Study On The Heavy Metal Migration Rule In The Mainstream Of Fenhe River

With its unique characteristics,river basin system bears the necessary water resources for industrial,agricultural and residential uses among basin area.Fenhe river basin is the principal region of Shanxi province with developed industry and agriculture and is densely populated.It yields 46% industry output value and 64% agricultural output value of whole province respectively.2.43 billion cubic meters water is taken from the Fenhe River every year to the regions along the river and this accounts for 46% of water resources of the whole province.Fenhe river also receives and conveys the industry wastewater and domestic sewage discharged in the basin.How will the long term year by year diurnal sewage discharge affect the water course,bottomland,bottom mud substrate,adjacent land and the groundwater? What will be the focus of the ecological repairing? What will be the solution to the sustainable utilization and development path of resources? These are problems urgently to be concerned and studied.This study is supported by Shanxi fund project The Study on Principal Water Course Pollutants Lateral Accumulation and Migration Rule.The study mainly investigated middle and downstream of Fenhe river stem flow to show the pollution degree,migration rule and distribution characteristics of water course,bottomland,bottom mud substrate,adjacent land and the groundwater.On the basis of systematic field sampling at typical cross sections,this paper mainly analyzed and studied the spatial distribution characteristics of pollutants,transport and migrant kinetic mechanism of solute,heavy metal migration processes,pollution prediction model include targeted remediation steps and the remote monitoring of heavy metal pollutants of Fenhe river.The conclusions provide a useful reference for the scientific and economical prevention and treatment measure of similar rivers according to their actual local conditions.Meanwhile,it is also a reference sample for the further research of the water body pollution and pollutants diffusion on the river basin scale.The conclusions of this paper mainly include:1.This paper selected three middle and downstream critical urban sections of Fenhe river as investigation sites,i.e.across section of Qingxu city,Linfen city and Yuncheng city as sampling points,and collected samples from surface water,riverbed soil(horizontal distance 120 m,vertical distance 5m)and ground water within 5-24 km of the surrounding area to survey the pollutants content,distribution characteristics and diffusion rule of major heavy metal such as lead,cadmium,chromium and mercury.2.The main soil compositions of all the sampling sections are sand and silt.The order of all the samples and bottom mud of origin sampling points for average clay particle content is Linfen> Qingxu>Yuncheng and for average soil density is Yuncheng > Qingxu> Linfen,for soil moisture content is Linfen> Qingxu>Yuncheng.Soil particle size distribution is the key impact factor to the soil density and moisture content in natural condition.3.Both the groundwater and soil of all the sampling cross sections are in eutrophication state.The mercury and cadmium heavily polluted the surface water.The pollution caused by chromium is lesser than that of the mercury and cadmium.The pollution caused by lead is the least.The pollution caused by mercury to the groundwater is very common and severe.The pollution caused by cadmium and chromium,lead is lesser.The cadmium content in the bottom mud and bottomland closes to or exceeds the limit of grade III of Environmental Quality Standard for Soil therefore heavily polluted the environment.The pollution caused by lead and mercury is lesser.Fortunately,the content of chromium is low and does not pose a threat of pollution.The pollution caused by heavy metals along the river bank tends to decrease as the vertical depth and the horizontal distance increase.The surface enrichment phenomenon of these heavy metals is not obvious.4.In general,the main factors affecting the migration of heavy metal pollutants in the soil are soil particle size distribution,soil density,water potential gradient,the density of water resource pollutants and water level.5.The study employed software to simulate the pollutants lateral diffusion model when river supply riverbed soil.Therefore the software is capable of predicting the lateral diffusion tendency of heavy metal pollutants in the riverbed soil when wastewater is discharged into the river.6.The study suggests the solution to the present cadmium pollution should focus on the controlling of pollution source.The key heavily polluted region should change from cultivation field to residence field.The study also puts forward a monitoring system utilizing soil pollutants sensor.Since the migration of heavy metal is complex,diverse and prolonged,the deviation during the sampling,transportation of samples and analysis is unavoidable.For this reason,the relatively precise and absolutely correct prediction model is impracticable.The huge amount and large range of real time data for the analysis to draw a conclusion are unavailable.Since the experimental scheme and the model establishment are all based on homogeneous soil,the influences of heterogeneous soil should be taken into consideration in practical situation and the advanced monitoring methods should also be adopted to measure the sampling field area soil pollution.