提高碳汇潜力：量化树种和造林模式对碳储量的影响

全球气候变化背景下,造林再造林固定的碳可以抵消温室气体减限排量。通过造林再造林增加森林面积可以增加林业碳汇,在土地面积有限的情况下,提高造林质量——在有限的造林面积上固定更多的碳是十分必要的。树种和造林模式的选择是增加森林生态系统碳汇的重要管理决策。文章综述了树种和造林模式对生态系统的碳储量的影响。树种从生物量的积累,凋落物和土壤碳储存,以及木材密度、碳贮存量等几个方面探讨其对生态系统碳库的影响。混交林能充分利用立地条件、改善树木营养状况,并且可以减少病虫害和森林火灾。同时分析了我国在森林经营方面存在的问题和改善途径,以期为该领域的研究提供参考。     

Impact of bioenergy crops in a carbon dioxide constrained world: an application of the MiniCAM energy-agriculture and land use model

In the coming century, modern bioenergy crops have the potential to play a crucial role in the global energy mix, especially under policies to reduce carbon dioxide emissions as proposed by many in the international community. Previous studies have not fully addressed many of the dynamic interactions and effects of a policy-induced expansion of bioenergy crop production, particularly on crop yields and human food demand. This study combines an updated agriculture and land use (AgLU) model with a well-developed energy-economic model to provide an analysis of the effects of bioenergy crops on energy, agricultural and land use systems. The results indicate that carbon dioxide mitigation policies can stimulate a large production of bioenergy crops, dependent on the level of the policy. This production of bioenergy crops can lead to several impacts on the agriculture and land use system: decreases in forestland and unmanaged land, decreases in the average yield of food crops, increases in the prices of food crops, and decreases in the level of human demand of calories.

Carbon neutral Biggar: calculating the community carbon footprint and renewable energy options for footprint reduction

The objective of this research was to develop a community carbon footprint model that could be used to assess the size and major components of a community’s carbon dioxide (CO₂) emissions. The town of Biggar aims to become Scotland’s first carbon neutral town. As expected for this rural community, car transport accounted for nearly half of the CO₂ emissions, with natural gas and electricity consumption resulting in a further 24% and 12% of total emissions, respectively, and air travel being the last major component at 10% of emissions. An assessment was also made of the wind and solar resources of the town. One large wind turbine would provide the town’s electricity, while three to four turbines would be needed to offset all CO₂ emissions. In contrast, offsetting by tree planting would require in the region of 2,000 ha of trees.

Monitoring the effect of restoration measures in Indonesian peatlands by radar satellite imagery

In the context of the ongoing climate change discussions the importance of peatlands as carbon stores is increasingly recognised in the public. Drainage, deforestation and peat fires are the main reasons for the release of huge amounts of carbon from peatlands. Successful restoration of degraded tropical peatlands is of high interest due to their huge carbon store and sequestration potential. The blocking of drainage canals by dam building has become one of the most important measures to restore the hydrology and the ecological function of the peat domes. This study investigates the capability of using multitemporal radar remote sensing imagery for monitoring the hydrological effects of these measures. The study area is the former Mega Rice Project area in Central Kalimantan, Indonesia, where peat drainage and forest degradation is especially intense. Restoration measures started in July 2004 by building 30 large dams until June 2008. We applied change detection analysis with more than 80 ENVISAT ASAR and ALOS PALSAR images, acquired between 2004 and 2009. Radar signal increases of up to 1.36 dB show that high frequency multitemporal radar satellite imagery can be used to detect an increase in peat soil moisture after dam construction, especially in deforested areas with a high density of dams. Furthermore, a strong correlation between cross-polarised radar backscatter coefficients and groundwater levels above -50 cm was found. Monitoring peatland rewetting and quantifying groundwater level variations is important information for vegetation re-establishment, fire hazard warning and making carbon emission mitigation tradable under the voluntary carbon market or REDD (Reducing Emissions from Deforestation and Degradation) mechanism.     

