Passive sampling field studies

Fux, E., C. Marcaillou, F. Mondeguer, R. Bire, and P. Hess. 2008. Field and mesocosm trials on passive sampling for the study of adsorption and desorption behaviour of lipophilic toxins with a focus on OA and DTX1. Harmful Algae 7 574-583. 

When compared to traditional and alkaline treatments, passivation is a low-cost technique (Kapadia et al. 1999). One of the problems associated with using passivation on weathered rock samples is the large amount of lime required to maintain a pH of 12 (De Vries 1996). Successful application of this technique may be difficult (Glover 2007) and the chemistry of the permanganate coating is still not clear (De Vries 1996 Felipe 2008) hence, more laboratory and long-term field studies are required to better understand the technique and its long term effectiveness. 

The oxidation of pyrite is suppressed by coating it with oxalic acid because this treatment lowers the standard redox potential of Fe(III)/Fe(II) and forms a complex (Sasaki et al. 1996). Belzile et al. (1997) studied the possible passivation of pyrite by oxalic acid as compared with other agents such as acetyl acetone, humic acid and sodium silicate on samples from Kidd Creek mine in Timmins, Ontario. They concluded that oxalic acid was more efficient than the other agents tested in reducing oxidation of pre-oxidized samples. However, it was noted that the effectiveness of oxalic acid requires high temperature (65 °C), which restricts its field application it is also toxic (Belzile et al. 1997). 

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