Contribution of glomalin to Pb sequestration in soils polluted by an acid battery recycling plant

DRA. CÁCERES MAGO, K.C.; DRA. SALAZAR M. J.; DRA. BECERRA A. G.

Conferencia; EMCEI; 2024

The lack of emissions control and inadequate waste disposal from an acid battery recycling plant in Bouwer (Córdoba, Argentina) has resulted in a significant accumulation of Pb over a large area, causing numerous cases of poisoning in the local population. This situation remains a potential toxicological risk, making phytoremediation with metal-tolerant plants and microorganisms a key tool for the recovery of the affected area. Therefore, this study aimed to assess the amount of glomalin-related soil protein (GRSP), produced by arbuscular mycorrhizal fungi (AMF), and its contribution to Pb sequestration, associated with the metallophytic plant Sorghum halepense growing in the contaminated area. Rhizospheric soil samples were collected from six sites with varying Pb content (μg g-1): Pb0 (24 ± 5), Pb1 (454 ± 14); Pb2 (1300 ± 23); Pb3 (4538 ± 45); Pb4 (15259 ± 94); and Pb5 (77589 ± 312). The uncontaminated site, Pb0, was located 2.7 km away from the factory area. GRSP was extracted using citrate buffer and autoclaving, and quantified by the Bradford protein assay. To determine the Pb content in GRSP through atomic absorption spectroscopy, the following steps were performed: protein precipitation at pH 2.5 with HCl, resuspension, dialysis against water, lyophilization, and digestion in HNO3. The study found similar amounts of GRSP (between 1.52 and 2.39 mg g-1) at all sites, with a significant increase at Pb3. The amount of Pb bound to GRSP (from 2.55 to 531.94 mg g-1) increased as soil Pb concentrations rose. This represented from 1.04 to 18.46 % of the total soil Pb, with a lower retention percentage at Pb5, but the same amount of GRSP bound 24 times more Pb at the most contaminated site (Pb5) compared to the least contaminated site (Pb1). This unprecedented study with such high levels of Pb concentration in soil suggests that the contribution of GRSP to element stabilization may be diminished in percentage terms at highly contaminated sites. Therefore, for AMF-assisted phytoremediation, it would be essential to develop plans that lead to increased glomalin in the soil to mitigate the adverse effects of highly heavy metal contaminated soils.