The following curves show measured effluent concentrations of solutes a, b, and

Question

The following curves show measured effluent concentrations of solutes a, b, and c (all pesticides) as they flowed through a 20-cm-long column packed with soil with porosity of 0.3, soil bulk density of 1.5 g/mL, and organic carbon fraction of 0.15. a. What can you say about the relative magnitudes of the partition coefficients (Kg) of each of the three solutes? (i.e. order them from greatest to least) b. If solute a has a retardation factor (Rd) of 1, calculate the retardation factor (dimensionless) and the partition coefficient (mL/g) of solute b. c. If solute c has a solubility of 1480 mg/L, calculate and R_d. log(K_oc) = -0.55 log 5 + 3.64 (valid for pesticides, where S is in mg/L and Koc is in mL/g)

Explanation / Answer

Solution:

# (a)

The partition coefficient of the three solutes a,b and c are in same phase only time varies,

Kd = C/Co where a = b = c = 0.5 shows that all three solutes are having unique property.

# (b)

If R = 1 then k an retention factor k = (1 - R) / R = 0 will yield uniform partition coefficient for all three solutes.

k = (3.5-2) / 2 = 0.75

# (c)

S = 1480 and by plugging in given equation we get log Koc = 1.89

gives Koc = 78.769 mL/g

Rd = 1.5 / 78 = 0.019

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