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21.
Bird-watching is an increasingly popular leisure activity. Previous research has taken for granted the identity of people who watch birds, often categorised by their level of skilled practice as ‘dude’, ‘birder’ or ‘twitcher’. Feminist geographers encourage us to explore identity work as an outcome of the reciprocal relationships between practices and place. Our feminist approach illustrates that the practices of bird-watching are always much more than categorising birds as species. This paper illustrates how the practices of bird-watching are integral to the making and remaking of sense of place as ‘home’ and ‘away’, to sustain identities beyond accepted categories of ‘dude’, ‘birder’ and ‘twitcher’. The creation and application of different types of ‘bird-lists’ helps to explain the ways in which practices of bird-watching facilitate making sense of place as simultaneously ‘home’, ‘away’ and habitat, as well as the identity work of home-maker, citizen-scientist and tourist. Our insights into these leisure practices of bird-watching are drawn from analysis of data gathered from 21 people who actively bird-watch and reside on the South Coast, New South Wales, Australia by combining research methods of talking, walking, drawing and photography. 相似文献
22.
Sandrine Vinatier Pascal Rannou Carrie M. Anderson Bruno Bézard Remco de Kok Robert E. Samuelson 《Icarus》2012,219(1):5-12
We utilized aerosol extinction coefficient inferred from Cassini/CIRS spectra in the far and mid infrared region to derive the extinction cross-section near an altitude of 190 km at 15°S (from far-IR) and 20°S (from mid-IR). By comparing the extinction cross section that are derived from observations with theoretical calculations for a fractal aggregate of 3000 monomers, each having a radius of 0.05 μm, and a fractal dimension of 2, we are able to constrain the refractive index of Titan’s aerosol between 70 and 1500 cm?1 (143 and 6.7 μm). As the real and imaginary parts of the refractive index are related by the Kramers–Kronig equation, we apply an iterative process to determine the optical constants in the thermal infrared. The resulting spectral dependence of the imaginary index displays several spectral signatures, some of which are also seen for some Titan’s aerosol analogues (tholins) produced in laboratory experiments. We find that Titan’s aerosols are less absorbent than tholins in the thermal infrared. The most prominent emission bands observed in the mid-infrared are due to CH bending vibrations in methyl and methylene groups. It appears that Titan’s aerosols predominantly display vibrations implying carbon and hydrogen atoms and perhaps marginally nitrogen. In the mid infrared, all the aerosol spectral signatures are observed at three additional latitudes (56°S, 5°N and 30°N) and in the 193–274 km altitude range, which implies that Titan’s aerosols exhibit the same chemical composition in all investigated latitude and altitude regions. 相似文献
23.
Scott C. Brooks Carrie L. Miller Ami L. Riscassi Kenneth A. Lowe Johnbull O. Dickson Grace E. Schwartz 《水文研究》2021,35(8):e14344
East Fork Poplar Creek (EFPC) is a mercury (Hg) contaminated creek in east Tennessee, USA. Stream restoration activities included the initiation of a flow management programme in 1996 in which water from a nearby lake was pumped to the head of the creek. We conducted regular water sampling for 2 years along the length of EFPC during active flow management and for 5 years after flow management stopped. Total Hg and total monomethylmercury (MMHg) concentration and flux decreased in the uppermost reaches of EFPC that were closest to the point of water addition. Most water quality parameters, including DOC concentration, remained unchanged after flow management termination. Nevertheless, SUVA254, a measure of dissolved organic matter (DOM) composition, increased and coincided with increased dissolved Hg (HgD) concentration and flux and decreased Hg solid-water partitioning coefficients throughout EFPC. Higher SUVA254 and HgD concentration have potential implications for bioavailability and MMHg production. Total and dissolved MMHg concentrations increased in lower reaches of EFPC after the end of flow management and these increases were most pronounced during spring and early summer when biota are more susceptible to exposure and uptake. A general warming trend in the creek after active flow management ended likely acted in concert with higher HgD concentration to promote higher MMHg concentration. Total and dissolved MMHg concentrations were positively correlated with water temperature above a threshold value of 10°C. Concentration changes for Hg and MMHg could not be accounted for by changes in creek discharge that accompanied the cessation of flow management. In addition to the changing DOM composition in-stream, other watershed-scale factors likely contributed to the observed patterns, as these changes occurred over months rather than instantaneously after flow management stopped. Nevertheless, similar changes in MMHg have not been observed in a tributary to EFPC. 相似文献
24.
