γ-聚谷氨酸和耐盐植物联合修复设施栽培盐渍化土壤

发布时间：2018-09-17 12:31

【摘要】：设施农业是随农业现代化和种植结构调整发展起来的新型产业,是最具活力的现代化农业,也是传统农业向现代化集约型农业转变的有效方式。近年来我国设施农业发展迅猛,2008年设施栽培面积突破330万hm2,约占世界设施农业总面积的85%,其中设施蔬菜种植面积达到34.7万hm2；2010年我国设施蔬菜总产量超过1.7亿吨,占蔬菜总产量的25%。设施农业生产中大水大肥灌溉、土壤连作障碍经常发生,养分失衡严重,土壤中大量盐分随水分蒸发向上运动而聚集在土表,造成土壤板结和次生盐渍化等环境问题,导致农产品的产量和质量下降。其中,设施土壤次生盐渍化问题最为突出。目前,全球次生盐渍化土壤面积达到7700万hm2,占农业土壤面积的30%以上,其中58%的盐渍土分布在农业灌溉区,并呈现逐年增加的趋势。土壤次生盐渍化已成为阻碍我国设施农业发展的主要问题,修复次生盐渍化土壤是设施农业生产中亟待解决的环境问题。引起设施土壤次生盐渍化的原因很多,主要有环境因素、盲目施肥、不合理灌溉和种植方式等。次生盐渍化的发生不仅造成设施土壤营养失衡,肥力下降,还会阻碍植物的吸水过程,对作物产生毒害作用,导致作物的产量和品质下降；次生盐渍化还会影响土壤微生物的生长和群落结构,抑制微生物活性。目前,盐渍化土壤的改良和修复手段主要有工程措施、化学措施、生物措施和农业措施,虽然取得了一定成效,但还存在建设投资大、运行成本高、容易造成二次污染、修复效果差或人为影响大等问题,特别是单一措施的修复能力非常有限,必须将多种修复手段相结合。耐盐植物包括稀盐植物(或真盐生植物)、泌盐植物和拒盐植物(或假盐生植物)等,具有良好的脱盐能力,有关它们的筛选、开发与利用引起了学术界的关注。稀盐植物田菁被广泛用于修复盐渍土,景天三七是新近发现的一种稀盐植物,它们不仅对Na+、K+、Ca2+、Mg2+、Cl-和NO3-等盐分离子具有一定的耐受能力,还能有效吸收这些离子。另一方面,γ-聚谷氨酸(γ-PGA)具有良好的水溶性、超强的螯合能力、生物降解性和环境友好等特点,已被用于废水中金属离子的去除研究,但在污染土壤修复中的应用还鲜见报道。本研究调查和分析了上海市郊主要园艺场出现耕作障碍的设施大棚土壤的盐分特征和盐渍化程度,应用统计分析方法,确定该地区次生盐渍化土壤的主要类型和主要盐分离子；针对该地区广泛分布的Ca2+-Mg2+-NO3型次生盐渍化土壤,利用γ-PGA螯合土壤中的Ca2+、Mg2+,降低其生物有效性；采用盆栽实验,研究景天三七和田菁对盐渍土中Ca2+、Mg2+和NO3-的吸收特征；将γ-PGA与耐盐植物联用,去除盐渍土中的Ca2+、Mg2+和NO3-,考察它们对次生盐渍土的修复效果。取得如下主要研究结果：1.随着种植年限的增加,上海市郊耕作障碍设施大棚土壤的平均含盐量呈现先升高后降低的趋势,非盐渍土、微盐渍土、轻度盐渍土、中度盐渍土、重度盐渍土和盐土分别占4.35%、17.39%、56.52%、4.35%、4,35%和13.04%。大棚盐渍土中含盐量与阴阳离子含量间的相关性较好,阳离子以Ca2+和Na+为主,其次为Mg2+；阴离子以NO3-和8042-为主,其次为Cl-, NO3是最主要的积累离子。施肥方式、种植年限、作物类型和管理水平都会影响次生盐渍化程度。根据典型对应分析(CCA),Ca2+、Mg2+和N03-积累量均随种植年限的增加而增大；长期单施有机肥或化肥,分别造成土壤碱化或酸化,加重土壤次生盐渍化；合理混施化肥和有机肥的大棚土壤盐渍化程度较低,且不受种植年限的影响。2.根据盐分离子和采样点的关系,将上海市郊设施盐渍化土壤划分为4种类型：Ⅰ号类型为崇明县的部分大棚土壤,受Na+、Cl和HCO3-的影响较大；Ⅱ号类型为崇明县的另一部分大棚土壤,受K+、Ca2+、Mg2+和NO3-的影响较大；Ⅲ号类型包括奉贤、闵行、青浦、部分南汇和部分嘉定地区的大棚土壤,主要受Ca2+Mg2+、N03和Cl-的影响；Ⅳ号类型为松江、部分南汇和部分嘉定地区的大棚土壤,主要受SO42-的影响。其中,大部分盐渍化土壤属于Ⅲ号类型,应重点控制。3.获得γ-PGA去除Ca2+、Mg2+的最佳条件,即γ-PGA的初始浓度为1000mg.L-1,混合体系的初始pH为7,温度为25℃在最佳实验条件下,γ-PGA对Ca2+、Mg2+的最大去除率分别达到51.59%和68.03%。二级动力学模型能够很好地描述γ-PGA对Ca2+、Mg2+的去除过程,获得Ca2+、Mg2+的去除速率常数分别为0.00282和0.0166(mg·L1)·1.min-1,其主要作用机制为γ-PGA的酰胺键和羧酸阴离子与Ca2+、Mg2+形成螯合物。4.景天三七对Ca2+、Mg2+_的最大去除率分别为64.35%和53.35%,对NO3也有较强的去除能力,最大去除率为51.78%；田菁对Ca2+、Mg2+的最大去除率分别为82.87%和45.55%。但是,田菁的根瘤菌具有固氮作用以及田菁残体的分解作用,使得土壤中N03-浓度维持在1.038 g.kg-1,比原盐渍土的N03-浓度提高了26.02%。5.盆栽实验发现,施入y-PGA不仅降低了Ca2+、Mg2+的生物有效性,减小了耐盐植物幼苗受到的盐分胁迫,还能促进植物的生长发育和抗逆性。监测耐盐植物的生理参数发现,1000mg·L-1γ-PGA和景天三七(J3)对Ca2+、Mg2+和N03。的处理效果最好,最大去除率分别达到93.25%、94.79%和84.26%；200 mg.L-1y-PGA和田菁(T1)对Ca2+、Mg2+的处理效果较好,最大去除率分别达到90.26%和69.92%。由于田菁根瘤菌的固氮作用和植物残体的分解作用,使得土壤中NO3。浓度维持在0.868 g-kg-1,比原盐渍土的NO3-浓度提高了5.36%。比较y-PGA、耐盐植物单一处理和联合处理的修复效果,获得修复Ca2+-Mg2+-NO3-型次生盐渍土的最佳组合为1000 mg·L-1 γ-PGA和景天三七(J3),总盐分的最终去除率达到74.71%。
[Abstract]:Facility agriculture is a new industry developed with the modernization of agriculture and the adjustment of planting structure. It is the most vigorous modern agriculture and an effective way to transform traditional agriculture into modern intensive agriculture. In 2010, the total yield of protected vegetables exceeded 170 million tons, accounting for 25% of the total yield of vegetables. In protected agricultural production, irrigation with large amount of water and fertilizer, soil continuous cropping obstacles often occur, nutrient imbalance is serious, a large amount of salt in the soil accumulated on the soil surface with the upward movement of water evaporation, resulting in soil erosion. Environmental problems such as soil compaction and secondary salinization have led to a decline in the