Fig. 1.

(A) Land use (USDA National Agricultural Statistics Service, 2009b) and (B) permitted animal feeding operations (Iowa Geological Survey, 2009) in Iowa. Stream sites where water samples were collected for analysis in 2008 are designated with black triangles. The number adjacent to this map symbol denotes the corresponding map number that is cross-referenced in Table 1


Fig. 2.

Time series of photographs taken at South Fork Iowa River at headwaters (05451070) showing the general climatic, hydrologic, and crop growth conditions encountered during the five sampling rounds in 2008. (A) March: pregrowing season, snowmelt conditions. (B) June: early growing season, intense flooding conditions. (C) July/August: mid-growing season, normal flow conditions. (D) September: late-growing season, dry conditions. (E) October: harvest, increased flow conditions. (F) view of headwaters during October. All photos taken by Kate Segreto (U.S. Geological Survey).



Fig. 3.

Streamflow conditions at the South Fork Iowa River northeast of New Providence (05451210) during 2008 (USGS National Water Information System, 2009). The dates of sample collection for this site are denoted with an “X.”


Fig. 4.

Summary of chemical concentrations per collection period. (A) Atrazine (ATZ; limit of detection = 7 ng L−1). (B) Formononetin (FOR; limit of detection = 0.8 ng L−1). (C) Deoxynivalenol (DON; limit of detection = 1.5 ng L−1). Percentages at the bottom of each panel indicate frequency of detection (NA = not analyzed because of improper extraction). Boxplots become truncated on the bottom end for compounds with low detection frequencies or look truncated for compounds with numerous detections at the reporting limit.


Fig. 5.

Concentrations of target compounds detected in the 75 stream samples collected during 2008. Percentages at the bottom of each panel indicate frequency of detection. Bold line represents each compounds limit of detection. ATZ, atrazine (herbicide); BIO, biochanin A (isoflavone); COU, coumestrol (coumestan); DAI, daidzein (isoflavone); DEA, deethylatrazine (atrazine degradate); DON, deoxynivalenol (mycotoxin); equol (isoflavone); FOR, formononetin (isoflavone); GEN, genistein (isoflavone); ZON, zearalenone (mycotoxin). Explanation of a boxplot is provided in Fig. 4