The Use of Leaching Tests to Assess Metal Release from Contaminated Marine Sediment under CO2 Leakages from CCS

Abstract

This study provides a better knowledge of key parameters controlling the mobility of Dissolved Organic Carbon (DOC), As, Cd, Cr, Cu, Ni, Pb and Zn from contaminated marine sediment in contact with acidified seawater using static and dynamic standard leaching tests. These procedures have been modified in order to use different leaching agents, L/S ratios, contact times and pH values that simulate seawater acidification under CO 2 leakages scenarios. Studied sediment from a potential area of CO 2 storage, shows a high acid neutralisation capacity (ANC pH=4 =3.58 eq/kg) for deionised water as well as for seawater (ANC pH=4 =3.97 eq/kg). The availability control mechanism is shown by releasing Cd with seawater at pH values 6, 7 and 8 and by the releasing of Zn with seawater at pH 6; the solubility control mechanism appears for Ni release using natural seawater. Experimental results of metal release from the pH dependence leaching test are modelled with Visual MINTEQ geochemical software to predict metal release from sediment, obtaining minor differences with experimental values. An improvement in the metal release results has been obtained considering in the model the influence of the DOC, Fe-and Al-(hydr)oxides, humic acids and fulvic acids. The obtained results would be useful as a line of evidence input for the risk assessment of a Carbon Capture and Storage site where acidified seawater at different concentrations of CO 2 is in contact with sediment.

Effect of Acidic Industrial Effluent Release on Microbial Diversity and Trace Metal Dynamics During Resuspension of Coastal Sediment

“…V release was observed in all experimental conditions, according to previous studies reporting high V mobility at neutral/marine pH (Brunori et al, 2005; Reijonen et al, 2016). In contrast, As was not remobilized during our experiment conducted at neutral/marine pH, in agreement with previous studies showing low As solubilization from contaminated marine sediment and processing waste under aerobic and neutral pH conditions (Al-Abed et al, 2007; Martín-Torre et al, 2013). In the neutral/marine pH region, the low As release is probably due to the co-sorption of As and Fe in sediments (Saulnier and Mucci, 2000; Al-Abed et al, 2007).…”

“…Acidic industrial effluent induced an increase in the content of several trace metals (e.g., Cd, V) in our resuspension experiment and could influence metal dynamics by modifying some physico-chemical parameters, especially pH, which control TE chemical form and mobility (Kiratli and Ergin, 1996; Eggleton and Thomas, 2004; Millero et al, 2009; Wang Z. et al, 2015). Martín-Torre et al (2013) have shown that metal response to pH variation varies from one element to another. According to our study, Cd was not controlled by neutral/marine pH (7–8.5) range, because it forms strong chloro complexes in seawater, which are weakly influenced by pH change (Millero et al, 2009; Martín-Torre et al, 2013; Bruland, 2014).…”

“…Martín-Torre et al (2013) have shown that metal response to pH variation varies from one element to another. According to our study, Cd was not controlled by neutral/marine pH (7–8.5) range, because it forms strong chloro complexes in seawater, which are weakly influenced by pH change (Millero et al, 2009; Martín-Torre et al, 2013; Bruland, 2014). U mobility was controlled by pH (immobilized at initial pH < 8 and mobilized at initial pH > 8), because U is known to form strong complexes with carbonates and hydroxides influenced by pH (Millero et al, 2009; Cumberland et al, 2016).…”

Generalised mathematical model to estimate Zn, Pb, Cd, Ni, Cu, Cr and As release from contaminated estuarine sediment using pH-static leaching tests

“…This acidification could mobilise elements from marine and estuarine sediments (Rodríguez- Romero et al, 2014;Zheng et al, 2012). The risk of potential contaminant release from sediment is usually assessed using leaching tests (Ho et al, 2012;Martín-Torre et al, 2014;Payán et al, 2012a). The mobility and availability of contaminants from a sediment matrix are highly dependent on the leaching pH (Coz et al, 2007), so pH dependence leaching tests are essential for analysing the importance of these parameters.…”