n-Alkanes in surficial sediments of Visakhapatnam harbour, east coast of India

Surface sediments collected from 19 stations along Visakhapatnam harbour were analysed for organic carbon (OC), δ 13 Coc, total lipids (TL), total hydrocarbon (THC), n-alkane concentration and composition. OC, δ 13 Coc, TL and THC ranged from 0.6% to 7.6%, −29.3 to −23.8, 300 to 14,948 μ gg −1 dw, and 0.2 to 2,277 μ gg −1 dw, respectively. Predominance of even carbon numbers n-alkanes C12–C21 with carbon preference index (CPI) of <1 suggests major microbial influence. Fair abundance of odd carbon number n-alkanes in the range of C15–C22 and C23–C33 indicates some input from phytoplankton and terrestrial sources, respectively. Petrogenic input was evident from the presence of hopanes and steranes. The data suggest that organic matter (OM) sources varied spatially and were mostly derived from mixed source.