Dense Nonaqueous Phase Liquid Tracer Tests: Experimental Results

Two dense nonaqueous phase liquid (DNAPL) tracer tests werecarried out in a shallow aquifer north of Fort Worth, TX. i-Propanolwas used as the nonpartitioning tracer; n-hexanol and n-octanol werethe partitioning tracers. Field data, mathematical modeling, theresults of column tests, and field tracer tests with NaCl were usedin designing the DNAPL tracer tests. The results indicated the presenceof DNAPL at both sites tested; semi-quantitative estimates of theamounts of DNAPL present were obtained by mathematical modeling.Interpretation was complicated by heterogeneity of the aquifer andmass transport effects.     

Nonpoint source of nutrients and herbicides associated with sugarcane production and its impact on Louisiana coastal water quality

A watershed analysis of nonpoint-source pollution associated with sugarcane (Saccharum officinarum L.) production was conducted. Runoff water samples following major rainfall events from two representative sugarcane fields (SC1 and SC2) were collected and analyzed. The impact of runoff on two receiving water bodies, St. James canal (SJC) and Bayou Chevreuil (BC) in a drainage basin (Baratarian Basin), was studied. Results show that runoff flow/rainfall ratios at the SC1 were significantly higher (P < 0.0001, n = 14) than at the SC2, probably mainly due to higher sand content and higher infiltration rate of surface soil at the SC2. In runoff water samples, total suspended solids (TSS) showed a significant correlation with the concentrations of N and P. Sugarcane runoff showed a direct impact on the SJC and BC locations where seasonal variations of pollutant concentrations in the waters followed the patterns of runoff loadings. Swamp forest runoff (SFR) location showed a buffering effect of forested wetlands on water quality with the lowest measured pollutant concentrations. The ratios in total N/total P and in inorganic N/organic N in runoff waters indicated that fertilization in spring greatly contributed to the temporal increase of N loadings, especially in forms of inorganic N. Isotope signature of (15)N-nitrate in the water samples verified that the nitrate was derived from fertilizers and was consumed during transportation. Both N and P concentrations in the receiving water bodies were above the eutrophic level. During the study period, herbicide concentrations in the receiving water bodies rarely exceeded the drinking water standards.     

Evaluating the Impacts of Mangrove Rehabilitation in Cogtong Bay,Philippines

Marine Protected Areas (MPAs) have been hailed worldwide as vehicles toward sustainable development (SD) in coastal zones. The prominent model by which MPAs operate is through a comanagement approach, a shift from traditional top-down management. This paradigm shift must be reviewed continuously to evaluate its social and ecological impacts, thereby allowing adaptive management. We evaluated the perceived impacts of the Cogtong Bay Mangrove Rehabilitation Project (CBMRP; Philippines) by using 12 perception indicators categorized into 3 comanagement impact criteria (equity, efficiency, and sustainability). We also collected 16 contextual attributes of each respondent to determine the correlates of perceived impacts. Our results showed that there were significant improvements in all indicators under the efficiency criterion but mixed impacts in the equity and sustainability criteria. Access to resource and household income (equity) and fisheries abundance (sustainability) were perceived to have decreased during the last 15 years and were not expected to improve in the future. Stepwise multiple regression analysis showed that the asymmetries of the perceived impacts of the CBMRP were principally caused by disparities in perceptions by gender and by location (Candijay and Mabini). This highlighted the importance of cross-scale institutional linkages between Cogtong Bay municipalities to systematically address baywide management issues. Our results further demonstrated the necessity of integrating gender issues into the evaluation of MPA impacts to ensure a robust evaluation. Finally, we recommend that a rigorous evaluation of MPAs using a common set of impact indicators should be encouraged to allow comparison of studies both spatially and temporally.     

Stress,work and professional satisfaction and militancy among Canadian physicians

The introduction of a national health care system in Canada has resulted in regular and increasing conflict between the medical profession, government and other political actors. The present study utilizes a stressor–strain framework to understand physician militancy in Canada. Data were collected from 2087 men and women physicians using questionnaires completed anonymously. Four groups of predictor variables identified in previous research were considered: individual demographic characteristics, practice characteristics, work stressors, and work and professional satisfactions. Empirical support for the model was found. Each panel of predictor variables had significant and unique relationships with measures of physician militancy.     

Managing the Commons Texas Style: Wildlife Management and Ground‐Water Associations on Private Lands1

Abstract: As nearly all of Texas’ rural lands are privately owned, landowner associations for the management of white‐tailed deer and ground‐water have become increasingly popular. Deer are a common‐pool resource with transboundary characteristics, requiring landowner cooperation for effective management. Ground‐water reserves are economically important to landowners, but are governed by the “rule of capture” whereby property rights are not defined. One ground‐water association and four wildlife management associations (WMAs) were surveyed to characterize their member demographics, land use priorities, attitudes, and social capital. Members of the ground‐water cooperative were part of a much larger, more heterogeneous, and more recently formed group than members of WMAs. They also placed greater importance on utilitarian aspects of their properties, as opposed to land stewardship for conservation as practiced by members of WMAs. If ground‐water association members could be more locally organized with more frequent meetings, social capital and information sharing may be enhanced and lead to land stewardship practices for improved hydrologic functions and sustained ground‐water supply. This, coupled with pumping rules assigned by the local ground‐water district, could yield an effective strategy that is ecologically and hydrologicaly sound, and that allows rural provision of water supply to urban consumers.     

