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41.
A simple quantitative approach for assessing the artificial recharge potential of large regions using spatial ensembles of local models is proposed. The method extends existing qualitative approaches and enables rapid assessments within a programmable environment. Spatial discretization of a water resource region into continuous local domains allows simple local models to be applied independently in each domain using lumped parameters. The ensemble results can be analyzed directly or combined with other quantitative and thematic information and visualized as regional suitability maps. A case study considers the hydraulic potential for surface infiltration across a large water resource region using a published analytic model for basin recharge. The model solution was implemented within a geographic information system and evaluated independently in >21,000 local domains using lumped parameters derived from existing regional datasets. Computer execution times to run the whole ensemble and process the results were in the order of a few minutes. Relevant aspects of the case study results and general conclusions concerning the utility and limitations of the method are discussed. 相似文献
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Bacterial transport experiments in fractured crystalline bedrock 总被引：5，自引：0，他引：5
The efficiency of contaminant biodegradation in ground water depends, in part, on the transport properties of the degrading bacteria. Few data exist concerning the transport of bacteria in saturated bedrock, particularly at the field scale. Bacteria and microsphere tracer experiments were conducted in a fractured crystalline bedrock under forced-gradient conditions over a distance of 36 m. Bacteria isolated from the local ground water were chosen on the basis of physicochemical and physiological differences (shape, cell-wall type, motility), and were differentially stained so that their transport behavior could be compared. No two bacterial strains transported in an identical manner, and microspheres produced distinctly different breakthrough curves than bacteria. Although there was insufficient control in this field experiment to completely separate the effects of bacteria shape, reaction to Gram staining, cell size, and motility on transport efficiency, it was observed that (1) the nonmotile, mutant strain exhibited better fractional recovery than the motile parent strain; (2) Gram-negative rod-shaped bacteria exhibited higher fractional recovery relative to the Gram-positive rod-shaped strain of similar size; and (3) coccoidal (spherical-shaped) bacteria transported better than all but one strain of the rod-shaped bacteria. The field experiment must be interpreted in the context of the specific bacterial strains and ground water environment in which they were conducted, but experimental results suggest that minor differences in the physical properties of bacteria can lead to major differences in transport behavior at the field scale. 相似文献
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Torres MA Testa CP Gáspari C Masutti MB Panitz CM Curi-Pedrosa R de Almeida EA Di Mascio P Filho DW 《Marine pollution bulletin》2002,44(9):923-932
Digestive glands of the mangrove mussel Mytella guyanensis, collected at one non-polluted site (site 1) and two polluted sites (sites 2 and 3), were analysed for different antioxidant defenses, lipid peroxidation and DNA damage. Thiobarbituric acid-reactive substance (TBARS) and 8-oxo-7,8-dihydro-2'-deoxyguanosine levels were enhanced at the polluted sites. With the exception of superoxide dismutase, the activities of catalase and glutathione peroxidase were also higher at the polluted sites. Greater increases were observed in glutathione reductase, glutathione S-transferase and etoxyresorufine-O-deethylase activities at the polluted sites. Conversely, reduced glutathione content was higher at the control site. Trace metal contents in mussels collected at polluted sites were increased compared to the control site, and there were strong positive correlations between TBARS and Cu and Pb contents. M. guyanensis is routinely exposed to an oxidative stress condition at both polluted sites, and considering xenobiotic bioaccumulation in bivalve molluscs, the mangrove mussel represents an excellent bioindicator for environmental monitoring studies. 相似文献
44.
Organochlorines and organophosphates were measured in four fish species (Lateolabrax japonicus, Pagrasomus major, Miichthys miiuy and Epinephalus awoara) and the mussel Perna viridis collected from aquaculture cages in coastal waters of Xiamen, China. Polycyclic aromatic hydrocarbon (PAH) metabolites were also measured in fish bile. Sites in Xiamen coastal waters (the harbour, Maluan and Tongan) are compared with a "cleaner" reference site at Dongshan Island. DDT was found in livers of all fish sampled (May 1998, 1999 and December 1999) ranging from 0.15 to 2.2 microg/g WW, but levels in muscle tissue (<0.5 ng/g to 0.22 microg/g WW) were at least an order of magnitude lower in the harbour, and were not detectable (<0.5 ng/g) in Tongan samples. All other pesticides examined were not detected in fish or mussels, except for dieldrin in one liver sample (0.07 microg/g WW). Food of the caged fish, small fish and dried pellets, had very low (0.015-0.027 microg/g WW) or non-detectable levels of DDT, indicating significant bioaccumulation of contaminants in caged fish and/or other possible sources of uptake (water and sediments). DDT levels in fish varied with species. DDT contamination in fish livers and whole mussels varied significantly with location. Highest concentrations in fish occurred in the harbour, and less consistently so in Tongan. Dongshan and Maluan had comparatively low levels of DDT. Relatively low residues of DDT in both fish and mussels at Dongshan likely reflect lower levels of pesticide input at this reference site. However, the low levels of DDT contamination in fish tissues from Maluan were unexpected in view of the close proximity of the harbour and possibly reflect the removal of particulate-bound contaminants by the intensive bivalve culture there. Consistently high proportions of DDT in the form of the parent compound (p,p'-DDT: fish 30-45%; mussels 40-65%) from all sites suggest recent releases of this chemical to the environment. Levels of two main groups of PAH metabolites (naphthalene and phenanthrene) in fish bile suggest a different environmental distribution pattern than that of pesticides, in that Dongshan fish appear to be no less exposed to hydrocarbons than those from Xiamen coastal waters. 相似文献
