Persistence of acetochlor, atrazine, and S‐metolachlor in surface and subsurface horizons of 2 typic argiudolls under no‐tillage

Abstract

Variations in soil properties with depth strongly influence the degradation and persistence of herbicides, underlining the importance of studying these processes in soil horizons with distinctively different properties. The persistence of the herbicides acetochlor, atrazine, and S-metolachlor was measured in samples of the A, B, and C horizons of 2 Typic Argiudolls from Argentina under no-till management. The soils studied differed in soil organic carbon (OC) content, pH, particle size distribution, and structure. Quantification of herbicides in soil was done through high-performance liquid chromatography with diode array detector. There were interactions of herbicide × horizon (p < 0.01) that resulted in degradation rates (k) of all herbicides decreasing, and their corresponding dissipation half-life (DT50) values increasing, with soil depth. Herbicide persistence across all soils and horizons ranged from 15 to 73 d for acetochlor, 13 to 29 d for atrazine, and 82 to 141 d for S-metolachlor, which had significantly (p < 0.01) greater persistence than atrazine and acetochlor. The DT50 values of herbicides were negatively correlated with the contents of OC (correlation coefficients ranging from -0.496 to -0.773), phosphorus (-0.427 to -0.564), and nitrogen-nitrate (-0.507 to -0.662), and with microbial activity (-0.454 to -0.687) and the adsorption coefficient (-0.530 to -0.595); DT50s were positively correlated with pH (0.366 to 0.648). Adsorption was likely the most influential process in determining persistence of these herbicides in surface and subsurface horizons. The present study can potentially improve the prediction of the fate of acetochlor, atrazine, and S-metolachlor in soils because it includes much needed information on the degradation of the herbicides in subsurface horizons. Environ Toxicol Chem 2017;36:3065-3073. © 2017 SETAC.

Metribuzin and 2,4-D as potential herbicides for weed management in sorghum [Sorghum bicolor (L) Moench]

“…Adequate rainfall after application of pre-emergence herbicide may also lead to chemical loss through runoff or leaching. Comparing persistence of three herbicides under no tillage, Bedmar et al (2017) found S- metolachlor to have significantly greater persistence of 82 to 141 days compared to atrazine whose persistence ranged from 13 to 29 days. The persistence varies depending on herbicide composition, soil type and rate of breakdown.…”

Agrochemical leaching reduction in biochar‐amended tropical soils of Belize

“…Therefore, the high organic matter and clay content explained why the herbicides had a higher sorption to clay loam than the other soils. Notably, there is a positive correlation between herbicide absorption and organic matter and clay content (Baskaran, 1994;Bedmar et al, 2017;Nemeth-Konda, Füleky, Morovjan, & Csokan, 2002;Weber, Wilkerson, & Reinhardt, 2004), but there is generally a stronger correlation between organic matter and sorption than clay content and sorption (Kookana et al, 1998;Weber et al, 2004). In addition, although organic matter and clay content have a dominant influence on sorption, pH may also affect sorption (Fontecha-Cámara et al, 2007).…”

“…When applied to soil, the agrochemical fate is determined by mixing/dissolution in the soil water, sorption onto soil particles, microbial degradation, and partitioning into gas phase and volatilization into the air, therefore posing a potential soil, air and water pollution risk (Liyanage et al, 2006;Bedmar et al, 2017;Pan & Chu, 2017a). By amending soils with biochar, agrochemical leaching and volatilization can be reduced by mechanisms such as increased agrochemical sorption, which retains agrochemicals in the bioactive topsoil layer for microbial degradation.…”

“…However, if improperly managed, agrochemicals can leach through the soil and contaminate drinking, surface and groundwater (Fontecha-Cámara, López-Ramón, Alvarez-Merino, & Moreno-Castilla, 2007;Pan & Chu, 2017a). Therefore, the risk to non-target sites of agrochemical contamination is dependent on the physicochemical structure of the compound, properties of the soil, climatic conditions, land structure and agrochemical management practices (Bedmar, Gimenez, Costa, & Daniel, 2017;Liyanage, Watawala, Aravinna, Smith, & Kookana, 2006;Pan & Chu, 2017a). As such, many countries regulate the registration and use of chemicals in agriculture and these regulations require the applicant to demonstrate no unacceptable risk to the environment following the proposed use (e.g., Regulation 1107/2009 in the EU, FIFRA 7.…”

Efficient Removal of Butachlor and Change in Microbial Community Structure in Single-Chamber Microbial Fuel Cells

“…The biodegradation of organic pollutants was demonstrated as a feasible and safe treatment technology [1,5,6]. However, the degradation efficiency is seriously limited in anoxic environments, e.g., groundwater, sediment, and subsoil [7,8]. Moreover, butachlor and alachlor are slower to degrade than acetochlor and metolachlor, since it is possible that the electronic effect of the long-chain alkyl substituents alters the susceptibility of the benzene ring [9].…”