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: Glyphosate will likely remain the most widely applied pesticide worldwide for years to come, and interest will grow in quantifying ecological and human health impacts, according to published global pesticide use data.
Abstract: Accurate pesticide use data are essential when studying the environmental and public health impacts of pesticide use. Since the mid-1990s, significant changes have occurred in when and how glyphosate herbicides are applied, and there has been a dramatic increase in the total volume applied. Data on glyphosate applications were collected from multiple sources and integrated into a dataset spanning agricultural, non-agricultural, and total glyphosate use from 1974–2014 in the United States, and from 1994–2014 globally. Since 1974 in the U.S., over 1.6 billion kilograms of glyphosate active ingredient have been applied, or 19 % of estimated global use of glyphosate (8.6 billion kilograms). Globally, glyphosate use has risen almost 15-fold since so-called “Roundup Ready,” genetically engineered glyphosate-tolerant crops were introduced in 1996. Two-thirds of the total volume of glyphosate applied in the U.S. from 1974 to 2014 has been sprayed in just the last 10 years. The corresponding share globally is 72 %. In 2014, farmers sprayed enough glyphosate to apply ~1.0 kg/ha (0.8 pound/acre) on every hectare of U.S.-cultivated cropland and nearly 0.53 kg/ha (0.47 pounds/acre) on all cropland worldwide. Genetically engineered herbicide-tolerant crops now account for about 56 % of global glyphosate use. In the U.S., no pesticide has come remotely close to such intensive and widespread use. This is likely the case globally, but published global pesticide use data are sparse. Glyphosate will likely remain the most widely applied pesticide worldwide for years to come, and interest will grow in quantifying ecological and human health impacts. Accurate, accessible time-series data on glyphosate use will accelerate research progress.
1,153 citations
TL;DR: GBHs are the most heavily applied herbicide in the world and usage continues to rise; Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions and regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science.
Abstract: The broad-spectrum herbicide glyphosate (common trade name “Roundup”) was first sold to farmers in 1974. Since the late 1970s, the volume of glyphosate-based herbicides (GBHs) applied has increased approximately 100-fold. Further increases in the volume applied are likely due to more and higher rates of application in response to the widespread emergence of glyphosate-resistant weeds and new, pre-harvest, dessicant use patterns. GBHs were developed to replace or reduce reliance on herbicides causing well-documented problems associated with drift and crop damage, slipping efficacy, and human health risks. Initial industry toxicity testing suggested that GBHs posed relatively low risks to non-target species, including mammals, leading regulatory authorities worldwide to set high acceptable exposure limits. To accommodate changes in GBH use patterns associated with genetically engineered, herbicide-tolerant crops, regulators have dramatically increased tolerance levels in maize, oilseed (soybeans and canola), and alfalfa crops and related livestock feeds. Animal and epidemiology studies published in the last decade, however, point to the need for a fresh look at glyphosate toxicity. Furthermore, the World Health Organization’s International Agency for Research on Cancer recently concluded that glyphosate is “probably carcinogenic to humans.” In response to changing GBH use patterns and advances in scientific understanding of their potential hazards, we have produced a Statement of Concern drawing on emerging science relevant to the safety of GBHs. Our Statement of Concern considers current published literature describing GBH uses, mechanisms of action, toxicity in laboratory animals, and epidemiological studies. It also examines the derivation of current human safety standards. We conclude that: (1) GBHs are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science. We offer a series of recommendations related to the need for new investments in epidemiological studies, biomonitoring, and toxicology studies that draw on the principles of endocrinology to determine whether the effects of GBHs are due to endocrine disrupting activities. We suggest that common commercial formulations of GBHs should be prioritized for inclusion in government-led toxicology testing programs such as the U.S. National Toxicology Program, as well as for biomonitoring as conducted by the U.S. Centers for Disease Control and Prevention.
638 citations
Cites background from "Fate and transport of glyphosate an..."
...GBHs contaminate drinking water via rainwater, surface runoff and leaching into groundwater, thereby adding drinking water, bathing, and washing water as possible routine exposure pathways [48, 54, 55]....
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TL;DR: It is hypothesized that the selection pressure for glyphosate-resistance in bacteria could lead to shifts in microbiome composition and increases in antibiotic resistance to clinically important antimicrobial agents, which would have an impact on plant, animal and human health.
