Chemical versus microbial degradation of cyanazine and atrazine in soils

Abstract

A laboratory study was performed to investigate the relationship between chemical (non‐biological) and microbial degradation of cyanazine and atrazine in soils ranging in pH from 5.3 to 8.1. Atrazine degradation was dominated by chemical processes in both a moderately acidic and a neutral pH soil, but showed a significant microbial involvement in the neutral pH soil. The primary cyanazine degradative mechanism was dependent on soil properties. Cyanazine was short‐lived in neutral to slightly basic soils, due to rapid microbial degradation. Cyanazine amide and cyanazine acid were the major metabolites formed. In a moderately acidic soil, microbial degradation was slowed and chemical processes were the primary means of cyanazine degradation.

Degradação e formação de resíduos não-extraíveis ou ligados do herbicida atrazina em solo

“…Ambos metabólitos parecem ter sido também degradados com o tempo e em todas as amostras, pois as porcentagens detectadas no T.56 diminuíram em relação ao T.28 (Tabela 2). Como a conversão da atrazina em metabólitos ocorreu tanto nas amostras de solo Glei Húmico esterilizado como no natural, provou-se que a presença de microrganismos não Natural foi fator decisivo, e uma parte do processo de degradação pode ter sido puramente química, conforme também observado por outros autores (Blumhorst & Weber, 1994;Andréa et al, 1997).…”

“…A degradação a hidroxiatrazina é importante do ponto de vista de rotação de culturas, porque representa destruição da fitotoxicidade da atrazina (Winkelmann & Klaine, 1991;Blumhorst & Weber, 1994). Além disso, a porcentagem de hidroxiatrazina pode também estar relacionada à formação de resí-duos ligados, pois em estudo de Andréa et al (1997), mais de 90% dos resíduos ligados de atrazina em solo eram hidroxiatrazina.…”

“…A formação de resíduos não-extraíveis ou ligados de atrazina foi observada por vários autores (Kruger et al, 1993;Assaf & Turco, 1994;Blumhorst &Weber, 1994;Nakagawa et al, 1995;Barriuso & Koskinen, 1996;Kruger, et al, 1997;Andréa et al, 1997). No Brasil, Nakagawa et al (1996) verificaram a formação de 61% e 82% de resíduos ligados do herbicida atrazina, 400 dias após a aplicação em solo Glei Húmico e Latossolo Vermelho-Escuro, respectivamente.…”

Persistence of 14C-labeled atrazine and its residues in a field lysimeter soil after 22years

“…Although atrazine has been the subject of multiple investigations, its long-term environmental behavior is still not clear. Most findings regarding fungal or microbial (Kaufmann and Blake, 1970;Mandelbaum et al, 1993;Assaf and Turco, 1994a) and chemical (Blumhorst and Weber, 1994) degradation are based on laboratory or short-term field experiments which have limited relevance to long-term outdoor trials. The estimated half-life of atrazine from these short-term tests ranges between a few days to about one year (Kruger et al, 1993;Accinelli et al, 2001), depending on application history (Shaner and Henry, 2007), soil depth (Miller at al., 1997), soil moisture content (Kruger et al, 1993), temperature (Dinelli et al, 2000), pH and presence of other nutrients such as nitrogen or carbon (Abdelhafid et al, 2000;Assaf and Turco, 1994b;Gan et al, 1996;Moorman et al, 2001;Alvey and Crowley, 1995).…”

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“…It proved the significance of inorganic soil contents for abiotic atrazine degradation (Skipper et al, 1967). Differing to these reports atrazine degraded chemically in the moderate acidic condition in the ground (Blumhorst and Weber, 1994). In the company of humic substances as well as in acidic or basic conditions favors the chemical hydrolysis (Kadian et al, 2008).…”