Transforming the Cement Industry into a Key Environmental Infrastructure for Urban Ecosystem: A Case Study of an Industrial City in China

Under the dual pressure of environmental constraints and increasingly thin profit margins, the cement industry in China is in a predicament. To alleviate the environmental and the economic pressure of the cement industry and to tackle the problem of delayed environmental infrastructure construction, this article introduced an urban ecosystem in which the cement industry was transformed into an effective complement to environmental infrastructure. The Xinfeng Cement Industrial Park in China, which has a production capacity of 5 million tonnes per annum (Mt/a) of clinker, was chosen as a case study. Our methodology involved proposing technologies to develop an efficient cement plant‐centered urban ecosystem; evaluating its environmental and economic performance; identifying barriers in its promotion; and proposing supportive policies. Results showed that the city's waste recycling ratio rose from about 50% to 70%, saving 0.6 Mt/a of coal equivalent and reducing about 3.0 Mt/a of resulting carbon dioxide (CO₂) emissions. The life span of the city's landfill site was extended by about 30 years. The total investment was 3.2 billion yuan (about US$480 million), 1 with an average payback period of 3 years. The Xinfeng Cement Industrial Park was transformed from an energy‐intensive consumer and a significant CO₂ emitter to a key industrial waste recycler, a crucial municipal waste co‐processor, an important new building material supplier, and a potential energy producer. Last, the “not‐in‐my‐back‐yard” (NIMBY) effect from constructing new environmental infrastructure was also avoided.     

我国典型城市化石能源消费CO2排放及其影响因素比较研究

城市是化石能源消费和CO_2排放的主要区域。分析典型城市化石能源消费CO_2排放特征,明确不同城市CO_2排放动态及主要影响因素的差异,是开展城市减排行动的重要科学依据。采用IPCC推荐方法及中国的排放参数核算11个典型城市2006—2015年间化石能源消费产生的CO_2排放量。根据各城市经济发展和CO_2排放特征将之分为四类:经济高度发达城市(北京、上海、广州)、高碳排放城市(重庆、乌鲁木齐、唐山)、低排放低增长城市(哈尔滨、呼和浩特和大庆)和低排放高增长城市(贵阳、合肥),并运用对数平均迪氏指数法(Logarithmic Mean Divisia Index,即LMDI分解法)对比分析了四类城市CO_2排放量的影响因素。结果表明:(1)研究期内大部分城市CO_2排放总量有所增加,仅北京和广州呈下降趋势,工业部门CO_2排放在城市排放总量及其变化中占据主导地位;四类城市的人均CO_2排放量表现出与排放总量相似的变化趋势;CO_2排放强度整体上表现为经济高度发达城市(均值为0.88 t CO_2/万元)低排放低增长城市(均值为2.82 t CO_2/万元)低排放高增长城市(均值为3.05 t CO_2/万元)高碳排放城市(均值为6.62 t CO_2/万元)。(2)在城市CO_2排放的影响因素中,经济发展和人口规模均是4类城市CO_2排放增长的促进因素,但经济发展效应的累积贡献值大于人口规模效应;能源强度降低是4类城市CO_2排放最主要的抑制因素,且经济高度发达和高碳排放城市的抑制作用强于其他两类城市;对第三产业GDP年平均增速高于第二产业的6个城市来说,产业结构是CO_2排放的抑制因素;能源结构的变化仅对煤炭消费比重较低且降幅较大的北京和广州的CO_2排放是抑制作用,累积贡献值分别为-21.73Mt和-0.03Mt,而对其他城市,特别是高碳排放城市的CO_2排放具有明显的促进作用。     

Materials Metabolism Analysis of China's Highway Traffic System (HTS) for Promoting Circular Economy

