Toxicity of biogenic zinc oxide nanoparticles to soil organic matter cycling and their interaction with rice-straw derived biochar

Abstract

Given the rapidly increasing use of metal oxide nanoparticles in agriculture as well as their inadvertent addition through sewage sludge application to soils, it is imperative to assess their possible toxic effects on soil functions that are vital for healthy crop production. In this regard, we designed a lab study to investigate the potential toxicity of one of the most produced nanoparticles, i.e. zinc oxide nanoparticles (nZnO), in a calcareous soil. Microcosms of 80 g of dry-equivalent fresh soils were incubated in mason jars for 64 days, after adding 100 or 1000 mg of biogenically produced nZnO kg−1 soil. Moreover, we also added rice-straw derived biochar at 1 or 5% (w: w basis) hypothesizing that the biochar would alleviate nZnO-induced toxicity given that it has been shown to adsorb and detoxify heavy metals in soils. We found that the nZnO decreased microbial biomass carbon by 27.0 to 33.5% in 100 mg nZnO kg−1 soil and by 39.0 to 43.3% in 1000 mg nZnO kg−1 soil treatments across biochar treatments in the short term i.e. 24 days after incubation. However, this decrease disappeared after 64 days of incubation and the microbial biomass in nZnO amended soils were similar to that in control soils. This shows that the toxicity of nZnO in the studied soil was ephemeral and transient which was overcome by the soil itself in a couple of months. This is also supported by the fact that the nZnO induced higher cumulative C mineralization (i.e. soil respiration) at both rates of addition. The treatment 100 mg nZnO kg−1 soil induced 166 to 207%, while 1000 mg nZnO kg−1 soil induced 136 to 171% higher cumulative C mineralization across biochar treatments by the end of the experiment. However, contrary to our hypothesis increasing the nZnO addition from 100 to 1000 mg nZnO kg−1 soil did not cause additional decrease in microbial biomass nor induced higher C mineralization. Moreover, the biochar did not alleviate even the ephemeral toxicity that was observed after 24d of incubation. Based on overall results, we conclude that the studied soil can function without impairment even at 1000 mg kg−1 concentration of nZnO in it.

Effects of zinc oxide nanoparticles on carbon mineralization kinetics and microbial attributes in plant residue-amended soils

“…The reductions observed in C min value can be related to a lower decomposer community in the presence of ZnO-NPs as previous studies have indicated that the decomposer microbial community is signi cantly vulnerable to ZnO-NPs(Collins et al, 2012;Ge et al, 2011;Shah et al, 2022). This nding is in agreement with that ofShemawar et al (2021), indicating that leaf litter C mineralization was decreased after ZnO-NPs addition to mesocosms containing sandy soil. García-Gómez et al (2015) also showed a substantial decline in the C mineralization of glucose in soils treated with ZnO-NPs.…”

“…The presence of NPs in the soil can signi cantly in uence the ability of the soil microorganisms to mineralize organic substances, and therefore a measurement of soil respiration kinetics is a valuable method to assess the impacts of NPs on soil microbial activity (Shemawar et al, 2021;Xin et al, 2020). In this study, the time-dependent organic C mineralization data were tted by the rst-order, double rst-order, rst-order E, and special models.…”

Unlocking the potential of co-applied biochar and plant growth-promoting rhizobacteria (PGPR) for sustainable agriculture under stress conditions

“…Biochar is rich in a range of mineral nutrients including nitrogen, phosphorus, potassium, calcium, magnesium, zinc, etc., depending upon the feedstock type and pyrolysis temperature [113]. Upon addition to soil, it is decomposed gradually to release these nutrients in the soil solution [114][115][116].…”

Green chemistry routed sugar press mud for (2D) ZnO nanostructure fabrication, mineral fortification, and climate-resilient wheat crop productivity

“…This approach of utilising the ZnO –SOM interaction interface may offer the required advantage of nutrient use efficiency due to its solubility-driven slow release moderated further by carbon sequestration. Thus, collectively leading to sustainable agriculture for a climate-resilient future 15 – 17 .…”