生物覆盖层基质对垃圾填埋场甲烷氧化的影响

生物覆盖层甲烷氧化是填埋场甲烷减排的重要途径,覆盖层基质性能对其甲烷氧化能力影响较大。选用≤1mm堆肥物（1#基质）、≤1mm堆肥物＋陶粒（2^#基质）、≤1mm堆肥物＋陶粒（3#基质）、1～2mm堆肥物（4#基质）、2～3．2mm堆肥物（5#基质）等5种不同类型的生物覆盖层基质,在实验室内模拟研究填埋场生物覆盖层的甲烷生物氧化状况,旨在为筛选垃圾填埋场甲烷高效氧化的生物覆盖材料提供科学依据。试验结果表明：粒径对基质氧气传输能力的影响不明显;不同基质的甲烷氧化能力存在显著差异,纯堆肥物基质（1#、4#和5#基质）几乎没有甲烷氧化能力,堆肥物＋陶粒（1：1（v：v）的复合基质（2#、3#基质）的甲烷氧化效率高达100％。堆肥物一陶粒复合基质为甲烷氧化细菌营造了良好的环境,改善了生物覆盖层内的气体传输性能,是一种适宜的填埋场生物覆盖层基质材料。     

Metabolic and Environmental Control on Methane Emission from Soils: Mechanistic Studies of Mesotrophic Fen in West Siberia

The biological mechanisms regulating methane emission fromnatural wetlands are the focus of this article. A novel techniqueprovides estimates of the distribution of CH₄ sources withinan undisturbed soil profile by recording the transient gasdynamics after soil enclosure by deep (50 cm) chamber. Thecombined use of conventional surface and soil chambers across a200-m fen transect allowed us to relate the observed methaneemission to its instant generation and uptake. Surprisingly, themethane generation was relatively constant (9–12 mg CH₄-C hr^-1 m^-2) and highly variable net emission (0.2–20 mg CH₄-C hr^-1 m^-2) was closely correlated (r = –0.809)with methane uptake. In laboratory incubations, CH₄ uptakefollowed Michaelis-Menten kinetics. Added chloride and nitrateirrespective of the cation's nature suppressed uptake as a strongnoncompetitive inhibitors (K _i 0.5 mM). The methaneformation turned out to be unstable and under anaerobicincubation, the formation of CH₄, CO₂ andH₂displayed sustained weekly oscillations. We conclude that effectsof environmental factors alone are not sufficient topredict the variation in emission, which depends also on metabolic control of respective soil organisms. The multitude ofsuch controls is dependent on diversity of respective soilorganisms and could be grouped into a limited number ofcategories considerably simplifying large-scale simulations.     

动物废弃物源甲烷排放量的初步估算与减缓技术选择

根据ＩＰＣＣ的国家温室气体排放清单编制指南，初步计算了中国动物废弃物源的甲烷排放量。２０年间，中国动物废弃物源的甲烷排放量增加了７５％，１９９０年的甲烷排放量为１．１９８Ｔｇ，占全球的１０％左右。并提出发展沼气池、贮留池不仅能减少甲烷排放，而且能产生其它的环境效益和经济效益。     

Methane emission from rice paddy soils, aerotolerance of methanogens and global thermal warming

In vitro methane emissions from different rice paddy soils and algal mats were studied under anoxic and atmospheric conditions. Methane production from rice paddy soils cultivating different strains of rice was found to be appreciable under anoxic conditions, but considerably reduced under atmospheric conditions, and dependent on rice cultivars (strains). A contradictory result was obtained with a Gobindabhog cultivated rice field (a strain of rice with aroma), where methane yield under anoxic was greater than that under atmospheric conditions. The results indicated aerotolerance of methanogens or the possible existence of microaerophilic methanogens. The results from algal mats corroborated these findings.Methane has been considered to be an important greenhouse gas contributing significantly to global thermal warming (GTW). Flooded rice paddy fields have been considered to be a most prominent source of abiogenic methane emission, though considerable uncertainty exists regarding the true estimates of methane emission. Factors affecting methane emission and its abatement have been examined. In spite of increasing methane emission, rice cultivation leads to enormous utilization of the green house gas carbon dioxide and release of oxygen to the atmosphere. Thus, the contribution of methane to GTW (from rice paddy cultivation) is more than compensated by carbon dioxide absorption.Appropriate steps have been suggested for the reduction of methane emissions, the most important of which is the restoration of methane sinks.     

风帽在准好氧填埋的应用及对填埋初期的影响

首次将风帽应用于准好氧填埋,以2 m×1 m×2 m的准好氧模拟箱为对象,考察了风帽对准好氧填埋环境形成过程的影响,比较了不同风速条件下二氧化碳和甲烷的浓度变化,并对风帽应用于准好氧填埋的作用原理进行了分析,以期为设计和优化准好氧填埋结构提供参考.结果表明,风帽可以加快准好氧环境的形成,将传统的准好氧环境的形成期由常规的50 d以上提前到40 d左右.通过比较风帽先拆后装二氧化碳和甲烷的浓度变化,表明风帽可以促进甲烷向二氧化碳的转化,减少甲烷的排放.卸下风帽后二氧化碳的浓度由最初的16.67%降为15.88%,甲烷从6.14%增大到16.12%;装上后二氧化碳的浓度增至19.18%,甲烷降为10.05%.考察了风速为2.0、3.5、5.0、6.5、8.0 m/s 5种条件下导气管出口处的甲烷排放情况,表明风速可以加强风帽的作用,有利于甲烷的减排,当风速增至8 m/s时,甲烷浓度由最初的15%以上降为5%以下.     

