Distribution Features and Variation Tendency of Chemical Elements in the Southern Yellow Sea in Winter

The data obtained from the survey in the Southern Yellow Sea in January 12～February 4,2007 are analyzed to study the distribution features and variation tendency of the marine chemicals.As it is shown in the results,firstly in the most of the sea area,the distribution of chemical elements is homogene-ous from the surface to the bottom,and it results from the strong vertical-mixing in winter.At the same time,the coastal current in the Western Yellow Sea,the marginal waters of the Taiwan Warm Current,the cyclonic eddy in the northern East China Sea,and the Yellow Sea Warm Current respectively play an important role in the distribution of the marine chemicals.Secondly,in the bottom water of the area ran-ging in 122°30′～124°E,34°42′～36°42′N i.e.in the north and the middle of the surveyed area,where the warming and saline influx effects of the Yellow Sea Warm Current become stronger,and the vertical mixing is limited within the upper layer,the thermocline appears in the water closely above the bottom lay-er in which some characteristics of the Yellow Sea Cold Water Mass remains from the summer time and some features of the warm water are given by the Yellow Sea Warm Current intrusion.It is the thermo-cline layer existence and the cold water remaining from summer time that provide favourable hydrographic conditions and dynamic factors for the lower DO and pH values,and the nutrient-rich places.Then the bi-ochemical effects become the inherent reason for the phenomena describled above.In addition,the thermo-cline layer plays an unfavourable role in the vertical transport of biogenic elements.Therefore the biochem-ical characteristics in the bottom layer are obviously different from those in the upper layer.Thirdly,al-though the chemical elements have their vertical homogeneous distributions in the most parts of the south-ern Yellow Sea in winter,the stratification phenomena and frontal structures appear in the eastern seg-ments of the sections in the northern and middle parts of the surveyed area,where the vertical homogene-ous distribution are limited within the upper layer and the gradient distribution appears in the lower layer.This can be attributed to the stratification occurring in the water layer closely above the bottom layer and to the waring and saline influx effects given by the Yellow Sea Warm Current.