With the rapid growth of highway mileage and vehicles, the Chinese highway traffic system (HTS) has become one of the great resource consumers. This article attempts to evaluate the material metabolism of China's HTS during 2001–2005 using the approach of material flow analysis (MFA) and to explore possible measures to promote circular economy throughout HTS. We measured a set of indicators to illustrate the whole material metabolism of China's HTS. The results indicated that the direct material input (DMI) of China's HTS increased from 1181.26 million tonnes (Mt) in 2001 to 1,874.57 Mt in 2005, and about 80% of DMI was accumulated in the system as infrastructure and vehicles. The domestic processed output (DPO) increased by 59.0% from 2001 to 2005. Carbon dioxide and solid waste accounted for 80.5% and 10.4% of DPO, respectively. The increase of resource consumption and pollutant emissions kept pace with the growth of transportation turnover. All these suggest that China's HTS still followed an extensive linear developing pattern with large resource consumption and heavy pollution emissions during the study period, which brought great challenges to the resources and the environment. Therefore, it's high time for China to implement a circular economy throughout the HTS by instituting resource and energy savings, by reducing emissions in the field of infrastructure construction and maintenance, by reducing vehicles’ energy and materials consumption, and by recycling waste materials.     

Maintenance and Expansion: Modeling Material Stocks and Flows for Residential Buildings and Transportation Networks in the EU25

Material stocks are an important part of the social metabolism. Owing to long service lifetimes of stocks, they not only shape resource flows during construction, but also during use, maintenance, and at the end of their useful lifetime. This makes them an important topic for sustainable development. In this work, a model of stocks and flows for nonmetallic minerals in residential buildings, roads, and railways in the EU25, from 2004 to 2009 is presented. The changing material composition of the stock is modeled using a typology of 72 residential buildings, four road and two railway types, throughout the EU25. This allows for estimating the amounts of materials in in‐use stocks of residential buildings and transportation networks, as well as input and output flows. We compare the magnitude of material demands for expansion versus those for maintenance of existing stock. Then, recycling potentials are quantitatively explored by comparing the magnitude of estimated input, waste, and recycling flows from 2004 to 2009 and in a business‐as‐usual scenario for 2020. Thereby, we assess the potential impacts of the European Waste Framework Directive, which strives for a significant increase in recycling. We find that in the EU25, consisting of highly industrialized countries, a large share of material inputs are directed at maintaining existing stocks. Proper management of existing transportation networks and residential buildings is therefore crucial for the future size of flows of nonmetallic minerals.     

The Bahamas at risk: Material stocks,sea-level rise,and the implications for development

Recent research suggests that over 75% of resources extracted globally now go toward creating, maintaining, or operating material stocks (MS) to provide societal services like housing, transport, education, and health. However, the integrity of current and future built environments, and the capacity of the system to continue providing services, are threatened by extreme events and sea-level rise (SLR). This is especially significant for the most disaster-prone countries in the world: Small Island Developing States. In the aftermath of disasters, complex rebuilding efforts require substantial material and economic resources, oftentimes incurring massive debt. Understanding the composition and dynamics of MS and environmental threats is essential for current and future sustainable development. Drawing on open-source OpenStreetMap (OSM) data, we conducted a spatially explicit material stock analysis (MSA) for The Bahamas for 2021, where we included buildings and transport MS, and SLR exposure scenarios. Total MS was estimated at 76 million tonnes (Mt) or 191 tonnes per capita (t/cap) of which transport comprises 43%. These MS are likely to increase by 36 Mt in the future. Simulations show that under 1-, 2-, or 3-m SLR scenarios, around 4, 6, and 9 Mt of current MS will be exposed, with transport MS at greatest risk, with over 80% of total exposure in each scenario. Our findings highlight the critical role that key MS play in sustainability and resilience, contributing to the emphasis on effective development planning and climate change adaptation strategies, and to the exploration of the use of OSM data for studying these objectives.     