571 citations
TL;DR: In this paper, a comprehensive assessment of the environmental occurrence of glyphosate and aminomethylphosphonic acid (AMPA) in the United States conducted to date, summarizing the results of 3,732 water and sediment and 1,018 quality assurance samples collected between 2001 and 2010 from 38 states.
Abstract: Glyphosate use in the United States increased from less than 5,000 to more than 80,000 metric tons/yr between 1987 and 2007. Glyphosate is popular due to its ease of use on soybean, cotton, and corn crops that are genetically modified to tolerate it, utility in no-till farming practices, utility in urban areas, and the perception that it has low toxicity and little mobility in the environment. This compilation is the largest and most comprehensive assessment of the environmental occurrence of glyphosate and aminomethylphosphonic acid (AMPA) in the United States conducted to date, summarizing the results of 3,732 water and sediment and 1,018 quality assurance samples collected between 2001 and 2010 from 38 states. Results indicate that glyphosate and AMPA are usually detected together, mobile, and occur widely in the environment. Glyphosate was detected without AMPA in only 2.3% of samples, whereas AMPA was detected without glyphosate in 17.9% of samples. Glyphosate and AMPA were detected frequently in soils and sediment, ditches and drains, precipitation, rivers, and streams; and less frequently in lakes, ponds, and wetlands; soil water; and groundwater. Concentrations of glyphosate were below the levels of concern for humans or wildlife; however, pesticides are often detected in mixtures. Ecosystem effects of chronic low-level exposures to pesticide mixtures are uncertain. The environmental health risk of low-level detections of glyphosate, AMPA, and associated adjuvants and mixtures remain to be determined.
388 citations
Cites background from "Fate and transport of glyphosate an..."
...…by a series of studies (Scribner et al., 2003, 2007; Kolpin et al., 2004, 2006; Battaglin et al., 2005, 2009; Baker et al., 2006; McCarthy et al., 2011; Coupe et al., 2012), most, but not all of which were designed to determine the fate of glyphosate and AMPA or other pesticides in the environment....
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...Coupe et al. (2012) also suggest that the %AMPA values should increase with increases in drainage area....
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...Coupe et al. (2012) suggest that the timing of rainfall runoff events relative to glyphosate and the amount of glyphosate and AMPA in the soil reservoir from previous applications controls %AMPA values in surface water....
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TL;DR: It was demonstrated that glyphosate and AMPA are present in soils under agricultural activity, and it was found that in stream samples the presence of glyphosate and aminomethylphosphonic acid is relatively more frequent in suspended particulate matter and sediment than in water.
383 citations
Cites background from "Fate and transport of glyphosate an..."
...…transport of glyphosate and AMPA in streams located in United States show that glyphosate and AMPA have been frequently detected in surface waters of agricultural basins where it is used and their concentrations are influenced by source, hydrology and water movement pathways (Coupe et al., 2012)....
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...Recently, studies about the transport of glyphosate and AMPA in streams located in United States show that glyphosate and AMPA have been frequently detected in surface waters of agricultural basins where it is used and their concentrations are influenced by source, hydrology and water movement pathways (Coupe et al., 2012)....
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References
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TL;DR: A conservation practice inventory for the South Fork of the Iowa River, 85% in corn (Zea mays L.) and soybean [Glycine max L. (Merr.)] rotations, showed only 7% of cropland was managed using no-tillage.
Abstract: Documenting the types and extent of conservation practices in a watershed is necessary to determine their water quality impacts. A conservation practice inventory for the South Fork of the Iowa River, 85% in corn (Zea mays L.) and soybean [Glycine max L. (Merr.)] rotations, showed only 7% of cropland was managed using no-tillage. About 30% of cropland receives manure annually, prior to corn. Surface residue following soybean was usually inadequate ( 34% highly erodible land, subject to USDA conservation compliance, indeed had erosion-control practices installed. Grassed waterways and riparian buffers were common edge-of-field practices, and highly erodible land fields near streams often had multiple practices and rotations including third crops. Yet, while most conservation practices are aimed at controlling runoff, tile drainage is the dominant hydrologic pathway. Resource management systems that address tile drainage as the primary route of nutrient loss need to be developed and encouraged. Better targeting of this pathway could include practices such as nutrient removal wetlands.
64 citations
TL;DR: In this paper, the authors measured batch and column experiments were performed using two soils collected from the Maresme area near Barcelona, Spain, and measured batch sorption coefficients ranged from 93 to 154, suggesting that it is strongly bound to soil.
