Flow structure of unconfined turbidity currents interacting with an obstacle

Driven by a growing importance to engineered structures, investigating the flow characteristics of turbidity currents interacting with a basal obstruction has become popular over the last three decades. However, research has focused on confined studies or numerical simulations, whereas in situ turbidity currents are typically unconfined. The present study investigates experimentally the velocity and turbulence structure of an unconfined turbidity current, in the immediate regions surrounding a rectangular obstacle. Initial density of the current, and substrate condition is varied. Through a novel technique of installing ultrasonic probes within the obstacle, the presence of a velocity recirculation region immediately upstream and downstream of the obstacle is revealed and confirmed with high-resolution imagery. This was found to be comparable to previous confined studies, suggesting that stream-wise velocity profile structure is somewhat independent of confinement. The obstacle was found to reduce velocity and turbulence intensity maxima downstream of the obstacle when compared with unobstructed tests.     

Do farmers need relief seed? A methodology for assessing seed systems

This article outlines a methodology to help agencies better determine whether or not relief seed is needed by farmers affected by disaster. A brief review of current seed needs assessment procedures in southern Somalia and Mozambique illustrates problems of knowing which crops and households are affected, the importance of seed access (not just availability) and the need to plan interventions earlier than at present. The development of a Seed Systems Profile (SSP) is proposed to understand better both the socio-economic and agro-ecological aspects of farmers' seed systems. A five-step framework for assessing seed systems in disaster situations is also presented. These tools are currently being tested and further refined in Mozambique. A better understanding of farmers' seed systems will allow for the development of relief and rehabilitation interventions that effectively enhance the resilience and reduce the vulnerability of these systems.     

Influence of flow rate on transport of bacteriophage in shale saprolite

The objective of this study was to investigate the influence of flow rate on transport and retention of bacteriophage tracers in a fractured shale saprolite, which is a highly weathered, fine-grained subsoil that retains much of the fabric of the parent bedrock. Synthetic ground water containing PRD-1, MS-2, and bromide was passed through a saturated column of undisturbed shale saprolite at rates ranging from 0.0075 to 0.96 m d '. First arrival of the bacteriophage tracers in effluent samples in each of the experiments occurred within 0.01 to 0.04 pore volumes (PV) of the start of injection, indicating that bacteriophage were advectively transported mainly through fractures or macropores. Bacteriophage transport velocities, based on first arrival in the effluent, were very similar to fracture flow velocities calculated using the cubic law for flow in a fractured material. For MS-2, maximum concentration and mass of tracer recovered both increased steadily as flow rate increased. For PRD-1, these values initially increased, but were nearly constant at flow rates above 0.039 m d(-1), indicating that approximately 50% of the observed losses were independent of flow rate. Evaluation of the data indicates that physical straining and electrostatic or hydrophobic attachment to fracture or macropore walls were the dominant retention processes. Inactivation and gravitational settling playing secondary roles, except at the slowest flow rates. The study suggests that microbial contamination from sources such as septic fields and sewage ponds may pose a threat to the quality of ground water and surface water in areas with saprolitic subsoils.     

Phenanthrene degradation in soils co-inoculated with phenanthrene-degrading and biosurfactant-producing bacteria

Contaminant sorption within the soil matrix frequently limits biodegradation. However, contaminant bioavailability can be species-specific. This study investigated bioavailability of phenanthrene (PHE) to two PHE-degrading bacteria (Pseudomonas strain R and isolate P5-2) in the presence of rhamnolipid biosurfactant and/or a biosurfactant-producing bacterium, Pseudomonas aeruginosa ATCC 9027. Pseudomonas strain R mineralized more soil-sorbed PHE than strain P5-2, but in aqueous cultures the rate and extent of PHE mineralization by P5-2 exceeded that by P. strain R. In Fallsington sandy loam (fine-loamy, mixed, active, mesic Typic Endoaquult) (high PHE-sorption capacity) the addition of rhamnolipid increased PHE mineralization by P. strain R. Phenanthrene mineralization in soils inoculated with P5-2 was minimal and no enhancement in PHE degradation was observed when biosurfactant was added. Co-inoculation of Fallsington sandy loam with the biosurfactant producer did not affect PHE mineralization by isolate P5-2, but significantly enhanced PHE mineralization by P. strain R. The enhancement of PHE mineralization could not be explained by P. aeruginosa-mediated PHE degradation. The addition of rhamnolipid at concentrations above the critical micelle concentration (CMC) resulted in enhanced PHE release from test soils. These results suggest that the PHE-degrading strains were able to access different pools of PHE and that the biosurfactant-enhanced release of PHE from soils did not result in enhanced biodegradation. The results also demonstrated that bacteria with the catabolic potential to degrade sorbed hydrophobic contaminants could interact commensally with surfactant-producing strains by an unknown mechanism to hasten the biodegradation of aromatic hydrocarbons. Thus, understanding interactions among microbes may provide opportunities to further enhance biodegradation of soil-bound organic contaminants.     

