SPATIAL DISTRIBUTION OF HEAVY METALS IN THE SURFACE SOIL OF YELLOW RIVER DELTA AND INFLUENCE FACTORS

This research focuses on the distribution pattern of heavy metals in the surface soil and sediment of the Yellow River Delta. 219 samples were collected, including 25 samples from the shallow coastal wetland in 2006-2008. Modern techniques have been used to detect the contents of heavy metals. The abundance of heavy metals appears in an order of Cr > Pb > Zn > As > Cu > Cd > Hg in the region. The accumulation ratio of heavy metals is low in shallow coast wetland. The Delta as a whole could be divided into three regions in accordance with the distribution pattern of heavy metals. It shows that the northern part of the delta is mainly effected by oil and gas exploration and production, the middle part of the delta affected by the River itself and the south part effected by agriculture and discharge of sewages. Even though the soil of the Delta is rich in organic matter, the heavy metal contamination remains on medium level or even lower in the upper deltaic plain, while pollution of heavy metals is higher in the shallow coast wetland.