World emissions and economic growth: Application of non-parametric methods

The Environmental Kuznets Curve (EKC) hypothesises an inverse U-shaped relationship between a measure of environmental pollution and per capita income levels. In this study, we apply non-parametric estimation of local polynomial regression (local quadratic fitting) to allow more flexibility in local estimation. This study uses a larger and globally representative sample of many local and global pollutants and natural resources including Biological Oxygen Demand (BOD) emission, CO2 emission, CO2 damage, energy use, energy depletion, mineral depletion, improved water source, PM10, particulate emission damage, forest area and net forest depletion. Copyright © 2009 Inderscience Enterprises Ltd.

Investigating the link between carbon dioxide emissions and transport-related social exclusion in rural Northern Ireland

Carbon dioxide (CO2) is considered the most harmful of the greenhouse gases. Despite policy efforts, transport is the only sector experiencing an increase in the level of CO2 emissions and thereby possesses a major threat to sustainable development. In contrast, a reduced level of mobility has been associated with an increasing risk of being socially excluded. However, despite being the two key elements in transport policy, little effort has so far been made to investigate the links between CO2 emissions and social exclusion. This research contributes to this gap by analysing data from 157 weekly activity-travel diaries collected in rural Northern Ireland. CO2 emission levels were calculated using average speed models for different modes of transport. Regression analyses were then conducted to identify the socio-spatial patterns associated with these CO2 emissions, mode choice behaviour, and patterns of participation in activities. This research found that despite emitting a higher level of carbon dioxide, groups in rural areas possess the risk of being socially excluded due to their higher levels of mobility.

Performance analysis of solar desiccant-evaporative cooling for a commercial building under different Australian climates

This paper evaluates and compares the system performance of a solar desiccant-evaporative cooling (SDEC) system with a referenced conventional variable air volume (VAV) system for a typical office building in all 8 Australian capital cities. A simulation model of the building is developed using the whole building simulation software EnergyPlus. The performance indicators for the comparison are system coefficient of performance (COP), annual primary energy consumption, annual energy savings, and annual CO2 emissions reduction. The simulation results show that Darwin has the most apparent advantages for SDEC system applications with an annual energy savings of 557 GJ and CO2 emission reduction of 121 tonnes. The maximum system COP is 7. For other climate zones such as Canberra, Hobart and Melbourne, the SDEC system is not as energy efficient as the conventional VAV system.

The role of lakes in carbon cycling in boreal catchments

Lakes are an important component of ecosystem carbon cycle through both organic carbon sequestration and carbon dioxide and methane emissions, although they cover only a small fraction of the Earth's surface area. Lake sediments are considered to be one of rather perma-nent sinks of carbon in boreal regions and furthermore, freshwater ecosystems process large amounts of carbon originating from terrestrial sources. These carbon fluxes are highly uncer-tain especially in the changing climate. -- The present study provides a large-scale view on carbon sources and fluxes in boreal lakes situated in different landscapes. We present carbon concentrations in water, pools in lake se-diments, and carbon gas (CO2 and CH4) fluxes from lakes. The study is based on spatially extensive and randomly selected Nordic Lake Survey (NLS) database with 874 lakes. The large database allows the identification of the various factors (lake size, climate, and catchment land use) determining lake water carbon concentrations, pools and gas fluxes in different types of lakes along a latitudinal gradient from 60oN to 69oN. Lakes in different landscapes vary in their carbon quantity and quality. Carbon (C) content (total organic and inorganic carbon) in lakes is highest in agriculture and peatland dominated areas. In peatland rich areas organic carbon dominated in lakes but in agricultural areas both organic and inorganic C concentrations were high. Total inorganic carbon in the lake water was strongly dependent on the bedrock and soil quality in the catchment, especially in areas where human influence in the catchment is low. In inhabited areas both agriculture and habitation in the catchment increase lake TIC concentrations, since in the disturbed soils both weathering and leaching are presumably more efficient than in pristine areas. TOC concentrations in lakes were related to either catchment sources, mainly peatlands, or to retention in the upper watercourses. Retention as a regulator of the TOC concentrations dominated in southern Finland, whereas the peatland sources were important in northern Finland. The homogeneous land use in the north and the restricted catchment sources of TOC contribute to the close relationship between peatlands and the TOC concentrations in the northern lakes. In southern Finland the more favorable climate for degradation and the multiple sources of TOC in the mixed land use highlight the importance of retention. Carbon processing was intensive in the small lakes. Both CO2 emission and the Holocene C pool in sediments per square meter of the lake area were highest in the smallest lakes. How-ever, because the total area of the small lakes on the areal level is limited, the large lakes are important units in C processing in the landscape. Both CO2 and CH4 concentrations and emissions were high in eutrophic lakes. High availability of nutrients and the fresh organic matter enhance degradation in these lakes. Eutrophic lakes are often small and shallow, enabling high contact between the water column and the sediment. At the landscape level, the lakes in agricultural areas are often eutrophic due to fertile soils and fertilization of the catchments, and therefore they also showed the highest CO2 and CH4 concentrations. Export from the catchments and in-lake degradation were suggested to be equally important sources of CO2 and CH4 in fall when the lake water column was intensively mixed and the transport of sub-stances from the catchment was high due to the rainy season. In the stagnant periods, especially in the winter, in-lake degradation as a gas source was highlighted due to minimal mixing and limited transport of C from the catchment. The strong relationship between the annual CO2 level of lakes and the annual precipitation suggests that climate change can have a major impact on C cycling in the catchments. Increase in precipitation enhances DOC export from the catchments and leads to increasing greenhouse gas emissions from lakes. The total annual CO2 emission from Finnish lakes was estimated to be 1400 Gg C a-1. The total lake sediment C pool in Finland was estimated to be 0.62 Pg, giving an annual sink in Finnish lakes of 65 Gg C a-1.

