| The present study investigated spatial distribution characteristics of sediment and the response to the depositional environment in the Xiamen sea. Particle size analysis of surface sediments were used to establishthe relationship between the spatial distribution characteristics and depositional environment.Thus, a variety of analyses wereused to obtain the type of sediment distribution pattern, net sediment transport trends and thesources.We also collectedthe coresamples to obtain thesediment grain size, sensitive components and deposition rate,according to the sediment dynamics and210Pb dating. Further, the interaction of the material sources and marine sedimentary environments are explored by the observation of tidal-cycle hydrodynamic process atthe study area.The previous and presentstudy suggestthatthe sediments of the study area are consist of various types, mainly silty sand and sandy silt. The sediment at Jiulong River Estuary isconsist of coarse particles,and that is medium grain size at the southernXiang’an and the eastern Xiamen Island area. The sediment around the Kinmen Island is muchcomplex. The coarse (<0.65φ) andwellsortedsediment (<2) is mainly observedin the Jiulong River Estuary.The Gao-Collins grain size model was applied to estimate the net sediment transport pathways in the study area. It suggests that the sediment transport southeastward in the Jiulong River Estuary, and towards this estuary from Dajinmen area. Marine sediments of Xiamen Bay transport from the ocean currents from the Taiwan Strait in the southwest of Xiamen. In addition, the sediment transport offshore to the central bay in Tonganwan area. The sediments transport towards north in the eastern Xiamen sea, and towards the mouth of Tonganwan and onshore of Aotou.The tidal-cycle hydrodynamicsmeasured atJiulong River Estuary show thatthe study area is regular semidiumaltide and reciprocating flow. The ebb is dominant during a tidal cycle.The water depth varied from5.87cm toll.52cm,temperature range is16℃-17.95℃,salinity varied from21to28,suspended sediment concentration increased with increasing velocity.Sensitive component of the sediment particle size is derived from the core samples collected at the Jiulong River Estuary. It shows that standard deviation curve of the grain size fraction has a bimodal distribution pattern. It represents two environmentally sensitive components,with the ranges5.0～10.2μm and136.8～193.4μm, and the peaks7.18μm and162.67μm, respectively. The former is clayey silt, representative suspended quality components, the sources may include the input of the basin to sand and offshore,while the latter is silty sand, on behalf of the bedload component, mainly from the upper basin.The sediment core was analyzed by using210Pb dating method, and showed that the deposition rate was2.62cm/a in the Jiulong River Estuary. Thereis an increasing trend in deposition rate in recent. In addition,the deposition rate atthe Jiulong River Estuaryas a whole is higher than that at Tongan Bay,while theXiamen is higher than the Jiulong River Estuary. The sedimentin the study area comesmainlyfrom the Jiulong River watershed, and also from the Taiwan Strait,which is consistent with the net sediment transport trends.Additionally,Tidal, wave and storm surge leada complex distribution pattern of sediments in the study area, and thus induceimpacts on the depositional environment. |
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