湿地甲烷的产生、氧化及排放通量研究进展

甲烷研究已倍受科学界关注,不仅由于其对全球变暖的贡献仅次于二氧化碳,贡献率达25%,还因为单分子甲烷的增值潜势是二氧化碳的15~30倍.湿地是甲烷的重要来源,估计湿地生态系统对全球甲烷排放的贡献率约为20%,即为100~200Tg a?1.湿地甲烷在厌氧条件下产生,在土壤氧化层以及根际中部分氧化,然后通过土壤、水体和植物体排放到大气中去.就近10a来湿地甲烷产生、氧化、传输过程及其影响因素等的研究进展进行了综述.产甲烷菌的研究主要集中在其对环境因子的生理生态和分子生物学,尤其集中在稻田产甲烷菌的研究上,因此在深度和广度上都有待突破.产甲烷过程是一个复杂的生化过程,要对甲烷排放量估计、甲烷排放动态研究以及在甲烷排放建模等方面取得进展,必需在甲烷产生机制上进行突破.甲烷氧化菌的研究集中于菌群对环境的适应以及其自身氧化能力上,应用研究还不是很深入.甲烷氧化过程的研究已经有了一定的深度,但氧化过程具体机理的研究还有待进一步深入,这需要分子生物学以及基因组学等多学科的交叉.甲烷传输过程是研究甲烷排放动态的基础,目前相关研究较少,国内有关研究主要集中在稻田研究上,对高寒湿地的研究则几乎是空白.湿地甲烷通量的研究是目前温室气体研究的热点问题,但主要解决的问题是大气中甲烷气体浓度增加与湿地甲烷通量的关系.湿地甲烷通量是由多种因素决定的,对影响湿地甲烷通量的因素的研究相当丰富,特别是近年来对生物因素的关注.由于学科的发展,近10a在这方面的研究较之过去更为全面和系统.图1表1参68     

An innovative wood-chip-framework substrate used as slow-release carbon source to treat high-strength nitrogen wastewater

Removal of nitrogen in wastewater before discharge into receiving water courses is an important consideration in treatment systems. However, nitrogen removal efficiency is usually limited due to the low carbon/nitrogen (C/N) ratio. A common solution is to add external carbon sources, but amount of liquid is difficult to determine. Therefore, a combined wood-chip-framework substrate (with wood, slag and gravel) as a slow-release carbon source was constructed in baffled subsurface-flow constructed wetlands to overcome the problem. Results show that the removal rate of ammonia nitrogen (NH₄⁺-N), total nitrogen (TN) and chemical oxygen demand (COD) could reach 37.5%–85%, 57.4%–86%, 32.4%–78%, respectively, indicating the combined substrate could diffuse sufficient oxygen for the nitrification process (slag and gravel zone) and provide carbon source for denitrification process (wood-chip zone). The nitrification and denitrification were determined according to the location of slag/gravel and wood-chip, respectively. Nitrogen removal was efficient at the steady phase before a shock loading using slag-wood-gravel combined substrate because of nitrification–denitrification process, while nitrogen removal was efficient under a shock loading with wood-slag-gravel combined substrate because of ANAMMOX process. This study provides a new idea for wetland treatment of high-strength nitrogen wastewater.     

Nitrous oxide fluxes from the littoral zone of a lake on the Qinghai-Tibetan Plateau

Nitrous oxide (N(2)O) fluxes were measured in six littoral mirco-zones of Lake Huahu on Qinghai-Tibetan Plateau in the peak growing season of years of 2006 and 2007. The weighted mean N(2)O flux rate was 0.08 mg N m(-2) h(-1) (ranged from -0.07 to 0.35 mg N m(-2) h(-1)). The result was relatively high in the scope of N(2)O fluxes from boreal and temperate lakes. Emergent plant zones (Hippuris vulgaris and Glyceria maxima stands) recorded the highest N(2)O flux rate (0.11 ± 0.24 and 0.08 ± 0.17 mg N m(-2) h(-1), respectively). Non-vegetated lakeshore recorded the lowest N(2)O flux (0.03 ± 0.11 mg N m(-2) h(-1)), lower than that from the floating mat zone of Carex muliensis (0.05 ± 0.18 mg N m(-2) h(-1)), the floating-leaved plant zone of Polygonum amphibium (0.07 ± 0.11 mg N m(-2) h(-1)), and the wet meadow (0.07 ± 0.15 mg N m(-2) h(-1)). Standing water depths were important factors to explain such spatial variations in N(2)O fluxes. Significant temporal variations in N(2)O fluxes were also found. Such temporal variation in N(2)O flux in the littoral zone may be dependent on the interaction of water regime and thermal conditions, instead of the latter solely. These results showed the importance of the littoral zone of lake, especially the emergent plant zone, as a hotspot of N(2)O fluxes in such grazing meadows.     