Measuring and Incorporating Vulnerability into Conservation Planning

Conservation planning is the process of locating and designing conservation areas to promote the persistence of biodiversity in situ. To do this, conservation areas must be able to mitigate at least some of the proximate threats to biodiversity. Information on threatening processes and the relative vulnerability of areas and natural features to these processes is therefore crucial for effective conservation planning. However, measuring and incorporating vulnerability into conservation planning have been problematic. We develop a conceptual framework of the role of vulnerability assessments in conservation planning and propose a definition of vulnerability that incorporates three dimensions: exposure, intensity, and impact. We review and categorize methods for assessing the vulnerability of areas and the features they contain and identify the relative strengths and weaknesses of each broad approach. Our review highlights the need for further development and evaluation of approaches to assess vulnerability and for comparisons of their relative effectiveness.     

Organic nitrogen in precipitation across the United Kingdom

The concentration of water-soluble organic nitrogen (WSON) in precipitation has been measured at seven sites across the United Kingdom, over a period of 1–2 years, using protocols developed in a pilot study. Samples were collected over 1–2 weeks in continuously open funnels made of stainless steel, draining to a glass bottle, and were preserved during and after collection by the addition of thymol. After chemical analysis, samples were excluded from the long-term average if they showed signs of contamination (significant concentrations of K⁺ or PO₄ ^3?). Two methods of measuring total dissolved N were used, persulphate oxidation and high-temperature chemiluminescence. The latter generally gave the larger values, and has been used to asses the organic component of dissolved N. The long-term data set confirms the original results from the pilot study—organic N contributes between 24 and 40% to the total annual wet deposition of dissolved N across the United Kingdom. The fraction of WSON was greatest at western sites, and was strongly correlated with ammonium concentrations. However, the seasonal pattern across all sites showed a late spring maximum for ammonium and nitrate, but a late summer maximum for WSON. The magnitude of the contribution of WSON to wet-deposited N has implications for the setting and assessment of critical loads for N deposition.     

Recreational benefits of residual open space: A case study of four communities in northeastern New Jersey

Numerous undeveloped and ecologically diverse tracts of land within urban communities in the United States are presently being utilized for a variety of unsupervised recreational activities. The present use and perceived value of residual open spaces adjacent to the Palisades to residents of four communities in northeastern New Jersey was assessed. The results of our survey suggest that parks and open space represent a city service that is not as highly valued as other more visible services, that respondents desire a diversity of recreational experiences, that existing parks and open space provide a narrow range of recreational benefits to users, that benefits of existing parks extend primarily to the provision of active pursuits, and that undeveloped residual open spaces are valued for and provide opportunities for a variety of passive pursuits.Residual open spaces are a resource that contributes towards meeting the aesthetic and recreational needs of city residents. Failure by planners and decision-makers to recognize the value and utility of such tracts of land may result in their destruction and in the loss of a resource which provides a range of recreational opportunities that is not adequately provided by formal parks and open spaces.Paper of the Journal Series, New Jersey Agricultural Experiment Station, Cook College, Rutgers University, New Brunswick, New Jersey.This work was performed as a part of NJAES Project No. 17501, Urban Forestry: Planning and Management of Residual Open Space, supported by the New Jersey Agricultural Experiment Station and by a grant from the Consortium for Environmental Forestry Studies sponsored by the U.S. Department of Agriculture, Forest Service, Northeast Forest Experiment Station.     

DEVELOPMENT OF AN INTERDISCIPLINARY PLANNING MODEL FOR WATER AND FISHERY MANAGEMENT1

ABSTRACT: This paper describes the development of an interdisciplinary model that analyzes the effects of resource management decisions on New Mexico fishery production, yield, sportfishing effort, and economic benefit to anglers. The model recreates river flows and materials transported through reservoirs and their tailwaters from 1974 through 1987. Solar radiation, water temperature, phosphorus, nitrogen, suspended solids, and water exchange rates determine primary production. Organic loads from watershed sources, added to primary production, form a trophic base for sportfish forage. Fish production is partitioned into biomass and growth of each age class in sportfish and forage fish groups by differential responses to food type, light, water-level fluctuation and predation. Fish biomass, with angler population distribution and site condition, contributes to determining angler effort and economic benefits. Model users can vary and analyze water level and quality, stocking, fishing regulations, site access, site facilities, and site entry fees. The model (on floppy disks with a user manual) is available for operation on MS DOS compatible computers with a hard disk. Contact R. M. Wilson, NMGF, State Capitol, Santa Fe, New Mexico, 87503.     

Towards sustainable management of natural ecosystems on farms? a New Zealand perspective

Many New Zealand farms still have large remnant indigenous forest patches. This paper discusses constraints and opportunities for the sustainable management of these remnants. First, the paper analyses why the specific ecological situation of the New Zealand vegetation poses severe constraints for sustainable management. Second, results from a case study are presented suggesting that analysis of farmers’ attitudes to remnant ecosystems might provide valuable data for improving existing environmental legislation. Finally, the possible management implications of the new Resource Management Act 1991 and Forest Amendment Act 1993 are discussed. It is argued that these Acts may bring to an end a thousand years of wilful and accidental destruction of New Zealand's natural environment.