Hydrochemistry Of Surface Seawater Of Laizhou Bay

Laizhou Bay is a semi-closed bay with plenty inputs of river and nutrients oncontinental shelf of China. It is an important fishery and a key spawning ground andfeeding ground for fish, shrimp, and crab in China. With the rapid development ofeconomy and society of Laizhou Bay area in the new century, waste water inputs intothe bay from industry and agriculture are quickly increasing, leading to unprecedentedchallenges to marine ecology environments.According to our investigating results in Laizhou Bay in August2012, thehorizontal distributions of nutrients, the hydrochemistry was analyzed in this paper.The eutrophication assessment, risk assessment of heavy metal pollutions to seawaterwas analyzed. Attempts were made to find out the source of nutrients and heavymetals of Laizhou Bay with the data of coastal groundwater and river water. Thefollowing main conclusions are drawn:Freshwater inputs were the main factors affect the distribution of seawaterchemical element. Conventional chemical/physical parameters such as pH, salinity,specific gravity, TDS, electric conductivity and concentrations of K, Mg, Na, Ca, Sr,Cl, S, Li in Laizhou Bay surface seawater had distributions similar to each other in thesense that their concentrations were lower near the coastline than in the inner part ofthe bay. The mixing of salt water and freshwater might be the main factor of chemicaldistributions.Seawater temperature variation with the depth is significant. The shallower theseawater depth is, the higher the temperature. DO (Dissolved Oxygen) andtemperature showed a significant negative correlation, distribution was almostopposite. The change of physical and chemical factor in the vertical at bay mouth wasirregularly.Seawater of Laizhou Bay can be divided into eastern and western parts based onthe cluster analysis rsults. The eastern part was mainly affected by salt water from theBohai Sea, and the western part, by coastal freshwater discharge.According to the eutrophication assessment, seawater was potential phosphorus limit nutrient level.The N/P atomic ratio was189.06and remains high in recent years.The ratio was much larger than Redfield Ratio. With the consumption of nitrogen andpoor in phosphorus, the N/P values may continue to increase.In Laizhou Bay, there exists the risk of heavy metal pollution, ranked in the orderof Cu> Ni> Co. Owing to the limitation of observation data, we failed to figure out,we can not determine the reason of heavy metals in some parts of Laizhou Bay werehigher than other area. The way of heavy metals into the sea requires furtherinvestigation.Freshwater inputs in estuarine was the main source of nutrients in Laizhou Bay,and the preliminary analysis showed that submarine groundwater discharge (SGD)was the main path of land-sourced nutrients inputs into the bay. The rough estimationsare: transport fluxes by SGD were1.26×105t/a for DIN and2.75×103t/a for P. Thetransmission capacity of SGD can not be ignored.