Impact of sub-watershed characteristics and changes on sediment DOM quantity and quality over Jiaozhou Bay

Abstract

Dissolved organic matter (DOM), which is influenced by watershed characteristics, plays an important role in carbon (C) budgets and reflects human impacts on the river ecosystem. This study aims to analyze the changes of land use and landscape patterns in three sub-watersheds and the effects of these sub-watershed characteristics on the content and quality characteristics of DOM. We collected sediment samples of different depth from exits of three sub-watersheds. Samples were analyzed for content and quality of DOM based on absorbance and fluorescence properties using ultraviolet–visible spectroscopy (UV–vis) absorbance and fluorescence spectroscopy. Results show that the land use types of the three sub-watersheds are mainly cropland and construction land. And the construction land area of three sub-watersheds increase from 2000 to 2018, while the area of cropland decrease. In addition, we find that forestland and cropland negatively influence sediment DOC contents and positively influence the proportion of humic fluorescence. And the water area has positive effect on protein-like DOM compounds. Moreover, the degree of fragmentation of the landscape has negative effects on sediment DOC contents. The connectivity of the landscape and the agglomeration of the patch have positive effects on humic-like components in sediment DOM at the exit of the sub-watershed. In general, sub-watershed characteristics have stronger effects on DOM quality than on its content. This study provides new insights on the importance of watershed characteristics on the content and quality of sediment DOM in river and supplies the support for river ecosystem management.