Chemical Cycling at the Ocean Margin: The Sedimentary Source

有关加州大陆边缘沉积物和水之间痕量金属循环的工作正在进行中。营养素和痕量金属的通量正在通过使用南加州大学的自由运载工具海底着陆器和通过计算沉积物孔隙水中毫米尺度的梯度来确定。最初工作的一个令人惊讶的结果是，沉积物中金属再矿化率最高的似乎来自含氧量较高的水域，而不是氧最小带深度范围内的沉积物。此外，高通量与高耗氧率、碳氧化和碳酸钙溶解有关。因此，新的工作正在解决金属和碳循环之间的关联。蒙特利湾沉积物外通量的测量正在与(查韦斯)正在进行的沉积物捕集碳通量测量进行比较，以确定碳信号中的季节性是否反映在金属的再矿化率上。还在对模拟孔隙水剖面得出的通量与来自海底洞室的通量进行详细研究，后者往往给出较高的通量值。这种差异表明，沉积物表面的绒毛层发生了快速的成岩反应，或者是被动物灌溉；这种可能性正在调查中。

Work is in progress on the cycling of trace metals between sediment and water in the continental margin of California. Fluxes of nutrients and trace metals are being determined by using the USC free vehicle bottom lander and by calculation of gradients in pore waters of sediments on a millimeter scale. A surprising result of the initial work is that the highest rate of remineralization of metals from the sediment appears to be from well oxygenated waters, not from sediments in the depth range of the oxygen minimum zone. Moreover the high fluxes are linked with high rates of oxygen consumption, carbon oxidation, and calcium carbonate dissolution. Consequently, new work is addressing the association between metal and carbon cycling. Measurements of fluxes out of the sediments in Monterey Bay are being compared to ongoing measurements of sediment trap carbon fluxes (by Chavez) to determine whether seasonality in the carbon signal is reflected by remineralization rates of metals. A detailed study is also being made of fluxes derived from modelling pore water profiles, compared to those from the benthic chambers, which tend to give higher flux values. The discrepancy suggests rapid diagenetic reactions in the fluff layer at the sediment surface, or irrigation by infauna; the possibilities are being investigated.