THE CHEMICAL AND STATISTICAL ANALYSIS OF GEOCHEMICAL MARKERS IN KARST GROUNDWATER OF SPRINGFIELD, MO

Springfield, MO is located on the Springfield Plateau physiographic province. The Springfield plateau consists of a number of Mississippian aged units, with the Burlington-Keokuk limestone typically being the uppermost unit. The Burlington-Keokuk is a highly fossiliferous limestone with nodular and interbedded chert. Beneath the Burlington-Keokuk lie the Elsey, Reeds Spring, and Pierson Formations respectively. These formations comprise the Springfield Plateau aquifer hydro-stratigraphic unit. Within the Springfield Plateau aquifer a well-developed karst system includes springs, sinkholes, and caves with recharge primarily draining from springs and seeps. The Springfield Plateau aquifer is the predominant source for springs and seeps in the Springfield area.

The purpose of this study was to understand the differences in water chemistry of what are thought to be individual karst groundwater basins in Springfield. The mixture of urban, industrial, and rural land use over these groundwater basins as well as minute differences in the Burlington-Keokuk suggest that enough difference in the water chemistry exists and a signature can be defined for each basin. The objectives of this study were threefold: (1) collect and analyze water samples; (2) Determine groundwater basin signatures (if possible) using collected water quality data and statistical software; and (3) test the accuracy of these signatures by testing a few random samples against known basins. Sampling was conducted at 12 sites in Springfield, MO from within what are believed to be five separate groundwater basins (as defined by previous dye traces). Samples were collected over six months, and 11 variables were measured. Field tests included pH, temperature, conductivity, bicarbonate (as CaCO3), and flow. Major cations calcium, magnesium, and sodium were tested using atomic absorption in the Missouri State University Chemistry department. Major anions chloride, sulfate, and nitrate were analyzed by Springfield City Utilities Blackman lab. The statistical analyses were run using SAS 9.4 discriminant analysis function. Groundwater basin signature results as well as intra/inter-basin trends are discussed.