of economic operators towards non-profitable market segments; the ability of free-market models to engender public participation in recycling programmes; and the failure of private sector solutions to consider the full environmental costs of packaging. Neo-liberalist competitive models do not address such problems convincingly, and therefore continued government intervention is required if the UK is to meet its targets under the EU Directive. Whilst economic instruments and competition provide avenues for a more effective environmental policy, there is a continuing need for government regulation rather than unquestioning faith in the benefits of the free market.     

Survival Model for Foot and Leg High Rate Axial Impact Injury Data

Objectives: Understanding how lower extremity injuries from automotive intrusion and underbody blast (UBB) differ is of key importance when determining whether automotive injury criteria can be applied to blast rate scenarios. This article provides a review of existing injury risk analyses and outlines an approach to improve injury prediction for an expanded range of loading rates. This analysis will address issues with existing injury risk functions including inaccuracies due to inertial and potential viscous resistance at higher loading rates.

Methods: This survival analysis attempts to minimize these errors by considering injury location statistics and a predictor variable selection process dependent upon failure mechanisms of bone. Distribution of foot/ankle/leg injuries induced by axial impact loading at rates characteristic of UBB as well as automotive intrusion was studied and calcaneus injuries were found to be the most common injury; thus, footplate force was chosen as the main predictor variable because of its proximity to injury location to prevent inaccuracies associated with inertial differences due to loading rate. A survival analysis was then performed with age, sex, dorsiflexion angle, and mass as covariates. This statistical analysis uses data from previous axial postmortem human surrogate (PMHS) component leg tests to provide perspectives on how proximal boundary conditions and loading rate affect injury probability in the foot/ankle/leg (n = 82).

Results: Tibia force-at-fracture proved to be up to 20% inaccurate in previous analyses because of viscous resistance and inertial effects within the data set used, suggesting that previous injury criteria are accurate only for specific rates of loading and boundary conditions. The statistical model presented in this article predicts 50% probability of injury for a plantar force of 10.2 kN for a 50th percentile male with a neutral ankle position. Force rate was found to be an insignificant covariate because of the limited range of loading rate differences within the data set; however, compensation for inertial effects caused by measuring the force-at-fracture in a location closer to expected injury location improved the model's predictive capabilities for the entire data set.

Conclusions: This study provides better injury prediction capabilities for both automotive and blast rates because of reduced sensitivity to inertial effects and tibia–fibula load sharing. Further, a framework is provided for future injury criteria generation for high rate loading scenarios. This analysis also suggests key improvements to be made to existing anthropomorphic test device (ATD) lower extremities to provide accurate injury prediction for high rate applications such as UBB.     

Estimating spatially-variable first-order rate constants in groundwater reactive transport systems

Numerical reactive transport models are often used as tools to assess aquifers contaminated with reactive groundwater solutes as well as investigating mitigation scenarios. The ability to accurately simulate the fate and transport of solutes, however, is often impeded by a lack of information regarding the parameters that define chemical reactions. In this study, we employ a steady-state Ensemble Kalman Filter (EnKF), a data assimilation algorithm, to provide improved estimates of a spatially-variable first-order rate constant λ through assimilation of solute concentration measurement data into reactive transport simulation results. The methodology is applied in a steady-state, synthetic aquifer system in which a contaminant is leached to the saturated zone and undergoes first-order decay. Multiple sources of uncertainty are investigated, including hydraulic conductivity of the aquifer and the statistical parameters that define the spatial structure of the parameter field. For the latter scenario, an iterative method is employed to identify the statistical mean of λ of the reference system. Results from all simulations show that the filter scheme is successful in conditioning the λ ensemble to the reference λ field. Sensitivity analyses demonstrate that the estimation of the λ values is dependent on the number of concentration measurements assimilated, the locations from which the measurement data are collected, the error assigned to the measurement values, and the correlation length of the λ fields.     

