Differentiating Between Naturally Occurring and Anthropogenic Sources of Salts in Groundwater Within Cyclic Lacustrine Sequences of the Upper Triassic Lockatong Formation in New Jersey

Differentiating between the presence of naturally occurring (dissolution of rock formation salt deposits) and anthropogenic (e.g., water softeners, road salts, agricultural run-off, industrial operations) sources of salts in groundwater within the Lockatong formation can be difficult since the presence of salt in groundwater may be caused by either of these sources, or consist of a mixture of both sources.  The Lockatong formation is characterized by lacustrine sequences with cyclic variations that create significant variation in the presence of naturally occurring salts laterally and vertically, further complicating efforts to segregate the two source types. 

To segregate areas where groundwater salts resulted from natural conditions from areas where salts were caused by releases of waste waters from an industrial operation, we used a ‘weight-of-evidence’ approach consisting of many of the techniques outlined in Richter and Kreitler 1992 (e.g., the characteristics of salt concentrations and molar ratios in groundwater associated with each source type).  The identification of the source of salts present in groundwater within and around the area of a salt release was based on an evaluation of local and regional geology, groundwater flow direction including influences by local groundwater pumping, other anthropogenic sources, statistical analyses of groundwater salt concentrations in areas with no known anthropogenic sources and immediately adjacent to the known salt release, and a comparison of molar ratios of certain salts in groundwater from various areas.  This weight-of-evidence approach demonstrated that groundwater impacts by industrial operations are limited to a small area in the vicinity of the release  and that elevated naturally occurring salt concentrations, above secondary drinking water standards, are pervasive in groundwater in this portion of the Lockatong formation. 

Richter, B.C. and C.W. Kreitler.  1992. Identification of Sources of Ground Water Salinization Using Geochemical Techniques.  United States Environmental Protection Agency.  January.  EPA/600/S2-91/064.