Matrix diffusion effects in the cleanup of heterogeneous aquifers

Simple mathematical models are developed to account for the rather slow mass transport of nonaqueous phase liquid (NAPL) into aqueous solution in groundwater during flushing operations. The models are based on the assumption that this bottleneck in the process is associated with diffusion in the aqueous phase in the porous medium from the location of the NAPL drops/ganglia in a region of relatively low permeability out into a region of substantially higher permeability, somewhat analogous to diffusion from a block of porous rock into a nearby fracture, where the fracture system overwhelmingly dominates the overall permeability. The models include batch flushing, flushing in a laboratory column, and a one-dimensional model for flushing by means of a single recovery well.     

Endogenous swimming rhythms underlying the spawning migration of the blue crab, Callinectes sapidus: ontogeny and variation with ambient tidal regime

Spawning female blue crabs, Callinectes sapidus, use ebb-tide transport (ETT) to migrate seaward. In estuaries with semi-diurnal tides, ETT in ovigerous blue crabs is driven by a circatidal rhythm in vertical swimming in which crabs ascend into the water column during ebb tide. The ontogeny of this rhythm was examined by monitoring swimming behavior of females before the pubertal molt, females that had recently undergone the molt but had not yet produced a clutch of eggs, and ovigerous females from an estuary with strong semi-diurnal tides. To assess variation in swimming rhythms with ambient tidal regime, swimming rhythms of ovigerous females from semi-diurnal (Beaufort, North Carolina), diurnal (St. Andrew Bay, Florida), and non-tidal (South River, North Carolina) estuaries were compared. Experiments were conducted during the summers of 2006–2008. Female crabs prior to oviposition had variable endogenous swimming rhythms (circadian, circatidal, or circalunidian). Ovigerous females from estuaries with semi-diurnal and diurnal tides had pronounced circatidal or circalunidian rhythms with swimming during the time of ambient ebb tide. Swimming rhythms of several ovigerous crabs switched between circatidal and circalunidian during the ~5-day observation period. Ovigerous crabs from a non-tidal estuary had a circadian rhythm with vertical swimming around the time of sunset. These results suggest that, while endogenous swimming rhythms are present in some female blue crabs prior to oviposition, rapid seaward movement via ETT in tidal estuaries begins following oviposition of the first clutch of eggs.     

Tetrodotoxin affects survival probability of rough-skinned newts (Taricha granulosa) faced with TTX-resistant garter snake predators (Thamnophis sirtalis)

Lethal chemical defenses in prey species can have profound effects on interactions with predators. The presence of lethal defenses in prey can correct the selective imbalance suggested by the life-dinner principle in which the fitness consequences of an encounter between predator and prey should be much greater for the prey species than the predator. Despite the apparent adaptive advantages of lethality the evolution of deadly prey presents a fundamental dilemma. How might lethal defenses confer an individual fitness advantage if both predators and prey die during interactions? We examined the interaction between the rough-skinned newt (Taricha granulosa), which contains a powerful neurotoxin called tetrodotoxin (TTX), and the common garter snake (Thamnophis sirtalis). In some sympatric populations, Th. sirtalis have evolved physiological resistance to TTX. Whether the newts’ toxin confers protection from snake predators or has been disarmed by the snakes’ physiological resistance has not yet been directly tested. In predator–prey trials, newts that were rejected by snakes had greater concentrations of TTX in their skin (4.52 ± 3.49 mg TTX/g skin) than those that were eaten (1.72 ± 1.53 mg TTX/g skin). Despite the plethora of taxa that appear to use TTX defensively, this is the first direct and quantitative demonstration of the antipredator efficacy of TTX. Because the survival probability of a newt (and thus fitness) is affected by individual TTX concentration, selection can drive the escalation of toxin levels in newts. The variable fitness consequences associated with both TTX levels of newts and resistance to TTX in snakes that may promote a strong and symmetrical coevolutionary relationship have now been demonstrated.     

Social organization in deer: Implications for localized management

Populations of white-tailed deer (Odocoileus virginianus) inhabiting many state and national parks and suburban areas have grown to the point that they conflict with human activities. Conflicts range from destruction of vegetation through browsing to public perception that diseases carried by deer pose threats to human health. Traditional modes of hunting to control populations are inappropriate in many of these areas because of intense human development and activity. This article explores an alternative approach for population reduction based on deer social organization. Female white-tailed deer are highly philopatric and female offspring remain near their dams for life. This suggests that a population expands slowly as a series of overlapping home ranges in a form analogous to the petals on a rose. Incorporating the rose petal concept into a model of population growth shows that removal of deer by family unit can potentially alleviate conflicts in localized areas for as many as 10–15 yr.     

