ABSTRACT
Due to severe disturbances caused by rapid urbanization and industrialization, river ecosystems have evolved into complex natural-social composite ecosystems. At present, there is no unified evaluation method for the effect of river restoration in China. The existing research fails to fully integrate the "natural-social" characteristics of rivers, and pays less attention to the river section scale, which is not conducive to the development of accurate pollution control work. In this paper, we first put forward the division method of river section type which conforms to the "nature-society" dual attribute characteristics of the river, and divides the river section into "ecological/service/dual" functional "urban/rural" river section. Then a method for evaluating the restoration effect of different river sections based on index weight optimization was proposed. Based on the type of river section, the weights of 17 indexes were optimized, and the common evaluation method of restoration effect-multi-index evaluation method was improved. In addition, the application and verification of the established method were carried out on the main stream of Qingyi River and its typical tributaries. The evaluation results show that only the restoration effect of Baling River decreased from average in 2019 to acceptable in 2021, and ΔH (the change of the mean score of the target factor after repair) decreased from 15.6% to 6.2%. It was found that for the river sections where the repair effect cannot be maintained stably (such as Baling River), the previous methods paid more attention to the overall effect and easily ignored the specific problems. The improved method can identify problems more easily and facilitate timely post-maintenance. To further optimize the repair effect of Qingyi River, it is suggested that the restoration effect should be strengthened from the aspects of pollution source control, water quality improvement, aquatic restoration, continuous monitoring and evaluation. The evaluation results can provide a reference for the design, operation, and maintenance of restoration projects in small and medium-sized rivers.
ABSTRACT
Black-odorous water, which exists widely in rural areas of China, affects the living environments of residents and causes a loss of ecosystem functions, and improper treatment may even cause secondary pollution. Moreover, the transformation relationships among the components of humus in the sediments of black-odorous water are largely unknown. Therefore, it is necessary to select appropriate methods for treating black-odorous water in rural areas and to understand the characteristics of humus in sediment during the treatment process. In this study, the use of aeration in treating black-odorous water and interstitial water in rural areas was studied and the effects of different treatment methods on the contents and spectral characteristics of humus components in sediments were explored. It was found that the quality of the treated water improved from severe black-odorous to nonblack-odorous, the colour of the sediment changed from black to greyish-brown to turquoise, and the odour changed from strong to weak. The removal rates of ammonia nitrogen, total nitrogen, total phosphorus, and chemical oxygen demand in the sediment aeration group reached more than 50% in the upper water, and more than 70% in the interstitial water. After treatment, the content of fulvic acid, the main black substance in sediment, decreased by 0.36-1.58 g/kg, and the molecular structure of the humus was simplified.
