Major, Minor, and Trace Element Results from Sequential Extractions of Sediment Cores Collected from the National Crude Oil Spill Fate and Natural Attenuation Research Site near Bemidji, Minnesota, 2014 to 2019

This U.S. Geological Survey (USGS) Data Release contains chemical analysis information on sediment core and oil samples collected at the National Crude Oil Spill Fate and Natural Attenuation Research Site near Bemidji, Minnesota, USA. Following a crude-oil spill in 1979, biodegradation of petroleum hydrocarbons in the contaminated aquifer has formed distinct zones of pH and/or redox state downgradient from the spill site (Baedecker et al., 1993; Bennett et al., 1993; Jones et al., 2023). Geogenic trace elements were mobilized from sediment into groundwater because of these geochemical changes (Baedecker et al., 1993; Ziegler et al., 2017; Jones et al., 2023). Trace elements mobilized from sediment were identified in the groundwater, co-occurring with contaminants indicative of the crude-oil plume. Sediment cores were collected between 2014 and 2019. Sequential extractions of sediment from geochemical zones along the plume path were used to elucidate the sediment phase origins of 30 trace elements and provide insight into mobilization and attenuation mechanisms. Extractions targeted elements in surface exchangeable, carbonate, oxide, hydroxide, and organic phases. Inductively coupled plasma-mass spectrometry and optical emission spectroscopy were employed to analyze sediment extracts for Li (lithium), Be (beryllium), B (boron), Na (sodium), Mg (magnesium), Al (aluminum), Si (silicon), K (potassium), Ca (calcium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Zn (zinc), As (arsenic), Se (selenium), Rb (rubidium), Sr (strontium), Mo (molybdenum), Ag (silver), Cd (cadmium), Sb (antimony), Ba (barium), La (lanthanum), Tl (thallium), Pb (lead), Ce (cerium), and U (uranium).