If you can convert the particle size distribution to a particle radius distribution, p(r), then the total surface area is just the integral (between the limits r=0 and r=infinity) of this multiplied by the surface area of a sphere. i.e. A = 4*pi* integral[ p(r)*r^2 dr ]. This adds up all possible surface areas for any sized spheres, weighted by the radius distribution function as it should be.
If you can convert the particle size distribution to a particle radius distribution, p(r), then the total surface area is just the integral (between the limits r=0 and r=infinity) of this multiplied by the surface area of a sphere. i.e. A = 4*pi* integral[ p(r)*r^2 dr ]. This adds up all possible surface areas for any sized spheres, weighted by the radius distribution function as it should be.