Trihalomethanes (THMs) are formed by the reaction of reactive chlorine species, such as hypochlorous acid, with naturally occurring organic matter. THMs are also found in soil and groundwater at sites where releases of organic solvents have occurred and are often ascribed to the biological degradation chlorinated solvents. This research was prompted by the discovery of THMs in groundwater at a site with a reported discharge of sodium hypochlorite. This paper reports the formation of THMs in soil and water resulting from the reaction of sodium hypochlorite with soil. Soil samples were reacted with dilute bleach solutions (sodium hypochlorite) and the solution collected for analysis by gas chromatography/mass spectrometry. All THMs were detected in test samples after treatment. Concentrations of chloroform up to 2450 µg/L in aqueous extracts were detected compared to 40 µg/L in bleach and 1 µg/L in blank samples. 相似文献
25.
The 3-D radar reflectivity data has become increasingly important for use in data assimilation
towards convective scale numerical weather prediction as well as next generation precipitation estimation.
Typically, reflectivity data from multiple radars are objectively analyzed and mosaiced onto a regional
3-D Cartesian grid prior to being assimilated into the models. One of the scientific issues associated
with the mosaic of multi-radar observations is the synchronization of all the observations. Since radar
data is usually rapidly updated (～every 5--10 min), it is common in current multi-radar mosaic techniques
to combine multiple radar' observations within a time window by assuming that the storms are steady within
the window. The assumption holds well for slow evolving precipitation systems, but for fast evolving
convective storms, this assumption may be violated and the mosaic of radar observations at different times
may result in inaccurate storm structure depictions. This study investigates the impact of synchronization
on storm structures in multiple radar data analyses using a multi-scale storm tracking algorithm. 相似文献
26.
Multiple factors causing Holocene lake-level change in monsoonal and arid central Asia as identified by model experiments 总被引：1，自引：0，他引：1
Lake-level records provide a rich resource of information about past changes in effective moisture, but water-balance fluctuations
can be driven by a number of different climate variables and it is often difficult to pinpoint their exact cause. This understanding
is essential, however, for reconciling divergent paleo-records or for making predictions about future lake-level variations.
This research uses a series of models, the NCAR CCSM3, a lake energy-balance and a lake water-balance model, to examine the
reasons for lake-level changes in monsoonal Asia and arid central Asia between the early (8.5 ka), middle (6.0 ka) and late
(ca. 1800 AD) Holocene. Our results indicate that the components of the lake water balance responsible for lake-level changes
varied by region and through time. High lake levels at 8.5 and 6.0 ka in the monsoon region were caused by the combined effects
of low lake evaporation and high precipitation. The low lake evaporation resulted from low winter solar radiation and high
summer cloud cover. Precipitation associated with the mid-latitude westerlies increased from the early to middle Holocene
and maintained high lake levels throughout most of arid central Asia ca. 6 ka. The modeled evolution of lake level in arid
central Asia from the mid to late Holocene was spatially heterogeneous, due to different sensitivities of the northern and
southern parts of the region to seasonally-changing insolation, particularly regarding the duration of lake ice cover. The
model results do not suggest that precipitation and lake evaporation changes compete with one another in forcing lake-level
change, as has been hypothesized. 相似文献
27.
Sources of uncertainty in estimating stream solute export from headwater catchments at three sites 
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下载免费PDF全文 Ruth D. Yanai Naoko Tokuchi John L. Campbell Mark B. Green Eiji Matsuzaki Stephanie N. Laseter Cindi L. Brown Amey S. Bailey Pilar Lyons Carrie R. Levine Donald C. Buso Gene E. Likens Jennifer D. Knoepp Keitaro Fukushima 《水文研究》2015,29(7):1793-1805
Uncertainty in the estimation of hydrologic export of solutes has never been fully evaluated at the scale of a small‐watershed ecosystem. We used data from the Gomadansan Experimental Forest, Japan, Hubbard Brook Experimental Forest, USA, and Coweeta Hydrologic Laboratory, USA, to evaluate many sources of uncertainty, including the precision and accuracy of measurements, selection of models, and spatial and temporal variation. Uncertainty in the analysis of stream chemistry samples was generally small but could be large in relative terms for solutes near detection limits, as is common for ammonium and phosphate in forested catchments. Instantaneous flow deviated from the theoretical curve relating height to discharge by up to 10% at Hubbard Brook, but the resulting corrections to the theoretical curve generally amounted to <0.5% of annual flows. Calibrations were limited to low flows; uncertainties at high flows were not evaluated because of the difficulties in performing calibrations during events. However, high flows likely contribute more uncertainty to annual flows because of the greater volume of water that is exported during these events. Uncertainty in catchment area was as much as 5%, based on a comparison of digital elevation maps with ground surveys. Three different interpolation methods are used at the three sites to combine periodic chemistry samples with streamflow to calculate fluxes. The three methods differed by <5% in annual export calculations for calcium, but up to 12% for nitrate exports, when applied to a stream at Hubbard Brook for 1997–2008; nitrate has higher weekly variation at this site. Natural variation was larger than most other sources of uncertainty. Specifically, coefficients of variation across streams or across years, within site, for runoff and weighted annual concentrations of calcium, magnesium, potassium, sodium, sulphate, chloride, and silicate ranged from 5 to 50% and were even higher for nitrate. Uncertainty analysis can be used to guide efforts to improve confidence in estimated stream fluxes and also to optimize design of monitoring programmes. © 2014 The Authors. Hydrological Processes published John Wiley & Sons, Ltd. 相似文献
28.
