Contemporary chemistry of Nova Scotian lakes

Abstract

Water samples were collected from 234 Nova Scotian lakes during the summers of 1981–1984. Samples from near-surface and mid-depth were composited to yield a single descriptive analysis for each lake. Median pH for the lakes was 5.37 (arithmetic mean 5.7), and ranged from 4.4 to 7.7. Conductivities <133 μS cm⁻¹ were found for 96% of the lakes with higher values for lakes influenced by road salt, proximity to the sea, or geology. The most dilute lake (19.8 μS cm⁻¹) was approximately the salinity of rain water. Sodium, the most abundant cation (216 μeq L⁻¹) was 2.5x more concentrated than Ca. Among anions, Cl (228 μeq L⁻¹) exceeded SO₄ by 2.7 times. Alkalinity averaged 48 μeq L⁻¹, and 16% of the lakes (n = 37) had no measurable alkalinity at a detection limit of 2 μeq L⁻¹. Non-marine fractions of ions were calculated from the ratio of Cl to SO₄ in standard seawater, and ranged from 9.8% for Na to 1001 for eight other ions. As with Na, Mg is strongly influenced by sea spray, while K is apparently influenced almost equally by marine and terrestrial sources. Sulfate and Ca are both strongly influenced by terrestrial sources. Color in the study lakes was as high as 300 T.C.U., and the implicit role of organic anion (ca. 50 ueq L⁻¹) in the ion sum is reviewed. Interactions between selected ion pairs are reviewed to examine the role of non-marine ions (e.g. SO^* ₄, Ca^*, K^*) in lake chemistry. Results for Al, Fe, Mn, and alkalinity are also considered.