SOURCE AND BIOGEOCHEMICAL CHARACTERISTICS OF NITROGEN AND PHOSPHORUS IN JIAOZHOU BAY SEDIMENTS

Nitrogen and phosphorus in sediment play an important role in marine ecosystem,so many studies focused on it.The source and biogeochemical characteristics of nitrogen and phosphorus were discussed using the field data on content and vertical distribution of TN,TP,ON,OP,IN,IP,OC∶TN,TN∶TP in sediments obtained from the Jiaozhou Bay.The results obtained imply both the total nitrogen and the total phosphorus in surface layer of sediment decrease when moving from the inner bay to the outer bay.The concentration of total nitrogen in surface layer sediment was 0.41,0.25,0.20mg/g,and of total phosphorus is 0.29、0.24、0.22mg/g in inner bay,bay mouth and outer bay respectively.In general,organic nitrogen occupy 50%—70% of total nitrogen and inorganic phosphorus account for more than 60% of total phosphorus.The vertical distributions of N and P are more completed than horizontal distribution.The ratio of TOC∶TN can be used to deduce the source of organic matter in sediment.According to the ratios of TOC∶TN,organic matter from terrene account for 71.1% in station B3,86.9% in station D4,37.9% in station D7,respectively.So Nitrogen accumulated in sediment of the inner bay and the bay mouth mainly come from terrene by vertical distribution of N,P and OC∶TN,and the portion of autogenetic N is 28.9% and 13.1%,respectively.However,in the outer bay N is mainly of autogenetic constituting 62.1% of total nitrogen.In contrast to N,phosphorus mainly contributes from terrene;however the percentage of autogenetic P in the outer bay is remarkably higher than that in the inner bay.The date on suspended particle confirms that N and P in sediment of the inner bay are also mainly originated from terrene.The vertical variation of the OC∶TN ratio in sediment of the Jiaozhou Bay reflects the change of materials source over recent years.The sand input from rivers has decreased sharply,however the garbage input from Qingdao and surrounding regions has permanently increased.Thus,currently the garbage input substituting sand input,is the main source of sedimentation.The vertical distribution of TN,TP contents and TN∶TP ratio are in accordance with the increased trend of nutrient content in seawater of the Jiaozhou Bay.The sedimentation fluxes vary spatially.The sedimentation flux is the highest in the bay mouth and the lowest in the outer bay.In same region,the sedimentation flux is obvious difference between organic nitrogen,organic phosphorous and inorganic nitrogen,inorganic phosphorus in same region because of their different content.Nitrogen and phosphorus in inner bay release from sediment to sea water according to diagenetic rate,which indicate that N and P in sediment is an important source of N and P in sea water in inner Bay.However,N and P in sea water may transport to sediment in outer bay.Diagenetic rate of N is higher than that of P,whereas diagenetic rate of organic phosphorus is higher than that for inorganic phosphorus.However,the diagenitic rate of organic nitrogen was found to be not always higher than that of inorganic nitrogen,and the diagenitic rate of inorganic nitrogen was far higher than that of organic carbon sometimes,which indicated that inorganic nitrogen play a neglected role in the movement of nitrogen.OC,pH,Eh,Es can affect diagenetic rate;however their influence is different in various environment.