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1.
Previous studies of the efficiency of Chinese electricity industry have been limited in providing insights regarding policy implications of inherent trade‐offs of economic and environmental outcomes. This study proposes a modified data envelopment analysis method combined with materials balance principle to estimate ecological and cost efficiency in the Chinese electricity industry. The economic cost and ecological impact of energy input reallocation strategies for improving efficiency are identified. The possible impacts of pollution taxes upon the levels of sulfur dioxide (SO2) emissions are assessed. Estimation results show that (1) both energy input costs and SO2 could be reduced through increasing technical efficiency. (2) It is possible to adjust energy input mix to attain ecological efficiency, and, correspondingly, SO2 would be reduced by 15%. (3) The Chinese electricity industry would reduce its unit cost by 9% if optimal ecological efficiency is attained and reduce its unit pollution by 13% if optimal cost efficiency is attained, implying that there are positive ecological synergy effects associated with energy cost savings and positive economic synergy effects associated with SO2 pollution reductions. (4) Estimated shadow costs of SO2 reduction are very high, suggesting that, in the short term, the Chinese electricity industry should pursue cost efficiency instead of ecological efficiency, since alternative abatement activities are less costly and some of the abatement cost could be further offset by energy input cost savings. (5) There would be no significant difference between the impacts of pollution discharge fees and pollution taxes on SO2 emissions levels because of the relatively low pollution tax rate.  相似文献   

2.
The issue of CO2 emission has become a major issue causing greater concern to the global economies due to its potential environmental effects and impact on climate change. In order to address this issue and mitigate its harmful effects on the environment, it is imperative to reduce CO2 emission drastically and fairly quickly. In this paper we have been focusing on alternative linkage methodologies for measuring CO2 emission, which entails linkages among the productive sectors in an economy. Methods, dealing with inter-sectoral carbon linkage measures can be summarized into two main categories, i.e. (a) the concept of traditional backward and forward linkages and (b) hypothetical extraction method (HEM). The (HEM) method is used to hypothetically extract a sector from an economic system and examine the influence of this extraction on other sectors in an economy. In this study we will evolve the environmentally extended input–output model to measure the CO2 emission linkages among the productive sectors in Italy using data obtained in 2011. Using the HEM method, the backward linkage emission and forward linkage emission are calculated to characterize the behavior of these sectors. The results obtained from these measures will enable us to formulate hypothesis about the direction and strength of the relationship between various linkages and will also indicate which key CO2 emitter sector measures are most similar and which are most dissimilar. According to the size of the various linkage measures, all sectors of the economy can be grouped into four categories. These measures allow us to examine and identify those sectors, which deserve more consideration in formulating mitigation policies.  相似文献   

3.
China's remarkable economic growth in the last 3 decades has brought about big improvements in quality of life while simultaneously contributing to serious environmental problems. The aim of all economic activities is, ultimately, to provide the population with products and services. Analyzing environmental impacts of consumption can be valuable for illuminating underlying drivers for energy use and emissions in society. This study applies an environmentally extended input‐output analysis to estimate household environmental impact (HEI) of urban Beijing households at different levels of development. The analysis covers direct and indirect energy use and emissions of carbon dioxide (CO2), sulfur dioxide (SO2), and nitrogen oxide (NOx). On the basis of observations of how HEI varies across income groups, prospects for near‐future changes in HEI are discussed. Results indicate that in 2007, an urban resident in Beijing used, on average, 52 gigajoules of total primary energy supply. The corresponding annual emissions were 4.2 tonnes CO2, 27 kilograms SO2, and 17 kilograms NOx. Of this, only 18% to 34% was used or emitted by the households directly. While the overall expenditure elasticity of energy use is around 0.9, there is a higher elasticity of energy use associated with transport. The results suggest that significant growth in HEI can be expected in the near future, even with substantial energy efficiency improvements.  相似文献   

4.
The electric power industry plays a critical role in the economy and the environment, and it is important to examine the economic, environmental, and policy implications of current and future power generation scenarios. However, the tools that exist to perform the life cycle assessments are either too complex or too aggregated to be useful for these types of activities. In this work, we build upon the framework of existing input‐output (I‐O) models by adding data about the electric power industry and disaggregating this single sector into additional sectors, each representing a specific portion of electric power industry operations. For each of these disaggregated sectors, we create a process‐specific supply chain and a set of emission factors that allow calculation of the environmental effects of that sector's output. This new model allows a much better fit for scenarios requiring more specificity than is possible with the current I‐O model.  相似文献   

