Boundary exchange completes the marine Pb cycle jigsaw

Area of Science:

• Geochemistry
• Oceanography
• Environmental Science

Background:

• Material fluxes at the land-ocean interface are critical for seawater composition and global element cycling.
• Research has predominantly focused on dissolved fluxes, overlooking the substantial role of particulate matter.
• For elements like lead (Pb), particulate fluxes are orders of magnitude higher than dissolved fluxes, suggesting their importance in elemental cycling.

Purpose of the Study:

• To investigate the significance of particulate-dissolved exchange in controlling dissolved lead (Pb) concentration and isotopic composition in the ocean.
• To quantify the contribution of particulate-dissolved exchange to oceanic Pb budgets, particularly in pre-anthropogenic conditions.

Main Methods:

• Chemical analyses of samples collected from equatorial Southeast Asia.
• Development and application of model simulations to assess Pb fluxes and exchange mechanisms.

Main Results:

• Particulate-dissolved exchange is identified as a key mechanism regulating dissolved Pb in seawater.
• Model simulations indicate that Pb input from particulate-dissolved exchange at ocean boundaries is comparable to or exceeds other major Pb sources in the pre-anthropogenic ocean.
• The study highlights the underappreciated role of particulate matter in marine Pb cycling.

Conclusions:

• Boundary exchange processes, particularly involving particulate matter, are crucial for understanding marine element cycling.
• The findings emphasize the need to consider particulate fluxes in assessing global element budgets and weathering-climate feedbacks.
• This research underscores the importance of studying particulate matter's role in ocean biogeochemical processes.