Biogeochemical Cycles - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 174

where
C

= concentration of total organic chemical [mg l −1 ]

B = concentration of DOC [kg B l −1 ]

M s = concentration of sediment in segment [kg s l −1 ]

Similarly, the sediment-sorbed ( f S ) and DOC-sorbed fractions ( f B ) are:

Cn
C

′ ⋅ n

nK B

f =

w

= (4.58)

∑

s

+⋅ + ⋅ K M

pB ps s

s

KB ⋅

CB
C

′ ⋅

pB

f =

B

= (4.59)

∑

B

nK B +⋅ + ⋅ K M

pB ps s

s

These fractions are determined in time and space throughout a simulation from
the partition coefficients, internally calculated porosities, simulated sediment con-
centrations, and specified DOC concentrations. Given the total concentration and
the five-phase fractions, the dissolved, sorbed, and biosorbed concentrations are
uniquely determined.

C w = C ⋅ f D (4.60)

C s = C ⋅ f s (4.61)

C B = C ⋅ f B (4.62)

These five concentrations have units of mg l −1 and can be expressed as concentrations
within each phase:

C w ′ = C w / n (4.63)

C ′ = C s / M s (4.64)

C B ′ = C B / B (4.65)

These concentrations have units of mg/l w , mg/kg s , and mg/kg B , respectively.

4.2.4.3 Computation of Partition Coefficients

If the octanol/water coefficient cannot be reliably measured or is not available in
databases, it can be estimated from solubility and molecular weight and structure
information 131 (see Equation 4.66). More detailed information about estimating these
coefficients is available within SPARC. 145

log S = -1.08 log K ow + 3.70 + log MW (4.66)