Source identification for fine aerosols in Mammoth Cave National Park

In this study, positive matrix factorization (PMF) was applied to the chemical composition data of the ambient PM_2.5 collected at the Mammoth Cave National Park, an IMPROVE site in Kentucky. Eight individual carbon fractions, four organic carbons (OCs), pyrolyzed organic carbon (OP) and three elemental carbons (ECs), were provided to the analysis. Nine sources including the well-distinguished gasoline emission and diesel emission were identified. Also, the back trajectories indicated the crustal factor in this study were likely caused by Saharan dust storms in the summer. The apportionment of nine sources was: gasoline emission (6.7%), diesel emission (3.1%), summer secondary sulfate (49.0%), winter secondary sulfate (0.6%), OP-rich secondary sulfate (16.2%), secondary nitrate (2.8%), Intercontinental dust plus soil (4.9%), wood smoke (13.6%), and aged sea salt (3.2%). The results of this study will help regularize the pollution control strategies in rural areas of Kentucky and upper mid-western US while demonstrating the feasibility of applying carbon fractions to the source apportionment of rural upper-Midwestern areas.     

Comparing CO2 Storage and Advection Conditions at Night at Different Carboeuroflux Sites

Anemometer and CO₂ concentration data from temporary campaigns performed at six CARBOEUROFLUX forest sites were used to estimate the importance of non-turbulent fluxes in nighttime conditions. While storage was observed to be significant only during periods of both low turbulence and low advection, the advective fluxes strongly influence the nocturnal CO₂ balance, with the exception of almost flat and highly homogeneous sites. On the basis of the main factors determining the onset of advective fluxes, the ‘advection velocity’, which takes net radiation and local topography into account, was introduced as a criterion to characterise the conditions of storage enrichment/depletion. Comparative analyses of the six sites showed several common features of the advective fluxes but also some substantial differences. In particular, all sites where advection occurs show the onset of a boundary layer characterised by a downslope flow, negative vertical velocities and negative vertical CO₂ concentration gradients during nighttime. As a consequence, vertical advection was observed to be positive at all sites, which corresponds to a removal of CO₂ from the ecosystem. The main differences between sites are the distance from the ridge, which influences the boundary-layer depth, and the sign of the mean horizontal CO₂ concentration gradients, which is probably determined by the source/sink distribution. As a consequence, both positive and negative horizontal advective fluxes (corresponding respectively to CO₂ removal from the ecosystem and to CO₂ supply to the ecosystem) were observed. Conclusive results on the importance of non-turbulent components in the mass balance require, however, further experimental investigations at sites with different topographies, slopes, different land covers, which would allow a more comprehensive analysis of the processes underlying the occurrence of advective fluxes. The quantification of these processes would help to better quantify nocturnal CO₂ exchange rates.     

美国国家科学基金会(NSF)地学学部(GEO)基金资助战略分析

美国国家科学基金会（NSF）是国际上具有重要影响的资助基础科学研究的政府基金机构，对促进美国基础科学研究的发展和保持世界领先地位做出了重要贡献。其对基础研究的资助政策、方向遴选、评审程序、经费分配、管理机制等，形成了一套行之有效的模式，对其它国家的基础研究政府资助机构具有借鉴和示范意义。在分析美国NSF近3年经费状况及其领域分配情况、近5年项目受理与批准情况、近12年项目评议情况的基础上，重点分析了地学学部（GEO）的近期重点资助领域、近3年按照NSF的整体优先领域和战略产出目标的经费分配情况、近10年按科学处的经费分配情况及变化趋势、各科学处2004—2006财政年度经费状况与重点资助领域、近10年项目的资助率与资助强度变化情况等。NSF地学学部是美国政府资助以大学为主的地学基础研究的主要渠道，其经费约占美国政府资助地学基础研究经费的62%。对NSF的基金项目资助战略，特别是对其地学学部项目的资助情况予以全面分析，对我国相关部门的管理工作有重要参考价值和借鉴意义。     

