The Application of Hyperspectral Imaging to Monitor Cadmium and Nickel Phytoremediation from Contaminated Soil Using Poplar Trees

Abstract

Pollution has been on the rise ever since the industrial revolution. In Lebanon, water and air pollution are among the most serious issues that require immediate solutions. Further, soil pollution cannot be excluded since it affects water sources and human nutrition. Soil pollution can happen due to hydrocarbon contamination or inorganic contamination like metal presence. More specifically, there are heavy metals (HMs) that if present above certain concentrations become contaminants to soils and crops. In this work, the use of plants, specifically a hyperaccumulator seedling called poplar, was explored as a remediation technique for cadmium (Cd) and nickel (Ni) contamination in soil. A pot experiment was set up in a greenhouse compartment at the American University of Beirut using synthetically contaminated clay soil to evaluate the efficiency of poplar seedlings in phytoremediation during a period of six months and was repeated with a second set of experiments. Further, the use of hyperspectral imaging (HSI) to detect and quantify heavy metals absorbed by different parts of the poplar plants was also assessed. The results showed that cadmium mostly accumulates in poplar leaves while nickel is found mostly in the roots of the plant. Roots of Ni-contaminated trees provided the most consistent trend in hyperspectral imaging when compared to atomic absorption spectrophotometry Ni concentrations results. Based on the above results and literature findings for poplar pot experiments, poplar trees were not found to be very effective for phytoremediation under the given experimental conditions of this work. Future work should consider running the experiment for a longer time and with higher concentrations to be assessed by the hyperspectral camera.