High Resolution Depositional Records Of Heavy Metals In The Mud Area Of The Coastal East China Sea And Their Response To The Human Activities

The coastal mud area of the East China Sea (ECS) is usually recognized as an important sink for heavy metals. The sedimentation rates in this mud area range in 1-5cm /a,therefore, this mud area is an ideal area to track the pollution history of heavy metals from the mainland China to the ECS in the past one hundred years.In this study, the depositional records of heavy metals of three cores in the coastal mud area of the ECS were reconstructed and their response to the human activities were revealed. The variations of grain size parameter depth profile in three cores are small, indicating that the hydrodynamic condition in study area is stable. The sedimentary rates of 24Z, 30Z and C0803 sediment core is calculated using 210Pb dating which are 3.38cm/a,0.98cm/a and 1cm/a, respectively, showing a rapid depositional rate in the area. The value of correlation between mean diameter and content of elements of 24Z core is high, indicating content of elements of sediments is primarily influenced by nature, but the remaining two is low , indicating content of elements of sediments aren't influenced by nature.Applying Al as the reference element, the enrichment factors (EF) of heavy metals in three sediment cores are calculated and the EFs of heavy metals are in good agreement with the rapid growth of economy of our country, especially having quite a good response to the china's economic recession. Applying change tendency of enrichment factoes(EF) of heavy metals as an index, combined with the relative literature, the high resolution of sediment records of heavy metals in mud areas of coastal East China Sea can be divided into three response stages in recent one hundred years.The first stage: Before the foundation of P.R.C (1900 ~ 1949).In the stage, enrichment factors of Pb, As, Zn in some periods increase rapidly, but the overall enrichment factors in the stage is low. It has a good response to our low level of our country's industrial development in the stage. The second stage: from the foundation of P.R.C to the beginning of reform and opening up (1949 ~ 1983). During this stage enrichment factors of Pb, Zn, As increase rapidly at first, which is in good agreement with the rapid development of our country's economy in the initial of building country. After a series of political struggle such as anti-Rightis and the Great Proletarian Cultural Revolution and so on, with political native impact, the economic growth rate slows down even the economy is in depression, which have a signal impact on sedimentary records of heavy metal.The third stage is:the era of reform and opening-up (1983 ~ 2009), enrichment factors of Pb, Zn, As are significantly higher than the other two stages, which indicating China's industrial economy in this stage is in the rapid development condition. After 1999, enrichment factor of these elements decreased, but the enrichment factor value is still significantly higher than it of the foundation of P.R.C.