导　　师： 许振成;彭晓春

学科专业： 083002

授予学位： 硕士

作　　者： ;

机构地区： 湖南农业大学

摘　　要： 随着城镇化的发展,以及生活水平提高,城镇食品消费结构发生显著变化,城镇居民家庭食物中摄入的氮素来源和数量也都相应发生了变化。城镇化改变了有机物生态循环系统,割断了有机排泄物及废弃物与原来的土壤生态系统的联系,使城镇的有机排泄物及其他废弃物又不能有效地进入土壤生态系统。同时,氮素作为食物蛋白质的重要成分,随着食物生产和消费而流动,其流动模式和流量与生态环境质量密切相关,未经处理粪尿排泄物和生活污水大量排入城市河涌后,引发起严重的水体富营养化问题。因此,本研究主要在利用国务院污染源项目中的“城镇生活污染源产排污系数测算研究”项目中的试验数据的基础上,采用物质流分析的方法,通过对我国城镇家庭食物消费体系氮素流动特征进行了初步探讨,以期为我国城镇化健康发展、保证资源环境安全提供理论依据。主要研究结果如下： /(1/)通过分析1981-2007年中国城镇居民家庭人均食物氮年消费量的趋势变化,并进行ARIMA模型时间序列预测分析,揭示了中国城镇化过程中城镇家庭食物氮消费的发展变化规律。结果表明,80年代后城镇居民食物氮年消费量经历了上升-下降-再上升的变化趋势,总体上处于轻微的上升趋势；随着经济快速发展和城镇化进程加快,未来居民食物氮消费量仍然保持持续上升状态,并且具有较大的上升空间。 /(2/)食物食用加工过程是一个多种单元操作的耦合的复杂过程。本研究通过模拟试验法,有针对性地对典型食物加工过程进行观察,以估算食物加工过程氮素流失比。结果表明：不同类别的食物在加工过程中氮素排入生活污水的流失比例存在明显差异,总体上,水产品>粮食、蔬菜>肉类>蛋类,氮素流失比分别为：粮食、蔬菜、肉类、蛋类、水产品分别为：16.00/%、17.00/%、5.00/%、7.00/%、27.00/%。这为制定食品加工过程产污系数和优化烹饪工艺降低污染负荷提供了理论指导。 /(3/)采用巢式设计进行了人体排泄试验,着重考察了影响污染物排泄系数的几个相关因素。试验结果表明：TN, TP的排泄系数比COD, BOD5的排泄系数要高得多,这反映了人体对氮、磷元素的吸收率比较低,说明了摄入相同数量的潜在“污染物”,人体粪尿排泄物中氮、磷排泄量比例较大；除COD排泄系数外,其他污染物排泄系数均是女性显著高于男性/(P<0.05/),这可能与男女之间的体重、消化能力以及体力消耗等性别差异有关；膳食结构与食物搭配也是影响污染物排泄系数的重要的因素,这可能与不同类别、种类的食物中表征COD、BOD5、TP、TN等物质的含量及其存在形式有关,应关注膳食结构的变迁引发的潜在的环境问题。不同食物在人体内的代谢途径以及食物中微量元素、外源酶等对人体代谢的调节机制还有待进一步研究。 再者,探讨了年龄、体质指数对人体粪尿氮排泄量的影响。结果表明,人体尿氮和粪氮排泄量分别为9.16g//cap//d、1.33 g//cap//d。粪、尿氮排泄量随着年龄增长呈递增趋势,但因机体体质的差别表现出一定的差异,总体上体质指数高者其尿氮也明显增多,而粪氮则没有明显变化。粪尿氮排泄模型综合考虑了这两个因素及其交互作用的影响。 /(5/)以城镇家庭为研究对象,探讨了家庭规模、家庭结构对生活污水排放特征的影响。结果表明：城镇家庭生活污水的排放特征与家庭规模、家庭结构密切相关,总体上各污染物指标随家庭规模的增大而增大,其中受家庭规模经济效应影响,COD、BOD的排放强度呈现出较为明显的边际递减规律,而TN、Tp主要受家庭居民个体因素影响较大；由于家庭污染排放与不同类型的家庭之间存在某种特定关系,以参照家庭为基准,构建污染等效因子,为估算不同地区家庭生活污染排放提供了一种简便方法。 /(6/)以氮素在家庭体系中的流动为主线,建立氮素流动模型框架,根据研究调查和文献资料来获取各个流通环节氮素的输入输出参数,设计了几套发展的情景方案,进行模型模拟。情景分析表明：食物消费结构对氮素的输出量有很大的影响,在一定社会经济条件下,家庭体系的氮素输出量取决于食物氮的输入量；粪尿氮还田率、污水处理率和氮去除率三种措施对减少氮素排入水体的敏感度不同,将粪尿还田率提高10个百分点,人均排入水体氮量将降低11.65/%；将污水处理率提高10个百分点,食物氮排入水体的比例将降低3/%；将氮去除率提高10个百分点,人均排入水体氮量也将降低12.14/%。进而对提出转变消费观念,优化食物消费结构,提高氮素的循环利用,提高污水处理基础设施能力,加大脱氮处理技术的研发,制定相关政策,调控养分流动的流向的中国食物链氮素管理策略。 With the growing of urbanization, food consumption structure of China changes significantly, consequently the change of nitrogen flow model has led to tremendous pressure of ecological environment and serious pollution problems in urban regions. Therefore, nitrogen flow characteristics were analyzed useing the method of material flow analysis, analyzing the statistical data, survey data, experiment data and literatures. Main research results were shown as follows. Food consumption is one of the important processes of household metabolism, contributing to the cause of resource consumption and pollution emission. The trend of urban food-nitrogen consumption from 1981 to 2007 based on national statistical data was analyzed. The results showed that, urban food-nitrogen consumption per capita underwent the multiple-periodic change of rise first then fall finally rise again. With the rapid development of economy and urbanization, food-nitrogen consumption per capita will be increasing continuously and has not yet reach a stable level. In order to estimate the nitrogen loss discharged into domestic sewage, analytical study on the Chinese cuisine by simulation test method was introduced. The results showed that there were significant differences among the nitrogen loss of different kind of food discharged into domestic sewage. The proportion of nitrogen loss of rice, vegetable, meat, egg and aquatic products