Method verification for determination of tetrachlorodibenzodioxin in soil

Methods for the determination of tetrachlorodibenzodioxin (TCDD) in surface and subsurface soil have been verified by spiking experiments conducted at a nominal level of twice the limit of detection. The methods involve Soxhlet extraction, silica and alumina clean-up and analysis by high resolution gas chromatography/ high resolution mass spectrometry. Mass Spectrometry done under profile data control is described. The precision (accuracy) found for surface and subsurface soils were 10.8% (85%) and 10.8% (95%) respectively. Application of the surface soil procedure is illustrated by analysis of soils from the Northeast United States.     

Allocation of reproductive effort in Mus domesticus: responses of offspring sex ratio and quality to social density and food availability

Summary Female mammals in good condition can maximize their inclusive fitness by investing more in male offspring than in female offspring during periods of poor environmental quality. To test this hypothesis, we measured the effects of undernutrition and crowding before and during gestation on the sex ratio and weight of offspring at parturition and at weaning in Mus domesticus. Sex ratio was not significantly affected by density. Dams altered the sex ratio of their offspring in response to food availability, but only if variance in competitive success within the experimental subpopulation was evident. Thus ad lib fed females produced litters with an unbiased sex ratio, competitively successful females under moderate food availability produced a male-biased sex ratio, and severely food deprived females produced litters with a female-biased sex ratio. In groups that experienced competition for food, successful dams favoured male offspring during lactation. These results are consistent with the predictions of Trivers and Willard (1973). Analysis of within-cell variance and covariance suggests that the interaction of social structure and food availability provides specific cues for the dams' tactical reproductive choices.     

Accumulation and release of petroleum-derived aromatic hydrocarbons by four species of marine animals

Survival of Ctenodiscus crispatus during exposure to hypoxia (P _{O 2}<3 mm Hg) at 5°C is greater than that of any echinoderm reported in the literature, the LT₅₀ being 248 h; this is reduced to 236 h in the presence of hydrogen sulfide. Unlike Asterias vulgaris and A. forbesi, both of which lose the tube foot response to tactile stimulation long before death from hypoxia occurs, C. crispatus remains responsive until death. The extension of the highly protrusible epiproctal cone, which occurs in 75% of the mud stars simultaneously exposed to hypoxia and H₂S, serves to maintain burrow contact with the overlying water. The rate of oxygen consumption remains constant down to an ambient oxygen partial pressure of 10 to 25 mm Hg, becoming more oxygen-dependent after prior exposure of the asteroids to hypoxia. C. crispatus exhibits a clear oxygen-debt phenomenon as well as a compensatory reduction in the residual P _{O 2} (oxygen partial pressure at which oxygen consumption ceases) from 2.4 to 0.2 mm Hg after hypoxic exposure.     

Protection from fishing alters the species composition of fish assemblages in a temperate-tropical transition zone

Closure of areas to fishing is expected to result in an increase in the abundance of targeted species; however, changes to populations of species not targeted by fishermen will depend upon their role in the ecosystem and their relationship with targeted species. The effects of protection on targeted and non-targeted reef fish species at the Houtman Abrolhos Islands, Western Australia were studied using baited remote underwater stereo–video cameras. Video images were collected from shallow (8–12 m) and deep (22–26 m) reef sites inside a Marine Protected Area (MPA) at each of three island groups and from three replicate fished locations at each of these groups that span a temperate-tropical transition area. The MPAs were established in 1994 and vary in size from 13.72 km² at the Pelsaert group in the south to 22.29 km² at the Easter group to 27.44 km² at the Wallabi group in the north. The relative abundances of 137 fish species from 42 families were recorded. Large differences in fish assemblage structure existed between MPA and fished locations, and also between shallow and deep regions. Targeted fish species Plectropomus leopardus, Lethrinus miniatus, Lethrinus nebulosus, Pagrus auratus and Glaucosoma hebraicum were more abundant inside MPAs than in areas open to fishing. Their abundance inside MPAs was between 1.13 and 8 times greater than their abundance at fished locations. For non-targeted fish species many were more abundant in areas open to fishing, e.g. Coris auricularis, Thalassoma lutescens, Thalassoma lunare, Dascyllus trimaculatus, however others were conversely more abundant inside MPAs, e.g. Gymnothorax spp, Kyphosus sydneyanus, Scarus microhinos, Chromis westaustralis, Chaetodon spp. This study demonstrates that the removal of abundant targeted species from an ecosystem by fishing can indirectly impact non-fished species and alter the trophic structure of fish assemblages. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

