2.3.1 Chemical analysis
A portable water quality analyzer (HACH, HQ-40d) was used to measure the
temperature (T), pH, and electrical conductivity (EC) values at the
sampling sites. Additionally, the alkalinity
(HCO3- metering) of the samples was
measured by Gran titration with 0.025N HCl (aq.) in the field. The
samples for measuring cations were acidified to pH < 2 with
ultrapure HNO3. Approximately 200 mL of water was
subsampled from each water sample to measure the anion and cation
concentrations of Cl-,
SO42-,
NO3-, Na+,
K+, Ca2+, and Mg2+by ion chromatography (ICS-3000, DIONEX). The precision of the anion and
cation concentrations were better than 5 mg/L.