Jesse Carrie Hamed Sanei Fariborz Goodarzi Gary Stern Feiyue Wang 《International Journal of Coal Geology》2009,77(3-4):416-423
The particulate organic matter in < 63 µm surface sediments from the Mackenzie River and its main tributaries was studied using Rock-Eval pyrolysis and organic petrology. The organic matter in the sediments is dominated by refractory residual organic carbon (RC) of mainly terrigenous nature, as indicated by abundant inertinite, vitrinite, and type III kerogen. Sediments from the tributaries contained significantly more algal-derived organic matter than from the main channel of the river, highlighting the importance of low-energy system dynamics in the tributaries, which allows modest algal production, more accumulation, and better preservation of autochthonous organic matter. This is particularly true for tributaries fed by lacustrine systems, which showed the highest S1 and S2 fractions, and consequently higher total particulate organic carbon (POC) in the basin. Organic petrology of the sediment samples confirms abundant liptinitic materials (i.e., fat-rich structured algae, spores and pollen, cuticles, and resins). Forest fire and coal deposits are also confirmed to contribute to the basin. Assuming that suspended and fine surfacial sediments have a similar OC composition, the Mackenzie River is estimated to deliver a total POC flux of 1.1 Mt C/yr to its delta, of which 85% is residual carbon with liptinitic OC (S1 + S2) and S3 accounting for another 9% and 6%, respectively. 相似文献
29.
Natalie E. Sievers Carrie A. Menold Marty Grove Matthew A. Coble 《International Geology Review》2017,59(5-6):621-638
ABSTRACTPrevious study of subducted continental crust within the Luliang Shan terrane in Northwest China has documented metasomatic formation of thick, hydrated phengite + garnet-rich selvages at the interface between mafic eclogite blocks and quartzofeldspathic host gneiss. Whole rock concentrations of Cs and Ba within the selvage are enriched by two orders of magnitude relative to the eclogite blocks and host gneiss. We performed in situ ion microprobe analyses of Li, Be, B, Rb, Sr, Cs and Ba and δ11B of phengite within the Luliang Shane terrane to better constrain the source(s) of the infiltrating fluid. The phengite within the selvage are enriched in Li, Cs and Ba and yield δ11B values between ?30‰ and ?9‰, values that are lower than mantle values. High Ba/Rb, Cs/Rb coupled with low B/Be, B/Li and highly negative δ11B values indicate that the high-pressure fluid that formed the selvage was derived from highly devolatilized rocks within the subduction channel. In contrast, muscovite, which crystallized in the adjacent host gneiss during a subsequent lower pressure phase of fluid infiltration at approximately 0.9 GPa depths, has much lower Li, Cs and Ba relative to the high-pressure phengite. These retrograde muscovite have very high concentrations of B (up to 5500 ppm) and Be (up to 50 ppm) and high (?2 to +8‰) δ11B values that are consistent with crystallization from a fluid derived from shallower and less devolatilized regions of the subduction zone. Additional host gneiss samples, regionally distributed and kilometres away from the studied area lack the B-rich signature and indicate that the late stage fluids were likely localized to the region near the studied traverse. 相似文献
30.
The post-glacial history of the Great Lakes has involved several changes in lake levels throughout the latest Pleistocene and Holocene, resulting from the changing position of the retreating Laurentide ice sheet, outlet incision and isostatic rebound. The final lowering of lake levels occurred at approximately 7600 14C yr BP, after which lake levels began to rise again to the Nipissing highstand at approximately 4700 14C yr BP. During this time of rising lake levels, black bands of iron sulfide were being formed in the sediments of all five of the Great Lakes. These bands signify suboxic to anoxic conditions, at least within the sediments and possibly at the sediment-water interface, during the middle Holocene warm interval. During this interval, the climate was warmer and drier than present, possibly resulting in the occasional absence of seasonal turnover in the lakes. We examined a series of piston cores from northern Lakes Michigan and Huron and found that the black bands are correlatable among cores taken from within the same basin. The observation that the banding can be correlated suggests a basin-wide cause, near-bottom or sub-bottom anoxia in the northern Michigan and northern Huron sediments during the mid-Holocene warm period. The sedimentary and geochemical processes in the Great Lakes during the middle Holocene warm interval are good indicators of possible future scenarios for the lakes as a result of global warming, as 21st-century temperatures are predicted to reach similar levels due to increased concentrations of greenhouse gases. 相似文献