The Response of Catchment Ecosystems in Eutrophic Agricultural Reservoirs to Water Quality Management Using DOM Fluorescence

Abstract

Three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy was used to investigate the characteristics of dissolved organic matter (DOM) in five typical eutrophic agricultural reservoirs. Based on catchment ecosystem, the five reservoirs were divided into three pollution sources of livestock, living, and farmland sources. The quantities and qualities of DOM in the reservoirs were analyzed. Our results showed that DOM characteristics were different in eutrophic reservoirs based on source. More protein-like components were observed in the reservoirs with the living sources, while more humic-like components were seen in the reservoir with farmland sources. Additionally, correlation analysis showed different sources for protein-like and humic-like components. Protein-like components originated mainly from phytoplankton (endogenous sources), and humic-like components were from terrestrial sources. Furthermore, the high values of specific fluorescence parameters were consistent with a dominant role of endogenous DOM in eutrophic water bodies, with FI values (fluorescence index) of approximately 1.9, and β:α values (freshness index) greater than 0.7. This result indicated that mixed features dominated endogenous sources in the reservoirs, regardless of terrestrial pollution sources. By comparing our fluorescence characteristics and historical references, we confirmed that catchment ecosystems related to human activities are important factors in determination of the characteristics of DOM in aquatic environments. However, complex and extensive eutrophication requires endogenous control of water bodies, which will play a central role in improving water environments and sustainable use of reservoirs. Therefore, this study provides an effective basis for water quality assessment of eutrophic agricultural reservoirs.

Natural sources and controlling factors of urea–nitrogen concentrations in agricultural drainage ditches

“…No significant differences were found among time points, but there was a peak in average BIX values (0.63) after the addition of the DON solution (2.61; Table 1). The BIX values of the mesocosm surface waters fell within the range reported from the pore waters of sediments (0.58–0.64) but were lower than agricultural reservoirs (0.99–1.41) and agriculturally impacted rivers (0.61–0.89; Begum et al., 2022; Jin et al., 2019; Lee et al., 2018; Pisani et al., 2020). The BIX results suggest that the DOM released from ditch sediments after storms is influenced by the slow degradation of complex DOM rather than newly produced sources from microorganisms.…”