5.
Industrial ecology (IE) methodologies, such as input/output or material flow analysis and life cycle assessment (LCA), are often used for the environmental evaluation of circular economy strategies. Up to now, an approach that utilizes these methods in a systematic, integrated framework for a holistic assessment of a geographic region's sustainable circular economy potential has been lacking. The approach developed in this study (IE4CE approach) combines IE methodologies to determine the environmental impact mitigation potential of circular economy strategies for a defined geographic region. The approach foresees five steps. First, input/output analysis helps identify sectors with high environmental impacts. Second, a refined analysis is conducted using material flow and LCA. In step 3, circular strategies are used for scenario design and evaluated in step 4. In step 5, the assessment results are compiled and compared across sectors. The approach was applied to a case study of Switzerland, analyzing 8 sectors and more than 30 scenarios in depth. Carbon capture and storage (CCS) from waste incineration, biogas and cement production, food waste prevention in households, hospitality and production, and the increased recycling of plastics had the highest mitigation potential. Most of the scenarios do not influence each other. One exception is the CCS scenarios: waste avoidance scenarios decrease the reduction potential of CCS. A combination of scenarios from different sectors, including their impact on the CCS scenario potential, led to an environmental impact mitigation potential of 11.9 Mt CO2-eq for 2050, which equals 14% of Switzerland's current consumption-based impacts.  相似文献   

6.
As cities represent the microcosms of global environmental change, it is very important for the global sustainable development by decoupling environmental pressure from economic growth on city level. In this paper, the municipality of Chongqing in China is employed as a case to show whether the decoupling of environmental pressures from economic growth has occurred in cities undergoing rapid economic growth; what is the level of decoupling; and what causes the observed degree of decoupling. Results show the following. (1) During the period of 1999–2010, decoupling from economic growth has been absolute for the emissions of SO2, soot, and waste water, while it has been relative for total energy consumption, emissions of CO2 and solid waste. (2) Compared with the period 2000–2005, decoupling level improved for all the six environmental pressures in the period 2005–2010. (3) Compared with China and other three municipalities of China, the overall decoupling level of Chongqing is above China’s average while below those of Beijing and Shanghai. (4) During the period 1999–2000, technological change was the dominate factor for decoupling Chongqing’s environmental pressure from economic growth, as it contributed 131.4%, 134.6%, 99.9%, 97.7%, 104.5% and 54.9% to the decoupling of total energy consumption, emissions of CO2, SO2, soot, waste water and solid waste, respectively; while economic structural change had very tiny effect to the decoupling of emissions of soot and SO2, and it even had negative effect to that of total energy consumption, and emissions of CO2 and waste water. Based on the above observations, we explain the difference in decoupling levels for different environmental pressures and suggest approaches for policy-makers on further promoting decoupling environmental pressure from economic growth.  相似文献   

7.
Empirical evidence based on integrated environmental monitoring including physical, chemical and biological variables is essential for evaluating the ecosystem benefits of costly emission reduction policies. The international multidisciplinary ICP IM (International Cooperative Programme on Integrated Monitoring of Air Pollution Effects on Ecosystems) programme studies the integrated effects of air pollution and climate change on ecosystems in unmanaged and calibrated forested catchments. We calculated site-specific annual input-output budgets for sulphate (SO4) and total inorganic nitrogen (TINNO3-N + NH4-N) for 17 European ICP IM sites in 1990–2012. Temporal trends for input (deposition) and output (runoff water) fluxes and the net retention/net release of SO4 and TIN were also analysed. Large differences in the input and output fluxes of SO4 and TIN reflect important gradients of air pollution effects in Europe, with the highest deposition and runoff water fluxes at IM sites located in southern Scandinavia and in parts of Central and Eastern Europe and the lowest fluxes at more remote sites in northern European regions. A significant decrease in the total (wet + dry) deposition of non-marine SO4 and bulk deposition of TIN was found at 90% and 65% of the sites, respectively. Output fluxes of non-marine SO4 in runoff decreased significantly at 65% of the sites, indicating positive effects of the international emission abatement actions in Europe during the last 20 years. Catchments retained SO4 in the early and mid-1990s, but this shifted towards a net release in the late 1990s, which may be due to the mobilization of legacy S pools accumulated during times of high atmospheric SO4 deposition. Despite decreased deposition, TIN output fluxes and retention rates showed a mixed response with both decreasing (9 sites) and increasing (8 sites) trend slopes, and trends were rarely significant. In general, TIN was strongly retained in the catchments not affected by natural disturbances. The long-term annual variation in net releases for SO4 was explained by variations in runoff and SO4 concentrations in deposition, while a variation in TIN concentrations in runoff was mostly associated with a variation of the TIN retention rate in catchments. The net release of SO4 from forest soils may delay the recovery from acidification for surface waters and the continued enrichment of nitrogen in catchment soils poses a threat to terrestrial biodiversity and may ultimately lead to a higher TIN runoff through N-saturation. Continued monitoring and further evaluations of mass balance budgets are thus needed.  相似文献   

