A novel theoretical approach to correct for pathlength amplification and variable sampling loading in measurements of particulate spectral absorptionby the quantitative filter technique

A simple theoretical model is described that takes into account the combine d effects of pathlength amplification and variable sample loading in measur ements of particulate spectral absorption by the quantitative filter pad te chnique. The model differs from previous methods to correct for pathlength amplification by explicitly considering variability ill absorptance of samp le material on the filter pad, A(fp), as a result of different degrees of p article loading on the tilter. Functional expressions were evaluated that d escribe the relationship between A(fp) and the product of a dimensionless p ath factor, rho, and pathlength amplification factor, beta. The path factor , rho, represented the product of the absorption coefficient of sample mate rial on the filter and the geometric pathlength of the sample. A simple fun ction was shown to adequately describe the relationship for varying filtrat ion volumes with a variety of sample types, including phytoplankton culture s and coastal waters. Patterns predicted by the model are compared with pre viously published formulae developed for correction of filter pad absorptio n measurements. The functional form given here simplifies the approach for determining pathlength amplification.