Evaluating Soil Dissolved Organic Matter Extraction Using Three-Dimensional Excitation-Emission Matrix Fluorescence Spectroscopy

Soil dissolved organic matter (DOM) consists of many organic compounds and plays an important role in contaminant transport in the ecosystem. However, the effects of different extraction conditions on contents of different DOM components are poorly understood. We extracted DOM from three soils using different extraction times, solid to liquid ratios (SLR), and extraction solution (KCl) concentrations, and evaluated the extractions using three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy. The sum of the contents of the main DOM components (protein-, fulvic-, and humic-like compounds) increased by 0.6-3.5, 2.5-3.9, and 0.11-0.37 times (P < 0.05) when SLR decreased from 1:2 to 1:10, the extraction solution concentration increased from 0.01 to 1.5 mol L−1, and extraction time increased from 10 to 300 min, respectively. The three-dimensional EEM fluorescence spectroscopy is a useful tool to characterize the components of DOM and evaluate DOM extraction in soils.