8.
This article proposes a linear programming model that is based on the wastewater treatment input‐output model (W2IO) to identify the lowest‐emission choice among alternative feasible options for wastewater treatment; this model can be considered as an application of the waste input‐output linear programming model (WIO‐LP) to wastewater issues. Using the data of the Tokyo metropolitan W2IO table, I apply this model to obtain the optimal wastewater treatment options under alternative scenarios. The Pareto frontiers of environmental loads are derived to show the trade‐off relationships among various types of environmental load and the effect of the introduction of high‐temperature incineration of dewatered sludge on the generation of environmental loads. The main conclusion of the study is that when all three types of environmental load (landfill level, global warming potential, and chemical oxygen demand) are considered, the introduction of high‐temperature incineration causes the widening of the Pareto frontier of environmental loads and also causes it to move closer to the origin.  相似文献   

9.
Bioenergy as well as bioenergy with carbon capture and storage are key options to embark on cost‐efficient trajectories that realize climate targets. Most studies have not yet assessed the influence on these trajectories of emerging bioeconomy sectors such as biochemicals and renewable jet fuels (RJFs). To support a systems transition, there is also need to demonstrate the impact on the energy system of technology development, biomass and fossil fuel prices. We aim to close this gap by assessing least‐cost pathways to 2030 for a number of scenarios applied to the energy system of the Netherlands, using a cost‐minimization model. The type and magnitude of biomass deployment are highly influenced by technology development, fossil fuel prices and ambitions to mitigate climate change. Across all scenarios, biomass consumption ranges between 180 and 760 PJ and national emissions between 82 and 178 Mt CO2. High technology development leads to additional 100–270 PJ of biomass consumption and 8–20 Mt CO2 emission reduction compared to low technology development counterparts. In high technology development scenarios, additional emission reduction is primarily achieved by bioenergy and carbon capture and storage. Traditional sectors, namely industrial biomass heat and biofuels, supply 61–87% of bioenergy, while wind turbines are the main supplier of renewable electricity. Low technology pathways show lower biochemical output by 50–75%, do not supply RJFs and do not utilize additional biomass compared to high technology development. In most scenarios the emission reduction targets for the Netherlands are not met, as additional reduction of 10–45 Mt CO2 is needed. Stronger climate policy is required, especially in view of fluctuating fossil fuel prices, which are shown to be a key determinant of bioeconomy development. Nonetheless, high technology development is a no‐regrets option to realize deep emission reduction as it also ensures stable growth for the bioeconomy even under unfavourable conditions.  相似文献   

