Artificial recharge through a thick, heterogeneous unsaturated zone   总被引：2，自引：0，他引：2  

Izbicki JA  Flint AL  Stamos CL 《Ground water》2008,46(3):475-488

Thick, heterogeneous unsaturated zones away from large streams in desert areas have not previously been considered suitable for artificial recharge from ponds. To test the potential for recharge in these settings, 1.3 x 10(6) m(3) of water was infiltrated through a 0.36-ha pond along Oro Grande Wash near Victorville, California, between October 2002 and January 2006. The pond overlies a regional pumping depression 117 m below land surface and is located where thickness and permeability of unsaturated deposits allowed infiltration and saturated alluvial deposits were sufficiently permeable to allow recovery of water. Because large changes in water levels caused by nearby pumping would obscure arrival of water at the water table, downward movement of water was measured using sensors in the unsaturated zone. The downward rate of water movement was initially as high as 6 m/d and decreased with depth to 0.07 m/d; the initial time to reach the water table was 3 years. After the unsaturated zone was wetted, water reached the water table in 1 year. Soluble salts and nitrate moved readily with the infiltrated water, whereas arsenic and chromium were less mobile. Numerical simulations done using the computer program TOUGH2 duplicated the downward rate of water movement, accumulation of water on perched zones, and its arrival at the water table. Assuming 10 x 10(6) m(3) of recharge annually for 20 years, a regional ground water flow model predicted water level rises of 30 m beneath the ponds, and rises exceeding 3 m in most wells serving the nearby urban area.  相似文献   

Measuring channel planform change from image time series: A generalizable,spatially distributed,probabilistic method for quantifying uncertainty     

Christina M. Leonard  Carl J. Legleiter  Devin M. Lea  John C. Schmidt 《地球表面变化过程与地形》2020,45(11):2727-2744

Channels change in response to natural or anthropogenic fluctuations in streamflow and/or sediment supply and measurements of channel change are critical to many river management applications. Whereas repeated field surveys are costly and time-consuming, remote sensing can be used to detect channel change at multiple temporal and spatial scales. Repeat images have been widely used to measure long-term channel change, but these measurements are only significant if the magnitude of change exceeds the uncertainty. Existing methods for characterizing uncertainty have two important limitations. First, while the use of a spatially variable image co-registration error avoids the assumption that errors are spatially uniform, this type of error, as originally formulated, can only be applied to linear channel adjustments, which provide less information on channel change than polygons of erosion and deposition. Second, previous methods use a level-of-detection (LoD) threshold to remove non-significant measurements, which is problematic because real changes that occurred but were smaller than the LoD threshold would be removed. In this study, we present a new method of quantifying uncertainty associated with channel change based on probabilistic, spatially varying estimates of co-registration error and digitization uncertainty that obviates a LoD threshold. The spatially distributed probabilistic (SDP) method can be applied to both linear channel adjustments and polygons of erosion and deposition, making this the first uncertainty method generalizable to all metrics of channel change. Using a case study from the Yampa River, Colorado, we show that the SDP method reduced the magnitude of uncertainty and enabled us to detect smaller channel changes as significant. Additionally, the distributional information provided by the SDP method allowed us to report the magnitude of channel change with an appropriate level of confidence in cases where a simple LoD approach yielded an indeterminate result. © 2020 John Wiley & Sons, Ltd.  相似文献   

Cryptosporidium and Giardia in Natural,Drinking, and Recreational Water of Northwestern Greece     

Panagiotis Karanis  Chrysanthi Papadopoulou  Akio Kimura  Evagelos Economou  Christina Kourenti  Heracles Sakkas 《洁净——土壤、空气、水》2002,30(1):49-58

