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Surface water mineralization of isopyrazam according to OECD 309: Observations on implementation of the new data requirement within agrochemical regulation
Author(s) -
Hand Laurence H.,
Moreland Harriet J.
Publication year - 2014
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.2490
Subject(s) - environmental chemistry , light intensity , mineralization (soil science) , environmental science , surface water , degradation (telecommunications) , phototroph , sediment , chemistry , photosynthesis , environmental engineering , soil science , biology , computer science , telecommunications , paleontology , biochemistry , physics , optics , soil water
A surface water mineralization study (according to the Organisation for Economic Co‐operation and Development [OECD] guideline OECD 309) is a new requirement in European Union agrochemical regulations; therefore, industry has little experience with this test. The guideline allows for a number of options within the test design, notably the options to conduct the study under diffuse light and to include an inoculum of suspended sediment. The present study was designed to investigate the potential impact of these options on the degradation rate of a representative compound. The fungicide, isopyrazam, was chosen as it was previously shown to be susceptible to metabolism by phototrophic organisms under a fluorescent light–dark cycle. The impact of diffuse light was investigated at light intensities representative of those at depth in large, open water bodies (<7% of the incident intensity), and it was demonstrated that metabolism of isopyrazam by phototrophic microorganisms was rapid (median degradation time for 50% of the test compound [DT50] < 50 d), whereas degradation in continuous darkness was negligible. Furthermore, investigation at 2 different light intensities resulted in similar degradation rates, indicating that this transformation mechanism was not proportional to light intensity, provided that there was sufficient light for photosynthesis to occur. Inclusion of suspended sediment did not have a significant impact on the degradation rate of isopyrazam, except at extremely high sediment concentrations, which were not considered representative of conditions in large, open water bodies. Environ Toxicol Chem 2014;33:516–524. © 2013 SETAC