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Upper Cretaceous strata of the Mahajanga Basin, northwestern Madagascar, yield some of the most significant and exquisitely preserved vertebrate fossils known from Gondwana. The sedimentology of these strata and their stratigraphic relations have been the focus of renewed geological investigations during the course of five expeditions since 1993. We here designate stratotypes and formalize the terrestrial Maevarano Formation, with three new members (Masorobe, Anembalemba, Miadana), and the overlying marine Berivotra Formation. The Maevarano Formation accumulated on a broad, semiarid alluvial plain bounded to the southeast by crystalline highlands and to the northwest by the Mozambique Channel. The Berivotra Formation was deposited in an open marine setting that evolved from a clastic- to a carbonate-dominated shelf, resulting in deposition of the overlying Betsiboka limestone of Danian age. New stratigraphic data clearly indicate that the Maevarano Formation correlates, at least in part, with the Maastrichtian Berivotra Formation, and this in turn indicates that the most fossiliferous portions of the Maevarano Formation are Maastrichtian in age, rather than Campanian as previously reported. This revised age for the Maevarano vertebrate assemblage indicates that it is approximately contemporaneous with the vertebrate fauna recovered from the Deccan basalt volcano-sedimentary sequence of India. The comparable age of these two faunas is significant because the faunas appear to be more similar to one another than either is to those from any other major Gondwanan landmass. The revised age of the Maevarano Formation, when considered in the light of our recent fossil discoveries, further indicates that the ancestral stocks of Madagascar's overwhelmingly endemic modern vertebrate fauna arrived on the island in post-Mesozoic times. The basal stocks of the modern vertebrate fauna are conspicuously absent in the Maevarano Formation. Finally, the revised age of the Maevarano Formation serves to expand our global perspective on the K/T event by clarifying the age of a diverse, and arguably the best preserved, sample of Gondwanan vertebrates from the terminal Cretaceous. 相似文献
49.
A suite of biomarkers were measured in barramundi (Lates calcarifer) from five North Queensland estuaries along a perceived pollution gradient. The biomarkers selected were 7-ethoxyresorufin-O-deethylase (EROD), cytochrome P450, fluorescent aromatic compounds (FACs), DNA integrity, RNA:DNA ratio, cholinesterase activity (ChE), condition factor and hepatosomatic index. The resulting database was subjected to uni- and multi-variate analyses in order to assess the most suitable biomarkers to assess pollution in North Queensland estuaries and to classify the environmental quality of the sites. Principal components analysis (PCA) on the biochemical markers revealed that EROD, EROD/P450, DNA damage and to a lesser extent ChE and FACs were found to be responsive to contaminants in the environment while cytochrome P450, condition factor and the hepatosomatic index were found to be less responsive biomarkers. This study has demonstrated the utility of applying a multibiomarker approach in conjunction with traditional analysis of contaminants in providing valuable information in environmental risk assessment. 相似文献
50.
Field methods for amending marine sediment with activated carbon and assessing treatment effectiveness 总被引：1，自引：0，他引：1
Cho YM Smithenry DW Ghosh U Kennedy AJ Millward RN Bridges TS Luthy RG 《Marine environmental research》2007,64(5):541-555
Previous laboratory studies have shown reductions in PCB bioavailability for sediments amended with activated carbon (AC). Here we report results on a preliminary pilot-scale study to assess challenges in scaling-up for field deployment and monitoring. The goals of the preliminary pilot-scale study at Hunters Point Shipyard (San Francisco, USA) were to (1) test the capabilities of a large-scale mixing device for incorporating AC into sediment, (2) develop and evaluate our field assessment techniques, and (3) compare reductions in PCB bioavailability found in the laboratory with well-mixed systems to those observed in the field with one-time-mixed systems. In this study we successfully used a large-scale device to mix 500kg of AC into a 34.4m(2) plot to a depth of 1ft, a depth that includes the majority of the biologically active zone. Our results indicate that after 7 months of AC-sediment contact in the field, the 28-day PCB bioaccumulation for the bent-nosed clam, Macoma nasuta, field-deployed to this AC-amended sediment was approximately half of the bioaccumulation resulting from exposure to untreated sediment. Similar PCB bioaccumulation reductions were found in laboratory bioassays conducted on both the bivalve, M. nasuta and the estuarine amphipod, Leptocheirus plumulosus, using sediment collected from the treated and untreated field plots one year after the AC amendment occurred. To further understand the long-term effectiveness of AC as an in situ treatment strategy for PCB-contaminated sediments under field conditions, a 3-year comprehensive study is currently underway at Hunters Point that will compare the effectiveness of two large-scale mixing devices and include both unmixed and mixed-only control plots. 相似文献