Authors / CoAuthors
Unknown
Abstract
Sniffer Files The 'Sniffer' or Direct Hydrocarbon Detection (DHD) technique used to detect hydrocarbon seepage offshore involves towing a submerged tow-fish close to the seafloor and continuously pumping seawater into a geochemical laboratory on board where the hydrocarbons are extracted and measured by gas chromatography. The Direct Hydrocarbon Detection (DHD) method continuously analyses C1-C8 hydrocarbons within seawater. The method used on the RV Rig Seismic is as follows. Seawater is continuously delivered into the geochemical laboratory onboard the ship via a submersible fish (which is towed approximately 10 m above the seafloor). The seawater is degassed in a vacuum chamber and the resulting headspace gas is injected into three gas chromatographs, which sequentially sample the flowing gas stream and measure a variety of light hydrocarbons. Total hydrocarbons (THC) are measured every thirty seconds, light hydrocarbons (C1-C4) are measured every two minutes and C5 to C8 are measured every 8 minutes. Fluorometer and Aquatrack Fil In October 1998, the Australian Geological Survey Organisation (AGSO) carried out field trials of three commercially available towed fluorometers; Aquatracka (Chelsea Instruments), SAFIRE (WetLabs), FLF (WetLabs). These instruments were pre-selected on manufacturer specifications as potentially the most suitable, compared to other fluorometers currently on the market, for the detection of polycyclic aromatic hydrocarbons (PAH) present in crude oils seeping into the marine environment. The fluorometers were set with an excitation wavelength in the range 239 nm to 260 nm and fluorescence was monitored over the range 340 nm to 360 nm. SAFIRE is a multi-wavelength instrument, which enabled simultaneous use of several excitation and emission wavelengths. All three fluorometers were mounted on deck and seawater was pumped through them. The Aquatracka instrument analysed deep water pumped to the surface by the "Sniffer" submersible system.
Product Type
dataset
eCat Id
77076
Contact for the resource
Custodian
Point of contact
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Keywords
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- GIS Dataset
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2013-08-20T00:00:00
Creation Date
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Status
Purpose
Maintenance Information
notPlanned
Topic Category
geoscientificInformation
Series Information
Lineage
Sniffer Data - Both Point and Line data A detailed description of the history of this data set can be found in "North West Shelf, Australia, Sniffer and Fluorometer Direct Hydrocarbon Detection Data", by MP Morse, AGSOCAT 34452 (unpublished). In summary the data from each survey was mapped to a consitent format and given a unique line number. A common subset of the parameters used by AGSO for seepage studies was extracted from each survey. These where then combined into one Microsoft Excel spreadsheet. The original survey data can be found on the data CD that is part of the AGSOCAT 34452. Aquatrack - Point data The acquisition of these data was synchronised with the "sniffer" operation and recorded as part of that system. These data were archived seperately from the "sniffer" data and also mereged with the other fluorometer data as Microsoft Excel spreadsheets. Fluorometer - Point Data The FLF and SAFIRE data sets were acquired using there own proprietary acquisition systems as time based data. Positions for these data were interpolated from the navigation data recorded with the Aquatracka and "sniffer" data on the same survey. This was done by matching the time data for each data set. The Aquatracka, FLF, and Safire data were then interleaved in time to create this dataset.
Parent Information
Extents
[-17.0, -8.7, 121.0, 127.5]
Reference System
Spatial Resolution
Service Information
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Unknown