Duc Huy Dang, Zhirou Zhang, Wei Wang, Oursel B., Juillot Farid, Dupouy Cécile, Lemonnier H., Mounier S. (2021). Tropical mangrove forests as a source of dissolved rare earth elements and yttrium to the ocean. Chemical Geology, 576, 120278 [12 p.]. ISSN 0009-2541.
Titre du document
Tropical mangrove forests as a source of dissolved rare earth elements and yttrium to the ocean
Chemical Geology, 2021,
576, 120278 [12 p.] ISSN 0009-2541
Rare earth elements (REEs) and Y are commonly used as geochemical proxies for water chemistry, history of the continental crust and provenance studies. At the continent-ocean interface, the estuarine geochemistry of REEs is commonly considered to be driven by a largescale removal. Consequently, the river-borne flux of dissolved REEs to the marine budget is assumed as a minor fraction. Here, we report a significant release of dissolved REEs, together with a fractionation between light, heavy REEs and Y, in the tropical mangrove estuaries of New Caledonia. These observations were associated with internal recycling within the redox-dynamic mangrove system. The possible contribution of groundwater can be ruled out based on water stable isotopes. These findings imply that tropical mangrove estuaries act as a sizeable source of REEs and Y to the ocean rather than as a buffer zone. We extrapolated our data toward global dissolved fluxes of REEs and Y through the mangroves. This preliminary calculation suggests that the mangrove system supplies 2.6-5% of global river-borne dissolved Nd, a REE with the most comprehensive mass balance. Therefore, oceanic mass balance budget models may need to consider this atypical system as an input to balance the global distribution of REEs and Y.