Application of high OLR-fed aerobic granules for the treatment of low-strength wastewater：Performance, granule morphology and microbial community

Aerobic granules, pre-cultivated at the organic loading rate (OLR) of 3.0 kg COD/(m3 ·day), were used to treat low-strength wastewater in two sequencing batch reactors at low OLRs of 1.2 and 0.6 kg COD/(m3 ·day), respectively. Reactor performance, evolution of granule morphology, structure and microbial community at low OLRs under long-term operation (130 days) were investigated. Results showed that low OLRs did not cause significant damage to granule structure as a dominant granule morphology with size over 540 μm was maintained throughout the operation. Aerobic granules at sizes of about 750 μm were finally obtained at the low OLRs. The granule reactors operated at low OLRs demonstrated effective COD and ammonia removals (above 90%), smaller granule sizes and less biomass. The contents of extracellular polymeric substances in the granules were decreased while the ratios of exopolysaccharide/exoprotein were increased (above 1.0). The granules cultivated at the low OLRs showed a smoother surface and more compact structure than the seeded granules. A significant shift in microbial community was observed but the microbial diversity remained relatively stable. Confocal Laser Scanning Microscopy observation showed that the live cells were spread throughout the whole granule, while the dead cells were mainly concentrated in the outer layer of the granule, and the proteins, polysaccharides and lipids were mainly located in the central regime of the granule. In conclusion, granules cultivated at high OLRs show potential for treating low-strength organic wastewater steadily under long-term operation.     

环境管理政策的选择分析

环境管理政策的选择是一项复杂的决策过程 ,本文拟就环境管理政策的一般原理和基本过程进行阐述。一是对环境政策、环境管理政策的选择空间进行界定 ,对环境管理政策的选择进行分析 ;二是提出环境管理政策的选择原理和评判准则 ;三是对环境管理政策选择的可操作过程进行分析和论述。并由此得出 :环境管理政策的选择应在考虑具体的外部因素以及内部因素的基础上的政策择优 ,有效的环境管理政策的选择应该是给定约束条件下的管制手段、经济手段和劝说手段的恰当组合。     

森林土壤氧化（吸收）甲烷研究进展

甲烷是一种重要的温室气体,对全球气候变暖的贡献仅次于CO2,约为25%。大气甲烷可以被土壤中甲烷氧化细菌在有氧条件下吸收利用,陆地生态系统森林土壤氧化吸收甲烷的研究已有大量报道。甲烷氧化菌是以甲烷作为唯一的碳源和能源的一类细菌的总称。但森林土壤在全球甲烷核算中具有一定的不确定性,取决于产甲烷菌和甲烷氧化菌的相对活性。甲烷氧化菌的研究集中在环境对氧化能力的影响和自身氧化能力上。大气甲烷氧化过程为高氧化能力低亲力氧化,受到一些因子,如土壤温度、土壤通气状况、pH、氮肥等的影响,具体机理的研究还有待进一步深入。土壤通气状况受土壤质地与土壤水分影响,土地利用类型可能改变土壤容重、土壤结构和土壤水分,进而影响土壤甲烷氧化。植物可以通过自身对生境的作用或化感作用影响土壤甲烷氧化。土壤动物的研究则相对较少,目前排放清单中仅有白蚁是全球甲烷核算所包括的。从甲烷氧化菌的分类出发,对甲烷氧化菌氧化甲烷的机理、菌的生态分布及甲烷氧化的影响因素、时空异质性、观测方法等作出了综述,为正确认识和准确预测森林土壤在一定气候和土地利用类型条件下的甲烷氧化强度提供理论依据。     

不同放牧强度对高寒草甸生态系统呼吸的早期影响

放牧是高寒草甸一种重要的利用方式,对土壤理化性质和植被会产生重要影响,研究放牧对高寒草甸生态系统呼吸的影响对估算碳交换和制定合理放牧政策具有重要意义.利用静态箱-气象色谱法,于2012年8月到2013年7月在青藏高原东缘高寒草甸对轻度、中度和重度3种放牧强度下的生态系统呼吸进行每月至少一次的连续观测,以估算高寒草甸生态系统呼吸,并探讨放牧强度对生态系统呼吸的作用.结果显示:轻度、中度和重度放牧条件下,年均生态系统呼吸(以C计)分别为226.33±62.30、213.63±53.22和215.15±53.19 mg m~(-2) h~(-1),三者之间无显著差异(P0.05);在生长季生态系统呼吸分别为367.97±47.86、324.62±44.95和348.37±43.10 mg m~(-2) h~(-1),在非生长季生态系统呼吸分别为105.81±22.13、96.55±14.69和110.61±16.89 mg m~(-2) h~(-1),在不同放牧强度下生态系统呼吸均表现出明显的季节特征,但在相同季节不同放牧强度间生态系统呼吸差异不显著;月累积降水量与生态系统呼吸呈显著正相关关系;该区域放牧地生态系统平均年累积呼吸为472.63 g m~(-2) h~(-1).本研究表明,在试验初期不同放牧强度对生态系统呼吸无显著作用.     

Estimation of the longitudinal dispersion coefficient using a two-zone model in a channel partially covered with artificial emergent vegetation

Environmental Fluid Mechanics - Understanding scalar transport in solvents is important in chemical engineering, pollution control, and water remediation, where the longitudinal dispersion...     

Evaluating the hydrodynamics of a round jet in a vegetated crossflow through large eddy simulation

Environmental Fluid Mechanics - Vegetation plays an important role on the turbulence structures of the effluent spreading in an open channel, which are insufficiently studied. This paper employs a...     

池州的生态旅游业

本文简要地介绍了贵池生态旅游的几地性,分析了池州地区发展生态旅游得天独厚的优势和条件,探讨了池州发展生态旅游业的对策,提出了发展生态旅游业是池州可持续发展之路。