Assessing the role of alkaline soils on the carbon cycle at a playa site     

Emma L. Yates  Angela M. Detweiler  Laura T. Iraci  Brad M. Bebout  Christopher P. McKay  Kathleen Schiro  Edwin J. Sheffner  Cheryl A. Kelley  Jovan M. Tadić  Max Loewenstein 《Environmental Earth Sciences》2013,70(3):1047-1056

Alkaline soils occupy approximately 5 % of the Earth’s land surface (7 million km), and this may increase due to the global trend towards increasing desertification, yet the extent to which these soils modulate carbon dynamics on regional and global scales is inadequately studied and poorly understood. Railroad Valley (RRV) playa (Nevada, USA) is a semi-arid playa with highly alkaline soils (pH > 10) and no vegetation. The extreme, alkaline environment and absence of vascular vegetation make RRV an ideal site to investigate the role of physiochemical processes of soil-atmosphere CO₂ exchange. Both field and laboratory investigations were conducted. This work shows how the atmospheric CO₂ mixing ratio decreases at nighttime at RRV playa to a value well below the average global background CO₂ concentration. Laboratory investigations using soil samples collected at RRV playa confirmed that CO₂ uptake by RRV playa soils occurs when temperatures are decreased. Both field and laboratory studies suggest that the alkaline RRV soil acts as a CO₂ reservoir during colder periods, such as at nighttime. These results highlight the importance of investigating carbon dynamics in previously understudied environments. Given how little information is available on the CO₂ flux in desert and semi-arid alkaline ecosystems lacking vegetation, our findings draw attention to these environments as becoming increasingly important for carbon fluxes on regional and global scales.  相似文献   

Citywide distribution of lead and other element in soils and indoor dusts in Syracuse,NY     

A. Hunt  D.L. Johnson  D.A. Griffith  S. Zitoon 《Applied Geochemistry》2012

Associations between Pb, Zn, Fe and Mn in soils and indoor dusts in urban Syracuse, NY have been investigated at different levels of spatial aggregation. The concentrations of these elements of interest (EOI) in 3566 soil samples were mapped across the city to investigate variations in concentration potentially associated with specific city locations. Indoor floor dust loadings for the EOI determined at 433 residences were mapped in a similar fashion. Pearson product correlation coefficients at different levels of soil sample aggregation (individual sampling points, block group averages, and census tract (CT) averages), consistently demonstrated a strong correlation between soil Pb and Zn concentrations. Correlations between Pb and both Fe and Mn soil concentrations were also significant. However, the correlation between the Fe and Mn floor dust loadings was much stronger than that for soil, as were the correlations between the Pb and both the Fe and Mn dust loadings. The correlation between the Fe and Zn floor dust loadings was far less significant. Surprisingly, most of the correlations between the paired EOI in the dusts and soils at the individual homes were mostly not statistically significant. The two correlations of any significance, and these were between the Pb in soil and the Pb in the dust, and between Pb in dust and Zn in soil.  相似文献   

Editorial     

Kamlesh Lulla  M Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(7)

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The Landsat 8 is ready for geospatial science and technology researchers and practitioners     

Kamlesh Lulla  M. Duane Nellis  Brad Rundquist 《国际地球制图》2013,28(3)

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Imputing forest carbon stock estimates from inventory plots to a nationally continuous coverage     

Barry Tyler Wilson  Christopher W Woodall  Douglas M Griffith 《Carbon balance and management》2013,8(1):1-15

