Progress and opportunities for monitoring greenhouse gases fluxes in Mexican ecosystems: the MexFlux network

Understanding ecosystem processes from a functional point of view is essential to study relationships among climate variability, biogeochemical cycles, and surface-atmosphere interactions. Increasingly during the last decades, the eddy covariance (EC) method has been applied in terrestrial, marine and urban ecosystems to quantify fluxes of greenhouse gases (e.g., CO₂, H₂O) and energy (e.g., sensible and latent heat). Networks of EC systems have been established in different regions and have provided scientific information that has been used for designing environmental and adaptation policies. In this context, this article outlines the conceptual and technical framework for the establishment of an EC regional network (i.e., MexFlux) to measure the surface-atmosphere exchange of heat and greenhouse gases in Mexico. The goal of the network is to improve our understanding of how climate variability and environmental change influence the dynamics of Mexican ecosystems. First, we discuss the relevance of CO₂ and water vapor exchange between terrestrial ecosystems and the atmosphere. Second, we briefly describe the EC basis and present examples of measurements in terrestrial and urban ecosystems of Mexico. Finally, we describe the conceptual and operational goals at short-, medium-, and long-term scales for continuity of the MexFlux network.     

火山口湖温室气体释放规模研究

火山口湖是地球上最为壮观的自然地貌之一。作为连接地表系统和地球深部岩浆-水热系统的纽带, 火山口湖是探索火山系统内部地质作用的重要窗口, 也是地球深部碳循环的重要环节。本研究在全球火山湖温室气体排放研究的基础上, 对火山口湖、玛珥湖和火山-构造有关的湖泊CO₂排放数据进行了甄别与梳理, 对火山口湖和玛珥湖温室气体释放特征进行了初步探讨; 同时, 以我国长白山天池火山口湖为例, 初步估算了天池火山口湖温室气体的释放规模, 并就火山口湖温室气体释放研究进行了展望。初步研究结果表明, 火山口湖的CO₂释放规模和释放速率整体上高于玛珥湖和火山-构造湖。火山口湖CO₂释放规模明显受火山活动的影响, 对火山活动具有较高的灵敏度, 是不可忽视的CO₂重要来源。作为我国典型的火山口湖, 长白山天池通过水-气界面扩散向大气中输送的CO₂规模为3.44×10⁴t/a, 大量CO₂溶解于湖水中, 湖水中溶解的CO₂规模为1.96×10⁵t。结合以往研究, 初步估算整个长白山天池火山区通过湿脱气系统向大气中释放的CO₂约占整个火山区CO₂释放总量的28%。虽然本研究仅对我国长白山天池火山口湖温室气体排放规模进行了初步估算, 但是随着研究程度的不断深入、调查范围的不断扩大, 火山口湖温室气体排放规模将会越来越精细, 火山区温室气体碳排放研究也会越来越系统, 火山区碳循环的路径也将会越来越清晰。

     

Spaceborne remote sensing of greenhouse gas concentrations

Despite their primary contribution to climate change, there are still large uncertainties on the sources and sinks of the main greenhouse gases: carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). A better knowledge of these sources is necessary to understand the processes that control them and therefore to predict their variations. Indeed, large feedbacks between climate change and greenhouse gas fluxes are expected during the 21st century. Sources and sinks of these gases generate spatial and temporal gradients that can be measured either in situ or from space. One can then estimate the surface fluxes, either positive or negative, from concentration measurements through a so-called atmospheric inversion. Surface measurements are currently used to estimate the fluxes at continental scales. The high density of spaceborne observations allows potentially a much higher resolution. Several remote sensing techniques can be used to measure atmospheric concentration of greenhouse gases. These techniques have motivated the development of spaceborne instruments, some of them already in space and others under development. However, the accuracy of the current estimates is still not sufficient to improve our knowledge on the greenhouse gases sources and sinks. Rapid improvements are expected during the forthcoming years with a strong implication of the scientific community and the launch of dedicated instruments, optimized for the measurement of CO₂ and CH₄ concentrations.     

