Thallium distribution in an estuary affected by acid mine drainage (AMD): The Ría de Huelva estuary (SW Spain)

Supplementary data to this article can be found online at https://doi. org/10.1016/j.envpol.2022.119448.

This work was supported by the Spanish Ministry of Economy and Competitiveness under the research projects CAPOTE (MINECO; CGL 2017-86050-R) and TRAMPA (MINECO; PID 2020-119196RB-C21). C.R C´anovas thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference RYC 2019- 027949-I. M.D. Basallote thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference IJC 2018-035056-I. A. Parviainen thanks the Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference IJCI-2016-27412. The comments and helpful criticisms of three anonymous reviewers and the support of Professor Wen-Xiong Wang (Editor) have considerably improved the original manuscript and are also gratefully acknowledged. Funding for open access charge: Universidad de Huelva/CBUA.

This study investigates the behavior of Tl in the Ría de Huelva (SW Spain), one of the most metal polluted estuaries in the world. Dissolved Tl concentration displayed a general decrease across the estuary during the dry season (DS); from 5.0 to 0.34 μg/L in the Tinto and Odiel estuaries, respectively, to 0.02 μg/L in the channel where the rivers join. A slighter decrease was observed during the wet season (WS) (from 0.72 to 0.14 μg/L to 0.02 μg/L) due to the dilution effect of rainfalls in the watersheds. These values are 3 orders of magnitude higher than those reported in other estuaries worldwide. Different increases in Tl concentrations with salinity were observed in the upper reaches of the Tinto and Odiel estuaries, attributed to desorption processes from particulate matter. Chemical and mineralogical evidences of particulate matter, point at Fe minerals (i.e., jarosite) as main drivers of Tl particulate transport in the estuary. Unlike other estuaries worldwide, where a fast sorption process onto particulate matter commonly takes place, Tl is mainly desorbed from particulate matter in the Tinto and Odiel estuaries. Thus, Tl may be released back from jarositic particulate matter across the salinity gradient due to the increasing proportion of unreactive TlCl0 and K+ ions, which compete for adsorption sites with Tl+ at increasing salinities. A mixing model based on conservative elements revealed a 6-fold increase in Tl concentrations related to desorption processes. However, mining spills like that occurred in May 2017 may contribute to enhance dissolved and particulate Tl concentrations in the estuary as well as to magnify these desorption processes (up to around 1100% of Tl release), highlighting the impact of the mine spill on the remobilization of Tl from the suspended matter to the water column.

CAPOTE (MINECO; CGL 2017-86050-R)

TRAMPA (MINECO; PID 2020-119196RB-C21)

Spanish Ministry of Science and Innovation for the Postdoctoral Fellowship granted under application reference RYC 2019- 027949-I.

Postdoctoral Fellowship granted under application reference IJCI-2016-27412

Funding for open access charge: Universidad de Huelva/CBUA