Sorption of atrazine and dicamba in Delaware coastal plain soils: a comparison of soil thin layer and batch equilibrium results
✍ Scribed by Johnson, Richard M.; Thomas Sims, J.
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 209 KB
- Volume
- 54
- Category
- Article
- ISSN
- 1526-498X
No coin nor oath required. For personal study only.
✦ Synopsis
The mobility and retention of atrazine and dicamba in six Atlantic Coastal Plain soils were estimated by soil thin-layer chromatography (soil-TLC). The soils studied were representative of the major agricultural regions in Delaware and were sampled, by horizon, to the water table. Four horizons from each proÐle were leached simultaneously with distilled water on one soil-TLC plate. Two values were obtained from each plate : the ratio of the distance traveled by the herbicide center of mass over that traveled by the solvent front and a
R m atrazine and from 0É80 to 0É94 for dicamba. Herbicide mobility was found to be greatest in coarse-textured soil horizons that contained low levels of organic matter, clay, and Fe and Al oxides. Correlation analysis indicated that e †ective cation exchange capacity, exchangeable acidity, exchangeable aluminum, and clay were useful predictive variables or both atrazine mobility and sorption. Organic matter was not useful for predicting soil-TLC derived sorption estimates ; however, it was correlated to estimates. Distribution coefficients K d -batch calculated from soil-TLC data were found to be in general agreement with K d values obtained for the same soils by batch equilibrium techniques. The average values for atrazine and dicamba were 2É09(^2É24) and 0É03(^0É02), K d -soil-TLC respectively. The ratio of the batch to the soil-TLC ranged from 0É1 to 19 K d K d (x6 \ 1É6, SD \ 3É8) for atrazine and from 2É9 to 38 (x 6 \ 12É6, SD \ 8É7) for dicamba. Thus, although for some horizons agreement between the two methods was good, for other horizons signiÐcant discrepancies existed. It is suggested that the soil-TLC gives results under non-equilibrium conditions, whereas the batch procedure is, by deÐnition, at quasi-equilibrium. These fundamental di †erences may account for the observed di †erences between the two methods. It is also suggested that, due to this di †erence, the soil-TLC procedure can provide additional information relevant to herbicide partitioning in the Ðeld environment that is not provided by traditional batch equilibrium techniques.