Emissions from India's transport sector: Statewise synthesis

A decentralized emission inventories are prepared for road transport sector of India in order to design and implement suitable technologies and policies for appropriate mitigation measures. Globalization and liberalization policies of the government in 90's have increased the number of road vehicles nearly 92.6% from 1980-1981 to 2003-2004. These vehicles mainly consume non-renewable fossil fuels, and are a major contributor of green house gases, particularly CO2 emission. This paper focuses on the statewise road transport emissions (CO2, CH4, CO, N-x, N2O, SO2, PM and HC) using region specific mass emission factors for each type of vehicles. The country level emissions (CO2, CH4, CO, NOx, N2O, SO2 and NMVOC) are calculated for railways, shipping and airway, based on fuel types. In India, transport sector emits an estimated 258.10 Tg Of CO2, of which 94.5% was contributed by road transport (2003-2004). Among all the states and Union Territories, Maharashtra's contribution is the largest, 28.85 Tg (11.8%) Of CO2, followed by Tamil Nadu 26.41 Tg(10.8%), Gujarat 23.31 Tg(9.6%), Uttar Pradesh 17.42 Tg(7.1%), Rajasthan 15.17 Tg (6.22%) and, Karnataka 15.09 Tg (6.19%). These six states account for 51.8% of the CO2 emissions from road transport.

Analyzing changes in macro-level drivers of country-specific emissions : The role of consumption, technology and trade