DEVELOPMENT OF EARTH SATELLITE TECHNOLOGY FOR THE TELEMETRY OF HYDROLOGIC DATA1

ABSTRACT The use of satellite telemetry is playing a major role in the collection of hydrologic data. Advancing technology and availability of government satellites have permitted many agencies to take advantage of new procedures for acquiring data from automated remote data collection stations. Experiments with Earth satellite technology started in the 1960's and 1970's, with the polar-orbiting National Aeronautics and Space Administration Nimbus and Landsat satellites. Subsequent advancements took place through the development phase to operational systems using the Geostationary Operational Environmental Satellite (GOES) of the National Oceanic and Atmospheric Administration. This satellite system supports more than 2,500 active telemetry sites, of which approximately 1,200 are Geological Survey stream-gaging stations for the collection of hydrologic data. A satellite data collection system is made up of three primary components; a small battery-operated radio, and Earth-orbiting satellite, and an Earth receive and data processing station. The data relay satellites' vast aerial view of the Earth's surface gives satellite telemetry a large advantage over ground-based systems for the collection of real-time hydrologic data for flood warning, reservoir management, irrigation water control, hydropower generation, and the operation of hydrologic stations.     

Environmental application of aerial reconnaissance to search for open dumps

Three approaches to using aerial photography are evaluated for searching for open dumps in the state of Indiana. Photography with hand-held cameras from a small airplane proved more effective and flexible than either photo-interpretation of existing air photos or subcontracting to a federal agency for new aerial photography. The rationale for our choice of aerial reconnaissance, other uses of low-level aerial surveillance, the utility of small-format camera aerial photography for environmental analysis, and methods used for locating open dumps are discussed.     

Chemical Changes in Sediment Pore-Waters of an Acidic Mining Lake After Addition of Organic Substrate and Lime for Stimulating Lake Remediation

In the past five years, enclosures have beeninstalled in an acidic mining lake in Lusatia to investigate insitu remediation processes. They were treated with straw, withstraw and Carbokalk, or with Carbokalk alone, where Carbokalkis a by-product of the sugar industry (solid precipitate ofnon-sugars after lime clarification of extracted sugar beetjuice). Sediment samples were taken as cores to get informationabout the behaviour of organic and inorganic components insediment pore-water with depth. Vertical distributions of pH,soluble reactive phosphate, nitrate, ammonium, silica,aluminium, iron, manganese, calcium, magnesium, sodium,potassium, sulphate, and DOC were measured. The resultingprofiles, each consisting of 15 data points at differentdepths, were compared by cluster analysis. The similarities ofsediment cores from different treated enclosures relating toprofiles of chemical components were discussed. Increasedconcentrations of potassium and sulphate were found in pore-water after substrate treatment. The data imply dissolution ofpotassium iron sulphate hydroxide minerals (jarosite) after anincrease of pH caused by dissolution of lime and by sulphatereducing processes which were stimulated by organic substrateaddition.     

Fish bioassay monitoring of waste effluents

Spills of toxic materials into bodies of water receiving industrial waste discharges can be prevented only if frequent or continuous assessments of effluent quality can be made. Currently available methods can automatically measure individual physical or chemical waste components but cannot assess toxicity caused by the interaction of components or the presence of an unsuspected material. Aquatic organisms, in contrast, respond to their total environment and in this way integrate the effects of all the various chemical and physical waste parameters.This study evaluates the possibility of using the continuously and automatically recorded responses of fish to monitor the toxicity of industrial waste effluents. A review of previously developed toxicity monitoring systems is followed by a field evaluation of a method that uses the computer-monitored ventilatory patterns of 12 bluegills (Lepomis macrochirus Rafinesque) to monitor the toxicity of an industrial waste effluent as it flows into a river. No known toxic spills occurred in the effluent during the operation of this system, but acetone added to the effluent waste caused responses from the fish at concentrations which peaked near the 96-hr LC₅₀ level. Some responses were also noted when no known toxicant was present; these were related to environmental disturbances and system design problems. Recommendations are made for the design of future biologic monitoring units.     

Rhythms in larval release of the sublittoral crab Neopanope sayi and the supralittoral crab Sesarma cinereum (Decapoda: Brachyura)

Ovigerous females of the subtidal xanthid crab Neopanope sayi (Smith) and the high intertidal grapsid crab Sesarma cinereum (Bosc) were collected during the summers of 1986 and 1987 in the Beaufort, North Carolina (USA), area and brought into the laboratory, where rhythms in larval release were monitored. When crabs with late-stage embryos were put under a 14 h light:10 h dark cycle in an otherwise constant-environment room, an apparent tidal rhythm in release of larvae was observed for both species, with N. sayi releasing near the time of day and night high tides, and S. cinereum releasing around the time of night high tides. The time of sunset relative to high tide was a complicating factor, since larval release for both species was often concentrated around sunset when evening high tides fell several hours before sunset. When a group of N. sayi and S. cinereum were brought into the laboratory and placed under constant lowlevel light for 5 d, the release rhythm of the population persisted, thus implying that the rhythm is endogenous. Larval release near the time of high tide and often at night is common among brachyurans living in tidal areas, regardless of specific adult habitat, suggesting a common functional advantage. Possibilities include transport of larvae from areas where predation and the likelihood of stranding and exposure to low-salinity waters are high, as well as a reduced probability of predation on adult females. Results of the present study suggest that the importance of release after darkness may increase with increasing tidal height of the adult.