Assessing chromium mobility in natural surface waters: Colloidal contribution to the isotopically exchangeable pool of chromium (EwCr value). (May 2018)

• Record Type: Journal Article
• Authors: Bolaños-Benítez, Viviana; van Hullebusch, Eric D.; Garnier, Jérémie; Quantin, Cécile; Tharaud, Mickaël; Lens, Piet N.L.; Sivry, Yann
• Is Part Of: Applied geochemistry. Volume 92(2018)
• Page Start: 19
• Page End: 29
• Publication Date: 2018-05
• Subjects: Isotopic exchange -- Chromium -- Mobility -- Colloid -- SPM -- Mining impact; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2018.02.007
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: The labile pool of chromium (Cr), ECr value for soils and E w Cr value for suspended particulate matter (SPM) in water, can be efficiently assessed in different environmental compartments through the use of isotopic dilution techniques. The overall objective of this work was to evaluate Cr availability based on the suspended particle matter size range and, more specifically, to determine the role of colloids in the calculation of the E w Cr value. Surface water samples were collected from ponds and streams at the active nickel mine of Barro Alto (Goiás State, Brazil). Two isotopic exchange (spiking) experiments were performed: #E1, the water samples were either spiked before cascade filtration (0.7 μm, 0.2 μm, 500 kDa and 1 kDa) or, #E2, according to the range of particle sizes (>0.7 μm, 0.2–0.7 μm, 500 kDa–0.2 μm and 1–500 kDa). This study showed that: 1) mining activities in ultramafic environments locally increase the presence of particulate matter and colloids containing Cr-bearing phases, mainly iron oxy(hydroxides); 2) in the pristine area, chromium was mainly associated with colloids (1 kDa–500 kDa), while mining activities increase the amount of large particles (>0.2 μm) containing chromium in the impacted area, and 3) there is an overestimation of the exchangeable pool of chromium (E W Cr value) due to the presence of organic and inorganic colloids containing non-exchangeable chromium. A correction to overcome this discrepancy was proposed. Graphical abstract: Image 1 Highlights: The availability of chromium ( E W Cr -value ) according to the range of suspended particle matter size was assessed. Mining activities increase the content of chromium associated to the particulate fraction (>0.2 μm). There is an overestimation of the E W Cr -value due to the presence of colloids containing non-exchangeable chromium. A correction to deal with the overestimation of the E W Cr -value was proposed.