An investigation about distribution of Giardia cysts and Cryptosporidium oocysts in natural, drinking, and recreational water in Northwestern Greece was performed. Five rivers (Aoos, Arachthos, Kalamas, Louros, and Voidomatis) and one lake (Pamvotis Ioannina Lake) in Northwestern Greece were investigated during a 10‐month period. Drinking and recreational water (swimming pools) from the area were also examined. Samples were collected from prefixed sampling stations and processed following a modification of standard methods for the microbiological examination of water, as suggested by the APHA/AWWA/WEF. Both Giardia cysts and Cryptosporidium oocysts were isolated from Pamvotis Ioannina Lake (15 positive/27 examined samples). Significantly lower numbers of Cryptosporidium oocysts were detected in Arachthos River (1/5), Voidomatis River (1/5), drinking water (1/7), and pool water samples (1/9). No Giardia cysts were detected, neither in river water, nor in drinking, and pool water samples. The results clearly show that, with the exception of Pamvotis Ioannina Lake, where contamination of high level was observed, natural water sources of the investigated area have low pollution, resulting in low contamination with parasites.  相似文献   

Petrogenesis of main group pallasite meteorites based on relationships among texture,mineralogy, and geochemistry     

Seann J. McKibbin  Lidia Pittarello  Christina Makarona  Christopher Hamann  Lutz Hecht  Stepan M. Chernonozhkin  Steven Goderis  Philippe Claeys 《Meteoritics & planetary science》2019,54(11):2814-2844

Main group pallasite meteorites are samples of a single early magmatic planetesimal, dominated by metal and olivine but containing accessory chromite, sulfide, phosphide, phosphates, and rare phosphoran olivine. They represent mixtures of core and mantle materials, but the environment of formation is poorly understood, with a quiescent core–mantle boundary, violent core–mantle mixture, or surface mixture all recently suggested. Here, we review main group pallasite data sets and petrologic characteristics, and present new observations on the low‐MnO pallasite Brahin that contains abundant fragmental olivine, but also rounded and angular olivine and potential evidence of sulfide–phosphide liquid immiscibility. A reassessment of the literature shows that low‐MnO and high‐FeO subgroups preferentially host rounded olivine and low‐temperature P₂O₅‐rich phases such as the Mg‐phosphate farringtonite and phosphoran olivine. These phases form after metal and silicate reservoirs back‐react during decreasing temperature after initial separation, resulting in oxidation of phosphorus and chromium. Farringtonite and phosphoran olivine have not been found in the common subgroup PMG, which are mechanical mixtures of olivine, chromite with moderate Al₂O₃ contents, primitive solid metal, and evolved liquid metal. Lower concentrations of Mn in olivine of the low‐MnO PMG subgroup, and high concentrations of Mn in low‐Al₂O₃ chromites, trace the development and escape of sulfide‐rich melt in pallasites and the partially chalcophile behavior for Mn in this environment. Pallasites with rounded olivine indicate that the core–mantle boundary of their planetesimal may not be a simple interface but rather a volume in which interactions between metal, silicate, and other components occur.  相似文献   

Mapping iron abundances on the surface of Mercury: Predicted spatial resolution of the MESSENGER Gamma-Ray Spectrometer     

Patrick N. Peplowski  David T. Blewett  Brett W. Denevi  Larry G. Evans  David J. Lawrence  Larry R. Nittler  Edgar A. Rhodes  Christina M. Selby  Sean C. Solomon 《Planetary and Space Science》2011,59(13):1654-1658

To illustrate the spatial resolution of measurements of Mercury's surface elemental composition by the Gamma-Ray Spectrometer on the MESSENGER spacecraft after one year of orbital observations, we have simulated a global coverage map of the 846-keV iron gamma-ray count rate. The simulated map suggests that distinct geologic units larger than 800 km in horizontal dimension will be discernable when the difference in Fe abundance between adjacent geologic units exceeds 4 wt%. These results imply that the MESSENGER Gamma-Ray Spectrometer dataset will provide useful information for regional geological studies of the surface of Mercury.  相似文献   

Natural revegetation and afforestation in abandoned cropland areas: Hydrological trends and changes in Mediterranean mountains     

Makki Khorchani  Estela Nadal-Romero  Teodoro Lasanta  Christina Tague 《水文研究》2021,35(5):e14191

