Document N0e7egN1yG2w6yMB8jMpw1JR

AR226-2283 [.....l.....^M.K..--*. Mark H Russell 05/06/20021150 AM To: cc: Subject: Catherine A Barton/AE/DuPont DuPont Modeling soil concentrations Cathy, I tried calling you but you weren't in. The simplest way to estimate potential soil concentrations is to divide the estimated loading (mass/area/time) by the depth of soil sampling, which you have already done. A more refined approach to estimating soil concentrations is to use a model such as PR2M which provides a daily mass balance of water and chemical. For a mobile, persistent (half-life = 10 yr) chemical that is semi-continuously deposited on the soil surface, an estimated mass balance would be: Annual mass balance mass added to soil: mass volatilized: mass degraded in top 1 m of soil: ug/L) mass removed via runoff/erosion: mass taken up by plants: mass leached below 1 m depth mass remaining In top 1 m of soil: 0.7-1.4 ug/kg in top 1 meter) More exact numbers can be calculated using PR2M. Hope this is useful 100 gm/ha/yr 1-2 gm/ha/yr (assuming low volatility) 1-2 gm/ha/yr 1-2 gm/ha/yr 20-30 gm/ha/yr 40-60 grn/ha/yr (results in gw cone of 15-20 10-20 gm/ha/yr (results in mean soil cone of Mark CAB000097 EID546946