Environment Monitoring of Offshore Sand Mining in Pearl River Estuary

Based on the analysis of the monitoring data of an offshore sand mining area in the Pear River estuary, the submarine geomorphy of the mining area can be classified into four types, namely shore, coarse sand mining pit, smooth sand mining pit and semi-deep terrain. From the sub-bottom profiles, it can be found that the four types represent four stage processes of sand mining, of which the most direct impact is the change of water depth, geomorphy and shallow sediment. Coarse granule sediments of autochthonous deposit cause strong reflection in the seabed surface and reduce the penetrating power of seismic wave. However, fine particles like clay and silt become suspended solids and gradually deposit, forming a smooth sediment surface of weak reflection and an illuvial horizon that can be penetrated by the seismic wave of shallow stratum section plotter, after being away from the sand mining center in a certain distance. Carry out research on four stratigraphic profiles representing the sand mining process that are selected from the testing zone and conduct analysis description on the sedimentation process of the sand mining area. By comparing topographic monitoring data of March in 2009 and that of September in 2010, the annually variation diagram of sedimentation can be acquired. There is more sedimentation in low-lying places. The thickest sedimentation is 3m. Yet the annually sedimentary thickness is less than 1m in the broad semi-deep water area that is more that 0.5 km away from the depocenter. This data show the local typical sedimentation rate.