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<p>Chromophoric dissolved organic matter (CDOM) plays a crucial role in regional carbon cycling, aquatic ecological stability and photochemical reactions. Variations in CDOM concentration and composition directly influence and indicate water quality. However, monitoring CDOM in lakes remains challenging under the harsh conditions of the Qinghai-Xizang Plateau (QXP), and its multi-scale dynamics across lake types are still poorly understood. In this study, we produced monthly 10-m CDOM maps for the saline lake (Qinghai Lake, QHL) and the freshwater lake (Keluke Lake, KLK) during the ice-free seasons from 2017 to 2024 using Sentinel-2, by averaging all valid within-month CDOM retrievals. Trend analysis and continuous wavelet transform (CWT) examined CDOM spatiotemporal dynamics and periodicity, while wavelet coherency (WTC) and multivariate linear models assessed environmental influences, including precipitation (<i>P</i>), air temperature (<i>T</i><sub>a</sub>), wind speed (WS), snow cover area (SC), normalized difference vegetation index (NDVI), lake mixed-layer depth and temperature (LMLD and LMLT), and lake area. Results show that the mean CDOM in QHL was 1.08/m, with 70.44% of the area showing a decline, whereas KLK averaged 1.93/m, with 88.33% showing an increase. CWT analysis of CDOM indicates that both lakes have a major cycle of approximately 21 months, but the KLK cycle signal is relatively weak. In addition, the QHL also shows a distinct seasonal oscillation (7 months). In QHL, WTC indicated sustained coherence between CDOM and all factors except lake area at 6–12-month time scales; in KLK, sustained coherence was mainly observed with <i>T</i><sub>a</sub>, NDVI, LMLT, and LMLD, although the coherence bands and cycles varied over time. At short time scales (&lt;5 months), CDOM in KLK showed stronger coherence with environmental fluctuations than in QHL. Temperature and vegetation explained over 60% of CDOM variance in both lakes. These findings provide important references for water quality management and environmental protection of plateau lakes under environmental change scenarios.</p>

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Revealing multiscale dynamics and drivers of chromophoric dissolved organic matter (CDOM) in lakes on the Qinghai-Xizang Plateau using Sentinel-2

  • 期刊论文

  • 发表日期：

    2026年6月22日

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  • Chuanli Jiang,
  • Yujun Ma,
  • Chenxiaoyu Han,
  • Wanting Chen

摘要

Chromophoric dissolved organic matter (CDOM) plays a crucial role in regional carbon cycling, aquatic ecological stability and photochemical reactions. Variations in CDOM concentration and composition directly influence and indicate water quality. However, monitoring CDOM in lakes remains challenging under the harsh conditions of the Qinghai-Xizang Plateau (QXP), and its multi-scale dynamics across lake types are still poorly understood. In this study, we produced monthly 10-m CDOM maps for the saline lake (Qinghai Lake, QHL) and the freshwater lake (Keluke Lake, KLK) during the ice-free seasons from 2017 to 2024 using Sentinel-2, by averaging all valid within-month CDOM retrievals. Trend analysis and continuous wavelet transform (CWT) examined CDOM spatiotemporal dynamics and periodicity, while wavelet coherency (WTC) and multivariate linear models assessed environmental influences, including precipitation (P), air temperature (Ta), wind speed (WS), snow cover area (SC), normalized difference vegetation index (NDVI), lake mixed-layer depth and temperature (LMLD and LMLT), and lake area. Results show that the mean CDOM in QHL was 1.08/m, with 70.44% of the area showing a decline, whereas KLK averaged 1.93/m, with 88.33% showing an increase. CWT analysis of CDOM indicates that both lakes have a major cycle of approximately 21 months, but the KLK cycle signal is relatively weak. In addition, the QHL also shows a distinct seasonal oscillation (7 months). In QHL, WTC indicated sustained coherence between CDOM and all factors except lake area at 6–12-month time scales; in KLK, sustained coherence was mainly observed with Ta, NDVI, LMLT, and LMLD, although the coherence bands and cycles varied over time. At short time scales (<5 months), CDOM in KLK showed stronger coherence with environmental fluctuations than in QHL. Temperature and vegetation explained over 60% of CDOM variance in both lakes. These findings provide important references for water quality management and environmental protection of plateau lakes under environmental change scenarios.