Degradation Dynamics of Glyphosate in Different Types of Citrus Orchard Soils in China

Abstract

Glyphosate formulations that are used as a broad-spectrum systemic herbicide have been widely applied in agriculture, causing increasing concerns about residues in soils. In this study, the degradation dynamics of glyphosate in different types of citrus orchard soils in China were evaluated under field conditions. Glyphosate soluble powder and aqueous solution were applied at 3000 and 5040 g active ingredient/hm 2 , respectively, in citrus orchard soils, and periodically drawn soil samples were analyzed by high performance liquid chromatography. The results showed that the amount of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in soils was reduced with the increase of time after application of glyphosate formulations. Indeed, the amount of OPEN ACCESSMolecules 2015, 20 1162 glyphosate in red soil from Hunan and Zhejiang Province, and clay soil from Guangxi Province varied from 0.13 to 0.91 µg/g at 42 days after application of aqueous solution. Furthermore, the amount of glyphosate in medium loam from Zhejiang and Guangdong Province, and brown loam from Guizhou Province varied from less than 0.10 to 0.14 µg/g, while the amount of AMPA varied from less than 0.10 to 0.99 µg/g at 42 days after application of soluble powder. Overall, these findings demonstrated that the degradation dynamics of glyphosate aqueous solution and soluble powder as well as AMPA depend on the physicochemical properties of the applied soils, in particular soil pH, which should be carefully considered in the application of glyphosate herbicide.

AminoMethylPhosphonic acid (AMPA) in natural waters: Its sources, behavior and environmental fate

“…Conversely, Bergström et al (2011) found correlations between AMPA degradation rates and amount of OM, observing a half-life of 35 days in clay topsoil and days in subsoil. Concerning loam top soils, Simonsen et al (2008) calculated a DT50 of 32 days for AMPA, Zhang et al (2015) observed AMPA DT50 ranging between and days, and lastly Mamy et al (2005) observed 25-75 days.…”

Residue Dynamics and Risk Assessment of Prochloraz and Its Metabolite 2,4,6-Trichlorophenol in Apple

“…The relationship between prochloraz residues and time is C t = C 0 × e −kt , where C t (mg·kg −1 ) is the residue after time t, C 0 (mg·kg −1 ) is the initial residue, e is a mathematical constant, and k is the dissipation rate constant (d −1 ). This equation is widely used to assess the level of pesticides in agriproducts [ 27 , 28 ].…”

Eco-toxicity of water, soil, and sediment from agricultural areas of Kilombero Valley Ramsar wetlands, Tanzania

“…Sampling in the dry season may have overlapped with pesticide application before seedling, as measured glyphosate and AMPA concentrations were higher in samples from dry than from rainy season. Both have strong soil adsorptive characteristics due to their large organic carbon to water partition coefficient (Koc) up to 60,000 L/kg (Okada, Costa, and Bedmar 2016;Maqueda et al 2017;Erban et al 2018) and half-lives in soil of 42-44 days, depending on the physicochemical properties of the applied soils (Kollman and Segawa 1995;Zhang et al 2015). Tsui and Chu (2003) showed that the glyphosate-containing product Roundup® had a high toxicity to different trophic levels of aquatic organisms in the laboratory such as bacteria, algae, protozoa and zooplankton, whereby almost 50% of the effect could be attributed to the toxicity of the surfactant polyoxyethyleneamine (POEA) as complementary component of the product which has not been analyzed in this study.…”