Abstract: Coastal tidal flat is an important ecological resource of coastal cities, the protection and restoration of which are important for its ecological function. In this study, we measured the mercury release flux of forest land and forest edge bare flat with an improved dynamic flux box system and Tekran 2537B mercury analyzer in the restored Kandelia candel plantation in Haicang Bay, Fujian Province, during the daily low and flat tide period in summer and winter from 2018 to 2019. The results showed that the concentrations of atmospheric mercury and surface sediment mercury in the plots were at low levels. The tidal flat/atmospheric mercury flux was generally positive. The release of mercury in the daytime was more obvious than that at night. The release intensity in summer was greater than that in winter. Compared with the bare flat, forest land showed a significant inhibitory effect on mercury release from tidal flat to the atmosphere. Temperature, light, wind speed, topsoil temperature, and atmospheric mercury concentration were positively correlated with mercury flux. The influencing factors of mercury flux could be classified into two categories: atmospheric factor and ground surface factor. The mercury flux prediction models of forest land and bare flat were obtained by regression analysis. By comparing the regression coefficients of both models, it was found that the impact capacity of atmospheric factor on mercury flux was significantly inhibited by forest. Our results confirmed the inhibition ability and control factors of mangrove to mercury release from the tidal flat to the atmosphere, and provide a scientific basis for assessing the ecological value of mangrove replanting on bare flat in coastal zone in terms of mercury storage.

Key words: mercury release flux, Kandelia candel plantation, urban littoral beach, factor analysis.