Ecology profile of the german high-speed rail passenger transport system,ICE

Intention, Goal, Scope, Background, Objectives  Environmental effects caused by the railway transport services have rarely been investigated in depth from a systemic point of view. A screening LCA, called ecology profile, of the German high-speed passenger train system, the ICE, is presented here, based on a study conducted by the University of Halle and the Deutsche Bahn AG, the major German rail operator. In this study, the resource consumption caused by traction, manufacturing and maintenance of ICE trains, as well as construction and operation of the supporting rail infrastructure and buildings, have been evaluated using cumulative energy demand (CED), cumulative material input per service unit (MIPS) and CO₂ emissions as indicators. Methods  Approximately 200 items of inventory data were collected from DB AG experts, manufacturers, site balances and the associated literature. They were allocated in order to derive 100-person-kilometre-related mass and energy consumption figures. The appropriate CED, MIPS and CO₂ factors were applied in order to quantify the indirect efforts associated with the inventory data. Conclusions  For the reference high-speed route investigated, Hanover-Wuerzburg, the railroad infrastructure does not contribute the high share of resource consumption to the life cycle of the transport service which was expected from other studies. For the reference route, the CED of the infrastructure contributes 13% to the total CED per 100 person kilometres, whilst the energy demand of the traction process dominates the life cycle. Within the railway infrastructure, the construction of tunnels and the heating of rail points during winter time are significant primary-energy active components, whereas the energy requirement for maintaining the railway stations is a minor factor in comparison. The environmental impact of new technologies for designing rail tracks have also been analysed. The new ballastless slab track technology investigated needs higher absolute resource inputs in the construction phase compared with the traditional gravel bed, but due to higher life expectancy, it competes favourably at the 100-person-kilometre level, at least in terms of material requirements. Efforts to reduce the traction energy consumption of the ICE train will have the greatest impact on the CED of the transport system. In summary, a total of 48 kg of solid primary resources are needed for a passenger to travel 100 km by ICE. Recommendations/Outlook  The results presented can be used for modelling other high-speed railway transport systems. A comparison of the ecology profiles of the German, French and Japanese high-speed train systems would be of interest in order to identify potential areas for improvement. Additional studies are needed to evaluate the short-hop, commuter train service. Further efforts should be directed to comparing the infrastructure of the high speed train and that of highway road traffic.     

Technoecological analysis of energy carriers for long‐haul transportation

Long‐haul transportation demand is predicted to increase in the future, resulting in higher carbon dioxide emissions. Different drivetrain technologies, such as hybrid or battery electric vehicles, electrified roads, liquefied natural gas and hydrogen, might offer solutions to this problem. To assess their ecological and economic impact, these concepts were simulated including a weight and cost model to estimate the total cost of ownership. An evolutionary algorithm optimizes each vehicle to find a concept specific optimal solution. A model calculates the minimum investment in infrastructure required to meet the energy demand for each concept. A well‐to‐wheel analysis takes into account upstream and on‐road carbon dioxide emissions, to compare fully electric vehicles with conventional combustion engines. Investment in new infrastructure is the biggest drawback of electrified road concepts, although they offer low CO₂ emissions. The diesel hybrid is the best compromise between carbon reduction and costs.     

Estimating the Material Stock of Roads: The Vietnamese Case Study

This study is a pioneering effort to quantify the materials stocked in the road network of a developing country, Vietnam, and analyze its relationships to the country's recent economic development. National road networks function as capital and infrastructure investments that are necessary catalysts for countries’ development, while requiring the extraction of vast amounts of construction materials for expansion and maintenance causing environmental impacts. However, there has so far been little research on the subject, especially in developing countries. We compile material stock and flow accounts for Vietnam's roads from 2003 to 2013 on the national and provincial levels, finding that approximately 40% of the domestic consumption of construction materials is for expanding and maintaining the road network, and the materials stocked in the road network doubled from 1,321 million metric tons in 2003 to 2,660 million metric tons in 2012. Material stock growth rates closely resembled those of gross domestic product (GDP) in this period, suggesting a codependency of physical infrastructure development and economic development. On the provincial level, our results show local disparities in the stock and its capacity to support the transportation of passengers and freight, especially considering the surging growth of vehicles in urban centers. By showcasing the challenges of conducting a material flow and stock analysis in a developing country, this study not only sheds light on Vietnam's transportation material stock and its policy implications, but also serves as a case study for further work in similar countries.     

Does Size Matter? Scaling of CO2 Emissions and U.S. Urban Areas

Urban areas consume more than 66% of the world’s energy and generate more than 70% of global greenhouse gas emissions. With the world’s population expected to reach 10 billion by 2100, nearly 90% of whom will live in urban areas, a critical question for planetary sustainability is how the size of cities affects energy use and carbon dioxide (CO₂) emissions. Are larger cities more energy and emissions efficient than smaller ones? Do larger cities exhibit gains from economies of scale with regard to emissions? Here we examine the relationship between city size and CO₂ emissions for U.S. metropolitan areas using a production accounting allocation of emissions. We find that for the time period of 1999–2008, CO₂ emissions scale proportionally with urban population size. Contrary to theoretical expectations, larger cities are not more emissions efficient than smaller ones.     

