Investigation of the ozonolysis of ethylenebisdithiocarbamate-fungicides in model solutions

A study of the effectiveness of ozonation for the removal of nabam (disodium ethylenebisdithiocarbamate) from aqueous solutions was carried out. Nabam is the parent compound of a commonly used group of fungicides. The process of nabam degradation was followed in terms of several parameters such as nabam concentration, chemical oxygen demand (COD), sulphate ion concentration as a measure of the relative degree of mineralization of nabam, and the pH value of the solution. Ozonation accelerates the decomposition of nabam with the formation of sulphates and nitrates as final products. The intermediate decomposition products of nabam are more resistant to degradation by ozone than the parent compound. The amounts of ozone which are used in wastewater treatment plants for disinfection may be sufficient to remove both nabam and its decomposition products, at a low level of contamination, but if the concentration of nabam is too high the intermediate decomposition products can still be present. Lowering the pH of the medium favours the oxidation of nabam.     

Recovery of temperate-stream fish communities from disturbance: A review of case studies and synthesis of theory

To evaluate the relative effect of autecologic factors, site-specific factors, disturbance characteristics, and community structure on the recovery of temperate-stream fish communities, we reviewed case histories for 49 sites and recorded data on 411 recovery end points. Most data were derived from studies of low-gradient third- or fourth-order temperate streams located in forested or agricultural watersheds. Species composition, species richness, and total density all recovered within one year for over 70% of systems studied. Lotic fish communities were not resilient to press disturbances (e.g., mining, logging, channelization) in the absence of mitigation efforts (recovery time >5 to >52 yr) and in these cases recovery was limited by habitat quality. Following pulse disturbances, autecological factors, site-specific factors, and disturbance-specific factors all affected rates of recovery. Centrarchids and minnows were most resilient to disturbance, while salmonid populations were least resilient of all families considered. Species within rock-substrate/nest-spawning guilds required significantly longer time periods to either recolonize or reestablish predisturbance population densities than did species within other reproductive guilds. Recovery was enhanced by the presence of refugia but was delayed by barriers to migration, especially when source populations for recolonization were relatively distant. Median population recovery times for systems in which disturbances occurred during or immediately prior to spawning were significantly less than median recovery times for systems in which disturbances occurred immediately after spawning. There was little evidence for the influence of biotic interactions on recovery rates.     

Mine-drainage treatment wetland as habitat for herptofaunal wildlife

Land reclamation techniques that incorporate habitat features for herptofaunal wildlife have received little attention. We assessed the suitability of a wetland, constructed for the treatment of mine-water drainage, for supporting herptofaunal wildlife from 1988 through 1990 using diurnal and nocturnal surveys. Natural wetlands within the surrounding watershed were also monitored for comparison. The treatment wetland supported the greatest abundance and species richness of herptofauna among the sites surveyed. Abundance was a function of the frog density, particularly green frogs (Rana clamitans) and pickerel frogs (R. palustris), while species richness was due to the number of snake species found. The rich mix of snake species present at the treatment wetland was believed due to a combination of an abundant frog prey base and an amply supply of den sites in rock debris left behind from earlier surface-mining activities. Nocturnal surveys of breeding male frogs demonstrated highest breeding activity at the treatment wetland, particularly for spring peepers (Hyla crucifer). Whole-body assays of green frog and bullfrog (R. catesbeiana) tissues showed no differences among sites in uptake of iron, aluminum, and zinc; managanese levels in samples from the treatment wetland were significantly lower than those from natural wetlands. These results suggest that wetlands established for water quality improvement can provide habitat for reptiles and amphibians, with the species composition dependent on the construction design, the proximity to source populations, and the degree of acidity and heavy-metal concentrations in drainage waters.     

Driver response to a disabled pedestrian using a dangerous crosswalk

A field experiment investigated factors expected to influence yielding by motorists to a pedestrian waiting to cross a city street. Subjects consisted of 604 motorists who passed through two marked crosswalks. Motorists were significantly more likely to stop for a disabled pedestrian using a cane than a non-disabled pedestrian without a cane. This study also evaluated the impact of a ‘fatality sign’ erected before one of the crossings. While the fatality sign by itself had no significant effect on motorists yielding, there was a strong interactive effect of the sign and the disability manipulation. Thus, the greatest levels of motorists yielding occurred for subjects who were exposed to the fatality sign and the disabled pedestrian. In contrast, the lowest levels of yielding occurred at the fatality-marked crossing for a non-disabled pedestrian.     

MULTIOBJECTWE OPTIMIZATION OF RESERVOIR SYSTEMS OPERATION1

ABSTRACT: Development of optimal operational policies for large-scale reservoir systems is often complicated by a multiplicity of conflicting project uses and purposes. A wide range of multiobjective optimization methods are available for appraising tradeoffs between conificting objectives. The purpose of this study is to provide guidance as to those methods which are best suited to dealing with the challenging large-scale, nonlinear, dynamic, and stochastic characteristics of multireservoir system operations. As a case study, the selected methodologies are applied to the Han River Reservoir System in Korea for four principal project objectives: water supply and low flow augmentation; annual hydropower production, reliable energy generation, and minimization of risk of violating firm water supply requirements. Additional objectives such as flood control are also considered, but are imposed as fixed constraints.     

