Microcosm-scale biogeochemical stabilization of Pb, As, Ba and Zn in mine tailings amended with manure and ochre

Abstract

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Effects of biochar, ochre and manure amendments associated with a metallicolous ecotype of Agrostis capillaris on As and Pb stabilization of a former mine technosol

“…The NH4NO3-extractable Fe concentration was low for P0% (0.02 µg.g -1 ), and only increased following the ochre amendment (27-fold) (Table 2), and can be explained by the NH4NO3-extractable Fe concentration of the ochre (1.04 µg.g -1 ) (Table 1). Such elevated Fe content in the ochre has been previously observed by Abed et al ( 2017) , Doi et al (2005) and Thouin et al (2019). However, one surprising fact was that although NH4NO3-extractable Fe concentration in manure was high (2.41 µg.g -1 ), no increase was observed following its addition to the Pontgibaud technosol, maybe due to its low application rate.…”

“…Finally, the results showed that SPW pH increases were higher when amendments were combined than when they were applied alone, showing neutral values compared to the slightly acidic values still observed with single amendment application. Such increases in SPW pH following biochar, ochre and/or manure amendments have previously been observed and attributed to the alkalinity of the three amendments (Marques et al 2008, Olimah et al 2015, Van Poucke et al 2018, which induces a liming effect. Indeed, biochar, ochre and manure presented alkaline pH values of 8.46, 8.29 and 9.52, respectively.…”

“…It was produced from the slow pyrolysis at 500 °C of hardwood biomass (mixture of oak, beech and charm), followed by a sieving to obtain a particle size between 0.5 and 1 mm. The ochre amendment was collected at a former charcoal mine (Alès) in France, as described in Thouin et al (2019). Before its incorporation into the soil, it was dried and crushed to obtain a fine powder.…”

Leaching of trace metals (Pb) from contaminated tailings amended with iron oxides and manure: New insight from a modelling approach

“…Organic wastes provide the nutrients necessary for plant growth, while marble wastes tend to increase pH, enhancing the immobilization of metal contaminants. To fully understand the influence of amendments on the behavior of metal contaminants, Thouin et al (2019) set up an original leaching experiment on mine tailings configured to be close to real conditions. The dynamic of natural recharge was reproduced by a regular water supply (every week).…”

“…Apart from a slight increase in Pb concentration during the first half of the experiment, a decrease to the base level during the rest of the experiment was recorded. Therefore, Thouin et al (2019) identified promising amendments to reduce Pb mobility in contaminated tailings. Nevertheless, this experiment, though critical for understanding these systems, was essentially qualitative as the nature and the rate of the main biogeochemical processes involved in the immobilization of Pb remain unknown.…”