Evaluation of Three Watershed‐Scale Pesticide Environmental Transport and Fate Models1

Abstract: The U.S. Environmental Protection Agency (USEPA) Office of Pesticide Programs (OPP) has completed an evaluation of three watershed‐scale simulation models for potential use in Food Quality Protection Act pesticide drinking water exposure assessments. The evaluation may also guide OPP in identifying computer simulation tools that can be used in performing aquatic ecological exposure assessments. Models selected for evaluation were the Soil Water Assessment Tool (SWAT), the Nonpoint Source Model (NPSM), a modified version of the Hydrologic Simulation Program‐Fortran (HSPF), and the Pesticide Root Zone Model‐Riverine Water Quality (PRZM‐RIVWQ) model. Simulated concentrations of the pesticides atrazine, metolachlor, and trifluralin in surface water were compared with field data monitored in the Sugar Creek watershed of Indiana’s White River basin by the National Water Quality Assessment (NAWQA) program. The evaluation not only provided USEPA with experience in using watershed models for estimating pesticide concentration in flowing water but also led to the development of improved statistical techniques for assessing model accuracy. Further, it demonstrated the difficulty of representing spatially and temporally variable soil, weather, and pesticide applications with relatively infrequent, spatially fixed, point estimates. It also demonstrated the value of using monitoring and modeling as mutually supporting tools and pointed to the need to design monitoring programs that support modeling.     

Competition,disturbance and local diversity patterns of substratum-bound clonal organisms: A simulation

We have conducted a series of simulations in order to compare the relative diversification effects of disturbance and intransitive (i.e., A > B, B > C but C > A) competition on a hypothetical set of clonal organisms. We found large significant differences between these two effects only when disturbance levels were low or absent. We suggest that natural assemblages should be examined for the frequency of intransitive interactions along disturbance gradients in order to assess the significance of these competitive relationships. We also argue that intransitive competition ought to be incorporated into nonequilibrium disturbance models; diversification effects of disturbance and intransitive competition need not be mutually exclusive.     

A study of diesel emissions on Drosophila

A sex-linked recessive lethal test was performed on male fruit flies of the species Drosophila melanogaster, (Oregon-R strain), exposed to an approximate five-fold dilution of exhaust from a diesel engine. The eight hour exposure was achieved by drawing diluted diesel exhaust from a three cubic meter stainless steel exposure chamber housing laboratory animals through a two liter reaction flask modified for use with Drosophila. A preconditioned sampling bag was used to collect the emissions after passing through the exposure chamber containing the flies. Results of analyses performed on the diesel exhaust mixture showed the following: carbon dioxide—0.17%, carbon monoxide—12.2 ppm, hydrocarbons—11.6 ppm, nitrogen oxide—3.8 ppm, nitrogen dioxide—2.9 ppm, sulphur dioxide—1.0 ppm, and particulates—2.18 mg/m³. Two broods of the F₂ generation were investigated for the occurrence of recessive lethal events. These broods approximated the developing gametogenic stages of mature sperm (P₁ matings on days 2 and 3 postexposure) and spermatocytes (P₁ matings on days 8 and 9). Additionally, the F₃ generation was evaluated for the occurrence of mosaic recessive lethal events which might escape detection in the F₂ generation. An equal number of F₂ and F₃ flies for both broods served as concurrent controls. Results indicate that, under the conditions tested, the diesel exhaust did not increase the mutation frequency of the exposed flies (F₂ rate = 0.30%, F₃ rate = 0%) when compared to the concurrent controls (F₂ rate = 0.37%, F₃ rate = 0.15%).     

THE ADOPTION OF MUNICIPAL WATER CONSERVATION: AN UNLIKELY EVENT?1

ABSTRACT: It is contended that water conservation measures that reduce a water system's net revenues are unlikely to be adopted. Pricing policies that induce conservation can be designed to increase net revenues. Management practices that lead to conservation and pure conservation measures may reduce net revenues; consequently, they are unlikely to be adopted. Recent experience in five southwestern cities supports these contentions. It is argued that the managers of a municipal water enterprise are particularly sensitive to short term variation in revenues. Consequently, to increase the likelihood of the adoption of measures that reduce net revenues it is necessary to remove either the decision to adopt measures that reduce net revenue or the adverse revenue effect from the water enterprise. Finally, to make higher rates for conservation palatable, imaginative use for the funds generated must be developed.     

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.