Fate and Effects of Nanoparticles in Soil

The environmental risks of manufactured nanoparticles (NPs) are attracting increasing attention from both industrial and scientific communities. This proposal focuses on the fate and behavior of silver and cerium NPs, the most widely used nanoparticles, in water-soil-plant continuum. These NPs have shown to be taken-up, translocated and bio-accumulated in plant edible parts. However, very little is known about the behavior of silver and cerium NPs in soil-plant system as affected by dissolved organic matter (DOM). This type of knowledge is critical to assessing the environmental fate and risks related to NP exposure. Thus the overall goal of this project is to elucidate the role of DOM in soil retention, bioavailability and plant uptake of silver and cerium oxide NPs. To accomplish this study of a relatively a new field in environmental research (nanoparticles in water-soil-plant continuum) we suggest a synergistic cooperation of soil chemists, environmental chemist, plant physiologist and analytical chemist. We plan to conduct a systematic study using two types of NPs (with different coating), three types of soils with low content of native DOM, two types of exogenous DOM (isolated from composted biosolids and peat soil), and two important agricultural crops - cucumber and chickpea. The following processes, and mechanisms, will be elucidated: 1) adsorption and fractionation of DOM by NPs as affected by pH, ionic strength and composition; 2) NPs retention by soils as affected by DOM; 3) the effect of DOM on NPs uptake, phytotoxicity and bioaccumulation in plants. We plan to use state of the art analyses to characterize the processes, which will enable their mechanistic understanding. To characterize adsorption, retention and fractionation of DOM we will use wet chemistry analyses, spectroscopic methods (IR, NMR), dynamic light scattering, and microscopy (TEM, AFM). To study uptake and translocation of nanoparticles by plants we will use ICP-MS and microscopy tools (TEM, SEM, synchrotron micro X-ray fluorescence). To elucidate the speciation of the NPs in soils and plants, X-ray absorption spectroscopy will be used. The proposed work will provide fundamental information for the mutual impact of NPs and DOM upon their interactions, and will help to elucidate the effect of essential soil factor (i.e., DOM) on retention, bioavailability, uptake and phytotoxicity of engineered NPs in soil-plant system. This research is expected to advance our understanding of the intricate relationship of NPs and DOM in soils and plants amended with biosolids where most NPs likely reside, thus promoting their safe use in agriculture.