Engineered metal oxide nanoparticles (NP) may impact soil biological processes essential to ecosystem services such as nutrient cycling by inhibiting soil enzymes. Previous work has shown that cupric ion (Cu2+) can inhibit soil hydrolytic enzymes, with consequences for cycling and bioavailability of soil nutrient elements including carbon (C), nitrogen (N), and phosphorus (P). We therefore examined the impacts of copper oxide (CuO) NP on soil enzyme activities across diverse ecosystems: two unmanaged ecosystems (woodland, grassland) and four agroecosystems (organic, conventional, and unfertilized), including a biochar-amended conventional system. For each ecosystem, activities of urease (N-cycling), β-glucosidase (C-cycling), phosphatase (P-cycling), and arylsulfatase (S-cycling) were evaluated following soil exposure to CuO NP (10 nm and 40 nm diameters) relative to CuO microparticle (9.5 µm diameter) and two copper ion controls (CuCl2, CuSO4) at 0, 100, and 1000 mg Cu kg-1 soil. Cu2+ activity in soils was additionally evaluated by an ion-selective electrode. We hypothesized that CuO NP effects would be reflect Cu2+ dissolution and activity, with increasing inhibition of enzyme activities with decrease with particle size (9.5 µm &lt; 40 nm &lt; 10 nm &lt; Cu2+ salts), and that these effects would vary by ecosystem type. As hypothesized, CuCl2 and CuSO4 produced greatest Cu2+ actvity, and decreased activity of phosphatase relative to the Cu-free control, but CuO NP decreased activity depending on land use and only for 10 nm NPs. 40 nm CuO NP and CuO microparticles did not change or even increased phosphatase activities. These trends were strongest in soils under organic agriculture and weakest in soils under woodland and grassland, and did not occur for the agricultural soil with biochar additions. Our results indicate that though CuO effects on soil enzymes may not be necessarily be mediated by Cu2+ solubility and that greater inhibition occurs for copper salts, smaller CuO NPs are more suppressive of soil enzyme activities. This holds implications for NP entry to ecosystems and managment (e.g., amendments such as biochar), which can differ in nutrient cycling and availability response.

Impacts of copper oxide nanoparticles on soil enzyme activities across diverse ecosystems

253rd National Meeting (2017)

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