Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins.
TL;DR: 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.
Abstract: BACKGROUND: 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 10000 Mg in 1992 to more than 80000 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 aminomethylphosphonicacid (AMPA) on a watershed scale is lacking. RESULTS: 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 andflow route. CONCLUSIONS: 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. c � 2011 Society of Chemical Industry
Citations
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TL;DR: Glyphosate is developmentally toxic to the zebrafish heart and alterations in the Mef2/mef2ca staining patterns during early cardiac patterning stages are found.
61 citations
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TL;DR: Results of long-lasting experiments indicate that glyphosate can markedly affect biological responses of marine invertebrates, and more efforts should be addressed at evaluating chronic or sub-chronic effects of such substances to Marine invertebrate species.
Abstract: Glyphosate is the active ingredient of numerous commercial formulations of herbicides applied in different sectors, from agriculture to aquaculture. Due to its widespread use around the world, relatively high concentrations of glyphosate have been detected in soil and aquatic environments. The presence of glyphosate in aquatic ecosystems has aroused the attention of researchers because of its potential negative effects on living organisms, both animals and plants. In this context, this review intends to summarize results of studies aimed at evaluating the effects of glyphosate (both as active ingredient and component of commercial formulations) on marine invertebrates. Generally, data obtained in acute toxicity tests indicate that glyphosate and its commercial formulations are lethal at high concentrations (not environmentally realistic), whereas results of long-lasting experiments indicate that glyphosate can markedly affect biological responses of marine invertebrates. Consequently, more efforts should be addressed at evaluating chronic or sub-chronic effects of such substances to marine invertebrate species.
61 citations
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TL;DR: This review summarizes methods used during the past 15 years for analysis of glyphosate and AMPA in water, plant materials and soil to facilitate environmental research needed to address the continuing concerns related to increasing glyphosate use.
Abstract: There is a need for simple, fast, efficient and sensitive methods of analysis for glyphosate and its degradate aminomethylphosphonic acid (AMPA) in diverse matrices such as water, plant materials and soil to facilitate environmental research needed to address the continuing concerns related to increasing glyphosate use. A variety of water-based solutions have been used to extract the chemicals from different matrices. Many methods require extensive sample preparation, including derivatization and clean-up, prior to analysis by a variety of detection techniques. This review summarizes methods used during the past 15 years for analysis of glyphosate and AMPA in water, plant materials and soil. The simplest methods use aqueous extraction of glyphosate and AMPA from plant materials and soil, no derivatization, solid-phase extraction (SPE) columns for clean-up, guard columns for separation and confirmation of the analytes by mass spectrometry and quantitation using isotope-labeled internal standards. They have levels of detection (LODs) below the regulatory limits in North America. These methods are discussed in more detail in the review.
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TL;DR: The present review summarizes the discovery, prevalence, chemical and physical properties, mode of action and effects in plants, glyphosate resistance and the environmental fate of glyphosate.
Abstract: Glyphosate is the most commonly-used herbicide in the world. The present review summarizes the discovery, prevalence, chemical and physical properties, mode of action and effects in plants, glyphosate resistance and the environmental fate of glyphosate. Numerous studies are reviewed that demonstrate that glyphosate may run off of fields where it is applied, while other studies provide evidence that plant roots can take up glyphosate. Non-target vegetation may be exposed to glyphosate in the root-zone, where it has the potential to remove aqueous glyphosate from the system. Further study on the effects of root-zone glyphosate on non-target vegetation is required to develop best management practices for land managers seeking to ameliorate the effects of root-zone glyphosate exposure.
59 citations
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...1 μg·L) to 86 μg·L [85]....
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TL;DR: This study is the first AMPA adsorption characterization for a significant number of temperate climate soils and proposes a pedotransfer rule with two variables—pHCaCl2 values and available phosphate amount—that remains acceptable for both molecules.
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.
59 citations
Cites background from "Fate and transport of glyphosate an..."
...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)....
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...…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)....
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References
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TL;DR: Glyphosate-based weed control products are among the most widely used broad-spectrum herbicides in the world and have been extensively investigated for their potential to produce adverse effects in nontarget organisms as discussed by the authors.
Abstract: Glyphosate-based weed control products are among the most widely used broad-spectrum herbicides in the world. The herbicidal properties of glyphosate were discovered in 1970, and commercial formulations for nonselective weed control were first introduced in 1974 (Franz et al. 1997). Formulations of glyphosate, including Roundup® Herbicide (RU)1 (Monsanto Company, St. Louis, MO), have been extensively investigated for their potential to produce adverse effects in nontarget organisms. Governmental regulatory agencies, international organizations, and others have reviewed and assessed the available scientific data for glyphosate formulations and independently judged their safety. Conclusions from three major organizations are publicly available and indicate RU can be used with minimal risk to the environment (Agriculture Canada 1991; USEPA 1993a; WHO 1994). Several review publications are available on the fate and effects of RU or glyphosate in the environment (Carlisle and Trevors 1988;Smith and Oehme 1992 ; Malik et al. 1989;Rueppel et al. 1977; Sullivan and Sullivan 1997;Forestry Canada, 1989). In addition, several books have been published about the environmental and human health considerations of glyphosate and its formulations (Grossbard and Atkinson 1985; Franz et al. 1997). In addition, RU and other glyphosate formulations have been selected for use in a number of weed control programs for state and local jurisdictions in the United States. Many of these uses require that ecological risk assessments be conducted in the form of Environmental Impact Statements or Environmental Assessments. These documents are comprehensive and specific to local use situations. Documents are available for risk assessments in Texas, Washington, Oregon, Pennsylvania, New York, Virginia, and other states (USDA 1989;USDA 1992;USDA 1996;USDA 1997;USDI 1989; Washington State DOT 1993).
