Herbicide Persistence in Seawater Simulation Experiments

• DOI: 10.1371/journal.pone.0136391
• Publication Date: 2015-08-27T18:04:43Z
• Authors: Philip Mercurio; Jochen F. Mueller; Geoff Eaglesham; Florita Flores; Andrew P. Negri
• Keywords: Persistence (discontinuity)

Herbicides are detected year-round in marine waters, including those of the World Heritage listed Great Barrier Reef (GBR). The few previous studies that have investigated herbicide persistence seawater generally reported half-lives order months, and several were too short to detect significant degradation. Here we eight herbicides commonly GBR or its catchments standard OECD simulation flask experiments, but with aim mimic natural conditions similar found on (i.e., relatively low concentrations, typical temperatures, light microbial communities). Very little degradation was recorded over 60 d period (Experiment 1) so a second experiment extended 365 d. Half-lives PSII ametryn, atrazine, diuron, hexazinone tebuthiuron consistently greater than year, indicating high persistence. detection atrazine diuron metabolites longer mercuric chloride-treated confirmed biodegradation contributed breakdown herbicides. shortest half-life 88 for growth-regulating 2,4-D at 31°C dark, while fatty acid-inhibitor metolachlor exhibited minimum 281 presence moderate elevated temperatures affected most herbicides; however, scale direction differences not predictable likely due changes community composition. estimates here represent some first appropriate data application risk assessments exposure tropical systems. long identified present study helps explain nearshore waters year round. Little these would be expected during wet season runoff associated flood plumes transporting proportion original from rivers into lagoon.