  The presence of even small amount of surfactant at the particle-laden fluid
interface subjected to shear makes surface flow incompressible if the shear
rate is small enough [T. M. Fischer et al, J. Fluid Mech. 558, 451 (2006)]. In
the present paper the effective surface shear viscosity of a flat,
low-concentration, particle-laden incompressible interface separating two
immiscible fluids is calculated. The resulting value is found to be 7.6% larger
than the value obtained without account for surface incompressibility.
