Biological Pollutants: Alien Fishes in Mountain Lakes

Many lakes in the national parks of the Canadian Rockies were stocked with alien fish species in the early to mid 20th century. Changes to Parks Canada's mandate require the original communities of these lakes to be restored. We document the changes to invertebrate communities caused by the stocking of alien fishes into three fishless alpine lakes, and describe the results of two restoration experiments, one the reintroduction of Hesperodiaptomus arcticus, a planktonic predator that had been eliminated from Snowflake Lake by stocked fish, and the other the removal of brook trout (Salvelinus fontinalis) from Bighorn Lake. In both cases, there were great changes to the zooplankton communities, which required several years to complete, probably because of the cold water and unproductive nature of the lakes. Many of the invertebrate species extirpated by stocked alien fishes co-exist with native fish species in nearby lakes. Possible reasons are discussed.     

Trends in the Water Chemistry of High Altitude Lakes in Europe

Here we present the chemical trends of seven high altitude lakes, analysed within the AL:PE and MOLAR Projects of the EU (1999) and selected on the basis of the availability of complete and reliable data for the period 1984–1999. The lakes are representative of the Scandinavian Alps, the Cairngorm Mountains in Scotland, the Alps and the Pyrenees. Significant trends were identified for some indicators of acidification, for instance pH and alkalinity, but not all lakes reacted similarly to decreasing depositions of sulphate and base cations. Differences in lake response are discussed in relation to recent variations of atmospheric deposition chemistry and associated changes in climatic conditions. Beside individual variations of the studied lakes, depending, among other things, on altitude and morphology, catchment characteristics and climate trends play a major role for the reaction of high altitude lakes on changes in atmospheric depositions.     

SUBJECTIVE RESPONSES TO COMPUTER SIMULATIONS OF URBAN ENVIRONMENTS

Simulations of urban or natural environments created by graphics computer software are increasingly being utilized in research and applied contexts, and pertinent techniques have become highly sophisticated. However, the quality and utility of such presentation means still need careful validation. This issue was addressed in a series of lab and field studies. In the study reported here, a simulation of a suburban environment was presented to respondents (n=147) in several variations to investigate the effects of lighting (day/sun, day/fog, night), personal shadow (yes/no) and sound (on/off) on perceived simulation quality. The contingencies with related aspects (such as comprehension, recollection and appreciation of the simulated environment) were investigated as well. Based on a comprehensive conceptual framework, a set of scales measuring relevant cognitive and affective aspects was employed. Main results are that simulations were perceived as valid and acceptable, that appraisals differ according to lighting and time-of-day conditions, and that provision of sound enhances the perceived quality of presentations. The findings elucidate which factors are crucial for further improving simulations and clarify the validity of computer simulations for assessing existing and future environments.     

PERCEIVED QUALITY OF CARE: THE INFLUENCE OF THE WAITING ROOM ENVIRONMENT

The current study investigated the effect of the physical environment of the waiting room on perceptions of the quality of care of the physician. One hundred forty-seven college students and 58 senior citizens viewed 35 slides of physicians' waiting rooms. Using a visual analog scale, participants rated the perceived quality of care and the environment of each waiting room. The primary hypothesis was that perceived quality of care would be greater for waiting rooms that were nicely furnished, well-lighted, contained artwork, and were warm in appearance versus waiting rooms that had outdated furnishings, were dark, contained no artwork or poor quality reproductions, and were cold in appearance. Factor analyses of the care and environment ratings produced factors consistent with the hypothesis. Additionally, waiting rooms judged to be those of female physicians were rated higher on both perceived quality of care and comfort in the environment.     

WATER QUALITY MODELING OF ALTERNATIVE AGRICULTURAL SCENARIOS IN THE U.S. CORN BELT1

ABSTRACT: Simulated water quality resulting from three alternative future land‐use scenarios for two agricultural watersheds in central Iowa was compared to water quality under current and historic land use/land cover to explore both the potential water quality impact of perpetuating current trends and potential benefits of major changes in agricultural practices in the U.S. Corn Belt. The Soil Water Assessment Tool (SWAT) was applied to evaluate the effect of management practices on surface water discharge and annual loads of sediment and nitrate in these watersheds. The agricultural practices comprising Scenario 1, which assumes perpetuation of current trends (conversion to conservation tillage, increase in farm size and land in production, use of currently‐employed Best Management Practices (BMPs)) result in simulated increased export of nitrate and decreased export of sediment relative to the present. However, simulations indicate that the substantial changes in agricultural practices envisioned in Scenarios 2 and 3 (conversion to conservation tillage, strip intercropping, rotational grazing, conservation set‐asides and greatly extended use of best management practices (BMPs) such as riparian buffers, engineered wetlands, grassed waterways, filter strips and field borders) could potentially reduce current loadings of sediment by 37 to 67 percent and nutrients by 54 to 75 percent. Results from the study indicate that major improvements in water quality in these agricultural watersheds could be achieved if such environmentally‐targeted agricultural practices were employed. Traditional approaches to water quality improvement through application of traditional BMPs will result in little or no change in nutrient export and minor decreases in sediment export from Corn Belt watersheds.     

ACCURACY AND RELIABILITY OF NUMERICAL RIVER MODELS1

ABSTRACT: Over the last 20 years, our possibilities to model river flows numerically have increased enormously. In this paper, the question is addressed whether a more sophisticated model is always better than a simpler one. Increased detail, both in finer resolution and in physical processes taken into account, has its price in more computer time, higher data need, and perhaps more unknown coefficients to be calibrated. Moreover, uncertainty in actual physical conditions (e.g., bottom roughness), inflow and parameters remains, which may dominate the uncertainty of the results. Also, the questions asked by a decision maker may not always be very precise. For a schematic but relevant example, we show that a better model does not necessarily give more reliable results because some of the basic uncertainties remain. It is concluded that we should use the simplest model that will answer the question as to the accuracy needed, taking into account uncertainties in the data     

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.     

Defining contamination limits with pneumatic hammer soil probes

There have been more than 100,000 confirmed releases of petroleum from underground storage tanks (USTs) in the United States and its territories. The 10,000-gallon spill and cleanup of unleaded gasoline, detailed in this article, that occurred from 1988 to 1990 on Cape Cod, Massachusetts, illustrates the author's argument that electric pneumatic-hammer soil probes are the fastest, most convenient, and least costly way of performing the soil-gas surveys needed to locate spilled petroleum product, evaluate vapor intrusion into basements, and determine the extent of groundwater contamination for remediation purposes. Current state soil-gas requirements are also included.     

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.