Quantifying the relationship between urban development intensity and carbon dioxide emissions using a panel data analysis

As a factor associated with urban management and planning, urban development intensity (UDI) could in fact form the basis for a new rationale in coordinating urban sustainable development and reducing CO₂ emissions. However, existing literature engaging in the task of quantifying the impacts of urban development intensity on CO₂ emissions is limited. Therefore, the goal of this study is to quantify the relationship between urban development intensity and CO₂ emissions for a panel made up of the five major cities in China (Beijing, Shanghai, Tianjin, Chongqing and Guangzhou) using time series data from 1995 to 2011. Firstly, this study calculated CO₂ emissions for the five selected cities and presented a comprehensive index system for the assessment of the level of urban development intensity based on six aspects (land-use intensity, economic intensity, population intensity, infrastructure intensity, public service intensity and eco-environmental intensity) using locally important socioeconomic variables. Panel data analysis was subsequently utilised in order to quantify the relationships between urban development intensity and CO₂ emissions. The empirical results of the study indicate that factors such as land-use intensity, economic intensity, population intensity, infrastructure intensity and public service intensity exert a positive influence on CO₂ emissions. Further, the estimated coefficients suggest that land-use intensity is the most important factor in relation to CO₂ emissions. Conversely, eco-environmental intensity was identified as having a major inhibitory effect on CO₂ emission levels. The findings of this study hold important implications for both academics and practitioners, indicating that, on the path towards developing low-carbon cities in China, the effects of urban development intensity must be taken into consideration.     

Decomposition of soil and plant carbon from pasture systems after 9 years of exposure to elevated CO2: impact on C cycling and modeling

Elevated atmospheric CO₂ may alter decomposition rates through changes in plant material quality and through its impact on soil microbial activity. This study examines whether plant material produced under elevated CO₂ decomposes differently from plant material produced under ambient CO₂. Moreover, a long‐term experiment offered a unique opportunity to evaluate assumptions about C cycling under elevated CO₂ made in coupled climate–soil organic matter (SOM) models. Trifolium repens and Lolium perenne plant materials, produced under elevated (60 Pa) and ambient CO₂ at two levels of N fertilizer (140 vs. 560 kg ha^?1 yr^?1), were incubated in soil for 90 days. Soils and plant materials used for the incubation had been exposed to ambient and elevated CO₂ under free air carbon dioxide enrichment conditions and had received the N fertilizer for 9 years. The rate of decomposition of L. perenne and T. repens plant materials was unaffected by elevated atmospheric CO₂ and rate of N fertilization. Increases in L. perenne plant material C : N ratio under elevated CO₂ did not affect decomposition rates of the plant material. If under prolonged elevated CO₂ changes in soil microbial dynamics had occurred, they were not reflected in the rate of decomposition of the plant material. Only soil respiration under L. perenne, with or without incorporation of plant material, from the low‐N fertilization treatment was enhanced after exposure to elevated CO₂. This increase in soil respiration was not reflected in an increase in the microbial biomass of the L. perenne soil. The contribution of old and newly sequestered C to soil respiration, as revealed by the ¹³C‐CO₂ signature, reflected the turnover times of SOM–C pools as described by multipool SOM models. The results do not confirm the assumption of a negative feedback induced in the C cycle following an increase in CO₂, as used in coupled climate–SOM models. Moreover, this study showed no evidence for a positive feedback in the C cycle following additional N fertilization.     

Impact of structural changes in wood‐using industries on net carbon emissions in Finland

Forests and forest industries can contribute to climate change mitigation by sequestering carbon from the atmosphere, by storing it in biomass, and by fabricating products that substitute more greenhouse gas emission intensive materials and energy. The objectives of the study are to specify alternative scenarios for the diversification of wood product markets and to determine how an increasingly diversified market structure could impact the net carbon emissions (NCEs) of forestry in Finland. The NCEs of the Finnish forest sector were modelled for the period 2016–2056 by using a forest management simulation and optimization model for the standing forests and soil and separate models for product carbon storage and substitution impacts. The annual harvest was fixed at approximately 70 Mm³, which was close to the level of roundwood removals for industry and energy in 2016. The results show that the substitution benefits for a reference scenario with the 2016 market structure account for 9.6 Mt C (35.2 Mt CO₂ equivalent [CO₂ eq]) in 2056, which could be further increased by 7.1 Mt C (26 Mt CO₂ eq) by altering the market structure. As a key outcome, increasing the use of by‐products for textiles and wood–plastic composites in place of kraft pulp and biofuel implies greater overall substitution credits compared to increasing the level of log harvest for construction.     

