Photolysis of Atrazine and Ametryne Herbicides in Barbados Sugar Cane Plantation Soils and Water

Abstract

The photodegradation kinetics of atrazine (2-chloro-6-(ethylamino)-4-isopropylamino-1,3,5-triazine) and ametryne (2-methylthio-4-ethylamino-6-isopropylamino-s-triazine), in fresh and coastal salt water from Barbados, were measured under irradiation with artificial solar and UV254-radiation. The first-order rate constants were greater for ametryne than for atrazine, and the rates were reduced in seawater relative to fresh water, and in soil slurries relative to fresh water. However, rates were accelerated in the presence of iron(III) at pH 3 due to photo-Fenton type processes. This rate enhancement was reduced at ambient pH values (pH 7-7.5) representative of surface water in Barbados. These results have important implications for the relative persistence of these contaminants in aquatic environments in tropical areas.

Ametryn degradation in the ultraviolet (UV) irradiation/hydrogen peroxide (H2O2) treatment

“…Yang et al [6] found that a commercial activated carbon had an adsorption capacity of 230 mg ametryn adsorbed/g activated carbon at pH 6.07 when aqueous equilibrium concentration of ametryn was around 36 mg/L. McMartin et al [7] investigated ametryn decomposition by several advanced oxidation processes (AOPs). Ametryn degradation was a pseudo-first-order reaction under photoradiation.…”

The role of indirect photochemical degradation in the environmental fate of pesticides: a review

“…Faster photolysis was reported in spring water (pH 7.5, 2.3 mg C per L) compared to ocean water, but a direct photolysis control was not included and the organic carbon content of the ocean water was not specied. 333 Studies using model sensitizers provide information about the reactivity of the herbicide with reactive species. Triplet sensitizers accelerate the photodegradation of ametryne, 36,334,335 while the herbicide is relatively unreactive towards singlet oxygen 335,337 and CO 3 À c. 30 Photolysis of iron in acidic solutions results in the photodegradation of ametryne via reaction with cOH.…”

“…Triplet sensitizers accelerate the photodegradation of ametryne, 36,334,335 while the herbicide is relatively unreactive towards singlet oxygen 335,337 and CO 3 À c. 30 Photolysis of iron in acidic solutions results in the photodegradation of ametryne via reaction with cOH. 333,336 The photolysis of atraton has only been studied under environmentally relevant conditions using model sensitizers, rather than DOM. The photodegradation of atraton is accelerated in the presence of model triplet sensitizers.…”

“…335,338,340,[347][348][349]394 Direct photolysis is slow under environmentally relevant conditions, which is related to its minimal light absorption in the solar spectrum. 355 Atrazine photolysis rates can either be increased 74,113,130,162,245,259,338,339,341,342,[344][345][346] or decreased 66,333,340,343,346 in the presence of DOM. Indirect photolysis of the herbicide in the presence of nitrate, iron, or H 2 O 2 occurs mainly through reaction with photochemically-generated cOH, 70,259,336,340,344,345,355 with DOM decreasing observed photodegradation rates by competing with atrazine for cOH.…”

Potencial do processo foto-Fenton como etapa complementar ao tratamento de esgoto urbano e efluentes de indústria agroquímica

“…O processo foto-Fenton é reconhecidamente uma alternativa para tratamento de água contaminada por pesticidas em baixas concentrações (SORIANO-MOLINA et al, 2019). Estudos comprovaram a eficiência deste processo na remoção de várias classes de pesticidas incluindo produtos à base de AMT, ATZ, IMD e TBT presentes em água superficial (GARKUSHEVA et al, 2017;MCMARTIN et al, 2003;PULGARIN et al, 2016;SILVA et al, 2010). Portanto, o processo foto-Fenton aplicado de forma isolada ou combinado a outros processos de tratamento pode ser alternativa eficiente e deve ser avaliada para o tratamento de efluentes industriais agroquímicos contendo pesticidas em altas concentrações.…”