Degradation Characteristics Research Of Full Biodegradable Dry Algae Polysaccharides Mulch

Mulching cultivation technology due to its prominent role in agricultural production has been widely used, but the plastic mulch is difficult to break down in the fields, and its long-term use on farmland has caused serious pollution. Therefore, full degradable film covering is an effective way to solve the "white pollution". In order to solve this problem, algae chemical laboratory of Ocean University of China has used the alginate successfully produced pollution-free environment-friendly biodegradable mulch new products. This dry algae polysaccharides mulch contributes a good yield in applied research, but there is also a lack of knowledge on degradation characteristics of the dry algae polysaccharides mulch. Therefore, this article evaluates the degradation characteristics of the mulch systemically from the light, biodegradation and other aspects and explore the effects of different soil moisture and temperature during the degradation process. The results are as the following:1. The mulches are put in the accelerating aging chamber with light treatment. On the 30th,60th,90th day that mulches accept light treatment, observe the surface morphology by scanning electron microscopy, on the 15th,30th,45th,60th,75th, 90th day measure its water content, weight, thickness, transparency, tensile strength, elongation at break rates and the relative molecular weight of algae polysaccharide, compare with the original sample, and evaluate of the light degradation properties of the mulch comprehensively. The results shows that within 90 days time that dry alginate polysaccharide mulches accept light degradation, the apparent shape did not change significantly, and the water content decreased 5.19%,7.10% weight reduction with thickness decreased 44.56%, transparency decreased about 15%, tensile strength decreased 62.48% and elongation at break decreased 82.05%. The relative molecular weight of algae polysaccharide dropped from 2079696 to 96827, suggesting a significant degradation has occurred. During induction period of 30 days, mulch maintained good performance; 30 days afterwards entering the photolysis of mechanical properties decreased. Bury the dry algae polysaccharides mulch after 90 days’light treatment in the soil, mechanical strength has totally lost within 10 days; film form is destroyed, mass loss rate of 26.34% and algae polysaccharides relative molecular weight down to 87859. Thus, the dry algae polysaccharide mulch has good optical performance degradation, but does not affect performance during use.2. In particular microorganisms, soil suspension, alginate lyase for microbial source, weight loss, microbial growth curve, CO2 content, algae polysaccharides relative molecular weight are measured for degradation characteristics of dry algae polysaccharides mulch, where the conclusions are:soil fungi, bacteria, and actinomycetes on dry alginate biodegradable mulch have significant effects, the role of the order is actinomycetes> bacteria> fungi; dry soil suspension also has degradation effects for alginate film, where degradation over 84 days time generated CO2 of 39.565mg, with film weight loss of 62.915mg, so the film is not only released CO2 during the degradation, but there may also be glycerol, water and oligosaccharide dissolute. Alginate lyase shows good effect for the degradation, where the degradation rate is faster without generating harmful substances.3. At temperature of 25℃, take air-dried soil,8%,13%,18%,25%RH soil for bury dry algae polysaccharides mulch, in 13% RH soil moisture, respectively at 4℃, 15℃,25℃,35℃,45℃ conditions bury dry algae polysaccharides mulch, investigate the effect of different soil moisture and temperature conditions for degradation characteristics of dry algae polysaccharides mulch. The study find that at temperature of 25℃ and humidity of 25%, the soil mulch degrades fastest with weight loss rate of 45.57% over period of 19 days; under 13% humidity at 25℃ mulch degrades with the fastest rate, with 62.91% of weightlessness during 49 days.dry algae polysaccharides mulch buried in the soil, the changes of Ca2+, Pb2+, Zn2+, Cu2+ in the mulch are in different levels, indicating that the mulch can adsorb heavy metal ions in soil, and then improve the soil environment.