Water resources availability is one of the main concerns for policy makers around the world in present and future management plans. In the Mediterranean basin, this concern is increased given the extreme variability in climate and the intrinsic aridity conditions. Water resources in the Mediterranean region depend mainly on surface and subsurface supply from mountain areas. Because evapotranspiration comprises a substantial portion of the water budget, recent land cover changes due to cropland abandonment may change transpiration (TRANS) and water supply. Therefore, land management plans must account for these potential hydrologic changes to guarantee water availability in the upcoming decades. Short-term changes to water yield have been shown to follow afforestation or natural revegetation, the main management strategies in abandoned cropland areas. Studies comparing long-term trends of these management practices, however, are scarce due to the lack of long-term hydrological data. In this study, we use the regional hydro-ecological simulation system (RHESSys), to analyse long-term changes and annual and seasonal trends in streamflow (STR) and transpiration following management of abandoned cropland areas. Annual mean values show significant differences between the three management scenarios for both streamflow and transpiration, while differences between climate scenarios are not significant. The Mann Kendall trend analysis shows significant changes to water yield compared to the situation before management. Depending on the total afforested area, afforestation could significantly decrease annual streamflow between 2.3%·decade⁻¹ and 5.9%·decade⁻¹ and increase annual transpiration between 1.1%·decade⁻¹ and 3.5%·decade⁻¹. These trends are attributed to changes during the first 30 years after management, while during the fourth and fifth decade, changes to water yield tend to stabilize or decrease. These results are substantial to optimize land management plans, ensuring sustainable hydrological and ecological ecosystem services.  相似文献   

Proposed methods for potential evapotranspiration calculation of the Red River basin (North Vietnam)     

Thi Phuong Quynh Le  Christina Seidler  Matthias Kändler  Thi Bich Nga Tran 《水文研究》2012,26(18):2782-2790

Potential evapotranspiration (ETP) is an important part of a climatic water balance and a crucial variable in many kinds of models in computing actual evapotranspiration. The objective of this study was to find a reasonable approach of ETP calculation for a height‐differentiated landscape in subtropical climate. From the pool of diverse approaches, six common methods [Hamon, Priestley–Taylor, Thornthwaite, Blaney–Criddle, Turc and Food and Agricultural Organization Irrigation and Drainage Paper No. 56 (FAO‐56)] were selected. With the meteorological data for long‐term period (1964–2008), the calculation of ETP values was performed for 12 different meteorological stations in the Red River basin. Among the applied ETP calculation methods, the Turc and the FAO‐56 methods agreed well at most stations and represent best the expectations for the ETP values of the Thao and Da subbasins. The findings of our investigations indicate that in highly structured (land use and elevation) regions, not all methods provide satisfying results. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Effects of chronic exposure to dispersed oil on selected reproductive processes in adult blue mussels (Mytilus edulis) and the consequences for the early life stages of their larvae     

Baussant T  Ortiz-Zarragoitia M  Cajaraville MP  Bechmann RK  Taban IC  Sanni S 《Marine pollution bulletin》2011,62(7):1437-1445

Mussels (Mytilus edulis) were continuously exposed to dispersed crude oil (0.015-0.25 mg/l) for 7 months covering the whole gamete development cycle. After 1 month exposure to 0.25 mg oil/l, the level of alkali-labile phosphates (ALP) and the volume density of atretic oocytes in female gonads were higher than those in the gonads of control females, indicating that oil affected the level of vitellogenin-like proteins and gamete development. Spawning of mussels was induced after 7 months oil exposure. Parental oil exposure did not affect subsequent fertilization success in clean seawater but this was reduced in 0.25 mg oil/l. Parental exposure to 0.25 mg oil/l caused both slow development and a higher percentage of abnormalities in D-shell larvae 2 days post-fertilization; reduced growth 7 days post-fertilization. These effects were greatly enhanced when larval stages were maintained at 0.25 mg oil/l. Similar studies are warranted for risk assessment prognosis.  相似文献   

Satellite and ground observations of the June 2009 eruption of Sarychev Peak volcano, Matua Island, Central Kuriles     

Alexander Rybin  Marina Chibisova  Peter Webley  Torge Steensen  Pavel Izbekov  Christina Neal  Vince Realmuto 《Bulletin of Volcanology》2011,73(9):1377-1392

