Tracing sources of sulfur in the Florida Everglades

We examined concentrations and sulfur isotopic ratios (34S/32S, expressed as delta34S in parts per thousand [/1000] units) of sulfate in surface water, ground water, and rain water from sites throughout the northern Everglades to establish the sources of sulfur to the ecosystem. The geochemistry of sulfur is of particular interest in the Everglades because of its link, through processes mediated by sulfate-reducing bacteria, to the production of toxic methylmercury in this wetland ecosystem. Methylmercury, a neurotoxin that is bioaccumulated, has been found in high concentrations in freshwater fish from the Everglades, and poses a potential threat to fish-eating wildlife and to human health through fish consumption. Results show that surface water in large portions of the Everglades is heavily contaminated with sulfate, with the highest concentrations observed in canals and marsh areas receiving canal discharge. Spatial patterns in the range of concentrations and delta34S values of sulfate in surface water indicate that the major source of sulfate in sulfur-contaminated marshes is water from canals draining the Everglades Agricultural Area. Shallow ground water underlying the Everglades and rain water samples had much lower sulfate concentrations and delta34S values distinct from those found in surface water. The delta34S results implicate agricultural fertilizer as a major contributor to the sulfate contaminating the Everglades, but ground water under the Everglades Agricultural Area (EAA) may also be a contributing source. The contamination of the northern Everglades with sulfate from canal discharge may be a key factor in controlling the distribution and extent of methylmercury production in the Everglades.     

Contents of Volume 15

Volume Contents

Contents of Volume 15     

The Input and Transmission of Fallout Radionuclides Through Redó, a High Mountain Lake in the Spanish Pyrenees

Fallout radionuclides have increasing value as tracers of pathways for pollutant transport through catchment/lake systems, in addition to their more traditional role in dating sediment records. The objectivesof this study, carried out within the EU MOLAR project, were tomeasure atmospheric fluxes of fallout ²¹⁰Pb, ¹³⁷Cs and ⁷Be at Redó, to establish mass balances for theseradionuclides, and test and validate models of pollutant transport through the lake and its catchment. This was achieved by comparing measured fluxes and concentrations in the water column with theoretical estimates using simple compartment models. Several interesting points emerged. Differences betweensoil core and rainwater measurements suggest that Saharan dust may be an important source of fallout ²¹⁰Pb. Fluxes throughthe water column had a clear seasonal trend reflecting winter icecover. Significant concentrations of ¹³⁷Cs are still presentin the water column, due to continued inputs from the catchment and/or remobilisation from the bottom sediments.     

Pulling up roots in the 1990s: Who's willing to relocate?

The purpose of this study was to develop a profile of employees in Fortune 500 companies who are willing to relocate. The profile was developed on a demographically diverse random sample of 827 employees from 20 Fortune 500 corporations, all of whom had moved at least once for their current employer. Employees who were most willing to relocate were younger, their incomes were lower, their career ambitions higher, and their spouses more willing than those who were less willing to relocate. These employees could be found in sales/marketing and production functions. Their attitudes toward moving were also favorable. The single most important predictor of willingness to relocate was spouse willingness to relocate. This result suggests strongly that in the 1990s, corporations are going to have to address the concerns of spouses, if married employees are going to remain mobile. The study also cautions corporations about the shortsightedness of thinking of spouse and dual career issues as ’women's issues‘ and assuming that females and minorities are unwilling to relocate.     

Management of the zinc chain

In this study, a substance chain approach as a tool contributing to a sustainable development has been tested by applying it to zinc. An analysis of the western world zinc substance chain has been made in order to identify the main routes of zinc losses from the chain. Technologically feasible options to improve the management of the chain have been selected and applied to a modelled chain. With the emphasis on resource management, the model has been designed to evaluate the impact of options on the input of primary zinc into the chain. The consequences of the options for the energy resources have been analyzed.Redesigning the global zinc chain using the chosen technologically feasible options has lead to a lower primary zinc input when compared to the present chain, but a 45% primary zinc input is still needed, while the improved chain requires 8% less energy. To obtain a further decrease of primary zinc input in the chain, research should focus on emission abatement during zinc usage, where especially corrosion of galvanized steel forms a problem, and on the prevention of mixed-product waste streams with a low average zinc concentration. The energy analysis shows that options to improve the zinc chain should be carried out carefully, avoiding extra demands on the energy resources.The study indicates that designing a substance chain, along with even simple modelling, results in a good tool to calculate the impact of different kinds of options on the total chain.     

Dual earner couples: Attitudes and actions in restructuring work for family

In a matched data set consisting of survey responses from both members of 39 dual earner couples, work and family involvement was used to predict job satisfaction, marital satisfaction, stress and work restructuring of both members of the couple. In general, the wives were found to be restructuring their work activities more than their husbands. Couples whose members had high levels of family involvement were experiencing high levels of marital satisfaction and low levels of stress. In addition, the coded responses to seven open ended questions provided qualitative data reflecting what specific types of work restructuring arrangements were most popular and the reasons for work restructuring.     

Opportunity costs of implementing forest plans

Intellectual concern with the National Forest Management Act of 1976 has followed a course emphasizing the planning aspects of the legislation associated with the development of forest plans. Once approved, however, forest plans must be implemented. Due to the complex nature of the ecological systems of interest, and the multiple and often conflicting desires of user clientele groups, the feasibility and costs of implementing forest plans require immediate investigation. For one timber sale on the Coconino National Forest in Arizona, forest plan constraints were applied and resulting resource outputs predicted using the terrestrial ecosystem analysis and modeling system (TEAMS), a computer-based decision support system developed at the School of Forestry, Northern Arizona University, With forest plan constraints for wildlife habitat, visual diversity, riparian area protection, and soil and slope harvesting restrictions, the maximum timber harvest obtainable was reduced 58% from the maximum obtainable without plan constraints.Former Graduate Student at Northern Arizona University.     

NUMERICAL ANALYSIS OF PUMPING FROM CONFINED-UNCONFINED AQUIFERS1

ABSTRACT: A numerical method is presented for the analysis of a pumped well in a homogeneous aquifer with allowance made for the decrease in saturated depth, vertical components of flow, the possibility of regions of the aquifer changing between the confined and unconfined states and the effect of different outer boundaries. The method is based on a discrete space, backward difference time, approximation. A particular example considered in detail concerns heavy pumping from one of a regular array of wells in an unconfined aquifer until the drawdown in the well reaches a critical value. Non-dimensional curves are presented relating the time and volume dewatered to the quantity discharged from the well. A further example investigates the effect of an initial confining pressure on the aquifer behaviour.