夏季长江口中颗粒态及溶解态正构烷烃组成和迁移

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

为阐释长江口颗粒态、溶解态正构烷烃的时空分布特征,并初步探讨其迁移循环机制.2001年7月在长江口分表、底层采集溶解态与颗粒态样品,采样区域的氯度跨度为0.028‰～16‰.样品经有机抽提和气相色谱定量分析,检测到表层溶解态、颗粒态正构烷烃总浓度分别为0.19～4.1μg·L^-1和0.19～3.6μg·L^-1;底层溶解态、颗粒态正构烷烃浓度分别为0.12～1.9μg·L^-1和0.63～4.2μg·L^-1.结果显示,长江口水体中正构烷烃碳数多分布在n-C15～n-C36间,正构烷烃碳数浓度分布呈高碳数优势、双峰型优势和低碳数优势3种关系.特征参数表明,长江口有机物呈显著的陆源有机质输入特征;且由长江口向外,陆源输入逐渐减弱.固-液分配系数Kd在不同站位和不同化合物间差异较大;同时Kd还存在颗粒物浓度效应.河口区颗粒态正构烷烃迁移的控制因素主要有潮周期的变化和沉积物再悬浮等.

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 soxht 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-C15 to n-C36. 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 CP1 values and S/L ratios. The farther away from the river, the less terrestrial organic matter is observed in the estuary. The partition coefficients Kd varied among different compounds and stations, and it seems that Kd can be influenced by the concentration of particles. The distribution of particulate nalkanes in the Changjiang Estuary might be mainly controlled by hydrodynamic processes and resuspension in the turbidity maximum zone.