Comparison of fluvial suspended-sediment concentrations and particle-size distributions measured with in-stream laser diffraction and in physical samples

Czuba, Jonathan A.; Straub, Timothy D.; Curran, Christopher A.; Landers, Mark N.; Domański, Marian

doi:10.1002/2014wr015697

Cited by 42 publications

(70 citation statements)

References 41 publications

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“…Although benchtop instruments may be able to measure over a wider size range, the LISST 100X was chosen for its in‐situ deployment capability. This instrument has been evaluated and used extensively for freshwater systems (Agrawal & Hanes, ; Czuba, Straub, Curran, Landers, & Domanski, ; Filippa et al, ; Guo & He, ; Williams, Walling, & Leeks, ).…”

Section: Methodsmentioning

confidence: 99%

Response of suspended sediment particle size distributions to changes in water chemistry at an Andean mountain stream confluence receiving arsenic rich acid drainage

Abarca

Guerra

Arce

et al. 2016

Hydrological Processes

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Acid drainage is an important water quality issue in Andean watersheds, affecting the sustainability of urban, agricultural, and industrial activities. Mixing zones receiving acid drainage are critical sites where changes in pH and chemical environment promote the formation and dissolution of iron and aluminum oxy/hydroxides. These particles can significantly change the speciation of toxic metals and metalloids throughout drainage networks via sorption, desorption, and settling processes. However, little is known about the behavior of particle size distributions (PSDs) in streams affected by acid drainage and their relationship to metal speciation. This work studied: (a) the PSDs for a wide range of mixing ratios found at a fluvial confluence affected by acid drainage, and (b) the response of PSDs and arsenic speciation to environmental changes found when the particles approach complete mixing conditions. The confluence between the Azufre River (pH ~ 2, high concentration of dissolved metals) and Caracarani River (pH = 8.6, low concentration of dissolved metals) was used as a representative model for study. Field measurements show a bimodal PSD with modal diameters of ~50 and 300 μm. At shorter distances from the junction, the smaller modes with smaller particle volumes were dominant across the stream cross‐sections. A systematic shift towards larger particle sizes and larger particle volumes occurred downstream. The analysis of laboratory PSDs for Azufre/Caracarani mixing ratios between 0.01 and 0.5 (pH from 6.2 to 2.3) showed a bimodal trend with ~15 and 50 μm characteristic diameters; larger particles formed at pH>4. When particle suspensions were transferred in laboratory experiments from very low pH to full mixing conditions (pH ~ 2.8 and mixing ratio ~ 0.25) particle sizes varied, and the dissolved arsenic concentration decreased. The observed reaction kinetics were slow compared to the time scale of advective transport, creating opportunities for engineered controls for arsenic. This work contributes to a better understanding of the chemical‐hydrodynamic interactions in watersheds affected by mining, and identifying opportunities to improve water quality at points of use.

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Section: Methodsmentioning

confidence: 99%

Response of suspended sediment particle size distributions to changes in water chemistry at an Andean mountain stream confluence receiving arsenic rich acid drainage

Abarca

Guerra

Arce

et al. 2016

Hydrological Processes

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“…Czuba et al . [] studied mass density in a survey of a number of U.S. rivers with a LISST‐SL, and reported a substantially reduced “effective” density as a nation‐wide average. In the case of present data, for a cross comparison, USGS personnel employed P‐61 samplers to grab water samples to get independent measures of mass concentrations.…”

Section: Field Measurements Of Sediment Size Distribution and Concentmentioning

confidence: 60%

“…Czuba et al . [] postulate this reduced apparent density being due to flocculation, shape effects, or unmeasured size fractions. Felix et al .…”

Section: Field Measurements Of Sediment Size Distribution and Concentmentioning

confidence: 99%

The implications of laser‐diffraction measurements of sediment size distributions in a river to the potential use of acoustic backscatter for sediment measurements

