Effects of air injection at Prompton Lake, Wayne County, Pennsylvania

Air injected into the hypolimnion of Prompton Lake at a maximum rate of 210 cubic feet per minute (6 cubic metres per minute) during a 65-day period (July 27 to September 30, 1973) produced the following results: (1) With cooler air temperatures prevailing, the mean subsurface temperature increased by 4.0° C compared with the same period in 1972, (2) although chemical and thermal destratiflcation was incomplete, 6 weeks of air injection increased the dissolved-oxygen concentration of the entire tropholytic zone to more than 4 milligrams per litre, (3) concentrations of nitrogen increased in the trophogenic zone during air injection, and (4) Anabaena flos-aquae attained cell concentrations in excess of 4,500 per millilitre during air injection.