Identifying priority areas for ecosystem service management in South African grasslands

Grasslands provide many ecosystem services required to support human well-being and are home to a diverse fauna and flora. Degradation of grasslands due to agriculture and other forms of land use threaten biodiversity and ecosystem services. Various efforts are underway around the world to stem these declines. The Grassland Programme in South Africa is one such initiative and is aimed at safeguarding both biodiversity and ecosystem services. As part of this developing programme, we identified spatial priority areas for ecosystem services, tested the effect of different target levels of ecosystem services used to identify priority areas, and evaluated whether biodiversity priority areas can be aligned with those for ecosystem services. We mapped five ecosystem services (below ground carbon storage, surface water supply, water flow regulation, soil accumulation and soil retention) and identified priority areas for individual ecosystem services and for all five services at the scale of quaternary catchments. Planning for individual ecosystem services showed that, depending on the ecosystem service of interest, between 4% and 13% of the grassland biome was required to conserve at least 40% of the soil and water services. Thirty-four percent of the biome was needed to conserve 40% of the carbon service in the grassland. Priority areas identified for five ecosystem services under three target levels (20%, 40%, 60% of the total amount) showed that between 17% and 56% of the grassland biome was needed to conserve these ecosystem services. There was moderate to high overlap between priority areas selected for ecosystem services and already-identified terrestrial and freshwater biodiversity priority areas. This level of overlap coupled with low irreplaceability values obtained when planning for individual ecosystem services makes it possible to combine biodiversity and ecosystem services in one plan using systematic conservation planning.     

Ligand-assisted degradation of carbon tetrachloride by microscale zero-valent iron

Degradation of carbon tetrachloride (CT) by microscale zero-valent iron (ZVI) was investigated in batch systems with or without organic ligands (ethylenediaminetetraacetic acid (EDTA), citric acid, tartaric acid, malic acid and oxalic acid) at pHs from 3.5 to 7.5. The results demonstrated that at 25°C, the dechlorination of CT by microscale ZVI is slow in the absence of organic ligands, with a pseudo-first-order rate constant of 0.0217 h(-1) at pH 3.5 and being further dropped to 0.0052 h(-1) at pH 7.5. However, addition of organic ligands significantly enhanced the rates and the extents of CT removal, as indicated by the rate constant increases of 39, 31, 32, 28 and 18 times in the presence of EDTA, citric acid, tartaric acid, malic acid and oxalic acid, respectively, at pH 3.5 and 25°C. The effect of EDTA was most significant; the dechlorination of CT at an initial concentration of 20 mg l(-1) increased from 16.3% (no ligands) to 89.1% (with EDTA) at the end of 8h reaction. The enhanced CT degradation in the presence of organic ligands was primarily attributed to the elimination of a surface passivation layer of Fe(III) (hydr)oxides on the microscale ZVI through chelating of organic ligands with Fe(III), which maintained the exposure of active sites on ZVI surface to CT.     

碳纳米管在环境样品前处理中的研究现状及应用进展

纳米碳管是一种新型的纳米材料,其独特的分子结构和性能引起了人们的广泛关注。本文重点评述了纳米碳管在环境样品前处理特别是在固相萃取和固相微萃取方面的研究现状与应用进展,并对纳米碳管的应用前景进行了展望。     

Impact of closed-loop network configurations on carbon footprints: A case study in copiers