三峡水库香溪河支流水域温室气体排放通量观测

开展对香溪河支流水体的温室气体排放观测,有助于增加对三峡水库支流温室气体排放情况的了解以及水华对温室气体排放的影响.研究采用静态箱-气相色谱法,于2009年10月至2010年10月先后11次开展对香溪河支流水体3种温室气体(二氧化碳、甲烷、氧化亚氮)排放强度的观测,结果表明:观测期间香溪河支流的二氧化碳平均排放通量约为76.52 mg/(m2·h),排放强度与水体中叶绿素a浓度呈显著负相关,支流水华期间,二氧化碳排放通量小于0,表现为对大气中二氧化碳的吸收;支流甲烷平均排放通量约为0.244 9 mg/(m2·h);氧化亚氮平均排放水平约为0.011 7 mg/(m2·h).通过将甲烷平均排放水平与三峡水库其它区域开展的研究结果进行对比表明:三峡水库的甲烷排放水平很低,明显不同于已有基于国外水库平均排放水平对三峡水库全区甲烷排放的估算结果.     

Effects of precipitation pulses on water and carbon dioxide fluxes in two semiarid ecosystems: measurement and modeling

Modeling of soil?Cwater, ?Cheat and ?Ccarbon (C) fluxes provides an important tool for predicting mass and energy transfers based on a hydraulic-, thermal- and C-mass balance approach. Model predictions were evaluated using measured data from two water-limited study sites, one pasture and one supporting an alfalfa crop, to indentify differences between these ecosystems. Soil water content, temperature, and evapotranspiration (ET) data were used to validate soil water dynamics components of a process-based numerical model. Soil surface CO₂ efflux estimates (i.e., fluxes from soil respiration) were also made to estimate soil CO₂ emissions. The results show that the Hydrus-1D numerical model can be parameterized to simulate the soil hydrodynamics and CO₂ fluxes measured at both locations. Rainfall and irrigation events triggering increases in plant root and microbial respiration rates were simulated to recreate observed pulsed CO₂ fluxes. There were distinct differences in ET and soil CO₂ effluxes between the ecosystems and watering events significantly modified the fluxes. Differences in potential evapotranspiration and soil texture could help explain these discrepancies. The results demonstrate that numerical modeling can be a useful tool for estimating soil surface fluxes in calibrated ecosystems when micrometeorological methods may not be suitable.     

Correlation between land-use change and greenhouse gas emissions in urban areas

Urban areas are the main sources of greenhouse gas (GHG) emissions. Previous studies have identified the effectiveness of better urban design on mitigating climate change and land-use patterns in cities as important factors in reducing GHG by local governments. However, studies documenting the link between land-use and GHG emissions are scant. Therefore, this study explores the driving forces of land-use change and GHG emission increments in urban areas and investigates their correlations. The study area, Xinzhuang, is a satellite city of Taipei that has rapidly urbanized in the past few decades. Twenty-one potential variables were selected to determine the driving forces of land-use change and GHG emission increments by binomial logistic regression based on the investigation data of national land use in 1996 and 2007. The correlation of land-use change and GHG increments was examined by Spearman rank-order analysis. Results of logistic regression analysis identified that population and its increasing density rate are main driving forces on both land-use change and GHG increments. The Spearman rank correlation matrix indicates that fluctuating urbanization level is significantly correlated with the increase of total GHG emissions, the emissions of residence, commerce, and transportation sectors in neighborhoods; and the emissions of residence and transportation sectors seem closely connected to current urbanization level. The findings suggest that relationships among land-use, urbanization, and GHG emissions in urban areas vary greatly according to residence and transportation characteristics. Land-based mitigation may provide the most viable mechanism for reducing GHG emissions through residence and transportation sectors.     

