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1.
A study of carbon (C) storage in the 0-0.75-m profile of soils subtending various types of grasslands on the Qinghai-Tibetan Plateau showed that the organic carbon content of the 1,627,000 km2 of such lands in the region reaches 33.52 Pg of C. Organic carbon is mainly stored in the meadow and steppe soils of the Plateau, which combined, represents 23.2 Pg of C stored in organic form. This represents 23.44% of China's total organic soil-stored carbon and 2.5% of the global pool of soil carbon as of 1996. Carbon emissions from the grassland soils were estimated based on the two major modes of emission: (i) natural soil respiration and (ii) shifts in net C flux to/from soil due to land-use changes and their potential influence on organic matter decomposition. Annual soil respiration-driven CO2 emissions from the grassland soils of the plateau reached 1.17 Pg C year(-1), accounting for 26.4% of China's total soil respiration and 1.73% of global soil respiration. Because the grassland area accounts for 1.02% of the global terrestrial land and 16.9% of China's total terrestrial land, this CO2 emission rate is significantly higher than the country's mean annual rate (approx. 4.2 Pg C year(-1)) and even higher than the global mean rate (approx. 68 Pg C year(-1)). In the last 30 years, approximately 3.02 Pg C have been emitted from the grassland soils of the plateau due to land-use changes and grassland degradation. The total CO2 emissions rate from the grassland soils of the plateau reached 1.27 Pg C year(-1). Protecting grasslands on the Qinghai-Tibetan Plateau is of great importance in limiting global climate change.  相似文献   

2.
Soils represent an important reservoir for persistent organic pollutants (POPs) in the terrestrial environment and thus the fate of contaminants deposited to the surface soils is important to understand. Since only a limited number of studies of the vertical distribution of POPs are available in the literature, the purpose of this study was to collect and analyze PCB concentrations in different layers of soil cores taken at agricultural and non-agricultural sites in Sweden. PCB concentrations at the agricultural site were nearly uniform on a dry weight basis throughout the depth considered (0-12 cm) while a distinct gradient with depth was observed at the five non-agricultural sites. On an organic carbon normalized basis, the concentration gradient was maintained at three of the non-agricultural sites while a more uniform distribution was observed at the other two sites. A statistically significant relationship between dry weight soil concentrations and organic carbon content was determined for all PCB congeners in the surface layers (0-1 cm) but not in the deeper layers (4-5 cm, 9-10 cm). These results were interpreted in relation to vertical soil transport processes and then the implications for environmental fate models including soil compartments were discussed.  相似文献   

3.
Lake areas in Chinese urban fringes are under increasing pressure of urbanization. Consequently, the conflict between rapid urban sprawl and the maintenance of water bodies in such areas urgently needs to be addressed. An integrated GIS-based analysis system (IGAS) for supporting land-use management of lake areas in urban fringes was developed in this paper. The IGAS consists of modules of land-use suitability assessment and change/demand analysis, and land evaluation and allocation. Multicriteria analysis and system dynamics techniques are used to assess land-use suitability and forecast potential land-use variation, respectively. Cost approximation and hypothetical development methods are used to evaluate land resource and market values, respectively. A case study implementing the system was performed on the Hanyang Lake area in the urban fringe of Wuhan City, central China, which is under significant urbanization pressure. Five categories of suitability were investigated by analyzing 11 criteria and related GIS data. Two scenarios for potential land-use changes from 2006 to 2020 were predicted, based on a systematic analysis and system dynamics modeling, and a hierarchical land-use structure was designed for the conservation of aquatic ecosystems. The IGAS may help local authorities better understand and address the complex land-use system, and develop improved land-use management strategies that better balance urban expansion and ecological conservation.  相似文献   

