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Fig. 9 | Geochemical Transactions

Fig. 9

From: How long do natural waters “remember” release incidents of Marcellus Shale waters: a first order approximation using reactive transport modeling

Fig. 9

The memory index of natural waters: Cmax and a τrecovery and b τrr of major species in the river (filled squares), SG aquifer (filled triangles), and S aquifer with high release (filled circles), medium release (crossed circles), and low release rates (open circles). Both are calculated from the modeling output of spatio-temporal concentration evolution. The Cmax is determined as the maximum aqueous concentration during release. The τrecovery is the time scale for each species to return to within 5% difference from its background concentrations in natural waters. The relative recovery time τrr, calculated as the ratio of τrecovery over τr, is a measure of the time scale that natural waters remember the incident relative to their residence time. Each species is represented by one color, with dashed line of the same color being their drinking water standard. In S aquifer with abundant clay, τrr values depend on cation affinity to solid surface with τrr between 5 and 10 for Na, Ca, and Mg, and 15–20 for Sr and Ba

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