Investigating the spatial variability of dissolved organic matter quantity and composition in Lake Wuliangsuhai

Abstract

Dissolved organic matter (DOM) is an important component of the carbon cycle and a critical driver in controlling a variety of biogeochemical and ecological processes in aquatic environments. We reported the spatial variability of DOM quantity and composition which collected from Lake Wuliangsuhai in arid and semi-arid region. This study could serve as a useful tool to assess the dynamics of DOM in similar complex wetlands or lakes and provide a support for ecological environment governance and restoration. The results showed that five fluorescent components, including three humic-like (C1, C2 and C4), and two protein-like components (C3 and C5), can be identified by excitation emission matrix (EEM) spectra combined with parallel factor analysis (PARAFAC) in Lake Wuliangsuhai. The spatial variation of the components showed the difference in the dominant fluorescent component. There were dominant protein-like component C5 and humic-like component C2 in water and pore water. Components C3 and C4 were the main fluorescent components in 0–10cm sediments. In 10–20cm sediments, C1 and C3 were the dominant humic-like and protein-like component respectively. The PARAFAC–PCA displayed four PCA factors. The humic-like components C2 and C4 concurrently showed positive factor 1 loadings. Factor 2 was mainly explained by terrestrial and marine humic-like component C1. The autochthonous, tryptophan-like, fluorescent component C3, showed positive factor 3 loadings. The autochthonous, tyrosine-like, fluorescence component C5, having a low factor loading in other three factors, showed extremely high factor 4 loading. The EEM–PARAFAC combined with PCA showed varying contributions of terrestrial versus autochthonous DOM sources for the different regions in the wetland, suggesting that differences in human activities control DOM dynamics.