Microbial response to copper oxide nanoparticles in soils is controlled by land use rather than copper fate

Authors: Rippner, Devin; MARGENOT, ANDREW - University Of Illinois; FAKRA, SIRINE - Lawrence Berkeley National Laboratory; AGUILERA, L. ANDREA - University Of California, Davis; LI, CHONGYANG - University Of California, Davis; SOHNG, JAEEUN - University Of California, Davis; DYNARSKI, KATHERINE - University Of California, Davis; WATERHOUSE, HANNAH - University Of California; MCELROY, NATALIE - University Of California, Davis; WADE, JORDON - University Of Illinois; HIND, SARAH - University Of Illinois; GREEN, PETER - University Of California, Davis; PEAK, DEREK - University Of Saskatchewan; McElrone, Andrew; CHEN, NING - Canadian Light Source Inc; FENG, R - Canadian Light Source Inc; SCOW, K - University Of California, Davis; PARIKH, S - University Of California, Davis

Submitted to: Environmental Science: Nano
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2021
Publication Date: 11/5/2021
Citation: Rippner, D.A., Margenot, A.J., Fakra, S.C., Aguilera, L., Li, C., Sohng, J., Dynarski, K.A., Waterhouse, H., McElroy, N., Wade, J., Hind, S.R., Green, P.G., Peak, D., McElrone, A.J., Chen, N., Feng, R., Scow, K., Parikh, S. 2021. Microbial response to copper oxide nanoparticles in soils is controlled by land use rather than copper fate. Environmental Science: Nano. 8(12):3560-3576. https://doi.org/10.1039/D1EN00656H.
DOI: https://doi.org/10.1039/D1EN00656H

Interpretive Summary: Highly available copper fungicides such as soluble copper (Cu) salts can alter soil microbial community size, composition, and function, hurting agricultural productivity. Copper oxide nanoparticles (nCuO), a novel fungicide formulation, are thought to alter soil microbial communities more like Cu salts compared to larger bulk copper oxide particles (bCuO). In our work, we found that despite differences in nCuO particle solubility compared to bCuO, microbial response to Cu salt, nCuO, and bCuO treatment was determined by historical land use rather than copper addition. Microbial community size in soils taken from agricultural systems was unaltered by Cu exposure, regardless of source, but microbial function was compromised while microbial community size and function was negatively influenced by Cu exposure in grassland and forest soils. Our results can be used by fungicide applicators to optimize Cu fungicide use to protect soil health based on historical land management.

Technical Abstract: Copper (Cu) products, including copper oxide nanoparticles (nCuO), are critically important agricultural fungicides and algaecides. The spray application onto crops and subsequent aerosol drift of these Cu products, especially nCuO, on to soil may alter nutrient cycling and microbial communities in both managed and unmanaged environments. We measured the influence of land use on soil microbial biomass and respiration in response to the addition of nCuO to alluvial soils (Mollic Haploxeralfs and Mollic Xerofluvents) formed from the same parent material. Different land uses included grassland, forest and both organic and conventional managed row crops. Soil samples were amended with 0, 10, and 1000 mg Cu kg-1 soil in the forms of CuCl2, 16 nm CuO (16nCuO), 42 nm CuO (42nCuO), and larger than nanoparticle sized bulk CuO (bCuO). Copper availability immediately increased in all soils following Cu addition in the order of CuCl2>16nCuO>42nCuO >bCuO. After 70 days Cu availability was diminished across land uses and lowest in soils treated with bCuO. The relatively high availability of Cu after treatment with nanoparticle-sized CuO was determined by micro-x-ray fluorescence microscopy (µXRF) to be due to the dissolution of CuO particles. Focused and bulk x-ray adsorption near edge structures (µXANES, XANES) spectroscopy confirmed the dissolution of nano-sized CuO and formation of new copper complexes (Cu adsorbed to silicates/organic matter) across land uses. Respiration, an indicator of microbial activity, was suppressed by Cu additions, especially CuCl2. Copper effects on soil microbial biomass was sensitive to land use. In agricultural soils, microbial biomass was unaltered by Cu form, regardless of concentration, whereas in unmanaged soils, it decreased following exposure to CuCl2 and 42nCuO at the highest copper dose. These results suggest that land use history has little impact on Cu chemical fate in soils, but strongly modulates microbial response to Cu exposure.