4.
A screening model of pesticide leaching loss is described which forms part of a multi-criteria risk-based indicator system called PRoMPT (Pesticide Risk Management and Profiling Tool). The leaching model evaluates pesticide fate in soil for any application rate and time of application (including multiple applications), for any land-based location in the world. It considers a generic evaluative environment with fixed dimensions and soil properties. The soil profile is conceptualised as a number of discrete layers. Equilibrium partitioning between adsorbed and dissolved chemical (based on the organic carbon-water partition coefficient [K(OC)]) is assumed in each time step, in each layer. Non-leaching losses are described using first order kinetics. Drainage is assumed to be uniform throughout the soil profile but varies temporally. The drainage rate, which can be augmented by evapotranspiration-adjusted irrigation, is derived from long-term mean monthly water balance model calculations performed for 30 arc-minute grid cells across the entire ice-free land surface of the earth. Although, such predictions are approximate, they do capture the seasonality and relative magnitude of drainage and allow the model to be applied anywhere, without the need for extensive data compilation. PRoMPT predictions are shown to be consistent with those made by more sophisticated models (PRZM, PELMO and PEARL) for the FOCUS groundwater scenarios.  相似文献   

5.
城区边缘绿色空间深刻地作用于 城市空间结构与生态品质,进而影响绿色低 碳建设目标,然而现实中却为规划建设的薄 弱环节。文章运用文献梳理与案例研究方 法,结合宝鸡南部台塬区规划实践,探讨了 绿色低碳背景下城区边缘绿色空间的规划 思路:尊重自然过程,提升城区边缘绿色空 间内在系统生态功能和外在复合服务功能; 利用区位与环境优势,发掘邻近城区正向关 联的空间环境与产业经济边缘效应。规划 方法展现于相互支撑的三个方面:塑造潜在 可能转化城区外缘绿色空间低碳功效的绿 色空间结构;构筑减少土地利用过程碳足迹的绿色空间用地布局;综合考量城郊游憩与地方 食物供给等绿色产业布局。最后,文章探讨了绿色空间与相关建设用地全覆盖土地利用控制 方法与空间设计导引指向。  相似文献   

6.
To assess the fate of the large amounts of nitrogen (N) brought into the agricultural environment by human activities in the Changjiang River basin, we used [China's county level agricultural database of 1980 and 1990. National Resources and Environmental Data Center, China] and published conversion data to set up a complete N budget for the Changjiang River basin. Sources considered include imported N such as atmospheric deposition, inorganic fertilizer, biological fixation and manure. Dominant losses considered include crop harvests, denitrification of soil nitrate and NH3 volatilization, and the budget was estimated from the difference between all inputs and all outputs. Therefore, the geographic distribution of excess N, considered as lost, by N storage in farmland and N transported to water bodies in Changjiang River basin was analyzed. In the Changjiang River basin, the anthropogenic reactive N has far exceeded the terrestrial bio-fixed N in nature, and human activities have significantly altered the N cycle in this region. The total inputs of N in 1980 and 1990 were 8.0 and 12.9 Tg N, respectively. The total N outputs are 4.41 Tg N in 1980 and 6.85 Tg N in 1990. Thus, the excess N that was stored in farmland was 1.51 Tg N at 1980 and 2.67 Tg N at 1990, respectively, and losses through transportation to water bodies in 1980 was 2.08 and 3.38 Tg N in 1990, respectively. Our research shows that from 1980 to 1990, cultivated land increased 5.9%, grain production increased 30% and N fertilizer-use increased 106%, but the N fertilizer-use efficiency decreased 36%, and the variations in the distribution of N fertilizer-use efficiency, N budgets and N transport to water bodies tended to coincide with each other geographically.  相似文献   

7.
全球气候变化引发的海平面上升对沿海区域的环境和社会经济发展造成巨大破坏。以珠三角广州南沙为研究区域,基于传统、自然增长和规划控制3种土地利用格局预设发展情景,采用PLUS(Patch-generating Land Use Simulation Model)模型模拟各情景下的未来土地利用格局。同时,针对近期(2030年)、中期(2050年)和远期(2100年)3种不同海平面上升叠加风暴潮风险下的土地利用格局脆弱性开展多情景定量化评估,并提出应对策略。结果显示:1)3种土地利用格局发展情景中,传统格局情景能够最有效地应对或缓解海平面上升和风暴潮灾害风险,而自然增长情景应对未来海岸灾害的能力最弱;2)从不同土地利用类型的脆弱性程度来看,城镇建设用地的综合脆弱性最高,而村庄建设用地的综合脆弱性最低;3)根据不同发展情景及灾害风险应采用综合防御、适应及撤退等多种应对策略。综合考虑了未来土地利用格局的多种变化情景、灾害风险及应对策略,能够为滨海城市应对未来海岸灾害的适应性规划提供决策参考。  相似文献   

