Statistical model development and estimation of suspended particulate matter concentrations with Landsat 8 OLI images of Dongting Lake, China

Abstract

Suspended particulate matter (SPM) is a dominant water constituent of case-II waters, and SPM concentration (CSPM) is a key parameter describing water quality. This study, using Landsat 8 Operational Land Imager (OLI) images, aimed to develop the CSPM retrieval models and further to estimate the CSPM values of Dongting Lake. One Landsat 8 OLI image and 53 CSPM measurements were employed to calibrate Landsat 8-based CSPM retrieval models. The CSPM values derived from coincident Landsat 8 OLI and Moderate Resolution Imaging Spectroradiometer (MODIS) images were compared to validate calibrated Landsat 8-based CSPM models. After the best stable Landsat 8-based CSPM retrieval model was further validated using an independent Landsat 8 OLI image and its coincident CSPM measurements, it was applied to four Landsat 8 OLI images to retrieve the CSPM values in the South and East Dongting Lake. Model calibration results showed that two exponential models of the red band explained 61% (estimated standard error (SE) = 7.96 mg l–1) and 67% (SE = 6.79 mg l–1) of the variation of CSPM; two exponential models of the red:panchromatic band ratio obtained 81% (SE = 5.48 mg l–1) and 77% (SE = 4.96 mg l–1) fitting accuracy; and four exponential and quadratic models of the infrared band explained 72–83% of the variation of CSPM (SE = 5.18–5.52 mg l–1). By comparing the MODIS- and Landsat 8-based CSPM values, an exponential model of the Landsat 8 OLI red band (CSPM = 1.1034 × exp(23.61 × R)) obtained the best consistent CSPM estimations with the MODIS-based model (r = 0.98, p < 0.01), and its further validation result using an independent Landsat 8 OLI image showed a significantly strong correlation between the measured and estimated CSPM values at a significance level of 0.05 (r = 0.91, p < 0.05). The CSPM spatiotemporal distribution derived from four Landsat 8 images revealed a clear spatial distribution pattern of CSPM in the South and East Dongting Lake, which was caused by natural and anthropogenic factors together. This study confirmed the potential of Landsat 8 OLI images in retrieving CSPM and provided a foundation for retrieving the spatial distribution of CSPM accurately from this new data source in Dongting Lake.