Kriging method evaluation for assessing the spatial distribution of urban soil lead contamination

Describing contaminant spatial distribution is an integral component of risk assessment. Application of geostatistical techniques for this purpose has been demonstrated previously. These techniques may provide both an estimate of the concentration at a given unsampled location, as well as the probability that the concentration at that location will exceed a critical threshold concentration. This research is a comparative study between multiple indicator kriging and kriging with the cumulative distribution function of order statistics, with both local and global variograms. The aim was to determine which of the four methods is best able to delineate between "contaminated" and "clean" soil. The four methods were validated with a subset of data values that were not used in the prediction. Method performance was assessed by calculating the root mean square error (RMSE), analysis of variance, the proportion of sites misclassified by each method as either "clean" when they were actually "contaminated" or vice versa, and the expected loss for each misclassification type. The data used for the comparison were 807 topsoil Pb concentrations from the inner-Sydney suburbs of Glebe and Camperdown, Australia. While there was very little difference between the four methods, multiple indicator kriging was found to produce the most accurate predictions for delineating "clean" from "contaminated" soil.     

Capital assets and intercultural borderlands: socio-cultural challenges for natural resource management

In their design or implementation, many natural resource management (NRM) programs ignore critical socio-cultural dimensions of the challenge to advance sustainability. Building on particular ideas about culture and human ecosystems, we combine the strengths of the capital assets model of sustainability and the idea of intercultural borderlands to respond to this gap. To advance our thesis about the utility of these tools, we critically reviewed and analysed a cross-disciplinary literature relating to the socio-cultural dimensions of NRM. This paper stems from that labour and examines particular tensions that arise in land management as a result of Australians' specific colonial and postcolonial legacies. These tensions--related to ethnicity, gender, population, age and health--are among the threads in the larger tapestry that comprises the socio-cultural dimensions of NRM. For the Australian case, they are central, longstanding and persistent, and thus worthy of analysis; and they are applicable in general terms to other places with similar histories of settlement and land use.     

Improved protection for children in forward-facing restraints during side impacts

OBJECTIVE: This study aims to determine the potential for improved child occupant protection in side impacts that can be obtained using rigid and semi-rigid anchorage systems and the addition of energy-absorbing padding in the side structures of child restraints. METHODS: This study uses a comprehensive set of simulated side impacts to evaluate the potential for improved side impact protection in forward-facing child restraints. Factors investigated included methods of anchoring the restraint to the vehicle, energy-absorbing materials in the side structure of restraints, and design features of the restraints such as side wing geometry and seat belt routing. RESULTS: The results show clearly that completely rigid lower attachment of restraints offers the potential for great reductions in head injury risk, which anchorage systems employing a combination of a rigid anchorage bar and webbing attached to a child restraint cannot match. The addition of energy absorbing material in the side structure of restraint systems is effective when the head is fully contained within an adequately designed side wing structure. For restraints anchored by seat belts and loop style semi rigid anchorage straps, belt routing has the potential to significantly affect occupant head excursion. CONCLUSIONS: The results suggest that current child restraint standards and consumer testing protocols do not adequately encourage best practice design of child restraints for side impact protection.     

Hedonic Analysis of Effects of a Nonnative Invader (<Emphasis Type="Italic">Myriophyllum heterophyllum</Emphasis>) on New Hampshire (USA) Lakefront Properties

Introduced species are a major threat to the planet's ecosystems and one of the major causes of species extinction. This study deals with some of the economic impacts of one of these "invaders," variable milfoil. Variable milfoil can clog water-bodies, cause boating and swimming hazards, and crowd out native species. This study analyzed the effects of variable milfoil on shoreline property values at selected New Hampshire lakes. Results indicate that property values on lakes experiencing milfoil infestation may be considerably lower than similar properties on uninfested lakes. Results are highly sensitive to specification (variable selection) of the hedonic equation.     