Industrial ecology is an important field of sustainability science. It can be applied to study environmental problems in a policy relevant manner. Industrial ecology uses ecosystem analogy; it aims at closing the loop of materials and substances and at the same time reducing resource consumption and environmental emissions. Emissions from human activities are related to human interference in material cycles. Carbon (C), nitrogen (N) and phosphorus (P) are essential elements for all living organisms, but in excess have negative environmental impacts, such as climate change (CO2, CH4 N2O), acidification (NOx) and eutrophication (N, P). Several indirect macro-level drivers affect emissions change. Population and affluence (GDP/capita) often act as upward drivers for emissions. Technology, as emissions per service used, and consumption, as economic intensity of use, may act as drivers resulting in a reduction in emissions. In addition, the development of country-specific emissions is affected by international trade. The aim of this study was to analyse changes in emissions as affected by macro-level drivers in different European case studies. ImPACT decomposition analysis (IPAT identity) was applied as a method in papers I III. The macro-level perspective was applied to evaluate CO2 emission reduction targets (paper II) and the sharing of greenhouse gas emission reduction targets (paper IV) in the European Union (EU27) up to the year 2020. Data for the study were mainly gathered from official statistics. In all cases, the results were discussed from an environmental policy perspective. The development of nitrogen oxide (NOx) emissions was analysed in the Finnish energy sector during a long time period, 1950 2003 (paper I). Finnish emissions of NOx began to decrease in the 1980s as the progress in technology in terms of NOx/energy curbed the impact of the growth in affluence and population. Carbon dioxide (CO2) emissions related to energy use during 1993 2004 (paper II) were analysed by country and region within the European Union. Considering energy-based CO2 emissions in the European Union, dematerialization and decarbonisation did occur, but not sufficiently to offset population growth and the rapidly increasing affluence during 1993 2004. The development of nitrogen and phosphorus load from aquaculture in relation to salmonid consumption in Finland during 1980 2007 was examined, including international trade in the analysis (paper III). A regional environmental issue, eutrophication of the Baltic Sea, and a marginal, yet locally important source of nutrients was used as a case. Nutrient emissions from Finnish aquaculture decreased from the 1990s onwards: although population, affluence and salmonid consumption steadily increased, aquaculture technology improved and the relative share of imported salmonids increased. According to the sustainability challenge in industrial ecology, the environmental impact of the growing population size and affluence should be compensated by improvements in technology (emissions/service used) and with dematerialisation. In the studied cases, the emission intensity of energy production could be lowered for NOx by cleaning the exhaust gases. Reorganization of the structure of energy production as well as technological innovations will be essential in lowering the emissions of both CO2 and NOx. Regarding the intensity of energy use, making the combustion of fuels more efficient and reducing energy use are essential. In reducing nutrient emissions from Finnish aquaculture to the Baltic Sea (paper III) through technology, limits of biological and physical properties of cultured fish, among others, will eventually be faced. Regarding consumption, salmonids are preferred to many other protein sources. Regarding trade, increasing the proportion of imports will outsource the impacts. Besides improving technology and dematerialization, other viewpoints may also be needed. Reducing the total amount of nutrients cycling in energy systems and eventually contributing to NOx emissions needs to be emphasized. Considering aquaculture emissions, nutrient cycles can be partly closed through using local fish as feed replacing imported feed. In particular, the reduction of CO2 emissions in the future is a very challenging task when considering the necessary rates of dematerialisation and decarbonisation (paper II). Climate change mitigation may have to focus on other greenhouse gases than CO2 and on the potential role of biomass as a carbon sink, among others. The global population is growing and scaling up the environmental impact. Population issues and growing affluence must be considered when discussing emission reductions. Climate policy has only very recently had an influence on emissions, and strong actions are now called for climate change mitigation. Environmental policies in general must cover all the regions related to production and impacts in order to avoid outsourcing of emissions and leakage effects. The macro-level drivers affecting changes in emissions can be identified with the ImPACT framework. Statistics for generally known macro-indicators are currently relatively well available for different countries, and the method is transparent. In the papers included in this study, a similar method was successfully applied in different types of case studies. Using transparent macro-level figures and a simple top-down approach are also appropriate in evaluating and setting international emission reduction targets, as demonstrated in papers II and IV. The projected rates of population and affluence growth are especially worth consideration in setting targets. However, sensitivities in calculations must be carefully acknowledged. In the basic form of the ImPACT model, the economic intensity of consumption and emission intensity of use are included. In seeking to examine consumption but also international trade in more detail, imports were included in paper III. This example demonstrates well how outsourcing of production influences domestic emissions. Country-specific production-based emissions have often been used in similar decomposition analyses. Nevertheless, trade-related issues must not be ignored.

Biomass gasification: Environmentally sound technology for decentralized power generation, a case study from India

This study aims at understanding the need for decentralized power generation systems and to explore the potential, feasibility and environmental implications of biomass gasifier-based electricity generation systems for village electrification. Electricity needs of villages are in the range of 5–20 kW depending on the size of the village. Decentralized power generation systems are desirable for low load village situations as the cost of power transmission lines is reduced and transmission and distribution losses are minimised. A biomass gasifier-based electricity generation system is one of the feasible options; the technology is readily available and has already been field tested. To meet the lighting and stationary power needs of 500,000 villages in India the land required is only 16 Mha compared to over 100 Mha of degraded land available for tree planting. In fact all the 95 Mt of woody biomass required for gasification could be obtained through biomass conservation programmes such as biogas and improved cook stoves. Thus dedication of land for energy plantations may not be required. A shift to a biomass gasifier-based power generation system leads to local benefits such as village self reliance, local employment and skill generation and promotion of in situ plant diversity plus global benefits like no net CO2 emission (as sustainable biomass harvests are possible) and a reduction in CO2 emissions (when used to substitute thermal power and diesel in irrigation pump sets).