8.
The importance of soil storage in global carbon cycling is well recognised and factors leading to increased losses from this pool may act as a positive feedback mechanism in global warming. Upland peat soils are usually assumed to serve as carbon sinks, there is however increasing evidence of carbon loss from upland peat soils, and DOC concentrations in UK rivers have increased markedly over the past three decades. A number of drivers for increasing DOC release from peat soils have been proposed although many of these would not explain fine-scale variations in DOC release observed in many catchments.We examined the effect of land use and management on DOC production in upland peat catchments at two spatial scales within the UK. DOC concentration was measured in streams draining 50 small-scale catchments (< 3 km2) in three discrete regions of the south Pennines and one area in the North Yorkshire Moors. Annual mean DOC concentration was also derived from water colour data recorded at water treatment works for seven larger scale catchments (1.5-20 km2) in the south Pennines. Soil type and land use/management in all catchments were characterised from NSRI digital soil data and ortho-corrected colour aerial imagery.Of the factors assessed, representing all combinations of soil type and land use together with catchment slope and area, the proportion of exposed peat surface resulting from new heather burning was consistently identified as the most significant predictor of variation in DOC concentration. This relationship held across all blanket peat catchments and scales.We propose that management activities are driving changes in edaphic conditions in upland peat to those more favourable for aerobic microbial activity and thus enhance peat decomposition leading to increased losses of carbon from these environments.  相似文献   

9.
Mercury (Hg) levels in terrestrial soils are linked to the presence of organic carbon (C). Carbon pools are highly dynamic and subject to mineralization processes, but little is known about the fate of Hg during decomposition. This study evaluated relationships between gaseous Hg emissions from soils and carbon dioxide (CO2) respiration under controlled laboratory conditions to assess potential losses of Hg to the atmosphere during C mineralization. Results showed a linear correlation (r2 = 0.49) between Hg and CO2 emissions in 41 soil samples, an effect unlikely to be caused by temperature, radiation, different Hg contents, or soil moisture. Stoichiometric comparisons of Hg/C ratios of emissions and underlying soil substrates suggest that 3% of soil Hg was subject to evasion. Even minute emissions of Hg upon mineralization, however, may be important on a global scale given the large Hg pools sequestered in terrestrial soils and C stocks.We induced changes in CO2 respiration rates and observed Hg flux responses, including inducement of anaerobic conditions by changing chamber air supply from N2/O2 (80% and 20%, respectively) to pure N2. Unexpectedly, Hg emissions almost quadrupled after O2 deprivation while oxidative mineralization (i.e., CO2 emissions) was greatly reduced. This Hg flux response to anaerobic conditions was lacking when repeated with sterilized soils, possibly due to involvement of microbial reduction of Hg2+ by anaerobes or indirect abiotic effects such as alterations in soil redox conditions. This study provides experimental evidence that Hg volatilization, and possibly Hg2+ reduction, is related to O2 availability in soils from two Sierra Nevada forests. If this result is confirmed in soils from other areas, the implication is that Hg volatilization from terrestrial soils is partially controlled by soil aeration and that low soil O2 levels and possibly low soil redox potentials lead to increased Hg volatilization from soils.  相似文献   

