Influence of carbon and nitrogen application on the mineralization of atrazine and its metabolites in soil

Abstract

It has been proposed that levels of carbon and nitrogen in soil affect the rate at which triazine herbicides degrade. The present study was designed to investigate the effects of varying the levels of initial soil carbon and nitrogen as well as the effects of a later carbon addition on the mineralization of atrazine and its metabolites in soil. Atrazine degradation in soils amended with carbon as mannitol, and with nitrogen as urea, at levels of 10, 30, 50, or 80 mg kg−1 mannitol, urea, or mannitol and urea was similar to degradation in unamended soils. Only 39% of applied atrazine was mineralized after 326 days regardless of the initial carbon or nitrogen treatment. In contrast, a second mannitol amendment of 1 g kg−1 soil at day 140 increased [14C]carbon dioxide evolution by an additional 17% as a result of enhancing the mineralization rate of the atrazine metabolites. This conclusion is supported by our finding that periodic extraction of the soil with methanol followed by quantification on HPLC showed complete dissipation of the parent atrazine in 120 days. The metabolites hydroxyatrazine (HA), deisopropylatrazine (DIA), deethylatrazine (DEA), and diaminochlorotriazine (DACT) began to appear in the methanol extract 10 days following atrazine application. The greatest concentrations of HA, DEA, DIA. and DACT in the methanol extracts were 19, 12.4, 10.1, and 6.7% of applied atrazine, respectively. These concentrations were observed at day 95 except for DEA where the concentration continued to increase until day 142. A second soil extraction with hydrochloric acid (1m) + methanol (20 + 80 by volume) recovered additional HA, deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA), and DACT. When the extraction data were combined, 31.9, 12.4, 10.1. 10.2, 12.0 and 7.8% of applied atrazine was recovered as HA, DEA, DIA, DEHA. DIHA, and DACT, respectively. Combustion of the extracted soil showed 20% of the applied atrazine remained as soil‐bound residues after 326 days.

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

“…The presence of organic carbon sources stimulating atrazine degradation by microbial activity has been previously studied using citrate amendment (Jablonowski et al, 2008a;Silva et al, 2004) and other carbon compounds (Assaf and Turco, 1994b). Neither soil-intruded nutrients, such as plant detritus and root exudates of the annual corn plantations, nor regular fertilizer application, could promote complete atrazine degradation via biological or physico-chemical processes during more than 20 years under environmental influences.…”

“…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). The environmental behavior of atrazine by addition of organic amendments, like plant residues, or its mineralization during bioremediation, field application and agricultural use has been studied intensively (Alvey and Crowley, 1995;Barriuso and Houot, 1996;Silva et al, 2004).…”

Biostimulation for the Enhanced Degradation of Herbicides in Soil

“…Dicloflop, a postemergent herbicide, was readily mineralized by the bacterial degraders when supplied with an additional carbon source in the form of tryptic soy broth [55]. Assaf and Turco [56] observed that addition of mannitol (carbon source) to the soil after 140 days increased the [ 14 C] carbon dioxide evolution as a result of enhanced mineralization of atrazine. Better dealkylation of atrazine in adapted soil was Applied and Environmental Soil Science 5 [57][58][59] detected with the addition of a large amount of glucose [57].…”

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

“…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.…”