The Sedimentary Characteristics And Environment Record Of Yalu River Estuary

A large number of sediment sampling and measured data was got by the Marine geological and geophysical survey in Yalu River estuary. Through the lab analysis to grain size、detrital mineral heavy metals and biogenic elements in surface sediment and core sediment, and combining with the measurement of sedimentation rates in the core sediment of by210Pb,The paper researched horizontal and vertical variation characteristics of grain size、 detrital minerals、heavy metals and biogenic elements in the sediment, discussed the sedimentary characteristics、sources、transportation process, analyzed the status of environmental pollution、the source of pollution and the evolution processes of environmentThe research of this paper got the following achievements:Researched the distribution characteristics of grain size and detrital minerals in the surface sediment of different zone in Yalu River estuary, and discussed the sources and transport process of surface sediment in different regions.Researched the distribution of heavy metals and the relationship between heavy metals and grain size in different zones, and discussed the sources and sedimentary environment of heavy metals.Evaluated the pollution condition of heavy metals using different assessment methods, and discussed the pollution levels and main pollution factors of heavy metals.Researched the rain size、detrital minerals、heavy metals and biogenic elements in core sediment, and got the change process of sedimentary environment and evolutionary process of environmental pollution in Yalu River estuary in recent century.The research of the paper got the following results:The research results of grain size showed that the source of surface sediment in Yalu river estuary was not single, but had diversity and spatial distribution, and that its surface sediment types were mainly S, ST, TS and very few TS. The sediment transport by runoff of Yalu River is very apparent in the estuary area, and together with the sediment of the shallow sea’s movement to land caused by the tides and waves, so the sediment source of the estuary surface was diversity. The sediment source of the Yalu River downstream area and middle water way was mainly for the river transportation, and the river runoff effect was obvious; The sediment source of west waterway and Liaodong shallow beach were both estuary transportation and the sediment movement of the shallow sea surface to land under the double influence of the rivers runoff and the ocean tide and waves.The research results of detrital minerals showed that the sumptomatic mineral t in the Yalu River estuary areas included the heavy mineral including sphene, andalusite, grenatite, kyanite and the light mineral-vitreous ash, and the distribution characteristics of and characteristic index change of detrital mineral showed that the surface sediment of the Yalu River estuary and of the shallow sea surface had different material sources. The Yalu River downstream area and the East waterway deposition gave priority to river function, and that was river modern sedimentary,then West water channel and the Liaodong shallow beach were affected by the double influence of the rivers and shallow sea.The study results of the heavy metal showed that the heavy metal of the Yalu river estuary mainly came from the industrial and agricultural pollutant discharge, and there was a more consistent source and sedimentary environment among the heavy metal element, then the heavy metal pollution factor with higher ecological risk assessment contribution rate to the metal pollution of the Yalu river estuary was Cu, Cd and Hg.The study results of biogenic elements showed that its main source was the industrial and agricultural pollutant emissions, land development, domestic sewage, etc; Biogenic elements had a high correlation with heavy metal element except Cu, and biogenic elements and heavy metal elements had a consistent source and sedimentary environment.The core sediment’s research results showed that the environment evolution process of the Yalu river estuary area could be divided into three stages:the first stage was before Shui Feng water reservoir built in1941, and pollutant content rangeability was larger, then by reason of no reservoir interceptor, the runoff’s annual change of the Yalu river was very large; The second stage for Shui Feng Water Reservoir built by the early1980s, because of the reservoir’s interception effect, the annual runoff rangeability of the Yalu river was small, and pollutant content change was also relatively small; The third stage is from Later1980s to now, pollutant content appeared an obvious increasing trend because of large amounts of pollutant emission from agriculture, industry and urban construction.