55 citations
TL;DR: In this article, a case study was designed in order to rank three alternative herbicides according to their exposure to surface waters in an uncultivated Finnish field (ca. 3500 m2, slope).
53 citations
TL;DR: Capel et al. as mentioned in this paper found that the highest concentrations of pesticides and nutrients were detected in samples of tile-drain water, overland flow, and water from Leary Weber Ditch.
Abstract: Leary Weber Ditch Basin, Hancock County, Indiana, is one of seven first-order basins selected from across the United States as part of the Agricultural Chemicals: Source, Transport, and Fate study conducted by the National Water-Quality Assessment Program of the U.S. Geological Survey. The nationwide study was designed to increase the understanding of the links between the sources of water and agricultural chemicals (nutrients and pesticides) and the transport and fate of these chemicals through the environment. Agricultural chemicals were detected in Leary Weber Ditch and in every associated hydrologic compartment sampled during 2003 and 2004. Pesticides were detected more frequently in samples collected from overland flow and from the ditch itself and less frequently in ground-water samples. The lowest concentrations of pesticides and nutrients were detected in samples of rain, soil water, and ground water. The highest concentrations of pesticides and nutrients were detected in samples of tile-drain water, overland flow, and water from Leary Weber Ditch. Samples collected from the tile drain, overland flow and Leary Weber Ditch soon after chemical applications to the fields and coincident with rainfall and increased streamflow had higher concentrations of pesticides and nutrients than samples collected a longer time after the chemicals were applied. A mass-balance mixing analysis based on potassium concentrations indicated that tile drains are the primary contributor of water to Leary Weber Ditch, but overland flow is also an important contributor during periods of high-intensity rainfall. When maximum rainfall intensity was 0.5 inches per hour or lower, overland flow contributed about 10 percent and tile drains contributed about 90 percent of the flow to Leary Weber Ditch. When maximum rainfall intensity was 0.75 inches per hour or greater, overland flow contributed about 40 percent and tile drains contributed about 60 percent of the flow to the ditch. Ground-water flow to Leary Weber Ditch was negligible. Tile drains are an important agricultural-chemical transport path to Leary Weber Ditch, based on the hydrologic contributions of overland flow and tile drains to the ditch. Overland flow is also an important agricultural-chemical transport pathway during high-intensity rainfall; however, storms with high-intensity rainfall are sporadic throughout the year. Tile drains and the soil water moving to the tile drains are the primary transport pathway for agricultural-chemical transport to Leary Weber Ditch during most storms as well as between storms. Introduction Leary Weber Ditch Basin in Hancock County, Indiana, is one of seven first-order basins selected from across the United States as part of the Agricultural Chemicals: Source, Transport, and Fate Team (ACT) study (Capel and others, 2004) conducted by the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS). The goal of the ACT study is to assess the fate and transport of chemicals applied to crops in agricultural basins across the Nation. Chemicals selected for nationwide ACT study include nutrients (nitrogen and phosphorus), major ions, and about 43 commonly used pesticides and 39 degradation products (including triazine herbicides such as atrazine and simazine, acetanilide herbicides such as acetochlor and metolachlor, and organophosphorus insecticides such as chlorpyrifos and diazinon). Because the herbicide glyphosate is so important in the Midwest, glyphosate and its degradate aminomethylphosphonic acid (AMPA) also were selected for analysis in the Leary Weber Ditch study in 2004 as part of the USGS Toxic Substances Hydrology Program. The basins in the ACT study represent a variety of agricultural settings with different crop types and agricultural practices related to tillage, irrigation, artificial drainage, and chemical use, as well as a range of landscapes with different geology, soils, topography, climate, and hydrology (Capel and others, 2004). Leary Weber Ditch Basin was selected for study because it is typical of an artificially drained (subsurface tile drains) Midwestern basin with corn and soybean row cropping. In areas with poorly drained soils, tile drains are used to Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04 By Nancy T. Baker, Wesley W. Stone, John T. Wilson, and Michael T. Meyer facilitate access to and cultivation of agricultural land. During the 1980s, the U.S. Department of Agriculture (USDA) estimated that approximately 50 percent of all cropland in Indiana was drained; tiles drain approximately 70 percent of that cropland. The USDA estimated that Indiana ranked second in the U.S. in total land area where artificial surface and subsurface drainage is used (U.S. Department of