Biogeochemical cycles in tundra ecosystems in areas impacted by gas industry facilities

Data acquired by monitoring modern biogeochemical cycles in tundra ecosystems in zones impacted by facilities of the gas industry indicate the absence of any perceptible changes in the system surface water–bottom sediments–soil–plants and show that the emitted nitrogen oxides beneficially affect productivity of the lichens and the functioning of the tundra ecosystem as a whole.     

Comments on possible Miocene hominin footprints

Gierlinski et al. (2017) report on what they interpret to be Miocene hominin footprints near the seaside village of Trachilos in western Crete. We review the case made by the authors that these ichnites represent bona-fide footprints, and their conclusion that they were made by bipedal hominins. Gierlinski et al.'s study demonstrates a number of problems with data presentation, e.g. a) substrates corresponding to measured prints are not clearly specified, b) no explanation is given for how prints were identified when the authors' own criteria for print identification were not met, c) no consistent morphological detail among prints is provided that could identify them as originating from the same or a similar agent, or one with bilateral symmetry, d) alternative agents that could have produced the prints are not explored, e) no explanation is given as to how their multivariate analyses of print outlines deals with missing data and why it uses non-homologous landmarks, etc. The evidence they present, therefore, is insufficient to support their arguments and conclusions. We remain unconvinced the ichnites are bona-fide footprints, let alone hominin footprints, but discuss some of the criteria employed for distinguishing and recognizing an early hominin footprint.     

大庆市生态足迹计量分析

生态足迹计量分析是一种度量可持续发展程度的方法,通过测定当前生物生产性土地面积的量来评估人类对地球生态系统的影响.本文基于石油城市大庆的现状,对生态足迹进行了定量计算,从而分析出大庆市生态足迹的情况.结果表明:2004年大庆市的人均生态赤字为1.0424 hm2,表明大庆市的发展模式处于一种不可持续的状态,这与大庆市多年来经济迅速发展,而这种高速发展是以消耗大量的自然资源和能量来维持这一现状相吻合的.     

Assessment of greenhouse gas emissions from coal and natural gas thermal power plants using life cycle approach

The importance of mitigation of climate change due to greenhouse gas (GHG) emissions from various developmental and infrastructure projects has generated interest at global level to reduce environmental impacts. Life cycle assessment may be used as a tool to assess GHG emissions and subsequent environmental impacts resulting from electricity generation from thermal power plants. This study uses life cycle approach for assessing GHG emissions and their impacts due to natural gas combined cycle (NGCC) and imported coal thermal power plants using the IPCC 2001 and Eco-Indicator 99(H) methods in India for the first time. The total GHG emission from the NGCC thermal power plant was 584 g CO₂ eq/kWh electricity generation, whereas in case of imported coal, it was 1,127 g CO₂ eq/kWh electricity generation. This shows that imported coal has nearly ~2 times more impacts when compared to natural gas in terms of global warming potential and human health as disability-adjusted life years from climate change due to GHG emissions such as carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O).     

Application of in-seam directional drilling technology for gas drainage with benefits to gas outburst control and greenhouse gas reductions in Daning coal mine,China

Gas outburst disasters are becoming more serious as the underground coal mines become deeper in China, and a thick zone of deformed coal provides conditions favorable to coal and gas outbursts. The Daning coal mine’s main mining seam is the No. 3 coal seam with coal and gas outburst hazard, which often contains two normal coal sub-layers and one deformed sub-layer. Considering both the geological conditions of the coal seam and applications of the in-seam directional longhole drilling technology, a new schematic diagram of in-seam directional longholes for gas drainage is developed. The two borehole layout models of longwall panel and main entries for gas outburst disasters control have been successfully applied. The gas drainage rates of both models are >70 %, and the residual gas contents are both <8 m³/t, which can be considered that the gas outburst disasters were effectively controlled. To better guide gas drainage, gas drainage normal and failure modes have been obtained. Although in-seam directional longhole technology has been successfully applied for regional gas drainage with benefits to gas outburst control, there are also some problems that are detrimental to greenhouse gas reductions in gas drainage and gas utilization. The three main problems are air leakage failure in gas drainage, decreasing gas concentration and a low gas utilization ratio. To address the problems mentioned above, five improvements are suggested.     

