Large-scale dispersant leaching and effectiveness experiments with oils on calm water

Area of Science:

• Environmental science
• Marine pollution
• Chemical engineering

Background:

• Dispersants are used to treat oil spills, but their effectiveness is reduced in calm seas due to insufficient mixing energy.
• Application of dispersants during calm conditions is sometimes considered for later effectiveness when sea states improve.

Purpose of the Study:

• To investigate the persistence of dispersants in oil slicks on calm water.
• To determine how long treated oil slicks remain dispersible after initial application in non-ideal sea conditions.

Main Methods:

• Treated oil slicks were placed on static and flowing water in a large outdoor wave tank for up to six days.
• The dispersibility of these slicks was tested by exposing them to breaking waves after the standing period.

Main Results:

• Thicker oil slicks maintained complete dispersibility for up to six days in calm water.
• Thinner slicks and those exposed to water movement showed reduced dispersibility within two days.
• The primary cause for loss of dispersibility was identified as dispersant loss, not oil weathering.

Conclusions:

• The effectiveness of dispersants can diminish over time in calm conditions, particularly for thinner slicks or those experiencing water movement.
• Dispersant persistence is a critical factor in the success of oil spill treatments, influencing the optimal timing for application.
• Further research into dispersant longevity and factors affecting their stability is crucial for effective oil spill management strategies.