yield and quality of agricultural products. Among them, secondary salinization of protected soils is the most prominent. At present, the area of secondary salinized soils in the world reaches 77 million hm2, accounting for more than 30% of the total agricultural soil area, of which 58% of the saline soils are distributed in agricultural irrigated areas, showing an increase year by year. Secondary salinization of soil has become a major obstacle to the development of facility agriculture in China. Rehabilitation of secondary salinized soil is an urgent environmental problem in facility agriculture. There are many reasons for secondary salinization of facility soil, such as environmental factors, blind fertilization, irrational irrigation and planting methods. The occurrence of salinization will not only cause the imbalance of soil nutrients and fertility, but also hinder the process of plant water uptake and produce toxic effects on crops, resulting in the decline of crop yield and quality. Secondary salinization will also affect the growth of soil microorganisms and community structure, inhibit microbial activity. There are engineering measures, chemical measures, biological measures and agricultural measures, although some results have been achieved, but there are still many problems, such as large investment in construction, high operating costs, easy to cause secondary pollution, poor repair effect or human impact, especially the repair capacity of a single measure is very limited, and a variety of restoration methods must be combined. Salt-tolerant plants, such as dilute salt plants (or euhalophytes), salt-secreting plants and salt-repellent plants (or pseudohalophytes), have good desalination capacity, and their screening, development and utilization have attracted academic attention. On the other hand, gamma-polyglutamic acid (gamma-PGA) has good water-solubility, strong chelating ability, biodegradability and environmental friendliness. It has been used in the removal of metal ions from wastewater, but in the remediation of contaminated soil. This study investigated and analyzed the salinity characteristics and salinization degree of greenhouse soils with farming obstacles in main horticultural farms in Shanghai suburbs. The main types and main salt segregators of secondary salinized soils in this area were determined by statistical analysis method. The bioavailability of raw saline soil was reduced by chelating Ca 2+, Mg 2+, with gamma-PGA; the absorption characteristics of Ca 2+, Mg 2+ and NO3 - by Sesbania Sesbania and Selaginella paniculata in saline soil were studied by pot experiment; and the effects of removing Ca 2+, Mg 2+ and NO3-, by combining gamma-PGA with Salt-Tolerant plants, on the restoration of secondary saline soil were investigated. The main results are as follows: 1. With the increase of planting years, the average salinity of greenhouse soil in the suburb of Shanghai increased first and then decreased. Non-saline soil, slightly saline soil, slightly saline soil, moderately saline soil, severely saline soil and saline soil accounted for 4.35%, 17.39%, 56.52%, 4.35%, 4,35% and 13.04% respectively. There was a good correlation between soil salt content and anion and cation content. Ca2+ and Na + were the main cations, followed by Mg2 +; NO3 - and 8042 - were the main anions, followed by Cl -, NO3 was the main