Does enhancing plant-microbe symbiosis improve phytostabilization in mine tailings more than compost amendment?
Abstract
The accumulation of mining waste (e.g. tailings piles, leachate ponds) is hazardous to people and industries through the spread of toxic heavy metals (e.g. Pb, Cr, Sb, As) by wind and water. Phytostabilization seeks to establish metal-tolerant plants in contaminated areas to decrease metal mobilization and physically stabilize waste material. One method for further decreasing metals mobilization and encouraging plant growth is the addition of organic and microbial amendments during phytostabilization. We used a series of experiments to determine whether the addition of municipal waste compost and/or bacterial endophytes (bacteria that live symbotically within plants) as seed coats could improve phytostabilization by Bouteloua curtipendula, a widespread grass species. We used two mine waste products from historical mining areas south of Tucson, AZ: polymetallic (Pb-Zn) mine tailings and porphyry copper waste rock. Seeds of B. curtipendula collected near the mines were coated with a mix of 11 microbial endophytes. The grasses were grown in an indoor chamber for 30 - 60 days, and we quantified phytostabilization success by evaluating plant health, soil health, and metal mobilization. We quantified plant health through above- and belowground biomass, soil health through increases in organic carbon, nitrogen, and microbial biomass, and metal mobilization into plant roots and shoots and from the tailings. Regardless of tailing type, we observed greater B. curtipendula biomass, organic carbon accumulation (the majority derived from compost, determined with stable carbon isotopes), and microbial biomass with both compost and endophyte addition. In the polymetallic tailings, heavy metals (Pb, As, Ag) preferentially mobilized in or around roots rather than shoots. Further work is underway to evaluate changes in endophyte communities among treatments, and to quantify how microbial communities and metals vary with amendment addition. Our results currently suggest that a viable means of improving phytostabilization and mining sustainability may be with the combined addition of organic amendments sourced from existing waste streams and endophyte seed coats that encourage plant viability.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGH33C1203C
- Keywords:
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- 1065 Major and trace element geochemistry;
- GEOCHEMISTRY;
- 0210 Coal geology;
- GEOHEALTH;
- 0215 Economic geology;
- GEOHEALTH;
- 1834 Human impacts;
- HYDROLOGY