After 33 years of repose, one of the most active volcanoes of the Kurile island arc—Sarychev Peak on Matua Island in the Central Kuriles—erupted violently on June 11, 2009. The eruption lasted 9 days and stands among the largest of recent historical eruptions in the Kurile Island chain. Satellite monitoring of the eruption, using Moderate Resolution Imaging Spectroradiometer, Meteorological Agency Multifunctional Transport Satellite, and Advanced Very High Resolution Radiometer data, indicated at least 23 separate explosions between 11 and 16 June 2009. Eruptive clouds reached altitudes of generally 8–16 km above sea level (ASL) and in some cases up to 21 km asl. Clouds of volcanic ash and gas stretched to the north and northwest up to 1,500 km and to the southeast for more than 3,000 km. For the first time in recorded history, ash fall occurred on Sakhalin Island and in the northeast sector of the Khabarovsky Region, Russia. Based on satellite image analysis and reconnaissance field studies in the summer of 2009, the eruption produced explosive tephra deposits with an estimated bulk volume of 0.4 km³. The eruption is considered to have a Volcanic Explosivity Index of 4. Because the volcano is remote, there was minimal risk to people or infrastructure on the ground. Aviation transport, however, was significantly disrupted because of the proximity of air routes to the volcano.  相似文献   

Chalcophile element geochemistry and petrogenesis of high-Ti and low-Ti magmas in the Permian Emeishan large igneous province,SW China   总被引：4，自引：0，他引：4  

Christina Yan Wang  Mei-Fu Zhou  Liang Qi 《Contributions to Mineralogy and Petrology》2011,161(2):237-254

Sulfide-poor mafic layered intrusions, sills/dykes and lava flows in the Funing region, SW China, are part of the ~260 Ma Emeishan large igneous province. They belong to either a high-Ti group (TiO₂ = 1.6–4.4 wt%) with elevated Ti/Y ratios (351–1,018), or a low-Ti group (TiO₂ < 1.2 wt%) with low Ti/Y ratios (133–223). This study investigates the role of fractionation of olivine, chromite and sulfide on the distributions of chalcophile elements, Ni, Cu and PGE, of the high-Ti and low-Ti group rocks at Funing. The high-Ti group rocks contain 1.6–5.3 ppb Pt + Pd, 0.06–0.43 ppb Ir and 0.01–0.13 ppb Ru, and show relative constant (Cu/Pd)_PM ratios (4.0–9.7) and a negative correlation between Ni/Pd and Cu/Ir ratios. Fractionated IPGE/PPGE patterns and very negative Ru anomalies of the high-Ti group rocks, together with low Fo values (59–62 mol%) of olivine, indicate that the high-Ti magmas may have experienced fractionation of olivine and chromite under S-undersaturated condition. Based on the PGE concentrations, the low-Ti group rocks can be further divided into two subgroups; a high-PGE low-Ti subgroup and a low-PGE low-Ti subgroup. The high-PGE low-Ti group rocks are rich in MgO (10–20 wt%), but Fo values of olivine from the rocks are low (74–76 mol%). The rocks contain highly variable PGE (Pt + Pd = 1.7–88 ppb, Ir = 0.05–1.3 ppb), Ni (179 –1,380 ppm) and Cu (59–568 ppm). They have Cu/Zr ratios >1, low (Y/Pd)_PM ratios (0.2–7.1) and nearly constant (Cu/Pd)_PM ratios (1.5–3.8). The even and parallel chalcophile element patterns of the high-PGE low-Ti subgroup rocks are likely a result of olivine-dominated fractionation under S-undersaturated condition. The low-PGE low-Ti group rocks have low MgO (4.5–8.9 wt%) and very poor PGE (Pt + Pd 0.5–1.6 ppb, Ir 0.004–0.02 ppb) with low Cu/Zr ratios (0.1–0.5), high (Y/Pd)_PM (26–70) and variable (Cu/Pd)_PM ratios (2.8–14). The trough-like chalcophile element patterns of the low-PGE low-Ti subgroup rocks indicate that the magmas were sulfide saturation and sulfide melts were extracted from the magmas. The extracted sulfide melts might be potential Ni–Cu sulfide ores at depth in the Funing region.  相似文献