Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Relations between microelement composition of bed load sediments and sedimentation in delta of the Mekong river (Vietnam)
Abstract
Relevance. The research of formation mechanisms of natural and natural-anthropogenous geochemical anomalies in water objects plays the extremely important role in geology and geoecology is the required stage in developing long-term forecasts of ecosystems state and planning nature protection actions. One of the key aspects of the problem - the revealing of the relations between geochemical and hydrological processes in a delta of the big river - is considered by the example of the largest river of Indochina - the Mekong river. The choice of the object is caused by the value of the river in social and economic development of southeast Asia. The aim of the research is to reveal the relations between the formation of bed load sediments in the delta of the Mekong river (Vietnam) and their microelement composition. Methods of the research: landscape-geochemical and geography-hydrological methods, mathematical modelling of hydrological processes. Results and conclusions. The authors have obtained the data on microelement composition of the bed load sediments in the delta of the Mekong river and have estimated the deformations of the river channel (the Hamluong channel) using the method of A.V. Karaushev by the surveying works in 1999 and 2000 in cross-sections, located in 72, 49, 14, 1 km from sea edge of delta. It was ascertained that accumulation of sediments prevails on a site of the Hamluong channel of 0-31 km from sea edge of the delta. Based on the data of the geochemical approbation which has been carried out by Phung Thai Duong in 2013-2014 it is shown, that within this site 1244 tons of Zn; 443 tons of Cu; 63 tons of Pb; 18 tons of Cd; 96 tons of As; 1,7 tons of Hg annually settle. In the delta of the Mekong river the basic part of weights of Zn, Cu, Pb, Cd, As 73 wt. % and Hg 69 wt. % are formed due to sedimentation of particles with the specified microelements (in the suspended form). As 27 wt. % and Hg 31 wt. % are related with sorbtion on besieged particles and removing poorly soluble substances from a solution. The authors made a conclusion that the application of the bed load sediments withdrawn in the delta of the Mekong river on a site from 31 up to 15 km is optimal for agricultural use. It is appropriate to use the river sediments on a site of 0-15 km with the highest concentrations of toxic microelements for building needs at engineering protection of coastal territories.
