Premium
Estimating sorption of monovalent acidic herbicides at different pH levels using a single sorption coefficient
Author(s) -
Spadotto Claudio A,
Locke Martin A,
Bingner Ronald L,
Mingoti Rafael
Publication year - 2020
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.5815
Subject(s) - sorption , chemistry , partition coefficient , dissociation constant , soil water , chromatography , analytical chemistry (journal) , environmental chemistry , organic chemistry , adsorption , environmental science , soil science , biochemistry , receptor
BACKGROUND Monovalent acidic pesticide sorption can be determined for any soil pH if the dissociation constant of the compound is known, and sorption coefficients are available for at least two different pH values, measured in a wide enough range to enable estimating both neutral and anionic form coefficients. Sorption estimates have also been made from a single sorption coefficient available, assuming a non‐compound specific value of the anionic form sorption coefficient or considering a generic ratio between sorption coefficients of the two forms. A compound‐specific procedure for adjustment of parameters of the equation for estimating sorption of monovalent acidic herbicides at different pH levels, from a single sorption coefficient, is proposed and evaluated. RESULTS The quality of fits was good for sorption of all three herbicides studied, especially for 2,4‐D and flumetsulam at pH above 5, even for diverse soils and experimental procedures and conditions. The best fits resulted in the following ratios of theoretical maximum organic‐carbon sorption coefficients for neutral and anionic forms (Kocn’:Koca’): 440:1 for 2,4‐D; 132:1 for flumetsulam; and 55:1 for sulfentrazone. CONCLUSION The ratios of theoretical maximum sorption coefficients for neutral and anionic forms (Kocn’:Koca’) are compound‐specific, thus this procedure should also be applied to pH‐sorption datasets for other acidic pesticides to provide the respective ratio between the theoretical maximum sorption coefficients, instead of using generic assigned values. More calibration research is recommended and validation of this approach is required to demonstrate applicability of the method. © 2020 Society of Chemical Industry