Unveiling the Complexity of Lead Distribution in the Pacific Ocean: Insights from the GEOTRACES GP15 Transect

The space- and time-dependent emission patterns of anthropogenic lead (Pb) and its isotope ratios have created a global geochemical experiment that elucidates the processes of advective, mixing, chemical, and particle flux that redistribute Pb within the ocean. The recent study by Jiang et al. (2025) utilized data collected during the GEOTRACES GP15 transect to investigate the distribution and sources of Pb in the Pacific Ocean. This comprehensive analysis, spanning from the Alaskan coast to Tahiti along the 152°W, offers a unique perspective on the complexities of Pb cycling and its potential as an oceanographic tracer.

One of the key findings of the study is the identification of distinct Pb sources across the Pacific Ocean, with significant differences observed along the latitudinal gradient. By analyzing the isotope ratios of ²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb, and ²⁰⁶Pb/²⁰⁴Pb, the study was able to distinguish between American, Australian, and Chinese Pb sources. Correlating the Pb isotope data from the near‐sea surface aerosols collected during the cruise, the study reveals the spatial variations in Pb sources and their contribution to the overall Pb budget in the Pacific Ocean.

The study also highlights the role of advective transport in Pb distribution, evident in the low Australian ²⁰⁶Pb/²⁰⁷Pb observed in the Sub‐Antarctic Mode Water (SAMW) at the southernmost stations, and in the penetration of dense Pacific Bottom Water through the passageways south of Hawaii. The GP15 PMT section connects to the GP16 EPZT section, providing a N‐S and E‐W three‐dimensional view of the Pb isotope distribution in a key region for intermediate and deep water circulation.

In conjunction with the previously published study of Lanning et al. (2023), which focus on the role of particle-rich ‘veils’ in the vertical transport of anthropogenic dPb isotopes, the two studies from GP15 transect significantly contribute to our understanding of the complex dynamics of Pb distribution in the Pacific Ocean. They provides valuable insights into the sources, transport, and cycling of Pb in the marine environment, advancing the filed of oceanographic trace element research.

References:

Jiang, S., Lanning, N., Boyle, E., Fitzsimmons, J., Ramezani, J., Wang, A. G., & Zhang, J. (2025). Meridional Central Pacific Ocean Depth Section for Pb and Pb Isotopes (GEOTRACES GP15, 152°W, 56°N to 20°S) Including Shipboard Aerosols. Journal of Geophysical Research: Oceans, 130. Access the paper:10.1029/2024jc021674

Lanning, N. T., Jiang, S., Amaral, V. J., Mateos, K., Steffen, J. M., Lam, P. J., Boyle, E. A., & Fitzsimmons, J. N. (2023). Isotopes illustrate vertical transport of anthropogenic Pb by reversible scavenging within Pacific Ocean particle veils. Proceedings of the National Academy of Sciences, 120. Access the paper:10.1073/pnas.2219688120

Boyle, E. A., Zurbrick, C., Lee, J.-M., Till, R., Till, C. P., Zhang, J., & Flegal, A. R. (2020). Lead and lead isotopes in the U.S. GEOTRACES East Pacific zonal transect (GEOTRACES GP16). Marine Chemistry, 227. Access the paper: 10.1016/j.marchem.2020.103892