13C/12C and 15N/14N Isotope Analysis To Characterize Degradation of Atrazine: Evidence from Parent and Daughter Compound Values

• Published in: Environmental science & technology Vol. 47; no. 13; pp. 6884 - 6891
• Main Authors: Meyer, Armin H, Elsner, Martin
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02.07.2013
• Subjects: Applied sciences; Atrazine - chemistry; Atrazine - metabolism; Carbon Isotopes; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Groundwaters; Herbicides - chemistry; Herbicides - metabolism; Manganese Compounds - chemistry; Natural water pollution; Nitrogen Isotopes; Oxides - chemistry; Pollution; Pollution, environment geology; Rhodococcus - metabolism; Water treatment and pollution; Microbial activity; Isotopic analysis; Agricultural chemical product; Metabolite; Rhodococcus; Nitrogen isotopes; Carbon isotopes; Chemical pollution; Selfpurification; Stable isotopes; Reaction mechanism; Bacteria; Oxidation; Organic compounds; Biodegradation; Permanganates; Pollutant behavior; Pesticides; Endocrine disruptor; Chemical degradation; Herbicide; Carcinogen; Triazine derivatives; Actinomycetes; Degradation product; Atrazine
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es305242q

Atrazine (Atz) and its metabolite desethylatrazine (DEA) frequently occur in the environment. Conclusive interpretation of their transformation is often difficult. This study explored evidence from 13C/12C and 15N/14N isotope trends in parent and daughter compounds when Atz was dealkylated by (i) permanganate and (ii) the bacterium Rhodococcus sp. NI86/21. In both transformations, 13C/12C ratios of atrazine increased strongly (εcarbon/permanganate = −4.6 ± 0.6‰ and εcarbon/Rhodoccoccus = −3.8 ± 0.2‰), whereas nitrogen isotope fractionation was small. 13C/12C ratios of DEA showed the following trends. (i) When DEA was formed as the only product (Atz + permanganate), 13C/12C remained constant, close to the initial value of Atz, because the carbon atoms involved in the reaction step are not present in DEA. (ii) When DEA was formed together with desisopropylatrazine (biodegradation of Atz), 13C/12C increased but only within 2‰. (iii) When DEA was further biodegraded, 13C/12C increased by up to 9‰ giving strong testimony of the metabolite’s breakdown. Two lines of evidence emerge. (a) Enrichment of 13C/12C in DEA, compared to initial Atz, may contain evidence of further DEA degradation. (b) Dual element (15N/14N versus 13C/12C) isotope plots for dealkylation of atrazine agree with indirect photodegradation but differ from direct photolysis and biotic hydrolysis. Trends in multielement isotope data of atrazine may, therefore, decipher different degradation pathways.