Carbon Dioxide emissions from an Acacia plantation on peatland in Sumatra, Indonesia

Abstract. Peat surface CO2 emission, groundwater table depth and peat temperature were monitored for two years along transects in an Acacia plantation on thick tropical peat (>4 m) in Sumatra, Indonesia. A total of 2300 emission measurements were taken at 144 locations. The autotrophic root respiration component of the CO2 emission was separated from heterotrophic emissions caused by peat oxidation in three ways: (i) by comparing CO2 emissions within and beyond the tree rooting zone, (ii) by comparing CO2 emissions with and without peat trenching (i.e. cutting any roots remaining in the peat beyond the tree rooting zone), and (iii) by comparing CO2 emissions before and after Acacia tree harvesting. On average, the contribution of root respiration to daytime CO2 emission is 21 % along transects in mature tree stands. At locations 0.5 m from trees this is up to 80 % of the total emissions, but it is negligible at locations more than 1.3 m away. This means that CO2 emission measurements well away from trees are free of any root respiration contribution and thus represent only peat oxidation emission. We find daytime mean annual CO2 emission from peat oxidation alone of 94 t ha−1 yr−1 at a mean water table depth of 0.8 m, and a minimum emission value of 80 t ha−1 yr−1 after correction for the effect of diurnal temperature fluctuations, which resulted in a 14.5 % reduction of the daytime emission. There is a positive correlation between mean long-term water table depths and peat oxidation CO2 emission. However, no such relation is found for instantaneous emission/water table depth within transects and it is clear that factors other than water table depth also affect peat oxidation and total CO2 emissions. The increase in the temperature of the surface peat due to plantation development may explain over 50 % of peat oxidation emissions.

Emissions from India’s transport sector: Statewise synthesis

A decentralized emission inventories are prepared for road transport sector of India in order to design and implement suitable technologies and policies for appropriate mitigation measures. Globalization and liberalization policies of the government in 90's have increased the number of road vehicles nearly 92.6% from 1980–1981 to 2003–2004. These vehicles mainly consume non-renewable fossil fuels, and are a major contributor of green house gases, particularly CO2 emission. This paper focuses on the statewise road transport emissions (CO2, CH4, CO, NOx, N2O, SO2, PM and HC), using region specific mass emission factors for each type of vehicles. The country level emissions (CO2, CH4, CO, NOx, N2O, SO2 and NMVOC) are calculated for railways, shipping and airway, based on fuel types. In India, transport sector emits an estimated 258.10 Tg of CO2, of which 94.5% was contributed by road transport (2003–2004). Among all the states and Union Territories, Maharashtra's contribution is the largest, 28.85 Tg (11.8%) of CO2, followed by Tamil Nadu 26.41 Tg (10.8%), Gujarat 23.31 Tg (9.6%), Uttar Pradesh 17.42 Tg (7.1%), Rajasthan 15.17 Tg (6.22%) and, Karnataka 15.09 Tg (6.19%). These six states account for 51.8% of the CO2 emissions from road transport.

Decentralised carbon footprint analysis for opting climate change mitigation strategies in India

Carbon footprint (CF) refers to the total amount of carbon dioxide and its equivalents emitted due to various anthropogenic activities. Carbon emission and sequestration inventories have been reviewed sector-wise for all federal states in India to identify the sectors and regions responsible for carbon imbalances. This would help in implementing appropriate climate change mitigation and management strategies at disaggregated levels. Major sectors of carbon emissions in India are through electricity generation, transport, domestic energy consumption, industries and agriculture. A majority of carbon storage occurs in forest biomass and soil. This paper focuses on the statewise carbon emissions (CO2. CO and CH4), using region specific emission factors and statewise carbon sequestration capacity. The estimate shows that CO2, CO and CH4 emissions from India are 965.9, 22.5 and 16.9 Tg per year, respectively. Electricity generation contributes 35.5% of total CO2 emission, which is followed by the contribution from transport. Vehicular transport exclusively contributes 25.5% of total emission. The analysis shows that Maharashtra emits higher CO2, followed by Andhra Pradesh, Uttar Pradesh, Gujarat, Tamil Nadu and West Bengal. The carbon status, which is the ratio of annual carbon storage against carbon emission, for each federal state is computed. This shows that small states and union territories (UT) like Arunachal Pradesh, Mizoram and Andaman and Nicobar Islands, where carbon sequestration is higher due to good vegetation cover, have carbon status > 1. Annually, 7.35% of total carbon emissions get stored either in forest biomass or soil, out of which 34% is in Arunachal Pradesh, Madhya Pradesh, Chhattisgarh and Orissa. (C) 2012 Elsevier Ltd. All rights reserved.

