PHOSPHATE-ENHANCED REMEDIATION OF LEAD AND ARSENIC CONTAMINATED SOIL: A GREENHOUSE EXPERIMENT

Past usages of lead-arsenate pesticides in the United States have resulted in elevated soil lead (Pb) and arsenic (As) concentrations in many areas, in particular orchards – some of them are being converted to gardens and farms. Human exposure to soil Pb and As is a major health concern. Phytoremediation have shown to be a sustainable method to remediate contaminated soils. It involves the usage of certain hyper-accumulating plants to naturally uptake trace metals from soil. It is well known that phosphate can help stabilize Pb in soil, and it can also enhance the mobilization of arsenic in soils. Therefore it potentially can enhance the phytoextraction of As by plants. A composite of co-contaminated soils with known levels of Pb and As were collected from a farm in New Jersey and used for this greenhouse study. The project will test the effectiveness of three different types of phosphate treatments: bone meal, Triple superphosphate (TSP), and manure compost. Pb-phosphate, a stable form of phosphate, will form in situ and result in the stabilization of soil Pb. Arsenic, on the other hand, will become mobile and phytoextracted by Pteris cretica, a species of ferns proven to have metal uptake potential, and Brassica juncea (Indian mustard). In addition, the effects of manganese oxide (MnO₂₎ and iron oxide (Fe₂O₃) in soils will be tested. The concentrations of Pb and As in plant tissues samples will be evaluated upon harvesting. The soil samples will be assessed for total Pb and As, as well as bioaccessible Pb and As using the EPA RBA method.