Interlaborafory Comparison of Formaldehyde Emissions from Particleboard Underlayment in Small-Scale Environmental Chambers

Formaldehyde (CH₂O) emissions from particleboard underlayment have been measured in 0.17 and 0.2 m³ chambers at separate laboratories to test the comparability of small scale environmental chamber measurements under different ventilation and product loading conditions. Absolute CH₂O calibration was established through intermethod comparison of different monitoring techniques against a CH₂O generation apparatus. Interlaboratory precision was enhanced via co-calibration of each laboratory’s CH₂O colorimetric analyzer against the same blank and bi-level generation source at the beginning and end of the study. The results show excellent intermethod and interlaboratory agreement in both the CH₂O calibration and particleboard emissions testing. The CH₂O emission rates of the test specimens demonstrate a Fick’s Law dependence on CH₂O vapor concentration. Measured CH₂O concentrations are described by a single-compartment, single emitter model, and are inversely proportional to the ratio [N/L (m/h)] of the air exchange rate [N(h^-1)] and product loading [L(m^-1)]. Comparison tests at varying N and L, but uniform N/L were performed; similar CH2O concentrations were measured for N and L levels selected from an indoor compartment model, and for fivefold larger N and L values, which are more convenient for small-scale chamber testing.     

Assessing President Obama’s climate change record

ABSTRACT

President Obama’s climate change record is assessed by looking at his success in translating policy goals into policy outputs (laws or regulatory action) during his time in office. Obama’s campaign speeches are examined to identify specific promises to take action on climate change before proceeding to examine whether, how and with what success he managed to act upon these pledges. Obama is shown to have set out a multi-pronged approach to deal with climate change in his campaign speeches and succeeded in translating many of his goals into policy outputs. This finding contributes to debates about Obama’s ‘green’ credentials.     

Quantification of pore clogging characteristics in potential permeable reactive barrier (PRB) substrates using image analysis

Permeable reactive barriers (PRBs) are now an established approach for groundwater remediation. However, one concern is the deterioration of barrier material performance due to pore clogging. This study sought to quantify the effect of pore clogging on the alteration of the physical porous architecture of two novel potential PRB materials (clinoptilolite and calcified seaweed) using image analysis of SEM-derived images. Results after a water treatment contaminated with heavy metals over periods of up to 10 months identified a decrease in porosity from c. 22% to c. 15% for calcified seaweed and from c. 22% to c. 18% for clinoptilolite. Porosity was reduced by as much as 37% in a calcified seaweed column that clogged. The mean pore size (2D) of both materials slightly decreased after water treatment with c. 11% reduction in calcified seaweed and c. 7% reduction in clinoptilolite. An increase in the proportion of crack-shaped pores was observed in both materials after the contaminated water treatment, most noticeably in the bottom of columns where contaminated water first reacted with the material. The distribution of pores (within a given image) derived from the distance transform indicated the largest morphological differences in materials was recorded in calcified seaweed columns, which is likely to impact significantly on their performance as barrier materials. The magnitude of porosity reduction over a short time period in relation to predicted barrier longevity suggest these and similar materials may be unsuited for barrier installation in their present form.     

A calibrated auction-conjoint valuation method: Valuing pork and eggs produced under differing animal welfare conditions

This paper develops a valuation method which generates consistent and systematic estimates of people's preferences for complex multi-attribute goods by inextricably linking auction bids with conjoint ratings. The advantage of the valuation approach is that it permits the estimation of people's values for many potential goods, allows one to decompose people's values for a good into its sub-components, and permits the study of preference heterogeneity without distributional assumptions. We apply the method to an important and increasingly controversial topic: animal welfare. The method is used to determine people's preferences for eggs and pork produced from different production systems. Data from experiments conducted in three diverse U.S. locations (Chicago, IL; Dallas, TX; and Wilmington, NC) indicates that people are, on average, willing to pay $0.95 more for a dozen eggs raised in an aviary, pasture system vs. a cage system, and are willing to pay $2.02 more for two-pounds of pork chops raised in a pasture system as opposed to a crate system.