Response of Key Soil Parameters during Compost-Assisted Phytostabilization in Extremely Acidic Tailings: Effect of Plant Species

Abstract

Phytostabilization of mine tailings acts to mitigate both eolian dispersion and water erosion events which can disseminate barren tailings over large distances. This technology uses plants to establish a vegetative cover to permanently immobilize contaminants in the rooting zone, often requiring addition of an amendment to assist plant growth. Here we report the results of a greenhouse study that evaluated the ability of six native plant species to grow in extremely acidic (pH ~ 2.5) metalliferous (As, Pb, Zn: 2000–3000 mg kg−1) mine tailings from Iron King Mine Humboldt Smelter Superfund site when amended with a range of compost concentrations. Results revealed that three of the six plant species tested (buffalo grass, mesquite, and catclaw acacia) are good candidates for phytostabilization at an optimum level of 15% compost (w/w) amendment showing good growth and minimal shoot accumulation of metal(loid)s. A fourth candidate, quailbush, also met all criteria except for exceeding the domestic animal toxicity limit for shoot accumulation of zinc. A key finding of this study was that the plant species that grew most successfully on these tailings significantly influenced key tailings parameters; direct correlations between plant biomass and both increased tailings pH and neutrophilic heterotrophic bacterial counts were observed. We also observed decreased iron oxidizer counts and decreased bioavailability of metal(loid)s mainly as a result of compost amendment. Taken together, these results suggest that the phytostabilization process reduced tailings toxicity as well as the potential for metal(loid) mobilization. This study provides practical information on plant and tailings characteristics that is critically needed for successful implementation of assisted phytostabilization on acidic, metalliferous mine tailings sites.

Abundance and Activity of 16S rRNA,AmoAandNifHBacterial Genes During Assisted Phytostabilization of Mine Tailings

“…Of interest was the fact that in the QB treatment pH stabilized at 4.7±0.6, whereas the TC and BG treatments continued to decrease to 3.5±0.5 and 3.1±0.3, respectively. These results contrast with our previous short-term greenhouse pot-study in compost-amended IKMSS tailings, where pH remained stable in the compost amended treatment for 60 days and actually increased significantly in planted treatments (Solís-Domínguez et al ., 2012). Surprisingly, after 60 days, BG treatments maintained a higher pH in the more acidic bulk and rhizosphere influenced tailings than QB.…”

“…The microbial communities of these materials are typically dominated by autotrophic iron- and sulfur-oxidizing populations with very low levels of bacterial heterotrophs (Mendez et al . 2007; Solís-Domínguez et al . 2012).…”

“…2005; Solís-Dominguez et al . 2011; Solís-Dominguez et al . 2012) and nifH copy number has been shown to increase with progressing plant succession in copper mine tailings (Huang et al .2011).…”

Bioavailability-Based In Situ Remediation To Meet Future Lead (Pb) Standards in Urban Soils and Gardens

“…53 In addition, plants may serve as a physical barrier through phytostabilization of dust to reduce airborne distributions and exposures from highly contaminated mine tailings. 54 However, because any subsequent disturbance of physical barriers may reintroduce exposure to the contaminated soil below, it is advisable to use other remediation strategies such as in situ stabilization with soil amendments in conjunction with physical barrier approaches. In the context of urban gardening, Pb accumulation by food-source plants is not considered a significant exposure risk, provided crops are adequately washed.…”

Germination of Bouteloua dactyloides and Cynodon dactylon in a Multi-Polluted Soil

“…Several studies have been developed with B. dactyloides and C. dactylon on phytoremediation for metal removal [12][13][14][15]. In Mexico, B. dactyloides, which is commonly called "Buffalograss", is a perennial native grass from semi-arid regions.…”