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91.
92.
Excavations at Bonneville Estates Rockshelter, Nevada recovered rodent remains from stratified deposits spanning the past ca. 12,500 14C yr BP (14,800 cal yr BP). Specimens from horizons dating to the late Pleistocene and early Holocene include species adapted to montane and moist and cool habitats, including yellow-bellied marmot (Marmota flaviventris) and bushy-tailed woodrat (Neotoma cinerea). Shortly after 9000 14C BP (10,200 cal yr BP) these mammals became locally extinct, or nearly so, taxonomic diversity declined, and the region became dominated by desert woodrats (Neotoma lepida) and other species well-adapted to xeric, low-elevation settings. The timing and nature of changes in the Bonneville Estates rodent fauna are similar to records reported from nearby Homestead and Camels Back caves and provide corroborative data on terminal Pleistocene–early Holocene environments and mammalian responses to middle Holocene desertification. Moreover, the presence of northern pocket gopher (Thomomys talpoides) at Bonneville Estates adds to a sparse regional record for that species and, similar to Homestead Cave, it appears that the ca. 9500 14C yr BP (10,800 cal yr BP) replacement of the northern pocket gopher by Botta's pocket gopher in the Great Salt Lake Desert vicinity was also in response to climate change. 相似文献
93.
Ghislain Dubois Benjamin Sovacool Carlo Aall Maria Nilsson Carine Barbier Alina Herrmann Sébastien Bruyère Camilla Andersson Bore Skold Franck Nadaud Florian Dorner Karen Richardsen Moberg Jean Paul Ceron Helen Fischer Dorothee Amelung Marta Baltruszewicz Jeremy Fischer Françoise Benevise Valérie R. Louis Rainer Sauerborn 《Chemie der Erde / Geochemistry》2012
Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy. 相似文献
94.
Kimberly A. Null Natasha T. Dimova Karen L. Knee Bradley K. Esser Peter W. Swarzenski Michael J. Singleton Mark Stacey Adina Paytan 《Estuaries and Coasts》2012,35(5):1299-1315
Submarine groundwater discharge (SGD) was quantified at select sites in San Francisco Bay (SFB) from radium (223Ra and 224Ra) and radon (222Rn) activities measured in groundwater and surface water using simple mass balance box models. Based on these models, discharge rates in South and Central Bays were 0.3?C7.4?m3?day?1?m?1. Although SGD fluxes at the two regions (Central and South Bays) of SFB were of the same order of magnitude, the dissolved inorganic nitrogen (DIN) species associated with SGD were different. In the South Bay, ammonium (NH 4 + ) concentrations in groundwater were three-fold higher than in open bay waters, and NH 4 + was the primary DIN form discharged by SGD. At the Central Bay site, the primary DIN form in groundwater and associated discharge was nitrate (NO 3 ? ). The stable isotope signatures (??15NNO3 and ??18ONO3) of NO 3 ? in the South Bay groundwater and surface waters were both consistent with NO 3 ? derived from NH 4 + that was isotopically enriched in 15N by NH 4 + volatilization. Based on the calculated SGD fluxes and groundwater nutrient concentrations, nutrient fluxes associated with SGD can account for up to 16?% of DIN and 22?% of DIP in South and Central Bays. The form of DIN contributed to surface waters from SGD may impact the ratio of NO 3 ? to NH 4 + available to phytoplankton with implications to bay productivity, phytoplankton species distribution, and nutrient uptake rates. This assessment of nutrient delivery via groundwater discharge in SFB may provide vital information for future bay ecological wellbeing and sensitivity to future environmental stressors. 相似文献
95.
For a century or so, the Hong Kong Observatory (HKO) has been providing temperature forecast for the whole of Hong Kong with
the HKO Headquarters as the reference location. In recent decades, due to spreading of population from the main urban center
to satellite towns, there is an increasing demand for regional temperature forecasts. To support such provision, the HKO has
developed a regression model to provide objective guidance to forecasters in formulating forecasts of maximum and minimum
temperatures for the next day at various locations in Hong Kong. In this paper, the regression model is presented, together
with the assessment of its performance. Based on the verification of one year of forecasts, it is found that the root mean
square errors (RMSEs) of maximum (minimum) temperature forecasts are from about 1.3 to 2.1 (1.1 to 1.4) degrees, respectively.
The regression model is shown to have generally out-performed the operational regional spectral model then operated by HKO.
Regional temperature forecast methods of other meteorological or research centers are also surveyed. Equipped with the regression
model, the HKO has launched an online regional temperature forecast service for the next day in Hong Kong since March 2008. 相似文献
96.
Occurrence and distribution of microplastics in marine sediments along the Belgian coast 总被引:2,自引:0,他引:2
Claessens M De Meester S Van Landuyt L De Clerck K Janssen CR 《Marine pollution bulletin》2011,62(10):2199-2204
Plastic debris is known to undergo fragmentation at sea, which leads to the formation of microscopic particles of plastic; the so called ‘microplastics’. Due to their buoyant and persistent properties, these microplastics have the potential to become widely dispersed in the marine environment through hydrodynamic processes and ocean currents. In this study, the occurrence and distribution of microplastics was investigated in Belgian marine sediments from different locations (coastal harbours, beaches and sublittoral areas).Particles were found in large numbers in all samples, showing the wide distribution of microplastics in Belgian coastal waters. The highest concentrations were found in the harbours where total microplastic concentrations of up to 390 particles kg−1 dry sediment were observed, which is 15-50 times higher than reported maximum concentrations of other, similar study areas.The depth profile of sediment cores suggested that microplastic concentrations on the beaches reflect the global plastic production increase. 相似文献
97.