10.
李竞  侯丽朋  唐立娜 《生态学报》2021,41(22):8845-8859
改革开放以来,中国经济迅猛发展,但大气污染等环境问题日益突出。进入21世纪,我国通过颁布实施多项大气污染防治政策,将京津冀及周边地区、长三角地区、珠三角地区等大气污染较严重的区域划定为重点区域,针对性制定治污措施和实施减排工程,努力推动区域环境空气质量改善。基于2000-2019年我国31个省(自治区、直辖市)(以下简称31个省份)GDP,以及SO2、PM10、NO2三项大气污染物浓度数据,利用环境库兹涅茨曲线(EKC,Environmental Kuznets Curve)模型,对31个省份和京津冀及周边地区、长三角地区、珠三角地区的经济增长情况、大气污染物浓度演变以及二者之间的关系进行了系统全面的分析评估。研究结果显示:(1)近年来实施的各项大气污染防治政策,特别是2013年以来颁布实施的《大气污染防治行动计划》《打赢蓝天保卫战三年行动计划》,推动环境空气质量改善的同时,促进了经济发展与环境保护长期关系协调性逐步增强,除NO2浓度呈U型外,31个省份SO2浓度、PM10浓度与人均GDP的EKC曲线呈倒U型和倒N型,并处于快速下降阶段。(2)京津冀及周边地区SO2浓度与人均GDP呈倒U型,且处于快速下降阶段;PM10和NO2浓度均呈现U型关系,且均处于上升期。(3)长三角地区SO2、PM10浓度与人均GDP呈现倒U型和U型,但均处于下降阶段;NO2浓度与人均GDP无相关关系。(4)珠三角地区SO2、PM10和NO2浓度与人均GDP均呈现倒U型关系,且均处于下降阶段。为此,建议"十四五"期间我国政府要继续实施新一轮的大气污染防治行动计划,聚焦机动车NOx污染管控,大力推动NO2浓度稳步下降,以实现我国环境空气质量持续改善,为统筹经济高质量发展和生态环境高水平保护奠定坚实基础。  相似文献   

11.
In Norway, the boreal forest offers a considerable resource base, and emerging technologies may soon make it commercially viable to convert these resources into low‐carbon biofuels. Decision makers are required to make informed decisions about the environmental implications of wood biofuels today that will affect the medium‐ and long‐term development of a wood‐based biofuels industry in Norway. We first assess the national forest‐derived resource base for use in biofuel production. A set of biomass conversion technologies is then chosen and evaluated for scenarios addressing biofuel production and consumption by select industry sectors. We then apply an environmentally extended, mixed‐unit, two‐region input?output model to quantify the global warming mitigation and fossil fuel displacement potentials of two biofuel production and consumption scenarios in Norway up to 2050. We find that a growing resource base, when used to produce advanced biofuels, results in cumulative global warming mitigation potentials of between 58 and 83 megatonnes of carbon dioxide equivalents avoided (Mt‐CO2‐eq.‐avoided) in Norway, depending on the biofuel scenario. In recent years, however, the domestic pulp and paper industry—due to increasing exposure to international competition, capacity reductions, and increasing production costs—has been in decline. In the face of a declining domestic pulp and paper industry, imported pulp and paper products are required to maintain the demand for these goods and thus the greenhouse gas (GHG) emissions of the exporting region embodied in Norway's pulp and paper imports reduce the systemwide benefit in terms of avoided greenhouse gas emissions by 27%.  相似文献   

12.
Global environmental and resource problems ask for new ways of managing the production and consumption of resources. The implementation of new paradigms, such as the circular economy, requires decision‐makers at multiple levels to make complex decisions. For this, clear analyses and modeling of scenarios are of utmost importance. Meanwhile, as the sophistication of databases and models increases so does the need for user‐friendly tools to use them. The RaMa‐Scene web platform reduces these barriers by allowing users to visualize easily diverse impacts of implementing circular‐economy interventions. This online web platform makes use of the multi‐regional environmentally extended input–output database EXIOBASE version 3 in monetary units, which has been modified to show explicit transactions of raw materials from recycling activities.  相似文献   

13.
This review aims at holistically analyzing the environmental problems associated with nitrous oxide (N2O) emissions by evaluating the most important sources of N2O and its environmental impacts. Emissions from wastewater treatment processes and the industrial production of nitric and adipic acid represent nowadays the most important anthropogenic point sources of N2O. Therefore, state-of-the-art strategies to mitigate the generation and release to the atmosphere of this greenhouse and O3-depleting gas in the waste treatment and industrial sectors are also reviewed. An updated review of the end-of-the-pipe technologies for N2O abatement, both in the waste treatment and industrial sectors, is herein presented and critically discussed for the first time. Despite the consistent efforts recently conducted in the development of cost-efficient and eco-friendly N2O abatement technologies, physical/chemical technologies still constitute the most popular treatments for the control of industrial N2O emissions at commercial scale. The recent advances achieved on biological N2O abatement based on heterotrophic denitrification have opened new opportunities for the development of eco-friendly alternatives for the treatment of N2O emissions. Finally, the main limitations and challenges faced by these novel N2O abatement biotechnologies are identified in order to pave the way for market implementation.  相似文献   

