Chemical Cycling at the Ocean Margin: The Sedimentary Source

有关加利福尼亚大陆边缘沉积物和水之间微量金属循环的研究工作正在进行中。利用USC自由载具底部着陆器和计算毫米尺度上沉积物孔隙水的梯度来确定营养物和微量金属的通量。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是来自含氧良好的水域，而不是来自含氧最小带深度范围内的沉积物。此外，高通量与高氧消耗、碳氧化和碳酸钙溶解率有关。因此，新的工作正在解决金属和碳循环之间的联系。蒙特雷湾沉积物通量的测量值正在与正在进行的沉积物捕集器碳通量的测量值（查韦斯）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。还对模拟孔隙水剖面所得的通量进行了详细的研究，并与底栖生物室所得的通量进行了比较，后者往往给出更高的通量值。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，或者是动物的灌溉作用；目前正在调查这些可能性。

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.