Negative Effects of Copper Oxide Nanoparticles on Carbon and Nitrogen Cycle Microbial Activities in Contrasting Agricultural Soils and in Presence of Plants

Abstract

Metal-oxide nanoparticles (NPs) such as copper oxide (CuO) NPs offer promising perspectives for the development of novel agro-chemical formulations of pesticides and fertilizers. However, their potential impact on agro-ecosystem functioning still remains to be investigated. Here, we assessed the impact of CuO-NPs (0.1, 1, and 100 mg/kg dry soil) on soil microbial activities involved in the carbon and nitrogen cycles in five contrasting agricultural soils in a microcosm experiment over 90 days. Additionally, in a pot experiment, we evaluated the influence of plant presence on the toxicity of CuO-NPs on soil microbial activities. CuO-NPs caused significant reductions of the three microbial activities measured (denitrification, nitrification, and soil respiration) at 100 mg/kg dry soil, but the low concentrations (0.1 and 1 mg/kg) had limited effects. We observed that denitrification was the most sensitive microbial activity to CuO-NPs in most soil types, while soil respiration and nitrification were mainly impacted in coarse soils with low organic matter content. Additionally, large decreases in heterotrophic microbial activities were observed in soils planted with wheat, even at 1 mg/kg for soil substrate-induced respiration, indicating that plant presence did not mitigate or compensate CuO-NP toxicity for microorganisms. These two experiments show that CuO-NPs can have detrimental effects on microbial activities in soils with contrasting physicochemical properties and previously exposed to various agricultural practices. Moreover, we observed that the negative effects of CuO-NPs increased over time, indicating that short-term studies (hours, days) may underestimate the risks posed by these contaminants in soils.

Smart nanocomposites of chitosan/alginate nanoparticles loaded with copper oxide as alternative nanofertilizers

“…Although NP toxicity strongly depends on the plant species, growth conditions, exposure time, concentration, type and size of NPs, we can assume that the concentration optimized for germination was in the range of low concentration that is reported in several works to not cause damage but to stimulate the plant growth by playing a crucial role as a microelement useful for the plant. [63][64][65][66]…”

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

“…Particle size-dependent increases in soil pH at 1 hour after application were likely due to differences in the surface charge and buffering capacity of the differently sized particles, rather than by CuO dissolution associated condensation reactions. 20,29,[98][99][100][101] Treatment with CuCl 2 resulted in soil acidification, likely via Cu 2+ hydrolysis, which further increased Cu availability from the highly Environmental Science: Nano Paper soluble salt (Fig. 3A, Table S4 †).…”

“…18,19 Despite ubiquitous usage and accumulation in and around agricultural soils, the fate and influence of nCuO and Cu in general on soil microbial biomass and activity is still poorly understood. 3,14,[18][19][20] The effects of Cu and nCuO exposure on microbial biomass and activity are often negative, with reduction dependent upon Cu input amount, soil texture, pH, and soil organic carbon (SOC) content. 14,15,[20][21][22][23][24] Soils with low pH, low organic carbon content, and coarse texture typically have more biologically available Cu than soils with high pH, high organic carbon content, and fine texture.…”

“…3,14,[18][19][20] The effects of Cu and nCuO exposure on microbial biomass and activity are often negative, with reduction dependent upon Cu input amount, soil texture, pH, and soil organic carbon (SOC) content. 14,15,[20][21][22][23][24] Soils with low pH, low organic carbon content, and coarse texture typically have more biologically available Cu than soils with high pH, high organic carbon content, and fine texture. [20][21][22]24 Regardless of soil properties, microbial communities in agricultural systems are particularly prone to Cu exposure through repeated application of Cu fungicides, potentially threatening microbial biomass and function.…”

“…14,15,[20][21][22][23][24] Soils with low pH, low organic carbon content, and coarse texture typically have more biologically available Cu than soils with high pH, high organic carbon content, and fine texture. [20][21][22]24 Regardless of soil properties, microbial communities in agricultural systems are particularly prone to Cu exposure through repeated application of Cu fungicides, potentially threatening microbial biomass and function. 25 Responses are dose dependent, with limited responses at low doses and nonlinear perturbations experienced at high doses.…”