To obtain realistic metal exposure profiles at the metal-contaminated sites where ecological risks due to the five metals were of concern, we first calculated the sum of TUs by dividing the measured dissolved metal concentrations by the U.S. EPA hardnessadjusted water quality criteria for aquatic life (U. S. Environmental Protection Agency, 2016; U.S. Environmental Protection Agency, 2002). The water quality criteria for a water hardness of 20 mg/L were used as conservative "safe" concentrations (Cu: 2.3 μg/L, Zn: 30.2 μg/L, Pb: 0.42 μg/L, Cd: 0.21 μg/L, Ni: 13.3 μg/L, and Al: 220 μg/L) because water hardness at many of the sampling sites were as low as 20 mg/L (Table ). We used U.S.