Nanoengineered Sorbents To Increase the Persistence of the Allelochemical Carvone in the Rhizosphere

Abstract

This study investigates the changes in sorption/desorption, dissipation and leaching of the two enantiomeric forms of the allelochemical carvone, R-carvone and S-carvone, after amending an agricultural soil sample with two nanoengineered sorbents: biochar (BC) and organoclay (OCl). The sorption of carvone enantiomers was non-enantioselective and similarly improved by the addition of OCl and BC to the soil. However, OCl-amended soil showed reversible sorption, whereas BC-amended soil displayed sorption-desorption hysteresis. Dissipation of carvone enantiomers was enantioselective. Both amendments increased the half-life of the enantiomers in soil compared to unamended soil. This effect was more pronounced for BCamended soil and for S-carvone. Leaching of R-and S-carvone through soil columns was scarce in unamended soil (< 7%), due to their rapid degradation during leaching, and null for OCl-and BC-amended soil, for which much of the applied R-and S-carvone remained in the top 0-5 cm amended soil layer. Addition of biochars and organoclays could help increase the persistence of carvone enantiomers in the rhizosphere, which may favor their use as residual pest management substances.

Sorption, persistence, and leaching of the allelochemical umbelliferone in soils treated with nanoengineered sorbents

“…Since allelochemicals can display a poor stability in aqueous solution and/or soil extracts, it is important to test their storage stability to avoid analytical artefacts when conducting experiments to assess their behaviour in soils 24,49 . The stability of umbelliferone in different water/methanol mixtures exposed to light and under dark conditions is illustrated in Supplementary Fig.…”

“…The impact of light exposure and presence of soluble soil components on the storage stability of umbelliferone was studied for umbelliferone aqueous solutions containing different amounts of methanol, which was used as a stabiliser. High concentrations of alcohol have antimicrobial properties 48 and previous experiments had shown that the addition of methanol helped stabilise aqueous solutions of readily biodegradable organic compounds, presumably by eliminating microbial activity 24,49 . For the stability experiments, 2 mg L −1 umbelliferone solutions (100 mL) were prepared either in distilled water or in a soil extract.…”

“…22 showed complete biodegradation of umbelliferone after incubation for 2 days. Nanotechnology can help circumvent some of these limitations associated with the use of natural products as agrochemicals by allowing the development of new tools to improve their effectiveness 21,23,24 . For example, some studies have shown that soil amendments, including certain nanoengineered additives, can greatly influence pesticide mobility and bioavailability, and consequently, the final pesticide efficacy 25–28 .…”

Biochar changes the bioavailability and bioefficacy of the allelochemical coumarin in agricultural soils

“…Soil dissipation of coumarin was very fast for both doses tested, which is typical of natural allelopathic compounds and is the main drawback for their potential use as biopesticides 50 . For this reason, strategies to increase their persistence in soils are vitally needed 8,9,40 …”

“…The use of different tools based on nanotechnology could overcome some of these limitations enhancing their effectiveness 6 . For instance, nanoengineered sorbents can be applied to soils to reduce the mobility of these compounds, 8,9 or nanoformulations of natural products can be prepared to protect them from premature degradation 10,11 . The application of adjuvants could be another strategy to improve the effectiveness of allelochemicals in soils.…”