2021 Organic Matter Research Lab Vectorized Fluorescence Data

The USGS CAWSC Organic Matter Research Laboratory (OMRL) provides laboratory services and support to regional and national projects in the analysis of organic matter using the latest methods in absorbance and fluorescence spectroscopy. Optical measurements such as absorbance and fluorescence are used to gain insight into dissolved organic matter (DOM) composition, and can also serve as proxies for more expensive and difficult to obtain measurements. These techniques are relatively rapid and inexpensive and allow for the comprehensive tracking of DOM dynamics in aquatic ecosystems ranging from rivers and lakes to estuaries to open marine systems. Absorbance spectra and fluorescence matrices were simultaneously collected on filtered water samples at room temperature (21 �C) in an acid-cleaned 1 cm quartz cuvette using a spectrofluorometer equipped with a charge-coupled device (CCD) (Aqualog�, Horiba Instruments, New Jersey, U.S.A.). Excitation and absorbance scans were performed using a double-grating monochrometer, a 150 W Xenon arc lamp, a 5 nm bandpass, and a 1 s integration time at wavelengths of 240-800 nm. Emission spectra were collected with a CCD at approximately 2.3 nm (4 pixel) intervals at wavelengths of 245?800 nm. Excitation and absorbance wavelengths were scanned from low to high energy (i.e., VIS to UV) to reduce UV exposure of the sample, thus limiting the effects of photobleaching during analysis. Laboratory fluorescence measurements collected on the Aqualog can provide validation or verification of field-based instrument fluorescence measurements where the sensor arrays are encompassed by the full Aqualog array (Booth and others, 2023). This approach may be superior to the other correction approaches where interferences are large, especially in cases where the field sensor measurements constitute less than 10% of the fully corrected value. For projects that already collect discrete samples during field sensor maintenance visits, the cost and effort is minimal for the data quality benefit. Data presented here were analyzed by the U.S Geological Survey California Water Science Center Organic Matter Research Lab, Sacramento CA. This release contains vectorized fluorescence data measured on the Aqualog � fluorometer January-December 2021.

美国地质调查局加利福尼亚水科学中心（USGS CAWSC）有机质研究实验室（OMRL）提供实验室服务与技术支持，承接区域及国家级项目，采用吸光光谱与荧光光谱领域的前沿方法开展有机质分析工作。吸光度与荧光等光学测量手段可用于解析溶解性有机质（dissolved organic matter, DOM）的组成，同时可作为成本高昂且难以获取的传统测量方法的替代指标。这些技术相对快速便捷、成本低廉，能够全面追踪从河流、湖泊到河口乃至开阔海洋系统的水生生态系统中DOM的动态变化过程。本研究在室温（21℃）下，使用经酸清洗的1cm石英比色皿，搭配搭载电荷耦合器件（charge-coupled device, CCD）的Aqualog®荧光分光光度计（堀场仪器公司，美国新泽西州），对过滤后的水样同步采集吸光光谱与荧光矩阵数据。激发与吸光度扫描采用双光栅单色器、150W氙弧灯，设置5nm通带带宽与1秒积分时间，扫描波长范围为240~800nm。发射光谱通过电荷耦合器件以约2.3nm（4像素）的间隔采集，波长范围为245~800nm。为降低样品的紫外曝光量以抑制分析过程中的光漂白效应，激发与吸光度扫描按照从低能到高能（即从可见光区至紫外光区）的顺序进行。通过Aqualog荧光分光光度计获取的实验室荧光测量数据，可用于验证野外原位仪器的荧光测量结果——当野外传感器阵列覆盖Aqualog完整阵列范围时（Booth等，2023）。当干扰效应较强时，该验证方法优于其他校正手段，尤其适用于野外传感器测量值仅占完全校正后数值10%以下的场景。对于在野外传感器维护期间已采集离散水样的项目而言，该方法仅需少量额外成本与工作量，即可显著提升数据质量。本数据集所呈现的数据由美国地质调查局加利福尼亚水科学中心有机质研究实验室（美国加利福尼亚州萨克拉门托）分析完成。本次发布的数据为2021年1月至12月使用Aqualog®荧光分光光度计测得的矢量化荧光数据。