Active capping demonstration in the Anacostia river,Washington, D.C.

An active capping demonstration project in Washington, D.C., is testing the ability to place sequestering agents on contaminated sediments using conventional equipment and evaluating their subsequent effectiveness relative to conventional passive sand sediment caps. Selected active capping materials include: (1) AquaBlokTM, a clay material for permeability control; (2) apatite, a phosphate mineral for metals control; (3) coke, an organic sequestration agent; and (4) sand material for a control cap. All of the materials, except coke, were placed in 8,000‐ft test plots by a conventional clamshell method during March and April 2004. Coke was placed as a 1.25‐cm layer in a laminated mat due to concerns related to settling of the material. Postcap sampling and analysis were conducted during the first, sixth, and eighteenth months after placement. Although postcap sampling is expected to continue for at least an additional 24 months, this article summarizes the results of the demonstration project and postcap sampling efforts up to 18 months. Conventional clamshell placement was found to be effective for placing relatively thin (six‐inch) layers of active material. The viability of placing high‐value or difficult‐to‐place material in a controlled manner was successfully demonstrated with the laminated mat. Postcap monitoring indicates that all cap materials effectively isolated contaminants, but it is not yet possible to differentiate between conventional sand and active cap layer performance. Monitoring of the permeability control layer indicated effective reductions in groundwater seepage rates through the cap, but also showed the potential for gas accumulation and irregular release. All of the cap materials show deposition of new contaminated sediment onto the surface of the caps, illustrating the importance of source control in maintaining sediment quality. © 2006 Wiley Periodicals, Inc.     

公园游客管理概念的演变

要保护公园的生态、社会、经济和文化价值 ,游客管理具有根本的重要性 . 政府要求公园进一 步在财政上自给自足 . 正在制定一个更加完善的管理方法代替单纯地限制游客的数量 . 这种 方法鼓励公众参与公园的目标设定和游客满意度评价 ,并奖励胜任的财务管理 .     

Prenatal diagnosis and intrafamilial clinical heterogeneity of Fraser syndrome

Fraser syndrome (MIM 219000) is a rare disorder of autosomal recessive inheritance, characterized by the association of cryptophthalmos, syndactyly and genital abnormalities. Here we report on two cases of Fraser syndrome (cryptophthalmos syndrome) in a non-consanguineous couple, with variable expression in echographic, clinical and autopsy findings. Furthermore, we highlight the difficulties in prenatal diagnosis of Fraser syndrome. Copyright © 2002 John Wiley & Sons, Ltd.     

Effects of ocean temperature on the southern range limits of two understory kelps, <Emphasis Type="Italic">Pterygophora californica</Emphasis> and <Emphasis Type="Italic">Eisenia arborea</Emphasis>, at multiple life-stages

Environmental factors have long been shown to influence species distributions, with range limits often resulting from environmental stressors exceeding organism tolerances. However, these abiotic factors may differentially affect species with multiple life-history stages. Between September 2004 and January 2006, the roles of temperature and nutrient availability in explaining the southern distributions of two understory kelps, Pterygophora californica and Eisenia arborea (Phaeophyceae, Laminariales), were investigated along the coast of California, USA and the Baja California Peninsula, Mexico, by limiting either: (a) tissue nitrogen uptake and storage by adult sporophytes during periods of elevated temperature, and/or (b) production of embryonic sporophytes by microscopic gametophytes. Results suggest that while adult sporophytes of both species are tolerant of high temperatures and low nutrients, reproduction by their microscopic stages is not. Specifically, while E. arborea produced embryonic sporophytes at both 12 and 18°C, temperatures commonly observed throughout the southern portion of its range, P. californica produced sporophytes at 12 but not at 18°C. As a result, it appears that the southern distribution of P. californica, which ends in northern Baja California, Mexico, may be limited by temperature acting on its microscopic stages. In contrast, the ability of E. arborea’s microscopic and adult stages to tolerate elevated temperatures allows it to persist in the warmer southern waters of Baja California, as well as to the north along the California coast where both species co-occur.