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This article in JEQ

  1. Vol. 39 No. 3, p. 1019-1027
    Received: July 30, 2009

    * Corresponding author(s): msoupir@iastate.edu
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Attachment of Escherichia coli and Enterococci to Particles in Runoff

  1. Michelle L. Soupir *a,
  2. Saied Mostaghimib and
  3. Theo Dillahac
  1. a Agricultural &Biosystems Engineering, Iowa State Univ., 3163 NSRIC Building, Ames, IA 50011
    b Biological Systems Engineering, Virginia Tech, 200 Seitz Hall, Blacksburg, VA 24061
    c Biological Systems Engineering, Virginia Tech, 840 Univ. City Blvd., Blacksburg, VA 24061. Assigned to Associate Editor A. Mark Ibekwe


Association of Escherichia coli and enterococci with particulates present in runoff from erodible soils has important implications for modeling the fate and transport of bacteria from agricultural sources and in the selection of management practices to reduce bacterial movement to surface waters. Three soils with different textures were collected from the Ap horizon (silty loam, silty clay loam, and loamy fine sand), placed in portable box plots, treated with standard cowpats, and placed under a rainfall simulator. Rainfall was applied to the plots until saturation-excess flow occurred for 30 min, and samples were collected 10, 20, and 30 min after initiation of the runoff event. The attachment of E. coli and enterococci to particles present in runoff was determined by a screen filtration and centrifugation procedure. Percentage of E. coli and enterococci attached to particulates in runoff ranged from 28 to 49%, with few statistically significant differences in attachment among the three soils. Similar partitioning release patterns were observed between E. coli and enterococci from the silty loam (r = 0.57) and silty clay loam soils (r = 0.60). At least 60% of all attached E. coli and enterococci were associated particles within an 8- to 62-μm particle size category. The results indicate that the majority of fecal bacteria attach to and are transported with manure colloids in sediment-laden flow regardless of the soil texture.

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