Roxana Paula Colombo

The Matanza-Riachuelo river basin (MRB) is considered one of the most polluted sites in the world, with very high levels of heavy metal(loid)s (HMs). However, as in almost all urban basins, studies on biological indicators of soil health are limited. In this work, we explore the potential of arbuscular mycorrhizal fungi (AMF) diversity, plant mycorrhizal status, and glomalin-related soil proteins (GRSP) concentration as bioindicators of soil health. We sampled three regions of the MRB: upper, middle and lower basins. The highest concentrations of HMs were detected in the lower basin, because it is exposed to a high input of pollutants and anthropogenic impact. Community composition and diversity were compared across the different soil samples. The Glomeraceae family was the most represented in the MRB, and Rhizoglomus intraradices was the only AMF species detected at every sampled site. This work constitutes the first report of 8 of the 16 AMF species described so far in the MRB. GRSP differences were strongly related to HMs concentrations. Both AMF species richness and GRSP concentrations were reliable biological indicators of soil health; while GRSP increases with soil toxicity, AMF richness decreases with soil disturbance.

Mining activities cause strong soil alterations, such as heavy metal (HM) pollution, which decreases the diversity of plant communities and rhizospheric microorganisms, including arbuscular mycorrhizal (AM) fungi. The polymetallic Paramillos de Uspallata mine in the Andes Mountains, the first mining exploitation in Argentina, provides a unique scenario to study AM fungal resilience after long-term disturbance following over 40 years of inactivity. This study aimed to analyze mycorrhizal status and AM fungal communities in the mine and a nearby unexploited area and to evaluate their associations with soil parameters to elucidate life history strategies. Long-term exposure to elevated Fe, Pb, Zn, and Ag concentrations and high electrical conductivity (EC, 5.46 mS/cm) led to the dominance of Entrophospora infrequens in association with Pappostipa speciosa, demonstrating that this AM species is a stress-tolerant strategist in symbiosis with a pioneer perennial plant, resilient in the most impacted mine areas. In contrast, the unexploited area, with an EC of 0.48 mS/cm and low HM contents, supported competitive and ruderal species, revealing distinct ecological strategies of AM fungi in disturbed versus undisturbed environments. These findings highlight the potential of E. infrequens for bioremediation and ecological restoration in post-mining landscapes.

Contaminated soils are a challenge for implementing biotechnology in bioremediation, the recovery of Critical and Strategic Raw Materials (CRMs and SRMs), and food security. European Union (EU) Governments have established strict limits on As, Pb, Cd, and Hg in foods (Document 32023R0915) and requested the recovery of 34 CRMs within a circular economy (CE) (5th CRMs list). This study proposed a biotechnological tool for the decontamination of soil with heavy metal(loid)s by arbuscular mycorrhizal (AM)-assisted phytoextraction and the subsequent recovery of CRMs or by phytostabilization to prevent their entry into the food chain. It consisted of placing Baccharis salicifolia plants, inoculated or non-inoculated with AM fungi, into bioreactors (BRs) containing mining soil with Cd, Ni, and Cu, according to the Argentinian Patent (AR090183B1). The bioextractive potential (BP) was also estimated at the highest Technological Readiness Level (TRL) using a vegetable depuration module (VDM, TRL 6). Inoculated plants showed significantly higher aerial bioaccumulation coefficients (Cd: 68.62; P: 2.99; Ni: 2.51; Cu: 0.18) in BRs, and the BP values reached 1.16 g, 9.75 g, 2.40 g, and 213.1 g for Ni, Cd, Cu, and P, respectively. Finally, these CRMs and SRMs could be recovered from biomass through hydrometallurgy within a CE framework.

Contaminated soils are a challenge for implementing biotechnology in bioremediation, recovery of Critical and Strategic Raw Materials (CRMs and SRMs), and food security. European Union (EU) Governments have established strict limits on As, Pb, Cd, and Hg in foods (Document 32023R0915), and requested the recovery of 34 CRMs within a circular economy (CE) (5th CRMs list). This study proposed a biotechnological tool for the decontamination of soil with heavy metal(loids) by arbuscular mycorrhizal (AM)-assisted phytoextraction and subsequent recovery of CRMs, or by phytostabilization to prevent their entry into the food chain. It consisted of placing Baccharis salicifolia plants, inoculated or non-inoculated with AM fungi, into Bioreactors (BRs) containing mining soil with Cd, Ni, and Cu, according to the argentinian Patent (AR090183B1). The bioextractive potential (BP) was also estimated at the highest Technological Readiness Level (TRL) using a Vegetable Depuration Module (VDM, TRL 6). Inoculated plants showed significantly higher aerial bioaccumulation coefficients (Cd: 68.62; P: 2.99; Ni: 2.51; Cu: 0.18) in BRs, and the BP values reached 1.16 g, 9.75 g, 2.40 g, and 213.1 g for Ni, Cd, Cu, and P, respectively. Finally, those CRMs and SRMs could be recovered from biomass through hydrometallurgy within a CE framework.