围海造地工程对香港维多利亚港现代沉积作用的影响

对采自香港维多利亚港的 4个 6m长的沉积柱状样作了2 10 Pb及Pb、Zn、Cu含量分析。结果表明,维多利亚港开阔区域现代沉积速率在 0.3～ 2cm/a之间变化,西部大于东部。在九龙海峡主航道上,基本上处于冲淤平衡状态。由于近百年来围海造地、海岸工程建设,使维多利亚港的岸线发生了较大的变化,在台风避风塘等潮流作用较弱的区域及靠近城市排污口的地方沉积速率可达 3～ 5cm/a,这表明围海造地、海岸工程等造成的岸线变化是影响维多利亚港堆积侵蚀的主要因素。Pb、Zn、Cu等重金属在沉积柱状样中的分布表明,在沉积速率较快的区域,重金属的污染也较为严重。

Assessing the Impact of Reclamation Activities on Recent Sedimentation in Victoria Harbour, Hong Kong

The sediments that accumulate in an estuarine environment recorded the information about the history of changes in the source of the material, the rate of deposition and the influence of man. Man's influences on Victoria Harbour are significant. To create flat land and cope with the rapid development in Hong Kong, reclamation activities have taken place about every 10～20 years in Victoria Harbour began from a few decades ago. And to maintain the navigation channel, get fill material for reclamation, many dredging activities were carried out in the Harbour. These activities changed the coastline seaward and also complicated the recent sedimentation process in the Harbour. To study the extent and history of man's influence on the sediments and recent sedimentation process in the Harbour, four vibrocores were collected in three designated locations within Victoria Harbour, Hong Kong in 1996. Sampling locations were chosen from a range of settings where reclamation or construction is planned or taking place. Each of the cores was 76 mm in diameter and 6 m in length. The sediment type and colour were describe from visual and photographic observations and by matching Munsell(R) Soil Color Charts. The 210Pb activities for the sediments were determined by210　　Pb method and ICP-AES was employed for the determination of Zn, Cu, while FAAS for that of Pb concentrations. Sedimentation rates in Victoria Harbour have been determined to be about 0.3～2 cm/a in open areas based on　210Pb dating and heavy metal distributions. This value can represent the natural sedimentation rates in the Harbour. Since reclamation activities have changed the coastline and affect the sedimentation process in the Harbour, sediments have been contributed by effluent discharge, materials lost from dredging and reclamation work. In some nearby enclosed coastal port and dumping areas, the rates were found to be somewhat higher in these areas, in the range 3～5 cm/a. This result, that the sedimentation rates are high in some places in the Harbour, is also in keeping with the more serious heavy metal pollution in these places and reflects man's influence on the Harbour. This means that changes in the coastline caused by reclamation may have a significant effect on siltation in the Harbour.