Exploring the links between health and housing: The limitations of population health surveys

While it is intuitively attractive to link health status and the quality of housing, it is methodologically complex to identify the relative importance of housing because individual characteristics and environmental variables act as confounders. A secondary issue is that the data sets which contain detailed data on health status and environmental variables often contain only limited data on housing. Similarly, housing surveys rarely contain detailed data on health and environmental variables. Respondents from Montreal, Toronto and Vancouver in the public use micro-data files of the 1996/97 cycle of the National Population Health Survey make up the data sets for a series of logistic regression models where health status, allergies, asthma, arthritis, migraines and bronchitis/emphysema act as the dependent variables. Sets of variables which measure housing, the environment (smoking and alcohol consumption) and the socio-economic status of individuals are used as independent variables. The issues of confounders and the limitations of the data are illustrated by the results of the analysis. If we are to go beyond local area surveys and carry out broader analyses of the links between health status and the quality of housing, researchers and data collection agencies will need to re-think the artificial divisions between these two critical aspects of peoples' lives.     

The behavior of apatite during crustal anatexis: Equilibrium and kinetic considerations

The solubility and dissolution kinetics of apatite in felsic melts at 850°–1500°C have been examined experimentally by allowing apatite crystals to partially dissolve into apatite-undersaturated melts containing 0–10 wt% water. Analysis of P and Ca gradients in the crystal/melt interfacial region enables determination of both the diffusivities and the saturation levels of these components in the melt. Phosphorus diffusion was identified as the rate-limiting factor in apatite dissolution. Results of four experiments at 8 kbar run in the virtual absence of water yield an activation energy (E) for P diffusion of 143.6 ± 2.8 kcal-mol^?1 and frequency factor (D₀) of 2.23^+2.88_?1.26 × 10⁹cm²-sec^?1. The addition of water causes dramatic and systematic reduction of both E and D₀ such that at 6 wt% H₂O the values are ~25 kcal-mol^?1 and 10^?5 cm²-sec^?1, respectively. At 1300°C, the diffusivity of P increases by a factor of 50 over the first 2% of water added to the melt, but rises by a factor of only two between 2 and 6%, perhaps reflecting the effect of a concentration-dependent mechanism of H₂O solution. Calcium diffusion gradients do not conform well to simple diffusion theory because the release of calcium at the dissolving crystal surface is linked to the transport rate of phosphorus in the melt, which is typically two orders of magnitude slower than Ca. Calcium chemical diffusion rates calculated from the observed gradients are about 50 times slower than calcium tracer diffusion.Apatite solubilities obtained from these experiments, together with previous results, can be described as a function of absolute temperature (T) and melt composition by the expression: In D^apatite/melt_P = [(8400 + ((SiO₂ ? 0.5)2.64 × 10⁴))/T] ? [3.1 + (12.4(SiO₂ ? 0.5))] where SiO₂ is the weight fraction of silica in the melt. This model appears to be valid between 45% and 75% SiO₂, 0 and 10% water, and for the range of pressures expected in the crust.The diffusivity information extracted from the experiments can be directly applied to several problems of geochemical interest, including I) dissolution times for apatite during crustal anatexis, and 2) pileup of P, and consequent local saturation in apatite, at the surfaces of growing major-mineral phases.     

Potential for localized groundwater contamination in a porous pavement parking lot setting in Rhode Island

