In cooperation with the Ohio Department of Agriculture Analysis of the Sensitivity of Soils to the Leaching of Agricultural Pesticides in Ohio Water-Resources Investigations Report 98-4108 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior U.S. Geological Survey Analysis of the Sensitivity of Soils to the Leaching of Agricultural Pesticides in Ohio By Charles W.Schalk Water-Resources Investigations Report 98-4108 In cooperation with the Ohio Department of Agriculture U.S. Department of the Interior Bruce Babitt, Secretary U.S. Geological Survey Thomas J. Casadevall, Acting Director Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. For additional information write to: District Chief U.S. Geological Survey 975 West Third Avenue Columbus, Ohio 43212-3192 Copies of this report can be purchased from: U.S.Geological Survey Branch of Information Sun/ices Box 25286, Building 810 Denver, Colorado 80225-0286 CONTENTS Abstract .........................................................................................................................._^ 1 Introduction ............................................................................................................................_^ 1 Purpose and scope ....................................................................................................................................................... 2 Description of study area ............................................................................................................................................ 3 Acknowledgments ....................................................................................................................................................... 3 Literature review ................................................................................................................................^ 3 Movement of pesticides in soil ................................................................................................................................... 3 Transport processes ........................................................................................................................................... 3 Adsorption processes ......................................................................................................................................... 5 Sensitivity and vulnerability assessments ................................................................................................................... 5 Regulations ................................................................................................................................................................. 6 Methods ..............................................................................................................................................................^ 6 Variables used in the analysis of soil sensitivity ......................................................................................................... 7 Assumptions ............................................................................. 8 Distribution of sensitivity indices ............................................................................................................................... 8 Classification of soil sensitivity .................................................................................................................................. 9 Soil sensitivity to pesticide-leaching potential ..................................................................................................................... 9 Suggestions for additional study ........................................................................................................................................... 10 Summary ...............................................................................................................................................................^ 11 References cited ..........................................................................................................................................................^ 11 PLATES [Plate in pocket] 1. Mapping units with the highest proportion of soils sensitive to pesticide leaching. FIGURES 1. Principal aquifers and physiographic diagram and divisions in Ohio ............................................................................ 4 2. Relation among map units, sequences, and layers in STATSGO ................................................................................... 7 TABLES 1. Cross-correlation matrix of Ohio STATSGO variables used in soil-sensitivity analysis ............................................... 7 2. Sensitivity indices for three variables used in the Ohio STATSGO analysis ................................................................. 8 Contents III CONVERSION FACTORS Multiply By To obtain Length inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter Area acre 4,047 square meter acre 0.4047 hectare Flow rate gallon per minute (gal/min) 0.06309 liter per second Application rate pounds per acre (Ib/acre) 1.121 kilograms per hectare Permeability inches per hour (in/hr) 25.4 millimeters per hour IV Contents Analysis of the Sensitivity of Soils to the Leaching of Agricultural Pesticides in Ohio By Charles W.Schalk Abstract buried valleys in several river basins, and parts of central and south-central Ohio. Medium-high- Pesticides have not been found frequently in the sensitivity soil units were found in other river ground waters of Ohio even though large amounts basins, along Lake Erie in north-central Ohio, and of agricultural pesticides are applied to fields in in many of the upland areas of the Muskingum Ohio every year. State regulators, including repre­ River Basin. Low-sensitivity map units domi­ sentatives from Ohio Environmental Protection nated the northwestern quadrant of Ohio. Agency and Departments of Agriculture, Health, and Natural Resources, are striving to limit the presence of pesticides in ground water at a mini­ Introduction mum. A proposed pesticide management plan for the State aims at protecting Ohio's ground water Agriculture is the largest industry in Ohio. In 1994, by assessing pesticide-leaching potential using about 75,000 Ohio farms encompassed 15.2 million geographic information system (GIS) technology acres of land, drove a $57 billion industry, and pro­ duced $1.7 billion in net cash income (Ohio Depart­ and invoking a monitoring plan that targets aqui­ ment of Agriculture, 1995). Money spent on fers deemed most likely to be vulnerable to pesti­ agricultural chemicals continues to grow to accommo­ cide leaching. date this industry. In 1992, Ohio farmers spent $190 The U.S. Geological Survey, in cooperation million on agricultural chemicals, not including fertil­ with Ohio Department of Agriculture, assessed izers; of all acres on which these chemicals were the sensitivity of mapped soil units in Ohio to pes­ applied, 80 percent were treated with herbicides and ticide leaching. A soils data base (STATSGO) 18 percent were treated with insecticides (U.S. Depart­ compiled by U.S. Department of Agriculture was ment of Commerce, 1994). used iteratively to estimate soil units as being of Pesticides have been found seasonally in Ohio's high to low sensitivity on the basis of soil perme­ surface water for years; less frequent or widespread, ability, clay content, and organic-matter content. however, has been the detection of pesticides in ground Although this analysis did not target aquifers water. More than 5 million Ohioans (about 46 percent) directly, the results can be used as a first estimate rely on ground water for drinking supply (R. J. Veley, U.S. Geological Survey, 1997, written commun.). Of of areas most likely to be subject to pesticide con­ these, about 64 percent are served by public water sys­ tamination from normal agricultural practices. tems, whereas 36 percent are supplied by domestic High-sensitivity soil units were found in wells. Protection of ground-water sources is an impor­ lakefront areas and former lakefront beach ridges, tant issue facing Ohio and its agricultural community. Abstract The proposed State Management Plan (SMP) bined effects of the physical characteristics of the soil for Pesticides for the State of Ohio (State Coordinating and pesticide, the hydrogeologic processes occurring Committee on Ground Water, 1996) addresses con­ in the area of ground-water recharge, and the manage­ cerns of pesticides in ground water from a regulatory ment of the land. Analogous to aquifer sensitivity is and managerial perspective. Few detections of pesti­ soil sensitivity, which is the likelihood of a soil to have cides in ground water can be documented, and most of properties affecting the leaching of surface-applied them were in samples from areas known to be espe­ pesticides to ground water. Again, soil sensitivity is cially vulnerable, such as the karstic limestone sink­ not dependent on agronomic practices or pesticide hole region in Hardin, Wyandot, and Seneca Counties properties. (plate 1) (State Coordinating Committee on Ground In most cases, vulnerable aquifers are overlain Water, 1996). The ground-water data base is lim­ by sensitive soils. In other cases, vulnerable aquifers ited not necessarily to the inclusion of pesticides as may be recharged from areas that are distant from the constituents of interest, but to the detections of pesti­ overlying