Comparison of discharge silver concentrations from electrolytic plating and metallic replacement silver recovery units

Silver-based photographic X-ray film is made of solid crystals of silver chloride or silver bromide suspended in a gelatin and then coated on a film. During the X-ray developing process, the image is processed and the nonimage areas containing solid silver chloride or silver bromide crystals are removed in a solution called the fixer. There may be local environmental regulations that regulate the amount of silver discharged from a facility. To meet these regulations, many facilities have added silver recovery units to their processes. Two different types of recovery processes are in use in a large hospital and three clinics under study. All of the units were claimed by their respective manufacturers to be able to recover silver down to concentrations of 5 mg/L. This concentration would ensure that the building that houses each unit would meet the local county limit of 0.5 mg/L silver for total building silver discharge. The hypothesis for this research is that one system, newer and more expensive, consisting of so-called electrolytic plating units (EPUs) (which are followed by so-called metallic replacement units [MRUs] as a backup), will have better silver recovery than MRUs alone. A total of six units were sampled, three EPUs (in combination with MRUs) and three MRUs. The units were sampled once or twice a day for 10 days for a total of 17 samples from each. The samples then were analyzed by inductively coupled plasma spectroscopy, and an analysis of variance was performed on the results. The range for the electrolytic plating unit/metallic replacement unit combinations was 0.20-99.9 mg/L (mean of 35.15 mg/L; median of 33.8 mg/L). The range for the MRUs alone was 7.2-1112 mg/L (mean of 565.5 mg/L; median of 720 mg/L). Many individual results exceeded 5 mg/L, such that extensive dilution would be required to ensure the building effluent did not exceed 0.5 mg/L. It is suggested that the metallic replacement units be changed to EPUs (with metallic replacement backup units) because they had better silver recovery. Also, the EPU combinations need to be sampled regularly to ensure that their silver concentrations are at acceptable levels.     

The complete dechlorination of DDT by magnesium/palladium bimetallic particles

The complete dechlorination of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) by a magnesium/palladium bimetallic system has been accomplished. The reaction takes place under ambient temperature and pressure and mild reaction conditions requiring only 0.25 g of magnesium and 0.3% palladium (wt/wt) to drive the dechlorination of 100 microg DDT (50 ppm in 2 ml). The process is both rapid and complete requiring less than 10 min to attain total dechlorination within the detection limit (approximately 10 pg for DDT) of electron capture detection gas chromatography (GC-ECD). The major product formed, as deduced from mass spectrometry (GC-MS) is the hydrocarbon skeleton, 1,1-diphenylethane. This technology may allow for the development of an economic and environmentally benign method of DDT remediation.     

A multi-criteria geographic information systems approach for the measurement of vulnerability to climate change

A flexible procedure for the development of a multi-criteria composite index to measure relative vulnerability under future climate change scenarios is presented. The composite index is developed using the Weighted Ordered Weighted Average (WOWA) aggregation technique which enables the selection of different levels of trade-off, which controls the degree to which indicators are able to average out others. We explore this approach in an illustrative case study of the United States (US), using future projections of widely available indicators quantifying flood vulnerability under two scenarios of climate change. The results are mapped for two future time intervals for each climate scenario, highlighting areas that may exhibit higher future vulnerability to flooding events. Based on a Monte Carlo robustness analysis, we find that the WOWA aggregation technique can provide a more flexible and potentially robust option for the construction of vulnerability indices than traditionally used approaches such as Weighted Linear Combinations (WLC). This information was used to develop a proof-of-concept vulnerability assessment to climate change impacts for the US Army Corps of Engineers. Lessons learned in this study informed the climate change screening analysis currently under way.     

GDL then and now

The first comprehensive Graduated License (GDL) law was implemented in Florida in 1996. Now, most states have implemented one or more GDL provision including: extending the time for which a learners permit must be held prior to licensure; passenger restriction; and night driving restriction. Evidence to support each of these provisions existed prior to 1996 and has been largely confirmed with the evaluation of each new state to implement GDL. Nationally, fatal crash involvements of 16 year-old drivers have decreased 23% (1993-1995 vs. 2003-2005). Greater reductions have been seen for crash involvements at night and with passengers. The single most effective GDL provision appears to be the extension of the learners period when this extension has the effect of delaying the time at which unsupervised driving is permitted.