Phosphorus exchange in marine microplankton communities near Hawaii

Tracer exchange kinetics were consistent with the view that microplankton of waters near Hawaii produced and assimilated dissolved orthophosphate and dissolved compounds other than orthophosphate at roughly equal rates in experiments conducted in September, 1982. Using simple exchange models plus chemical measurements, we inferred that material other than orthophosphate could sometimes dominate the soluble molybdate-reactive pool (SRP), as is frequently the case in fresh waters. Where phosphorus exchange was most rapid, the tracer kinetics suggested that some fraction of the plankton community was disproportionately responsible for dissolved phophorus exchange. Comparisons against independent measurements of rapid phytoplankton turnover in these communities supported the conclusion that dissolved compounds other than orthophosphate were rapidly cycled and formed an important substrate for plankton growth.     

Self-Organizing Maps for Integrated Environmental Assessment of the Mid-Atlantic Region

A new method has been developed to perform environmental assessment at regional scale. This involves a combination of a self-organizing map (SOM) neural network and principal component analysis (PCA). The method is capable of clustering ecosystems in terms of environmental conditions and suggesting relative cumulative environmental impacts of multiple factors across a large region. Using data on land-cover, population, roads, streams, air pollution, and topography of the Mid-Atlantic region, the method was able to indicate areas that are in relatively poor environmental condition or vulnerable to future deterioration. Combining the strengths of SOM with those of PCA, the method offers an easy and useful way to perform a regional environmental assessment. Compared with traditional clustering and ranking approaches, the described method has considerable advantages, such as providing a valuable means for visualizing complex multidimensional environmental data at multiple scales and offering a single assessment or ranking needed for a regional environmental assessment while still facilitating the opportunity for more detailed analyses.     

Testicular histopathology in deer mice (Peromyscus maniculatus) following exposure to polychlorinated biphenyl

Adult deer mice testes were subjected to routine histopathology following exposure to Aroclor 1254 supplemented diet (5 ppm), for 30 days. Body and testicular weight revealed no statistical significance between the control and treated animals. From a histological standpoint the testes of the controls were similar to normal murids and other animals. In contrast, the testes from treated animals displayed seminiferous tubules with significant degenerative alterations. These alterations included fewer layers of seminiferous epithelium exaggerated intercellular spaces and appearance of pyknotic nuclei. Most tubules displayed subluminal nuclei that morphologically could be identified as part of spermatozoa heads and these usually lacked tails, indicating that the treatment interfered with spermiogenesis. Therefore, we concluded that Aroclor 1254 as an environmental contaminant is highly destructive to seminiferous tubules, and that these histological alterations undoubtedly are responsible for the depressed fertility in Peromyscus following chronic exposure to PCBs, that has been reported in the literature.     

Mayfly larvae (Baetis rhodani and B. vernus) as biomonitors of trace metal pollution in streams of a catchment draining a zinc and lead mining area of Upper Silesia,Poland

Larvae of two Baetis species were used to investigate spatial and temporal variability in the bioavailabilities of cadmium, copper, lead, zinc and iron in the river Biala Przemsza and its tributaries draining an area of lead and zinc mining in Upper Silesia, Poland. Accumulated metal concentrations were measured in April, May, August and November 2000. Both species indicated significant local geographical variability in availabilities of zinc, iron, lead and cadmium, but not copper. Accumulated concentrations of lead, zinc and cadmium confirmed the high general contamination of the Biala Przemsza system by these three trace metals. Larvae showed little seasonal variation in concentrations of cadmium, copper, lead and iron. Accumulated zinc concentrations were low in Baetis rhodani in August, perhaps as a result of insufficient time for high concentrations to accumulate since hatching of the larvae. Samples collected in August most nearly matched criteria of the greatest availability of larvae for collection and their size homogeneity, minimising the possibilities of any effect of differential larval size and/or age on accumulated metal concentrations. Mayfly larvae are members of a suite of potential stream biomonitors in Central Europe, which together can provide information on the different sources of bioavailable trace metals present in aquatic ecosystems.     

