ROLE OF EUXINIC CONDITIONS IN ADSORBING ARSENIC IN ORGANIC MATTER AND PYRITE PRESERVED IN THE LOCKATONG FORMATION OF NEWARK: IMPLICATION TO THE QUALITY OF GROUNDWATER

The Lockatong formation of Newark basin is rich in organic matter. It hosts pyrite which occurs as dissemination, small patches, or parallel veins. The isotope sulfur isotope values of pyrite samples range from -7.5 to 0.5 ‰_CDT (average = -3.5‰_CDT). The negative δ³⁴S values are indicative of Bacterial Sulfate Reduction (BSR) under low temperature and euxinic conditions. It is under these conditions that Arsenic was incorporated into both organic matter and pyrites (pending Total Organic Carbon and Arsenic data). These euxinic conditions enhanced the preservation of organic matter, the formation of pyrite, and also the complexation/adsorption of Aresnic.The organic matter-rich anoxic levels of this formation and pyrites are potential sources of Arsenic in groundwater in Newark basin, with Arsenic values reaching up to 215 μg/L.