Partitioning of potentially toxic elements among two colloidal fractions and relevance for their mobility in different water types

Filipa Moreno,Patrícia Gomes,Ana Costa,Maria Rosário Costa,Teresa Valente,Rita Fonseca,O Chudaev,R Millot,R Harmon,Y Kharaka,O Shouakar-Stash

doi:10.1051/e3sconf/20199809020

Abstract

Potentially toxic elements are mobilized in aquatic systems in solution or bounded to colloids of different sizes, which may include nanometer particles. The present work studies the distribution of elements (Al, Fe, Zn, Mn, Co, Cd, Ni, Cu, and As) between small (<0.20 μm) and larger (0.45–0.20 μm) colloids in different waters sources in a world class metallogenic province (Iberian Pyrite Belt), including the acid mine waters. Syringe filters with pore-size ratings of 0.20 μm and 0.45 μm have been used to assess the transport and fate of these potentially toxic elements. The results show the contribution of colloids for mobility of arsenic and most metals, evidencing the role of the small ones in acid mine drainage.

Highlights

The presence of significant colloidal metal(loid) fractions in water bodies has implications on the transport, fate and bioavailability of potentially toxic elements (PTE)
PTE bound to colloids may harmfully affect riverine habitats and biota [2]
The straight practice of distinguishing between particulate and dissolved phases, using membrane or filters with 0.45 m pore-size may greatly neglect the importance of colloids [3,4,5]. This likewise drew attention to the inadequacy of this cut-off on the comprehensive understanding of the behaviour of the heterogeneous and multisource material found in natural systems. This scenario attains utmost expression in systems impacted by acid mine drainage (AMD), where the formation of iron ultrafine colloids in the nanoscale

Summary

Introduction

The presence of significant colloidal metal(loid) fractions in water bodies has implications on the transport, fate and bioavailability of potentially toxic elements (PTE). The straight practice of (operationally) distinguishing between particulate and dissolved phases, using membrane or filters with 0.45 m pore-size may greatly neglect the importance of colloids [3,4,5]. This likewise drew attention to the inadequacy of this cut-off on the comprehensive understanding of the behaviour (and effects) of the heterogeneous and multisource material found in natural systems. Such framework may compromise the acquisition of reliable results and accurate predictions on the PTE behaviour throughout the impacted water bodies [6]. This work aimed to compare the application of two (0.45 and 0.20 m) pore-size syringe filters in the treatment of different waters types from the Iberian Pyrite Belt (IPB), seeking meaningful relationships with regard to the PTE partitioning among both fractions

Study area

Experimental section

Results and discussion