上海近海水体悬浮泥沙浓度反演及营养化评价

Inversion of suspended sediment concentration and nutrient evaluation in Shanghai offshore waters

中文关键词:  悬浮泥沙  BP神经网络  Landsat-8/9OLI  富营养化

英文关键词:suspended sediment  BP neural network  Landsat-8/9 OLI  eutrophication

中文摘要:

      悬浮泥沙浓度是重要的水质监测参数之一，开展悬浮泥沙研究对上海近海水体环境保护具有重要意义。本文基于水文实测数据和Landsat-8/9OLI数据，利用BP神经网络建立了上海近海水体悬浮泥沙浓度反演模型，测试集均方根误差为16.12mg/L，平均相对误差为10.81%，决定系数达到0.9855，精度优于常用的悬浮泥沙经验反演算法。通过悬浮泥沙浓度、溶解氧浓度、叶绿素a浓度、无机氮浓度及活性磷酸盐浓度五种水质因子Spearman相关性分析，发现悬浮泥沙与其余四种水质因子有明显的负相关性。通过富营养化指数法分析了上海近海2022年4个月份的水体营养化分布，发现高悬浮泥沙浓度月份水体营养程度相对较低，悬浮泥沙对于水中营养物质具有吸附或沉降作用，悬浮泥沙与富营养化指数之间的Pearson系数空间分布表明悬浮泥沙可以抑制近海水体富营养化。

英文摘要:

      Suspended sediment concentration is a key water quality monitoring parameters, and the study of suspended sediment is crucial for the environmental protection of Shanghai offshore waters. In this study, an inversion model for suspended sediment concentration in Shanghai offshore waters was developed using a BP neural network, based on measured hydrological data and Landsat-8/9 OLI data. The model achieved a root-mean-square error of 16.12 mg/L, an average relative error of 10.81%, and a coefficient of determination of 0.985 5. outperforming commonly used empirical inversion algorithm for suspended sediment. Spearman correlation analysis was conducted on suspended sediment concentration, dissolved oxygen concentration, chlorophyll-a concentration, inorganic nitrogen concentration and active phosphate concentration. The results indicated that suspended sediment was negatively correlated with all four water quality factors. The eutrophication index method was applied to assess nutrient distribution in Shanghai′s offshore waters over four months in 2022. The findings revealed that in months with high suspended sediment concentration, nutrient levels were relatively low, suggesting that suspended sediment may have an adsorption or sedimentation effect on waterborne nutrients. The spatial distribution of the Pearson coefficient between suspended sediment concentration and the eutrophication index indicates that suspended sediment can inhibit eutrophication in offshore waters.