William W. ChadwickJr Sigurjon Jónsson Dennis J. Geist Michael Poland Daniel J. Johnson Spencer Batt Karen S. Harpp Andres Ruiz 《Bulletin of Volcanology》2011,73(6):679-697
The May 2005 eruption of Fernandina volcano, Galápagos, occurred along circumferential fissures parallel to the caldera rim
and fed lava flows down the steep southwestern slope of the volcano for several weeks. This was the first circumferential
dike intrusion ever observed by both InSAR and GPS measurements and thus provides an opportunity to determine the subsurface
geometry of these enigmatic structures that are common on Galápagos volcanoes but are rare elsewhere. Pre- and post- eruption
ground deformation between 2002 and 2006 can be modeled by the inflation of two separate magma reservoirs beneath the caldera:
a shallow sill at ~1 km depth and a deeper point-source at ~5 km depth, and we infer that this system also existed at the
time of the 2005 eruption. The co-eruption deformation is dominated by uplift near the 2005 eruptive fissures, superimposed
on a broad subsidence centered on the caldera. Modeling of the co-eruption deformation was performed by including various
combinations of planar dislocations to simulate the 2005 circumferential dike intrusion. We found that a single planar dike
could not match both the InSAR and GPS data. Our best-fit model includes three planar dikes connected along hinge lines to
simulate a curved concave shell that is steeply dipping (~45–60°) toward the caldera at the surface and more gently dipping
(~12–14°) at depth where it connects to the horizontal sub-caldera sill. The shallow sill is underlain by the deep point source.
The geometry of this modeled magmatic system is consistent with the petrology of Fernandina lavas, which suggest that circumferential
eruptions tap the shallowest parts of the system, whereas radial eruptions are fed from deeper levels. The recent history
of eruptions at Fernandina is also consistent with the idea that circumferential and radial intrusions are sometimes in a
stress-feedback relationship and alternate in time with one another. 相似文献
98.
Background
Induced precipitation of phosphate minerals to scavenge trace elements from groundwater is a potential remediation approach for contaminated aquifers. The success of engineered precipitation schemes depends on the particular phases generated, their rates of formation, and their long term stability. The purpose of this study was to examine the precipitation of calcium phosphate minerals under conditions representative of a natural groundwater. Because microorganisms are present in groundwater, and because some proposed schemes for phosphate mineral precipitation rely on stimulation of native microbial populations, we also tested the effect of bacterial cells (initial densities of 105 and 107 mL-1) added to the precipitation medium. In addition, we tested the effect of a trace mixture of propionic, isovaleric, formic and butyric acids (total concentration 0.035 mM).Results
The general progression of mineral precipitation was similar under all of the study conditions, with initial formation of amorphous calcium phosphate, and transformation to poorly crystalline hydroxylapatite (HAP) within one week. The presence of the bacterial cells appeared to delay precipitation, although by the end of the experiments the overall extent of precipitation was similar for all treatments. The stoichiometry of the final precipitates as well as Rietveld structure refinement using x-ray diffraction data indicated that the presence of organic acids and bacterial cells resulted in an increasing a and decreasing c lattice parameter, with the higher concentration of cells resulting in the greatest distortion. Uptake of Sr into the solids was decreased in the treatments with cells and organic acids, compared to the control.Conclusions
Our results suggest that the minerals formed initially during an engineered precipitation application for trace element sequestration may not be the ones that control long-term immobilization of the contaminants. In addition, the presence of bacterial cells appears to be associated with delayed HAP precipitation, changes in the lattice parameters, and reduced incorporation of trace elements as compared to cell-free systems. Schemes to remediate groundwater contaminated with trace metals that are based on enhanced phosphate mineral precipitation may need to account for these phenomena, particularly if the remediation approach relies on enhancement of in situ microbial populations. 相似文献99.
Grazing by small epifauna on live seagrass leaves was formerly viewed as unimportant in controlling plant biomass and growth,
instead researchers focused on the indirect benefits of small invertebrates that crop algal competitors. Recent evidence shows
that the emerald nerite Smaragdia viridis preferentially ingests seagrass leaf tissue. In contrast, the button snail Modulus modulus feeds on epiphytes and periphyton coating the leaves. We conducted laboratory microcosm and field experiments to investigate
how the different feeding preferences of these seagrass-associated snails affect turtlegrass Thalassia testudinum primary production. Data revealed that after 24 h S. viridis reduced foliar biomass (25%) and chlorophyll (30%) and injured the equivalent of 50% of daily seagrass growth per shoot.
Conversely, M. modulus did not affect these variables. Our results emphasize that in subtropical seagrass communities not all small epifauna browse
off leaf surfaces and some can have important direct negative impacts on their seagrass host. 相似文献
100.