Fig. 1. Fluorescence characteristics of humic substances. Component 1 and 3 were contributed by fulvic acid-like organic matter materials, and component 2 humic acid-like organic matter materials. EFa, Elliott soil standard fulvic acid; EHa, Elliott soil standard humic acid; LHa, Leonardite standard humic acid; PHa, Pahokee peat reference humic acid; WFa, Waskish peat reference fulvic acid; WHa, Waskish peat reference humic acid.