The weight of islands: Leveraging Grenada's material stocks to adapt to climate change

The building stock consumes large amounts of resources for maintenance and expansion which is only exacerbated by disaster events where large‐scale reconstruction must occur quickly. Recent research has shown the potential for application of material stock (MS) accounts for informing disaster risk planning. In this research, we present a methodological approach to analyze the vulnerability of the material stock in buildings to extreme weather events and sea‐level rise (SLR) due to climate change. The main island of Grenada, a Small Island Developing State (SIDS) in the Caribbean region, was used as a case study. A bottom‐up approach based on a geographic information system (GIS) is used to calculate the total MS of aggregate, timber, concrete, and steel in buildings. The total MS in buildings in 2014 was calculated to be 11.9 million tonnes (Mt), which is equivalent to 112 tonnes per capita. Material gross addition to stock (GAS) between 1993 to 2009 was 6.8 Mt and the average value over the time period was 4.0 tonnes per capita per year. In the year following Hurricane Ivan (2004), the per capita GAS for timber increased by 172%, while for other metals, GAS spiked by 103% (compared to average growth rates of 11% and 8%, respectively, between 1993 and 2009). We also ran a future “Ivan‐II” scenario and estimated a hypothetical loss of between 135 and 216 kilotonnes (kt) of timber from the building stock. The potential impact of SLR is also assessed, with an estimated 1.6 Mt of building material stock exposed under a 2‐m scenario. We argue that spatial material stock accounts have an important application in planning for resilience and provide indication of the link between natural disaster recovery and resource use patterns.     

Weight under Steel Wheels: Material Stock and Flow Analysis of High‐Speed Rail in China

The construction of a nation‐wide high‐speed rail (HSR) network has emerged as a hugely expensive and ambitious infrastructure project in China. As of December 2012, some 8,800 kilometers (km) of double‐track HSR lines came into service in the country, accounting for 40% of the total HSR length in the world. The network is expected to expand to 34,000 km or longer in around two decades. As the first HSR system specially built and operated in an economically developing country, it helps integrate the sprawling economy and lift the quality of life of the increasing urban population. China's experiences in HSR are expected to be of value to other countries aiming to adopt bullet train systems, especially those at a similar level of industrialization and urbanization. This work specifically examines material stocks and flows associated with the HSR infrastructure construction in China. A major distinction from the construction of HSR tracks in Europe is that nearly 70% of the HSR tracks in China are laid upon bridges or inside tunnels, which are structures that demand great amounts of raw materials. The entire network, once completed by 2030, will cumulatively require 83 to 137 million tonnes (Mt) of steel and 560 to 920 Mt of cement. This is still a small share of China's use of material resources. Nonetheless, the massive application of the steel‐ and cement‐intensive structures deserves consideration when assessing the environmental performance of HSR over its entire life cycle.     

Spatial analysis of urban material stock with clustering algorithms: A Northern European case study

A large share of construction material stock (MS) accumulates in urban built environments. To attain a more sustainable use of resources, knowledge about the spatial distribution of urban MS is needed. In this article, an innovative spatial analysis approach to urban MS is proposed. Within this scope, MS indicators are defined at neighborhood level and clustered with k‐mean algorithms. The MS is estimated bottom‐up with (a) material‐intensity coefficients and (b) spatial data for three built environment components: buildings, road transportation, and pipes, using seven material categories. The city of Gothenburg, Sweden is used as a case study. Moreover, being the first case study in Northern Europe, the results are explored through various aspects (material composition, age distribution, material density), and, finally, contrasted on a per capita basis with other studies worldwide. The stock is estimated at circa 84 million metric tons. Buildings account for 73% of the stock, road transport 26%, and pipes 1%. Mineral‐binding materials take the largest share of the stock, followed by aggregates, brick, asphalt, steel, and wood. Per capita, the MS is estimated at 153 metric tons; 62 metric tons are residential, which, in an international context, is a medium estimate. Denser neighborhoods with a mix of nonresidential and residential buildings have a lower proportion of MS in roads and pipes than low‐density single‐family residential neighborhoods. Furthermore, single‐family residential neighborhoods cluster in mixed‐age classes and show the largest content of wood. Multifamily buildings cluster in three distinct age classes, and each represent a specific material composition of brick, mineral binding, and steel. Future work should focus on megacities and contrasting multiple urban areas and, methodologically, should concentrate on algorithms, MS indicators, and spatial divisions of urban stock.     

