Several sediment samples were collected and analyzed for TCE and a concentration
ID: 527394 • Letter: S
Question
Several sediment samples were collected and analyzed for TCE and a concentration versus depth profile was prepared from the data. The resulting profile was a straight, non-vertical line with the lowest concentrations near the sediment-water interface (i.e. the concentration increased with depth). This suggests that: a. the system (sediment, pore water and overlying water) was not at equilibrium b. the system was at steady-state c. the sediments are losing TCE into the water column d. all of the above If the concentration of chlorobenzene (solubility = 466 mg/L; vapor pressure equivalent to 75 mg/L; K_oc = 126) in the water column of a pond were 1 mg/L and the concentration in the sediment (infinity = 0.04) were 10 mg/kg would the flux across the sediment-water interface be into or out of the sediment? Explain. Assume an explosion in the air results in the spike input of 20 g of chlorobenzene into the atmosphere over a diameter 2 m. Estimate the diameter of the plume after 1 day(m) assuming dispersion coefficients (E_f, E_v and E_l) 10^4 cm^2/s.Explanation / Answer
Answer 7)
Considering all option step by step:
a) System was not at equilibrium:
Explanation: System is not at equilibrium since the concentration is of TCE is increasing with depth of sedimentation.
b) System is at steady state:
It is at steady state since the sediments have settled and there is no change in velocity.
c) Sediments are losing TCE into water column:
As the depth to sedmintation increases, water content will be decreases. ( Particles will be more at the bottom the at interface due to gravity settling). Thus at sediment depth 0 - water will be more than at sediment depth 2.
As per graph, TCE concentration is increasing with depth.
Thus sediment are losing TCE to water.
Answer: d) All of the above.
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