Sorption Interactions between Imazaquin and a Humic Acid Extracted from a Typical Brazilian Oxisol

Abstract

Soil sorption of most hydrophobic organic compounds (e.g., nonpolar pesticides) is directly related to soil organic matter (SOM) content. Humic substances are the major SOM components, containing carboxylic, phenolic, amine, quinone, and other functional groups, and specific structural configurations. In this paper, sorption interactions between imazaquin (2-[4,5-dydro-4-methyl-4-(1-methylethyl)-5-oxo-1H- imidazol-2-yl]-3-quinoline-carboxylic acid) herbicide (IM) and a humic acid (HA) extracted from a typical Brazilian Oxisol were studied with electron paramagnetic resonance (EPR) and Fourier-transform infrared (FTIR) spectroscopic techniques. A polarographic technique was used to quantify sorption. The IM amount sorbed on the HA was much higher than that on the whole soil within the pH range studied, emphasizing the prominent role played by SOM on IM sorption. Moreover, IM sorption increased as the soil-solution pH decreased. This enhancement in sorption was attributed to the hydrophobic affinity of the herbicide by the HA and to the electrostatic interaction between the protonated quinoline group of IM and the negative sites of the HA. Hydrophobic regions in the HA's interior at low pH (< 5.0) were recently demonstrated by an EPR detectable spin-label molecule. The FTIR and EPR spectroscopy and polarography data indicated weak interaction between IM and the soil and its HA, involving hydrogen bonding, proton transfer, and cation exchange (at low pH), and mainly hydrophobic interactions. However, no strong reaction mechanism, such as charge transfer, was involved. In addition, this research suggested that soil amendment with organic material might increase magnitude of IM sorption, consequently avoiding leaching and carryover problems usually found for mobile and persistent herbicides such as imazaquin.

Sorptive removal of ibuprofen from water using selected soil minerals and activated carbon

“…4b-d) presumably due to instantaneous complexation of ibuprofen with HA in aqueous phase as HA was introduced (Ferreir et al 2002;Gu et al 2007). In the 10-50 mg/L HA concentration range, an increased ibuprofen sorption (2.27-5.1, 1.4-3.35 and 1.5-4.7 mg/g, respectively in kaolinite, montmorillonite and goethite) was observed, while a higher concentration of HA (100 mg/L) resulted in an opposite effect.…”

Sorção e hidrólise do herbicida flazasulfuron

“…Por outro lado, aumentos de pH implicam aumentos na quantidade de moléculas aniônicas em solução (pH ≥ pK a ), propiciando ligações catiônicas com os colóides do solo. Contribuição significativa dos óxidos de ferro e alumínio na sorção de herbicidas ácidos fracos tem sido observada em solos com baixos teores de carbono orgânico, conforme observado por Regitano et al (1997Regitano et al ( , 2001Regitano et al ( , 2002, Ferreira et al (2002), Rocha et al (2002) e Koskinen & Harper (1990) . Oliveira Jr. et al (2000) descreveram relação inversa entre sorção e pK a para sulfometuron-metil, nicosulfuron e metsulfuron-metil em solos brasileiros, indicando relação entre a especiação das moléculas e o pH.…”

Sorption of Pesticides on Natural Geosorbents

“…Humic substances are the most important class of molecules present in the natural organic matter (Thurman, 1985, Senesi, 1992, Tremblay & Gagné, 2009. Hydrophobic interactions are proposed as an important mechanism for the sorption of many pesticides such as DDT, endrin and other organochlorine pesticides (Lenheer & Aldrichs, 1971, Peng et al, 2009, atrazine and simazine (Herwig et al, 2001), 2,4-dichlorophenoxyacetic acid and triclopyr (Johnson et al, 1995), imazaquin (Ferreira et al, 2002), carbaryl (de Oliviera et al, 2005, pentachlorophenol (Lee et al, 1990), primisulfuron (Ukrainczyk & Ajwa, 1996), prometryn (Khan, 1982), s-triazine herbicides (Celis et al, 1997) and imidacloprid (Liu et al, 2006). The presence of numerous polar oxygen and hydroxyl-containing groups in pesticides, humic substances or clays gives rise to the formation of hydrogen bonds between electron- (Cox et al, 1993, Yang et al, 2005, primisulfuron , glyphosate (Vereecken, 2005), 2,4-dichlorophenoxyacetic acid (Hyun & Lee, 2005), and atrazine (Martin-Neto et al, 1994, Kovaios et al, 2006, Lima et al, 2010.…”