Abstract

The traditional field-based measurements of carbon dioxide (pCO2) for inland waters are a snapshot of the conditions on a particular site, which might not adequately represent the pCO2 variation of the entire lake. However, these field measurements can be used in the pCO2 remote sensing modeling and verification. By focusing on inland waters (including lakes, reservoirs, rivers, and streams), this paper reviews the temporal and spatial variability of pCO2 based on published data. The results indicate the significant daily and seasonal variations in pCO2 in lakes. Rivers and streams contain higher pCO2 than lakes and reservoirs in the same climatic zone, and tropical waters typically exhibit higher pCO2 than temperate, boreal, and arctic waters. Due to the temporal and spatial variations of pCO2, it can differ in different inland water types in the same space-time. The estimation of CO2 fluxes in global inland waters showed large uncertainties with a range of 1.40–3.28 Pg C y−1. This paper also reviews existing remote sensing models/algorithms used for estimating pCO2 in sea and coastal waters and presents some perspectives and challenges of pCO2 estimation in inland waters using remote sensing for future studies. To overcome the uncertainties of pCO2 and CO2 emissions from inland waters at the global scale, more reliable and universal pCO2 remote sensing models/algorithms will be needed for mapping the long-term and large-scale pCO2 variations for inland waters. The development of inverse models based on dissolved biogeochemical processes and the machine learning algorithm based on measurement data might be more applicable over longer periods and across larger spatial scales. In addition, it should be noted that the remote sensing-retrieved pCO2/the CO2 concentration values are the instantaneous values at the satellite transit time. A major technical challenge is in the methodology to transform the retrieved pCO2 values on time scales from instant to days/months, which will need further investigations. Understanding the interrelated control and influence processes closely related to pCO2 in the inland waters (including the biological activities, physical mixing, a thermodynamic process, and the air–water gas exchange) is the key to achieving remote sensing models/algorithms of pCO2 in inland waters. This review should be useful for a general understanding of the role of inland waters in the global carbon cycle.

Highlights

  • Recent studies have revealed the presence of four interrelated processes closely related to water surface pCO2, i.e., biological activities, physical mixing, a thermodynamic process, and the air–water gas exchange. In principle, understanding these control processes of pCO2 in the inland waters and unearthing the environmental variables linking to these processes, which can be derived from satellite data, are the key to successfully achieving remote sensing of pCO2 in inland waters

  • This paper reviewed the temporal and spatial variability of pCO2 in inland waters

  • This review summarized previous investigations on remote sensing of pCO2 in sea and coastal waters, which is essential to the accurate description of the spatial-temporal heterogeneity of sea-surface CO2 flux

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Summary

A Review of Quantifying pCO2 in Inland Waters with a Global

Zhidan Wen 1 , Yingxin Shang 1 , Lili Lyu 1 , Sijia Li 1 , Hui Tao 1 and Kaishan Song 1,2, *.

Introduction
Spatio-Temporal Variability of pCO2 in Inland Waters
The Current State of CO2 Fluxes in Inland Waters
Studies on Remote Sensing of pCO2
Remote Sensing Estimating pCO2 in Marine and Coastal Waters
Remote Sensing of pCO2 and CO2 Fluxes for Inland Waters
Challenges and Limitations of pCO2 Remote Sensing Algorithms
Findings
Conclusions
Full Text
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