Abstract:
This roller tank experiment investigated the partitioning of different oil compounds (n-alkanes and polyaromatic hydrocarbons) between sinking marine oil snow, the unaggregated particles in the surrounding seawater and the dissolved water phase. Moreover, the effect of the dispersant Corexit on the occurring processes was investigated. For this experiment, a cyanobacterium culture (Nodularia) was used to form marine oil snow (MOS). The aim was to gain new insights into the oil incorporation mechanisms into marine snow.
Suggested Citation:
Uta Passow, Marisa Wirth, D. Schulz-Bull. 2017. Roller Tank Experiment for the component-specific Investigation of Oil Incorporation into Marine Oil Snow with a Phytoplankton Culture (Nodularia) (t = 24 hours). Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7TX3CTM
Data Parameters and Units:
a. Tank number b. Treatment= different treatments and controls were prepared (MilliQ Control = control tank containing only MilliQ water, Plankton Control = control tank containing only the plankton culture, OP = Oil and Plankton treatment, OPC = Oil, Plankton and Corexit treatment) c. Replicate = usually each fraction was sampled once for each tank; however, the PM fractions of the OP and OPC treatments were sampled three times each due to high heterogeneity d. Sample Type = in each treatment three different fractions were sampled: MOS = marine oil snow (aggregated, sinking particles > 1mm), PM = particulate matter < 1mm (unaggregated particles and oil drops), DP = dissolved water phase (everything that passes through a 0.7 µm filter) e. Sample volume (L) f. Entire fraction volume (L) g. DOC = dissolved organic carbon (mg/L) h. POC = particulate organic carbon (mg/L) i. Cell chain length = the total length of all Nodularia strands combined was measured for each sample (mm/mL) j. Naph = Naphthalene (ng/mL) k. Acy = Acenaphthylene (ng/mL) l. Ace = Acenaphthene (ng/mL) m. Fl = Fluorene (ng/mL) n. Phen = Phenanthrene (ng/mL) o. Ant = Anthracene (ng/mL) p. Fluo = Fluoranthene (ng/mL) q. Pyr = Pyrene (ng/mL) r. BaA = Benzo(a)anthracene (ng/mL) s. Chr = Chrysene (ng/mL) t. BbF = Benzo(b)fluoranthene (ng/mL) u. BkF = Benzo(k)fluoranthene (ng/mL) v. BaP = Benzo(a)pyrene (ng/mL) w. Ind = Indeno(1,2,3-c,d)pyrene (ng/mL) x. DBA = Dibenzo(a,h)anthracene (ng/mL) y. BP = Benzo(g,h,i)perylene (ng/mL) z-bd. Cx = n-alkane with x C-atoms and 2x+2 H-atoms
Methods:
Eight tanks (MilliQ control, Plankton control and three replicates for OP and OPC treatments) were filled bubble free with MilliQ water (MilliQ control) or plankton culture (Plankton control and OP and OPC treatments; salinity 7.2 PSU) and sealed. The MilliQ and Plankton control remained unchanged, but oil or oil and Corexit were slowly injected into the center of the already rotating tanks of the OP and OPC treatments. For the OP treatments, 50 µl of oil (Marlin Platform, Dorado source oil) and 20 µl of MilliQ water were injected. For the OPC treatments, 50 µl of oil, 3 µl of Corexit (Clean Seas) and 20 µl of MilliQ water were used. All tanks were incubated in the dark on the roller tables for 24 hours (until MOS had formed). The temperature was 24.3 °C. For sampling, tanks were carefully removed from the roller tables. All formed MOS > 1mm was collected manually with a cut-off pipette. Afterwards, the tanks were sealed again and the contents mixed. Subsamples from this surrounding seawater fraction were subsequently taken. Both the marine snow slurry and the surrounding seawater were filtered onto 0.7 µm borosilicate glass filters (Whatman, UK). Thereby, three different sample categories were obtained. The filtrate from the surrounding seawater was termed the dissolved phase (DP). The respective filter cake was termed particulate matter < 1 mm (PM). It contained unaggregated marine particles as well as oil drops, since they do not pass through the filter. The filter cake from the marine snow slurry was termed marine oil snow (MOS), the respective filtrate was discarded as it contained predominately DP. The pore water fraction of aggregates is too small to sample in this fraction. Subsamples of the MOS slurry and the surrounding seawater were fixed with Lugols solution and used for cell counting. For n-alkane and PAH analysis, DP samples were mixed with 225 µl of deuterated internal PAH standard solution (LGC Standards, UK). The samples were extracted twice with 10 mL dichloromethane (Prochem, Germany) and once with 10 mL hexane (Prochem, Germany) for 10 minutes each. The extracts were combined, dried over sodium sulfate (Merck, Germany) and concentrated to about 1 mL trough rotary evaporation. Subsequently, the solutions were purified over an aluminum oxide (Merck, Germany) and silica gel (Merck, Germany) column. The column was conditioned with 10 mL toluene (Prochem, Germany) and 10 mL heptane (Prochem, Germany). Analytes were eluted with 15 mL heptane and 30 mL of a heptane toluene mixture (2:1). The purified extracts were again concentrated to 1 mL. Filters (MOS and PM) were extracted with 15 mL dichloromethane and 15 mL hexane in an ultrasonic bath for 2 hours. The solvents were mixed with the same standard solutions. Afterwards, the samples were treated as described for the DP samples. The samples were measured for PAHs using a Trace DSQ GC-MS system (Thermo Scientific, Germany) equipped with an electron impact ionization source and single quadrupole detector that operates in the SIM mode. The compounds were separated with a 60 m DB-5MS column (Agilent, U.S.). The following PAHs were targeted: Naphthalene (Naph), Acenaphtylene (Acy), Acenaphthene (Ace), Fluorene (Fl) Phenanthrene (Phen), Anthracene (Ant), Fluoranthene (Fluo), Pyrene (Pyr), Benz(a)anthracene (BaA), Chrysene (Chr), Benz(b)fluoranthene (BbF), Benz(k)fluoranthene (BkF), Benz(a)pyrene (BaP), Indeno(1,2,3-c,d)pyren (Ind), Dibenzo(a,h)anthracene (DBA) and Benz(g,h,i)perylene (BP). A self-prepared mixture of internal (deuterated) and external PAH standard (LGC Standards, UK) was measured alongside the samples and used for quantification. The samples were measured for alkanes using a Trace GC Ultra system (Thermo Scientific, Germany) equipped with an FID detector. The analytes were separated with a 30 m DB-5MS column (Agilent, U.S.). The n-alkanes from n-Decane (C10H22) to n-Tetracontane (C40H82) were targeted. An external n-alkane standard (Ultra Scientific, U.S.) was measured alongside the samples and used for quantification. The DP samples were measured for dissolved organic carbon (DOC) and the MOS and PM samples for particulate organic carbon (POC). DOC measurements were carried out with a TOC-LCPH/TOC-VCPH TOC-Analyzer (Shimadzu, Germany). Samples were acidified with 80 µL of 2 N HCl to previously purge inorganic carbon. POC measurements were conducted with a varioMICRO cube element analyzer (Elementar Analysensysteme, Germany). Filters were dried for 30 min, acidified with 100 µL 2N HCl and incubated for 30 min. They were subsequently dried, folded and packed in tin containers for the subsequent measurement. Nodularia cells were enumerated in a 3 mL counting chamber for inverted microscopes at 100-fold magnification. The surrounding seawater samples (PM) were used at their full concentration; the MOS slurry samples were diluted 1:30 in Lugols solution. The total length of the Nodularia cell strands in different width size classes was determined in each sample. Sample losses: OP Tank 3 spilled during the experiment. Therefore, no data of this Tank is available.
View Metadata