Phytostabilization of Zn and Cd in Mine Soil Using Corn in Combination with Biochars and Manure-Based Compost

Gilbert C Sigua,Thomas F Ducey,Mark G Johnson,Jeff M Novak,Jim A Ippolito,Kurt A Spokas,Don W Watts

doi:10.3390/environments6060069

Abstract

Mining activities could produce a large volume of spoils, waste rocks, and tailings, which are usually deposited at the surface and become a source of metal pollution. Phytostabilization of the mine spoils could limit the spread of these heavy metals. Phytostabilization can be enhanced by using soil amendments such as manure-based biochars 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 biochars and other organic amendments for mine spoil remediation are still unclear. In this greenhouse study, we evaluated the interactive effect of biochar additions (BA) with or without the manure-based compost (MBC) on the shoots biomass (SBY), roots biomass (RBY), uptake, and bioconcentration factor (BCF) of Zn and Cd in corn (Zea mays L.) grown in mine soil. Biochar additions consisting of beef cattle manure (BCM); poultry litter (PL); and lodge pole pine (LPP) were applied at 0, 2.5, and 5.0% (w/w) in combination with different rates (0, 2.5, and 5.0%, w/w) of MBC, respectively. Shoots and roots uptake of Cd and Zn were significantly affected by BA, MBC, and the interaction of BA and MBC. 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 BA, the greatest BCF for Cd in the shoot of 92.3 was from the application of BCM and the least BCF was from the application of PL (72.8). Our results suggest that the incorporation of biochar enhanced phytostabilization of Cd and Zn with concentrations of water-soluble Cd and Zn lowest in soils amended with manure-based biochars while improving the biomass productivity of corn. Overall, the phytostabilization technique and biochar additions have the potential to be combined in the remediation of heavy metals polluted soils.

Highlights

Mining activities usually produce a large volume of spoils, waste rocks, and tailings, which are usually deposited at the soil surface
On the root uptake of Cd and Zn, the application of beef cattle manure (BCM), lodge pole pine (LPP), and poultry litter (PL) resulted in 127.3% and 63.8%, −20.2% and −31.8%, 62.4% and −21.9% over the untreated plants, respectively (Table 6). These results suggest that the effects of biochar application on the shoot and root uptake of Cd and Zn by corn may vary significantly with biochars produced from different feedstocks
Corn applied with 2.5% BCM has the greatest Cd and Zn bioconcentration factor (BCF) in the shoots and these results suggest that corn can accumulate large quantities of metal in their shoot tissues when grown in contaminated mine soils

Summary

Introduction

Mining activities usually produce a large volume of spoils, waste rocks, and tailings, which are usually deposited at the soil surface. Mining activities can lead to extensive environmental pollution of terrestrial ecosystem due to the deposition of heavy-metal containing waste materials, tailings, and lagoon wastes [1,2,3]. Metal (loid) contaminants such as Cd and Zn are significant issues, for the environment, but especially for human health [4,5,6]. These contaminated areas present a health risk and are recognized as areas that need to be remediated to allow for crop phytostabilization to occur [1]

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