14.
The resource‐development trajectory of developed countries after the Industrial Revolution of the eighteenth and nineteenth centuries can be portrayed as an “environmental mountain” (EM). It is important for developing countries to decouple their resource use from economic growth and tunnel through the EM. In this study, we embedded the decoupling indicators for resource use and waste emissions into EM curves to quantify China's progress in tunneling through the EM over a specific time period. Five case studies regarding the conditions required for decoupling energy consumption, crude steel production, cement production, CO2 emissions, and SO2 emissions from economic growth in China were conducted. The results indicated that during 1985–2010 the trajectories of energy consumption, and CO2 and SO2 emissions in China met the requirements for tunneling through the EM, but the trajectories of cement and steel production did not. Based on these results, suggestions regarding China's environmental policies are provided to enable the country to tunnel through the EM.  相似文献   

15.
A hybrid approach combining life cycle assessment and input‐output analysis was used to demonstrate the economic and environmental benefits of current and future improvements in agricultural and industrial technologies for ethanol production in Brazilian biorefineries. In this article, three main scenarios were evaluated: first‐generation ethanol production with the average current technology; the improved current technology; and the integration of improved first‐ and second‐generation ethanol production. For the improved first‐generation scenario, a US$1 million increase in ethanol demand can give rise to US$2.5 million of total economic activity in the Brazilian economy when direct and indirect purchases of inputs are considered. This value is slightly higher than the economic activity (US$1.8 million) for an energy equivalent amount of gasoline. The integration of first‐ and second‐generation technologies significantly reduces the total greenhouse gas emissions of ethanol production: 14.6 versus 86.4 grams of carbon dioxide equivalent per megajoule (g CO2‐eq/MJ) for gasoline. Moreover, emissions of ethanol can be negative (–10.5 g CO2‐eq/MJ) when the system boundary is expanded to account for surplus bioelectricity by displacement of natural gas thermal electricity generation considering electricity produced in first‐generation optimized biorefineries.  相似文献   

16.
The environmental situation related to the thermal power basin of Kostolac for the most part represents the result of the influence of the thermal power plants (TPPs) of Kostolac A, Kostolac B, and the open-pit lignite mine. The quality of air is monitored by continuously measuring concentrations of the overall precipitation matters and gases such as CO2, SO2, NOx, CO, and O3. Values significantly exceeding the legal limits have been found for pollutants in the surroundings of the TPPs Kostolac A and B and in the direction of dominant winds. The paper analyzes the impact of different scenarios of emission of harmful matters from the blocks of TPPs Kostolac A and B on the quality of air in this part of Serbia. The Gaussian model has been used to evaluate dispersion of gas substances and suspended particulates as well as parameters related to the surroundings. Calculations have been made relating to ground-level concentrations of sulfur dioxide, nitrogen oxide, and suspended particles at varying distances from the emission source.  相似文献   

17.
Industrial emissions of SO2 and NOx, resulting in the formation and deposition of sulfuric and nitric acids, affect the health of both terrestrial and aquatic ecosystems. Since the mid-late 20th century, legislation to control acid rain precursors in both Europe and the US has led to significant declines in both SO4–S and H+ in precipitation and streams. However, several authors noted that declines in streamwater SO4–S did not result in stoichiometric reductions in stream H+, and suggested that observed reductions in base cation inputs in precipitation could lessen the effect of air pollution control on improving stream pH. We examined long-term precipitation chemistry (1978–2010) from nearly 30 sites in the US and Europe that are variably affected by acid deposition and that have a variety of industrial and land-use histories to (1) quantify trends in SO4–S, H+, NH4–N, Ca, and NO3–N, (2) assess stoichiometry between H+ and SO4–S before and after 1990, and (3) examine regional synchrony of trends. We expected that although the overall efforts of developed countries to reduce air pollution and acid rain by the mid-late 20th century would tend to synchronize precipitation chemistry among regions, geographically varied patterns of fossil fuel use and pollution control measures would produce important asynchronies among European countries and the United States. We also expected that control of particulate versus gaseous emission, along with trends in NH3 emissions, would be the two most significant factors affecting the stoichiometry between SO4–S and H+. Relationships among H+, SO4–S, NH4–N, and cations differed markedly between the US and Europe. Controlling for SO4–S levels, H+ in precipitation was significantly lower in Europe than in the US, because (1) alkaline dust loading from the Sahara/Sahel was greater in Europe than the US, and (2) emission of NH3, which neutralizes acidity upon conversion to NH4 +, is generally significantly higher in Europe than in the US. Trends in SO4–S and H+ in precipitation were close to stoichometric in the US throughout the period of record, but not in Europe, especially eastern Europe. Ca in precipitation declined significantly before, but not after 1990 in most of the US, but Ca declined in eastern Europe even after 1990. SO4–S in precipitation was only weakly related to fossil fuel consumption. The stoichiometry of SO4–S and H+ may be explained in part by emission controls, which varied over time and among regions. Control of particulate emissions reduces alkaline particles that neutralize acid precursors as well as S-containing particulates, reducing SO4–S and Ca more steeply than H+, consistent with trends in the northeastern US and Europe before 1990. In contrast, control of gaseous SO2 emissions results in a stoichiometric relationship between SO4–S and H+, consistent with trends in the US and many western European countries, especially after 1991. However, in many European countries, declining NH3 emissions contributed to the lack of stoichiometry between SO4–S and H+.Recent reductions in NOx emissions have also contributed to declines in H+ in precipitation. Future changes in precipitation acidity are likely to depend on multiple factors including trends in NOx and NH3 emission controls, naturally occurring dust, and fossil fuel use, with significant implications for the health of both terrestrial and aquatic ecosystems.  相似文献   

