Microbial response to designer biochar and compost treatments for mining impacted soils

Authors: Ducey, Thomas; Novak, Jeffrey; Sigua, Gilbert; IPPOLITO, JAMES - Colorado State University; Rushmiller, Hannah; Watts, Donald - Don; Trippe, Kristin; Spokas, Kurt; Stone, Kenneth; JOHNSON, MARK - Environmental Protection Agency (EPA)

Submitted to: Biochar
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2021
Publication Date: 4/7/2021
Citation: Ducey, T.F., Novak, J.M., Sigua, G.C., Ippolito, J.A., Rushmiller, H.C., Watts, D.W., Trippe, K.M., Spokas, K.A., Stone, K.C., Johnson, M.G. 2021. Microbial response to designer biochar and compost treatments for mining impacted soils. Biochar. 3:299-314. https://doi.org/10.1007/s42773-021-00093-3.
DOI: https://doi.org/10.1007/s42773-021-00093-3

Interpretive Summary: Over the past century, the soils of the Oronogo-Duenweg Mining Belt in southwest Missouri, have been impacted by heavy mining activity. This activity has contaminated the soils with high concentrations of the heavy metals cadmium (Cd), lead, and zinc (Zn). These heavy metals pose a threat to both human health and the environment, and the contaminated lands were listed as a US EPA Superfund Site. As a consequence of remediation to remove the lead, the productive soil horizons were also removed, leaving a subsoil with poor soil fertility characteristics, as well as residual cadmium and zinc. To improve soil fertility, we treated the soil with a combination of biochars and compost, all applied at several rates. Biochars were selected for their ability to bind heavy metals, while compost was selected to serve as source of organic carbon and nutrients to improve the soil. To test soil fertility, we grew two grass species. Our results indicate that the type of biochar used, and the rates of which the biochar and compost are applied influenced soil characteristics, plant biomass, and microbial properties. These results suggest that using biochar and compost can improve mine-impacted soil characteristics, which can help future remediation efforts.

Technical Abstract: The Oronogo-Duenweg mining belt is a designated United States Environmental Protection Agency Superfund site due to lead-contaminated soil and groundwater by former mining and smelting operations. This area has been subjected to almost a century of mining (from 1848 to the late 1960’s), during which over ten million tons of cadmium, lead, and zinc containing mining waste have contaminated over 10,000 acres. Sites that have undergone remediation – in which the O, A, and B horizons have been removed along with the lead contamination – have left the C horizon exposed and incalcitrant to revegetation efforts. Soils also continue to contain quantifiable Cd and Zn concentrations. In order to improve soil conditions and encourage successful site revegetation, our study employed three biochars, sourced from different feedstocks (poultry litter, beef lot manure, and lodge pole pine), at two rates of application (2.5%, and 5%), coupled with compost applied at rates of 0%, 2.5% and 5%. Biochars were selected for their potential to bind zinc and other heavy metals responsible for phytotoxicity, while locally sourced compost was selected for available organic carbon and nutrient incorporation into these depleted soils. Two plant species were grown in these amended materials, switchgrass (Panicum virgatum) and buffalograss (Bouteloua dactyloides). Our results indicate that – to varying degrees – biochar feedstock as well as biochar and compost application rates influenced soil physicochemical factors, above ground biomass, microbial composition, and enzyme functionality. Results suggest that soil reclamation using biochar and compost can improve mine-impacted soil biogeophysical characteristics, and potentially improve future remediation efforts.