Study On The Influence Of Reed Decomposition Process On The Water Quality Of Dongting Lake Around Reed Growth

Reed is an iconic plant in the Dongting Lake District.In 2017,the area of the reed in the lake area reached 1.3 million mu,with an annual output of 920,000 tons.It was mainly used as a raw material for the paper industry in the economic market.A small part was made into handicrafts and bamboo shoots.industry.The reeds in the Dongting Lake area are widely distributed and have a large biomass.In 2018,the Hunan Provincial People’s Government issued the“Implementation Plan for Guiding Exit of Papermaking Enterprises in the Dongting Lake District”（Office of Hunan government[2018]36）,requesting that“the papermaking enterprises around Dongting Lake in 2018will be comprehensive.Withdrawing from pulp production capacity and fully withdrawing from paper production capacity in 2019",the reed downstream industry papermaking industry is facing an overall withdrawal,which makes it difficult to find alternative resource utilization in the lake area in the short term.A large number of reeds will remain in the lake area and cannot be cut and utilized.Based on the investigation of the distribution status of reeds in Dongting Lake area,this study used reeds as raw materials to explore the relationship between the enrichment and release of nitrogen,phosphorus and organic matter during the process of decomposition,and further study the reed plants when releasing nitrogen and phosphorus The transfer between reed-water-sediment has obtained the following research results.（1）According to remote sensing interpretation,the reeds in Dongting Lake area are about 876,700 mu,mainly distributed in Yiyang,Changde,and Yueyang.Among them,the reed distribution area in Yiyang City is the most extensive,accounting for50.40%,and the reed area in Changde City is the smallest,at 18.21%.（2）The distribution of TN content in various parts of reeds is:spike>leaf>root>stem,but the difference in TN between root and stem is small,and the TN content is between 5.76 mg/g and 11.07 mg/g.The distribution rule of TP content is:spike>leaf,root>stem,and TP content is between 1.14 mg/g～2.11 mg/g.When the above-ground part of reed is cut,it can remove 7712.99 tons of nitrogen and 1241.45 tons of phosphorus annually.（3）The impact of the decomposition process on water quality is mainly manifested in the early stage,and the greater the biomass density,the greater the impact on water quality,and the greater the biomass density,the longer the impact on water quality.Temperature has a positive correlation with the decomposition process,that is,as the temperature increases,TN,TP and COD will increase.（4）The three parts of reed leaf,stem and spike,the same rule exists in the concentration of NH₄⁺-N,TN,TP:spike>leaf>stem,and the concentration of the three indicators showed a rapid increase from day 0-10,the concentration reached The highest,then slowly declined and stabilized,（5）The dry matter reduction of reeds in different parts was different.By the end of the experiment（90 days）,the dry matter weight of leaves,stems and spikes had decreased by 36.4%,21.78%and 40.67%,respectively.It takes 412.8 days,1552.88days and 838.13 days to release 99%of N in leaves,stems and spikes,respectively,and301.96 days,568.58 days and 430.7 days for leaves,stems and spikes to release 99%P.