Work

Depth profiles of dissolved and particulate lead indicate reversible scavenging in deep waters of the West Subtropical Pacific

Year: 2026

Type: article

Abstract: Despite the global phase-out of leaded gasoline, contemporary industrial sources, particularly from East Asia, continue to deliver lead (Pb) to the marine environment via atmospheric deposition. Here, we present depth profiles of dissolved Pb (dPb) and particulate Pb (pPb) in the western subtropical Pacific Ocean. Our results reveal pronounced northwest-to-southeast gradients in surface dPb, consistent with ongoing aeolian inputs. The distinct subsurface maxima, associated with the North Pacific Intermediate Water, align with observations from previous studies. Below 500 m, we observe both quasi-conservative transport of dPb with water masses and evidence of additional Pb inputs near the continent, likely supplied by advective transport and sinking particles with reversible scavenging. Combining our new data with published datasets reveals that deep-water (> 1200 m) dPb concentrations resemble the geographical distribution of surface dPb across the whole Pacific, indicating that particle-mediated vertical transport is a key pathway for delivering anthropogenic Pb to the deep ocean independently of deep-water formation. This study highlights the sustained influence of Asian emissions on the North Pacific and underscores the central role of reversible scavenging in the oceanic Pb cycle, providing new constraints on both external Pb inputs and internal cycling in a region of global significance.

Source: Earth and Planetary Science Letters

DOI: 10.1016/j.epsl.2026.119914