A geochemical analysis of lake waters and soils associated with three granites of variable fluoride concentration in Maine and New Hampshire, USA

Kittredge, Leah

FIELD WORK: 'A comparative study of the lakes associated with the Cadillac and Lucerne Granites, Maine, and Conway Granite, New Hampshire, focuses on bedrock composition controls on lake chemistry, while also considering factors that influence lake chemistry such as soil chemistry, element mobility, complexation, and precipitation chemistry. The Conway Granite in New Hampshire is F-rich containing up to 1 % F (Creasy, 1974). The Lucerne Granite in Maine also contains F-rich accessory minerals, but has a lower F concentration (0.1%) (Norton and Vesely, unpublished). The Cadillac Granite in Maine contains small amounts of F-bearing minerals and is F-poor (Chapman, 1970).' 'The bedrock F concentration is reflected in the chemistries of the Conway, Lucerne, and Cadillac lakes, but the soils exhibit different behavior. The Fitts Pond (Lucerne) soils have higher Fh20 and FCaCl2 concentrations than the Upper Greeley (Conway) soils, even though the Conway Granite contains more F than the Lucerne Granite. The Upper Greeley soils however, are considerably coarser than the Fitts soils. The Fitts B-horizon also has nearly two times the organic concentration as the Upper Greeley B-horizon, this coupled with the larger fraction of fine grained material in the Fitts soils promotes greater retention of F in the Fitts soils. The relationship between soil texture and FH2o and FCaCl2 concentrations suggests that little F is held in the Upper Greeley soils, and the majority of F passes directly from soils to lake water upon weathering.' 'In Bubble and Fitts Ponds on the Cadillac Granite and Lucerne Granite, respectively, the lake water- Al species were predominantly hydroxyl complexes. In Upper Greeley Pond, on the Conway Granite, the Al species were dominated by Al-F complexes. MINEQL plus simulations showed direct correlation between total F concentration and dissolved Al. In all three regions the majority of the lakes sampled were at circum-neutral pH. The major differences in average lake chemistry between regions were Cl, F, and SO4 concentrations.' /STUDY LOCATIONS:/ /MOUNT DESERT ISLAND/Bubble Pond/The Bowl/Eagle Lake/Jordan Pond/Sargent Mountain Pond/The Tarn/Lake Wood/