Characterization of CDOM in saline and freshwater lakes across China using spectroscopic analysis

Abstract

China were examined to determine relationships between lake water sources (fresh versus saline) and their fluorescence/absorption characteristics. Results indicated significant differences regarding DOC concentration and a CDOM (254) between freshwater (6.68 mg C L-1 , 19.55 m-1) and saline lakes (27.4 mg C L-1 , 41.17 m-1). While humic-like (F 5) and fulvic-like (F 3) compounds contributed to CDOM fluorescence in all lake waters significantly, their contribution to total fluorescence intensity (F T) differed between saline and freshwater lakes. Significant negative relationships were also observed between lake altitude with either F 5 (R 2 =0.63, N=306) or F T (R 2 =0.64, N=306), suggesting that the abundance of humic-like materials in CDOM tends to decrease with increased in lakes altitude. In high-altitude lakes, strong solar irradiance and UV exposure may have induced photo-oxidation reactions resulting in decreased abundance of humic-like substances and the formation of low molecular weight compounds. These findings have important implications regarding our understanding of C dynamics in lacustrine systems and the contribution of these ecosystems to the global C cycle.

Characteristics and Source of Dissolved Organic Matter in Lake Hulun, A Large Shallow Eutrophic Steppe Lake in Northern China

“…In this study, the absorption coefficient of CDOM at 254 nm (α 254 , m −1 ) was used as a proxy for CDOM concentration. The value of α 254 was determined using the following equation [24]:…”

“…CDOM is part of the DOM and is involved in the absorption of UV and photosynthetically available radiation [29][30][31]. CDOM is a major component of DOM in water and plays a vital role in carbon cycling in inland water [24,32]. The CDOM concentration, represented by α 254 in the overlying water of Lake Hulun, ranged from 6.97 m −1 to 86.89 m −1 , and showed significant seasonal differences.…”

“…In addition, the DOM in their water bodies is prone to photodegradation given the strong light intensity and UV radiation [42], resulting in the lowest DOM concentration in the entire country. The ELR and YGR are also two distinctive lake regions in China that have highly intense human activity and serious eutrophication [24,41]. The DOM concentration in the ELR was lower than that in the YGR, and it is mainly related to factors such as the lake's characteristics, hydrodynamic conditions, and pollution sources.…”

“…The DOM concentrations in lakes of the MXR are higher than the other compared lakes in this paper, which is mainly due to climatic conditions, altitude, and lake conditions. The MXR is located in the high-latitude region of China, and lakes are mostly the last resting place of inland water systems [24]. At the same time, the lakes are concentrated, the lake areas are decreased, and the water is shallow because the evaporation is much greater than the excess supply.…”

CDOM Absorption Properties of Natural Water Bodies along Extreme Environmental Gradients

“…Conmy et al [29] found changes in the CDOM absorption spectral slope S 280−312 with salinity to be a result of mixing of CDOM originating from freshwater and marine humics together with photo-bleaching in coastal water. Song et al [34] discovered that the humic-like materials in CDOM tended to decrease with altitude in lakes.…”