Optimum Nitrogen Concentration Supporting Maximum Crude Oil Biodegradation in Microcosms

2010

Water Qual Expo Health

Self Cite

Knowledge of the oxygen and nutrient concentrations in an oil-contaminated Prince William Sound (PWS) beach is important for understanding of the oil persistence over two decades after the Exxon Valdez spill. It was traditionally believed that there was enough oxygen in the contaminated shorelines to sustain aerobic microbial metabolism of oil and that nutrients were the major factors limiting oil biodegradation. In the present study, we analyzed the oxygen and nutrients levels in both clean and oily areas on a PWS beach that was heavily contaminated by the Exxon Valdez oil spill. We found that the level of nitrogen and phosphorous were 0.454 mg-N L −1 and 0.033 mg-P L −1 , respectively, which is not sufficient to fully support microbial growth, confirming that nutrient concentration was a major factor limiting oil transformation by biological ways. We also observed that the oxygen level varied from higher than 3 mg L −1 in the clean wells to about 1 mg L −1 (near anoxic level) in the oily wells. In addition, the lowest nitrate levels were observed at the oily wells. Altogether, these results suggest that the low level of efficient electron acceptors (oxygen and nitrate) detected at the oily spot is responsible for slow and potentially inefficient biodegradation of the oil.

Section: Discussionmentioning

confidence: 48%

The Effect of Pore Water Chemistry on the Biodegradation of the Exxon Valdez Oil Spill

Sharifi

Aken

2010

Water Qual Expo Health

Self Cite

“…This led to a major effort where around 55 tons of nutrients were applied on beaches of PWS (Bragg et al 1994). A recent study (Eslinger et al 2001) found that the maximum concentration of nutrient in PWS is less than 0.20 mg‐N/L, an order of magnitude smaller than the minimum needed for optimal (70%) biodegradation of hydrocarbons (Boufadel et al 1999; Du et al 1999; Zhu et al 2001).…”

Section: Introductionmentioning

confidence: 98%

Feasibility of High Pressure Injection of Chemicals into the Subsurface for the Bioremediation of the Exxon Valdez Oil

Groundwater Monitoring Rem

Bobo

2010

Self Cite

Delivery of dissolved chemicals to bioremediate oil from the Exxon Valdez oil spill was investigated at Beach EL056C of Eleanor Island, Prince William Sound, Alaska. The delivery technique was high pressure injection (HPI) of an inert tracer, lithium, at the approximate depth of 1.0 m into the beach near the mid‐tide line. The results revealed that the maximum injection flow rate was 3.0 L/min and the associated pressure was around 196 kPa. Therefore, exceeding any of these values would probably cause failure of the injection system. The injected tracer was monitored at multiple depths of four surrounding observation wells, and the results showed that the tracer plume occupied an area of 12 m2 within 24 h. The tracer plume traveled at the average speeds of 10 m/d in the seaward direction and 1.7 m/d in other directions. The rapid movement under HPI and the large diameter of influence (3.0 m) indicated that bioremediation of the Exxon Valdez oil on this beach via injection of chemicals is logistically feasible.

“…A more recent study by Atlas and Bragg (2009) on the beach under study in this article found an average nutrient concentration of 0.24 mg N/L. Therefore, the nutrient nitrogen concentration is an order of magnitude smaller than the minimum needed for optimal biodegradation of hydrocarbons, which ranges from 2.0 to 10 mg/L (Boufadel et al 1999; Du et al 1999; Zhu et al 2001).…”

Section: Introductionmentioning

confidence: 64%

Feasibility of Deep Nutrients Delivery into a Prince William Sound Beach for the Bioremediation of the Exxon Valdez Oil Spill

Groundwater Monitoring Rem

Bobo

Xia

2011

Self Cite

Delivery of dissolved chemicals to potentially bioremediate oil from the Exxon Valdez oil spill was investigated at Smith Island, Prince William Sound, Alaska. Two transects for tracer application were installed: one at a clean area and another at an oiled area. Tracer delivery occurred under ambient pressure through manifolds. Lithium in LiBr/sea water solution was the inert tracer, and the solution (82.6 mg/L of lithium) was released at a flow rate of 0.23 L/min for 58.5 h. While maintaining the flow rate, the solution was switched to sea water (i.e., 0.0 mg/L of lithium) for 16 h. The results show that the tracer moved landward with rising tides and seaward with falling tides. The plume got deeper moving landward and shallower moving seaward of the manifold. Thus, in situations where oil biodegradation is limited by the availability of nutrients or oxygen, applying these chemicals by this technique would allow them to reach entrapped oil seaward of the manifold from below. The seaward plume traveling speed (around 2.0 m/d) suggests that this technique is logistically feasible from a hydraulic point of view.