Persistence Behavior of Penoxsulam Herbicide in Two Different Soils

An insight into the sorption kinetics of boscalid onto soils: Effect of general soil properties

Boscalid is a carboxamide fungicide widely used for crop protection, however owing to its high persistence, it is detected in high concentrations in various environments. Since the fate of such xenobiotics is strongly influenced by its interaction with soil components a better understanding of its adsorption onto soils of varying properties could allow the adjustment of its application in a given agro-ecological region to limit the consequent environmental burden. The present investigation was carried out to examine the kinetics of boscalid adsorption onto ten Indian soils of varying physico-chemical properties. Kinetic data of boscalid for all soils under investigation fitted well to both pseudo-first-order and pseudo-second-order kinetic models. However, based on the standard error of estimate (S.E._est.) values pseudo-first-order model was better for all soil samples, except one soil which had the lowest readily oxidizable organic carbon. Adsorption of boscalid by soils appeared to be controlled by the diffusion-chemisorption process while for soils especially rich in readily oxidizable organic carbon or clay + silt content the intra-particle diffusion process seemed to be more important. Stepwise regression of kinetic parameters on soil properties revealed that the inclusion of a set of some soil properties could help better prediction of adsorbed amounts of boscalid and kinetic constants. These findings may help assess the fate and possible transport of boscalid fungicide in different soils.

Effects of ecotoxicity of penoxsulam single and co-exposure with AgNPs on Eisenia fetida

Penoxsulam (PNX) and silver nanoparticles (AgNPs) are likely to coexist in soils due to continuous use. However, the ecotoxicity of PNX in earthworms and the effect of AgNPs on PNX toxicity are unknown. Therefore, the toxicity of PNX (0.05, 0.5, and 2.5 mg/kg) single and co-exposure with AgNPs (10 mg/kg) after 28 and 56 days on Eisenia fetida (E. fetida) was investigated from biochemical, genetic, histopathological, and transcriptomic aspects. The results showed that the low concentration of PNX (0.05PNX) had almost no effect on the biochemical level of E. fetida. However, the addition of AgNPs resulted in 0.05PNX causing E. fetida to produce excessive reactive oxygen species, and the activity of antioxidant and detoxification enzymes were interfered, resulting in lipid peroxidation and DNA damage. From the genetic level, even the lowest concentration of PNX can significantly interfere with the expression of functional genes, thus inducing oxidative stress and apoptosis and inhibited reproductive behavior in E. fetida. The integrated biomarker response results at the biochemical and genetic levels showed that the comprehensive toxicity of PNX and PNX + AgNPs on E. fetida was PNX dose-dependent. And the toxicity of all co-exposure groups was greater than that of the PNX only exposure groups. Furthermore, the addition of AgNPs significantly increased the damage of PNX on E. fetida intestinal tissue. Meanwhile, transcriptomic analysis showed that PNX + AgNPs had a greater effect on E. fetida than PNX single, and multiple pathways related to oxidative stress, inflammation, and cellular process regulation were disturbed. These results provide a basis for comprehensive evaluation of the ecotoxicity of PNX and confirm that the AgNPs does increase the ecotoxicity of PNX in soil environment.

Persistence of atrazine and trifluralin in a clay loam soil undergoing different temperature and moisture conditions