Agrawal

Hanes

2015

Water Resources Research

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We construct vertical profiles of the acoustic attenuation and back‐scattering properties of a river column from measured particle concentration and size distribution profiles. The particle size and concentration data were collected in situ in the Cowlitz River in Washington, U.S., using a laser diffraction‐instrument LISST‐SL. The particle size distribution was bimodal, comprising a vertically well‐mixed washload, and a suspended load that was similar to Rouse profiles. We then explore how well the results of converting these synthetic profiles to recover an acoustic equivalent sediment concentration and acoustic equivalent size compare with laser data in this bimodal environment. The acoustic scattering and attenuation properties are computed for four distinct frequencies: 0.5, 1, 3, and 5 MHz. It is seen that at the lowest frequency, 500 KHz, the acoustic attenuation throughout the water column is nearly constant and determined primarily by particles of size smaller than ∼30 microns, i.e., the washload. At the next higher frequency, 1 MHz, the suspended load also contributed to attenuation, but even so, attenuation remained nearly constant over the vertical profile. Thus, at the two lower frequencies, attenuation was decoupled from scattering, making the inverse problem explicit for inversion. In contrast, at the two highest frequencies, scattering of sound by the suspended mode became the dominant contributor to attenuation, and attenuation varied by an order of magnitude over river depth. As for backscatter, the computed acoustic backscatter strength was determined by a combination of the washload and suspended sediment mode at all four frequencies. A fairly narrow monotonic relationship was found between total sediment concentration and locally computed backscatter, effectively providing a calibration between local backscatter signal strength and suspended sediment concentration. Such a relationship existed throughout the water column, for every frequency. The sediment concentration derived from backscatter at a pair of frequencies was within ∼50% of the value measured by laser diffraction; however, the acoustic equivalent diameter exceeded the laser volume mean diameter by up to an order of magnitude. The robustness of these results for application to other flow regimes or rivers remains to be investigated.

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“…Indeed, the measurement range is 2.07-350 µm with limitations on the actual concentrations: inaccuracies may rise from multiple light scatter and too low scatter, which fix low and high threshold concentrations, respectively [44]. These limitations rise doubts on the opportunity of having detailed PSDs carefully profiled with punctual sampling by a LISST-SL rather than an estimation of sand and clay-silt concentrations along beams by applying an acoustic method.…”

Section: Recommendationsmentioning

confidence: 99%

The Acoustic Properties of Suspended Sediment in Large Rivers: Consequences on ADCP Methods Applicability

Guerrero

Rüther

Szupiany

et al. 2016

Water

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Abstract:The use of echo-levels from Acoustic Doppler Current Profiler (ADCP) recordings has become more and more common for estimating suspended bed-material and wash loads in rivers over the last decade. Empirical, semi-empirical and physical-based acoustic methods have been applied in different case studies, which provided relationships between scattering particles features derived from samples (i.e., concentration and grain size) and corresponding backscattering strength and sound attenuation. These methods entail different assumptions regarding sediment heterogeneity in the ensonified volume (e.g., particle size distribution (PSD) and spatial concentration gradient). Our work was to compare acoustic backscatter and attenuation properties of suspended sediments, sampled in the rivers Parana and Danube that represented rather different hydro-sedimentological conditions during the surveys. The Parana represents a large sandy river, characterized through a huge watershed and the typical bimodal PSD of sediment in suspension, while the Danube represents in the investigated reach an exposed sand-gravel bed and clay-silt particles transported in the water column in suspension. Sand and clay-silt concentrations clearly dominate the analyzed backscattering strength in the rivers Parana and Danube, respectively, with an effect of PSD level of sorting in the latter case. This comparison clarifies the extent of assumptions made, eventually advising on the actual possibility of applying certain ADCP methods, depending on the expected concentration gradients and PSD of suspended sediment to be investigated.

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Comparison of fluvial suspended-sediment concentrations and particle-size distributions measured with in-stream laser diffraction and in physical samples

Cited by 42 publications

References 41 publications

Response of suspended sediment particle size distributions to changes in water chemistry at an Andean mountain stream confluence receiving arsenic rich acid drainage

Response of suspended sediment particle size distributions to changes in water chemistry at an Andean mountain stream confluence receiving arsenic rich acid drainage

The implications of laser‐diffraction measurements of sediment size distributions in a river to the potential use of acoustic backscatter for sediment measurements

The Acoustic Properties of Suspended Sediment in Large Rivers: Consequences on ADCP Methods Applicability

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