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

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 μeq∙L−1 to 6.7 and 89 μeq∙L−1, respectively. Total whole-lake Al decreased gradually from 130 to 30 μg∙L−1, Mn decreased from 80 to 28 μg∙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.

Changes in the Zoobenthos Community of Acidified Bowland Lake after Whole-Lake Neutralization and Lake Trout (Salvelinus namaycush) Reintroduction

“…Profundal zoobenthos biomasses (860-1 300 mg am -2, were higher than merage values reported by Demott et al (1986) for groups of central Ontario Bakes ranging in pH from 4.6-7.7 (99-808 mg.m12); however, a larger and thus presumably less efficient, screen size (500 pm) was used for that study. The slightly reduced zoobenthos abundance in the year following neutralization (1984) in c o m p~s o n to preneutralizatiora (1982) abundance may indicate a short-term negative influence by water quality changes or metal precipitation induced by neutralization (Molot et al 1990). Previous studies have documented reduced zoobenthos abundance after lake neutralization (Scheider et al 1975;Raddum et al 1984).…”

Long‐term trends in catchment export and lake retention of dissolved organic carbon, dissolved organic nitrogen, total iron, and total phosphorus: The Dorset, Ontario, study, 1978–1998

“…Since catchments, and in particular wetlands, are major sources of DOC in unproductive lakes on the Precambrian Shield [ Dillon and Molot , 1997a], fluctuations in lake DOC concentrations can be driven in large part by regional scale factors that affect export, for example, runoff [ Schindler et al , 1997; Dillon and Molot , 1997b; Schiff et al , 1998; Pastor et al , 2003]. Acidification can also affect lake DOC concentrations [ Molot et al , 1990].…”

Does Acid Rain Increase Human Exposure to Mercury? A Review and Analysis of Recent Literature

“…Decreases in DOC content and/or colour of lakes have been linked to both sulphate deposition and lake acidification [6,22,24]. Likewise, the neutralization of acidified lakes by liming has resulted in significant increases in DOC [25,26], suggesting that a direct relationship exists between lake acidification and DOC concentration. The impact of acid deposition on DOC has been attributed to the binding and precipitation of DOC with aluminum [27], which is expected to be higher in concentration under acidified conditions [4,6,24].…”