Whole-Lake and Nearshore Water Chemistry In Bowland Lake Before and After Treatment with CaCO3

Publisher Website
Google Scholar
Abstract
After neutralization of Bowland Lake, a clear oligotrophic acidified lake, with CaCO3 in August 1983, the whole-lake pH and alkalinity increased from 4.9 and -6 .mu.eq.cntdot.L-1 to 6.7 and 89 .mu.eq.cntdot.L-1, respectively. Total whole-lake Al decreased gradually from 130 to 30 .mu.g.cntdot.L-1, Mn decreased from 80 to 28 .mu.g.cntdot.L-1 and the lake became less transparent as dissolved organic carbon (DOC) increased and Secchi depth decreased. Metals other than Al and Mn remained low and did not respond to neutralization. Between August 1983 and March 1986, about 40% of the added alkalinity of Bowland Lake was lost. Decreases of whole-lake pH following snowmelt occurred prior to but not after neutralization. Neutralization of lake water did not prevent acidic melt water from forming a distinctive acidic zone < 1 m thick beneath the ice. The melt layer was more acidic than lake water, it was colder and therefore less dense, it usually contained higher Al, and it was dilute with lower conductivity and Ca. Intra-site variation was probably due to variable volumes of melt water received. A snowmelt model based on daily air temperature and precipitation predicted intermittent recharge of groundwater reservoirs during snowmelt. However, runoff was continually observed nearshore under ice suggesting that groundwater reservoirs continued to discharge after recharge ended or that the residence time of melt waters in the littoral zone was relatively long.