Light-scattering Features of Turbidity- causing Particles in Interconnected Reservoir Basins and a Connecting Stream Upstate Freshwat er Inst. Feng Peng and Steven W. Effler Upstate Freshwater Institute, Syracuse, New York Donald C. Pierson NYC Department of Environmental Protection David G. Smith National Institute of Water and Atmosphere, New Zealand
Upstate Freshwater Inst. Light-scattering Features of Turbidity-causing Particles in Interconnected Reservoir Basins and a Connecting Stream. Feng Peng and Steven W. Effler Upstate Freshwater Institute, Syracuse, New York Donald C. Pierson NYC Department of Environmental Protection - PowerPoint PPT Presentation
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Light-scattering Features of Turbidity-causing Particles in Interconnected Reservoir
Basins and a Connecting Stream
UpstateFreshwaterInst.
Feng Peng and Steven W. EfflerUpstate Freshwater Institute, Syracuse, New York
Donald C. PiersonNYC Department of Environmental Protection
David G. SmithNational Institute of Water and Atmosphere, New Zealand
Study System turbidity as a water quality issue
Character of Light-scattering (Turbidity-causing) Particles within the Catskill System
Related questions
What are the light-scattering characters of particles (size distributions, composition, shape) in the Catskill system?
Are there differences in the light scattering characteristics of particles in different parts of the Catskill System?
Does the potential difference cause disproportionate contributions of the source particles to turbidity (Tn) within the system?
Turbidity (Tn): A Measure of Light Scattering
(light scattering coefficient, b; m1)
Tn measured at acceptance angle centered at 90 (“side-scattering”)
Tn b
0º
90º
Light scattering coefficient (b) depends on four features of particle population
1. particle number concentration (N)2. particle size distribution (PSD)3. particle composition (i.e., refractive index)4. particle shape
Particle characterizations• bulk measurements of mass (TSS) and mass
fractions; disconnect with light scattering• PSDs counters; size limitations, no chemical
composition• SAX§ individual particle analysis; N, PSD,
composition, and shape
Particles and Light Scattering : Dependencies and Analytical Support
§ scanning electron microscopy interfaced with automated image and X-ray analyses
Individual Particle Analysis (IPA)
by Scanning electron microscopy
interfaced
with Automated image and X-ray analyses
(SAX)
Detailed compositional and morphological analyses
SAX Characterizations§
• Chemical (elemental X-rays) 5 inorganic particle types,
including clay minerals, quartz
• Morphological rotating chord algorithm
PAi sum of all triangular areas
di area equivalent diameter
shape “nonsphericity”,
ASP (aspect ratio) = Dmax/Dperp
• >1,000 particles analyzed in each sample
§ Peng and Effler (2007) Limnol. Oceangr. 52: 204216. Peng et al. (2009) Water Res. 43: 22802292.
0.0 0.5 1.0 1.5 2.0 2.5 3.00
500
1000
1500Si
X-r
ay C
ounts
keV
Al
V sample volume N number of particles per unit volume of waterQb,i light scattering efficiency of particle i; Mie theory
mi (complex) relative refractive index of particle i
(ni in); depending on composition
wavelengthdi size of particle i
PAi projected area of particle i
Calculation of b from SAX Measurements
according to light scattering theory
b,1
1( ) ( , , ) PA
N
i i i ii
b Q m dV
light
System Configuration,
and Sampling (2005) for
SAX Characterizations
Sites (n = 9)
Schoharie site 3 and withdrawal
Esopus AP (above portal), E16i
Ashokan sites 3 and 1 (W. basin),
site 4 (E. basin)
Kensico sites 4.2 and 4.1
Runoff Conditions (Q)
low Q and Tn; high Q and Tn
Tunnel Operations
on/off
SchoharieRes.
AshokanRes.
KensicoRes.
EsopusCreek
ShandakenTunnel
CatskillAqueduct
Dependency of b on Size(calculated from SAX results)
properties of the suspended particles throughout the Catskill system over a wide range of turbidity – composition (clay minerals dominating)– size distribution– shape
• Similar potencies of particle populations in upstream vs. downstream turbidity sources
• Findings support– direct incorporation of Tn measurements into loading
calculations to evaluate source impacts– parameterization of mechanistic turbidity models; e.g.,
representations of particles in the turbidity models for Schoharie, Ashokan, and Kensico
• Published manuscriptPeng, F., S.W. Effler, D. C. Pierson, and D. G. Smith. 2009. Light-scattering features of turbidity-causing particles in interconnected reservoir basins and a connecting stream. Water Research 43(8): 2280–2292.