The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Since the Industrial Revolution, a significant amount of lead (Pb) released by human activities has dispersed into the open ocean through aerosols. Due to limited in situ observation in the Northwest Pacific, little is known about the basin scale distribution and sources of Pb in its waters. This study provides a detailed analysis of the distribution of dissolved and particulate Pb during the 2019 GEOTRACE GP09 cruise. We found latitude-dependent variations of dissolved Pb at surface, with higher concentrations (up to 40 pM) observed at 21°N compared to lower concentrations (as low as 20 pM) at 11°N, possibly related to atmospheric deposition. Subsurface water exhibits a significant maximum dissolved Pb concentration (up to 80 pM), with the water thickness of such Pb maximum decreasing from 1000 m in the north to 400 m in the south. Water mass analysis suggests a link to the southward extension of Pb-enriched North Pacific Mode Water. Furthermore, deep-sea (>2000m) dissolved Pb concentrations decrease with increasing offshore distance, changing from 30 pM to 10 pM, while particulate Pb concentrations gradually decrease from 3 pM to 0.5 pM with a long distance of 2000 Km. This suggests that lithogenic Pb introduced through lateral transport is a significant source of elevated Pb concentrations in the deep Pacific.

northwest Pacific, GEOTRACES, dissolved lead, particulate lead, terrestrial input, atmospheric input, water mass mixing