DETECTING CILANGES IN THE SPATIAL DISTRIBUTION OF NITRATE CONTAMINATION IN GROUND WATER1

ABSTRACT: Many studies of ground water pollution in general and nitrate contamination in particular have often relied on a one-time investigation, tracking of individual wells, or aggregate summaries. Studies of changes in spatial distribution of contaminants over time are lacking. This paper presents a method to compare spatial distributions for possible changes over time. The large-scale spatial distribution at a given time can be considered as a surface over the area (a trend surface). The changes in spatial distribution from period to period can be revealed by the differences in the shape and/or height of surfaces. If such a surface is described by a polynomial function, changes in surfaces can be detected by testing statistically for differences in their corresponding polynomial functions. This method was applied to nitrate concentration in a population of wells in an agricultural drainage basin in Iowa, sampled in three different years. For the period of 1981–1992, the large-scale spatial distribution of nitrate concentration did not show significant change in the shape of spatial surfaces; while the magnitude of nitrate concentration in the basin, or height of the computed surfaces showed significant fluctuations. The change in magnitude of nitrate concentration is closely related to climatic variations, especially in precipitation. The lack of change in the shape of spatial surfaces means that either the influence of land use/nitrogen management was overshadowed by climatic influence, or the changes in land use/management occurred in a random fashion.     

Homophily and Agency: Creating Effective Sustainable Development Networks

Community networks are self-organized groupings that form for many different reasons. Some networks, connected mainly through bonding ties, are based on personal interests and relationships; others, based mainly on bridging ties, centre around broader interests. These networks form to create collective agency for engaging with social, environmental, and other issues through the concentration of social capital. The multi-scaled and evolutionary nature of sustainable development issues requires that community groups dedicated to engaging with such issues be particularly diverse, resilient, and flexible. As such, they must build a large number of bridging ties leading to external resources and limit the potential for bonding ties to impose constraining norms upon the group. Over time, however, volunteer groups tend towards a state of homophily, the tendency of groups to form from similar actors and then become more similar with time. This tendency leads to a decrease in the number of the bridging ties that help to provide group agency. Homophily must be actively recognized within community sustainable development groups if they are to remain effective over the long term. This paper suggests methods to prevent and control group homophily drawn from experience in forming small, time-limited sustainable development networks. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue     

Mine capacity and mineral price

The loss of foreign mineral supplies may affect domestic supply and price. To investigate the assumption that prices, a simple mine investment model that relates mine capacity to deposit attributes is used. A test of the model to see how well it approximates industry investment practice illustrates its accuracy. The model suggests that price changes can substantially affect the optimal capacity of planned or existing mines as well as the mineral supply in the USA.     

Selection, preparation, and disposal of sodium compounds for dry SOx scrubbers

A program has been initiated to assess an SO₂ removal method wherein dry powdered sodium compounds are injected into the gas stream ahead of the baghouse filter. The compounds are collected on the surface of the filter bags for reaction with the gaseous SO₂. Initial program efforts include a survey of suitable and available sodium compounds, methods of preparing the compounds for injection, and an invistigation of environmentally acceptable methods of disposal.     

The effects of oil spill chemicals on carbon translocation rates in Phaseolus vulgaris L

Phaseolus vulgaris L. cv. Black Valentine when sprayed with Corexit dispersants shows a rapid inhibition of photosynthesis. The plant retains the ability to translocate fixed carbon, and this involves mobilising previously fixed carbon in the sprayed leaf or the repartitioning of carbon from unsprayed regions of the plant towards the growing sink regions. The ability to maintain carbon translocation while photosynthesis is declining maximises the regrowth potential of the plant.     

Replacement of a multiple hearth by a fluid bed incinerator the Greensboro case history

