【作者】 史一鸣；

【导师】 吕军；

【作者基本信息】 浙江大学 ， 水资源利用与保护， 2010， 博士

【摘要】 随着农业产业结构调整、畜禽养殖业规模化发展,畜禽粪尿和冲洗用水过度集中并大量无序排放,不仅严重污染临近水体和周边环境,还直接影响畜禽养殖的防疫卫生,制约畜牧业的持续健康发展。在目前的畜禽养殖废弃物的处理途径中,特别是在循环经济的倡导和各级政府的支持下,利用沼气发酵工艺将畜禽粪污进行生物质能转化,已经成为最具经济、社会和环境效益的方法之一。但是,沼气工程大发展带来的突出问题就是沼气发酵的尾产物沼液的处置问题,因为沼液是富含COD、BOD、SS、总氮、氨氮、总磷等的有机污染物质,而仅作为当地肥料使用远不能满足对源源不断并且日益增加的沼液的处理需求。特别是对于规模化畜禽养殖场的日产沼液达一、二百吨的情况,如何处置沼液已经成为亟待解决的重大环境问题。因此,本研究根据我国南方稻田遍布的现实条件,试图在维持和促进水稻优质高产和确保土壤质量健康的前提下,尽可能地充分利用稻田湿地生态系统和水稻生产对沼液的消解和净化能力,建设和开发水稻粮食生产和沼液处理相结合的人工湿地生态系统。然而,水稻作为我国最重要的粮食作物之一,大量沼液投入到稻田,到底会不会给水稻生产带来风险,并给水环境、土壤肥力、土壤环境质量健康、土壤微生物生态等带来怎样的影响,是必须回答的问题。本文以养猪场沼液为研究对象,通过室内模拟和大田试验,探讨了沼液的自净及其在稻田生态系统消解净化过程中对水稻生产和环境的影响,研究了沼液淹灌过程中土壤肥力和土壤微生态的变化规律；分析和监测了稻田消解沼液过程对水稻产量和品质安全以及土壤环境质量的影响。为全面了解水稻生长和稻田生态系统对沼液的响应规律,分析稻田生态系统消解沼液的潜力,优化沼液排放模式提供理论与技术依据。主要结论有：1、沼液自净过程的研究表明,静置条件下沼液自身的生境条件对微生物生存不利,严重抑制了微生物的活动,削弱了微生物的自净能力。沼液的自净作用主要依赖于物理和物理化学过程、化学过程。施灌到稻田以后,在微生物、作物等生物因子的参与下,大大强化了沼液的消解、净化过程；在沼液灌后12天内,田面水N、P、CODMn浓度基本可达到空白对照田的水平。在本试验的传统水稻种植区,由于稻田犁底层发育良好,施灌沼液引起的地下水铵态氮污染风险不大,4倍N沼液处理田块(2400 t ha-1的沼液用量)的地下水NH4+-N浓度小于常规化肥N用量的田块。施灌沼液不会导致当季地下水硝态氮浓度超标(生活饮用水卫生标准GB／5749-2006)。施灌沼液对当季地下水CODMn的浓度的影响不显著。2、大量施灌沼液使土壤氮、磷含量提高,土壤氮、磷含量与沼液施灌量呈显著正相关；土壤有机质含量及其腐殖化强度无明显增强；所用沼液没有对土壤过氧化氢酶与蔗糖转化酶活性产生明显影响；土壤pH、水溶性盐电导率与沼液施灌量显著正相关,施灌沼液在一定程度上影响土壤的酸碱性,但还远不足产生盐害。3、沼液淹灌室内培养试验结果表明,土壤微生物种群数量增加,而PLFA总量有下降趋势；细菌、真菌、好氧菌的特征脂肪酸总量所占比例基本保持不变。土壤中放线菌、甲烷氧化菌、硫酸盐还原菌的特征脂肪酸总量和所占比例均有显著下降；土著优势种群结构长时间保持稳定,表明稻田土壤微生态具有较强的调整内部种群结构的能力,较快适应沼液淹灌环境；水稻土微生态区系中共有的优势特征脂肪酸总量的判别分析结果表明,0.5倍N至等N沼液灌溉量对土壤优势微生物的影响最小,1.5倍N沼液灌溉量尚不会破坏稻田土壤微生物的区系构成。4、现有沼液施灌水平下(最大沼液灌溉量为2400 t ha-1),土壤重金属含量未因施灌沼液有显著提高,土壤中重金属均符合保障农业生产,维护人体健康的国家土壤环境质量标准(GB／15618-1995)。5、水稻田间试验结果表明,2倍N沼液处理的产量最高,当沼液用量达到4倍N处理时出现倒伏等现象,虽然产量较常规化肥处理没有下降,但边际增产效应下降；施灌沼液处理的稻谷中重金属含量与空白处理以及正常化肥处理之间没有显著差异。沼液施灌量的增大未对稻谷中重金属含量产生显著影响。稻谷中重金属含量未超出国家食品中污染物限量标准(GB／2762-2005)。随沼液用量增加,稻谷胶稠度、赖氨酸含量下降,直链淀粉含量、粗蛋白含量影响效果不明显。6、做为处理废水为目的的稻田湿地生态系统,要解决的关键问题是在确保水稻安全生产的基础上尽可能增加单位面积的沼液负荷量,而且不仅要保证水稻的产量和品质安全,还应该避免土壤退化,防止土壤生态遭到破坏以及土水环境遭到污染,保障稻田生态系统的健康运转。但在稻田生态系统中,针对沼液的粮食产量、微生态承载量和环境承载量三者并不完全一致；如何确保水稻持续高产和品质稳定的条件下,尽可能地协调三个目标优化组合,构成了稻田湿地生态系统消解沼液的多目标优化问题。本研究对试验地区沼液的施灌量的优化做了初步探讨,提出两种优化方案：方案1,以水稻产量最大为优先目标,环境安全最大承载量为第二目标,生态安全最大承载量为第三目标。产量最高的2倍N沼液处理为最优,既能保障水稻产量、品质安全,又不对稻田生态、环境产生破坏,水稻种植期的沼液总共承载量折算为1200 t·ha-1；方案2,以环境安全最大承载量为第一目标,粮食安全最大承载量为第二目标,生态安全最大承载量为第三目标。则4倍N沼液处理为最优,既能维持粮食稳定高产,又满足消解容量最大化的沼液处理目标,水稻种植期的总承载量折算为2400 t·ha-1。更多还原

【Abstract】 With the adjustment of agricultural structure and the development of livestock and poultry breeding, excessively centralized and the massive disorderly emissions of livestock manure and flushing water not only polluted the adjacent water body and the surrounding environment, but also hindered epidemic prevention of poultry cultivation. Under the guidance of "recycle economy" and supported by the government, the biogas fermentation engineering was rapid developed in Chinese rural region as an economic, social and environment-friendly method for the organic wastewater treatment. However, the knotty problem of biogas project is how to dispose massive biogas slurry, because there are still very high contents of DOM, SS, N, P and nutrients in biogas slurry. Just treating biogas slurry with local fertilizing can’t use up so much and continuously increasing biogas