Tree integration in homestead farms in southeast Nigeria: propositions and evidence

This paper contributes to wider debates on the dominant factors determining the emergence and sustainability of intermediate systems of forest management in developing countries. The theoretical framework and propositions for analysing tree integration in homestead farms are presented, with reference to southeast Nigeria. The paper argues that, first, at the household level, livelihood strategies constitute the main determinant of the decision to integrate trees in homestead farms. Secondly, induced innovation has a wider and more significant role at the community level than at the household level in encouraging the integration of trees in farms. Thirdly, the sustainability of observed patterns of tree integration is influenced by the interaction of environmental, ecological, political, economic and social factors. Based on these propositions, the paper analyses the internal (household) and external (wider community) factors influencing tree integration in homestead farms in southeast Nigeria.     

A Comparison of Methods to Predict Soil Surface Texture in an Alluvial Basin

Surface soil texture controls many important ecological, hydrological, and geomorphic processes in arid regions and is therefore important from a land‐management perspective. Soil survey efforts have traditionally fulfilled this need, but they are constrained by the size, remoteness, and inaccessibility of many arid regions, which renders simple field measurements prohibitively expensive. This article compares several different predictive soil‐mapping techniques with a sparse data set in order to develop surficial soil texture maps. Our results suggest that data collected at the landscape scale can be used as input to predictive soil‐mapping techniques to create maps of soil texture at higher fidelity and a fraction of the cost than would be required using traditional methods.     

Geography's Profile in Public Debate “Inside the Beltway” and the National Academies*

Geographers continue to engage in public debate “inside the Beltway” by participation within and through federal agencies and through the National Research Council. Several examples illustrate the level and kind of this engagement, which has been concentrated on environmental and spatial data and analysis themes. Most professional geographers have the opportunity to engage in this form of public debate through participation in the activities of the National Research Council. The level of this participation has been surprisingly strong, given the small size of the community of professional geographers, and has helped to shape both U.S. and international research agendas relevant to geographic research. Participation, however, is concentrated in a few programs and individuals, raising questions about the sustainability of geography's voice in this public activity.     

A cladoceran-based paleolimnological assessment of the impact of forest harvesting on four lakes from the central interior of British Columbia, Canada

To investigate the impact of forest harvesting on lake ecosystems, six lakes (four impact, two reference) from central British Columbia, Canada were assessed using cladoceran remains preserved in the lake sediment cores. Two temporal resolutions were analyzed: a decadal scale for the past 70 years, and a high-resolution scale (2 year intervals for ten years before and after harvesting). Three lakes which experienced forestry activity in their watersheds in the early 1960s, and one lake which experienced forestry activityin the mid 1970s, showed subtle but statistically significant changes in cladoceran species composition following forest harvesting (analysis of similarity tests) at the decadal scale, whereas only two of these lakes showed significant changes at the higher resolution. These changes may be due to increased nutrient levels that might be associated with forest harvesting. The two reference lakes, which had not experienced any known large-scale anthropogenic watershed disturbances in the past century, showed no significant shifts in the cladoceran species assemblages at either temporal scale.     

H<Subscript>2</Subscript>-rich and Hydrocarbon Gas Recovered in a Deep Precambrian Well in Northeastern Kansas

