Fate and Transport of Glyphosate and Aminomethylphosphonic Acid in Surface Waters of Agricultural Basins

US Geological Survey, Pearl, MS, USA.
Pest Management Science (Impact Factor: 2.69). 01/2012; 68(1):16-30. DOI: 10.1002/ps.2212
Source: PubMed


Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking.
Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route.
Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil.


Available from: Richard H. Coupe, Apr 21, 2015
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    • "equivalent basis and added to the glyphosate concentration to obtain the total extracted glyphosate (TEG) as follows (Coupe et al., 2011): "
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    ABSTRACT: Glyphosate (N-(phosphonomethyl) glycine) is a post-emergence, non-selective, foliar herbicide. Around 200 million liters of this herbicide are applied every year in Argentina, where the main agricultural practice is no-till (NT), accounting for 78.5% of the cultivated land. In this work, we studied the adsorption of glyphosate in different soils under long-term management (more than 16 years) of NT and conventional tillage (CT). Samples were taken from different regions of Argentina corresponding to: Paraná soil (PAR), a silty clay loam soil (b 37% clay), Manfredi (MAN) and Pergamino (PER), both silty loam soils (b26% clay). We found that the adsorption was very high in all the soils, and it was particularly influenced by the soil clay content and CEC and negatively related to pH and phosphorus. In general, the adsorption coefficient (Kf) was higher in the CT samples. We also studied the vertical transport of glyphosate in undisturbed columns (15 cm long) and compared the effect of NT and CT. Less than 0.24% of the applied pesticide leached in all soils. No significant difference was found between the total amount of leached glyphosate between soils or tillage practice. The highest glyphosate concentration (67.53% of the initially applied doses) was found in the top 5 cm of the columns. The strong retention of glyphosate to the soil matrix, as confirmed by the high Kf values obtained in the isotherm studies, was the dominant factor influencing glyphosate mobility through the soil profile.
    Geoderma 02/2016; 263. DOI:10.1016/j.geoderma.2015.09.009 · 2.77 Impact Factor
    • "AMPA (aminomethylphosphonic acid) is its main degradation product. Glyphosate mobility in the environment is supposed to be limited because of its high adsorption capacity in soils (Cheah et al. 1997; Vereecken 2005; Borggaard and Gimsing 2008), but some studies show that glyphosate may reach surface waters either by transport in dissolved form, or by particle-facilitated transport (Coupe et al. 2012; Aparicio et al. 2013). Analysis in drainage-water samples (Kjaer et al. 2005, 2011; Candela et al. 2010; Norgaard et al. 2014) or in leachates of soil-column experiments (Dousset et al. 2004; Landry et al. 2005) underscored the possible leaching of glyphosate and AMPA through the soil and thus the risk of groundwater contamination. "
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    ABSTRACT: Adsorption of the herbicide glyphosate and its main metabolite AMPA (aminomethylphosphonic acid) was investigated on 17 different agricultural soils. Batch equilibration adsorption data are shown by Freundlich adsorption isotherms. Glyphosate adsorption is clearly affected by equilibration concentrations, but the nonlinear AMPA adsorption isotherms indicate saturation of the adsorption sites with increasing equilibrium concentrations. pHCaCl2 (i.e. experimental pH) is the major parameter governing glyphosate and AMPA adsorption in soils. However, considering pHCaCl2 values, available phosphate amount, and amorphous iron and aluminium oxide contents by using a nonlinear multiple regression equation, obtains the most accurate and powerful pedotransfer rule for predicting the adsorption constants for these two molecules. As amorphous iron and aluminium oxide contents in soil are not systematically determined, we also propose a pedotransfer rule with two variables-pHCaCl2 values and available phosphate amount-that remains acceptable for both molecules. Moreover, the use of the commonly measured pHwater or pHKCl values gives less accurate results compared to pHCaCl2 measurements. To our knowledge, this study is the first AMPA adsorption characterization for a significant number of temperate climate soils.
    Environmental Science and Pollution Research 11/2015; DOI:10.1007/s11356-015-5796-5 · 2.83 Impact Factor
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    • "Glyphosate (N-[phosphonomethyl]glycine) is the most widely used herbicide globally in terms of treated area as well as total amount used (Coupe et al., 2012). It is the active compound of RoundUp 1 and, besides being applied in agriculture as weed control agent, glyphosate is also used to treat winter cover crops in order to obtain a better establishment of the subsequent spring crop and to artificially accelerate and synchronize ripening of various crops (Duke and Powles, 2009; Helander et al., 2012; Landbrugsrådgivning Syd, 2012). "
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    ABSTRACT: Glyphosate is extensively used for weed control and to ripen crops. Despite a number of studies on the direct effect of glyphosate on plants and soil organisms, only little is known about indirect effect of glyphosate on rhizosphere microbial communities, following the accelerated turnover of the fast-dying root biomass. In microcosms we studied the indirect effect of glyphosate on the microbial community in the rhizosphere of barley with phyllosphere application of glyphosate in comparison to leaving the plant intact or cutting off the shoot. Attempting to link the response of bacterial and protist communities to foliar application of glyphosate, we measured bacterial and protist abundance, diversity and physiological status, as well as soil organic carbon. Foliar application of glyphosate doubled bacterial abundance of the culturable fraction present in the rhizosphere compared to the other treatments with no effect on total abundance. Also the abundance of culturable protists increased as an effect of glyphosate and the bacterial genetic diversity as revealed by 16S rDNA DGGE analysis was affected. Overall, the results indicate that when barley leaves are treated with glyphosate, the availability of organic carbon in the rhizosphere of the dying roots is altered, which in turn may alter the bacterial and protist communities and their interactions. This can have implications for general soil carbon turnover processes and CO2 release in arable systems.
    Applied Soil Ecology 11/2015; DOI:10.1016/j.apsoil.2015.09.007 · 2.64 Impact Factor
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