Modeling phytoremediation of aged soil Ni from anthropogenic deposition using Alyssum murale

Several field-scale phytoextraction scenarios were created in a greenhouse study to investigate the feasibility of using Alyssum murale, to remediate three types of industrially Ni-contaminated soil (heavy clay, sand, organic muck) from Port Colborne, Ontario. The observed distribution of Ni mass between soil and aboveground vegetation was used in STELLA modeling software to predict timelines for the target soil Ni concentration, namely 1200 mg Ni/kg. Alyssum murale grown in sand would have a relatively constant pool of Ni available for plant uptake, which would not be the case for plants grown in organic muck and heavy clay. The maximum Ni extraction (%, plant Ni mass/soil Ni mass) was achieved in A. murale grown in unfertilized clay soil at the higher irrigation rate. Using these data, the STELLA model predicted that 246 years would be required to reduce soil Ni concentration in the most efficient combination of treatments to the remediation target. In addition, hypothetical A. murale Ni extraction in plant-soil systems optimized by manipulating soil chemistry and physical attributes, were modeled. The most optimized A. murale plant-soil systems for Ni extraction would require 9 years to achieve the same reduction, and it is not clear that this optimization can be achieved in the field. This study showed that phytoremediation using A. murale is not likely a time-sensitive approach for these soils.