20090330151223 20200616165227 Table 3 from Hem (1985) "Study and Interpretation of the Chemical Characteristics of Natural Water", U.S. Geological Survey Water-Supply Paper 2254. %PROGRAMFILES%\Gwb\Gtdata\thermo.tdat %PROGRAMFILES%\Gwb\Gtdata\WaterQualityRegs.dat %PROGRAMFILES%\Gwb\Gtdata\conductivity-USGS.dat Sample ID SiO2(aq) Al+++ Fe++ Ca++ Mg++ Na+ K+ HCO3- SO4-- Cl- F- NO3- TDS pH Amazon River 0.116502979979795 0.002594370216629913 0.001074363887048543 0.1072854291417166 0.04525817732976754 0.07829559195817276 0.3113881190682612 0.03123126124325405 0.05359207965475417 0.01052720229071922 0.001612775764496032 28 6.5 Mississippi River 0.1314819345486258 0.0003581212956828478 0.9481037924151696 0.4114379757251595 0.8699510217574751 0.07417202282452177 1.851939866037553 0.5309314411353189 0.6769525851126843 0.01579080343607883 0.03870661834790476 232 7.4 World average 0.2163626771053337 0.374251497005988 0.1686895700473154 0.2740345718536046 0.05882608706772417 0.9505532055767973 0.1145146245585982 0.2200095901616224 0.01612775764496032 89