Feasibility of using near-infrared reflectance spectroscopy for the analysis of C, N, P, and diatoms in lake sediments

The present study explored whether rapid, non-destructive near-infrared ref lectance spectroscopy (NIRS) could complement conventional paleolimnologica l and chemical analyses of sediment cores for greater efficiency and cost-e ffectiveness. The study used a 47-cm long freeze-core from the deepest poin t in Lake Arendsee, Mecklenburg Plain in northern Germany taken in 1993 to elucidate eutrophication history and to identify the pre-impact algal commu nities in this system. The core had been analyzed for total C, CO32-, N, P, and diatoms. Thirty-four of the 47 1-cm thick core sections were scanned b y NIRS and calibrations were developed for total C, CO32-, N, P, N:P, total diatoms, and three dominant diatom species with different sedimentary prof iles (Stephanodiscus binatus, Cyclotella rossii, and Fragilaria crotonensis ). Total C ranged from 167-194 mg g(-1) dry weight (d.w.), CO32- from 31.3- 66.4 mg g(-1) d. w., N from 9.9-17.4 mg g(-1) d. w., and P from 0.7-6.0 mg g(-1) d. w. Calibrations developed using multiple linear regression between NIR-predicted values and chemically-measured values were excellent for P ( r(2) > 0.99), good for C, N, and N:P (r(2) > 0.93), and satisfactory for CO 32-(r(2) > 0.8). Calibrations for total diatoms and for individual species were highly statistically significant (r(2) between 0.54 and 0.69). Althoug h the calibrations are not useful for reliable predictions of the content o f diatoms in the samples, the results indicate that NIRS detects spectral p roperties associated with diatoms or lake conditions when they were present , and that further work is warranted to attempt to improve the results. The study demonstrated that rapid, non-destructive, simultaneous analysis of t otal C, CO(3)2(-,) N, P, and N:P in sediment cores is feasible.