Li Jian-Hong, Huang Chang-Chun, Zha Yong, Wang Chuan, Shang Na-Na, Hao Wei-Yue
School of Geography, Nanjing Normal University, Nanjing 210023, China.
Key Laboratory of Karst Dynamics, Ministry of Natural Resources/Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
Huan Jing Ke Xue. 2021 Nov 8;42(11):5239-5249. doi: 10.13227/j.hjkx.202103245.
Total suspended matter(TSM) is an important parameter that describes optical characteristics and water pollution level. Remote sensing was used to obtain suspended matter concentrations in the planar water body, which can monitor and analyze the reliability of turbidity and pollution levels. In this study, a semi-empirical model of suspended matter along the Yangtze River mainstream(from Chongqing to Shanghai) was constructed based on the field measured hyperspectral data and suspended matter concentration and its components, with reference to MODIS(1-4 band), Landsat 8(1-5 band), Sentinel 2(2-6 band), HJ-B1(1-4 band), and other commonly used band ranges. The results show that:① Turbidity and TSM of the Yangtze River mainstream increased from Chongqing to Shanghai during the dry season, whereas the proportion of OSM to TSM(OSM/TSM) decreased from Chongqing to Shanghai. ② The spectral properties of chlorophyll- were not obvious; however, it showed a bimodal spectral characteristic of suspended matter concentration. Due to the low concentration of suspended matter in the water(<114.68 mg·L), the first peak value was significantly higher than the second peak. However, peak reflection and position had an obvious "red shift" phenomenon in the direction of the wavelength. ③ The reflectance values of the Yangtze River mainstream were most sensitive to the concentration of suspended matter in the 600-710 nm and 475-550 nm bands. Most of these fall in the green and red band of MODI, Landsat 8, Sentinel 2, and HJ-1B satellites. Therefore, the commonly used satellites have a band setting to detect the inversion of turbidity degree index of the Yangtze River main stream water body. The Sentinel 2 satellite band is most suitable for the inversion of suspended matter concentration in the Yangtze River mainstream. The mean absolute percentage error(MAPE) and root mean square error(RMSE) of the optimal exponential model were 10.23 mg·L and 23%, respectively.
总悬浮颗粒物（TSM）是描述光学特征和水污染程度的一个重要参数。利用遥感技术获取平面水体中的悬浮物质浓度，可对浊度和污染程度的可靠性进行监测与分析。本研究基于实测的高光谱数据以及悬浮物质浓度及其组分，参照中分辨率成像光谱仪（MODIS）（1 - 4波段）、陆地卫星8号（Landsat 8）（1 - 5波段）、哨兵2号（Sentinel 2）（2 - 6波段）、环境减灾卫星-1B（HJ - B1）（1 - 4波段）等常用波段范围，构建了长江干流（从重庆到上海）悬浮物质的半经验模型。结果表明：①长江干流枯水期浊度和TSM从重庆到上海呈上升趋势，而有机悬浮物质（OSM）占TSM的比例（OSM/TSM）从重庆到上海呈下降趋势。②叶绿素的光谱特性不明显；然而，其呈现出悬浮物质浓度的双峰光谱特征。由于水体中悬浮物质浓度较低（<114.68 mg·L），第一个峰值明显高于第二个峰值。不过，峰值反射和位置在波长方向上有明显的“红移”现象。③长江干流的反射率值在600 - 710 nm和475 - 550 nm波段对悬浮物质浓度最为敏感。其中大部分落在MODI、Landsat 8、Sentinel 2和HJ - 1B卫星的绿光和红光波段。因此，常用卫星的波段设置可用于检测长江干流水体浊度指数的反演。哨兵2号卫星波段最适合长江干流悬浮物质浓度的反演。最优指数模型的平均绝对百分比误差（MAPE）和均方根误差（RMSE）分别为10.23 mg·L和23%。