Variable impact transportation (VIT) model for energy and environmental impact of hauling truck operation

Purpose

Fuel economy and emissions of heavy-duty trucks greatly vary based on vehicular/environmental conditions. Large-scale infrastructure construction projects require a large amount of material/equipment transportation. Single-parameter generic hauling models may not be the best option for an accurate estimation of hauling contribution in life cycle assessment (LCA) involving construction projects; therefore, more precise data and parameterized models are required to represent this contribution. This paper discusses key environmental/operational variables and their impact on transportation of materials and equipment; a variable-impact transportation (VIT) model accounting for these variables was developed to predict environmental impacts of hauling.

Methods

The VIT model in the form of multi-nonlinear regression equations was developed based on simulations using the U.S. Environmental Protection Agency (EPA)’s Motor Vehicle Emission Simulator (MOVES) to compute all the impact categories in EPA’s TRACI 2.1 and energy consumption of transportation. Considering actual driving cycles of hauling trucks recorded during a pavement rehabilitation project, the corresponding environmental impacts were calculated, and sensitivity analyses were performed. In addition, an LCA case study based on historical pavement reconstruction projects in Illinois was conducted to analyze the contribution of transportation and variability of its impacts during the pavements’ life cycle.

Results and discussion

The importance of vehicle driving cycles was realized from simulation results. The case study results showed that considering driving cycles using the VIT model could increase the contribution of hauling in total life cycle Global Warming Potential (GWP) and total life cycle GWP itself by 2–4 and 3–5%, respectively. In addition to GWP, ranges of other hauling-related impact categories including Smog, Ozone Depletion, Acidification, and Primary Energy Demand from fuel were presented based on the case study. Ozone Depletion ranged from 9 to 45%, and Smog ranged from 11 to 48% of the total relevant life cycle impacts. The GWP contribution of hauling in pavement LCA ranged between 5 and 32%. The results indicate that the contribution of hauling transportation can be significant in pavement LCA.

Conclusions

For large-scale roadway infrastructure construction projects that need a massive amount of material transportation, high fidelity models and data should be used especially for comparative LCAs that can be used as part of decision making between alternatives. The VIT model provides a simple analytical platform to include the critical vehicular/operational variables without any dependence on an external software; the model can also be incorporated in those studies where some of the transportation activity data are available.

     

Geospatial Characterization of Material Stock in the Residential Sector of a Latin‐American City

Building stock constitutes a huge repository of construction materials in a city and a potential source for replacing primary resources in the future. This article describes the application of a methodological approach for analyzing the material stock (MS) in buildings and its spatial distribution at a city‐wide scale. A young Latin‐American city, the city of Chiclayo in Peru, was analyzed by combining geographical information systems (GIS) data, census information, and data collected from different sources. Application of the methodology yielded specific indicators for the physical size of buildings (i.e., gross floor area and number of stories) and their material composition. The overall MS in buildings, in 2007, was estimated at 24.4 million tonnes (Mt), or 47 tonnes per capita. This mass is primarily composed of mineral materials (97.7%), mainly concrete (14.1 Mt), while organic materials (e.g., 0.15 Mt of wood) and metals (e.g., 0.40 Mt of steel) constitute the remaining share (2.3%). Moreover, historical census data and projections were used to evaluate the changes in the MS from 1981 to 2017; showing a 360% increase of the MS in the last 36 years. This study provides essential supporting information for urban planners, helping to provide a better understanding of the availability of resources in the city and its future potential supply for recycling as well as to develop strategies for the management of construction and demolition waste.     

