Release of Fenamiphos, Atrazine, and Alachlor into Flowing Water from Granules and Spray Deposits of Conventional and Controlled-Release Formulations

Abstract

The release into water of active ingredients from spray deposits or granules of fenamiphos, atrazine, and alachlor was measured for commercial and experimental controlled-release formulations. Granules or spray mixtures of the pesticides were mixed with coarse sand and dried if necessary, and the mixture was placed in 5 mm × 35 mm stainless steel cylinders through which distilled water was then pumped for 24 h. Pesticide concentrations in the eluate were determined by HPLC analysis. The conventional formulations (emulsifiable concentrates, granulars, and dispersible granules) gave total release in 5−24 h and in some cases appeared to release particles into contacting water. Controlled-release starch-encapsulated formulations gave between 5% and 94% release in 24 h. Clay/alginate and clay/alginate/linseed oil formulations gave 0.3−100% release in 24 h, depending mainly on the aqueous solubility and lipophilicity of the pesticide. This simple technique provides comparative insights into the amounts and rates of release of pesticide active ingredients (and/or other chemicals such as oxidative degradates) when these formulations are contacted by flowing water. Initial results indicate that formulation can affect the potential of these pesticides to be water pollutants under severe rainfall conditions. Keywords: Atrazine; alachlor; fenamiphos; formulation; controlled release; spray deposit; water quality; runoff; leaching; granules

Effect of formulations and treatment methods of nursery boxes applied with insecticide on the behavior of imidacloprid in rice paddy fields

“…3,10,17,25,26) Again, the covered soil particles play a role, as does the controlled release layer discussed previously. 24,27) This layer partly reduced the imidacloprid release rate in both treatments. Consequently, the slow release rate of imidacloprid from soil to paddy water in addition to the photolysis of imidacloprid in paddy water resulted in increased partitioning towards the later period.…”

“…[17][18][19] The release rate of active ingredient from granules depended on the characteristics of sorbents, 8,18) sizes of the granules, 16,17,19) loading mass of the pesticide, and physicochemical properties, such as the aqueous solubility and lipophilicity of pesticides. 8,16,18,19,24) The mechanism of dissolution and sorption of imidacloprid for BT and AS treatments in rice paddy fields is elucidated in the Fig. 4.…”

“…3,10,17,25,26) Moreover, previous studies reported that soil particles may behave like a controlled release formulation because of their adsorption-desorption characteristics. 24,27) In addition to the controlled release formulation, this soil layer promoted a slower release rate in AS treatment; consequently, the low concentration of imidacloprid was found in AS treatment. Since imidacloprid in water is very sensitive to sunlight, 2,21) the controlled release formulation with AS treat- Vol.…”

Runoff and leaching of atrazine and alachlor on a sandy soil as affected by application in sprinkler irrigation

“…The highest concentrations of atrazine were nearly twice its solubility of 33 ppm (Hornsby, et al, 1996) indicating that our splash samples contained paniculate atrazine which later dissolved in the extracting solvent. This is further evidence (Wauchope et al, 1990;Davis et al, 1996) that the fine particulates deposited by commercial atrazine formulations may be washed off fields in worst-case runoff situations. Alachlor, applied as an emulsion, generally gave lower concentrations though the differences with atrazdnewere not always large.…”

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“…Slow Release or Controlled Release (CR) granules release chemicals more slowly than conventional granules and under worst-case conditions of rainfall immediately after application they should exhibit lower runoff. (Davis et al, 1996). So, under those conditions conventional granules would give more runoff than CR granules.…”