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首页> 外文期刊>Marine Chemistry >An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of ~(234)Th as a POC flux proxy
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An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of ~(234)Th as a POC flux proxy

机译：评估海洋中颗粒状有机碳与or-234的比率及其对〜（234）Th作为POC助熔剂应用的影响

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摘要

Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the ~(234)Th activity distribution (in order to calculate ~(234)Th fluxes) and an estimate of the C/~(234)Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C/~(234)Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C/~(234)Th either increases or is relatively invariant with increasing particle size (size classes> 1 to 100s μm). Observations also suggest that C/~(234)Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from ~(234)Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2-3). We recommend sampling for C/~(234)Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple ~(234)Th profiles and C/~(234)Th samples during the course of longer observation periods to better sample temporal variations in both ~(234)Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column.
机译：ium 234被越来越多地用作海洋粒子通量的示踪剂，主要是用来估计从表层海洋中输出的颗粒有机碳的一种手段。这就需要确定〜（234）Th活度分布（以便计算〜（234）Th通量）和对沉没粒子上C /〜（234）Th比率的估计，以凭经验得出C通量。在审查C /〜（234）Th变异性时，使用单一采样方法获得的结果显示出最可预测的行为。例如，在大多数采用原位泵收集粒度分级颗粒的研究中，C /〜（234）Th随粒度的增加而增加或相对不变（粒度等级> 1至100sμm）。观测结果还表明，C /〜（234）Th随深度而降低，并且在不同区域之间可能会发生显着变化（大型硅藻盛开和沿海高产环境中最高）。从〜（234）Th得出的C通量的比较表明，它与C通量的独立估计值具有很好的一致性，包括在适当的空间和时间范围内（2-3因子之内）C和养分的质量平衡。我们建议从100 m的标准深度或至少在混合层以下的一个深度采样C /〜（234）Th，使用大体积大小的分级过滤以捕获稀有的大颗粒，或者使用沉淀池或其他装置进行采样。收集下沉的颗粒。我们还建议在较长的观察周期内收集多个〜（234）Th轮廓和C /〜（234）Th样本，以更好地采样〜（234）Th通量和下沉颗粒特征的时间变化。经过优化的新技术使我们感到鼓舞，这些新技术可以更可靠地对真正沉降的颗粒进行采样，并期望这种示踪剂的效用得到提高，这不仅适用于上层海洋碳通量，而且适用于水柱深处的其他元素和过程。

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