Growing concerns about the environment make a supply chains’ eco-footprint increasingly important, presuming that footprints are a more effective (policy) instrument than those currently in use. The eco-footprint comprises all kinds of environmental impact, but often is narrowed down to one aspect; e.g. the carbon footprint, material footprint, the water footprint, and so on. Although returns give rise to an additional goods flow from customers back to producers, it usually improves the eco-footprint due to the substitution effect. The reverse channel supplies high quality (recovered) products, components and materials to the forward channel thereby reducing the need for virgin sourcing and production. We refer to this as closed-loop recovery, as opposed to recovery for cascade markets which lacks substitution. To maximize substitution, the recovered items must re-enter the original supply chain. The feasibility of closed-loop recovery depends partly on the geographical proximity of forward and reverse facilities. We develop a decision framework for optimizing closed loop network configurations, i.e. the combined disposition and location–transport decision. We apply the framework to a single case study concerning one type of footprint (namely the carbon footprint) of a copier (closed-loop) supply chain. The main implication is that a regional network, with combined forward and reverse facilities per continent, proves most efficient and most robust in view of uncertain exogenous variables, but only when a full set of closed-loop options is available (including closed-loop recycling). As an embedded case, main contribution value of it lies in the discovery of a new phenomenon with generic implications; namely that not only the closed-loop supply chains footprint strongly depends on the substitution effect, but that in turn the feasibility of closed-loop recovery options depends heavily on the network design. From delineations of the study we derive issues for further research.     

Modelling forest management within a global vegetation model—Part 2: Model validation from a tree to a continental scale

The construction of a new forest management module (FMM) within the ORCHIDEE global vegetation model (GVM) allows a realistic simulation of biomass changes during the life cycle of a forest, which makes many biomass datasets suitable as validation data for the coupled ORCHIDEE-FM GVM. This study uses three datasets to validate ORCHIDEE-FM at different temporal and spatial scales: permanent monitoring plots, yield tables, and the French national inventory data. The last dataset has sufficient geospatial coverage to allow a novel type of validation: inventory plots can be used to produce continuous maps that can be compared to continuous simulations for regional trends in standing volumes and volume increments. ORCHIDEE-FM performs better than simple statistical models for stand-level variables, which include tree density, basal area, standing volume, average circumference and height, when management intensity and initial conditions are known: model efficiency is improved by an average of 0.11, and its average bias does not exceed 25%. The performance of the model is less satisfying for tree-level variables, including extreme circumferences, tree circumference distribution and competition indices, or when management and initial conditions are unknown. At the regional level, when climate forcing is accurate for precipitation, ORCHIDEE-FM is able to reproduce most productivity patterns in France, such as the local lows of needleleaves in the Parisian basin and of broadleaves in south-central France. The simulation of water stress effects on biomass in the Mediterranean region, however, remains problematic, as does the simulation of the wood increment for coniferous trees. These pitfalls pertain to the general ORCHIDEE model rather than to the FMM. Overall, with an average bias seldom exceeding 40%, the performance of ORCHIDEE-FM is deemed reliable to use it as a new modelling tool in the study of the effects of interactions between forest management and climate on biomass stocks of forests across a range of scales from plot to country.     

CO2 capture and storage from a bioethanol plant: Carbon and energy footprint and economic assessment

Biomass energy and carbon capture and storage (BECCS) can lead to a net removal of atmospheric CO₂. This paper investigates environmental and economic performances of CCS retrofit applied to two mid-sized refineries producing ethanol from sugar beets. Located in the Region Centre France, each refinery has two major CO₂ sources: fermentation and cogeneration units. “carbon and energy footprint” (CEF) and “discounted cash flow” (DCF) analyses show that such a project could be a good opportunity for CCS early deployment. CCS retrofit on fermentation only with natural gas fired cogeneration improves CEF of ethanol production and consumption by 60% without increasing much the non renewable energy consumption. CCS retrofit on fermentation and natural gas fired cogeneration is even more appealing by decreasing of 115% CO₂ emissions, while increasing non renewable energy consumption by 40%. DCF shows that significant project rates of return can be achieved for such small sources if both a stringent carbon policy and direct subsidies corresponding to 25% of necessary investment are assumed. We also underlined that transport and storage cost dilution can be realistically achieved by clustering emissions from various plants located in the same area. On a single plant basis, increasing ethanol production can also produce strong economies of scale.