Simultaneous inversion of concentrations of POC and its endmembers in lakes: A novel remote sensing strategy

Jie Xu; Yunmei Li; Heng Lyu; Shaohua Lei; Meng Mu; Shun Bi; Jiafeng Xu; Xiaoguang Xu; Song Miao; Lingling Li; Xingcheng Yan

doi:10.1016/j.scitotenv.2021.145249

Simultaneous inversion of concentrations of POC and its endmembers in lakes: A novel remote sensing strategy

Sci Total Environ. 2021 May 20:770:145249. doi: 10.1016/j.scitotenv.2021.145249. Epub 2021 Jan 20.

Authors

Jie Xu¹, Yunmei Li², Heng Lyu³, Shaohua Lei¹, Meng Mu¹, Shun Bi¹, Jiafeng Xu¹, Xiaoguang Xu⁴, Song Miao¹, Lingling Li¹, Xingcheng Yan⁵

Affiliations

¹ Key Laboratory of Virtual Geographic Environment of Education Ministry, Nanjing Normal University, Nanjing 210023, China.
² Key Laboratory of Virtual Geographic Environment of Education Ministry, Nanjing Normal University, Nanjing 210023, China; Jiangsu Center for Collaboration Invocation in Geographical Information Resource Development and Application, Nanjing 210023, China. Electronic address: yunmei2009@gmail.com.
³ Key Laboratory of Virtual Geographic Environment of Education Ministry, Nanjing Normal University, Nanjing 210023, China; Jiangsu Center for Collaboration Invocation in Geographical Information Resource Development and Application, Nanjing 210023, China.
⁴ School of Environment, Nanjing Normal University, Nanjing 210023, China.
⁵ UMR 7619 METIS, Sorbonne University, Paris 75005, France.

PMID: 33508668
DOI: 10.1016/j.scitotenv.2021.145249

Abstract

Data on the concentration of particulate organic carbon (POC) and its endmembers provide a basis for the characterisation of lake biogeochemical cycles. Here, a novel remote sensing strategy (the SC_POC algorithm) was developed to determine total POC concentrations, as well as terrestrial and endogenous POC concentrations in lakes. This strategy provides a successful example for the combination of isotope tracer and remote sensing technology. First, we obtained the terrestrial and endogenous POC concentration at the sampling point based on isotope tracing technology. Afterwards, we established a relationship between the phytoplankton absorption coefficient and the endogenous POC concentration (C_end), and applied a semi-analytical algorithm to invert the C_end value. Finally, the POC source ratio model and C_end value were combined to obtain the POC concentration (C_POC) and terrestrial POC (C_ter). The results of synchronisation verification based on ocean and land colour instrument (OLCI) images show that the SC_POC algorithm has high C_end, C_ter, and C_POC inversion accuracy, with MAPE values of 26.07%, 30.43%, and 42.28%, respectively. In fact, the SC_POC algorithm not only improved the accuracy of lake POC mapping, but also fills the gap of optical retrieval of POC endmember concentrations. Additionally, data from the OLCI images indicated that the studied lakes were dominated by external POC. However, because of the greater contribution of algal blooms to POC, this dominant advantage weakens in summer, although the terrestrial organic carbon carried by rainfall runoff also affects lake POC composition. Different POC sources have different ecological roles in lakes, and the superior POC end-element estimation capability of the SC_POC algorithm can not only be used as a supplement to traditional tracing methods, but also provides accurate spatial data for lake management.

Keywords: Particulate organic carbon; Remote sensing; Source tracer; Stable isotope.