Department of Earth Sciences, Centre for Trace Metal and Experimental Biogeochemistry (TracEx), Stellenbosch University, Stellenbosch, 7600, South Africa.
Department of Oceanography, University of Cape Town, Rondebosch, 7701, South Africa.
Sci Rep. 2023 Apr 4;13(1):5465. doi: 10.1038/s41598-023-32613-5.
Using a spatiotemporal dataset of dissolved lead (dPb) from the subtropical oceans surrounding South Africa, this study quantifies the exchange of dPb between the Indian and Atlantic Oceans. Despite the absence of a major Pb source within the South Atlantic sector and the complete phase-out of leaded petroleum in Southern Africa, the ecologically important southeast Cape Basin shows an elevated surface dPb concentration (21-30 pmol kg). We estimated up to 90% of the measured dPb in surface waters of the Cape Basin was delivered from the Indian Ocean via the Agulhas Current (AC). Eddy dynamics and leakage at Agulhas retroflection result in an increased Pb flux from winter to summer, while a long-term (2008-2019) temporal change in dPb in the AC-derived water of Cape Basin was contemporaneous to a change in atmospheric Pb emissions from South Africa. The South African-origin atmospheric Pb, however, contributes first to the Agulhas waters in the West Indian Ocean, which is then transported to the South Atlantic, thereby regulating the dPb inventory of the Cape Basin. This indirect mechanism of Pb transfer emphasizes the importance of regulating Pb emissions from Southern Africa to protect rich fishing grounds associated with the Benguela marine ecosystem.
利用来自南非周边亚热带海洋的溶解铅（dPb）时空数据集，本研究量化了印度洋和大西洋之间 dPb 的交换。尽管南大西洋扇区没有主要的 Pb 源，且南非已全面淘汰含铅石油，但生态重要的东南开普敦盆地的表层 dPb 浓度（21-30 pmol kg）仍然很高。我们估计，开普敦盆地表层水中测量到的 dPb 中高达 90%是通过阿古拉斯洋流（AC）从印度洋输送来的。阿古拉斯折返处的涡流动力学和泄漏导致冬季到夏季 Pb 通量增加，而开普敦盆地 AC 衍生水中 dPb 的长期（2008-2019 年）变化与南非大气 Pb 排放的变化同时发生。然而，源自南非的大气 Pb 首先对西印度洋的阿古拉斯水域产生影响，然后再输送到南大西洋，从而调节开普敦盆地的 dPb 储量。这种 Pb 转移的间接机制强调了调节来自南非的 Pb 排放以保护与本格拉海洋生态系统相关的丰富渔业区的重要性。
