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Print version CEE 697z Organic Compounds in Water and Wastewater PCBs: Introduction and Properties Lecture #34 CEE 697z - Lecture #34

PCBs in the Lake Superior  Reference: Jeremiason, Hornbuckle and Eisenreich, Environmental Science and T echnology, 28:903 (1994) St. Mary’s River CEE 697z - Lecture #34

Empirical Models ( ) = ∑ ∑ − 0 20 . t PCB PCB e 25 25 o ( ) = ∑ ∑ − 0 22 . t PCB PCB e 82 82 o  Data tell us that about 26,500 kg has been lost from the water column between 1980 and 1992 CEE 697z - Lecture #34

Loss rates depend on specific congener Log Kow -0.6 -0.5 -0.4 k (/yr) k (yr-1) -0.3 k-regr. -0.2 Good correlation -0.1 with K ow 0 4.5 5 5.5 6 6.5 7 7.5 CEE 697z - Lecture #34

' ≡ dissolved toxicant c d Sorption c p ≡ particulate toxicant = φ and: c ' c d d  Definitions = + so: c c c T p d m k u Particle K  dissolved to particulate equilibrium ← → ' c c d p CEE 697z - Lecture #34

Langmuir Isotherm  At Equilibrium  Rate of adsorption = rate of desorption = R R ad de ( ) ν − ν = ν k M c k M  So, solving for the sorbed concentration ( ν ) ad s d m de s = ν c ν m d de + k c d k ad CEE 697z - Lecture #34

Limiting Cases  When C d is small, and there are lots of surface sites  Common situation for trace “toxics” like PCBs ν ν ν c c k ν = ≈ = m d m d m ad c + d k k c k de de k d k de ad ad ν = K d c d  So the bulk particulate concentration is: = ν = c m mK c p d d  And the total toxicant is: = + = + c c c c mK c T d p d d d CEE 697z - Lecture #34

Toxics: Linear sorption modeling  Now define c c ≡ = d d f + d c c mK c T d d d  adsorption model K m 1 = 1 = 1 d f f + + p d m m K K d d c = + = c = f c f f 1 f c d d T p p T d p CEE 697z - Lecture #34

1 = 1 f Estimation of partition coefficients + d K m d  Relationship to organic fraction −   mg tox . K =     − 3 m f K g C     or   − − mg tox .   d oc oc   g C   3 m  and properties of organic fraction Octanol:water partition − = 7 K 6 . 17 x 10 K coefficient oc ow  combining, we get:   − − = mg tox . 7   K 6 . 17 x 10 f K − 3  m Oct .  d oc ow −  .  mg tox   − 3   m H O 2 Karickhoff et al., 1979; Wat. Res. 13:241 CEE 697z - Lecture #34

Octanol:water partitioning  2 liquid phases in a separatory funnel that don’t mix  octanol  water  Add contaminant to flask  Shake and allow contaminant to reach equilibrium between the two  Measure concentration in each (K ow is the ratio) CEE 697z - Lecture #34

Observations  Summary of K ow and TSS effects  From Chapra, pg. 722 CEE 697z - Lecture #34

Box and Whisker Plots  Useful for summarizing non-ideal data distributions Thickness is proportional to the square root of the number of outlier observations x Median Upper data range Lower data range Upper quartile Lower quartile CEE 697z - Lecture #34

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