slurry, especially for the livestock and poultry breeding in large scale. Paddy field ecosystem is a typical constructed wetland ecosystem and it has a very wide distribution in south and east China. Therefore, the subject of this study aims to build the paddy field as an artificial wetland ecosystem with both functions of rice production and organic wastewater treatment under the premise of rice production and soil quality safety assurances. Accordingly, our research activities focus on how to support and improve rice production and soil quality under high concentration of organic wastewater conditions, how to increase the decontamination potentials of the paddy field ecosystem, and how to prevent risks resulted from the high discharge of wastewater in the field. In this study, field and laboratory experiments were conducted with the heavy irrigation of biogas slurry to investigate the purification process of the slurry and its influences on the rice production and the environment of paddy field ecosystem. The results provide theoretical basis and technical guidance for comprehensive understanding the response of paddy field ecosystem to the heavy irrigation of biogas slurry, exploring the potential capacity of paddy field to decontaminate biogas slurry and optimizing discharge mode for the heavy irrigation of biogas slurry. The main results are summarized as follows:1. Self-purification of biogas slurry mainly depends on physical and physicochemical processes, but not on microbial activities because microbial activities were strong limited under the conditions of biogas slurry itself. After discharging biogas slurry into paddy field, paddy ecosystem plays a leading role in decontaminating and purifying biogas slurry. With the participation of micro-organisms, plants and other biological processes, the abilities of decontamination and purification of biogas slurry significantly increased. Up to 12 days after biogas slurry irrigation, the concentration of N, P, CODMn in surface water basically reached to CK level. Under 4N biogas slurry irrigation treatment (2400 t-ha-1), NH4+-N concentration in the ground water is smaller than 1N chemical fertilizer treatment, and biogas slurry irrigation will not cause NO3--N pollution in the ground water in current season. The CODMn concentration of groundwater had not varied significantly.2. After irrigation of biogas slurry, soil N and P content was significantly increased, and were positively related to the quantity of biogas slurry irrigation. Soil organic matter content and its metabolic processes had no significant enhancement in short term. There were no obvious adverse effects on soil catalase and invertase activities; Soil pH and the electric conductivity of the soil were positively correlated with biogas slurry irrigation quantity. It indicated that biogas slurry could modify soil acidity in some sense, but it can’t go so far as soil salinization.3. Biogas slurry flooding decreased the content of total PLFAs compared with non-flooding soil. After flooding by biogas slurry, the characteristic PLFA for bacteria, fungi, aerobic bacteria were almost unchanged, however, the contents and characteristic PLFA