The control of polluted surface runoff and the assessment of possible impacts on groundwater is a concern at the local and regional scale. On this background, a study investigates possible impacts of organic and inorganic pollutants (including bacteria) originating from a permeable asphalt parking lot on the water quality immediately beneath it. The functioning of the permeable pavement, including clogging and restricted vertical percolation, was also evaluated. Four nested sample ports (shallow and deep) were installed below low- and high-traffic areas, including one port outside the parking lot. At least initially there was a good hydraulic connection between the parking surface and the shallow sample ports. The presence of a geotextile layer at the base of the parking lot structure, however, was identified in lab tests as one factor restricting vertical percolation to the deeper ports. Clogging of the permeable surface was most pronounced in heavy traffic areas and below snow pile storage areas. Corroborated by high electric conductivity and chloride measurements, sand brought in by cars during winter was the principal cause for clogging. No bacteria or BOD were found in percolating water. Polycyclic aromatic hydrocarbons (PAH) were present at concentrations near minimum detection limit. Nutrients (nitrate and phosphate) were being leached into the ground via the permeable parking lot surface at annual flux rates of 0.45–0.84 g/m²/year. A multi-species tracer test demonstrated a retention capacity of the permeable parking lot structure of >90% for metals and 27% for nutrients, respectively.     

Transport of mecoprop from agricultural soils to an adjacent salt marsh

Salt marshes are important ecological areas and play a significant role in coastal flood defence schemes. In many areas of the UK they are adjacent to agricultural areas utilised for the growth of cereal crops, for which mecoprop is used as a selective herbicide in the control of broad-leaf weeds. This study measured concentrations of mecoprop in soils, drainage ditch waters and sediments and salt marsh sediments over a period of 138 days following spring application. Soil concentrations of up to 1827 microg/g were recorded after application, which demonstrated a half life for mecoprop of from 9 to 12 days, with first order kinetics. However, a major rainfall event 9 days after application resulted in significant transport of herbicide to the salt marsh via subsurface field drains, drainage ditches and discharge sluice. Mecoprop concentrations of up to 386 microg/l observed in water samples were above UK guidelines.     

Wind erosion and intensive prehistoric agriculture: A case study from the Kalaupapa field system,Moloka'i Island,Hawai'i

Wind erosion is a major problem for modern farmers, a key variable affecting nutrient levels in ecosystems, and a potentially major force impacting archaeological site formation; however, it has received scant consideration in geoarchaeological studies of agricultural development compared with more easily quantifiable environmental costs, such as vegetation change or fluvial erosion. In this study, soil nutrient analysis is used in the Kalaupapa field system, Moloka'i Island, Hawai'i, to detect an increase in wind erosion attributable to intensive agriculture following the burning of endemic forest. This practice began on a small scale in the 13th century A.D., expanded around cal A.D. 1450–1550, and continued until the near total abandonment of the fields after European contact in the 18th century. Nutrients that naturally occur in high amounts in coastal windward areas due to the long‐term, cumulative effect of sea spray were especially impacted. However, thanks to the unique landform of the Kalaupapa Peninsula, nutrient depletion in windward areas was offset by downwind enrichment and likely contributed to the long‐term sustainability of the system as a whole. Future research on tropical and arid agriculture should consider the cumulative environmental cost of increased eolian erosion attributable to anthropogenic landscape modification. © 2007 Wiley Periodicals, Inc.     

The effect of organic materials on the mobility and toxicity of metals in contaminated soils

Organic materials such as compost are often proposed as suitable materials for the remediation of contaminated brownfield sites intended for soft end-use. In addition to vitalising the soil, they are also believed to immobilise metals thereby breaking contaminant-receptor pathways and reducing the ecotoxicity of the contaminants. However, some research has demonstrated contradictory effects between composts on metal immobilisation. In the present study, four different composts and a liming product containing organic matter (LimeX70) were tested to examine both their metal retention and toxicity reduction capabilities on three different metal contaminated soils. Leaching tests, a plant growth test with Greek cress (Lepidium sativum), an earthworm (Eisenia fetida) survival and condition test and a bacterial toxicity test using Vibrio fischeri were carried out. The leaching test results showed that spent mushroom compost caused an increase in metal concentration in the leachates, while LimeX70 caused a decrease. The variation in behaviour between different amendments for each soil was high, so a generic conclusion could not be drawn. Toxicity tests showed significant reduction of metal bioavailability and toxicity for Greek cress, earthworms and bacteria. The results also suggest that more research should be undertaken to understand the mechanisms involved in metal complexation using different types of organic matter, in order to optimise the use of organic materials like compost for soil remediation.     

