Brief descriptionThe key objectives of Project 3.2:
(1) Characterize the physical/optical properties of sediment suspensions;
(2) Map the dredge-generated plume;
(3) Provide data to optimize and validate plume modelling;
(5) Assess the spatial and temporal variability (~10 years) of background suspended sediment loads using archived remote sensing data;
(6) To estimate the benthic light field with respect to TSS;
In this study we investigated various common turbidity sensors, including optical scattering and acoustic scattering instrumentation, and compared and contrasted their effectiveness in estimating particle load (TSS concentration), and/or Particle Size Distributions (PSDs). Studies were conducted in a controlled laboratory-based setting with a range of different sediment types primarily obtained from the Pilbara coast.
More specifically we:
• determined the particle size (PS) of sediment samples from Pilbara coastal waters using a sequoia scientific LISST 100X submersible particle size analyser and related PS to the particulate backscattering slope (γbp parameter) of HobiLabs HydroScat-6 and the particulate scattering slope (γb parameter) of WETLabs acs-176;
• Established the relationship between Turb and TSS concentration using the optical properties of particulate backscattering coefficient (bbp), scattering coefficient (bb) and total absorptions (a) from HydroScat-6 and acs-176; Wetlabs ECO NTU and Campbell Scientific OBS3+.
LineageStatement: Sediment samples used in this experiment were obtained from the waters along the Pilbara coast near Onslow in northern Western Australia. Sediment samples from the field sites in Pilbara waters were collected in June 2014, March 2015 and July 2015 field campaigns (see final report).
The experiment was conducted using a large, 1.66 × 1.51 m fibreglass tank in the aquatic laboratory of Curtin University where optical instruments were positioned such that contamination of detectors due to light sources from neighbouring instrument was avoided. The cleaned tank was filled with 5 μm filtered sea-water and instruments were cleaned before placing each in their designated places. The stirrer was then turned on and allowed to run for 5 minutes before starting measurements. The instruments were run for at least 3 minutes to collect the ‘clean’ water measurements. Sediment samples (see Table 1) were divided into 10 or less portions and mixed with seawater in an effort to divide the sample into approximately even portions. A single portion of sediment sample was then added. Instrument outputs were monitored in real-time to observe the uniformity of data. Typically, a period of approximately 1 minute was required for the water to mix well and for the measurements to stabilize. The water was then allowed to mix for 2–3 minutes before water samples were taken, then an additional 2–3 more-minutes of instrument readings were taken. This step was repeated for each additional portion of sample added until all portions were finished. The instruments were then all stopped and taken out of the tank for downloading the data, cleaning and calibration if required. The process was repeated for each unique sample listed in Table 1 (see final report for full details)
- SBE 19 plus SeaCAT
- WetLabs ac-s
- HobiLabs Hydroscat-6
- AQUAscat 1000R
- Sequoia Scientific LISST 100X and data processing procedure
Modified: 16 10 2018
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(Link to final report)
- global : 4d961aed-906c-4777-927d-60fc243a318e