The incinerator at the T.Z. Osborne Plant in Greensboro, North Carolina burns sludge from its own waste water treatment plant and sludge pumped from the nearby North Buffalo plant. The two plants have a combined capacity of 36 million gallons per day of wastewater. Because of the age of and increasing high maintenance on the existing multiple hearth incinerator, and the need to increase treatment capacity, the Osborne plant concluded a study in 1992 evaluating its options for future municipal sewage sludge disposal. Options which were evaluated during the study included; (i) rehabilitation of the existing eight-year old multiple hearth unit; (ii) addition of a new multiple hearth; (iii) addition of a new fluid bed system; (iv) drying, composting, or land application. The chosen option, based on both economic and environmental considerations, was a new fluid bed system with a capacity of 2.55 tons per hour, approximately double that of the existing multiple hearth. Design of the new fluid bed system began in December 1994 and equipment delivery for the incineration system was begun in April 1995. Initial operation occurred in August 1996. Primary and secondary sludge, dewatered to 28% dry solids by centrifuge, is delivered by piston pumps to the twenty-foot freeboard ID incinerator. A shell and tube heat exchanger recuperates heat from the exhaust gas and preheats the combustion air to 1250°F, resulting in minimal auxiliary fuel use. The air pollution control device is a high-energy Tandem Nozzle® scrubber. Greensboro was the initial installation of this scrubber design on a fluid bed incinerator and its characteristics and performance are discussed. Ash is dewatered in an ash thickener/belt press system prior to disposal to landfill. The system includes a state of the art Programmable Logic Controller (PLC) system for computer control of the operation. The unit was commissioned in August 1996 and has been in continuous operation since that time except for a one week inspection and maintenance shutdown in February 1999. The plant operates 24 h/day, 7 days per week. The initial performance test showed the system to readily meet federal and state air emission standards. Particulate released was 0.002 grains per dry standard cubic foot, carbon monoxide was 22.5 parts per million volumetric (ppmv) and opacity was 0.4%. These results show a significant emission reduction with the fluid bed when compared to the multiple hearth. Annual tests conducted since then and continuous emission monitoring have shown the unit to be in consistent compliance. Since the fluid bed system became operational, the old multiple hearth system has been maintained on standby as a backup, but its use has not been required. Operational experience is discussed, the most interesting of which is the relatively trouble-free operation. The minor problems which occurred and their solutions are detailed. Also included is a comparison of operation and maintenance experience of the fluid bed and the multiple hearth. Current sludge disposal actual cost data are also provided including the average cost per ton of dry solids treated. The almost three years of operational experience to date has shown that the decision to install a new fluid bed system was the correct one on both an environmental and economic basis. It has provided benefits to all interested parties — the wastewater treatment plant, the regulators, the taxpayers, and the surrounding community.     

Sperm traits in the quacking frog (<Emphasis Type="Italic">Crinia georgiana</Emphasis>), a species with plastic alternative mating tactics

In species where males use alternative reproductive tactics and male phenotypes are confronted with different risks of sperm competition, theory predicts that between-male-type differences in sperm expenditure may evolve. In the frog Crinia georgiana big males can monopolize females, whereas small males often engage in polyandrous matings. Consequently, big males may experience a lower risk of sperm competition than do small males. We tested if the predictions from theoretical models can be applied to the mating system of C. georgiana. Our results showed that small males do not have larger testes relative to their body size compared to their larger counterparts and that the efficiency with which sperm number, size, motility, and longevity are produced by the testes does not differ between small and large males in the predicted way. These results are not in alignment with predictions from a loaded raffle model of sperm competition on sperm expenditure in males with alternative phenotypes. The plasticity in mating tactics used by C. georgiana males and a high intraseasonal variation in male densities may have prevented the evolution of enhanced sperm performance in smaller males. A fair raffle in the sperm competition game played by C. georgiana males could also explain the observed patterns in sperm traits. Future investigations determining the parameters responsible for the deviation from theoretical predictions in this system will test the degree to which current theoretical models can indeed be applied to species with plastic reproductive tactics.     

Ornamental Marine Species Culture in the Coral Triangle: Seahorse Demonstration Project in the Spermonde Islands,Sulawesi, Indonesia

Ornamental marine species (‘OMS’) provide valuable income for developing nations in the Indo-Pacific Coral Triangle, from which most of the specimens are exported. OMS culture can help diversify livelihoods in the region, in support of management and conservation efforts to reduce destructive fishing and collection practices that threaten coral reef and seagrass ecosystems. Adoption of OMS culture depends on demonstrating its success as a livelihood, yet few studies of OMS culture exist in the region. We present a case study of a land-based culture project for an endangered seahorse (Hippocampus barbouri) in the Spermonde Islands, Sulawesi, Indonesia. The business model demonstrated that culturing can increase family income by seven times. A Strengths Weaknesses Opportunities Threats (SWOT) analysis indicated good collaboration among diverse stakeholders and opportunities for culturing non-endangered species and for offshoot projects, but complicated permitting was an issue as were threats of market flooding and production declines. The OMS international market is strong, Indonesian exporters expressed great interest in cultured product, and Indonesia is the largest exporting country for H. barbouri. Yet, a comparison of Indonesia ornamental marine fish exports to fish abundance in a single local market indicated that OMS culture cannot replace fishing livelihoods. Nevertheless, seahorse and other OMS culture can play a role in management and conservation by supplementing and diversifying the fishing and collecting livelihoods in the developing nations that provide the majority of the global OMS.