Department of Earth Sciences and §Department of Biological Sciences and Department of Earth Sciences, University of Southern California , Los Angeles, California 90089-0740, United States.
Environ Sci Technol. 2014 Jul 15;48(14):7730-7. doi: 10.1021/es5019515. Epub 2014 Jul 7.
Understanding biogeochemical cycling of trace metals in the ocean requires information about variability in metal concentrations and distribution over short, e.g., diel, time scales. Such variability and the factors that influence it are poorly characterized. To address this shortcoming, we measured trace metal concentrations in the total dissolved, colloidal, and soluble fractions every 3-4 h for several consecutive days and nights in surface waters from a coastal station. Our results show that both the concentration and the size partitioning of some biologically essential (Fe, Cu, Co, and Cd) and anthropogenic (Pb) metals are subjected to diel variations that may be related to both inorganic and biological processes (e.g., photolysis of high-molecular-weight dissolved organic matter, photoinduced reduction/oxidation of metal(hydrous)oxides, uptake by growing phytoplankton, degradation of organic matter, lysis, and grazing). The largest fluctuations were observed in the soluble and colloidal pools. Soluble Fe varied during the day-night cycle by a factor of 40, and the contribution of colloidal Pb to the total dissolved fraction increased from 6±3% during the day to as much as 70-80% during the night. Our results suggest that changes occurring over time scales of hours need to be considered when collecting and interpreting trace metal data from the surface ocean.
了解海洋中痕量金属的生物地球化学循环需要有关金属浓度和分布在短时间内（例如昼夜）变化的信息。这种变化及其影响因素的特征描述很差。为了解决这一不足，我们在沿海站的表层水中连续几天和几个晚上每 3-4 小时测量一次总溶解、胶体和可溶解部分的痕量金属浓度。我们的结果表明，一些生物必需的（Fe、Cu、Co 和 Cd）和人为的（Pb）金属的浓度和大小分配都受到昼夜变化的影响，这些变化可能与无机和生物过程有关（例如，高分子量溶解有机物的光解、金属（水合）氧化物的光诱导还原/氧化、浮游植物的生长吸收、有机物的降解、裂解和摄食）。最大的波动发生在可溶解和胶体池中。可溶性 Fe 在昼夜周期内变化了 40 倍，胶体 Pb 对总溶解部分的贡献从白天的 6±3%增加到晚上的 70-80%。我们的结果表明，在收集和解释来自海洋表面的痕量金属数据时，需要考虑发生在小时时间尺度上的变化。
