Wednesday, November 15, 2006

Simazine Removal comparing Peat Moss and Gravel in Mesocosms.

Gordon Stearman1, Plaxedes Makweche2, and Dennis George2. (1) Tennessee Tech. Univ., Tennessee Tech University, Box 5033 Water Center, Cookeville, TN 38505, (2) Tennessee Technological Univ, Box 5033, Cookeville, TN 38505

Removal of the herbicide simazine using peat moss and gravel in sterilized and nonsterilized mesocosms was tested at one and four day retention times in an environmental growth chamber. Glass mesocosms 15.2 cm in length and 15.2 cm inside diameter were used. Pore space was 400 mL for both gravel and peat moss. A 0.6 ppm simazine stock solution was gravity fed to gravel and peat moss mesocosms for 16 days for one day retention time and 16 days for four day retention times. The leachate samples collected daily were analyzed for simazine using gas chromatography. Treatments were analyzed using analysis of variance and mean separation tests. Significant difference was observed between peat and gravel and between one and four day retention times. Peat moss removed 100% simazine for all treatments while gravel removed 42% simazine. Gravel showed signifcant difference under sterilized and nonsterilized conditions (39% vs. 45%, respectively) as well as under one and four day retention times (81% vs. 3%, respectively). Gravel unlike peat moss, apparently became overloaded with simazine during the 40-day duration of the mesocosm column study and was unable to remove significant simazine during the four day retention time. A batch adsorption study showed that peat moss removed over 90% of simazine with an adsorption coefficient of 0.41 L/g for 1 g peat and 0.31 L/g for 2 g peat using 150 mL of simazine solution. Simazine removal at the field wetland cells using peat moss is currently being examined.