ESTIMATING MARYLAND CRITICAL AREA ACVS IMPACT ON FUTURE NONPOINT POLLUTION ALONG THE RHODE RWER ESTUARY1

ABSTRACT: This paper presents the results of an investigation of the effects of the Maryland Critical Area Act on generation of non-point source loads of phosphorus, nitrogen, and sediment to the Rhode River estuary. The Simple Method model, the Marcus and Kearney regression model, and the CREAMS model were used to estimate annual loads under: (1) present conditions, (2) maximum land use development allowable under the Act, and (3) two sets of future land use conditions that might occur if the Act were not in place. Results indicate that the Critical Area Act can reduce the present generation of nonpoint nutrient and sediment loadings 20–30 percent from the regulated area. These reductions can occur while preserving agricultural lands and allowing limited residential and urban development. The decrease in nutrient loadings is primarily dependent upon implementation and enforcement of agricultural best management practices (BMPs). The BMPs could reduce present agricultural nutrient loadings by 90 percent to a level comparable to loadings from residential areas. The estimated effectiveness of the Critical Area Act is even greater when compared to potential future nutrient loadings if development in the area remains unregulated. Unrestricted residential and urban development could increase nutrient loadings by 200 percent to 1000 percent as compared to controlled development under Critical Area Act guidelines. The Critical Area Act primarily prevents these future increases by severely limiting woodland cutting, with lesser results obtained by requiring urban BMPs.     

SPATIAL DISTRIBUTION OF POINT SOIL MOISTURE ESTIMATES USING LANDSAT TM DATA AND FUZZY-C CLASSIFICATION1

ABSTRACT: Many hydrologic models have input data requirements that are difficult to satisfy for all but a few well-instrumented, experimental watersheds. In this study, point soil moisture in a mountain watershed with various types of vegetative cover was modeled using a generalized regression model. Information on sur-ficial characteristics of the watershed was obtained by applying fuzzy set theory to a database consisting of only satellite and a digital elevation model (DEM). The fuzzy-c algorithm separated the watershed into distinguishable classes and provided regression coefficients for each ground pixel. The regression model used the coefficients to estimate distributed soil moisture over the entire watershed. A soil moisture accounting model was used to resolve temporal differences between measurements at prototypical measurement sites and validation sites. The results were reasonably accurate for all classes in the watershed. The spatial distribution of soil moisture estimates corresponded accurately with soil moisture measurements at validation sites on the watershed. It was concluded that use of the regression model to distribute soil moisture from a specified number of points can be combined with satellite and DEM information to provide a reasonable estimation of the spatial distribution of soil moisture for a watershed.     

The role of facet importance as a moderator in job satisfaction processes

Two studies were designed to test hypotheses derived from Locke's (1969, 1976, 1984) model of job satisfaction. Consistent with the model, both studies found that perceived have-want discrepancy scores were powerful predictors of facet job satisfaction. In addition, facet importance tended to moderate this relationship in the manner predicted by Locke. Workers who viewed a job facet as having high importance were more satisfied with a small perceived have-want discrepancy and more dissatisfied with a large discrepancy than workers who viewed the facet as having low importance. Finally, as expected, facet importance failed to moderate the relationship between facet satisfaction and overall job satisfaction. This finding supports Locke's proposition that facet satisfaction scores are ‘implicitly weighted’ by facet importance. Implications and directions for future research are discussed.     

NETWORK AND SUBWATERSHED PARAMETERS EXTRACTED FROM DIGITAL ELEVATION MODELS: THE BILLS CREEK EXPERIENCE1

ABSTRACT: An automated extraction of channel network and sub-watershed characteristics from digital elevation models (DEM) is performed by model DEDNM. This model can process DEM data of limited vertical resolution representing low relief terrain. Such representations often include ill-defined drainage boundaries and indeterminate flow paths. The application watershed is an 84 km² low relief watershed in southwestern Oklahoma. The standard for validation is the network and subwatershed parameters defined by the blue line method on USGS 7.5–minute topographic maps. Evaluation of the generated and validation networks by visual comparisons shows a high degree of correlation. Comparison of selected network parameters (channel length, slope, drainage density, etc.) and of drainage network composition (bifurcation, length, slope, and area ratios) shows that, on the average, the generated parameters are within 5 percent of those derived from the validation network. The largest discrepancies were found for the channel slope values. The results of this application demonstrate that DEDNM effectively addresses network definition problems often encountered in low relief terrain and that it can generate accurate network and subwatershed parameters under those conditions.