Migration of pollutants in groundwater. III. Numerical dispersion reduction with cartesian coordinates

The partial differential equation governing the movement of a decomposing pollutant undergoing 2-dimensional flow in a saturated aquifer is examined. The analytical solution of the equation is usually not possible, and use of mesh numerical integration techniques causes excessive numerical dispersion to arise from the advection term. We apply two asymmetrical upwind formulas to approximate the advection term. These markedly reduce numerical dispersion without requiring the use of coordinate systems obtained by conformal mapping. Flow within a right angle and flow toward a sink in an otherwise uniform field are analyzed to illustrate the methods.     

Perceived Impacts of Ecotourism on Environmental Learning and Conservation: Turtle Watching as a Case Study

Using a case study, involving turtle-based ecotourism, we explore the role of ecotourism in promoting environmental learning and in sustaining conservation of nature. Mon Repos Conservation Park (an important marine turtle rookery involved in ecotourism) in Queensland, Australia, was selected for this study and visitors were surveyed using a structured questionnaire. The reported on-site experiences of respondents are analysed to identify important factors that alter their stated conservation attitudes and behaviours. The impact of these factors (such as the amount of environmental education that respondents claimed they obtained, sighting of sea turtles, nationality) is quantified using regression analyses. There has been little previous quantification of such influences. The study reveals that a considerable amount of environmental knowledge is gained by visitors to Mon Repos. The ecotourism experience, involving environmental education and seeing of turtles, was found to have positive and statistically significant impacts on the visitors' stated desire and intended behaviour to protect sea turtles. The study reveals the importance of learning and the interaction of tourists with wildlife as a contributor to their pro-conservation sentiments and actions. It shows how ecotourism can support nature conservation. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Dispersion of Tellina tenuis from Kames Bay,Millport, Scotland

The dispersion of Tellina tenuis da Costa in the laboratory was analysed by the Clark and Evans nearest-neighbour test and by the Kolmogorov-Smirnov one-sample test. The dispersion was random, with a slight tendency toward aggregation that was independent of density. In the field, the dispersion was analysed by the Clark and Evans nearest-neighbour test and by the X² approximation to Fisher's coefficient of dispersion. The dispersion was again random, this time with a slight tendency toward spacing out that was independent of density. The tendency toward aggregation displayed in the laboratory was independent of the dispersion pattern shown at the start of the experiment, and also unaffected by the edge of the container. The apparent randomness suggests that T. tenuis is primarily a suspension feeder, but may be a deposit feeder under certain environmental conditions.     

Jellyfish aggregations and leatherback turtle foraging patterns in a temperate coastal environment

Leatherback turtles (Dermochelys coriacea) are obligate predators of gelatinous zooplankton. However, the spatial relationship between predator and prey remains poorly understood beyond sporadic and localized reports. To examine how jellyfish (Phylum Cnidaria: Orders Semaeostomeae and Rhizostomeae) might drive the broad-scale distribution of this wide ranging species, we employed aerial surveys to map jellyfish throughout a temperate coastal shelf area bordering the northeast Atlantic. Previously unknown, consistent aggregations of Rhizostoma octopus extending over tens of square kilometers were identified in distinct coastal "hotspots" during consecutive years (2003-2005). Examination of retrospective sightings data (>50 yr) suggested that 22.5% of leatherback distribution could be explained by these hotspots, with the inference that these coastal features may be sufficiently consistent in space and time to drive long-term foraging associations.     

Young driver risk in relation to parents' retrospective driving record

PROBLEM: Parents are an important potential influence on the driving safety of their children. This study examined the relationship of parental driving record on male and female offspring's at-fault collision risk. METHOD: Drivers aged 16-21 on the date of full licensure were selected from driver records and a matching process was used to identify putative parents in two-parent households. Poisson regression models were developed to predict at-fault collisions of male and female youth in the three years following full licensure from parents' at-fault collisions, speeding offenses, and other moving offenses in the four years prior to children's licensure. One set of models examined the relative risk associated with increasing numbers of maternal and paternal at-fault collisions and offenses. Other models examined the joint versus separate maternal and parental contributions. RESULTS: Controlling for region of residence, both mothers' and fathers' at-fault collisions were associated with an increased risk in both male and female youth at-fault collisions. Mothers' and fathers' speeding offenses were also associated with increased relative risk of at-fault collisions for both sons and daughters, while fathers' other moving offenses increased collision risk for sons but not daughters. DISCUSSION: Further research is required to identify how parental driving risk is transmitted to children. IMPACT ON INDUSTRY: (a) Parents of young children should be informed of their role in influencing their children's future driving risk; (b) The results identify risk factors that could be of interest to licensing authorities and the insurance industry.     