18.
The economic and ecological aspects of a social system are coherently linked and can be examined by its material and energy flows. In this study, we used the material flow analysis (MFA) to model the material input and output of the Wujin District of Changzhou City, Jiangsu Province in China. It was revealed that: (1) total material input and material input per capita increased with economic development, while the total material output and material output per capita decreased consistently; (2) except for water, the total material input continued to increase. Input of solid materials grew faster than that of gaseous materials, while the total material output declined. The gas output accounted for the largest proportion of the output resulting in primary environmental pollution as burned fossil fuel; (3) water use in agriculture continued with an increasing trend while that in industrial and residential sectors decreased per capita. The total wastewater discharge and wastewater discharge per capita decreased with a faster decreasing rate of residential wastewater discharge followed by industrial wastewater discharge; (4) material input per unit GDP fluctuated and material output per unit GDP decreased. A decreasing trend in both water use and wastewater discharge per unit GDP was disclosed. These results suggest that the efficiency of resource use in the Wujin District has improved. This weakened the direct link between economic development and environmental deterioration. Additionally, we discussed the harmonic development between environment and economy. Potential limitations of MFA’s application were also discussed. It is suggested that effective measures should be taken for the enforcement of circular economic strategies and the construction of a resource-saving economy __________ Translated from Acta Ecologica Sinica, 2006, (8): 2578–2586 [译自:生态学报]  相似文献   

19.
城市森林在吸收、滞留大气污染物,改善城市生态环境方面具有重要意义。以大庆市6种常见绿化树种为研究对象,采用水洗-滤膜法和熏气试验探究不同树种对总悬浮颗粒物(TSP)、大颗粒物(PM>10)、粗颗粒物(PM3—10)和细颗粒物(PM1—3)的滞留规律以及对大气中SO2、NO2的消减效果。研究结果表明:(1)不同树种的滞尘能力差异显著(P<0.05),对TSP的滞留量从大到小依次为:油松(3.82±0.40)g/m2>红瑞木(1.45±0.12)g/m2>紫丁香(1.22±0.17)g/m2>梣叶槭(1.21±0.13)g/m2>大叶杨(0.93±0.17)g/m2>旱柳(0.54±0.14)g/m2;(2)树种间对不同颗粒物的滞留量具有显著差异(P<0.05),供试树种对不同粒径颗粒物滞留的质量占比表现...  相似文献   

20.
The geographic distributions of two common species of epiphytic lichens,Phaeophyscia limbata (Poelt) Kashiw. andLecanora pulverulenta Müll. Arg., on city park trees in the Osaka Plain and their relation to the distribution of SO2 and NO2 was examined. The concentrations of SO2 and NO2 are greater in the central area of this plain, and decrease with distance from the center. The frequency ofL. pulverulenta is lowest in the central area, and increases gradually toward the periphery. In contrast, the frequency ofP. limbata is highest in the intermediate area, and lower in the central and peripheral areas, i.e. at intermediate SO2 and NO2 concentrations. We conclude thatL. pulverulenta is more useful thanP. limbata as a bioindicator of air pollutants such as SO2 and NO2.  相似文献   

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