Dissipation kinetics of atrazine and trifluralin in a clay loam soil was investigated in a laboratory incubation experiment under different temperature and moisture conditions. The soil was spiked with diluted atrazine and trifluralin concentrations at 4.50 and 4.25 mg/kg soil, respectively, the moisture content adjusted to 40, 70, and 100% of field capacity (FC) and then incubated in three climatic chambers at 10, 20, and 30 °C. For each of the herbicides, soil samples were collected at 0, 7, 21, 42, 70, and 105 days and analysed by Gas Chromatography-Electron Capture Detector (GC-ECD). A stochastic gamma model was used to model the dissipation of herbicides from the clay loam soil by incorporating environmental factors as covariates to determine half-life and days to complete dissipation. Results showed that temperature played a greater role on atrazine persistence than soil moisture; while the interaction effect of temperature and moisture was significant on the persistence of trifluralin over time. Atrazine dissipated more rapidly at 30 °C compared to 10 and 20 °C, with a half-life of 7.50 days and 326.23 days to reach complete dissipation. Rapid loss of trifluralin was observed at 70% moisture content when incubated at 30 °C, with a half-life of 5.80 days and 182.01 days to complete dissipation. It was observed that the half-life of both herbicides tended to double with every 10 °C decreases of temperature over the range tested. The model indicated that both atrazine and trifluralin have the potential to persist in clay loam soil for several years at temperature ≤20 °C; which could potentially affect following crops in rotation.

Evaluation of the behaviour of propoxycarbazone herbicide in soils and water under different conditions. Post-targeted study

The aim of this study is to understand the levels and behaviour of the herbicide propoxycarbazone in environmental compartments, which are poorly characterized considering degradation products that might reach either surface water as groundwater or soil samples. To this end, an analytical method, based on ultra-high performance liquid chromatography (UHPLC) coupled with Orbitrap mass spectrometry (MS), has been developed to determine the parent compound and its transformation products in soils and water. In addition, a set of laboratory trials has been designed to address the dissipation process of propoxycarbazone formulation in both environmental substrates. The study revealed that the dissipation in water followed a first order kinetics and a non-linear "First Order Multi Compartment" model (FOMC) to soil. Relevant advances have been also achieved in terms of the analytical methodology, as far as the UHPLC-Orbitrap-MS technique allows the development of a retrospective screening of pesticide transformation products in water and soils. For this purpose, an accurate-mass database has been built and used for the post-run screening analysis with 9 transformation products. Photodegradation presumably plays an important role in the dissipation of propoxycarbazone. The results of UHPLC-Orbitrap-MS revealed that four transformation products were formed during the degradation process of the herbicide.

Identification and Characterization of Herbicide Penoxsulam Transformation Products in Aqueous Media by UPLC-QTOF-MS

Photodegradation is an important non-biodegradation process of pesticide degradation in aquatic environments. In this study, the effect of different forms of nitrogen on the photodegradation kinetics of penoxsulam was investigated. The photodegradation of penoxsulam was accelerated by NO^3- and NO^2- but was not affected by NH⁴⁺. Ultra-high-performance liquid chromatography coupled with time-of-flight mass spectrometry was used to separate and identify the transformation products (TPs)converted by photodegradation of penoxsulam in an aqueous solution under UV-Vis (290-800 nm) irradiation. Seven major transformation products were identified based on mass spectral data. The structure was determined by elemental composition calculations, comparison of structural analogs, and existing literature. The main pathways of photodegradation were found to be sulfonamide bond cleavage, rearrangement, triazole ring cleavage, and hydroxylation. These findings are critical to elucidate the environmental fate of penoxsulam in aquatic ecosystems and provide a basis for further environmental risk assessment.

Effect of Soil Type, Moisture and Temperature on the Dissipation of Penoxsulam in Soil Under Laboratory Conditions

A comprehensive study was conducted to evaluate the effect of concentration, moisture conditions, temperature and soil type on dissipation of penoxsulam in soil under laboratory conditions. Penoxsulam residues from the soil were extracted using matrix solid phase dispersion method and quantified using high performance liquid chromatography with UV detector at 230 nm. Dissipation followed first order kinetics and penoxsulam dissipated within 60 days in all the treatments with half-life varying from 12.60 to 30.08 days. Soil type greatly influenced the dissipation of penoxsulam and it was found to be slower in clay loam followed by loam, sandy loam and loamy sand soil. However, irrespective of soil type, dissipation of penoxsulam increased with increase in moisture content of soil and temperature.