Waters supplying the SNARC and WARU research facilities are
pumped from the same water-bearing geological formation (the Sparta
Sand Aquifer, also called the Middle Claiborne Aquifer) and from
approximately the same depth (330 m). However, the facilities are
124 km (77 miles) apart and the aquifer is known to yield waters that
differ markedly in appearance and chemistry depending on location
(Waldron et al., 2011). The SNARC facility lies near thewestern outcrop
of the aquifer in central Arkansas in a transitional area between
calcium-bicarbonate-type waters near the aquifer outcrop and
sodium-bicarbonate-type waters to the south and east (Renken,
1998). The WARU facility is southeast of Stuttgart, over the central
downdip region of the aquifer which yields sodium-carbonate-type
waters with a higher total dissolved solid content than waters to the
north and west. Aquifer material in the downdip region contains
lignite—a soft coal derived from compressed peat. Lignite in the Sparta
Sand Aquifer originated from vegetation deposited with fluvial sands
during late Eocene construction of the delta systemthat was eventually
buried to become the aquifer (Waldron et al., 2011). Color associated
with dissolved organic matter (DOM) derived from contact of the
water with lignite is visually obvious in theWARU water (Fig. 1). Comprehensive
chemical analysis of the two waters showed differences in
every analyte, as expected. Most differences were judged to be quantitatively
minor or of no biological significance. For clarity, only important
analytes are shown in Table 1. The complete analytical report can be
obtained from the corresponding autho