Research On Heavy Metal Water Quality Model Of Changzhutan Section Of The Xiangjiang River Based On WASP

In recent years,although the water quality of the Xiangjiang River has improved,due to the fact that it has accumulated a lot of historical debts,it is too hard to recover to the normal level.So the Xiangjiang River heavy metal pollution situation is still grim,coupled with the problem that the heavy metal pollution is concealed and persistent.At present,the Xiangjiang River has not yet established a response relationship between heavy metal pollutants and river water quality,it can not carry out effective supervision and management of heavy metal emissions,so it is difficult to achieve effective protection of the Xiangjiang River.Therefore,in this study,we select the TOXI module of WASP model,and choose Changzhutan section as the research area,in which heavy metal pollution is relatively concentrated in the Xiangjiang River.The cadmium,arsenic and lead with strong emissions are used as the research indicators.Under these circumstances,the heavy metals water quality model for the Xiangjiang River Changzhutan section is constructed,meanwhile the water environment capacity of cadmium,arsenic and lead in the Xiangjiang River Changzhutan section is calculated,in order to provide technical support for the Xiangjiang River heavy metal pollution prevention and water environment management.The main research results are as follows:?1?At first,the Xiangjiang River Changzhutan section is divided into 12segments,and the collection,processing and input of the model information are completed.Next,according to the rule of the migration and transformation of heavy metals in water,the sedimentation rate K_W,the resuspension rate K,the partition coefficient to dissolved organic carbon K₁?except for arsenic?,the partition coefficient to silts and fines K₂,the partition coefficient to organic solids K₃ and the partition coefficient to sands K₄ are choosen as simulation oparameters of the cadmium,arsenic and arsenic,then the heavy metal water quality model of the Xiangjiang River Changzhutan section is initially established.?2?The parameter local sensitivity analysis and the sensitivity analysis based on orthogonal design are basically the same.At the same time,the key parameters of the simulated output concentration of cadmium,arsenic and lead are sedimentation rate K_W and the partition coefficient to sands K₄.Based on the orthogonal design results,theoretical optimal parametersl combination of cadmium,arsenic and lead is determined.On this basis,we choose the method of model trial and error,and use monitoring data to get corresponding parameters of cadmium,arsenic and lead.The sedimentation rate K_W of cadmium,arsenic and lead are 3.18 m/d,2.89 m/d,2.97 m/d,respectively.The the partition coefficient to sands K₄ of cadmium,arsenic and lead are 4.48×10⁴ L/kg,7.89×10³ L/kg,9.51×10⁴ L/kg,respectively.?3?Two sets of data and two methods are used to test the model.The results of Cort consistency analysis showed that the consistency index?d?of cadmium,arsenic and lead are 97.88%,99.10%and 98.69%,respectively.The relative error analysis showed that the average relative error of measured values and simulated values of cadmium,arsenic and lead are 6.03%,6.50%and 7.52%,respectively.On the whole,the combination of parameters is reasonable,and the heavy metal water quality model can be used to simulate the heavy metal water quality of the Xiangjiang River Changzhutan section.?4?The heavy metal water quality model is applied to calculate the water environment capacity of cadmium,arsenic and lead in Changzhutan section of the Xiangjiang River under three different hydrological conditions,including dry season,plain water period and high water period.The water environmental capacity of cadmium are 9.50 t/a,17.04 t/a,35.40 t/a,respectively.The water environmental capacity of arsenic are 51.78 t/a,110.24 t/a,127.16 t/a,respectively.The water environmental capacity of lead are 72.00 t/a,119.86 t/a,302.70 t/a,respectively.