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
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TL;DR: In this paper , the authors demonstrated that GBH Roundup® LB plus has a negative effect on embryonic development of the South African clawed frog Xenopus laevis, leading to smaller eyes, brains and cranial cartilages in comparison to untreated embryos.
8 citations
TL;DR: Except for ephemeral effects, glyphosate applications appeared not to affect the function of the BS and RS exoenzymes under conventional tillage or no-till, and negative correlations between C:P and N:P nutrient ratios and nutrient acquisition ratios underscored the inverse relation between soil nutrient status and microbial community exoenzyme activities.
Abstract: BACKGROUND
We report results of the last two years of a 7-year field experiment designed to test the null hypothesis: applications of glyphosate on glyphosate resistant (GR) and non-resistant (nonGR) corn (Zea mays L.) under conventional tillage and no-till would have no effect on soil exoenzymes and microbial activity.
RESULTS
Bulk soil (BS) and rhizosphere soil (RS) macronutrient ratios were not affected by either GR or nonGR corn, or glyphosate applications. Differences observed between exoenzyme activities were associated with tillage rather than glyphosate applications. In 2013 nutrient acquisition ratios for bulk and rhizosphere soils indicated P limitations, but sufficient assimilable N. In 2014 P limitations were observed for bulk and rhizosphere soils, in contrast to balanced C and N acquisition ratios in rhizosphere soils. Stoichiometric relationships indicated few differences between glyphosate and non-glyphosate treatments. Negative correlations between C:P and N:P nutrient ratios and nutrient acquisition ratios underscored the inverse relation between soil nutrient status and microbial community exoenzyme activities.
CONCLUSIONS
Inconsistent relationships between microbial community metabolic activity and exoenzyme activity indicated an ephemeral effect of glyphosate on BS exoenzyme activity. Except for ephemeral effects, glyphosate applications appeared not to affect the function of the BS and RS exoenzymes under conventional tillage or no-till.
8 citations
TL;DR: In this paper , a review of glyphosate-based herbicide use in the environment, potential risks to human and ecological health, and various maximum residual limits for crops as suggested by international organizations is presented.
Abstract: The use of synthetic molecules to achieve specific goals is steadily increasing in the environment, and these molecules adversely impact human health and ecosystem services. Considering the adverse effects, a better understanding of how these molecules behave in the environment and their associated risks is necessary to keep their use acceptably limited. To meet the demands of farmers and combat weed problems, woodlands and farmlands are sprayed with agrochemicals, primarily glyphosate-based herbicides. Farmers increasingly embrace these herbicides containing glyphosate. Glyphosate and aminomethylphosphonic acid (AMPA), a key metabolite of glyphosate, have been reported as toxicological concerns when they become more prevalent in the food chain. The chemical glyphosate has been linked to various health issues in humans and other living organisms, including endocrine disruption, reproductive issues, tumours, non-Hodgkin lymphomas, and liver, heart, and blood problems. Therefore, the current review aims to compile data on glyphosate-based herbicide use in the environment, potential risks to human and ecological health, and various maximum residual limits for crops as suggested by international organizations. As a result, regulatory agencies can advise glyphosate users on safe usage practices and synthesize herbicides more efficiently.
8 citations
TL;DR: In this article , the authors compared the influence of environmentally relevant concentrations of AMPA (from 0.07 to 3.57 μg l−1) on the relation between developmental traits and oxidative status markers known to alter homeostasis when unbalanced (superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), thiols and ratios thereof).
8 citations
TL;DR: In this article, the authors performed four high-frequency sampling campaigns (from 2015 to 2017) following controlled spray applications on an experimental perennial grass field site with wetness-prone marginal soils, monitoring dissolved glyphosate concentrations in the outflow (runoff and shallow drainage) using liquid chromatography-mass spectrometry and enzyme-linked immunosorbent assays.
Abstract: Recent environmental surveys report widespread detections of the herbicide glyphosate [N-(phosphonomethyl)glycine] in surface waters, despite its strong immobilization and rapid biodegradation in soils. We performed four high-frequency sampling campaigns (from 2015 to 2017) following controlled spray applications on an experimental perennial grass field site with wetness-prone marginal soils. We monitored dissolved glyphosate concentrations in the outflow (runoff and shallow drainage) using liquid chromatography–mass spectrometry and enzyme-linked immunosorbent assays. Rainfall-triggered outflow events occurred between 3 and 13 days following spray application. Outflow concentrations varied widely from nondetectable levels to 90 μg L–1, peaking during the first significant outflow event in each campaign and diminishing as flows subsided. Subsequent outflow peaks caused concentrations to increase again but to a lesser extent. Cumulative mass efflux in outflow across the different campaigns ranged from 0.06...
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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
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
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.
444 citations
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.
387 citations
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