A preliminary geochemical study of two cores from Massaciuccoli Eutrophic Lake, Northern Tuscany, and Paleoclimatic implications

Elevated organic carbon concentration in present sediments commonly derives from human and industrial activities and reflects the eutrophic status of a system. Furthermore, amount and type of organic matter may be used to reconstruct marine, lacustrine and continental paleoenvironments and paleoclimates because they depend on production and preservation rates, direct consequences of environmental changes. In September 2003 five 50 cm long cores were sampled in Massaciuccoli Lake, northwestern Tuscany, and two of them were chosen to investigate the impact of organic pollution sources on the system. Total content of organic carbon (TOC) and nitrogen (TN) were examined to study the eutrophic status of the lake, while TOC/TN ratio was used to distinguish between terrestrial and aquatic origin of organic matter. Results evidenced the presence of high organic matter concentrations in sediments and, in particular, its terrestrial origin, thus confirming inputs from land reclamation to water and sediment. According to such results, it appears that immission of nutrients, with consequent algal blooms, have a smaller impact than immission of land-derived organic matter in sediments. Moreover, one core probably recorded a climatic cycle, three times reiterated in the stratigraphic sequence.