Youness Sharifi

The 1989 Exxon Valdez oil spill contaminated around 800 kilometers of shoreline in Prince William Sound, Alaska. Despite extensive cleanup efforts and nearly 20 years of natural weathering, subsurface oil residues persist in patches in some beaches. The hydrogeological mechanism causing the oil persistence was not fully understood due to the complex surface and groundwater interactions in the intertidal zone including tides, inland freshwater recharge, sediment heterogeneity, seawater density-effect and beach landforms. Based on field data and numerical simulations, we show that the persistence of oil is due to the two-layered structure (a high-permeability surface layer underlain by a low-permeability layer) in conjunction with a small freshwater recharge. The surface layer probably provided the oil a temporary storage for its slow, continuous filling of the lower layer whenever the water table dropped below the interface of the two layers due to small freshwater recharge from inla...

Twenty years after the Exxon Valdez oil spill in 1989, the oil is still lingering in beaches of Prince William Sound, Alaska. We conducted measurements of water level, salinity, nutrients, and dissolved oxygen in a beach on Eleanor Island heavily contaminated in 1989. The measurements were conducted in two transects: One transect contained Heavy Oil Residue (HOR) and the other was clean. Six pits were dug in each transect, and they ranged in depth from 0.9 m to 1.5 m. In each pit, a multiport sampling well and two sampling boxes (each around 200 ml in volume) were placed for collecting water samples at various depths. Nutrients measurements revealed that nitrate-N was around 0.2 mg/L at oiled pits, which is an order of magnitude lower than the concentration needed for optimal degradation of oil by micro-organisms. The dissolved oxygen was less than 0.6 mg/L in the oiled pits while it was, on the average, larger than 4.0 mg/L in the clean pits. This suggests that oxygen limitation co...

... Observations of mesoscale eddies in the South Atlantic Cape Basin: Baroclinic and deep barotropic eddy variability,. Baker-Yeboah, S., DA Byrne, and DR Watts (2010),. J. Geophys. Res., 115, C12069, doi:10.1029/2010JC006236. Publication Date: 29 December 2010. ...