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Soonkie Nam Marte Gutierrez Panayiotis Diplas John Petrie Alexandria Wayllace Ning Lu Juan Jorge Muñoz 《Engineering Geology》2010,110(1-2):1-10
The soil water characteristic curve (SWCC), also known as soil water retention curve (SWRC), describes the relationship between water content and soil suction in unsaturated soils. Water content and suction affect the permeability, shear strength, volume change and deformability of unsaturated soils. This paper presents results of the laboratory determination of the SWCC for soil samples obtained from the riverbank of the Lower Roanoke River in North Carolina. Six different testing methods were used to establish the SWCC including the filter paper, dewpoint potentiameter, vapor equilibrium, pressure plate, Tempe cell and osmotic methods. It is concluded that each suction measurement technique provides different measurable ranges of suction values, and the combined results from the different tests provide continuous SWCCs. Three widely available models were also shown to adequately fit the experimental SWCC data, particularly for matric suction values under 1500 kPa. These results will be valuable to practitioners in deciding which methods to use to establish the SWCC, and which empirical relationship to use for modeling the SWCC of riverbank soils. 相似文献
2.
Nicholas R. de Sieyes Kevan M. Yamahara Adina Paytan Alexandria B. Boehm 《Estuaries and Coasts》2011,34(2):256-268
Two 14-day experiments conducted in the dry summer (July 2006) and wet winter (March 2007) seasons, respectively, examined
tidal, wave-driven, and seasonal variability of submarine groundwater discharge (SGD) at Stinson Beach, CA, using natural
radium tracers. Tide stage, tide range, breaker height, and season each explained a significant degree of radium variability
in the surf zone. A mass balance of excess radium in the surf zone was used to estimate SGD for each season, confirming larger
discharge rates during the wet season. Our results indicate median groundwater discharge rates of 6 to 8 L min−1 m−1 in July 2006 and 38 to 43 L min−1 m−1 in March 2007. SGD from 200 m of Stinson Beach in March 2007 contributed a flux of phosphate and dissolved inorganic nitrogen
approximately equal to that associated with all local creeks and streams within 6 km of the study site at that time. 相似文献
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This paper joins literature on suburban advertising with Lefebvre's concept of representational space to analyse property advertisements as part of the representational production of suburban space. Based on comparative analysis of advertising material for suburban residential developments on Auckland's “North Shore” in two time‐periods—1950s and 2010s—the paper examines changes and continuities in thematic content. While property advertisements in the mid‐1900s emphasised the “functional suburb,” paying attention to attributes such as quality of utilities and proximity to the central city, more recently advertisements have more strongly emphasised the “lifestyle suburb,” with a focus on middle‐class community and natural amenity. 相似文献
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Alexandria B. Boehm Kevan M. Yamahara Sarah P. Walters Blythe A. Layton Daniel P. Keymer Rachelle S. Thompson Karen L. Knee Matt Rosener 《Estuaries and Coasts》2011,34(5):925-936
This study quantifies dissolved inorganic nitrogen (DIN), soluble reactive phosphorous (SRP), and microbial pollutant inputs
to a tropical embayment, Hanalei Bay, Kaua'i, Hawai'i from rural watersheds during two field excursions during non-storm conditions.
We employ land cover analysis and a suite of nucleic acid fecal source tracking markers (host-specific Bacteroidales and human enterovirus) to identify sources of pollutants to the bay. The highest concentrations of DIN and SRP are in streams
draining watersheds with large areas of cultivated land, suggesting fertilizer is a source of these nutrients to the streams
and coastal waters. Pollutant areal loading correlates with the fractions of urban and cultivated land cover. Microbial source
tracking indicates the presence of human, pig, and ruminant feces in the streams. This work provides preliminary evidence
that human development affects loading of DIN, SRP, and microbial pollutants to tropical coastal waters; further study is
needed to confirm this. Additionally, results point to a mix of microbial pollutant sources. 相似文献
5.
