Assessing the Potential for Hemp to be Used in the Bioremediation of Soils Containing Perfluoroalkyl Substances (PFAS)

Abstract

Widespread industrial and commercial use of perfluoroalkyl substances (PFAS) has led to their accumulation in soil, groundwater, and freshwater supplies. The high stability of PFAS has rendered many traditional methods of remediation largely ineffective or too expensive to implement. This study seeks to quantify the efficacy of hemp as phytoremediator of soil contaminated by wastewater biosolid containing PFAS. Twenty hemp plants were cultivated using Arizona desert soil and mixed with biosolid contaminated with PFAS. The biosolid was incorporated into the soil at varying loading rates: 0%, 5%, 15%, and 30% biosolid by volume. Biosolid treatment groups consisted of five cannabis plants that were kept in a state of vegetative growth for 16 weeks. Initial soil samples were taken from the homogenized biosolid treatment mixtures before planting and compared with the final soil samples obtained from each plant to assess changes in PFAS levels. After harvest, plant tissue samples were taken from the roots, stems, and leaves for PFAS analysis. Plant growth metrics (height, stem diameter and number of axials) were recorded weekly for each plant. The plants grown in 5% biosolid by volume exhibited the greatest height and largest average stem diameter. The plants grown in 15% biosolid mixture appeared to be the healthiest and had greater biomass. The experiment unveiled significant translocation of PFOA and PFBS into various regions of the plants in all biosolid treatments. Specifically, within treatment #1 and treatment #2, 20.56% and 49.06% of the PFOA from the initial soil samples were translocated into the roots of plants, respectively. The types of PFAS that tend to be taken up by the plants are water soluble and tend to leach through soil. PFOS was found to be filtered out of samples by solid phase extraction ENV cartridges and were not translocated into the plants.