Potential Ecological Risk Asssessment Of Heavy Metals In The Surface Sediment Of Bohai Bay Caused By Ore Stacking Yard Of Tianjin Port

At present, the ore stacked in Tianjin Port is mainly deposited in the open air, theleaching of rain will cause the dissolution of heavy metals in the ore. Static soakingand dynamic leaching experiments showed that the dissolution amount of someelements exceeded the standard. In this study, microcosm and mathematical modelwere builded in order to analysis and simulate the aquatic environment, to explore themigration behavior of heavy metals in aquatic environment, to get the inherent law.Simultane ously, the work, detecting the total content and fraction of heavy metalsand physicochemical indexes in the surface sediment of Bohai Bay, was carried out inorder to know the impact of ore stacking yard of Tianjin Port on Bohai Bay, toprovide data and theory to prevent Bohai Bay from being polluted by heavy metal.A series of results and viewpoints were presented:(1) In aquatic microcosm, the concentration of lead and cadmium in the waterphase firstly increased and then decreased, and the content of lead declined faster thancadmium. The concentration of cadmium in the sediments increased slowly within120h, and then fell slightly. The concentration of lead in the sediments increasedrapidly within24h, and then fluctuated slightly. The increase of total content ofcadmium was mainly caused by the increase of exchangeable form amd fractionsbound to carbonates and Fe/Mn-oxides in the sediments. The increase of total contentof lead was mainly caused by the increase of fractions bound to carbonates,Fe/Mn-oxides and organic matter.(2) That the simulated results matched the data obtained by the experiment wellshowed that this model was rational. By comparing the values of D, the migrationparameter, it was found that about61%of total content of cadmium was retained inthe sediments, and the remaining was taken away by advection, however about99%of lead was retained in the sediments, which showed that settlement is the mainprocess of migration of cadmium and lead, especially the lead.(3) In the surface sediment of Bohai Bay, the content of heavy metals increasedcontinually from sorth to nouth, and reduced with constantly away from the coast.Among heavy metals, lead was polluted heaviest, while other heavy metals (iron,chromium, nickel, copper, and zinc) were clean or lightly polluted. According to the comprehensive analysis of the characteristics of the distribution of heavy metal inBohai Bay, the position of ore stacking yard of Tianjin Port and the types of ore, orestacking yard of Tianjin Port may be the main reason led the content of heavy metalsin the surface sediment of Bohai Bay, such as iron, chromium and nickel, to reach themaximum.