Trace Metals in Surface sediments 

The samples were taken from five locations in the intertidal zone of Bohai Bay. In total 15 sediment samples were gathered, each 5-10 cm deep. Five samples were collected from the lower intertidal zone, middle intertidal zone and upper intertidal zone respectively and placed in acid-rinsed polyethylene zipper bags. Sequential extraction procedure was used as analytical method to leach metals out of the sediment samples. This was done while the samples were still wet by reason to reduce errors at analysis.

 

The concentration of Cd, Cr, Cu, Pb, Ni and Zn were obtained by the use of plasma-mass spectrometry whereas the concentration of Al was analysed by plasma-atomic emission spectrometry.

 

To determine the water percentages of the samples an equal volume of each sample were heated until they reached a constant weight. Subsequently the result where compared with the weight before heating. Shimadzu TOC-VCPH/SSM-5000A and Elementar vario MACRO cube CHNS analyser were used to receive the TOC (total organic carbon) in the sediment samples.

 

For every sample the percentages of sand, silt and clay were measured.
 

To distinguish the natural metal concentrations from the metal pollution caused by humans the normalization technique was utilised. There are different types of normalization methods. In this study the index of geoaccumulation (Igeo) and enrichment factor were used.