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Urea Fertilizer and pH Influence on Sorption Process of Flumetsulam and MCPA Acidic Herbicides in a Volcanic Soil
Author(s) -
Palma Graciela,
Jorquera Milko,
Demanet Rolando,
Elgueta Sebastian,
Briceño Gabriela,
Luz Mora María
Publication year - 2016
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2015.07.0358
Subject(s) - mcpa , chemistry , sorption , urea , fertilizer , adsorption , andisol , nuclear chemistry , environmental chemistry , soil water , agronomy , soil science , organic chemistry , pesticide , biology , environmental science
The aim of this study was to evaluate the influence of urea fertilizer and pH on the sorption process of two acidic herbicides, flumetsulam (2′,6′‐difluoro‐5‐methyl[1,2,4]triazolo[1,5‐a]pyrimidine‐2‐sulfonanilide) and MCPA (4‐chloro‐ o ‐tolyloxyacetic acid), on an Andisol. Urea reduced the adsorption of MCPA but not that of flumetsulam. The Freundlich parameter K f of MCPA decreased from 8.5 to 5.1 mg 1−1/ n L 1/ n kg −1 . This finding could be attributed to an increase in dissolved organic C due to an initial increase in soil pH for urea application. The higher acidic character of MCPA compared with that of flumetsulam produced a greater hydrolysis of urea, leading to a further pH increase. A marked effect of pH on the adsorption of both herbicides was observed. The organic C distribution coefficient ( K oc ) values for flumetsulam were in the range of 74 to 10 L kg −1 , while those of MCPA were in the range of 208 to 45 L kg −1 . In the kinetic studies, the pseudo‐second‐order model appeared to fit the data best ( R 2 > 0.994). The initial adsorption rates ( h ) ranged from 20.00 to 4.59 mg kg −1 h −1 for flumetsulam and from 125.00 to 25.60 mg kg −1 h −1 for MCPA. Both herbicides were adsorbed rapidly during the first stage of the sorption process, and the rates of sorption were dependent on pH. The application of the Elovich and Weber–Morris models led us to conclude that mass transfer through the boundary layer and, to a lesser degree, intraparticle diffusion were influenced by the chemical character of the herbicide. These results suggest that urea application could increase leaching of acid herbicides in soils. Core Ideas The effect of urea on adsorption depended on the acidic character of the herbicides. An increase in pH and dissolved organic C due to urea application was observed. The sorbed amount of MCPA was higher than that of flumetsulam. Urea application could increase the leaching of acid herbicides in Andisols.