Superoxide decay kinetics in the southern ocean.

Area of Science:

• Chemical Oceanography
• Marine Chemistry
• Environmental Science

Background:

• Superoxide (O(2)(-)) plays a role in marine biogeochemical cycles.
• Understanding superoxide sinks is crucial for polar marine environments.
• Previous studies lacked detailed kinetic data in Southern Ocean waters.

Purpose of the Study:

• Investigate superoxide reaction kinetics in Antarctic waters.
• Determine the primary sinks of superoxide, focusing on dissolved organic matter and metals.
• Assess the role of copper and iron in superoxide's fate.

Main Methods:

• Utilized a modified chemiluminescence flow injection system with MCLA for superoxide detection.
• Conducted transects in the Drake Passage aboard the research icebreaker Polarstern.
• Employed DTPA additions to isolate metal-mediated reactions and metal titrations to assess reactivity.

Main Results:

• Superoxide half-life in ambient seawater ranged from 9.3 to 194 seconds.
• O(2)(-) decay rates indicated dismutation as the dominant reaction, not reaction with dissolved organic matter.
• Copper was identified as the major sink for superoxide throughout the water column.

Conclusions:

• Superoxide's reactivity in polar waters is primarily governed by dismutation and metal interactions.
• Organic chelation of copper and iron significantly influences their reactivity with superoxide.
• The developed strategy offers a novel approach for determining iron and copper speciation in seawater.