title: Fate and transport of Irgarol 1051 in a modular estuarine mesocosm.
abstract: Fate and transport of Irgarol 1051 were assessed using a modular estuarine mesocosm containing natural seawater, saltmarsh sediments, marsh grass, shrimp, clams, snails, and naturally derived planktonic and benthic microorganisms. The mesocosms were enclosed in a greenhouse under near ambient conditions, and included a saltwater sump and a simulated tidal flux. The exposure was comprised of four replicate treatments of 0, 100, 1,000 and 10,000 ng/L Irgarol. Solid-phase extraction (SPE) was used to extract Irgarol and its major metabolite M1 (aka GS26575) from water samples. Sediment samples were extracted using Accelerated Solvent Extraction (ASE) with 100% dichloromethane. Irgarol and M1 were separated and quantified utilizing Liquid Chromatography Tandem Mass Spectrometry (LC-MS-MS) with ElectroSpray Ionization in Multiple Reaction Monitoring mode. Aqueous concentrations of Irgarol declined rapidly (average 93% loss) over the course of the 35 day experiment while Irgarol was accumulated in the sediments (average mass balance of 75 +/- 5%). Loss of aqueous Irgarol occurred in two distinct phases, a relatively rapid phase up to 96 hours post-dose, and a slower phase following 96 hours. The rate constants of the initial rapid degradation phase (k(1)) for treatments 100 and 1,000 ng/L Irgarol were 2-3 times higher than the rate constants of the subsequent slow degradation phase (k(2)) for these treatments. The average half-life of Irgarol in water was 7 +/- 3 days. The aqueous concentration of Irgarol's metabolite, M1 increased over the course of the experiment. By 35 days post-dose, M1 concentrations in water averaged about 3% of the parent compound. M1 also accumulated in mesocosm sediments (average 16.7 +/- 2.5% of total Irgarol dose). Mass balance calculations showed that by 35 days, Irgarol and M1 amounts in mesocosm water and sediments were close to 100% of the initial Irgarol dose. Average partition coefficient normalized for organic carbon (log K(oc)) calculated for Irgarol was 3.2 +/- 0.1 for 35 days post-dose. Accumulation of Irgarol and M1 in mesocosm sediments may warrant further study to assess toxicity for benthic communities.
authors: JHT Inc., (Contractor to NOAA), 331 Fort Johnson Rd., Charleston, SC 29412, USA. yelena.sapozhnikova@noaa.gov
authors: Yelena
authors: Y
authors: Sapozhnikova
authors: Paul
authors: P
authors: Pennington
authors: Edward
authors: E
authors: Wirth
authors: Michael
authors: M
authors: Fulton
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology; D006109:Poaceae / Q000737:chemistry / Q000378:metabolism; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology; D052616:Solid Phase Extraction; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014227:Triazines / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D014872:Water Movements
chemical_list: D014227:Triazines; C103341:irgarol 1051