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Environmental Biomonitoring, Sampling, and Testing
Published in Frank R. Spellman, The Science of Water, 2020
Turbidity is generally measured by using a turbidity meter or turbidimeter. The turbidimeter is a modern nephelometer [originally, a box containing a light bulb which directed light at a sample. The amount of light scattered at right angles by the turbidity particles was measured, as a measure of the turbidity in the sample, and registered as Nephelometric Turbidity Units (NTU).] The turbidimeter uses a photoelectric cell to register the scattered light on an analog or a digital scale, and the instrument is calibrated with permanent turbidity standards composed of the colloidal substance, formazin. Meters can measure turbidity over a wide range—from 0 to 1,000 NTUs. A clear mountain stream might have a turbidity of around 1 NTU, whereas a large river like the Mississippi might have a dry-weather turbidity of 10 NTUs. Because these values can jump into hundreds of NTUs during runoff events, the turbidity meter to be used should be reliable over the range in which you will be working. Meters of this quality cost about $800. Many meters in this price range are designed for field or lab use.
Process Parameters Monitoring and Control
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
The cloudy or milky appearance of liquid or solid media is expressed as “turbidity.” This turbidity is due to the presence of suspended particles such as microorganisms and sludge. It is based on the scattering or absorption of light by the suspended particles in solution. The transmitted intensity can be determined from the Beer–Lambert equation. This measured intensity of transmitted light is a function of the concentration of dispersed phase. The Nephelometric Turbidity Unit (NYU)/Formazin Turbidity Unit (FNU) is used to measure the intensity of the suspended matters present in the medium. Microbial cells usually remain in suspension in the medium. A turbidity meter is calibrated by using a standard solution prepared with a formazin polymer suspension in water (Fig. 10.7).
Static water levels and geochemical field parameters
Published in Neal Wilson, Soil Water and Ground Water Sampling, 2020
Turbidimeters should be operated in accordance with the manufacturer’s operating instructions. In the absence of a precalibrated scale, calibration curves are prepared by using a reagent grade Formazin standard or styrene divinylbenzene beads. Formazin is a carcinogen, so it must be carefully handled. Air bubbles, floating or suspended solids, and turbulent motions may cause false readings from a nephelometer. The sample tubes must not be handled where the light contacts them and must be kept scrupulously clean inside and out. Tubes should be discarded if they become scratched or etched.
The unfulfilled promise of urban Lake Kleine Melanen (The Netherlands): Diagnostics, experiment on reduction of sediment P-release and in-lake restoration
Published in Lake and Reservoir Management, 2018
Guido Waajen, Miquel Lürling, René van de Sande
Prior to the enclosure experiment, the lake was sampled 11 d before the start of the experiment (day −11). The enclosures and the lake were sampled on day −4 and on days 0, 1, 4, 11, 24, 45, 59, and 87 at a water depth of 0.3 m. Samples were taken in the morning (between 08:00 and 12:00 h). At day −4, the samples from the enclosures were taken 1.5 h after the addition of the sand, while at day 0 the samples were taken 1.5 h after the addition of the LMB and PAC. TP and total nitrogen (TN) concentrations were analyzed in unfiltered samples and OP in filtered samples (0.45 µm membrane filter, Polydisk) using a continuous flow analyzer (Skalar Analytical BV, Breda, The Netherlands) following the Dutch standard protocols (NNI 2005a, 2005b, 2006a). Chl-a concentrations were determined in the laboratory with a PHYTO-PAM phytoplankton analyzer (Heinz Walz GmbH, Effeltrich, Germany), differentiated into cyanobacteria, green algae, and diatoms, and calibrated against the Dutch standard procedure (NNI 2006b). The sum of the Chl-a concentrations from cyanobacteria, green algae, and diatoms is referred to as total Chl-a concentration. Turbidity was measured using a Hach 2100P turbidity meter in Formazin Turbidity Units (FTU). Total lanthanum (TLa) analysis was conducted in unfiltered samples and filterable La (FLa) in filtered samples (0.45 µm membrane filter, Polydisk) according to NNI (2009) by inductively coupled plasma optical emission spectrometry ICP-OES (detection limits 6–12 µg/L). On every sampling date, the pH and oxygen (O2) concentrations were determined in situ using a WTW Multi 350i meter (WTW, Weilheim, Germany). Filterable aluminum (Al) was analyzed in filtered samples (0.45 µm membrane filter, Polydisk) by ICP-MS according to NNI (2004).