for actinomyces, methanotrophic bacteria and sulfate deoxidation bacteria were significantly decreased; The diversity of soil microbial PLFAs was significantly improved due to the exogenous micro-organisms in biogas slurry, conversely, the contents of total PLFAs extracted from the different treated soil were declined, while the dominant soil PLFAs maintain long-term stability under the same condition. It indicated that the micro-ecology of paddy soil could rapidly screen out the priorities and discard the inferior population, adjusting the internal microbial community structure, thus reach the purpose of adaptable environment. Discrimiant analysis and principal component analysis were used to analyze the dominant PLFAs, and the results showed that treatments 0.5N-1N treatments didn’t significantly weakened soil dominant microbial community and microbiologic population. Meanwhile, treatment 1.5N had not yet lead to a devastating impact on the paddy soil microbes. After the biogas slurry irrigation, soil-microbial community structure changed little, which indicated soil ecosystem has the resilience and resistance to maintain its health status in short period.4. Soil heavy metals did not show the significant increase in the paddy fields with the biogas slurry irrigation (maximum to 2400 t ha-1). The content of heavy metals all accord with the national environmental quality standards (GB/15618-1995).5.2N biogas slurry treatment resulted in the highest rice yield. Although rice lodging appeared in 4N biogas slurry irrigation treatment, the yield had not declined significantly. The concentrations of all heavy metals in rice grain were not significantly different among the treatments of the heavy irrigation of biogas slurry, chemical fertilization and CK. The contents of heavy metals in rice grain all accord with the National Standard(GB/2762-2005). With increase of the slurry irrigation, the gel consistency and contents of lysine of the rice declined, while the changes of amylase and crude protein were not significant.6. To ensure the safety for rice production, to maintain the sustainable functions of paddy field ecosystem and to consume more biogas slurry in unit paddy field are three goals for this study. But they are not fully consistent with each other. Therefore, the coordination and optimization of these three goals for the paddy filed wetland ecosystem for biogas slurry treatment is a multi-objective optimization problem. According to our research results, two optimization schemes were proposed to make a preliminary estimation of the irrigation quantity of biogas slurry in the experiment areas. The first scheme with rice yield grain as preferential goal followed by environmental safety and soil fertility maintenance respectively was suggested that 2N treatment of biogas slurry irrigation with the total consumption of biogas slurry 1200 t·ha-1 for one rice production season. The second suggested scheme was the maximal consumption of biogas slurry followed by rice yield and soil fertility maintenance respectively:4N treatment of biogas slurry irrigation with the total consumption of biogas slurry 2400 t·ha-1 for one rice production season.更多还原