esm222_19case_studies2

esm222_19case_studies2 - ESM 222 Case Studies Resuspension...

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1 © Arturo A. Kel er ESM 222 Case Studies #2 2 © Arturo A. Kel er Case Studies Resuspension of River Sediment Containing Benzo(a)Pyrene ± Another coal gasification plant which operated for 60 years was located next to the Watford River (used for cooling water) ± River sediments contain Benzo(a)Pyrene, another PAH which is quite toxic 3 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± Approximately 60 m of river in front of power plant contain BaP in sediments ± Upstream flood channel work caused erosion in this region of river, resuspending sediments ± Sediment load increased by 20 mg/L in vicinity of power plant 4 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene 5 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± Over next 6 km of river, there was a net loss of 15 mg/L of suspended sediments ± What is concentration of BaP in river downstream from site? ± How much is dissolved in river? 6 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± Site information: ± River velocity = 0.3 m/s ± Settling velocity of sediments, v sed = 1 m/day ± River depth, H = 1.5 m ± River volumetric water flow rate = 25 m 3 /s ± Suspended sediment conc., C ss = 110 mg/L, upstream of plant Sedimentation rate, k sed = v sed C ss /0.5H Pollutant removal via sedimentation = k sed C s
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7 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± Site information: ± fine sediment = 80% by mass ± f oc,f (fine sediment) = 0.08 ± f oc,c (coarse sediment) = 0.03 ± concentration of BaP in river bed = 1,000mg/kg ± density of river bed sediments = 1,200 kg/m 3 8 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± Physicochemical data: ± C w sat = 0.0038 mg/L ± P sat = 7 x 10 -12 atm ± K H = 0.000018 ± K ow = 10 5.97 = 933,000 Benzo(a)Pyrene 9 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± Volatilization is not significant and can be neglected ± Sorption will be a major process ± Desorption will occur, to a small extent (although this analysis doesn’t include the rate of desorption, this may be an important factor in determining the actual concentrations) 10 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± To calculate K d , we consider both types of sediments: K d = 0.63 x 10 -3 K ow [(0.8) f oc,f + (0.2) f oc,c ] m 3 /kg = 38 m 3 /kg K d = C s /C w R = 1 + (ρ s K d / q) = 45,601 (most BaP travels sorbed in sediment) C w » 0.0026 mg/L 11 © Arturo A. Kel er River Sediment Containing Benzo(a)Pyrene ± In terms of reactions ± hydrolysis doesn’t occur ± no known biodegradation rate (or it is very, very small) ± Photolysis is the only possible
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This note was uploaded on 08/06/2008 for the course ESM 222 taught by Professor Keller during the Spring '08 term at UCSB.

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esm222_19case_studies2 - ESM 222 Case Studies Resuspension...

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