Sleepiness among night-time drivers: relationship to blood alcohol concentration and other factors

OBJECTIVE: The study aimed to explore the distribution and correlates of subjective sleepiness among the general night-time driving population. METHODS: The survey took place in three British Columbia communities in June 2003 between 21:00 hours to 03:00 hours. Sites and vehicles were selected randomly. Surveyors obtained information on several demographic and situational variables including self-assessed degree of sleepiness and self-reported hours asleep and awake, as well as an objective measure of blood alcohol concentration obtained from a hand-held breath-testing device. RESULTS: The total compliance rate among intercepted drivers was 85%. Among the 2335 drivers responding to the questionnaire, 68.4% indicated that they were wide awake, 27.6% were somewhat sleepy, and 4.1% were very sleepy. Logistic regression quantified the independent contributions of the various factors to subjective sleepiness. Male drivers with positive blood alcohol concentrations under 50 mg% were more likely to report feeling sleepy than those with either higher or with zero blood alcohol concentration. Greater relative risk of sleepiness was also associated with being female, being under age 55, and advanced hour of night. Driving with passengers of the same gender was associated with lower reported sleepiness. CONCLUSIONS: A substantial proportion of night-time drivers are driving while sleepy, especially at late night and early morning hours. The combination of alcohol and sleepiness compounds impairment in experimental studies and deserves greater attention in crash risk studies and as a topic for public education and awareness.     

Energy flows in the coffee plantations of Costa Rica: from traditional to modern systems (1935–2010)

Regional Environmental Change - This article addresses energy flows in the coffee agro-ecosystems of Costa Rica within the context of the socio-ecological transition, between 1935 and 2010,...     

Agroecosystem energy transitions: exploring the energy-land nexus in the course of industrialization

Regional Environmental Change -     

Pond bank access as an approach for managing toxic cyanobacteria in beef cattle pasture drinking water ponds

Forty-one livestock drinking water ponds in Alabama beef cattle pastures during were surveyed during the late summer to generally understand water quality patterns in these important water resources. Since livestock drinking water ponds are prone to excess nutrients that typically lead to eutrophication, which can promote blooms of toxigenic phytoplankton such as cyanobacteria, we also assessed the threat of exposure to the hepatotoxin, microcystin. Eighty percent of the ponds studied contained measurable microcystin, while three of these ponds had concentrations above human drinking water thresholds set by the US Environmental Protection Agency (i.e., 0.3 μg/L). Water quality patterns in the livestock drinking water ponds contrasted sharply with patterns typically observed for temperate freshwater lakes and reservoirs. Namely, we found several non-linear relationships between phytoplankton abundance (measured as chlorophyll) and nutrients or total suspended solids. Livestock had direct access to all the study ponds. Consequently, the proportion of inorganic suspended solids (e.g., sediment) increased with higher concentrations of total suspended solids, which underlies these patterns. Unimodal relationships were also observed between microcystin and phytoplankton abundance or nutrients. Euglenoids were abundant in the four ponds with chlorophyll concentrations >?250 μg/L (and dominated three of these ponds), which could explain why ponds with high chlorophyll concentrations would have low microcystin concentrations. Based on observations made during sampling events and available water quality data, livestock-mediated bioturbation is causing elevated total suspended solids that lead to reduced phytoplankton abundance and microcystin despite high concentrations of nutrients, such as phosphorus and nitrogen. Thus, livestock could be used to manage algal blooms, including toxic secondary metabolites, in their drinking water ponds by allowing them to walk in the ponds to increase turbidity.