@article{weber_warren_swain_yelverton_2007, title={Physicochemical property effects of three herbicides and three soils on herbicide mobility in field lysimeters}, volume={26}, ISSN={["1873-6904"]}, DOI={10.1016/j.cropro.2006.01.020}, abstractNote={Understanding herbicide mobility in soils is necessary to prevent ground water contamination. We studied the mass balance distribution of three 14C-labeled herbicides (atrazine, metolachlor, and primisulfuron-methyl) in three soils (Blanton, Norfolk, and Rains) 128 days after treatment (DAT) to fallow soil column field lysimeters. Analyses were made of surface soil, subsoil, and leachate samples. Volatilization losses were calculated by difference. Our objectives were to examine, measure, and correlate the leaching patterns of the chemicals and correlate their leaching characteristics with physicochemical and biological properties of the herbicides and the physicochemical properties of the soils. Metolachlor was the most mobile herbicide, as indicated by the retardation factor (Rf) (Rf=0.48 in 1992 and 0.19 in 1993), followed by primisulfuron-methyl (Rf=0.41 in 1992 and 0.12 in 1993), and atrazine (Rf=0.38 in 1992 and 0.15 in 1993), where mobility was greatly affected by water input (637 mm in 1992 and 509 mm in 1993). Herbicide mobility (Rf) was related to 14C-parent compound in leachate (0.02–6.9% of 14C applied), 14C in the subsoil (9–24%), and the pesticide leaching potential (PLP) index of each herbicide, as computed using a simple decision-aid model. The herbicides were most mobile through Blanton, followed by Norfolk and Rains soils and mobility (Rf) was inversely related to mean % organic matter (OM) content of the soil profiles and directly related to soil pH and soil leaching potential (SLP) indices of the soils. Physicochemical and biological properties of the herbicides and soils were related to many of the measured herbicide distribution parameters.}, number={3}, journal={CROP PROTECTION}, author={Weber, Jerome B. and Warren, Ralph L. and Swain, Len R. and Yelverton, Fred H.}, year={2007}, month={Mar}, pages={299–311} }
 @article{weber_mckinnon_swain_2003, title={Sorption and mobility of C-14-labeled imazaquin and metolachlor in four soils as influenced by soil properties}, volume={51}, ISSN={["0021-8561"]}, DOI={10.1021/jf021210t}, abstractNote={Aqueous batch-type sorption-desorption studies and soil column leaching studies were conducted to determine the influence of soil properties, soil and suspension pH, and ionic concentration on the retention, release, and mobility of [14C]imazaquin in Cape Fear sandy clay loam, Norfolk loamy sand, Rion sandy loam, and Webster clay loam. Sorption of [14C]metolachlor was also included as a reference standard. L-type sorption isotherms, which were well described by the Freundlich equation, were observed for both compounds on all soils. Metolachlor was sorbed to soils in amounts 2-8 times that of imazaquin, and retention of both herbicides was related to soil organic matter (OM) and humic matter (HM) contents and to herbicide concentration. Metolachlor retention was also related to soil clay content. Imazaquin sorption to one soil (Cape Fear) increased as concentration increased and as suspension pH decreased, with maximum sorption occurring in the vicinity of pK(a1) = (1.8). At pH levels below pK(a1) imazaquin sorption decreased as hydronium ions (H3O+) increased and competed for sites. NaCl was more effective than water in desorption of imazaquin at pH levels near the pK(a1). Mechanisms of bonding are postulated and discussed. The mobility of imazaquin through soil columns was in the order Rion > or = Norfolk > Cape Fear > or = Webster, whereas for metolachlor it was Rion > or = Norfolk >> Webster > or = Cape Fear. Imazaquin was from 2 to 10 times as mobile as metolachlor.}, number={19}, journal={JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY}, author={Weber, JB and McKinnon, EJ and Swain, LR}, year={2003}, month={Sep}, pages={5752–5759} }
 @inbook{van wesenbeeck_schabacker_winton_heim_winberry_williams_weber_swain_velagaleti_1998, title={Demonstration of the functionality of a self-contained modular lysimeter design for studying the fate and transport of chemicals in soil under field conditions}, DOI={10.1021/bk-1998-0699.ch009}, abstractNote={Analytical Bio-Chemistry (ABC) Laboratories, Inc. has developed a modular lysimeter design and has instrumented and installed the lysimeters at four field sites in the United States: Missouri (MO), Iowa (IA), Illinois (IL), North Carolina (NC) and Ontario (ON), Canada. The modular lysimeter design consists of three components that are readily assembled and installed in the field; an intact soil core, a run-off (overflow) collection system, and a leachate collection system. In NC, the lysimeters were installed at the NC State University Experimental Station site in Clayton with a Novartis Crop Protection development compound, designated as 14C-XYZ for confidentiality reasons. The fate and transport of the chemical was studied over a period of 90 days using intact 90 cm deep, 15 cm diameter soil columns containing sandy soil. Parent compound degraded into an acid metabolite that was detected down to 60 cm in the soil profile. Parent compound was not observed at a soil depth below 15 cm. The decline of the parent compound coincided with the formation of the acid metabolite which degraded into four additional metabolites. Lysimeters 30 cm in diameter and 75-90 cm deep were instrumented and installed at four locations (MO, IA, IL, and ON) to study the fate and transport of a DowElanco development compound, designated as 14C-DEC for confidentiality reasons. In these experiments, the fate and transport of the test compound and a bromide tracer in the lysimeters were compared with that in the field plots for 12 months. Preliminary results from IA and MO suggest that degradation and solute transport processes were similar in the soil plots and lysimeters, and that the 30 cm diameter pipe lysimeters approach the representative elementary volume (REV) for solute transport processes at the IA site. The modular pipe lysimeter design offers significant advantages in terms of assessing solute mass balance, mobility, variability (through increased replication) and reduced cost of radioactive waste compared to soil plot studies.}, number={699}, booktitle={The lysimeter concept: Environmental behavior of pesticides}, publisher={Washington, DC: American Chemical Society}, author={Van Wesenbeeck, I. and Schabacker, D. J. and Winton, K. and Heim, L. and Winberry, M. W. and Williams, M. D. and Weber, J. B. and Swain, L. R. and Velagaleti, R.}, year={1998}, pages={122–135} }