A systematic examination of the relationships between CDOM and DOC in inland waters in China

Kaishan Song,Chong Fang,Yingxin Shang,Ying Zhao,Zhidan Wen

doi:10.5194/hess-21-5127-2017

Abstract

Abstract. Chromophoric dissolved organic matter (CDOM) plays a vital role in the biogeochemical cycle in aquatic ecosystems. The relationship between CDOM and dissolved organic carbon (DOC) has been investigated, and this significant relationship lays the foundation for the estimation of DOC using remotely sensed imagery data. The current study examined samples from freshwater lakes, saline lakes, rivers and streams, urban water bodies, and ice-covered lakes in China for tracking the variation of the relationships between DOC and CDOM. The regression model slopes for DOC vs. aCDOM (275) ranged from extremely low 0.33 (highly saline lakes) to 1.03 (urban waters) and 3.01 (river waters). The low values were observed in saline lake waters and waters from semi-arid or arid regions, where strong photobleaching is expected due to less cloud cover, longer water residence time, and daylight hours. In contrast, high values were found in waters developed in wetlands or forest in Northeast China, where more organic matter was transported from catchment to waters. The study also demonstrated that closer relationships between CDOM and DOC were revealed when aCDOM (275) were sorted by the ratio of aCDOM(250)∕aCDOM (365), which is a measure for the CDOM absorption with respect to its composition, and the determination of coefficient of the regression models ranged from 0.79 to 0.98 for different groups of waters. Our results indicate the relationships between CDOM and DOC are variable for different inland waters; thus, models for DOC estimation through linking with CDOM absorption need to be tailored according to water types.

Highlights

Inland waters play a disproportionate role in global carbon cycling with respect to carbon transportation, transformation, and carbon storage (Tranvik et al, 2009; Raymond et al, 2013; Verpoorter et al, 2014; Yang et al, 2015)
Researchers have found that remote sensing might provide a promising tool for quantification of dissolved organic carbon (DOC) in inland waters on a large scale through linking DOC with chromophoric dissolved organic matter (CDOM), for inland waters situated in remote areas with little accessibility (Tranvik et al, 2009; Kutser et al, 2015; Brezonik et al, 2015)
Total nitrogen (TN) and Total phosphorus (TP) concentrations were very high in fresh lakes, saline lakes, and in urban water bodies (Table 1)

Summary

Introduction

Inland waters play a disproportionate role in global carbon cycling with respect to carbon transportation, transformation, and carbon storage (Tranvik et al, 2009; Raymond et al, 2013; Verpoorter et al, 2014; Yang et al, 2015). The amount of dissolved organic carbon (DOC) stored in the inland waters is still unclear or the uncertainty is still needed to be evaluated (Tranvik et al, 2009). Researchers have found that remote sensing might provide a promising tool for quantification of DOC in inland waters on a large scale through linking DOC with chromophoric dissolved organic matter (CDOM), for inland waters situated in remote areas with little accessibility (Tranvik et al, 2009; Kutser et al, 2015; Brezonik et al, 2015). The autochthonous CDOM essentially originates from algae and macrophytes, and mainly consists of various compounds of low molecular weights

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Conclusion