Rapid determination of chemical and physical properties in marine sediments using a near-infrared reflectance spectroscopic technique

Marine sediments preserve useful information for reconstructing oceanographic conditions and environmental changes in the past. In this study, the authors have evaluated an efficient near-infrared reflectance spectroscopy (NIRS) method for simultaneous determination of total C (TC), total inorganic C (TIC), total organic C (TOC), magnetic susceptibility (MS), the ratio of di- and tri-unsaturated C37 alkenones (U37k′), and δ18O of foraminiferal shells in marine sediments. Near-infrared diffused reflectance spectra (1100-2500 nm) of 172 sediments recovered from the IMAGES Core MD972151, located in the southwestern South China Sea, were analyzed and correlated with the abovementioned parameters using partial least squares regression (PLSR) procedures. The leave-one-out cross-validation results showed that TC and TIC were successfully predicted (r2 > 0.93) while MS, U37k′, and δ18O were estimated with moderate accuracy (r2 > 0.76). The concentrations of TOC, however, could not be estimated with high precision (r2 = 0.34), which is possibly a result of the low and narrow range of organic C in this specific core. The results indicate that NIRS has the potential to be a rapid analytical tool for continuous marine core examination, although uncertainties associated with TOC need further investigation.