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Building urban parks is one of the important ways to alleviate the Urban Heat Island Effect, and the cold island effect is a commonly used indicator to characterize the cooling effect of urban parks on surrounding areas. This study takes the Olympic Park in Beijing as an example and combines remote sensing data with measured data from meteorological stations to propose a new method for evaluating the urban cold island effect based on the superposition of multiple remote sensing images. The research results show that: The magnitude of PCI(Park Cold Island)values has a highly significant correlation with the highest temperature of the day, and the two show a linear correlation. The higher the temperature, the greater the PCI; From 2013 to 2021, the difference between the highest temperature and the lowest temperature in the study area is 23 times, and the difference between the maximum and minimum PCI value is 19 times. The PCI mix assessment method can better contain the extreme value, reduce the instability of temperature with seasonal changes and the impact of temperature variation differences between years, and reduce the contingency of assessment research; This new method is systematic, continuous, and statistically significant. The method proposed in this study for evaluating the urban cold island effect based on multi-phase image overlay can provide guidance for the future construction of urban parks and open up new ideas for evaluating the cooling effect of urban parks. • A new method has been proposed to describe the cold island effect of urban parks. • Research on the joint application of remote sensing and ecological index data. • Reflect the intensity of urban park cold island effect more continuously and objectively. • Compare the causes and effects of new methods and traditional methods on the results. [ABSTRACT FROM AUTHOR]

Fluorescence spectroscopy and UV-visible absorption spectroscopy were applied and multiple related parameters were analyzed to study both horizontal and vertical distributions of dissolved organic matters (DOM) in the sediment of the Taihu Lake, to explore their spectral characteristics, possible sources, influencing factors, and environmental implications. And the results showed that com- positions of sediment DOM varied between different lake areas and between different depths. Horizontally, sediment DOM in the Zhushan Bay contained more complex macromolecule substances and humus. This lake area is impacted by multiple DOM sources such as land-based sources and biological sources. In contrast, sediment DOM in the east part of the lake was less complex, and dominated by protein-like substances, indicating that this part is less impacted by land-based input than in the Zhushan Bay. Vertically, DOM compositions of the Zhushan Bay sediment exhibited a declining complexity with the depth, and DOM of the river sediment presented a similar trend, which implies that the degradation of DOM is more sufficient at the deeper sediment. Comparing the spectra of sediment DOM at the same depth, it was found that DOM composition of river sediments was more complex than that of lake sediments, which indicates that the DOM of river sediments was less degraded than that of lake sediment at the same depth, and was impacted by multiple sources. [ABSTRACT FROM AUTHOR]