Preface

Water, Air, &; Soil Pollution: Focus -     

Ecological Integrity: Concept,Assessment, Evaluation: The Traunsee Case

Definitions and concepts relevant to the evaluation of theEcological Integrity of lakes are discussed herein. Theirapplication to Traunsee, a deep lake located in the AustrianAlps which is affected by wastes of salt- and soda-producingindustries, is evaluated, based on 13 contributions published inthis special issue of Water, Air, and Soil Pollution.: Focus.     

REGIONAL SEWERING AND GROUNDWATER QUALITY IN THE SOUTHERN SAN JOAQUIN VALLEY1

ABSTRACT: Sewage effluent is commonly disposed of on land in arid regions, and the majority usually recharges the groundwater. Few evaluations have been made of the effect of effluent disposal on groundwater quality in the west. Groundwater hydrologists are rarely involved with treatment plant design and operation or effluent disposal in the San Joaquin Valley, California. The author's purpose is to evaluate the effect of regional sewering programs on groundwater quality in this valley. Research was conducted on past studies of sewage effluent disposal. An extensive water sampling program was undertaken near the Fresno Sewage Treatment Plant. Chloride contents were used to trace recharged effluent. The extent of recharged effluent was delineated and traced for about ten miles. Sampling between the plant and the urban Fresno area indicated a high probability of large-scale leakage of raw sewage into the groundwater.     

NUMERICAL MODELING OF THERMAL STRATIFICATION IN A RESERVOIR WITH LARGE DISCHARGE-TO-VOLUME RATIO1

ABSTRACT: A numerical model study of thermal stratification in a high discharge-to-volume reservoir is described. Predicted temperature profiles are compared with field data for two different years. The model accurately predicts the date of fall turnover, and predicts degree of stratification and depth of the thermocline within about 20% for both years simulated. A parametric study of stratification mechanics for a high flow reservoir indicated that diffusion was the predominant heat transport mechanism in the hypolimnion, while surface effects dominated the epilimnion. Flow effects for the particular case studied, in which all inflows and outflows occur in the epilimnion, did not significantly affect stratification behavior.     

Benthic Algal (Periphyton) Growth Rates in Response to Nitrogen and Phosphorus: Parameter Estimation for Water Quality Models

Nitrogen (N) and phosphorus (P) are significant pollutants that can stimulate nuisance blooms of algae. Water quality models (e.g., Water Quality Simulation Program, CE‐QUAL‐R1, CE‐QUAL‐ICM, QUAL2k) are valuable and widely used management tools for algal accrual due to excess nutrients in the presence of other limiting factors. These models utilize the Monod and Droop equations to associate algal growth rate with dissolved nutrient concentration and intracellular nutrient content. Having accurate parameter values is essential to model performance; however, published values for model parameterization are limited, particularly for benthic (periphyton) algae. We conducted a 10‐day mesocosm experiment and measured diatom‐dominated periphyton biomass accrual through time as chlorophyll a (chl a) and ash‐free dry mass (AFDM) in response to additions of N (range 5–11,995 µg nitrate as nitrogen [NO₃‐N]/L) and P (range 0.89–59.51 µg soluble reactive phosphorus/L). Resulting half‐saturation coefficients and growth rates are similar to other published values, but minimum nutrient quotas are higher than those previously reported. Saturation concentration for N ranged from 150 to 2,450 µg NO₃‐N/L based on chl a and from 8.5 to 60 µg NO₃‐N/L when based on AFDM. Similarly, the saturation concentration for P ranged from 12 to 29 µg‐P/L based on chl a, and from 2.5 to 6.1 µg‐P/L based on AFDM. These saturation concentrations provide an upper limit for streams where diatom growth can be expected to respond to nutrient levels and a benchmark for reducing nutrient concentrations to a point where benthic algal growth will be limited.     

Influence of delayed metamorphosis on survival and growth of juvenile barnacles Balanus amphitrite

Competent cyprid larvae of the barnacle Balanus amphitrite Darwin were prevented from metamorphosing in the laboratory for 3 or 5 d using three different techniques (holding at low temperature, crowding, and detaining on a silanized surface). We then assessed the effects of prolonging larval life on post-metamorphic growth and survival, in comparison with control individuals that metamorphosed soon after they were competent to do so. Seven experiments were conducted over 2 yr (July 1987 to September 1989). In all experiments (each with six replicates per treatment), postponing larval metamorphosis for 3 or 5 d dramatically depressed postmetamorphic growth rate (P<0.05), although metamorphic success and post-metamorphic survival were not affected (P>0.10). The results suggest that B. amphitrite cyprids deferring their metamorphosis in the field may be less successful in competing for space, at least during the first few weeks of postlarval life.