Caloric Changes Along Pulp and Paper Mill Effluent Plumes

Abstract

Eight pulp and paper effluent plumes in Nipigon Bay were tracked with Rhodamine dye to determine dilution and nondilution losses of calories with distance and time. Dilution, as determined by Na+ decrease, accounted for 98.5% of the decrease in caloric concentration along centerline trajectories of plumes over 2000 m in 7.5 h; mean caloric concentration decreased from 1583 cal∙ℓ−1 in effluent to 50 cal∙ℓ−1 at background stations. Nondilution caloric changes were estimated by two methods, first by examination of the main processes (respiration, settling of particles, and primary production) and, secondly, by interpretation of time series of direct measurements of caloric concentrations. By the first method, measurement of respiration indicated loss of 2.1 cal∙ℓ−1, while particle loss from plumes was 25.5 cal∙ℓ−1 and accrual of calories by primary production was 0.5 cal∙ℓ−1. Integration of these results yielded an estimate of 27.1 cal∙ℓ−1 net nondilution loss in caloric concentration along centerline trajectories over the average distance of 2000 m. By the second method, direct measurement of decrease in caloric concentration gave an estimate of nondilution loss of 45 cal∙ℓ−1 over 2000 m. Approximately 17% of effluent calories were used in biodegradation and lost in sedimentation from the plume within 2000 m of the source. Environmental degradation, in terms of dissolved oxygen conditions and deposition of particles, apparently was only locally significant.