Monte Carlo Valuation of natural gas investments

This paper deals with the valuation of energy assets related to natural gas. In particular, we evaluate a baseload Natural Gas Combined Cycle (NGCC) power plant and an ancillary instalation, namely a Liquefied Natural Gas (LNG) facility, in a realistic setting; specifically, these investments enjoy a long useful life but require some non-negligible time to build. Then we focus on the valuation of several investment options again in a realistic setting. These include the option to invest in the power plant when there is uncertainty concerning the initial outlay, or the option's time to maturity, or the cost of CO2 emission permits, or when there is a chance to double the plant size in the future. Our model comprises three sources of risk. We consider uncertain gas prices with regard to both the current level and the long-run equilibrium level; the current electricity price is also uncertain. They all are assumed to show mean reversion. The two-factor model for natural gas price is calibrated using data from NYMEX NG futures contracts. Also, we calibrate the one-factor model for electricity price using data from the Spanish wholesale electricity market, respectively. Then we use the estimated parameter values alongside actual physical parameters from a case study to value natural gas plants. Finally, the calibrated parameters are also used in a Monte Carlo simulation framework to evaluate several American-type options to invest in these energy assets. We accomplish this by following the least squares MC approach.

Income risk of EU coal-fired power plants after Kyoto

Coal-fired power plants may enjoy a significant advantage relative to gas plants in terms of cheaper fuel cost. Still, this advantage may erode or even turn into disadvantage depending on CO2 emission allowance price. This price will presumably rise in both the Kyoto Protocol commitment period (2008-2012) and the first post-Kyoto years. Thus, in a carbon-constrained environment, coal plants face financial risks arising in their profit margins, which in turn hinge on their so-called "clean dark spread". These risks are further reinforced when the price of the output electricity is determined by natural gas-fired plants' marginal costs, which differ from coal plants' costs. We aim to assess the risks in coal plants' margins. We adopt parameter values estimated from empirical data. These in turn are derived from natural gas and electricity markets alongside the EU ETS market where emission allowances are traded. Monte Carlo simulation allows to compute the expected value and risk profile of coal-based electricity generation. We focus on the clean dark spread in both time periods under different future scenarios in the allowance market. Specifically, bottom 5% and 10% percentiles are derived. According to our results, certain future paths of the allowance price may impose significant risks on the clean dark spread obtained by coal plants.

Towards more sustainable and environmentally-friendly concretes: The use of silica fume

Concrete is the most widely used construction material. At the same time, however, the concrete industry is a major CO2 emitter thus contributing towards global warming. While enhanced efficiency in the production of concrete is not likely to dramatically reduce the CO2 emissions, cement replacement by a supplementary material or mineral additive, such as silica fume, which is not associated with CO2 emission, can substantially reduce the aforementioned problem. The present work discusses the benefits of incorporating mineral additives in concrete and shows that these additives can improve both the mechanical and physical properties of the end-product, and hence its durability, albeit with a reduction in cement content. © 2009 WIT Press.

