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<p>Dissolved oxygen (DO) is a crucial indicator of water body self-purification capacity and ecosystem health. The North Mainstream of the Dongjiang River (NMDR) features a dense network of tributaries, where both human activities and natural factors impact DO levels. This study employed field measurements to identify key drivers of DO variability and selected dominant factors that can be estimated from remote sensing data, including thermal infrared band indicating temperature and visible-NIR bands sensitive to water quality parameters. Band combination was then proposed to represent relative concentrations of chlorophyll (Chl), suspended particulate matter (SPM), and organic pollutant matter (OPM). By synergistically integrating multi-spectral satellite images and in situ site measurement, our algorithm was implemented, providing a mechanistic framework that integrates physical principles with remote sensing mechanism and DO dynamics. Upon station verification, the <i>R</i><sup>2</sup> between remotely sensed DO and measured DO was 0.73 with an <i>RMSE</i> of 0.50 mg/L when thermal infrared image was included. The <i>R</i><sup>2</sup> substantially reduced with an <i>RMSE</i> of 0.71 mg/L when using solely the visible-NIR bands. The results revealed a distinct seasonal pattern, with lower DO levels during summer and autumn and higher levels during winter and spring, primarily driven by temperature fluctuations. Spatially, the upstream DO is generally higher than downstream, with mainstream DO concentration being notably higher than those in some tributaries. Favorable factors contributing to these variations included the influx of high-DO water from the Dongjiang and Zengjiang rivers, while unfavorable factors included wastewater discharge along the riverbank, shipping activities, and tidal flow. Our study underscores the need to consider both natural and human-induced factors in assessing river health. By integrating remote sensing with site measurements, this research enhances our understanding of DO dynamics in NMDR, supporting its effective management and conservation.</p>

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Assessing dissolved oxygen dynamics in the North Mainstream of the Dongjiang River, China using remote sensing and field measurements

  • 期刊论文

  • 发表日期：

    2025年5月31日

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  • Youbin Feng,
  • Yingqing He

摘要

Dissolved oxygen (DO) is a crucial indicator of water body self-purification capacity and ecosystem health. The North Mainstream of the Dongjiang River (NMDR) features a dense network of tributaries, where both human activities and natural factors impact DO levels. This study employed field measurements to identify key drivers of DO variability and selected dominant factors that can be estimated from remote sensing data, including thermal infrared band indicating temperature and visible-NIR bands sensitive to water quality parameters. Band combination was then proposed to represent relative concentrations of chlorophyll (Chl), suspended particulate matter (SPM), and organic pollutant matter (OPM). By synergistically integrating multi-spectral satellite images and in situ site measurement, our algorithm was implemented, providing a mechanistic framework that integrates physical principles with remote sensing mechanism and DO dynamics. Upon station verification, the R2 between remotely sensed DO and measured DO was 0.73 with an RMSE of 0.50 mg/L when thermal infrared image was included. The R2 substantially reduced with an RMSE of 0.71 mg/L when using solely the visible-NIR bands. The results revealed a distinct seasonal pattern, with lower DO levels during summer and autumn and higher levels during winter and spring, primarily driven by temperature fluctuations. Spatially, the upstream DO is generally higher than downstream, with mainstream DO concentration being notably higher than those in some tributaries. Favorable factors contributing to these variations included the influx of high-DO water from the Dongjiang and Zengjiang rivers, while unfavorable factors included wastewater discharge along the riverbank, shipping activities, and tidal flow. Our study underscores the need to consider both natural and human-induced factors in assessing river health. By integrating remote sensing with site measurements, this research enhances our understanding of DO dynamics in NMDR, supporting its effective management and conservation.