NEAR-INFRARED REFLECTANCE SPECTROSCOPY OF SEDIMENTS - A POTENTIAL METHOD TO INFER THE PAST PH OF LAKES

We show that there is a pH-related fraction of lake sediments that can be recorded by near-infrared (near-IR) reflectance spectroscopy. Relationships between near-IR spectra of surface sediment samples and measured lake-water pH values, and between near-IR spectra of sediment cores and historical pH values inferred by diatom analysis, are modeled by partial least squares regression. The standard errors of prediction of these models are comparable to those obtained by modeling of diatom and lake-water pH data. We believe that near-IR reflectance spectroscopy has the potential to become a fast and simple method for inferring lake-water pH from lake sediment cores and thus a complement to diatom analysis, which is the best but tune-consuming technique available to study lake acidification history.