A Study On Water Environment And Water Pollution Of Chang’an In The Tang Dynasty

Many factors should be taken into account in the location of the capital,and the water environment factors undoubtedly occupy a very heavy part.The water resources landscape of Chang’an in Tang Dynasty presented by archaeological materials has distinct characteristics of the times.In the design of water diversion,both coverage and grade system are taken into account,while in the design of drainage,rainwater treatment is the main method.Chang’an in the Han Dynasty considered salt brine when it moved its capital,while Chang’an in the Tang Dynasty repeated the same mistake after only 300 years.Through the analysis of the drainage layout of Chang’an City in Tang Dynasty,this paper finds that there are some defects in the water conservancy design of Chang’an City in Tang Dynasty,and it has to rely on seepage wells to treat domestic sewage.It took about 800 years for Chang’an in the Han Dynasty to have salty brine in its water.The water quality change of Chang’an in the Tang Dynasty had a clue in the middle and late Tang Dynasty,but it was not recorded clearly until the Song Dynasty that the urban groundwater was bitter and could not be drunk.There were at least two possible causes for the appearance of "bitter water" in Chang’an in the Tang Dynasty.The first is that domestic sewage is discharged underground through seepage wells and oxidized into nitrate nitrogen under suitable conditions,which eventually leads to excessive nitrate nitrogen content in groundwater.The other is that the lack of perfect drainage facilities leads to the continuous rise of groundwater level and obstruction.The water environment in Tang Dynasty was influenced by natural and human factors.Natural factors refer to bureaucratic disasters caused by heavy rains or prolonged rains,which aggravate soil salinization.Humanistic factors include the increase of sewage treatment pressure caused by urban population growth and structural changes.This kind of urban water environment change will naturally bring new problems.Excessive water accumulation may lead to the damage of canals or barriers,while the pressure of sewage treatment brought by the development of cities leads to the simple excavation of seepage pits due to leakage,and the pollution of sewage.In addition,the damage of urban water facilities will also deteriorate the water environment of Chang’an in Tang Dynasty,but its impact should not be overestimated.At the end of Tang Dynasty,water pollution or water quality was not taken into account.Considering the above factors,this paper finds that the water pollution in Tang Dynasty may not be serious.Therefore,in the last part of this paper,we turn to reflect on the previous research on water pollution.After careful analysis,this paper finds that the materials used to demonstrate water pollution in Tang Dynasty were misinterpreted to varying degrees.The first type is to extract materials from specific historical situations,and then to disassemble them word by word;the second type is to draw holistic conclusions from a few materials,trying to discuss the water quality changes of Chang’an in the Tang Dynasty with sporadic water quality change materials;the third type is to draw conclusions in the context of preconceived.In fact,these arguments are inadequate.Therefore,in the last part of this paper,the author further combs the achievements of the circle,analyses the basis of its derivation,and tries to find out the real reason why the water quality of Chang’an in Tang Dynasty was salty and bitter.