clay and imazethapyr

Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t

Topics: Acrylic Resins; Aluminum Silicates; Bentonite; Clay; Diffusion; Galactans; Herbicides; Hydrogels; India; Kinetics; Mannans; Nanocomposites; Nicotinic Acids; Particle Size; Plant Gums

We investigated sorption characteristics of two commonly used herbicides, atrazine and imazethapyr, in 101 soils with allophanic and non-allophanic clays of New Zealand using the batch equilibration technique. Soil properties, such as organic carbon (OC) content, texture, pH, amount and type of clay, and cation-exchange capacity (CEC), were tested against the sorption coefficients (Kd) of these herbicides. There was a wide variation in the sorption affinities of the soils, as the Kd values of atrazine and imazethapyr ranged from 0.7 to 52.1 and from 0.1 to 11.3 L kg(-1), respectively. For atrazine, the sorption affinities for the allophanic set of soils (mean Kd of 8.5 L kg(-1)) were greater than for the non-allophanic set of soils (mean Kd of 7.5 L kg(-1)). However, no effect of allophanic status was found for imazethapyr sorption (mean Kd of 0.82 and 0.76 L kg(-1) for allophanic and non-allophanic, respectively). None of the measured soil properties could alone explain adequately the sorption behavior of the herbicides. The variation of OC soil sorption coefficients, Koc, was also larger for atrazine (mean Koc of 126.9 L kg(-1)) than for imazethapyr (mean Koc of 13.2 L kg(-1)). The prediction equations for atrazine and imazethapyr developed overseas failed to provide the acceptable values of sorption coefficients for the soils of New Zealand. The study highlights the danger of using sorption coefficient data from the literature for practical assessments of the herbicide leaching in New Zealand soils.

Topics: Adsorption; Aluminum Silicates; Atrazine; Clay; Herbicides; New Zealand; Nicotinic Acids; Soil

Sorption of ametryn and imazethapyr in 25 soils from Pakistan and Australia was investigated using the batch method. The soils varied widely in their intrinsic capacities to sorb these herbicides as shown by the sorption coefficients, Kd, which ranged from 0.59 to 47.6 for ametryn and 0.02 to 6.94 for imazethapyr. Generally the alkaline soils of Pakistan had much lower Kd values of both herbicides than the soils of Australia. Both soil pH and soil organic carbon (SOC) were correlated significantly with the sorption of ametryn, whereas only soil pH was strongly correlated with imazethapyr sorption. No correlation was found between Kd values of the herbicides and the clay contents of the soils. Multiple regression analysis showed that Kd values were better correlated (r2=0.94 and 0.89 for ametryn and imazethapyr, respectively) if SOC and pH were simultaneously taken into account. The study indicated that sorption of these herbicides in the alkaline soils of Pakistan was low and consequently there is considerable risk of groundwater contamination.

Topics: Adsorption; Aluminum Silicates; Australia; Carbon; Clay; Herbicides; Hydrogen-Ion Concentration; Kinetics; Linear Models; Nicotinic Acids; Pakistan; Soil; Soil Pollutants; Triazines