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111.
Rita D. Winkler Diana M. Allen Tim R. Giles Brian A. Heise R. Dan Moore Todd E. Redding Dave L. Spittlehouse Xiaohua Wei 《水文研究》2021,35(5):e14123
Over the past 35 years, the Upper Penticton Creek (UPC) Watershed Experiment has supported forest hydrology research in south-central British Columbia (BC), Canada. This paper provides a synthesis of research results, highlights the challenges facing UPC and identifies new research directions. Clearcutting approximately 50% of two small, snow-dominated (Dfb Koppen classification) watersheds advanced the timing of snowmelt-generated high flows and decreased late-summer low flows, relative to predictions based on pre-treatment regressions. Changes in high flows did not have a significant effect on stream channels due to low stream power, coarse substrate, and limited riparian disturbance. Changes in summer low flows reduced modelled useable fish habitat by 20%–50%. Evaporation averaged 52% of the annual precipitation in the mature forest, was reduced to 30% in a clearcut, and recovered to 40% and 47% in a 10 and 25 year-old stand, respectively. Groundwater recharge to the bedrock was estimated at 19% of annual precipitation, indicating that, even with the large uncertainty associated with this estimate, deep groundwater should not be ignored in the water balance. Suspended sediment, turbidity, and colour increased post-logging; however, chemical surface water quality did not change. Aquatic community structure changed post-logging; and although this affected the processing of organic matter, the effects on habitat quality were considered minimal. The information gained at UPC has supported provincial policies, management guidelines, forest stewardship plans and watershed risk assessments. The undisturbed control watershed, re-growing treatment watersheds and ongoing long-term hydrometric monitoring continue to provide opportunities for future research addressing issues such as the effects of young forests on streamflow and hydrologic recovery, and the influence of climate change on the hydrologic regime. 相似文献
112.
Colin Neal Brian Reynolds James W. Kirchner Phil Rowland Dave Norris Darren Sleep Alan Lawlor Clive Woods Sarah Thacker Hayley Guyatt Colin Vincent Kathryn Lehto Simon Grant Jeremy Williams Margaret Neal Heather Wickham Sarah Harman Linda Armstrong 《水文研究》2013,27(17):2531-2539
This scientific briefing announces the availability of a new multi‐element high‐frequency water quality data set that is openly accessible to the research community. The data set comprises up to 2 years of 7‐hourly water quality data for two streams and one rainfall site in the Upper Severn catchment at Plynlimon in Mid‐Wales. The measurements cover 50 analytes ranging from H+ to U and spanning six orders of magnitude in concentration, including major, minor and trace elements as well as nutrients, and they complement decades of weekly measurements of the same analytes at the Upper Severn. Together, the weekly and 7‐hourly time series provide a unique data set for studying both long‐term trends and short‐term dynamics. The data show complex behaviour over a wide range of timescales, challenging our understanding of catchment processes and informing future modelling efforts. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
113.
The nutrient rich fractions in wastewater originating from human urine and can be recovered as solids for more efficient recycling, facilitated handling and storage for reuse in agriculture. Freezing and thawing can be used to concentrate the urine nutrients. Phosphorus (P) and nitrogen (N) can be precipitated as struvite [(Mg,Ca)(K,NH4)(PO4)·6H2O] by adding MgO and additional nitrogen can be recovered by using zeolites. The zeolite in this study was pretreated in two ways: (i) washed and (ii) washed and thermally treated. The P recovery was high (> 97%) and the N recovery was ca. 50 to 60%. There was no significant difference in the nitrogen recovery among the different pretreated zeolites or between the pretreated and the untreated zeolite. Freezing had a positive effect on the nutrient concentration. The acute toxicity of the supernatants was tested on Daphnia magna to evaluate the possibilities of discharging the remaining supernatants to a recipient. The supernatants from the frozen treatments and from the unfrozen and washed zeolites were much less toxic than those of the original urine. The minerals acted as slow‐release fertilizers in climate chamber tests on spring wheat. 相似文献
114.
