棉秆热解分级冷凝产物改良盐碱土效果

Improved effect of saline soil by grading condensate of cotton straw pyrolysis fluid

为揭示分级冷凝热解液对盐碱土的改良作用,该研究以三级冷凝方式作为棉秆热解液精制方法,分析分级冷凝对产物组成影响;在此基础上,利用盆栽试验,以不同热解温度下获得的棉秆分级冷凝第3级产物稀释不同倍数后施入盐碱土,考察分级冷凝第3级产物对于小白菜生长、土壤pH值、全盐量、蔗糖酶、脲酶、碱性磷酸酶、过氧化氢酶、有机质,碱解氮、速效磷和速效钾的影响。结果表明:1)分级冷凝可以达到棉秆热解液从源头分离的目的,实现酚类与酸类物质的粗分离,分级冷凝第3级产物的酚类与酸类物质浓度分别为单级产物的0.50~0.55与1.21~1.35倍。2)灌施分级冷凝第3级产物可以显著促进小白菜的萌发与生长(P<0.05),热解温度与稀释倍数均会影响促进作用。中温热解以及较大的稀释倍数对种子萌发更有利,500℃热解获得分级冷凝第3级产物稀释600倍灌施时,小白菜的长势最好,发芽率、株高与株质量分别提高32.12%、95.11%与120.03%,丙二醛含量降低48.39%。3)灌施分级冷凝第3级产物会显著影响土壤酶活性,除稀释50倍时降低土壤脲酶与碱性磷酸酶活性外,其他稀释倍数下土壤中酶活性显著增加(P<0.05)。4)灌施分级冷凝第3级产物会显著降低盐碱土的pH值与全盐量,显著增加盐碱土的有机质,碱解氮、速效磷和速效钾的含量(P<0.05)。上述结果表明,分级冷凝第3级棉秆热解产物可有效对盐碱土进行改良,热解温度与稀释倍数会显著影响改良效果,该研究能够为生物质热解液在盐碱土改良中的应用提供一定理论依据。

A huge area of saline-alkali land cannot be cultivated in China, due to the salt stress and low nutrient. Pyrolysis fluid with high acidity has been used to improve the saline soils. Among them, phenolic substances are adverse to the growth of plants. Therefore, the aim of the study was to explore the improvement effect of pyrolysis fluid on the saline soils, in order to efficiently reduce the phenols during pyrolysis. Firstly, the pyrolysis fluid was prepared at different temperatures(300, 400,500, 600, and 700 ℃), and then refined under the three-stage condensation mode. Secondly, an analysis was made to clarify the effect of graded condensation on the product composition. Taking the Chinese cabbage as an indicator, a pot experiment was performed on the saline soils using the tertiary product under different dilution folds(50, 200, 400 and 600). Finally, a systematic investigation was implemented to determine the effects of the tertiary product on the growth of Chinese cabbage,soil p H, total salt, sucrase, urease, alkaline phosphatase, catalase, organic matter, alkaline digested nitrogen, fast-acting phosphorus and potassium. The results showed that: 1) No new substance was found in the tertiary product from the pyrolysis fluid phase during three-stage condensation, compared with the single-stage. The graded condensation was used to realize the rapid and efficient separation of phenols and acids from the fluid phase products of cotton stalk pyrolysis. The concentrations of phenols and acids in the secondary product were 2.18-2.24 and 0.07-0.11 times higher than those by the single-stage,respectively. In the tertiary product, the concentrations of phenols and acids were 0.50-0.55 and 1.21-1.35 times higher than those by the single-stage, respectively. 2) The tertiary product significantly promoted the germination and growth of the Chinese cabbage(P<0.05). This promotion also depended mainly on both pyrolysis temperature and dilution ratio. The medium pyrolysis temperature and the larger dilution folds were more favorable for the Chinese cabbage seed germination.The best growth of Chinese cabbage was observed in the T500-D600 treatment(pyrolysis temperature of 500 ℃, dilution fold of 600), with 32.12%, 95.11%, and 120.03% increase in the germination rate, plant height, and fresh weight per plant,respectively, while 48.39% decrease in the malondialdehyde content. 3) The soil enzyme activity was dominated by the irrigation of the tertiary product with different dilution ratios(P<0.05). Interestingly, the activities of urease and alkaline phosphatase were reduced, only when the tertiary product was diluted by 50 times into the saline soil. Additionally, the activities of urease, alkaline phosphatase, sucrase and catalase in the saline soil increased by 218.13%, 123.65%, 64.78%, and 36.87% respectively, compared with the control. 4) The tertiary products significantly reduced the pH and total salt amounts in the saline soil, whereas, there was a significant increase in the nutrient contents(P<0.05). The contents of organic matter,alkaline soluble nitrogen, fast-acting phosphorus, and fast-acting potassium in the saline soil increased by 64.86%, 33.07%,64.65% and 17.29%, respectively. Anyway, the tertiary-stage condensation products of cotton stalk pyrolysis greatly contributed to the high fertility and enzyme activity of saline soil, as well as the better growth of Chinese cabbage. This finding can provide a sound theoretical basis for the biomass pyrolysis fluid to improve the saline-alkali land.