OTOLITH MICROCHEMISTRY AS A NOVEL INDICATOR OF FRACK WATER POLLUTION

Marcellus Shale fracking in Pennsylvania has created much concern for the surrounding environments. A main concern is fracking fluids polluting surface and ground waters. Rules and Regulations are in place for large scale or prolonged spills, however small spills or slow leaks may be over looked simply because monitoring is inadequate due to the ephemeral nature of the discharge. A novel approach to find evidence of these small scale spills hides within fish otoliths. Otoliths grow daily concentric rings of calcium carbonate, incorporating elemental components of the water they are living in. Two major cations in frac water, Sr and Ba, easily replace Ca from the otolith structure. Fish exposed to frac water would therefore incorporate the high concentrations (compared to natural stream water) of Sr and Ba into their otoliths, thereby recording the presence of frac water exposure.

Brook Trout were held in 990L of regional well water for 15 days. Tanks were then injected with one of four concentrations (0.0% control, 0.01%, 0.1% and 1%) of fabricated frac water for a 2, 15, or 30-day period. Otoliths were sectioned to expose growth rings, polished, and embedded on glass slides. LA-ICP-MS analysis were performed on dual transects; from edge to center of otolith and from center to edge. Preliminary data show increases in Sr and Ba at the start of exposure for each concentration and length of exposure. Fish exposed for 2 days were then held in control water for another 15 days. There is a defined increase and decrease in Sr and Ba concentrations indicating the 2-day period at all concentrations.

All fish exposed to frac water, irrelevant of concentration or exposure time, recorded an increase in Sr and Ba cations within their otoliths. This knowledge, applied to wild fish living near or downstream from drilling sites, may be used as a tool by regulatory organizations in order to determine if there has been any spills or slow leaks from surrounding drill sites.