The effect of bacterial strain and temperature changes on the nitrogenase activity of Lotus pedunculatus root nodules

After 40 days of growth at 25°C, Lotus pedunculatus cav., cv. Maku plants infected with Rhizobium loti strain NZP2037 displayed similar relative growth rates but had twice the nodule mass and only one third the whole plant dry weight of plants infected with Bradyrhizobium sp. (Lotus) strain CC814s. In the NZP2037 symbiosis, the rate of CO₂ evolution (per g dry weight of nodulated root) was 1.6 times as high as that in the CC814s symbiosis while the rate of C₂H₂ reduction (per g dry weight of nodule) was only 48% of that in the CC814s symbiosis. Studies of the effect of short term temperature changes on the gas exchange characteristics (CO₂ and H₂ evolution, C₂H₂ reduction) of these symbioses revealed wide differences in the optima for C₂H₂ reduction. Nodules infected with NZP2037 displayed maximal C₂H₂ reduction rates [157 μmol (g dry weight nodule)^?1 h^?1] at 12°C, whereas nodules infected with CC814s were optimal at 30°C [208 μmol (g dry weight nodule)^?1 h^?1]. These short term studies suggested that differences in temperature optima for N₂ may have partially accounted for the poorer effectivity, at 25°C, of strain NZP2037 when compared with strain CC-814s. The relative efficiency [RE = 1 – (H₂ evolution/C₂H₂ reduction)] of N₂ fixation varied widely with temperature in the two symbioses, but there was a general trend toward higher RE with lower temperatures. The ratio of CO₂ evolution: C₂H₂ reduction (mol/mol) in nodulated roots infected with CC814s was constant (ca 10 CO₂/C₂H₂) between 5°C and 30°C, whereas in plants infected with NZP2037 it reached a minimal value of 3.3 CO₂/C₂H₂ at 10°C and was 19 CO₂/C₂H₂ at the growing temperature (25°C).     

旅游交通碳排放的空间结构与情景分析

旅游业作为全球第一大产业,是影响气候变化的重要因素之一,旅游碳排放的相关研究近年来已经引起学者们的关注.选择了九寨沟风景区、西安碑林博物馆、南京珍珠泉风景区3个旅游交通模式差异明显的案例地为例,根据实地问卷调查数据估算了九寨沟风景区、西安碑林博物馆、珍珠泉旅游风景区2010年的旅游交通碳排放总量分别为654.18,108.44和15.92 Gg.通过比较九寨沟、西安碑林和珍珠泉的碳排放累积曲线,得出不同旅游平均距离的景区的碳排放结构均衡度有所不同,旅游平均距离偏低景区的碳排放结构最不均衡.同时,旅游景区的交通碳排放在距离上具有分段性,不同旅游平均距离的景区交通碳排放的空间结构具有明显的差异性.通过4种不同的交通情景分析发现,旅游平均距离高和距离中等的景区对飞机的碳减排敏感度较高,旅游平均距离偏低的景区自驾车的碳减排效果最为明显.研究结果为旅游管理部门根据碳排放结构有针对性的制定差异化的旅游交通碳减排政策提供了参考和借鉴.     

北京城区道路系统路网空间特征及其与LST和NDVI的相关性

城市道路系统是人类活动最为频繁的场所之一,研究路网空间特征与相关环境指标的关系,可为定量分析城市建设过程对城市生态环境的影响以及为城市基础设施规划管理提供方法。对北京市五环内各级道路抽样调查及面向对象的高分辨率遥感影像识别,建立道路空间信息数据库,运用TM影像反演获得地表温度(LST)及归一化植被指数(NDVI),研究4种不同分析网格下城市路网特征与两者的空间相关性。结果表明,在较大分析网格下(4×4),路网空间指标与LST mean及NDVI mean相关性显著;中等网格下,除LST与NDVI的平均值外,路网空间指标还可与两者最小值建立相关性;在较小窗口下(32×32),除平均值与最小值,还可建立特定道路指标与LST max及NDVI max的联系;各路网指标中,单位面积道路总长与LST及NDVI相关性最强;加权道路结点数在8×8和32×32网格分析中,与NDVI的相关性高于该指标未加权值,而结点指标均不适合与LST max建立联系;在各分析网格下,4项道路指标均与NDVI mean呈极显著负相关,表明道路绿地建设规模还不足以对NDVI的强度及分布产生较大影响。