川西北高寒草甸土壤呼吸研究：季节动态和放牧效应

除植被冠层的光合作用之外，土壤的呼吸作用是陆地生态系统碳收支中最大的通量。土壤呼吸即使发生较小的变化也能显著地减缓或加剧大气中CO2浓度的增加，从而明显影响到全球气候变化。土壤呼吸速率变化与否以及变化的方向可以反映生态系统对环境变化的敏感程度和响应模式。尽管如此，土壤呼吸仍是一个为人们了解不多的生态系统过程。 草地生态系统是陆地生态系统的一个重要组成部分。针对草地土壤呼吸进行野外实验研究和相应方法论的探讨将对区域乃至全球碳源汇性质的准确估算具有重要的科学意义。然而，近几年来关于草地土壤呼吸的主要研究工作都集中在温带草原和部分热带草原，而针对高寒草甸生态系统土壤呼吸的研究报道还很少。 2008年4月至2009年4月期间，我分别在2008年6、8、10、12月和2009年2月和4月分6次对川西北的典型高寒草甸群落的土壤呼吸进行观测，分析了不同类型高寒草甸群落土壤呼吸的季节变化特征以及环境因子和放牧模式对其影响。主要研究结果如下： 1）该地区高寒草甸生态系统在生长季（6月～8月）土壤呼吸速率较大（6.07～9.30μmolCO2¡m-2¡s-1 ） ， 在非生长季（ 12 月～ 2 月） 较小（ 0.16 ～0.49μmolCO2¡m-2¡s-1 ） 。土壤CO2 年累积最大释放量为3963 ～ 5730gCO2¡m-2¡yr-1，其中，生长季土壤CO2的释放量占年总释放量的85%～90%。非生长季占10%～15%。非生长季所占比例略小于冬季积雪覆盖地区的冬季土壤呼吸占年土壤呼吸量的比例（14%～30%）。温度，尤其地温，是影响该地区高寒草甸生态系统土壤呼吸速率的最主要环境因子。土壤呼吸速率与地上生物量和土壤水分之间没有显著相关性，但是土壤含水量过大会导致土壤呼吸速率下降。 2）在观测期内，草丘区的土壤呼吸显著高于对照区的土壤呼吸，其最大土壤呼吸速率为16.77μmolCO2¡m-2¡s-1，土壤CO2 年累积最大释放量为8145gCO2¡m-2¡yr-1，是对照区的近2 倍。由于草丘在高寒草甸中占有较大的面积比例（近30%），因此，它将对高寒草甸生态系统的碳循环起着重要的作用。 3）放牧模式不仅可以影响高寒草甸群落的土壤CO2 排放，而且还可以改变土壤呼吸的温度敏感性（Q10）。本研究表明，在生长季有长期放牧活动干扰时将会增加土壤向大气中释放二氧化碳的速度，促使土壤碳库中碳的流失。禁牧样地的土壤呼吸速率在刚禁牧时先迅速增大，随着禁牧时间的延长土壤呼吸速率将会下降。此外，与其它放牧模式相比，冬季放牧将高寒草甸群落土壤呼吸速率在生长季达到最大值的时间明显向后推迟。不同放牧模式下高寒草甸群落土壤呼吸的Q10 值大小顺序为：禁牧一年群落>冬季放牧群落>禁牧三年群落>夏季放牧群落>自由放牧群落。 4）基于呼吸室技术的观测方法中，测量前的剪草处理可以明显改变该地区高寒草甸群落的土壤温度和土壤呼吸速率。在生长季，剪草处理将使土壤呼吸速率的瞬时响应增加90%左右。由于剪草处理明显增加了剪草样方白天的土壤温度，而土壤温度与土壤呼吸之间存在着极显著的指数相关关系，因而剪草处理导致土壤呼吸速率迅速增加。因此，在高寒地区基于呼吸室技术观测的土壤呼吸应当进行校正。 综上所述，川西北高寒草甸生态系统土壤呼吸速率在生长季较高，而在非生长季较低。土壤温度是影响该地区土壤呼吸的最主要环境因子。在实验观测期，草丘区土壤呼吸速率显著高于对照区的，是对照区土壤呼吸速率的近2倍。由于测量前的剪草处理可以明显改变待测点的土壤呼吸速率，因此，应对在高寒地区基于呼吸室技术观测的土壤呼吸进行校正。 Soil respiration is the second largest component (less than plant phtotosynthesis) of carbon dioxide flux between terrestrial ecosystems and the atmosphere. A minor change in soil respiration rate can significantly slow down or accelerate the increase of atmospheric CO2 concentration that is closely related to global climatic change. In turn, the change in the flux direction and rate of soil respiration may indicate the elasticity and stability of ecosystems to global changes and human disturbance. However, soil respiration is still an ecosystem process that has been poorly understood. Grassland ecosystem is an important component of the terrestrial ecosystem. Accurately estimating the CO2 flux from soil to atmosphere in situ is the key to evaluating the carbon resource and sink regionally or globally. Despite of extensive studies on the temperate and tropic grasslands, the soil respiration of alpine meadows has not substantially been measured. In the current study, soil respiration was measured for an annual cycle from April, 2008 to April, 2009 for the alpine meadow in northwestern Sichuan Province of China to determine the seasonal variation of soil respiration for the typical plant communities. The results are shown as follows: 1) Large seasonal variation of soil respiration was observed in the alpine meadow. The rate of soil respiration was the greatest (6.07～9.30μmolCO2¡m-2¡s-1) in June and the smallest (0.16 ～ 0.49μmolCO2¡m-2¡s-1) occurred from December to February in the non-growing season. The total emission of soil CO2 was estimated as 3963～5730 gCO2¡m-2¡yr-1, 85%~90% of which was released during the growing season, and 10%~15% during the non-growing season which was slightly less than the ratio of winter and annual CO2 flux from soil. Temperature, particularly the soil temperature, was the major environmental factor regulating the soil respiration. Significant and positive relationships were not found between soil respiration and soil moisture and between soil respiration and plant above-ground biomass, but excessive soil water content would decrease in the rate of soil respiration. 