珠江口内伶仃洋海域近百年来沉积物粒度变化和重金属分布特征

GRAIN SIZE VARIATION AND HEAVY METALS DISTRIBUTION DURING LAST HUNDRED YEARS UNDER THE IMPACT OF HUMAN ACTIVITIES IN THE INNER LINGDINGYANG BAY OF THE PEARL RIVER ESTUARY

对珠江口内伶仃洋不同海域3个柱状样沉积物进行的210 Pb测年和重金属分布特征垂向变化分析;研究了近百年来珠江口沉积速率时空变化;探讨了在自然作用和人类活动影响下重金属分布特点和累积因素。结果表明,珠江口内伶仃洋海域东西两岸的沉积物平均粒径4~7.5Φ,横门和深圳海域沉积物敏感组分呈现出显著双峰分布,粗细组分分界线为5.25Φ,淇澳岛沉积物敏感组分不明显,沉积环境较为稳定。基于210Pb测年的CIC模式,获得了各个岩心的现代沉积速率,横门海域沉积速率1.6cm/a,淇澳岛海域沉积速率4.08cm/a,0~70cm深度内深圳西海岸海域沉积速率2.58cm/a,70cm以深沉积速率为4.47cm/a。重金属含量分析表明,Cr、Ni、Cu、Zn和Pb含量从1923—1986年维持较高水平,但是变化不大;1967—1983年的深圳海域和1983—2004年的淇澳岛海域,各重金属元素含量快速上升;进入2000年以后,2003—2005年和2008—2012年,重金属含量呈现逐年减小趋势,2005—2008年则表现为逐年上升;这些变化与沿岸的社会经济发展、重金属入海量紧密相关。

3 sediment cores were collected in August 2012 at the Lingdingyang Bay of the Pearl River Estuary,the South China.On the basis of heavy metal analysis and 210 Pb dating,sedimentation rates over the past century are acquired.The distribution pattern and accumulation factors of heavy metals are discussed on the roles of natural and human activities.The results show that the mean grain size changes from 4Φ~7.5Φin the 3sediment cores.Obvious bimodal distribution is observed in the sensitive components in the Shenzhen and Hengmen sea areas,where the coarse component was divided from the fine at 5.25Φ,whereas the sensitive components around the Qi,ao Island is not obvious,suggesting a stable sedimentary environment.Modern sedimentation rates are calculated with 210 Pb dating data by CIC model.It was 1.6cm/a in the Hengmen sea area,but 4.08cm/a near the Qi,ao Island.Within 0 ~ 70 cm of the depth of the core,the sedimentation rate was 2.58cm/a in the Shenzhen sea area,and below the depth of 70 cm it was as high as 4.47cm/a.Heavy metal contents analysis shows that the contents of the Cr,Ni,Cu,Zn and Pb from 1923 to 1986remained on a high level with little change.A rapid increase occurred in the sea area of Shenzhen from 1967 to 1983and in the sea area of the Qi,ao Island from 1983 to 2004.From 2003 to2005 and from 2008 to 2012,the heavy metal content decreased year by year,except for the period from2005 to 2008while heavy metals increase.The changes in heavy metal content are closely related with socio-economic development there and the heavy metal flux into the sea area.