Phytostabilization of Zn and Cd in mine soil using corn in combination with biochars and manure-based compost

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

Submitted to: Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2019
Publication Date: 6/13/2019
Citation: Sigua, G.C., Novak, J.M., Watts, D.W., Ippolito, J.A., Ducey, T.F., Johnson, M.G., Spokas, K.A. 2019. Phytostabilization of Zn and Cd in mine soil using corn in combination with biochars and manure-based compost. Environments. 6(6):69. https://doi.org/10.3390/environments6060069.
DOI: https://doi.org/10.3390/environments6060069

Interpretive Summary: Numerous studies have been done on adding organic amendments (e.g., biochars, sewage sludge, manures) to soil to promote phytoextraction process, but only few studies have evaluated the combined effect of organic amendments and phytostabilization with corn in Cadmium (Cd) and Zinc (Zn) contaminated mine soils. There is a lack of agreement over the influence of organic amendments such as biochars on metal immobilization in soil. In our study, we evaluated the interactive effects of manure- and plant-based biochar applications with or without compost on shoots and roots biomass production, uptake, and bioconcentration factor (BCF) of Zn and Cd of corn grown in mine soil. Biochars may have several effects on heavy metals and can offer several advantages, alone or in combination with other amendments during remediation of soils contaminated with heavy metals. Results of our study can be summarized as follows: i) with increasing rates of biochar in combination with increasing application rates of compost beef cattle manure enhanced soil pH decreased the concentrations of water-soluble Cd and Zn in mine soils; ii) effects of biochar application on shoot and root uptake of Cd and Zn by corn varied significantly with biochars produced from different feedstocks; and iii) the BCF values of Cd and Zn in corn were considerably greater than 1, which are evident that Cd and Zn in mine soils were highly bio-accumulated and phytostablized due to biochar and phytostabilization using corn. Overall, our results suggest that phytostabilization when combined with biochar application have the potential for the remediation of heavy metals polluted soils. Biochars can reduce the bioavailability of heavy metals while phytostabilization can reduce the amount of soil heavy metals in polluted areas. Additionally, our study validates the findings that biochars can be designed to modify soil condition (i.e., soil pH) to reduce bioavailable Cd and Zn concentrations in contaminated mine soils.

Technical Abstract: Mining activities could produce a large volume of spoils, waste rocks, and tailings, which are usually deposited at the surface and become sources of metal pollution. Phytostabilization of the mine spoils could limit the spread of these heavy metals. Phytostabilization can be enhanced by using soil amendments like manure-based biochar capable of immobilizing metal(loid)s when combined with plant species that are tolerant of high levels of contaminants while simultaneously improving properties of mine soils. However, the use of manure-based biochar and other organic amendments for mine spoil remediation are still unclear. In this greenhouse study, we evaluated the interactive effect of biochar application and compost on shoots biomass yield (SBY), roots biomass yield (RBY), uptake, and bioconcentration factor (BCF) of Zn and Cd in corn (Zea mays L.) grown in mine soil. Biochar sources (BS) consisted of beef cattle manure (BCM); poultry litter (PL); and lodge pole pine (LPP) were applied at 0, 2.5, and 5.0 percent (%) in combination with different rates (0, 2.5, and 5.0%) of cattle manure compost (CMC), respectively. Shoots and roots uptake of Cd and Zn were significantly affected by BS, CMC, and the interaction of BS and CMC. Corn plants that received 2.5% PL and 2.5% BCM had the greatest Cd and Zn shoot uptake, respectively. Corn plants with 5% BCM had the greatest Cd and Zn root uptake. When averaged across BS, the greatest BCF for Cd in the shoot of 92.3 was from the application BCM and the least BCF was from the application of PL (72.8). Our results suggest that incorporation of biochar enhanced phytostabilization of Cd and Zn with concentrations of water-soluble Cd and Zn lowest in soils amended with both manure-based biochars while improving biomass productivity of corn. Overall, phytostabilization technique and biochar application have the potential to be combined in the remediation of heavy metals polluted soils.