A smoothed particle hydrodynamics modelling of soil–water mixing and resulting changes in average strength

Soil–water interaction is a pivotal process in many underwater geohazards such as underwater landslides where soil sediments gradually evolve into turbidity currents after interactions with ambient water. Due to the large deformations, multiphase interactions and phase changes this involves, investigations from numerical modelling of the transition process have been limited so far. This study explores a simple numerical replication of such soil–water mixing with respect to changes in average strength using smoothed particle hydrodynamics (SPH). A uniform viscoplastic model is used for both the solid-like and fluid-like SPH particles. The proposed numerical solution scheme is verified by single-phase dam break tests and multiphase simple shear tests. SPH combinations of solid-like and fluid-like particles can replicate the clay–water mixture as long as the liquidity index of the solid-like particles is larger than unity. The proposed numerical scheme is shown to capture key features of an underwater landslide such as hydroplaning, water entrainment and wave generation and thus shows promise as a tool to simulate the whole process of subaquatic geohazards involving solid–fluid transition during mass transport.     

Predation on the rocky shores of Patagonia,Argentina

Rocky intertidal communities of Argentinean Patagonia are exposed to harsh physical conditions caused by dry, strong southern trade winds (mean speed 45 km h^-1, gusts up to 140 km h^-1) that result in intense desiccation of intertidal organisms. Predator distributions in these communities were evaluated from April 2003 to December 2004 at two exposed headlands and six protected bays in Cabo dos Bahias (44°50′S, 65°40′W). Crabs and sea stars dominated the predator assemblage, with occasional scavenger snails and fish also present. During low tide, predators were never found in the open but were always associated with shelter (primarily within mussel beds and coralline algae), suggesting a strong predator dependency on foundation species to buffer them from physical stress. Few predators (mostly crabs) emerged from shelter at high tide. Unlike the larger predators found on Chilean rocky shores, invertebrate predators in this system are diminutive, generally < 2 cm. The lone exception was the newly discovered invasive green crab,Carcinus mamas. Feeding trials, gut content analyses, and visual surveys indicated that native predators feed primarily on small, soft-bodied prey.C. mamas fed on slow-moving and sessile animals, including the super abundant musselPerumytilus purpuratus, with much greater voracity than native predators. Because native intertidal organisms are dependent on mussel beds and coralline algae for shelter from desiccation, successful invasion ofC. mamas may lead to a significant decrease in native diversity by consuming foundation species. This study represents a preliminary survey of predator distributions and feeding habits on the rocky shores of Argentinean Patagonia and provides important baseline data to evaluate trophic linkages and predatory effects on Patagonian rocky shores.     

When hazard avoidance is not an option: lessons learned from monitoring the postdisaster Oso landslide,USA

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

     

Use of sinkhole and specific capacity distributions to assess vertical gradients in a karst aquifer

The carbonate-rock aquifer in the Great Valley, West Virginia, USA, was evaluated using a database of 687 sinkholes and 350 specific capacity tests to assess structural, lithologic, and topographic influences on the groundwater flow system. The enhanced permeability of the aquifer is characterized in part by the many sinkholes, springs, and solutionally enlarged fractures throughout the valley. Yet, vertical components of subsurface flow in this highly heterogeneous aquifer are currently not well understood. To address this problem, this study examines the apparent relation between geologic features of the aquifer and two spatial indices of enhanced permeability attributed to aquifer karstification: (1) the distribution of sinkholes and (2) the occurrence of wells with relatively high specific capacity. Statistical results indicate that sinkholes (funnel and collapse) occur primarily along cleavage and bedding planes parallel to subparallel to strike where lateral or downward vertical gradients are highest. Conversely, high specific capacity values are common along prominent joints perpendicular or oblique to strike. The similarity of the latter distribution to that of springs suggests these fractures are areas of upward-convergent flow. These differences between sinkhole and high specific capacity distributions suggest vertical flow components are primarily controlled by the orientation of geologic structure and associated subsurface fracturing.