Surface Water‐Ground Water Interaction: Herbicide Transport into Municipal Collector Wells (original) (raw)

Minimizing the risk of herbicide transport into public water supplies; a Nebraska case study

Fact Sheet

Herbicides and their by-products commonly are present in Nebraska's major rivers in small concentrations, but these concentrations increase in the planting season during runoff in spring and early summer. Although water from the Elkhorn and Platte Rivers mixes after their confluence, mixing is incomplete near the city of Lincoln well field, which includes horizontal collector wells located on an island in the Platte River. Figure 1. Location of Lincoln, Ashland, selected rivers, and cultivated land (shown in red) in Nebraska (Conservation and Survey Division, University of Nebraska-Lincoln, written commun., 2000).

Herbicides in Ground Water beneath Nebraska's Management Systems Evaluation Area

Journal of Environment Quality, 2003

physical-chemical characteristics that allow for mobility and moderate persistence. Atrazine, the most wide-Profiles of ground water pesticide concentrations beneath the Nespread pesticide in the nation's ground water, and its braska Management Systems Evaluation Area (MSEA) describe the effect of 20 yr of pesticide usage on ground water in the central Platte transformation products together with cyanazine, sima-Valley of Nebraska. During the 6-yr (1991-1996) study, 14 pesticides zine, and alachlor and metolachlor and their transformaand their transformation products were detected in 7848 ground water tion products are the most commonly detected herbisamples from the unconfined water table aquifer. Triazine and acetcides in row-cropped regions (Barbash et al., 1999) (see amide herbicides applied on the site and their transformation products for chemical names of pesticides detected in had the highest frequencies of detection. Atrazine [6-chloro-N-ethylthis study).

Herbicide Transport in Goodwater Creek ExperimentalWatershed: I. Long-Term Research on Atrazine1

JAWRA Journal of the American Water Resources Association, 2011

Atrazine continues to be the herbicide of greatest concern relative to contamination of surface waters in the United States (U.S.). The objectives of this study were to analyze trends in atrazine concentration and load in Goodwater Creek Experimental Watershed (GCEW) from 1992 to 2006, and to conduct a retrospective assessment of the potential aquatic ecosystem impacts caused by atrazine contamination. Located within the Central Claypan Region of northeastern Missouri, GCEW encompasses 72.5 km 2 of predominantly agricultural land uses, with an average of 21% of the watershed in corn and sorghum. Flow-weighted runoff and weekly base-flow grab samples were collected at the outlet to GCEW and analyzed for atrazine. Cumulative frequency diagrams and linear regression analyses generally showed no significant time trends for atrazine concentration or load. Relative annual loads varied from 0.56 to 14% of the applied atrazine, with a median of 5.9%. A cumulative vulnerability index, which takes into account the interactions between herbicide application, surface runoff events, and atrazine dissipation kinetics, explained 63% of the variation in annual atrazine loads. Based on criteria established by the U.S. Environmental Protection Agency, atrazine reached concentrations considered harmful to aquatic ecosystems in 10 of 15 years. Because of its vulnerability, atrazine registrants will be required to work with farmers in GCEW to implement practices that reduce atrazine transport.

Changes in herbicide concentrations in Midwestern streams in relation to changes in use, 1989–1998

Science of The Total Environment, 2000

Water samples were collected from Midwestern streams in 1994-95 and 1998 as part of a study to help determine if changes in herbicide use resulted in changes in herbicide concentrations since a previous reconnaissance study in . Sites were sampled during the first significant runoff period after the application of preemergent herbicides in 1989-90, 1994-95, and 1998. Samples were analyzed for selected herbicides, two atrazine metabolites, three cyanazine metabolites, and one alachlor metabolite. In the Midwestern United States, alachlor use was much greater in 1989 than in 1995, whereas acetochlor was not used in 1989 but was commonly used in 1995. The use of atrazine, cyanazine, and metolachlor was about the same in 1989 and 1995. The median concentrations of atrazine, alachlor, cyanazine, and metolachlor were substantially higher in 1989-90 than in 1994-95 or 1998. The median acetochlor concentration was higher in 1998 than in 1994 or 1995. Figure 4. Distribution of alachlor concentrations in post-application runoff samples from Midwestern streams, 1989Midwestern streams, -90, 1994Midwestern streams, -95, and 1998

Major Herbicides in Ground Water

Journal of Environment Quality, 2001

are unlikely to "ensure adequate protection of ground water"-but whose use is not cancelled on a national To improve understanding of the factors affecting pesticide occurbasis (USEPA, 1991(USEPA, , 1993a. The first set of proposed rence in ground water, patterns of detection were examined for selected herbicides, based primarily on results from the National Water-PMPs will focus on four herbicides that are used pri-Quality Assessment (NAWQA) program. The NAWQA data were marily for agricultural purposes; atrazine, simazine, derived from 2227 sites (wells and springs) sampled in 20 major hydroalachlor, and metolachlor, hereafter referred to as the logic basins across the USA from 1993 to 1995. Results are presented PMP herbicides. Cyanazine was originally included in for six high-use herbicides-atrazine (2-chloro-4-ethylamino-6-isothe PMP list, but subsequently removed with the cancelpropylamino-s-triazine), cyanazine (2-[4-chloro-6-ethylamino-1,3,5lation of its registration for all uses in December 1999 triazin-2-yl]amino]-2-methylpropionitrile), simazine (2-chloro-4,6-bis-(Jones, 2000). As the PMPs evolve, their analytical [ethylamino]-s-triazine), alachlor (2-chloro-N-[2,6-diethylphenyl]-Nscope may expand to include other pesticides and pesti-[methoxymethyl]acetamide), acetochlor (2-chloro-N-[ethoxymethyl]-

