“…No significant relationships were found among any of the measured parameters and the sDII categories, although significant seasonal variation was observed. Forty physical and chemical parameters were measured for this study (SI Appendix, Table S5), and, of these, specific conductance (as a proxy for TDS) and dissolved Cl, Br, Ca, Na, Li, B, Ba, and Sr are known as useful geochemical tracers of produced water (24,25,28,29,76,77). The pH was measured as a potential indicator for acids used in shale gas well completion and for potential effects on microbial and macroinvertebrate communities (32,33,48,78).…”