accumulation ion. Fertilizing methods, planting years, crop types and management level all affected the degree of secondary salinization. +, Mg2+ and N03-accumulation increased with the increase of planting years; long-term application of organic fertilizer or chemical fertilizer resulted in soil alkalization or acidification, which aggravated soil secondary salinization; reasonable mixing of chemical fertilizer and organic fertilizer in greenhouse soil salinization degree is low, and is not affected by planting years. 2. According to the relationship between salt separator and sampling points, the salinization degree will be lower. The greenhouse soils in Shanghai suburbs can be divided into four types: part of the greenhouse soils in Chongming County are of type I, which are greatly affected by Na +, Cl and HCO3 - and part of the greenhouse soils in Chongming County are of type II, which are greatly affected by K +, Ca 2 +, Mg 2 + and NO3 - respectively; part of the greenhouse soils in Fengxian, Minhang, Qingpu, Nanhui and part of Jiading are of type III. The greenhouse soils in this area are mainly affected by Ca2+Mg2+, N03 and Cl-, and the type IV is Songjiang, some Nanhui and some Jiading areas are mainly affected by SO42-. Most of the saline soils belong to the type III and should be controlled emphatically. 3. The optimum conditions for removing Ca2+, Mg2+ by gamma-PGA, i.e. the initial concentration of gamma-PGA is 1000mg.L. The maximum removal rates of Ca2+ and Mg2+ by gamma-PGA were 51.59% and 68.03% respectively under the optimum experimental conditions. The second-order kinetic model could well describe the removal process of Ca2+ and Mg2+ by gamma-PGA, and the removal rate constants of Ca2+ and Mg2+ were 0.00282 and 0.0166 (mg.L1). 1.min-1, respectively. The mechanism of action is that the amide bond of gamma-PGA and the anion of carboxylic acid form chelate with Ca 2+, Mg 2+. 4. The maximum removal rates of Ca 2+, Mg 2+, and NO 3 are 64.35% and 53.35% respectively, and 51.78% respectively, and 82.87% and 45.55% for Ca 2+, Mg 2+ respectively. Nitrogen fixation and Sesbania residue decomposition kept the concentration of N03-in the soil at 1.038 g.kg-1, which was 26.02% higher than that of the original saline soil. 5. Pot experiments showed that the application of y-PGA not only reduced the bioavailability of Ca2+, Mg2+, but also reduced the salt stress on salt-tolerant plant seedlings, and promoted plant growth and development. Monitoring physiological parameters of salt-tolerant plants showed that 1000 mg L-1 gamma-PGA and Sesbania notoginseng (J3) had the best effect on Ca2 +, Mg2 + and N03. The maximum removal rates were 93.25%, 94.79% and 84.26% respectively; 200 mg L-1y-PGA and Sesbania (T1) had the best effect on Ca2 +, Mg2 + with the maximum removal rates of 90.26% and 69.92% respectively. Nitrogen fixation by rhizobia and decomposition of plant residues resulted in the concentration of NO3 in soil being maintained at 0.868 g-kg-1, which was 5.36% higher than that of the original saline soil. Compared with y-PGA, the best combination of single treatment and combined treatment of salt-tolerant plants was 1000 mg-L-1 gamma-PGA and landscape treatment. 37 (J3), the final removal rate of total salt reached 74.71%.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S156.41

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