10.
Interest in the application of biochar (charcoal produced during the pyrolysis of biomass) to agricultural land is increasing across the world, recognised as a potential way to capture and store atmospheric carbon. Its interest is heightened by its potential co-benefits for soil quality and fertility. The majority of research has however been undertaken in tropical rather than temperate regions. This study assessed the potential for lump-wood charcoal addition (as a substitute for biochar) to soil types which are typically under arable and forest land-use in North East England. The study was undertaken over a 28 week period and found:
i)
No significant difference in net ecosystem respiration (NER) between soils containing charcoal and those without, other than in week 1 of the trial.
ii)
A significantly higher dissolved organic carbon (DOC) flux from soils containing large amounts of charcoal than from those untreated, when planted with ryegrass.
iii)
That when increased respiration or DOC loss did occur, neither was sufficiently large to alter the carbon sink benefits of charcoal application.
iv)
That charcoal incorporation resulted in a significantly lower nitrate flux in soil leachate from mineral soils.
v)
That charcoal incorporation caused significant increases in soil pH, from 6.98 to 7.22 on bare arable soils when 87,500 kg charcoal/ha was applied.
Consideration of both the carbon sink and environmental benefits observed here suggests that charcoal application to temperate soils typical of North East England should be considered as a method of carbon sequestration. Before large scale land application is encouraged, further large scale trials should be undertaken to confirm the positive results of this research.  相似文献   

11.
Edges mediate the material flux between adjacent systems. This mediating effect of edges is strongly tied to the complexity of the adjacent shapes. Land use within a watershed has a direct impact on the water quality of adjacent aquatic systems. Hydrological processes carry material produced by land-use activities into aquatic ecosystems through the edges of the ecosystem. Therefore, the geometry of aquatic ecosystems theoretically affects the relationship between land use and water quality. This study investigates whether the shape complexity of reservoirs moderates the direct impact of land use on the water quality of adjacent reservoirs. A moderation model was adopted to measure the shape effects, and 153 reservoirs were randomly sampled with a consideration of reservoir size (surface area), geographic location, and data availability. With a focus on urban land use, we used GIS to measure land-use types within a 1 km buffer of reservoir boundaries. The shape complexity of sampled reservoirs was measured using fractal dimensions. Land uses and shape complexity were then regressed to measure water quality parameters such as chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP). Correlation analysis revealed that the shapes of reservoirs are likely to be simple where urban land use dominates the areas close to reservoirs. Use of the standard regression model indicated that the increasing shape complexity of reservoirs significantly reduces the concentration of BOD, COD, and TP within reservoir water. Moderation models for BOD, COD, TN, and TP suggest that shape complexity can considerably relieve the negative impacts on water quality of urban land use in areas adjacent to reservoirs. The results of this study highlight the need to focus on shoreline management in order to mitigate the adverse impacts of land use on lakes and reservoirs.  相似文献   

12.
Forest remnants are vital for the overall heterogeneity and health of rural landscapes. However, deforestation is a significant process afflicting large numbers of agroforested regions of the world. The Maskoutains regional county municipality (RCM) in southern Quebec, Canada, experiences intense deforestation that has reached critical levels. The goal of this study is to develop a geographic cellular automata (GCA) to model land-use change in this region and test the influence of different management scenarios on the fate of the forested remnants. The GCA was built using a 100 m cell size, a Moore neighborhood configuration, a 3 years time step resolution and probabilistic transition rules derived from the comparison of two land-use maps for the years 1999 and 2002. Four groups of management scenarios were tested: (1) status quo (SQ), (2) reduced deforestation (RD), (3) promotion of ligniculture (L), and (4) protection of forest connectivity (CONN). Results indicate that none of the scenarios succeed in maintaining the actual levels of forest area. However, certain scenarios (amongst the RD and CONN), significantly alter the loss of forest areas in the short to mid-term and delay the fragmentation, reduction, and isolation of forest patches.  相似文献   

13.
This paper describes work carried out within the EU-funded FOOTPRINT project to characterize the diversity of European agricultural and environmental conditions with respect to parameters which most influence the environmental fate of pesticides. Pan-European datasets for soils, climate, land cover and cropping were intersected, using GIS, to identify the full range of unique combinations of climate, soil and crop types which characterize European agriculture. The resulting FOOTPRINT European agro-environmental dataset constitutes a large number of polygons (approximately 1,700,000) with attribute data files for i) area fractions of annual crops related to each arable-type polygon (as an indicator of its probability of occurrence); and, ii) area fractions of each soil type in each polygon (as an indicator of its probability of occurrence). A total of 25,044 unique combinations of climate zones, agricultural land cover classes, administrative units and soil map units were identified. The same soil/crop combinations occur in many polygons which have the same climate while the fractions of the soils and arable crops are different. The number of unique combinations of climate, soil and agricultural land cover class is therefore only 7961. 26-year daily meteorological data, soil profile characteristics and crop management features were associated with each unique combination. The agro-environmental scenarios developed can be used to underpin the parameterization of environmental fate models for pesticides and should also have relevance for other agricultural pollutants. The implications for the improvement and further development of risk assessment procedures for pesticides are discussed.  相似文献   

