Abstract
We analyzed alkalinity in low-alkalinity streams using high-accuracy potentiometric titration by Gran's plot method for the end-point detection. Alkalinity determined by Gran's plot method for samples after the dissolved CO2 was removed by bubbling with N2 gas was almost the same as that for unaerated samples, but the former was easier to handle. The Japanese Industrial Standards (JIS-K0101) method could not accurately determine alkalinity lower than 100 μeq/l in stream waters like those on the island of Yakushima, where the bedrock is dominantly granite, leading to overestimate alkalinity up to 56%. Gran's plot method is thus superior for measurement of alkalinity in low-alkalinity watersheds.