An empirical analysis of economic strategies for controlling air pollution

In evaluating current environmental protection policy, economists often note that current regulations are more costly than necessary to meet environmental quality standards. While the a priori case is strong that current regulatory approaches are resulting in higher-than-necessary costs to attain environmental standards, there is relatively little empirical evidence to support this claim. The purpose of this paper is to supply some of the missing evidence by presenting the results of one study that assesses some of the potential savings associated with implementing economic, rather than command-and-control, regulatory approaches to abate one type of air pollution in one region of the country. Specifically, the paper examines the costs of meeting a prospective short-term standard for nitrogen dioxide under a range of alternative emissions control strategies for stationary sources of nitrogen oxide emissions in the Chicago Air Quality Control Region. The alternative strategies that are considered range from those that might result under current regulatory policy to those that economic policy approaches (such as emissions charges or marketable permits) are designed to implement. The analysis shows that the most efficient program of emissions controls may be more than an order of magnitude less costly than current regulatory strategies, and that economic approaches have additional advantages over more conventional regulatory approaches.     

Practical Perspectives of 1,4‐Dioxane Investigation and Remediation

1,4‐Dioxane (dioxane) is a contaminant of emerging concern that is classified by the U.S. Environmental Protection Agency as a likely human carcinogen. Dioxane has been used as a minor or major ingredient in many applications, and is also generated as an unwanted by‐product of industrial processes associated with the manufacturing of polyethylene, nonionic surfactants, and many consumer products (cosmetics, laundry detergents, shampoos, etc.). Dioxane is also a known stabilizer of chlorinated solvents, particularly 1,1,1‐trichloroethane, and has been commonly found comingled with chlorinated solvent plumes. Dioxane plumes at chlorinated solvent sites can complicate site closure strategies, which to date have not typically focused on dioxane. Aggressive treatment technologies have greatly advanced and are clearly capable of achieving lower parts per billion cleanup criteria using ex situ advanced oxidation processes and sorption media. In situ chemical oxidation has also been demonstrated to effectively remediate dioxane and chlorinated solvents. Other in situ remedies, such as enhanced bioremediation, phytoremediation, and monitored natural attenuation, have been studied; however, their ability to achieve cleanup levels is still somewhat questionable and is limited by co‐occurring contaminants. This article summarizes and provides practical perspectives on dioxane analysis, plume stability relative to other contaminants, and the development of investigation tools and treatment technologies.     

Long-term individual identification and site fidelity of white sharks, <Emphasis Type="Italic">Carcharodon carcharias</Emphasis>, off California using dorsal fins

Mark-recapture techniques can be used to estimate white shark (Carcharodon carcharias) population abundance. These frameworks are based on assumptions that marks are conserved and animals are present at the sampling location over the entire duration of the study. Though these assumptions have been validated across short-time scales for white sharks, long-term studies of population trends are dependent on these assumptions being valid across longer periods. We use 22 years of photographic data from aggregation sites in central California to support the use of dorsal fin morphology as long-term individual identifiers. We identified five individuals over 16–22 years, which support the use of dorsal fins as long-time individual identifiers, illustrate strong yearly site fidelity to coastal aggregation sites across extended time periods (decades), and provide the first empirical validation of white shark longevity >22 years. These findings support the use of fin morphology in mark-recapture frameworks for white sharks.