Browsing by Author "Connolly, John P."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item An Age Dependent Model Of PCB In A Lake Michigan Food Chain(1981-09-30) Thomann, Robert V.; Connolly, John P.An age-dependent food chain model that considers species bioenergetics and toxicant exposure through water and food is developed. It is successfully applied to PCB contamination of the Lake Michigan lake trout food chain represented by phytoplankton, Mysis, alewife, and lake trout. The model indicates that for the top predator lake trout, PCB exposure through the food chain can account for greater than 99 percent of the observed body burden. A simple steady-state computation indicates that ratios of chemical concentration in predators to that in prey in feeding experiments may be as low as 0.2 and still result in significant food chain transfer. It is estimated that a criterion specifying that PCB concentrations of all ages of lake trout be at or below 5 ug/g (wet weight) in the edible portion would require that dissolved PCB concentrations be reduced to somewhere between 0.5 and 2.5 ug/R. The range reflects uncertainty in the PCB assimilation efficiency of the species and the dissolved PCB concentration. This report was submitted in fulfillment of Cooperative Agreement No. CR805916010 by Manhattan College under the sponsorship of the U.S. Environmental Protection Agency. This report covers the project period May 1, 1978 to September 30, 1981.Item Mathematical Models Of Water Quality In Large Lakes Part 2: Lake Erie(1980-07) Di Toro, Dominic M.; Connolly, John P.This research was undertaken to develop and apply a mathematical model of the water quality in large lakes, particularly Lake Huron and Saginaw Bay (Part 1) and Lake Erie (Part 2). A mathematical model was developed for analysis of the interactions between nutrient discharges to Lake Erie, the response of phytoplankton to these discharges, and the dissolved oxygen depletion that occurs as a consequence. Dissolved oxygen, phytoplankton chlorophyll for diatoms and nondiatoms, zooplankton biomass, nutrient concentrations in available and unavailable forms and inorganic carbon are considered in the model. Extensive water quality data for Lake Erie was analyzed and statistically reduced. Comparison of data from 1970 and 1973-74 to model calculations served for calibration of the model. A verification computation was also performed for 1975, a year when no anoxia was observed. Recent developments in phytoplankton growth and uptake kinetics are included in this analysis. The methods of sedimentary geochemistry are expanded to include an analysis of sediment oxygen demand within the framework of mass balances. Projected effects of varying degrees of phosphorus removal on dissolved oxygen, anoxic area, chlorophyll, transparency and phosphorus concentration are presented. This report was submitted in fulfillment of Grant No. R803030 by Manhattan College under the sponsorship of the U.S. Environmental Protection Agency. This report covers the project period March 26, 1974 to March 25,1977.Item A Model of Kepone in the Striped Bass Food Chain of the James River Estuary(1985) Connolly, John P.; Tonelli, RosellaA mathematical model that computes the accumulation of Kepone in the stripped bass food chain of the James River estuary was developed. The purpose of the model was to help understand the relationship of Kepone levels in important fish species to sediment and water column Kepone concentrations and then to address the question of why these levels still exceed Food and Drug Administration limits 8 years after discharge stopped. The model considers exposure through diet and respiration at rates based on species bioenergetics. It was successfully calibrated to observed 1976 through 1982 striped bass, white perch, and Atlantic croaker Kepone concentrations. The model indicates that for the upper levels of the food chain, diet is the major route of contamination, accounting for 87-88% of the observed concentration in croaker and white perch and 91% of the observed concentration in striped bass. The two Kepone sources; sediment and water column, contribute approximately equally to the croaker and white perch. The water column is more significant for striped bass, being the original source for approximately 60% of the observed body burdens. It was estimated that a criterion requiring Kepone concentrations in fish to be at or below 0.3 ng/g would require dissolved water column and sediment Kepone concentrations to be reduced to somewhere between 3 and 9 ng/l and 13-39 ng/g, respectively, depending on the species. Striped bass require the greatest reductions in dissolved water column and sediment Kepone concentration to somewhere between 3 and 5 ng/l and 13 and 24 ng/g respectively.