Currently, with the acceleration of urbanization in China and the shortage of urban construction land, it is particularly important to objectively and scientifically evaluate the efficiency of urban construction land use. This paper takes Hunan Province as the research object, uses the three-stage DEA model to analyze, obtains the efficiency value except for environmental factors and random factors, and compares and analyzes the change of urban construction land use efficiency of 13 Prefecture-level city in Hunan Province in 2018. The research results indicate that the utilization efficiency of urban construction land in Hunan Province is good, and the resource allocation is relatively reasonable. However, some cities have redundant inputs or insufficient outputs, unreasonable resource allocation, and low urban scale efficiency. Based on the above conclusions, this article proposes suggestions to improve the efficiency of urban construction land use in Hunan Province from three aspects.

The sea area around Dajin Island in the Pearl River Estuary is the second-largest habitat in China for the Indo-Pacific humpback dolphin (Sousa Chinensis). However, the rapid economic development of this area brings potential threats to the aquatic ecology around Dajin Island. Real-time monitoring and evaluation of the ecological health of the sea area are urgent. In this study, band ratio and single-band inversion algorithms were performed to obtain Chlorophyll-a (Chl-a) and Suspended Sediment Concentration (SSC), relying on both Compact Airborne Spectrographic Imager (CASI) and Moderate resolution Imaging Spectrometer (MODIS) images. The CASI/Chl-a with high spatial resolution was adopted to assess the eutrophication status, while the dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) optical properties were used to derive the material composition and sources. The results suggest that the study area is under a low to medium eutrophication state with evenly distributed low Chl-a concentration. However, higher Chl-a is observed in the outer estuary with MODIS/Chl-a. The relatively high DOC concentration, especially in the north, where aquaculture is practiced, and near the estuary’s main axis, i.e., east Dajin Island, indicates that the eutrophication state might be underestimated using satellite chlorophyll alone. CDOM optical properties indicated that terrestrial materials are the DOC’s primary material sources, but the DOC derived from fishery aquaculture cannot be ignored. The low Chl-a concentration is likely due to the turbulent hydrodynamic regime caused by jet flow and reciprocating flow in this marine area. Comprehensive observation, including the assessment of different technological platforms, is suggested for the aquatic environment.

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