COMPOSITIONAL ANALYSES OF CHRISTMAS 2020 FLOOD ALLUVIUM OF THE SUSQUEHANNA RIVER

Susquehanna River flood alluvium collected following the Christmas 2020 flood reveals elemental and mineralogical differences between the West and North Branches of the Susquehanna River. Based on this study, the West Branch of the Susquehanna River is more greatly influenced by acid mine drainage (AMD) than the North Branch. Between December 17 and 25, 2020, two major storms contributed abundant snow (nearly 4 ft in some regions) and rain (2-3 in) resulting in minor flooding of the West Branch and main stem but moderate flooding of the North Branch.

114 sediment samples were collected along both branches from Lock Haven (West) and Sayre (North) to the confluence (Northumberland) and along the Main Stem, to Halifax/Duncannon. Some of the sediment was dried, pulverized, pressed into pellets and analyzed for elemental chemistry using X-ray fluorescence (XRF). Some sediment was wet sieved to separate fine and coarse sediment. Both size distributions were analyzed using X-ray diffraction (XRD). Samples were also analyzed for grain size using a Bouyocous Hydrometer (ASTM 152B) to determine the density in a sample suspension.

Metals associated with AMD, (Fe2O3, ZnO, MnO, and SO3) were elevated in the West Branch. This is due to the presence of transported iron oxide nodules. These nodules and rip-up clasts were derived from eroded areas upstream, near their Carboniferous mining source. The iron oxide nodules deteriorate downstream through abrasion and transport. Additionally, Na2O values were elevated due to the use of excessive road salts from the winter storm. SiO2 and Al2O3 values were inverse with distance downstream and between the branches. The mineralogy of samples (quartz, orthoclase, kaolinite, illite, chlorite, vermiculite, and magnetite) does not appear to correspond to the chemistry along the West Branch due to the iron-enriched nodules. By knowing the composition of the sediment in the Susquehanna we can understand its overall environmental impact.