地面抽采煤层气环境影响和管理对策探讨

随着我国一系列鼓励煤层气开发政策、规划的实施,区域煤层气规模化和商业化开发将逐步展开.煤层气开发环境问题与常规天然气相比有其特殊性,主要表现为井网密度大、疏水降压排采和加压集输引发的特殊环境问题.井网密度大则对地表生态环境的影响大;煤层排水是煤层气开发区别于常规油气资源开发最主要的环境问题;加压集输和井网密度大增加动力设备,影响声环境质量和生态环境质量等.针对煤层气开发环境问题的特殊性,提出煤层气开发应以水平井为主减少地表扰动.不同水文地质条件煤层排水水质不同,我国为缺水国家,煤层排水如果为淡水,应考虑综合利用;如果为高矿化度水应考虑适当处理回注地下.     

造纸污泥与味精废液联合厌氧消化产甲烷性能研究

采用造纸污泥与味精废液间歇式联合厌氧消化产沼气,通过设计总固体(TS)含量、碳氮比(C/N)和接种量等不同的工艺参数,研究了不同工艺条件下各反应器的产甲烷性能.试验结果表明:在中温(37±2)℃条件下,TS含量对系统累积产气量的影响较大,各反应器的累积产气量随TS含量的增加而增加;各反应器的单位质量挥发性固体(VS)累积产气率和TS、VS的去除率随TS含量增加而降低;在TS含量为10%的3组反应器中,造纸污泥:味精废液(w/w)=10∶1的反应器产气效果优于造纸污泥∶味精废液(w/w)=25∶1和70∶1两组处理,这与前者在消化过程中pH值下降最多、酸化能力最强有关;联合厌氧消化累积甲烷产量最大值为5482mL(TS含量为10%,造纸污泥∶味精废液(w/w)=10∶1),单位质量VS甲烷产率最大值为362mL.g-1(TS含量为3%,造纸污泥∶味精废液(w/w)=11∶1),可见这两种工业废物联合厌氧消化具有巨大的产甲烷潜力.     

异波折板厌氧废水处理技术研究

设计异波折板复合厌氧反应器,进行为期12个月的生活污水处理试验研究。试验结果表明,在温度处于(25±2)℃条件下,反应器的最佳水力停留时间(HRT)为6h。此时所对应的COD、TN、TP去除率分别为76.95%、36.56%、39.28%;最适厌氧污泥区容积百分比为45%～65%;最适进水COD浓度为150～800mg/L。控制HRT为6h,查明温度降至(7±1)℃时所对应的COD、TN、TP分别为63.53%、20.28%、22.35%;最大比甲烷生产率降至1.95mL(/gVSS·h)。此研究结果表明在北方地区低温度条件下应用该技术处理低浓度生活污水可行。基于试验结果,阐明了此厌氧生物处理技术处理低浓度生活污水的高效机理在于异波折板复合厌氧反应器具有高效传质和双层分阶段多生物相的特点。     

Effects of support acidity on the reaction mechanisms of selective catalytic reduction of NO by CH4 in excess oxygen

The reaction mechanisms of selective catalytic reduction (SCR) of nitric oxide (NO) by methane (CH₄) over solid superacid-based catalysts were proposed and testified by DRIFTS studies on transient reaction as well as by kinetic models. Catalysts derived from different supports would lead to different reaction pathways, and the acidity of solid superacid played an important role in determining the reaction mechanisms and the catalytic activities. Higher ratios of Br?nsted acid sites to Lewis acid sites would lead to stronger oxidation of methane and then could facilitate the step of methane activation. Strong Br?nsted acid sites would not necessarily lead to better catalytic performance, however, since the active surface NO_y species and the corresponding reaction routes were determined by the overall acidity strength of the support. The reaction routes where NO₂ moiety was engaged as an important intermediate involved moderate oxidation of methane, the rate of which could determine the overall activity. The reaction involving NO moiety was likely to be determined by the step of reduction of NO. Therefore, to enhance the SCR activity of solid superacid catalysts, reactions between appropriate couples of active NO_y species and activated hydrocarbon intermediates should be realized by modification of the support acidity.     

Methane emissions during storage of di erent treatments from cattle manure in Tianjin

Many studies on methane emissions from animal manure have revealed that animal manure is a major source of methane emissions to the atmosphere that can have negative consequences for people, animals and environment. In general, the release of methane can be influenced by the type of feed taken by animals, temperature, manure characteristics and so on. This study aimed at quantifying and comparing methane release from dairy manure with di erent piling treatments. Four treatments were designed including manure piling height 30, 45, 60 cm and adding 6 cm manure every day until the piling height was 60 cm. Static chamber method and gas chromatography were adopted to measure the methane emissions from April to June in 2009. Methane emission rates of all four manure treatments were low in the first week and then increased sharply until reaching the peak values. Subsequently, all the methane emission rates decreased and fluctuated within the steady range till the end of the experiment. Wilcoxon nonparametric tests analysis indicated that methane emission rate was greatly influenced by manure piling height and manner. There were no significant relationships between methane emission rates and the temperatures of ambience and heap. However, regression analysis showed that the quadratic equations were found between emission rates of all treatments and the gas temperature in the barrels.