was 16.00/%.17.00/%.5.00/%.7.00/%. All these provided the theoretical guidance for making pollutants producing coefficient and optimizing on the process for the Chinese cuisine. Nested design was performed in order to execute experiment on excretion of human, in which mainly related factors affecting the excretion coefficients were examined. The results showed that excretion coefficients of TN,TP were higher than that of COD,BOD5, suggesting that the absorption rates of N, P were lower, and there would be more excretion of TN and TP than that of COD and BOD5 in human excreta when equivalent amount of pollutants were .ingested. Except for COD excretion coefficient, excretion coefficients in female group were higher than those in male group with significant difference /(P<0.05/), possibly related to gender differences in weight, digestive ability and physical output. Besides, dietary pattern and food arrangement were also important factors affecting excretion coefficient, possibly associated with the levels and existing forms of COD, BOD5, TP, TN in different kinds of food. Therefore, environmental problems induced by the change of dietary pattern should be paid much attention to. The metabolic pathway of nutrients and regulation mechanism of trace elements and exogenous enzymes in different foods in human metabolism should be further studied. The effect of N excreteion for age and BMI of human excreta was investigated. The excretion rate of N element found in urine was 9.16 g//cap//day and 1.33 g//cap//day in faeces. As age increased, it presented with progressive tendency for the N excretetion both in urine and faeces. When BMI gone up, it also led to the increase on N excretetion in urine, but no significant variation was found between the results for human faeces at different BMI groups. The model gave a comprehensive consideration of age, BMI and their interaction effect. Taking urban household as the research object, relationships between household scale, household structure and emission characteristics of domestic sewage were investigated. The results showed that emission characteristics of domestic sewage were closely related to household scale and household structure. As household scale increased, it presented with progressive tendency for pollutant indicators of COD and BOD, due to scale economic effect. While the results of TN,TP were mainly influenced by individual factors. According to some special relationships between pollutants emission and household type, a simple approach of equivalence factor in reference household was proposed for estimating wastewater discharge in different urban household. Based on the systematical analysis of the main factors which affects nitrogen flow in urban household, a model frame of nitrogen flow was established and nitrogen flow in the different scenarios were analyzed. The results showed that food consumption structure was a important factor affecting nitrogen output. Return field rate, sewage treatment rateand nitrogen removal efficiency had different contribution to nitrogen loss discharged into water environment. When return field rate, sewage treatment rate and nitrogen removal efficiency increased by 10 percentage points respectively, nitrogen discharged into water environment would decreases by 11.65/%,3/%,12.14/%.

关 键 词： 氮素流动 城镇化 水体污染

分 类 号： [X50]

领　　域： [环境科学与工程]