883 citations
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TL;DR: The literature on pesticide losses in runoff waters from agricultural fields is reviewed in this paper, where the majority of commercial pesticides, total losses are 0.5%0 or less of the amounts applied, unless severe rainfall conditions occur within 1-2 weeks after application.
Abstract: The literature on pesticide losses in runoff waters from agricultural fields is reviewed. For the majority of commercial pesticides, total losses are 0.5%0 or less of the amounts applied, unless severe rainfall conditions occur within 1–2 weeks after application. Exceptions are the organochlorine insecticides, which may lose about 1% regardless of weather pattern because of their long persistence; and soil surface-applied, wettable-powder formulations of herbicides, which may lose up to 5%, depending on weather and slope, because of the ease of washoff of the powder.Pesticides with solubilities of 10 ppm or higher are lost mainly in the water phase of runoff, and erosion control practices will have little effect on such losses. Organochlorine pesticides, paraquat, and arsenical pesticides, however, are important cases of pesticides which are strongly adsorbed by sediments, and erosion control can be important in controlling losses of these compounds.The behavior and fate of pesticides in streams receiving runoff is generally not known. Information on such factors as time and distance of impact of a given runoff event, ability of local ecosystems to recover from transient pesticide concentrations, and dissipation or concentration processes in aquatic ecosystems will have to be obtained before “edge-of-field” pesticide losses can be related to water quality in receiving waters.
753 citations
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TL;DR: Glyphosate [N-(phosphonomethyl)glycine] was readily bound to kaolinite, illite, and bentonite clay and to charcoal and muck but not to ethyl cellulose as mentioned in this paper.
Abstract: Glyphosate [N-(phosphonomethyl)glycine] was readily bound to kaolinite, illite, and bentonite clay and to charcoal and muck but not to ethyl cellulose. Fe+++ and Al+++-saturated clays and organic matter adsorbed more glyphosate than Na+ or Ca+-saturated clays and organic matter. Glyphosate appears to be bound to the soil through the phosphonic acid moiety as phosphate in the soil competed with 14C-glyphosate for adsorption sites. Glyphosate mobility in the soil was very limited and was affected by pH, phosphate level, and soil type. The 14C-glyphosate was biodegraded in soil to 14CO2 possibly by co-metabolism. Potentiometric titrations of the compound gave pKa values of 2, 2.6, 5.6, and 10.6.
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TL;DR: Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit and the development and use of failsafe introgression barriers in crops with such linked genes is needed.
Abstract: Glyphosate [N-(phosphonomethyl) glycine]-resistant crops (GRCs), canola (Brassica napus L.), cotton (Gossypium hirsutum L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] have been commercialized and grown extensively in the Western Hemisphere and, to a lesser extent, elsewhere. Glyphosate-resistant cotton and soybean have become dominant in those countries where their planting is permitted. Effects of glyphosate on contamination of soil, water, and air are minimal, compared to some of the herbicides that they replace. No risks have been found with food or feed safety or nutritional value in products from currently available GRCs. Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit. Weed species in GRC fields have shifted to those that can more successfully withstand glyphosate and to those that avoid the time of its application. Three weed species have evolved resistance to glyphosate in GRCs. Glyphosate-resistant crops have greater potential to become problems as volunteer crops than do conventional crops. Glyphosate resistance transgenes have been found in fields of canola that are supposed to be non-transgenic. Under some circumstances, the largest risk of GRCs may be transgene flow (introgression) from GRCs to related species that might become problems in natural ecosystems. Glyphosate resistance transgenes themselves are highly unlikely to be a risk in wild plant populations, but when linked to transgenes that may impart fitness benefits outside of agriculture (e.g., insect resistance), natural ecosystems could be affected. The development and use of failsafe introgression barriers in crops with such linked genes is needed.
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TL;DR: In this paper, the Soil and Water Assessment Tool (SWAT) water quality model is designed to assess nonpoint and point source pollution and was recently modified for tile drainage.
Abstract: The presence of subsurface tile drainage systems can facilitate nutrient and pesticide transport, thereby contributing to environmental pollution. The Soil and Water Assessment Tool (SWAT) water quality model is designed to assess nonpoint and point source pollution and was recently modified for tile drainage. Over 25% of the nation's cropland required improved drainage. In this study, the model's ability to validate the tile drainage component is evaluated with nine years of hydrologic monitoring data collected from the South Fork watershed in Iowa, since about 80% of this watershed is tile drained. This watershed is a Conservation Effects Assessment Program benchmark watershed and typifies one of the more intensively managed agricultural areas in the Midwest. Comparison of measured and predicted values demonstrated that inclusion of the tile drainage system is imperative for obtaining a realistic watershed water balance. Two calibration/validation scenarios tested if the results differed in how the data set was divided. The optimum scenario results for the simulated monthly and daily flows had Nash-Sutcliffe efficiency (ENS) values during the calibration/validation (1995-1998/1999-2004) periods of 0.9/0.7 and 0.5/0.4, respectively. The second scenario results for the simulated monthly and daily flows had ENS values during the calibration/validation (1995-2000/2001-2004) periods of 0.8/0.5 and 0.7/0.2, respectively. The optimum scenario reflects the distribution of peak rainfall events represented in both the calibration and validation periods. The year 2000, being extremely dry, negatively impacted both the calibration and validation results. Each water budget component of the model gave reasonable output, which reveals that this model can be used for the assessment of tile drainage with its associated practices. Water yield results were significantly different for the simulations with and without the tile flow component (25.1% and 16.9%, expressed as a percent of precipitation). The results suggest that the SWAT2005 version modified for tile drainage is a promising tool to evaluate streamflow in tile-drained regions when the calibration period contains streamflows representing a wide range of rainfall events.
209 citations