SEARCHING FOR SOURCES OF TRACE METALS IN THE SUSQUEHANNA RIVER NEAR BYERS ISLAND, SHAMOKIN DAM (NORTHUMBERLAND COUNTY) PA

In 2009, we found elevated levels of heavy metals (copper, lead, and manganese) in Susquehanna River water samples on the eastern side of Byers Island, an island in the Susquehanna River near Shamokin Dam. Subsequent studies in the summers of 2010 and 2011, designed to look for the sources of these metals, failed to even find the metals in the river water, possibly due to very high flow conditions in both summers. In this year’s study, we investigated the possibility that an old lead/zinc mine (Doughty Mine, in operation during the mid-1800’s and located near the Susquehanna riverbank on the eastern side of Byers Island) is affecting the geochemistry of the river. Water samples were collected by canoe and kayak from 18 sites: 3 on either side of Byers Island toward the upstream end, 3 on either side near the center of the island, and 3 on either side close to the downstream tip of the island. In situ analyses included pH, temperature, dissolved oxygen, and conductivity. Turbidity was measured immediately upon returning to shore on unfiltered samples; alkalinity and acidity were determined within hours of sampling on filtered samples. Subsamples were preserved for later laboratory analyses for simple cations and anions (filtered, ion chromatography) and selected metals (both filtered and unfiltered, acidified pH<2, ICP-OES). We found nitrate and sulfate concentrations lowest near the island. We have consistently observed segregation of West Branch water from North Branch water in the Susquehanna River at this site, and this sampling trip was no exception, with the two westernmost stations on each transect exhibiting water chemistry distinct from the more eastern sampling sites. In addition, both iron and manganese concentrations are highest in the sampling site nearest the eastern shore of the river in all three transects. Iron concentrations decrease downstream, whereas the peak of manganese is in the center transect, arguing for a potential source of manganese from the shore near the mine. Oddly enough, both lead and zinc were not detectable in any samples, including those closest to the mine.