In late 2005 and early 2006, the WTW Operating, LLC (W.T.W. Oil Co., Inc.) #1 Wilson well (T.D. = 5772 ft; 1759.3 m) was drilled for 1826 ft (556.6 m) into Precambrian basement underlying the Forest City Basin in northeastern Kansas. Approximately 4500 of the 380,000 wells drilled in Kansas penetrate Precambrian basement. Except for two previous wells drilled into the arkoses and basalts of the 1.1-Ga Midcontinent Rift and another well drilled in 1929 in basement on the Nemaha Uplift east of the Midcontinent Rift, this well represents the deepest penetration into basement rocks in the state to date. Granite is the typical lithology observed in wells that penetrate the Precambrian in the northern Midcontinent. Although no cores were taken to definitively identify lithologies, well cuttings and petrophysical logs indicate that this well encountered basement metamorphic rocks consisting of schist, gneiss, and amphibolitic gneiss, all cut by aplite dikes. The well was cased and perforated in the Precambrian, and then acidized. After several days of swabbing operations, the well produced shows of low-Btu gas, dominated by the non-flammable component gases of nitrogen (20%), carbon dioxide (43%), and helium (1%). Combustible components include methane (26%), hydrogen (10%), and higher molecular-weight hydrocarbons (1%). Although Coveney and others [Am. Assoc. Petroleum Geologists Bull., v. 71, no, 1, p. 39–48, 1987] identified H₂-rich gas in two wells located close to the Midcontinent Rift in eastern Kansas, this study indicates that high levels of H₂ may be a more widespread phenomenon than previously thought. Unlike previous results, the gases in this study have a significant component of hydrocarbon gas, as well as H₂, N₂, and CO₂. Although redox reactions between iron-bearing minerals and groundwater are a possible source of H₂ in the Precambrian basement rocks, the hydrocarbon gas does not exhibit the characteristics typically associated with proposed abiogenic hydrocarbon gases from Precambrian Shield sites in Canada, Finland, and South Africa. Compositional and isotopic signatures for gas from the #1 Wilson well are consistent with a predominantly thermogenic origin, with possible mixing with a component of microbial gas. Given the geologic history of uplift and rifting this region, and the major fracture systems present in the basement, this hydrocarbon gas likely migrated from source rocks and reservoirs in the overlying Paleozoic sediments and is not evidence for abiogenic hydrocarbons generated in situ in the Precambrian basement.     

Influence of advection on scales of ecological studies in a coastal equilibrium flow

Spatial patterns are generated as a result of the coupling between biogeochemical and physical processes and the ability to capture and reproduce patchiness is crucial for the better comprehension of an ecosystem and its response to external perturbations. A 1D reaction–diffusion–advection equation is used to investigate the formation of patterns and relevant time and spatial scales and thus define an approach for the determination of a critical domain size that allows differentiation of the role of local and internal cycling from advective fluxes across the open boundaries in a shallow coastal ecosystem. By using a 3D numerical model, in conjunction with an extensive field data set, it is shown that domain sizes must be larger than this critical value in order to capture the patterns generated within the system. For smaller domains, the evolution of the system is controlled by transport processes across the boundaries misleading the interpretation of the internal ecological dynamics. The study of the influence of boundary fluxes on ecological patchiness was motivated by the need to define the size of the domain necessary for the assessment of the impact of a sewage outflow on a coastal regime.     

An Automated GIS Procedure for Delineating River and Lake Boundaries

Digitization of river and lake boundaries is an essential task in several hydrologic studies, which, in most cases, is performed manually by using aerial photographs. This paper presents an automatic geographic information system (GIS) procedure for delineating river and lake boundaries using aerial photographs. The GIS procedure is based on supervised classification of aerial photographs by using the National Hydrography Dataset (NHD) for creating training areas. Four study areas – Lake Palestine in Texas, Brazos River in Texas, Neuse River in North Carolina, and Snake River in Idaho – are used to demonstrate the approach. The results from the automatic boundary delineation process are evaluated by comparing them to manually digitized boundaries. The boundaries delineated by the automatic procedure matched the manually digitized boundaries with an overall difference of less than five percent in terms of area measurement. Besides saving about 85 percent of manual labor, the GIS procedure provides a consistent way of delineating water bodies, and provides estimation of river channel widths, which, in conjunction with existing NHD data, can be used to estimate average flow depths. Supplementing the regional scale NHD data with local scale attributes such as channel width and depth may lead to increased use of NHD in local scale studies.