The composition and distribution of particulate and dissolved n-Alkanes in the Changjiang Estuary in Summer

Dissolved and particulate n-alkanes were collected from the Changjiang Estuary in July 2001. Samples collected from surface and bottom layers were covered from Xuliujing to the coastal area with the chorinity in range of 0.028‰~16.2‰. By soxlet extraction and gas chromatographic analysis, concentrations of total n-alkanes varied from 0.19 g·L~ -1 to 4.1 g·L~ -1 in surface layer and 0.12 g·L~ -1 to 1.9 g·L~ -1 in bottom layer for dissolved phase, and from 0.19 g·L~ -1 to 3.6 g·L~ -1 in surface layer and 0.63 g·L~ -1 to 4.2 g·L~ -1 in bottom layer for particulate phase. The carbon numbers of n-alkanes for most samples were in the range from n-C_ 15 to n-C_ 36 . The profiles of n-alkanes were three types including a bimodal distribution, a high carbon number predominance and a low carbon number predominance. The predominant source for organic matter in the Changjiang Estuary was terrestrial input indicated by CPI values and S/L ratios. The farther away from the river, the less terrestrial organic matter is observed in the estuary. The partition coefficients K_ d varied among different compounds and stations, and it seems that K_ d can be influenced by the concentration of particles. The distribution of particulate n-alkanes in the Changjiang Estuary might be mainly controlled by hydrodynamic processes and resuspension in the turbidity maximum zone.