Michael A. Dopita Lee Armus Lisa J. Kewley Jeff A. Rich Dave Sanders Phillip N. Appleton Ben H. P. Chan Vassilis Charmandaris Aaron S. Evans David T. Frayer Justin H. Howell Hanae Inami Joseph A. Mazzarella Andreea Petric Sabrina Stierwalt Jason Surace 《Astrophysics and Space Science》2011,333(1):225-239
This paper describes a pilot study into the spectral energy distribution (SED) fitting and the derivation of physical parameters for 19 galaxies observed as part of the Great Observatories All-sky LIRG Survey (GOALS) survey as observed with the Spitzer Space Telescope. For this we have used the pan-spectral fitting tools developed in a series of papers by Dopita and his co-workers. We show that the standard Lee and Draine ??astronomical silicate?? model cannot provide a good fit to the silicate absorption features as observed in the heavily dust-extinguished (A V??50 mag.) starbursts. We have derived an empirical fit to the ??starburst silicate?? absorption in these objects. This absorption curve is consistent with the silicate grains being systematically larger in starburst environments than in the local Galactic interstellar medium. We demonstrate the sensitivity of the SED fitting to each of the fitted parameters, and derive these parameters for those galaxies which do not have an embedded AGN. This technique is simple and provides reasonably robust and uniform parameters for the starburst, especially as far as the star formation rate, population of old stars, compactness of the starburst region and total foreground extinction are concerned. However, the chemical abundances and the optical extinction cannot be reliably determined by this analysis, and optical SEDs will also be required to provide a complete characterization of the starburst region and of the surrounding galaxy. 相似文献
115.
Kelsey E. O’Brien Dave Risk Daniel Rainham Anne Marie O’Beirne-Ryan 《Environmental Earth Sciences》2014,72(7):2607-2620
Radon gas is a human health hazard; long-term exposure to high radon concentrations through inhalation is the second leading cause of lung cancer. Nova Scotia has been previously identified as a potential high risk region because of the geology. As such, the gas transport through Halifax’s fine grained leucomonzogranite (FGL) unit of the South Mountain Batholith needed to be quantified to further remediation efforts. Using controlled laboratory experiments, four different soil columns were created using the Halifax Regional Municipality’s (HRM) highest producing field tills and bedrock. Permeability, diffusivity, radon-222 gas concentrations, and gas transit time/speed were measured in both dry tills (field moisture) and wet tills (simulated rain event moisture). Columns with HRM till displayed the highest radon concentrations, and were less permeable with additional moisture. Radon diffusivity calculated from CO2 was 7.52 × 10?8 m2 (dry), and 3.37 × 10?8 m2 (wet); diffusivity calculated from 222Rn was 7.30 × 10?7 m2 (dry), and 6.47 × 10?7 m2 (wet). The average FGL transit time in a 60 cm column was 3.57 days (dry), and 3.82 days (wet). Locally this study presents two different methods for diffusivity calculations, for a unit lacking previous diffusivity information. The radon gas concentrations and transport speeds quantified the transport mechanisms within the till. Globally, the correlation between soil moisture, and radon/permeability values was established using these results. The link between diffusivity and permeability was also confirmed using field tills. Implications were made for building foundations, as well as the depth and type of material necessary to reduce radon gas from reaching the surface. 相似文献
116.
117.
P. Protopapas J. M. Giammarco L. Faccioli M. F. Struble R. Dave C. Alcock 《Monthly notices of the Royal Astronomical Society》2006,369(2):677-696
We present a methodology to discover outliers in catalogues of periodic light curves. We use a cross-correlation as the measure of 'similarity' between two individual light curves, and then classify light curves with lowest average 'similarity' as outliers. We performed the analysis on catalogues of periodic variable stars of known type from the MACHO and OGLE projects. This analysis was carried out in Fourier space and we established that our method correctly identifies light curves that do not belong to those catalogues as outliers. We show how an approximation to this method, carried out in real space, can scale to large data sets that will be available in the near future such as those anticipated from the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) and Large Synoptic Survey Telescope (LSST). 相似文献
118.
119.
