A systematic examination of the relationships between CDOM and DOC in inland waters in China
Kaishan Song1, Ying Zhao1,2, Zhidan Wen1, Chong Fang1,2, and Yingxin Shang11Northeast Institute of Geography and Agroecology, CAS, Changchun, 130102, China 2University of Chinese Academy of Sciences, Beijing 10 0049, China
Received: 25 Mar 2017 – Accepted for review: 03 Apr 2017 – Discussion started: 04 Apr 2017
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 the significant relationship lays the foundation for the estimation of DOC using remotely sensed imagery data. An algorithm has been developed to retrieve DOC via CDOM absorption (aCDOM) at 275 and 295 nm for coastal waters, but it is still unclear for the relationship between DOC and aCDOM in other types of waters. The current study examined the samples from freshwater lakes, saline lakes, rivers and streams, urban water bodies, and ice-covered lakes in China. The regression model slopes for DOC versus aCDOM(275) ranged from extreme low 0.33 (highly saline lakes) to 1.03 (urban waters) and 3.13 (river waters). The low values were observed in saline lake waters and waters from semi-arid or arid regions where strong photo-bleaching is expected due to thin ozone layers, 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 massive organic matter was transported from catchment to waters. The study also demonstrated that stronger relationships between CDOM and DOC were revealed when aCDOM(275) were sorted by the ratio of aCDOM(250) to aCDOM(365), which is a tracer for the CDOM absorption with respect to its composition, and the determination of coefficient of the regression models ranged from 0.78 to 0.99 for different groups of waters. Our results indicated the relationships between CDOM and DOC are variable for different inland waters, and therefore remote sensing models for DOC estimation through linking with CDOM absorption need to be tailored according to water types.
Song, K., Zhao, Y., Wen, Z., Fang, C., and Shang, Y.: A systematic examination of the relationships between CDOM and DOC in inland waters in China, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2017-179, in review, 2017.