Date of Award
Doctor of Philosophy
Plant, Soil and Environmental Sciences
Russell J. Lewis
Lloyd F. Seatz, Larry S. Jeffery, James Q. Chambers
The adsorption, desorption, and volatility of dinitramine (N4,N4- diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), fluchloralin (N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-trifluoromethyl aniline), and profluralin (N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl- 10-toluidine) were investigated in soil.
Batch adsorption experiments were conducted on four Tennessee soils that had been subjected to various chemical treatments. In one set of extractions soils were sequentially extracted with solvents of increasing polarity. The solvents, the components removed and the change in adsorption relative to nontreated samples of the soils were as follows; ether-waxes and oils-(+22.0%); ethanol-resins-(+34.3%); water polysaccharides-(+ 0.8%); 2% HCl-hemicellulose-(+38.2%); and 80% H2SO4- cellulose-(+77.2%). In a second set of extractions the following solvents, the components removed and the effect on adsorption relative to the nontreated samples of the soils were as follows; 35% H2O2-organic matter-(-21.3%); sodium [citrate-dithionite-bicarbonate]-free iron oxides-(+44.0%); 35% H2O2 + sodium [citrate-dithionite-bicarbonate]- organic matter & free iron oxides -(+576.5%). Adsorption was directly related to the soils' organic matter content and the length of the aniline sidechain. The proposed bonding mechanism for adsorption of the three dinitroanilines in soil is a combination of van der Waals-London interactions reinforced by hydrophobic bonding.
Desorption of the three herbicides showed that profluralin was held with a greater force than dinitramine or fluchloralin. The desorption from soils was inversely related to the soil's organic matter content. Average percent of the adsorbed herbicides desorbed by the five rinses was 32.4, 31.0, and 15.1% for dinitramine, fluchloralin, and profluralin.
The effects of herbicidal properties, herbicide rates (12.5 and 25 μg/50 g), soil moisture (25, 50, 75, and 100% of field capacity-FC) and temperature (greenhouse-average maximum daytime temperature 38°C, laboratory-average maximum temperature 25°C) on volatilization of herbicides from soil were investigated. The average loss of herbicides 14 days after application for the 12.5 yg rate was 43.1, 23.9, and 17.4% for dinitramine, fluchloralin, and profluralin, respectively. Slightly lower values (37.7, 21.7, and 16.0%) were observed for the 25 μg rate. Increasing the soil moisture content increased volatilization substantially for all three herbicides. For example, profluralin loss increased from 23.5% at 25% of FC to 56.3% at FC. Generally no statistical difference in loss was recorded between the greenhouse and laboratory samples. This was due to the greenhouse samples being in a dry state for longer periods of time than the laboratory samples. Coefficients of determination (R-Square) obtained from a multiple regression technique were used to estimate the variability of herbicide loss caused by the parameters herbicides, moisture, temperature in the volatility study. The terms in the analysis included the linear, interaction, and square of the linear terms of herbicides (H), moisture (M), and temperature (T). A three variable model (H H2 M2) explained 89% of the variation for the 12.5 yg rate while a four variable model (H HT H2 M2) explained 86% of the variation for the 25 μg rate.
Akins, Michael B., "The absorption, desorption, and volatility of three dinitroaniline herbicides in soil. " PhD diss., University of Tennessee, 1977.