Manure and iron oxide show potential for reducing uptake of arsenic and mercury in lettuce grown in a contaminated mining site

Abstract

The poor soil quality and high concentrations of potentially toxic elements (PTEs) found in gold mine tailings make them inappropriate for crop production. Assessing the viability of mine tailings for crop production after mining is essential because of the harmful impacts of these PTEs on food safety and human health. A 44-day pot experiment was conducted to test the effectiveness of different soil amendments in reducing the levels of PTEs at a decommissioned mining site in south-western Ghana. Compost, iron oxides, and poultry manure were applied individually or in combination to the mine soil in the pots. Lettuce (Lactuca sativa L.) was subsequently planted in the pots. Upon reaching maturity, the lettuce was harvested, and an analysis of the nutrients and PTE contents in both the soil and plants was done. The uptake of PTE by lettuce was evaluated, and the transfer coefficients of the PTEs were determined. The addition of manure and iron oxide as distinct ameliorants significantly decreased the uptake of PTEs by lettuce. The application of manure led to a 93 % decrease in arsenic (As) bioaccumulation in lettuce. Iron oxide resulted in a notable 67 % decrease in the bioaccumulation of As in lettuce. The exclusive application of manure led to an 83 % reduction in Hg uptake by lettuce plants, while Co uptake experienced a 46 % increase. Utilizing manure and iron oxides could prove beneficial in enhancing soil quality and potentially reducing the uptake of arsenic and mercury by lettuce grown in the contaminated mining site.