Document n9yq8LYvKM4vZGGK1jejjx5XX

AR226-2283 M ark H R u ssell 05/06/2002 11:20 AM To: Catherine A Barton/AE/DuPont@ DuPont cc: Subject: M odeling so il concentrations Cathy, I tried calling you but you w eren't in. The sim plest w ay to estim ate potential so il concentrations is to divide the estim ated loading (mass/area/time) by the depth of so il sam pling, which you have already done. A m ore refined approach to estim ating soil concentrations Is to use a m odel such as PRZM which provides a daily m ass balance of water and chem ical. For a m obile, persistent (half-life = 10 yr) chem ical that is sem i-continuously deposited on the so il surface, an estim ated m ass balance would be: Annual m ass balance m ass added to soil: m ass volatilized: m ass degraded in top 1 m of soil: m ass rem oved via runoff/erosion: m ass taken up by plants: ug/L) m ass leached below 1 m depth m ass rem aining In top 1 m of soil: 0.7-1.4 ug/kg in top 1 meter) 100 gm/ha/yr 1-2 gm/ha/yr (assum ing low volatility) 1-2 gm/ha/yr 1-2 gm/ha/yr 20-30 gm/ha/yr 40-60 gnf/ha/yr (results in gw cone of 15-20 10-20 gm/ha/yr (results in mean so il cone of More exact num bers can be calculated using PRZM . Hope this is useful M ark CAB000097 E ID 546946