Optical properties of sedimentary dissolved organic matter in intertidal zones along the coast of China: Influence of anthropogenic activities

The intertidal zone, due to its location in the transition zone of terrestrial and marine ecosystems, is seriously disturbed by anthropogenic activities such as fuel combustion and industrial production, causing significant increase in dissolved organic matter (DOM). However, the distribution and properties of DOM in intertidal sediments at the large scale and their correlations with local socio-economic indicators remain unclear. In this study, we collected sediment samples from 13 intertidal zones across 11 coastal provinces in China and analyzed optical properties and compositions of sed-imentary DOM. The results showed that the physico-chemical properties of sediment, such as pH and texture, affected the content of organic matter, thereby influencing the concentration of sedimentary DOM indirectly. The contents of fulvic acid-and protein-like components were relatively higher than humic acid-like component at all sampling sites. Moreover, urbanization could lead to the release of aromatic and humified organic matters into intertidal zones. Un-like coal, oil consumption exhibited positive correlation with SUVA254, indicating that the combustion of oil released more aromatic compounds. These findings revealed the impact of anthropogenic activities on sedimentary DOM and provided theoretical basis for predicting and regulating intertidal carbon sink.