Macroscopic Observation of Soil Nitrification Kinetics Impacted by Copper Nanoparticles: Implications for Micronutrient Nanofertilizer.

Allison VandeVoort,Yuji Arai

doi:10.3390/nano8110927

Abstract

The potential agricultural use of metal nanoparticles (NPs) for slow-release micronutrient fertilizers is beginning to be investigated by both industry and regulatory agencies. However, the impact of such NPs on soil biogeochemical cycles is not clearly understood. In this study, the impact of commercially-available copper NPs on soil nitrification kinetics was investigated via batch experiments. The X-ray absorption near edge structure spectroscopy analysis showed that the NPs readily oxidized to Cu(II) and were strongly retained in soils with minimum dissolution (<1% of total mass). The Cu2+ (aq) at 1 mg/L showed a beneficial effect on the nitrification similar to the control: an approximately 9% increase in the average rate of nitrification kinetics (Vmax). However Vmax was negatively impacted by ionic Cu at 10 to 100 mg/L and CuNP at 1 to 100 mg/L. The copper toxicity of soil nitrifiers seems to be critical in the soil nitrification processes. In the CuNP treatment, the suppressed nitrification kinetics was observed at 1 to 100 mg/kg and the effect was concentration dependent at ≥10 mg/L. The reaction products as the results of surface oxidation such as the release of ionic Cu seem to play an important role in suppressing the nitrification process. Considering the potential use of copper NPs as a slow-release micronutrient fertilizer, further studies are needed in heterogeneous soil systems.

Highlights

With the rise of nanotechnology within the past decade, nanofertilizers have been considered for use in agricultural fields [1]
This study aims to investigate the effects of metallic CuNPs as a nanofertilizer component on the complex nitrogen cycle in agricultural soils
The extent of CuNP dissolution is important because the release of Cu ions is associated with the production of reactive oxygen species as well as DNA damage in bacteria [26]

Summary

Introduction

With the rise of nanotechnology within the past decade, nanofertilizers have been considered for use in agricultural fields [1] While this technology continues to advance, the possibility for slow-release micronutrients resulting from the nanosized solid state of these products is appealing for some agricultural systems. In a study of hydroponic zucchini plant growth in the presence of CuNPs at 1000 mg/L, Stampoulis and coworkers found that exposure to metallic CuNPs resulted in a slower rate of plant growth compared to the control They found that 1000 mg/L of bulk Cu had approximately the same effect as 10 mg/L CuNO3, and that 1000 mg/L of CuNPs had a similar effect as 100 mg/L CuNO3 [8]. They reported CuNPs did not exhibit significant toxicity in oregano

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