Characterization and prediction of nutrients and pesticides in base flow conditions of first order streams in the Mid-Atlantic Coastal Plain - a collaborative effort Ann M. Pitchford, Anne C. Neale, USEPA/ORD/NERL/ESD/LEB Judith M. Denver, Scott W. Ator, IJSGS MD-DE-DC Water Science Center - 4fi& ' , VIRGS^ | — " "' ¦ •" \ V" - : . ^ jcWW-*" 1. Goals Study Area in Mid- Atlantic Coastal Plain The Landscape Indicators for Pesticides Study in Mid-Atlantic Coastal Streams (LIPS-MACS) goals: •Characterize levels of pesticides and nutrients in headwater stream base flow and associated stream biota. •Predict water quality in small streams throughout the Coastal Plain using geographic information such as land use, geology, soil types, and land forms. 2. Methods a. Sampling From a total of 10,144 first-order streams, 174 streams were selected across a gradient of hydrogeologic and land-use settings. Water samples were collected from all 174 streams and analyzed for selected pesticides, pesticide metabolites, nutrients, and major ions. Benthic- community and habitat assessments were also conducted at each stream. b. Landscape Metrics Predominant texture of surface sediments Clay and Silt HJ Mixed Mixed with Peat Sand and Gravel Landscape metrics were computed using data for soils, land use, and topography for each stream's watershed. Land Cover- % agriculture (ag) total, forest, urban, wetland, barren, ag on slopes >3% Human Stresses- Road density, roads crossing streams, roads in close proximity to streams Riparian Buffer Land Cover- % ag, forest, urban, or wetland in stream grid cell Topography- Elevation mean, range, slope mean, slope curvature Soil-related Metrics- % clay, % organic matter, % sand, available water capacity, mean bulk density, moisture content, permeability, water table depth Principal components grouped these metrics: Principal Components PCI- upland (vs. low-relief) areas PC2- urban and road influences PC3- soil texture, well-drained soil PC 4- agriculture PC5- wetland influences PC6- barren land influences PC7- mixed: low-organic-matter wetlands and roads crossing streams PC8- soil organic matter and non-barren land c. Making the Maps Notice: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy. Mention of trade names or commercial products does not constitute endorsement or recommendation by EPA for use. Stepwise logistic regression for binary data was used to predict the likelihood of selected nutrients or pesticide compounds occurring in streams in late winter or spring base flow at or ab ov e certain c one entrations. Variable s considered included principal components above and geologic setting, as well as sample date and stream latitude. 3. Characterization Results a. Nutrients Nutrient concentrations vary regionally with differences in land use, soils, hydrogeology, and other factors that control the occurrence and fate of these compounds. Nitrogen •Nitrate is the predominant form of nitrogen in streams in we 11- draine d watersheds. The m edian nitrate concentration among Coastal Plain streams during base flow is 0.4 mg/L. •Ammonia and organic nitrogen are the predominant nitrogen species in streams in poorly drained watersheds. Phosphorus •Phosphorus concentrations are generally lower in streams in watersheds with well-drained sediments; •Phosphorus concentrations are higher in poorly drained watersheds. Hydrogeologic Subregions ¦f C oastal L owlands [ 2 Mixed Sediment | 3 Fine Sediments Inner Coastal Plain 4. Maps of Predictions Concentrations of selected nutrients in streams in different hydrogeologic subregions during base flow. Relation of pesticide occurrence in streams during base flow and watershed land use. I 6 Dissected Outcrop i ri i W ii- » I • i l£~ i; b. Pesticides •Low concentrations of pesticides or pesticide degradates were detected in about three-quarters of the streams in the Coastal Plain during winter and spring base flow. •Very few of the detections were above levels considered harmful to aquatic life, although these levels have not been determined for many of the compounds detected. •Although concentrations were typically low, multiple pesticide compounds were commonly present. •Metolachlor and its two common degradates, metolachlor ESA and metolachlor OA, were the most frequently detected pesticide compounds in the Coastal Plain; concentrations of metolachlor degradates were generally much higher than those of metolachlor. a. Nutrients Probability of nitrate at concentrations Nitrate greater than or equal to 0.71 mg'L. ,/ Vj — U4| J rSKflu Si::: ag Although nitrate is common in Coastal Plain streams during base flow, concentrations greater than 0.71 mg/L are relatively unlikely. Areas with the highest likelihood of nitrate greater than 0.71 mg/L occur in highly agricultural or urban areas with we 11-drained soils. b. Pesticides Metolachlor iU and Breakdown i- ill Products -t " .. i Probability or metolachlor f«ncluelin< metabolites) at n, 7 greater than or equal lo 0 06 ug>L ' **" ¦Safe ¦filL 'M -M Metolachlor compounds (including metolachlor, metolachlor ESA, and metolachlor OA) occur in stream base flow in most areas of the Coastal Plain. Concentrations of total metolachlor above 0.06 jxg/L are most likely to occur in agricultural areas of southern New Jersey, the Delmarva Peninsula, southern Virginia, and North Carolina; they are least likely in forested areas. 5. Potential Applications ¦Assessing pesticide and nutrient occurrence and vulnerability within a wide area; •Allocating resources for additional, focused monitoring; •Protecting source waters; •Assessing statewide waters compared to designated uses; •Evaluating best management practice options. 6. Collaborators •U.S. Environmental Protection Agency •U.S. Geological Survey's National Water Quality Assessment Program; and •Multi-Resolution Landscape Characteristics Consortium. Acknowledgement: The authors thank the U.S. EPA's Ecological Exposure Research Division for collecting and analyzing the benthic macroinvertebrate and sediment samples. 1261eb 05. SF -Pitchford * a y epascienceforum \^/y I Collaborative Science for Environmental Solutions rv PRO"*4- TW) ' c INO o 0 01 ------- |