Nicholas B. Handler Adina Paytan Christopher P. Higgins Richard G. Luthy Alexandria B. Boehm 《Estuaries and Coasts》2006,29(5):860-870
To elucidate relationships between land cover and water quality along the central California coast, we collected monthly samples
from 14 coastal waterway outlets representing various degrees of human development. Sites were distributed between three salinity
categories, freshwater, estuarine, and marine, to better understand land cover-water quality relationships across a range
of coastal aquatic ecosystems. Samples were analyzed for fecal indicator bacteria (FIB), dissolved nutrients, stable nitrogen
isotopes in particulate organic matter, and chlorophylla (chla). Sediment samples from 11 sites were analyzed for the concentration of the anthropogenic organic contaminant perfluorooctane
sulfonate and its precursors (ΣPFOS). While the data indicated impairment by nutrient, microbial, and organic contaminants
at both agricultural and urban sites, the percentage of agricultural land cover was the most robust indicator of impairment,
showing significant correlations (p<0.05) to FIB, nutrient, chla, and ΣPFOS levels. FIB densities were strongly influenced by salinity and were highest at sites dominated by agriculture
and urbanization. Nutrient levels and chla correlated to both agricultural and urban land use metrics as well. Positive correlations among FIB, nutrients, chla, and ΣPFOS suggest a synergy between microbial, nutrient, and organic pollution. The results emphasize the importance of
land management in protecting coastal water bodies and human health, and identify nutrient, microbial, and organic pollution
as prevalent problems in coastal California water bodies. 相似文献
6.
Improving solar radiation models is critical for supporting the increase in solar energy usage and modeling ecosystem dynamics. However, coarse spatial resolutions of solar radiation models overlook the impacts resulting from spatial variability of clouds at meso- and micro-scales. To address this problem, Moderate Resolution Imaging Spectroradiometer (MODIS) cloud climatology developed by the National Severe Storms Laboratory was used to relate cloudiness to surface solar radiation observations. We developed a linear regression model between the surface solar radiation and MODIS cloud climatology and used the model to estimate average radiation across Oklahoma. Furthermore, the study compared the average error and coefficient of determination to measured ground radiation. Error analysis of the regression model showed that the differences between observed radiation and estimated radiation were spatially autocorrelated for the Aqua MODIS satellite scan. This suggests cloudiness alone is not sufficient to predict surface solar radiation. This study found that simple cloud datasets alone can account for approximately 50% of the variation in observed solar radiation at 250-m spatial resolution, but additional datasets such as optical depth, elevation, and slope are needed to accurately explain spatial distributions of incoming shortwave radiation. 相似文献
7.
Karen L. Knee Blythe A. Layton Joseph H. Street Alexandria B. Boehm Adina Paytan 《Estuaries and Coasts》2008,31(4):607-622
Water quality monitoring in Hanalei Bay, Kaua`i (Hawai`i, USA) has documented intermittent high concentrations of nutrients
(nitrate, phosphate, silica, and ammonium) and fecal indicator bacteria (FIB, i.e., enterococci and Escherichia coli) in nearshore waters and spurred concern that contaminated groundwater might be discharging into the bay. The present study
sought to identify and track sources of nutrients and FIB to four beaches in Hanalei Bay and one beach outside the bay, together
representing a wide range of land uses. 223Ra and 224Ra activity, salinity, nutrient and FIB concentrations were measured in samples from the coastal aquifer, the nearshore ocean,
springs, the Hanalei River, and smaller streams. In addition, FIB concentrations in beach sands were measured at each site,
and the enterococcal surface protein (esp) gene assay was used to investigate whether the observed FIB originated from a human source. Nutrient concentrations in groundwater
were significantly higher than in nearshore water, inversely correlated to salinity, and highly site specific, indicating
local controls on groundwater quality. Fluxes of groundwater into Hanalei Bay were calculated using a mass-balance approach
and represented at least 2–10% of river discharges. However, submarine groundwater discharge (SGD) may provide 2.7 times as
much nitrate + nitrite to Hanalei Bay as does the Hanalei River. It may also provide significant fluxes of phosphate and ammonium,
comprising 15% and 20% of Hanalei River inputs, respectively. SGD-derived silica inputs to the bay comprised less than 3%
of Hanalei River inputs. FIB concentrations in groundwater were typically lower than those in nearshore water, suggesting
that significant FIB inputs from SGD are unlikely. Positive esp gene assays suggested that some enterococci in environmental samples were of human fecal origin. Identifying how nutrients
and FIB enter nearshore waters will help environmental managers address pressing water quality issues, including exceedances
of the state Enterococcus water quality standard and nutrient loading to coral reefs. 相似文献
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