Copper Nanoparticles and Nitrogen Balance in Soil Systems.

With the rise of nanotechnology within the past decade, nanofertilizers have been developed for use in agricultural fields. While this technology is still relatively new, the possibility for slow-release micronutrients resulting from the nano-sized solid state of these products is appealing to many farmers. Copper, an essential micronutrient for all crops, is a commonly produced nanoparticle in its metallic state as copper nanoparticles (CuNP). Like many micronutrients, these CuNPs have the potential to be beneficial to plants and/or microorganisms by preventing copper deficiency; however, an overdose of CuNPs can also lead to toxicity for these same organisms. Furthermore, they may impact the complex nitrogen cycle in soil systems, particularly bacterial nitrification, in which the stable, plant-available ammonium (NH₄⁺) is converted into the plant available, but easily leached nitrate (NO₃^-).

This study aims to analyze the effects of CuNPs as nanofertilizers on the complex nitrogen cycle, which directly impacts soil tilth for agricultural practices. These CuNPs may also give further benefit to soil systems by inhibiting the bacterial nitrification process in the soil. The physical state of CuNPs as nano-sized solid metal rather than pure dissolved ions has the potential to allow for a controlled release over time in soil solutions. The activity of CuNPs was analyzed in soil systems, including dissolution and sorption onto soil surfaces in the presence of a variety of background electrolytes. Nitrification was measured through nitrate and nitrite analysis on solutions containing up to 100 mg/L CuNP and up to 10 mg/L Cu²⁺. The interactions of CuNPs in soil solution were impacted by both electrolyte and ligand concentrations. Nitrification experiments indicate that the nitrification process is impacted by both ionic and nanoparticulate copper. These data suggest that CuNP efficiency is greatly impacted by environmental conditions.