The U.S. has been providing national-scale estimates of forest carbon (C) stocks and stock change to meet United Nations Framework Convention on Climate Change (UNFCCC) reporting requirements for years. Although these currently are provided as national estimates by pool and year to meet greenhouse gas monitoring requirements, there is growing need to disaggregate these estimates to finer scales to enable strategic forest management and monitoring activities focused on various ecosystem services such as C storage enhancement. Through application of a nearest-neighbor imputation approach, spatially extant estimates of forest C density were developed for the conterminous U.S. using the U.S.’s annual forest inventory. Results suggest that an existing forest inventory plot imputation approach can be readily modified to provide raster maps of C density across a range of pools (e.g., live tree to soil organic carbon) and spatial scales (e.g., sub-county to biome). Comparisons among imputed maps indicate strong regional differences across C pools. The C density of pools closely related to detrital input (e.g., dead wood) is often highest in forests suffering from recent mortality events such as those in the northern Rocky Mountains (e.g., beetle infestations). In contrast, live tree carbon density is often highest on the highest quality forest sites such as those found in the Pacific Northwest. Validation results suggest strong agreement between the estimates produced from the forest inventory plots and those from the imputed maps, particularly when the C pool is closely associated with the imputation model (e.g., aboveground live biomass and live tree basal area), with weaker agreement for detrital pools (e.g., standing dead trees). Forest inventory imputed plot maps provide an efficient and flexible approach to monitoring diverse C pools at national (e.g., UNFCCC) and regional scales (e.g., Reducing Emissions from Deforestation and Forest Degradation projects) while allowing timely incorporation of empirical data (e.g., annual forest inventory).  相似文献   

Galaxy Evolution tool: Construction and Applications     

Yeshe Fenner  Brad K. Gibson  Marco Limongi 《Astrophysics and Space Science》2002,281(1-2):537-538

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Investigation of groundwater flow in karst areas using component separation of natural potential measurements     

Z. Wanfang  Barry F. Beck  J. Brad Stephenson 《Environmental Geology》1999,37(1-2):19-25

 The natural (electrical) potential (NP) method – also known as self-potential, spontaneous potential and streaming potential (SP) – has been used to locate areas of groundwater flow in karst terrane. NP is the naturally occurring voltage at the ground surface resulting from ambient electrical currents within the earth. The measurement of NP can be used to characterize groundwater flow in karst terrane because electrical potential gradients are generated by the horizontal flow of water along fractures or conduits and the vertical infiltration of water into fractures or shafts. NP data from a site on the Mitchell Plain of southern Indiana, USA, revealed that NP data can be decomposed into three components: topographic effect, residual NP and noise. At this site, NP was inversely proportional to elevation, but the correlation varied with time. The topographic correction factor varied from –2.5 to –1.2 mV/m (NP change per unit elevation increase), with an average linear correlation coefficient (R) of 0.95. Because the site slopes toward an adjacent creek that is the local groundwater discharge zone, one possible explanation for this effect is a streaming-potential mechanism generated by groundwater movement toward the creek. The residual NP data revealed three negative anomalies at the survey area. Two of them coincide with sinkholes. A part of the third anomaly is coincident with a small valley, and concentrated infiltration does occur at this elevation in other valleys at the site, as evidenced by the existence of sinkholes. However, the dispersed, low-magnitude nature of the third anomaly does not prove the existence of concentrated groundwater recharge activity. Received: 18 March 1998 · Accepted: 27 April 1998  相似文献   

Echelle spectroscopy of Ca ii HK activity in Southern Hemisphere planet search targets     

C. G. Tinney  Chris McCarthy  Hugh R. A. Jones  R. Paul Butler  Brad D. Carter  Geoffrey W. Marcy  Alan J. Penny 《Monthly notices of the Royal Astronomical Society》2002,332(3):759-763

We present the results of ultraviolet echelle spectroscopy of a sample of 59 F, G, K and M stars from the Anglo-Australian Planet Search target list. Ca  ii activity indices, which are essential in the interpretation of planet detection claims, have been determined for these stars and placed on the Mount Wilson R '_HK system.  相似文献   

Is the initial mass function of low surface brightness galaxies dominated by low-mass stars?     

Hyun-chul Lee  Brad K. Gibson  Chris Flynn  Daisuke Kawata  Michael A. Beasley 《Monthly notices of the Royal Astronomical Society》2004,353(1):113-117

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Radio and X-ray signatures of merging neutron stars     

Brad M. S. Hansen †  Maxim Lyutikov† 《Monthly notices of the Royal Astronomical Society》2001,322(4):695-701

We describe the possible electromagnetic signals expected from the magnetospheric interactions of a neutron star binary prior to merger. We find that both radio and X-ray signals of detectable strength are possible. We discuss possible links with the phenomenon of gamma-ray bursts (GRBs) and describe the prospects for direct detection of these signals in searches for radio and X-ray transients.  相似文献