Effects of Lead and Arsenic in Soils from Former Orchards on Growth of Three Plant Species.

Historical use of lead arsenate as a pesticide in former orchards of eastern Washington State (USA) has resulted in legacy lead (Pb) and arsenic (As) soil contamination. However, the impacts on plant growth in soils with residual Pb and As contamination have not yet been quantified. To this end, a comparative study of plant growth impacts was performed for native bluegrass (Poa secunda), invasive cheatgrass (Bromus tectorum), and buttercrunch lettuce (Lactuca sativa). Using standard plant growth protocols, germination frequency and biomass growth were measured over a wide range of Pb and arsenate concentrations, with maximum concentrations of 3400 and 790 mg kg-1 for Pb and As, respectively. Results indicated that only the biomass growth for all species decreased in soils with the highest concentrations of Pb and As in the soil, with no impacts on soils with lower residual Pb and arsenate concentrations. No impact on percentage of germination was observed at any soil concentration. These results can be used to determine site-specific soil screening levels for use in ecological risk assessments for Pb and arsenate in soils. Environ Toxicol Chem 2022;41:1459-1465. © 2022 Battelle Memorial Institute. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Application of dielectrophoresis towards characterization of rare earth elements biosorption by Cupriavidus necator.

This work presents the dielectric characterization of rare earth elements (REEs) biosorption by Cupriavidus necator using dielectrophoretic crossover frequency measurements. Traditional means of characterizing biomass for biosorption is limited and time consuming. In this research we are presenting, for the first time, an electrokinetic method termed as dielectrophoresis (DEP) for the characterization of biosorption (uptake) of rare earth elements (REEs) by gram negative bacteria - Cupriavidus necator. To characterize, a 3mm-diameter point and planar microwell device platform is used to measure the DEP crossover frequency that yields the dielectric properties of the targeted biosorbents. Quantified dielectric properties of native Cupriavidus necator (REE-) and those exposed to rare earth elements (REE+): europium, neodymium, and samarium revealed a substantial change in the surface characteristics of the Cupriavidus necator after exposure to the REE solution. The response of C. necator to changes in REE exposure is substantially different for europium but similar between neodymium and samarium. Statistically both the REE+ and REE- groups dielectric signatures were significantly different proving that the REEs were absorbed by the bacteria. This research will revolutionize and impact the researchers and industrialists in the field of biosorption seeking for economical, greener, and sustainable means to recover REEs.