State of rare earth elements in the sediment and their bioaccumulation by mangroves: a case study in pristine islands of Indian Sundarban

State of rare earth elements in the sediment and their bioaccumulation by mangroves: a case study in pristine islands of Indian Sundarban

Sanjay K. Mandal1,2 & Raghab Ray3,4 & Aridane G. González3,5 & Vasileios Mavromatis6 & Oleg S. Pokrovsky6,7,8 & Tapan K. Jana1
Received: 9 August 2018 /Accepted: 10 January 2019
# Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract

The mangrove ecosystems are known to efficiently sequester trace metals both in sediments and plant biomass. However, less is known about the chemistry of rare earth elements (REE) in the coastal environments, especially in the world’s largest mangrove province, the Sundarban. Here, the concentration of REE in the sediment and plant organs of eight dominant mangrove species (mainly Avicennia sp.) in the Indian Sundarban was measured to assess REE sources, distribution, and bioaccumulation state. Results revealed that light REE (LREE) were more concentrated than
the heavy REE (HREE) (128–144 mg kg−1 and 12–15 mg kg−1, respectively) in the mangrove sediments, with a relatively weak positive europium anomaly (Eu/Eu* = 1.03–1.14) with respect to North American shale composite. The primary source of REE was most likely linked to aluminosilicate weathering of crustal materials, and the resultant increase in LREE in the detritus. Vertical distribution of REE in one of the long cores from Lothian Island was altered by mangrove root activity and dependent on various physicochemical properties in the sediment (e.g., Eh, pH, organic carbon, and phosphate). REE uptake by plants was higher in the below-ground parts than in the above-ground plant tissues (root = 3.3 mg kg−1, leaf + wood = 1.7 mg kg−1); however, their total concentration was much lower than in the sediment (149.5 mg kg−1). Species-specific variability in bioaccumulation factor and translocation factor was observed indicating different REE partitioning and varying degree of mangrove uptake efficiency. Total REE stock in plant (above + live below ground) was estimated to be 168 g ha−1 with LREE contributing ~ 90% of the stock. This study highlighted the efficiency of using REE as a biological proxy in determining the degree of bioaccumulation within the mangrove environment.

Keywords Rare earth elements (REE) . Bioaccumulation . Mangrove . Sundarban
Responsible editor: Philippe Garrigues
* Raghab Ray raghab.ray@gmail.com; raghab.ray@aori.u-tokyo.ac.jp
1 Department of Marine Science, Calcutta University, Kolkata 70019, India
2 Department of Chemistry, Sundarban HaziDesarat College, South 24 Parganas, Pathankhali 743611, India
3 LEMAR (Laboratoire des Sciences de l’Environnement Marin), UMR 6539, (CNRS-UBO-IRD- IFREMER), 29280 Plouzané, France
4 Department of Chemical Oceanography, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8564, Japan
5 Instituto de Oceanografía y Cambio Global, IOCAG, Universidad de Las Palmas de Gran Canaria, ULPGC, 35017 Las Palmas de Gran Canaria, Spain
6 GET (Géosciences Environnement Toulouse) UMR 5563 CNRS, 31400 Toulouse, France
7 BIO-GEO-CLIM Laboratory, Tomsk State University, Tomsk, Russia 634050
8 N. Laverov Federal Center for Integrated Arctic Research, IEPS, Russian Academy of Sciences, Arkhangelsk, Russia 163000
Environmental Science and Pollution Researchhttps://doi.org/10.1007/s11356-019-04222-1