| As an important natural resource,economic resource and social resource for urban development,urban water bodies are an indispensable part of the urban ecosystem.In recent years,with the acceleration of urbanization,river pollution has become more and more serious,and black and odorous water bodies have occurred frequently.At present,there have been many research achievements on the formation mechanism,evaluation methods,and ecological restoration of black and odorous water bodies,but the research on remote sensing identification and monitoring is still not mature enough.Based on the water quality monitoring data of key remediation creeks in Guangzhou from 2016 to 2019,this study used the principal component analysis method to calculate the weights of water quality indicators and constructed a new urban black and odorous water body evaluation model—Black and Odorous Water Quality Index（B-OWQI）;using the GF-2 satellite images,the water quality indicator concentration in central districts of Guangzhou was retrieved and mapped by remote sensing;the retrieved water quality indicators were applied to the B-OWQI model to identify and classify the black and odorous water bodies,and the accuracy of the identification results was evaluated based on the measured data of ground stations;finally,the pollution source traceability analysis of black and odorous water bodies was carried out from some factors such as industrial pollution,domestic pollution,and agricultural pollution.The main results show:（1）The principal component analysis was carried out on the indicators such as dissolved oxygen（DO）,ammonia nitrogen（NH3-N）,total phosphorus（TP）,and chemical oxygen demand（COD）in the water quality monitoring data of key remediation creeks in Guangzhou to calculate their weights.A new urban black and odorous water body evaluation model B-OWQI was proposed.The accuracy of the evaluation results of the B-OWQI model was analyzed using the measured data from ground stations,and the recognition accuracy rate reached 81.87%.The correlation analysis between the evaluation results of the B-OWQI model and the comprehensive water quality identification index（WQII）method and the creek water quality index（CWQI）was carried out.It is found that the evaluation results of the three models are well correlated.Compared with WQII and CWQI,the newly proposed B-OWQI is more objective and more suitable for the evaluation of black and odorous water bodies in Guangzhou.（2）The concentrations of DO,NH3-N,TP and COD were retrieved based on GF-2satellite images in central districts of Guangzhou,and the accuracy of the inversion results of water quality indicators was verified using quasi-synchronous measured data of ground stations with satellite images;further,the inversion results of the water quality indicators were applied to the B-OWQI model to realize the identification and grading mapping of black and odorous water bodies in Guangzhou,and the verification samples of ground site data were used to verify the accuracy of the remote sensing recognition of black and odorous water bodies using the confusion matrix method.The results show that the inversion errors of water quality indicators are all less than 35%,which indicates that the remote sensing inversion results can be used for large-scale water quality inversion and evaluation of black and odorous water bodies;the classification accuracy of B-OWQI model applied to GF-2 image identification of black and odorous water bodies is better than 70%.The research results can provide the water environment department with spatiotemporal continuous pollution status of black and odorous water bodies and provide effective support for the treatment and prevention of black and odorous water bodies.（3）Using the remote sensing recognition results of black and odorous water bodies to analyze the spatial distribution of black and odorous water bodies in central districts of Guangzhou,it is found that black and odorous water bodies are mainly distributed in Huangpu District and Baiyun District,while the water quality in other districts is relatively good.Through the pollution source traceability analysis of key black and odorous water bodies in Huangpu District and Baiyun District,it is found that the southern rivers of Huangpu District mainly flow through urban land and there are many polluting enterprises around the rivers,indicating that the water quality is mainly polluted by industrial wastewater and domestic sewage;the northern rivers of Huangpu District mainly flow through cultivated land and there are many rural settlements nearby,indicating that the pollution sources are mainly domestic sewage and agricultural sewage.Some sections of the Liuxi River in Baiyun District are polluted by domestic sewage,and the water quality is slightly black and odorous;the creeks in the east of Liuxi River mainly flow through cultivated land and urban land and there are many polluting enterprises nearby,indicating the creeks are affected by industrial wastewater,domestic sewage and agricultural sewage,resulting in black and odorous water quality. |