Recommended design for more accurate duplication of natural conditions in salt marsh creation

Construction of 653 ha of salt marsh habitat from dredged material near the Aransas National Wildlife Refuge, Texas, has been proposed, with the goal of increasing the area of habitat available to endangered whooping cranes (Grus americana). We assessed prototype created wetlands, and their similarity to natural reference sites, in terms of topography, vegetation, and hydrology. The created sites were steeply sloped relative to natural sites and were dominated by monotypic stands of Spartina alterniflora. Natural sites were dominated by vegetation more tolerant of desiccation and hypersalinity and by unvegetated salt pans. Differences in vegetation communities and distributions of habitat types resulted from efforts to enhance habitat diversity in created marsh cells through manipulation of marsh topography. However, the scale at which this diversity occurred in natural marsh of the study area was not considered. When constructing wetlands in cellular configurations, we recommend creation of large complexes of adjoining, hydrologically linked, cells wherein the desired habitat diversity is created at the scale of the entire complex, rather than within a single cell. Suggested design modifications would increase the similarity of created marshes to natural reference sites, potentially improving habitat function.     

From Superfund Site to Developable Property: The Case of Rentokil

The Comprehensive Environmental Response, Compensation, and Liability Act (42 USC §§9601 et seq.), commonly known as Superfund, was enacted on 11 December 1980 to facilitate the clean-up of hazardous waste sites. Superfund authorizes the Environmental Protection Agency (EPA) to compel responsible parties to clean up such sites. Superfund has been the source of extensive criticism since its inception. In response to this criticism, the EPA undertook a series of administrative reforms in 1993 to make the Superfund programme faster, fairer and more efficient. As of September 2000, active site remediation was complete at 757 (43%) of the 1779 national priority list (NPL) sites and 218 sites (12%) had been deleted from the NPL. Rentokil, a former wood-preserving plant on a 10 acre (4 ha) site in Henrico County, Virginia, was brought to the Virginia Health Department's attention as a threat to human health and the environment in 1989, was listed on the NPL the same year and was fully cleaned up in 1999. The cost of cleaning up Rentokil was $12 million, or $37.08 per square foot ($412 per square metre). The site is proposed to be redeveloped for tax-generating light industrial and commercial use. Rentokil reflects the EPA's implementation of several reforms geared toward reconciling cost considerations with remedy effectiveness and expedient implementation, and facilitating redevelopment. This case study's examination of Rentokil's progression through the Superfund process is intended to provide planning practitioners and students with insight into the Superfund programme and process, as well as an awareness of the challenges confronting Superfund's success.     

HYDRAULIC GEOMETRY RELATIONSHIPS FOR URBAN STREAMS THROUGHOUT THE PIEDMONT OF NORTH CAROLINA1

ABSTRACT: Hydraulic geometry relationships, or regional curves, relate bankfull stream channel dimensions to watershed drainage area. Hydraulic geometry relationships for streams throughout North Carolina vary with hydrology, soils, and extent of development within a watershed. An urban curve that is the focus of this study shows the bankfull features of streams in urban and suburban watersheds throughout the North Carolina Piedmont. Seventeen streams were surveyed in watersheds that had greater than 10 percent impervious cover. The watersheds had been developed long enough for the streams to redevelop bankfull features, and they had no major impoundments. The drainage areas for the streams ranged from 0.4 to 110.3 square kilometers. Cross‐sectional and longitudinal surveys were conducted to determine the channel dimension, pattern, and profile of each stream and power functions were fitted to the data. Comparisons were made with regional curves developed previously for the rural Piedmont, and enlargement ratios were produced. These enlargement ratios indicated a substantial increase in the hydraulic geometry for the urban streams in comparison to the rural streams. A comparison of flood frequency indicates a slight decrease in the bankfull discharge return interval for the gaged urban streams as compared to the gaged rural streams. The study data were collected by North Carolina State University (NCSU), the University of North Carolina at Charlotte (UNC), and Charlotte Storm Water Services. Urban regional curves are useful tools for applying natural channel design in developed watersheds. They do not, however, replace the need for field calibration and verification of bankfull stream channel dimensions.     

Implementing Sustainability: the Use of Natural Channel Design and Artificial Wetlands for Stormwater Management

Sustainability is a concept that has been widely embraced both politically and intellectually but has not been addressed in terms of practical application. In most resource sectors, the features of a sustainable future remain unclear and there are few examples that give practical expression to sustainability. This is especially true in the case of water resources management which has been conspicuous in its absence from the majority of the literature. This paper attempts to address this deficiency on two counts. First, it provides a discussion of sustainability and the application of the concept to the management of water resources. Second, the paper illustrates how the concept can be utilized for the management and planning of urban stormwater. The paper concludes by offering research opportunities to investigate the feasibility of adopting natural channel design and artificial wetlands for sustainable stormwater management.