Sascha Fl?gel Geoffrey Parkin Dave Pollard Wolf-Christian Dullo Thomas Wagner 《Climate Dynamics》2011,37(7-8):1565-1573
Freshwater discharge is one main element of the hydrological cycle that physically and biogeochemically connects the atmosphere, land surface, and ocean and directly responds to changes in pCO2. Nevertheless, while the effect of near-future global warming on total river runoff has been intensively studied, little attention has been given to longer-term impacts and thresholds of increasing pCO2 on changes in the partitioning of surface and subsurface flow paths across broad climate zones. These flow paths and their regional responses have a significant role for vegetation, soils, and nutrient leaching and transport. We present climate simulations for modern, near-future (850?ppm), far-future (1880?ppm), and past Late Cretaceous (1880?ppm) pCO2 levels. The results show large zonal mean differences and the displacement of flows from the surface to the subsurface depending on the respective pCO2 level. At modern levels the ratio of deeper subsurface to near-surface flows for tropical and high northern latitudes is 1:4.0 and 1:0.5, respectively, reflecting the contrast between permeable tropical soils and the areas of frozen ground in high latitudes. There is a trend toward increased total flow in both climate zones at 850?ppm, modeled to be increases in the total flow of 34 and 51%, respectively, with both zones also showing modest increases in the proportion of subsurface flow. Beyond 850?ppm the simulations show a distinct divergence of hydrological trends between mid- to high northern latitudes and tropical zones. While total wetting reverses in the tropics beyond 850?ppm due to reduced precipitation, with average zonal total runoff decreasing by 46% compared to the 850?ppm simulation, the high northern latitude zone becomes slightly wetter with the average zonal total runoff increasing by a further 3%. The ratio of subsurface to surface flows in the tropics remains at a level similar to the present day, but in the high northern latitude zone the ratio increases significantly to 1:1.6 due to the loss of frozen ground. The results for the high pCO2 simulations with the same uniform soil and vegetation cover as the Cretaceous are comparable to the results for the Cretaceous simulation, with higher fractions of subsurface flow of 1:5.4 and 1:5.6, respectively for the tropics, and 1:2.2 and 1:1.6, respectively for the high northern latitudes. We suggest that these fundamental similarities between our far future and Late Cretaceous models provide a framework of possible analogous consequences for (far-) future climate change, within which the integrated human impact over the next centuries could be assessed. The results from this modeling study are consistent with climate information from the sedimentary record which highlights the crucial role of terrestrial-marine interactions during past climate change. This study points to profound consequences for soil biogeochemical cycling, with different latitudinal expressions, passing of climate thresholds at elevated pCO2 levels, and enhanced export of nutrients to the ocean at higher pCO2. 相似文献
120.
Rob A. Holman K. Todd Holland Dave M. Lalejini Steven D. Spansel 《Ocean Dynamics》2011,61(11):1927-1935
We investigate the issues and methods for estimating nearshore bathymetry based on wave celerity measurements obtained using
time series imagery from small unmanned aircraft systems (SUAS). In contrast to time series imagery from fixed cameras or
from larger aircraft, SUAS data are usually short, gappy in time, and unsteady in aim in high frequency ways that are not
reflected by the filtered navigation metadata. These issues were first investigated using fixed camera proxy data that have
been intentionally degraded to mimic these problems. It has been found that records as short as 50 s or less can yield good
bathymetry results. Gaps in records associated with inadvertent look-away during unsteady flight would normally prevent use
of the required standard Fast Fourier Transform methods. However, we found that a full Fourier Transform could be implemented
on the remaining valid record segments and was effective if at least 50% of total record length remained intact. Errors in
image geo-navigation were stabilized based on fixed ground fiducials within a required land portion of the image. The elements
of a future method that could remove this requirement were then outlined. Two test SUAS data runs were analyzed and compared
to survey ground truth data. A 54-s data run at Eglin Air Force Base on the Gulf of Mexico yielded a good bathymetry product
that compared well with survey data (standard deviation of 0.51 m in depths ranging from 0 to 4 m). A shorter (30.5 s) record
from Silver Strand Beach (near Coronado) on the US west coast provided a good approximation of the surveyed bathymetry but
was excessively deep offshore and had larger errors (1.19 m for true depths ranging from 0 to 6 m), consistent with the short
record length. Seventy-three percent of the bathymetry estimates lay within 1 m of the truth for most of the nearshore. 相似文献