棉花秸秆热解产物对新疆盐碱土壤的改良作用及机理研究

Xinjiang is the biggest inland provinces in China and the saline-alkali soil area accounts for 25% of total area of Xinjiang. The salinization of soil has become more serious in Xinjiang with improper cultivation in recent years, which has seriously restricted the development of local agriculture. Besides, Xinjiang province has the largest cotton-producing area in China, and the higher production of cotton means the greater output of byproducts. A large quantity of cotton stalk became an environmental problem, especially after it had lost their importance as fuel or feed. Therefore, there is an urgent need to explore new applications of cotton stalk and solve the above environmental problem . Taking the utilization of agricultural wastes as priority to solve the problems of soil salinization, we investigated the effect of operation parameters on pyrolysis behavior of cotton stalk through pyrolytic process, especially on the composition of biochar and wood vinegar. Based on these studies, pyrolytic products would apply in alkali-saline soil to elucidate the relationship between surface structural properties of the biochar, the composition of wood vinegar and the improvement effect, and to reveal the mechanism of pyrolytic products for improvement saline-alkali soil. In addition, an new ameliorant's preparation method of energy conservation and consume reduction would be found while keeping the improvement effect of saline-alkali soil. Though the project is performance, the sustainable use of saline-alkali soil would be considered, and special purpose ameliorants from cotton stalk would be developed.

新疆作为中国面积最大的内陆省区，盐碱地约占其土地面积的1/4，且近年来土壤盐渍化状况不断加重，严重制约了当地农业的发展。此外，新疆作为中国最大的棉花产区，棉花秸秆资源丰富，且一直未得到合理、有效的利用，亟需找到新的合理利用途径。本项目从新疆农业发展过程中的土壤盐渍化问题出发，以当地产量巨大的农业废弃物资源的合理利用为前提，通过对棉秆热解过程的研究，明确热解条件对产物（炭与木醋液）分布、棉秆炭表面结构及木醋液组分形成的影响规律；在此基础上，通过对棉秆热解产物的盐碱土改良过程进行研究，阐明炭的结构特性、木醋液的组分构成与改良效果间的内在联系，揭示棉秆热解产物的盐碱土改良机理，在保证改良效果的前提下，建立工艺简单、成本低、能耗小、资源化率高的棉秆热解产物型盐碱土改良剂制备工艺，为拓展棉秆应用途径、解决盐碱地利用问题奠定基础。

新疆是我国盐碱化面积最大的省，同时也是我国产棉量最大的地区。本研究就此出发，以棉秆作为原料，考察热解条件对产物分布与特性的影响，在此基础上将热解产生炭与木醋液应用于盐碱土改良。主要得到以下结论：. 1）热解温度对棉秆的热解产物分布有着显著的影响。随着温度升高，棉秆炭的产率和H/C值降低，炭化程度升高; 棉秆炭的比表面积和热解液产率呈现先升后降的趋势，液相产物中总多酚含量上升，总酸含量逐渐减少。. 2）棉杆炭的施加会促进盐碱土中植物的发芽，但只有适宜的炭比表面积与施加量才会促进植物的生长。吸附炭基肥与造粒炭基肥相比，前者有着更优的盐碱土改良特性。其施加可以降低土壤的全盐量，增加土壤pH值，促进盐碱土中小麦的发芽、生长与抗逆性，增加土壤中速效氮、磷、钾的含量以及蔗糖酶、碱性磷酸酶和脲酶活性。. 3）棉秆粗热解液不能有效促进盐碱土中植物发芽。分级冷凝是与盐析萃取更优的精制方式。三级冷凝产物木醋液对小白菜的发芽率、株高及株重以及抗逆性指标有明显促进效果，同时它还能降低盐碱土的pH、全盐量，增强多种土壤酶的活性以及土壤有机质、碱解氮、速效磷及速效钾的含量。以木醋液为基底构建的木醋液肥可以进一步增强改良效果。. 4）催化剂的添加可以有效提升棉秆木醋液的产率，降低其中酚类物质含量。以FeCl3为催化剂时制备的催化木醋液与原木醋液相比，有着更优的改良效果。相对于单一处理，生物炭与木醋液的联合处理可以更为有效的提升土壤脲酶、碱性磷酸酶的活力，增加植株中叶绿素的含量，但会降低土壤中微生物的群落丰度。但是相对于联合处理，催化木醋液肥可以更为有效的促进植物的生长，提高植物的抗逆性，增加盐碱土壤中脲酶、蔗糖酶以及碱性磷酸酶的活性，但也会部分降低土壤中微生物的群落丰度。但是比较而言，催化木醋液肥是棉秆热解产物制备盐碱土改良剂的最优工艺。