Agriculture, 1987). The ACT study is designed to increase the understanding of the links between the sources of water and agricultural chemicals (nutrients and pesticides) and the fate and transport of these chemicals through the environment. Understanding the fate and transport of these chemicals in the study basins may help predict the fate and transport of agricultural chemicals in other agricultural areas. This information will help managers target the implementation of best management practices to those hydrologic compartments that are the most conducive to the transport of agricultural chemicals. Purpose and Scope This report documents the occurrence of agricultural chemicals in Leary Weber Ditch and in the major hydrologic compartments of the Leary Weber Ditch Basin during 2003 and 2004. Hydrologic compartments that contribute water and agricultural chemicals to Leary Weber Ditch are rain water, overland-flow water, soil water, tile-drain water, and ground water. Water samples were collected during four storms in 2003 and three storms in 2004 from the Tile Drain, Overland Flow, and Leary Weber Ditch sites. In addition, stable-flow samples were collected between storms at the Tile Drain and Leary Weber Ditch sites. Weekly composite rain samples were collected for 13 weeks in 2003 and 2004. Soil-water and ground-water samples were collected at selected times during 2003 and 2004. The samples were analyzed for selected pesticides, nutrients, and major ions. This report also describes the transport of water and chemicals from the major hydrologic compartments to Leary Weber Ditch based on a mass-balance mixing analysis and analyses of hydrologic and chemical data from each of the hydrologic compartments. Description of Basin and Sampling Sites Leary Weber Ditch is a 2.73 mi intensively farmed drainage basin dominated by poorly drained soils in Hancock County, east-central Indiana (fig. 1). The USGS maintains streamflow gaging station 03361638, Leary Weber Ditch at Mohawk, IN (hereafter referred to as the gaging station). Agriculture is the principal land use, with 87 percent of the total land area in row crops. Leary Weber Ditch is an intermittent stream and a tributary to Sugar Creek. The ditch has been dredged along much of its reach to facilitate drainage of the shallow water table. Successful farming requires lowering the water table and removing ponded water by artificially draining the fields through tiles. Flow in Leary Weber Ditch is sustained primarily from tile-drain contributions. Large changes in flow are tied to snowmelt and rainfall, with flow diminishing quickly between periods of precipitation. A more complete description of the basin can be found in Lathrop (2006). Tile-drain systems are extensive in the basin; field reconnaissance showed 58 tile-drain outlets along the 2.86-mi length of Leary Weber Ditch. This number of outlets is conservative because 0.3 mi of the ditch was not accessible during the reconnaissance. The drains typically are installed 3 to 4 ft below the land surface, with an average outlet spacing of 200 ft. Tile-drain outlets represent individual tiles or collector tiles that combine discharge water from a network of tiles that may drain several fields. Approximate locations of tile drains in the basin are shown in figure 2. Tile locations were derived from landowner recollection, tile-drain outlets, and infrared aerial photography. Because it was not possible to verify tile locations derived from infrared aerial photography, precedence for estimating locations was given to landowner recollection and tile-drain outlets. The Leary Weber Ditch Basin is topographically flat. A few land areas adjacent to the ditch have overland runoff; areas farther away hold ponded water, unless they too are drained by tile drains. The areas where overland runoff can occur are usually small field-size depressions that drain directly into the ditch, commonly through a culvert that runs beneath the berm of the ditch bank. The Overland Flow site is one of 17 overland flow culverts along the length of Leary Weber Ditch. The Overland Flow site is a 3.5-acre depression with a culvert for drainage at the mouth. The contributing area for runoff is variable and dependent upon the magnitude and intensity of rainfall. Field observations during rainfall indicate that runoff occurs mainly as sheet and rivulet flow to the discharge point. The potential contributing areas of the other 16 culverts were not determined. A sampling plan was established so that chemicals in Leary Weber Ditch Basin could be accounted for from their point of entry into the basin, their storage or degradation within the basin, or until their departure by flow out of the basin through Leary Weber Ditch (Lathrop, 2006). A wide variety of water-quality sampling sites were established throughout the basin to evaluate the occurrence and movement of water and chemicals into Leary Weber Ditch and between the hydrologic compartments: rain, soil water, ground water, tile-drain water, and overland-flow water. Five monitoring sites were established to characterize Leary Weber Ditch and th
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