Sediment Dispersal Processes On The Southern Yellow Sea Continental Shelf:Tracer Methods

Tracer methods represent an efficient way for tracing material from source to sink,which can quantify the transport patterns and processes within the system consisting of the river,the coast and the continental shelf.It is important in the field of marine sediment dynamics for material source identification and sediment transport rate calculations.In the present study,the tracer methods,including sediment provenance tracing and sediment transport tracing modelling,are integrated a unified method or technique.The radial sand ridges on the inner continental shelf of the southern Yellow Sea,with complex dynamic processes and multiple sediment provenances,was selected as the study area.The distribution characteristics of grain size,heavy minerals,and geochemical elements in the different grain size sediments and clay minerals in the different sediments from the modern Yellow River,Yangtze River and abandoned Yellow River are analyzed,to display the spatial and temporal variations in the different tracer fingerprints from the three invironments.Differentiation analysis is carried out to determine the best tracer fingerprints for the three terrestrial sediments;on suh a basis,the sediment sources on the inner continental shelf are quantified by using the mixing model.Furthermore,the sediment transport rate is calculated by using the governing equation of the tracers.Specifically,the major results from the study are summarized as follows.(1)Analytical procedures are established for selecting the best tracer fingerprints of the coarse and fine sediments,respectively.Nonparametric significance test methods,i.e.,the Mann-Whitney U and Kolmogorov-Smirnov methods for two independent sets of samples,are applied,in combination with the spatial and temporal variations of the different tracer fingerprints from the abandoned Yellow River,modern Yellow River and Yangtze River,to indicate that the best tracers are garnet and zircon for the heavy minerals,Ni,P,Zn and Co for the muddy sediments,and Ba,K,Ti,P,Mn,Fe,Ni,Co for the sandy sediments.(2)Based on the identification of best tracer fingerprints and the mixing model,quantitative analysis has been carried out to trace the sediment sources on the inner continental shelf of the southern Yellow sea,which shows that the muddy sediment is mainly from the abandoned Yellow River delta,including both Yellow River and non-Yellow River materials.The sandy sediment is mainly the materials from the abandoned Yellow River and the Yangtze River.These results imply that the sediment sources are quite different for the different grain size sediments on the inner continental shelf of the southern Yellow Sea.(3)The universally valid tracer system for net sediment transport is solved for the first time,to define the sediment transport rate over a large area.The sediment transport patterns obtained for the study area showed that the transport rates for the muddy and sandy sediments varied from 10-1 kg/m/s to 100 kg/m/s,and the transport directions are quite different in the muddy and sandy areas.(4)The assumption made for the modeling is that the sedimentary amterials within the transport system are supplied by the abandoned Yellow River and the Yangtze River.However,if the sediment sources are changed,then the sediment transport patterns will vary,even if the tidal current dynamic conditions remain the same.Hence,the modeling can be further improved by taking into account the other possible sediment sources,e.g.,the reworking of pre-Holocene strata and the newly generated sediments in the marine evironement.