2) The rate of soil respiration in grass hummock communities was up to 16.77μmolCO2¡m-2¡s-1, which was about twice as great as in the controls (communities located in low and even sites). Considering the large proportion (about 30% on average) of hummock area in the meadow, it can be concluded that the hummocks played an important role in the carbon cycling of the study ecosystem. 3) Grazing patterns affected the flux of CO2 emission and the temperature sensitivity of soil respiration (Q10) in the alpine meadow. Grazing during growing season increased the rate of soil respiration. The rate of soil respiration increased significantly immediately after the alpine meadow being fenced, but thereafter decreased. In addition, grazing in winter delayed the peak respiration rate relative to the non-grazing mode. The Q10 value was the largest in the non-grazed area for one year, and next came the area with grazing in winter, followed by the non-grazed area for three years, the area with grazing in summer, and the non-limited grazed area. 4) In the chamber-based techniques, clipping manipulation before each measurement increased the transient rate of soil respiration by about 90% in the summer of the alpine meadow. As increase in soil temperature at daytime in the clipped plots by clipping and the exponential relationship between soil respiration and temperature, clipping manipulation led to increase in the rate of soil respiration. This suggested that a correction should be done for the techniques if employed in alpine and cold regions. In summary, the rate of soil respiration in the alpine meadow was the greatest in June and the smallest occurred from ecember to February in the non-growing season. Soil temperature was the major environmental factor regulating the soil respiration. The rate of soil respiration in grass hummock communities was up to 16.77μmolCO2¡m-2¡s-1, which was about twice as great as in the controls. A correction should be done for the techniques if employed in alpine and cold regions, because of the effect of clipping manipulation on soil temperature and respiration.

A comparative study of non-oxidative pyrolysis and oxidative cracking of cyclohexane to light alkenes

Naphthene is generally considered difficult to convert in traditional pyrolysis, but the ring rupture becomes fairly easy with the presence of oxygen in the gas phase oxidative cracking of the model compound, cyclohexane. About 86.8% conversion of cyclohexane, 43.7% yield of light alkenes, 6.6% yield of benzene and 14.3% yield of CO could be obtained at 750 degreesC, at which temperature the pyrolysis of cyclohexane was negligible, while at 850 degreesC, the total yield of alkenes, benzene and CO was as high as 80% (50%, 12% and 18%, respectively) with 98% conversion of cyclohexane. The gas phase oxidative cracking process could be run in an autothermal way (cyclohexane/O-2 mole ratio of 0.69-0.8 in theory), which would minimize energy consumption and capital costs of the whole process. CO prevailed in the produced CO, and the yield Of CO2 was always below 1%, which means about 90% Of CO2 emission by fuel burning in pyrolysis would be saved. The gas phase oxidative cracking process appears to be an environmentally benign and efficient route for light alkene production with naphthene rich feedstocks. (C) 2004 Published by Elsevier B.V.