Fig. 2. Elemental concentrations in samples.

a–e Cation concentrations with respect to salinity, organized by lithologic aquifer type, plotted alongside relevant endmember values: seawater and global average riverine endmembers (references available in Table 1), as well as the average global groundwater composition calculated in this study. Linear regressions across all the data are plotted for each element to provide context of what conservative (Li, Mg, Ca, and Sr) vs. non-conservative (Ba) mixing across the salinity gradients would appear as. Sample sizes (n) are provided here: a [Li]: (n = 136), b [Mg]: (n = 139), c [Ca] (n = 140), d [Sr] (n = 225), e [Ba] (n = 56).