Infiltration of Acetochlor and Two of Its Metabolites in Two Contrasting Soils

Abstract

To obtain data concerning the risk of leaching of acetochlor (2-chloro-2'-methyl-6'-ethyl-N-ethoxymethyl-acetanilide) and its major metabolites, ethanesulfonic acid (ESA) and oxanilic acid (OA), to ground water, we studied the fate of these products in two different soil types (luvisol and calcisol) under the same weather conditions. The metabolites were detected in the soils as early as 7 d after application, indicating a rapid onset of acetochlor degradation. Ethanesulfonic acid was predominant over OA in the calcisol, regardless of time or depth, whereas the ESA to OA ratio varied with both time and depth in the luvisol. The maximum depths at which they were detected were 60 to 70 and 10 to 20 cm for ESA and OA, respectively, in the luvisol, and 60 to 70 cm (maximum depth sampled) and 30 to 40 cm for ESA and OA, respectively, in the calcisol. Acetochlor was still detected in the surface layer of the two soils 344 d after its application, although the molecule was partially leached. The maximum depths at which acetochlor was detected (60-70 cm in the luvisol and 50-60 cm [maximum depth sampled] in the calcisol) were recorded during the first sampling 7 d after application. Acetochlor was not detected on later dates below the 30- to 40-cm layer in the calcisol or the 5- to 10-cm layer in the luvisol. The greater preferential flow in the luvisol, which would have favored leaching, might partially explain why the mass balances done 7 d after application were lower in the luvisol (approximately 26%) than in the calcisol (approximately 45%).

Acetochlor sorption and degradation in limestone subsurface and aquifers

“…But this was not evident (Fig. 1A), although it is reasonable to assume that acetochlor has leached through the topsoil to at least 0.6 mbs 21. This is in line with the conclusion of KotoulaSyka et al 47 that acetanilides do not induce microbial adaptation.…”

“…The full mineralisation pathway for acetochlor is not yet established, but the most common metabolites are acetochlor ethanesulfonic acid (ESA) and acetochlor oxanilic acid (OA), both formed under aerobic conditions, and other metabolites have also been reported 4, 16, 17. The two major acetochlor metabolites (ESA and OA) are detected more frequently and in higher concentrations than the parent compound, and ESA more frequently and often in higher concentrations than OA 7, 11, 13, 18–22. Metabolites can be more mobile, persistent and toxic than their parent compounds, and, as little is known about ESA and OA, these should be taken into account when considering the fate of pesticides, e.g.…”

Analysis of metolachlor ethane sulfonic acid (MESA) chirality in groundwater: A tool for dating groundwater movement in agricultural settings

“…After application, metolachlor is readily transported into the soil where it is transformed into several compounds, the most abundant being, metolachlor ethane sulfonic acid (2-[(2-ethyl-6-methylphenyl)(2-methoxy-1-methylethyl)amino]-2-oxoethanesulfonic acid, MESA) (Baran and Gourcy, 2013;Bayless et al, 2008;White et al, 2010). MESA can be found in groundwater wherever metolachlor has been used and it appears to be quite stable in groundwater (Baran et al, 2004;Barbash et al, 1999;Bayless et al, 2008;Denver et al, 2010;Domagalski et al, 2008;Huntscha et al, 2008;Kalkhoff et al, 2012;Krutz et al, 2006;Rebich et al, 2004;Hancock et al, 2008).…”

A multiphasic characterization of the impact of the herbicide acetochlor on freshwater bacterial communities

“…Following land application, acetochlor has been shown to exhibit substantial off-site movement to natural waters via overland runoff and leaching (Ferenczi et al, 2002;Baran et al, 2004). The established negative impacts of acetochlor exposure to aquatic organisms combined with the importance of bacteria consortia to freshwater food chain processes such as decomposition and nutrient cycling, warranted an investigation of the impacts of acetochlor on freshwater microbial communities.…”

“…ESA is likely a by-product of glutathione conjugation occurring in plants, algae and microorganisms (Kalkhoff et al, 1998). The movement of acetochlor and its transformation products is mediated through several pathways including leaching, soil erosion (Baran et al, 2004) and surface runoff, which has been shown to facilitate the movement of up to 1% of applied acetochlor following natural rainfall conditions (Ferenczi et al, 2002). As a result of these transport mechanisms, it is estimated that up to 96% of freshwater streams in agricultural environments contain detectable quantities of acetochlor (Kolpin et al, 1996;Battaglin et al, 2000;Rebich et al, 2004).…”