Marine Bacteria Regulation Of Water-fertilizer-salt During Abandoned Salt Field Reclamation

In Shandong Province,96.9%of the salt fields are distributed in the coastal areas of the Yellow River Delta.In recent years,many salt fields have become abandoned.In the Yellow River Delta area,underground pipe drainage is mainly used for washing salt.However,nutrients such as nitrogen and phosphorus in the soil could leak out of the soil with the salt washing and drainage,which will cause the soil nutrient supply to become unbalanced and induce regional ecological problems.It is known that Water and salt movement are frequent during salt washing,and the salinity fluctuates greatly.Marine bacteria with nitrogen and phosphorus fixation ability that survive in extreme environment may be more suitable for soil nutrient fixation during underground pipe drainage.In order to inhibit soil salinization,improve soil fertility and give full play to the nitrogen and phosphorus fixing performance of marine bacteria and ensure the diversity of soil microbial communities,immobilization with straw can be applied to the waste salt field soil.In this study,the optimal bacteria strain and microbial immobilized carrier straw that can be used for abandoned salt field reclamation were screened via batch simulation leaching tests.The soil columns and simulated salt washing test were used for exploring the effects of immobilized marine bacteria on soil properties,salt washing drainage water quality,and microbial community during salt washing.The main works and conclusions of this research are as follows:(1)The optimal combination of immobilized marine bacteria was screened from four marine bacteria(Pseudoalteromonas sp.SCSE709-6(709-6),Vibrio.Sp Y1-5(Y1-5),Shewanella sp.CF8-6(CF8-6),Pseudoalteromonas sp.CF10-13(CF10-13))and three kinds of straw(corn straw,wheat straw,and corn cob)through batch simulated leaching test.The results showed that corn cob immobilization CF8-6 was optimal.CF8-6 increased the pH of the eluent,effectively reduced nitrogen loss by 53.33%,inhibited the NO2-N loss,and reduced phosphorus loss by 88.03%.Compared with the two immobilized treatments of corn straw and wheat straw,the corn cob immobilized CF8-6 had the largest amount of salt washing,the smallest amount of NH4-N and TP leaching,and decreased TN leaching by 53.92%.(2)The soil column test was used to explore the physicochemical properties of surface soils,different forms and transformation of nitrogen and phosphorus,and the enzyme activities under different treatments during the cultivation period.The results showed that corn cob immobilized marine bacteria increased soil available phosphorus by 37.03%,significantly increased the bio-available phosphorus content,improving soil fertility.The addition of corn cob in the treatment of immobilized marine bacteria not only increased the soil nitrogen content,but also facilitated the enrichment of nitrogen-fixing bacteria.The effect of corn cob on the soil bacterial community was greater than that of marine bacteria.Corn cob immobilized CF8-6 increased the abundance of Proteobacteria and Actinobacteria,promoting the conversion of nitrogen and phosphorus.By measuring the microbial community structure during soil column cultivation,the immobilized carrier corncob had a greater impact on the soil bacterial community than the marine bacteria.After immobilization treatment,catalase activity decreased,urease activity and alkaline phosphatase activity increased significantly,improving the bioavailability of nitrogen and phosphorus in soil systems.(3)The effects of different treatments on the quality of drainage water were investigated through simulated salt washing tests to assess the leaching of nitrogen and phosphorus.The results showed that in the treatment of immobilized marine bacteria,immobilized carrier corn cob alleviated the NO3-N loss,and marine bacteria CF8-6 alleviated the NO2-N and NH4-N loss.Corn cob provided a stable environment for marine bacteria,so that marine bacteria could give full play to the performance of phosphorus fixation,significantly reducing the concentration of P04-P and TP in salt washing and drainage.In summary,this study screened the optimal immobilized marine bacteria combination-corn cob immobilized CF8-6 that can be used to fix nitrogen and phosphorus in the salt washing process of abandoned salt fields.It realized microbial reclamation and applied the theoretical basis for improving saline soil.