14.
This paper describes relationships between land-use and air quality. Until very recently, strategies directed toward improved air quality relied almost exclusively upon fuel switching and employment of emission control devices. However, air quality can also be influenced through alteration of land-use patterns. Engineers during their education are generally not exposed to land-use and other socio-economic aspects of air-quality management, although federal and state policy maker are increasingly recognizing that exclusive reliance upon emission control devices is not a very satisfactory long range approach. Alteration of land use as it affects the living, working, and transportation patterns must be considered as well.The first two sections of this paper attempt to provide guidelines within which land-use alternatives can be meaningfully evaluated. Air-quality standars and other aspects of air-quality management are described and interpreted within a quantitative cost-benefit framework.The rudiments of urban geography are also provided in order to introduce the readers to the economics and social forces which shape cities. The fundamental purpose is to make technologists aware of the conflict between these forces and plans for arbitrary changes in spatial patterns. Next, energy variables are proposed as a way to meaningfully relate land-use and environmental pollution with society's quest for affluence. The section on meteorology and dispersion models describes and criticizes the modeling tools and simulations currently available for the prediction of pollution dispersion. Finally, an urban simulation is used to integrate the foregoing material. The air-pollution propensities of various land-use alternatives are assessed.Thus a diversity of topics—all with the common thread of relating urban air quality to urban land use—is addressed. Rather than providing ready-made answers, this paper describes useful evaluation tools and provides insight into the complex problems and interactions involved.  相似文献   

15.
Land management to promote forest growth can conserve and sequester a significant amount of terrestrial carbon and thereby reduce the buildup of atmospheric carbon. This study uses geographic information systems (GIS) technology to develop a multi-criteria land use model for Butler County in southwestern Ohio that ranks rural land areas for restorative forest management based on their potential for carbon conservation. Our results identify 161 sites, or 18% of the county study area outside of incorporated urban areas, that have topographic and soil conditions productive for forest growth, and 21% of the mapped area is on transitional (uncultivated and undeveloped) lands that are potentially available for restorative management. The study strongly supports the planned protection of lands along stream corridors; 43% of the transitional lands ranked high potential are within a 100 m stream buffer and 80% are within a 500 m buffer. It also reveals “gaps” between the predicted carbon conservation map and regional plans for conservation, particularly showing the need to consider incorporating woodlots into privately owned farms on flat uplands with deep soil profiles. The study provides a valuable ecological planning resource that prioritizes lands for rural conservation based on their functional contributions to the regional carbon balance.  相似文献   

16.
Catchment Flood Management Plans involve a high-level assessment of current flood risk and attempt to demonstrate how this risk could change with time. An influencing factor will be the changes to rural and urban land use on catchment hydraulics. By assessing a range of land use and urban-growth scenarios catchment wide, a 'catchment flood management plan' can demonstrate the cumulative effect on downstream flood-risk areas. 'Catchment flood management plan' methods also indicate how long-term land-use and climate changes can expose new areas to more frequent flooding. Techniques to assess these issues, up to a 50-year horizon, have been established as part of these pilot studies. In addition to briefly describing how land-use concerns are integrated into such concepts, this paper outlines how flood-management planning must evolve as a dynamic tool, to fulfil an on-going requirement for future development assessment.  相似文献   

17.
韦亚平  潘聪林 《城市规划》2012,(3):76-84,89
基于杭州城西9个街区1339份居民出行数据,利用居民个体属性、出行距离和土地利用等三组变量建构了多项逻辑决策模型,分析街区土地利用变量对通勤方式选择的影响。结论为:在中国高密度城市形态下,由于城区扩张和收入水平提高,形成了以小汽车为主导的混合通勤结构,而小尺度街区、密集路网等土地利用变量则是助长小汽车通勤的诱因;有必要在街区空间尺度上,通过土地利用规划、小汽车使用管制以及公共交通环境设计等综合措施,优化居民的通勤结构。  相似文献   

