Study On Saline Soil Water And Salinity Transportation Of Layered Soil In The Yangtze River Estuary

It is serious of the impact of the seawater invasion and seawater encroachment to thesoil of the Yangtze River Estuary. The salinization of soil always is serious at this area.After Three Gorges Project and Eastern Route of South-to-North Water Transfer Projectand Deepwater Channel Regulation project are put into operation, the ecologicalenvironment in Yangtze Estuarine Area will be more complicated and difficult to Predict.Study on Soil Water-salt Movements in the Yangtze River Estuary has become researchhotspot facing agriculture production and the protection of water resources andenvironment.Based on the Soil Salinization Character of the Yangtze River Estuary Area, this papermonitor the behavior on Soil Nutrient Characteristics and water content in different depthwith soil column simulation experiment in lab under the infiltration and evaporationconditions. Besides, we have constructed salt transfer coefficient model, salt migrationmodel and water migration model by1stOpt Software.This study provides scientific basis for the prediction of soil water content andimprovement of Coastal Saline Soil in Yangtze River Estuary Area. The main conclusionswere as follows:(1)Under stable infiltration condition, the regularity of Soil Salt Transport in YangtzeRiver Estuary Area is as follows: the soil layers between0~40cm were desalting at theoutset; soil layers between40~130cm were desalting after accumulating to a peak; soillayers between130~220cm accumulate salt gradually. The maximum downrange of soilEC(electrical conductivity) lied at30cm after leaching120days, and the maximumaccumulated value2.47ms·cm-1which is the maximum value during the whole studyprocess lied at90cm after leaching61days.(2)Under the Evaporation Condition, the study on Soil Water-salt Movements suggeststhe following results. Firstly, at different soil layers, soil EC became enlarged over time,and there has been a remarkable increase between0to30cm and170to220cm soillayers.The former because the rapid evaporation, and the latter, ground saltwater recharge.Secondly, volumetric water content became reduction at different soil layers over time, andthere has been a remarkable decrease from0to90cm due to high evaporation rates.However, after30days evaporating, volumetric water content decreased only0.004~0.015at soil layers90~220cm. Thirdly, during the experiment of soil evaporation, infrared heat lamp raised the temperature of upper soil layer, and the topsoil tends to salt accumulationobviously by the subtraction of water by evaporation at the0~25cm soil layer. Additionally,as the groundwater is salty, high concentration saltwater would rise from ground to columnof190to220cm deep.(3) We have modeled soil EC and volumetric water content with Excel under theEvaporation Condition at different soil layers including10cm，30cm，50cm，70cm，90cm，110cm，130cm，150cm，170cm，190cm and210cm deep. Function modely ax b, whoserelated coefficient larger than0.95, can model the correlation between soil EC and time atdifferent soil layers, and Function model y a x b, whose related coefficient larger than0.96, can model the correlation between volumetric water content and time at different soillayers.Under steady infiltration condition, we have constructed Soil EC dynamical modeland Salt Migration model and under evaporation condition Soil Salinity dynamical modeland water dynamic model were also constructed by the optimization platform of FirstOptimization software. The related coefficient(R) of the four models varies between0.9624and0.9992, the determination coefficient between (DC)0.9226and0.9984, the meansquare error（RMSE）between0.1400~0.1759and the square sum of error（SSE）between0.0002and4.4245.The studies of this paper are vital to predict soil water and salt transference andprevent and control soil secondary salinization in the Yangtze River Estuary; In addition,conclusions obtained have certain referential value for regulation of Three Gorges Project，South-to-north Water Transfer Project and Deepwater Channel Project and lay the theoreticfoundation for more simple and suitable Water-Salt Transport Model.