四川盆地恐龙足迹化石研究综述

四川盆地的中生代陆相地层十分发育,盛产恐龙化石和恐龙足迹化石。自20世纪40年代在四川广元首次发现恐龙足迹化石以来,迄今四川盆地已命名的恐龙足迹化石共20属24种,超过中国现已发现的恐龙足迹化石种类(39属55种)的2/5,成为中国发现恐龙足迹化石种类最多的地区。四川盆地恐龙足迹化石具有时代最早、分布广泛、种类众多的特点。建议今后重点加强晚三叠世恐龙足迹化石的研究,深入开展早侏罗世恐龙足迹化石的研究。     

Private agri-food governance and greenhouse gas abatement: Constructing a corporate carbon economy

Private sector actors are playing an increasingly significant role in the definition and governance of ‘sustainable’ agri-food practices. Yet, to date little attention has been paid by social scientists to how greenhouse gas (GHG) emissions are addressed as part of private agri-food governance arrangements. This paper examines how private actors within agri-food supply chains respond to emerging pressure for measures to reduce GHG emissions from agriculture. Drawing upon the Anglo-Foucauldian governmentality literature, we introduce the notion of the corporate carbon economy to conceptualise the practical techniques that enable private agri-food actors to make GHG emissions thinkable and governable in the context of existing market, regulatory, and supply chain pressures. Using a case study of the Australian dairy industry, we argue that private agri-food actors utilise a range of techniques that enable them to respond to existing government environmental regulations, balance current market pressures with future supply chain requirements, and demonstrate improved eco-efficiency along food supply chains. These techniques – which include environmental self-assessment instruments, tools for measuring GHG emissions, and sustainability reporting – have little direct relevance to the ‘international climate regime’ of carbon trading, and carbon markets more broadly, yet individually and in combination they are crucial in enacting an alternative regime of GHG governance. In concluding, we contend that the growing use of sustainability metrics by international food companies is likely to have the most powerful implications for GHG governance in the agri-food sector, with potentially far-reaching consequences for how future action on climate change is rendered thinkable and practicable.     

Soil temperature and moisture controls on surface fluxes and profile concentrations of greenhouse gases in karst area in central part of Guizhou Province, southwest China

In order to better understand the spatiotemporal variations and interrelationships of greenhouse gases (GHG), monthly surface fluxes and profile concentrations of GHG (CO₂, N₂O and CH₄) in karst areas in the Guizhou Province, southwest China, were measured from June 2006 to May 2007. GHG fluxes showed high variability, with a range of 460.9?C1,281.2?mg?m^?2?h^?1 for CO₂, ?25.4 to 81.5???g?m^?2?h^?1 for N₂O and ?28.7 to ?274.9???g?m^?2?h^?1 for CH₄, but no obvious seasonal change trends of the fluxes existed. Profile concentrations of CO₂, N₂O and CH₄ varied between 0.5 and 31.5?mL?L^?1, 0.273 and 0.734, and 0.1 and 3.5???L?L^?1, respectively. In general, concentrations of CO₂ and N₂O increased with depth, while CH₄ had an inverse trend. However, in October, November and January, the reversal of depth patterns of GHG concentrations took place below 15?cm, close to the soil?Crock interface. The spatiotemporal distribution of CO₂ in soil profile was significantly positively correlated with that of N₂O (p?<?0.05?C0.01) and negatively correlated with that of CH₄ (p?<?0.01). The correlation analysis showed that soil temperature and moisture may be responsible for GHG dynamics in the soils, rather than the exchange of GHG between land and atmosphere.     