Water Quality in Walnut Creek Watershed: Herbicides in Soils, Subsurface Drainage, and Groundwater

Journal of Environment Quality, 1999

There is a lack of quantitative information describing the impact of farming on water quality at the watershed scale. This study documents the surface water quality of Walnut Creek-a 5130-ha watershed with about 86% of the land used for crop production. Starting in 1990, flow and concentrations of NO 3 -N and four herbicidesatrazine [e-chloro-W-ethyl-JVXl-methylethyty-l^S-triazine^-diamine], alachlor [2-chloro-7V-(2,6-diethylphenyI)-JV-(methoxymethyl)acetamide], metribuzin [4-amino-6-(l,l-dimethylethyl)-3-(methylthio)-l,2,4-triazin-5(4/f )-one], and metolachlor [2-chloro-A'-(2-ethyl-6-methylphenyl) -N -(2 -methoxy -l-methylethyl)acetamide]-were measured at eight locations. Nitrate-N concentrations often exceeded 10 mg L" 1 during May, June, and July. Total losses from the watershed ranged from 4 to 66 kg ha ' yr~' and represented 6 to 115% of the N applied as fertilizer in any year. Atrazine and metolachlor were detected at concentrations >0.2 (ig L" 1 in about half of all water samples, while alachlor and metribuzin were seldom detected. Median concentrations for atrazine and metolachlor were below 1 jig L ' for all locations within the watershed. During runoff events, herbicide concentrations in the stream increased while NO 3 -N concentrations decreased. Yearly losses from the watershed ranged from 0.2 to 7.5 g ha" 1 for atrazine and from 03 to 6.7 g ha ' for metolachlor. These losses represent 0.18 to 5.6% of the atrazine and 0.047 to 1.6% of the metolachlor applied in any year.

Atrazine and Metolachlor in Surface Runoff under Typical Rainfall Conditions in Southern Louisiana

Journal of Agricultural and Food Chemistry, 2003

Atrazine and metolachlor are commonly detected in surface water bodies in southern Louisiana. These herbicides are frequently applied in combination to corn, and atrazine to sugarcane, in this region. A study was conducted on the runoff of atrazine and metolachlor from 0.21 ha plots planted to corn on Commerce silt loam, a Mississippi River alluvial soil. The study, carried out over a three-year period characterized by rainfall close to the 30-year average, provided data on persistence in the surface soil (top 2.5 cm layer) and in the runoff active zone of the soil, as measured by decrease in runoff concentrations with time after application. Regression equations were developed that allow an estimate of the runoff extraction coefficients for each herbicide. Atrazine showed soil half-lives in the range 10.5-17.3 days, and metolachlor exhibited half-lives from 15.8-28.0 days. Concentrations in successive runoff events declined much faster than those in the surface soil layer: Atrazine runoff concentrations decreased over successive runoff events with a half-life from 0.6 to 5.7 days, and metolachlor in runoff was characterized by half-lives of 0.6-6.4 days. That is, half-lives of the two herbicides in the runoff-active zone were one-tenth to one-half as long as the respective half-lives in the surface soil layer. Within years, the half-lives of these herbicides in the runoff active zone varied from two-thirds longer for metolachlor in 1996 to one-fifth longer for atrazine in 1995. The equations relating runoff concentrations of atrazine and metolachlor to soil concentrations contain extraction coefficients of 0.009. Losses in runoff for atrazine were 5.2-10.8% of applied, and for metolachlor they were 3.7-8.0%; atrazine losses in runoff were 20-40% higher than those for metolachlor. These relatively high percent of application losses indicate the importance of practices that reduce runoff of these chemicals from alluvial soils of southern Louisiana.

Herbicide Loading to Shallow Ground Water beneath Nebraska's Management Systems Evaluation Area

Journal of Environment Quality, 2003

Atrazine is the most widely detected pesticide in the nation's ground water and the USEPA has set 3 g L Ϫ1 Better management practices can counter deterioration of ground as the maximum contaminant level (MCL) in drinkwater quality. From 1991 through 1996 the influence of improved irrigation practices on ground water pesticide contamination was assessed ing water. at the Nebraska Management Systems Evaluation Area. Three 13.4-ha Generally, nonpoint-source loading of pesticides in corn (Zea mays L.) fields were studied: a conventional furrow-irrigated shallow ground water beneath agricultural fields is visufield, a surge-irrigated field and a center pivot-irrigated field, and a alized as a complex, nonuniform network of macropores center pivot-irrigated alfalfa (Medicago sativa L.) field. The corn fields conveying contaminants through the vadose zone to the received one identical banded application of Bicep (atrazine [6-chlorowater table where high input concentrations are par- -diamine] ϩ metolachlor tially masked by vertical and radial dilution. The major- ity of loading has been attributed to the transfer, mixing, acetamide]) annually; the alfalfa field was untreated. Ground water application, and disposal or "routine use" of pesticides samples were collected three times annually from 16 depths of 31 multiin agriculture. Hallberg (1989), however, points out that level samplers. Six years of sample data indicated that a greater than 50% reduction in irrigation water on the corn management fields low-