Influence of a one-time biosolids application on elemental and nutrient concentrations on mine tailings

Abstract

Mine tailings are nutrient deficient, contain no organic matter, and have high metal concentrations preventing the long-term establishment of vegetation. The use of organic amendments, including biosolids, can help the revegetation of mine tailings by adding organic matter and nutrients but can increase metals in the receiving soil. There is also uncertainty if biosolids provide a long-term benefit, or if the benefits diminish with time. To test this, a study was conducted on two tailings storage facilities — a sand, and a silt loam — for a copper mine in the southern interior of British Columbia, Canada. In 1998, biosolids were applied at rates between 50 and 250 Mg·ha−1 and compared with a control and fertilizer treatment. Plots were sampled in 2000 and 2015 for total and available nutrients and metals. This study showed that 17 yr after a one-time biosolids application at different rates, the tailing storage facilities that received biosolids had higher carbon, nitrogen, phosphorus, and biomass compared with tailings that did not receive biosolids or received conventional fertilizer. Many elements such as carbon (C) did not change from 2000 to 2015 in biosolids-treated plots, indicating a long-term benefit to the tailings. Additionally, biosolids did not result in increased concentrations of metals above the national regulatory limits for agriculture. This study suggests that a one-time biosolids application can provide a long-term benefit to tailings, whereas proper application rates can reduce the risks of metal exceedances.