Gases in Taiwan mud volcanoes: Chemical composition,methane carbon isotopes,and gas fluxes

Mud volcanoes are important pathways for CH₄ emission from deep buried sediments; however, the importance of gas fluxes have hitherto been neglected in atmospheric source budget considerations. In this study, gas fluxes have been monitored to examine the stability of their chemical compositions and fluxes spatially, and stable C isotopic ratios of CH₄ were determined, for several mud volcanoes on land in Taiwan. The major gas components are CH₄ (>90%), “air” (i.e. N₂ + O₂ + Ar, 1–5%) and CO₂ (1–5%) and these associated gas fluxes varied slightly at different mud volcanoes in southwestern Taiwan. The Hsiao-kun-shui (HKS) mud volcano emits the highest CH₄ concentration (CH₄ > 97%). On the other hand, the Chung-lun mud volcano (CL) shows CO₂ up to 85%, and much lower CH₄ content (<37%). High CH₄ content (>90%) with low CO₂ (<0.2%) are detected in the mud volcano gases collected in eastern Taiwan. It is suggestive that these gases are mostly of thermogenic origin based on C₁ (methane)/C₂ (ethane) + C₃ (propane) and δ¹³C_CH4 results, with the exception of mud volcanoes situated along the Gu-ting-keng (GTK) anticline axis showing unique biogenic characteristics. Only small CH₄ concentration variations, <2%, were detected in four on-site short term field-monitoring experiments, at Yue-shi-jie A, B, Kun-shui-ping and Lo-shan A. Preliminary estimation of CH₄ emission fluxes for mud volcanoes on land in Taiwan fall in a range between 980 and 2010 tons annually. If soil diffusion were taken into account, the total amount of mud volcano CH₄ could contribute up to 10% of total natural CH₄ emissions in Taiwan.     

Lake District pioneers – the earliest footprints on land

New evidence reveals that the first arthropods colonized dry land over 450 million years ago, more than 20 million years before the appearance of vascular plants. Traditionally, it was thought that animals only emerged on to land after plants had become established, thus providing a plentiful new food source. The earliest known terrestrial trace fossils occur in volcanogenic sediments from the English Lake District. The trace fossils are thought to have been made on land by a small millipede-like creature. These rocks contain no other fossils.     

Estimating greenhouse gas emissions from open-cut coal mining: application to the Sydney Basin

A new site-specific (Tier 3) method has been developed to determine greenhouse gas emissions from open coal mining. The Tier 3 method presented here is based on extensive measurement of gas emissions from open-cut coal mines and the physics of gas desorption from coal. It was adopted by Australian National Greenhouse and Energy Reporting in 2009 and since 2012 formed the scientific basis for the Australian Government guidelines on calculating greenhouse gas emissions from open cut mines. The main strength of this method is its site-specific nature and accuracy, as well as its ability to be integrated with routine coal exploration programs. New concepts were produced for the model: a coal mine is regarded as a ‘gas reservoir,’ with coal seam gas being emitted from a ‘gas release zone’ that consists of sedimentary geological units (emission layers) above and below the base of the mine. The primary data required for the method are the in situ gas content and gas composition of the coal and carbonaceous rocks contained within the gas-release zone. These data are obtained through direct measurement of gas desorption from bore cores. To reduce gas drilling, a mine lease is compartmentalised into ‘gas zones’ of similar gas content and reservoir properties. The outputs of the method are emission density (the potential volume of gas emitted from mining site per unit area of the ground surface) and emission factor (the gas volume emitted per tonne of raw coal extracted). Owing to spatial variability and errors of measurement, the estimate of emissions is associated with uncertainty. A simple method of calculating uncertainty of emissions is presented in this work.     

水库水气界面温室气体通量监测方法综述

水库水体中的有机碳,经过水中微生物代谢分解,生成甲烷、二氧化碳等温室气体,通过扩散、气泡等方式,经由水气界面排向大气.目前国外对水库水气界面的温室气体通量监测已经发展了静态箱法、梯度法、倒置漏斗法、TDLAS法以及涡度相关法等.综述了以上监测方法的原理、应用、优缺点及适用范围,从水体、陆地和气候环境方面分析了影响水气界...