18.
This study aimed to assess farmers’ perception of soil fertility change and their priorities for soil fertility management techniques for different land use types in Arsamma Watershed, Southwestern Ethiopian Highlands. A three-stage random sampling technique was employed to select the sampled households. A smaller proportion of farmers perceived soil fertility decline in perennial cropland than in annual cropland as the farmers appeared to be less aware of below-ground processes of soil degradation. The farmers used physical, chemical and biological indicators to evaluate soil fertility changes. The rate of soil fertility decline and the occurrence of the contributory factors were land use specific. Increasing fertilizer requirement of croplands and decreasing yield per unit of land were the main indicators of soil fertility decline in annual and perennial cropland, respectively. Farmers’ preference for soil fertility management techniques was also found to depend on the type of land use. Integrated soil fertility management (ISFM) and agroforestry were the top priorities of the farmers, respectively, for annual and perennial cropland management. Farmers lack knowledge of below-ground processes of soil degradation by leaching, nutrient mining and soil acidity; and agricultural extension services should respond to this need. Further, ISFM for annual cropland and agroforestry for perennial cropland need to be encouraged in the study catchment.  相似文献   

19.
Water quality associated with nitrate (NO3-) leaching from agricultural soils is an important environmental issue. This paper describes a new modelling approach to quantitatively evaluate the effect of the use of fertilisers on global nitrate leaching. A global process-based simulation model was previously developed for the nitrogen cycle in terrestrial ecosystems, in which soil inorganic nitrogen in the form of ammonium (NH4+) and NO3- was considered. After introducing data on world fertiliser consumption (FAO, 1995) into the steady-state model, the extent of disturbance to the nitrogen cycle caused by fertilisation was calculated. Although fertilisation resulted in an annual increase in net primary production (NPP, represented as carbon) of 18 Gt year-1, NO3- leaching and gaseous losses of nitrogen oxides and ammonia were also accelerated. Most regions with heavy fertiliser application (over 100 kg ha-1 year-1) showed a high annual leaching load equal to or more than 20 kg ha-1 year-1. About 2.5% of the land area occupied by terrestrial ecosystems suffered a serious leaching load of more than 30 kg ha-1 year-1. Of the total amount of applied fertilisers (138 Tg year-1) 19% was lost to NO3- leaching, 8% to gaseous ammonia, and 3% to gaseous nitrogen oxides. The rest was assumed to be fixed in the ecosystems through vegetation uptake.  相似文献   

20.
Fate of antibiotics during municipal water recycling treatment processes   总被引:8,自引:0,他引:8  
Municipal water recycling processes are potential human and environmental exposure routes for low concentrations of persistent antibiotics. While the implications of such exposure scenarios are unknown, concerns have been raised regarding the possibility that continuous discharge of antibiotics to the environment may facilitate the development or proliferation of resistant strains of bacteria. As potable and non-potable water recycling schemes are continuously developed, it is imperative to improve our understanding of the fate of antibiotics during conventional and advanced wastewater treatment processes leading to high-quality water reclamation. This review collates existing knowledge with the aim of providing new insight to the influence of a wide range of treatment processes to the ultimate fate of antibiotics during conventional and advanced wastewater treatment. Although conventional biological wastewater treatment processes are effective for the removal of some antibiotics, many have been reported to occur at 10-1000 ng L−1 concentrations in secondary treated effluents. These include β-lactams, sulfonamides, trimethoprim, macrolides, fluoroquinolones, and tetracyclines. Tertiary and advanced treatment processes may be required to fully manage environmental and human exposure to these contaminants in water recycling schemes. The effectiveness of a range of processes including tertiary media filtration, ozonation, chlorination, UV irradiation, activated carbon adsorption, and NF/RO filtration has been reviewed and, where possible, semi-quantitative estimations of antibiotics removals have been provided.  相似文献   

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