Lake Extract Algae-grass-mud Matrix And Its Effectiveness And Safety Evaluation

In recent years,algae blooming is becoming more and more frequent because of the water eutrophication.It really has affected the safety of surrounding residents,drinking water and ecological environment security.The urgent needs that repair of the water eutrophication and governance of lake extract such as algae、aquatic plants and dredging sludge etc are badly imminent.If not handle with the lake extract that brought ashore in time,the water and soil on the yard would suffer from secondary pollution.Therefore,lake extract harmless resource utilization technology has become the focus in the governance of eutrophication of water.Lake extract contained much nitrogen,phosphorus and other nutrients.If compost with lake extract,it can be made into high quality organic fertilizer.It not only can solve the trouble back at home of lake extract and avoid the problem of secondary pollution,realize the utilization,also developed a new type of organic fertilizer.This experiment discusses the use of cyanobacteria,water hyacinth and Chaohu dredging sediment as a raw material for composting treatment,during the composting process the changes of the nutrient content and the final product of composting may cause the effects on soil and crops in safety evaluation after back field.The main results were as follows:(1)The changes of physical and chemical parameters during compostingUse 40%algae,40%aquatic plants and 20%mud to compost.At first,the pile body temperature rises from 39.4℃ which the environment temperature is,then reaches to peak temperature 63.5℃,the temperature 60℃ lasts more than 6 days later,then reduces to less than 60℃,then composting enters the cooling phase and finally dropped to 370.5℃,gradually stabilized.During the whole process,the pile temperature lasts above 50℃ and keeps 15 days which conforms to the hygiene standards.The moisture shows a trend of gradual decline from the original 61.51%to 52.74%,but still in the range of optimum moisture content.TN content changes slightly,from 1.09%to 1.06%,and intermediate process changes in wavy.NH4+-N content starts with increasing then decreasing,to the end of the compost,NH4+-N content decreases from 39.32mg/kg to 38.73 mg/kg.TP content increases gradually during the composting process,until the end of composting,the TP content rises from 0.33%upto 0.42%.The organic matter content gradually reduces from41.76%to 34.72%,but humic acid content increases from 13.57%to17.31%.C/N mainly shows a trend of decline,and ultimately reduced to less than 20,can determine the terminal of composting.(2)Study on fertilizer of algae-grass-mud substrateIn order to study the effect of the application of the algae-grass-mud substrate on soil nutrient and crop yield,and the transition and enrichment of heavy metals in soil and plant,the experiment sets 6 groups treatments.Average vegetable output of the various treatments:algae-grass-mud organic fertilizer+ perlite>algae-grass-mud organic fertilizer + vermiculite>algae-grass-mud organic fertilizer>commercially available organic fertilizer>algae-grass-mud organic fertilizer+urea>urea.Algae-grass-mud organic fertilizer has a certain positive promotion effect on green vegetables production.After harvest,the organic matter contents of soil which applying of algae-grass-mud organic fertilizer + perlite,algae-grass-mud organic fertilizer + vermiculite and algal-grass-mud organic fertilizer are 29.1 g/kg,28.91 g/kg and 28.01 g/kg,and are more than the 23.12%of algae-grass-mud organic fertilizer + urea and 21.74%of urea.After harvest,compared with the 1.763g/kg of single urea,the TN content of algal-grass mud organic fertilizer + perlite,algal-grass-mud organic fertilizer + vermiculite and algal-grass-mud organic fertilizer are 1.955g/kg,1.942g/kg and 1.937g/kg and more higher.Use of algal-grass-mud organic fertilizer and its matrix has not only increases yield and can increases soil organic matter and TN,it has a role in increasing fertility.(3)Safety evaluation of algae-grass-mud substrateThe five kinds of heavy metal contents in algal-grass-mud organic fertilizer are:Pb:0.161 mg/kg,As<0.04 mg/kg,Cr:0.294 mg/kg,Cd<0.01 mg/kg,Hg<0.046 mg/kg,and the contents are far lower than the contents of organic fertilizer in the limited index requirements,therefore comply with the safety standards for heavy metal organic fertilizer.Use mei’s pollution index method to evaluate the five kinds of heavy metal of algal-grass-mud organic fertilizer or its matrix,the contents are Pb:0.2430.002mg/kg,As<0.04mg/kg,Cr:0.115mg0.002/kg,Cd<0.01mg/kg,Hg<0.046mg/kg,the result shows that the comprehensive pollution index of a soil is far less than 0.7,soil is clean level and is a safe level.The four kinds of heavy metals(Pb,As,Cr,Cd)contents of potted vegetables are comply with the regulations of the state administration of quality supervision bureau safety requirements of the agricultural product safety and quality of pollution-free vegetables.Mercury(Hg)content is below the instrument detection limit(0.046 mg/kg)and did not check out,cannot be compared with the national pollution-free vegetable safety requirements.