Aquifer prioritization for ambient ground water monitoring   总被引：1，自引：0，他引：1  

Marjorie E. Bedessem  Brenda Casey  Kevin Frederick  Nathan Nibbelink 《Ground Water Monitoring & Remediation》2005,25(1):150-158

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Charakterisierung von Al(III)-Spezies in basischen Aluminiumchlorid-Flockungsmitteln mittels Ferronreaktion bzw. 27Al-Kernresonanzspektroskopie Characterization of Al(III) Species in Basic Aluminium Chloride Flocculants by Means of Ferron Method and 27 Al Nuclear Magnetic Resonance     

R. Bertram  W. Geßner  D. Müller  M. Danner 《洁净——土壤、空气、水》1994,22(6):265-269

Flocculant processes as a treatment step in water and wastewater purification technology are of increasing importance. Partially neutralized aqueous aluminium chloride solutions — the basic aluminium chlorides — are often used as flocculants in water conditioning. The present paper describes the reactions which appear in these solutions by their dilution, the identification of occurring cationic aluminium species, and the relations between the composition of the solutions and their efficiency as flocculants. The solutions were quantitatively analyzed using ²⁷Al NMR and the ferron method; the latter method offers a simple and inexpensive alternative for identification and quantification of aluminium cations and can facilitate investigations of the Al speciation at concentrations too low for analysis by NMR. The distribution of aluminium cations in basic aluminium chloride solutions changes drastically by the dilution while applied as flocculants because the equilibrium strongly depends on the concentration. The dynamic changes following the dilution of partially neutralized solutions were investigated simply by mixing a solution with water and immediate analysis by the ferron method. It could be shown that rearrangement reactions occur in the system, partially overlapping each other, the oligomeric cations seem to be especially instable. Furthermore, a partial change from octahedral to tetrahedral coordination of the aluminium in the species can be observed. At extremely low aluminium concentration as in the case of application of the basic aluminium chloride solutions for flocculation, monomeric and especially transition polymeric and polymeric aluminium cations, respectively, appear. The ratio of these cations to each other also depends on the time up to the flocculation. Accordingly, these cations especially the different polymeric aluminium species seem to be important for the efficiency of the basic aluminium chlorides as flocculants in water conditioning.  相似文献   

Evaluation of microbiologically induced corrosion in an estuary     

Brenda Little  Pat Wagner  John Jacobus  Louis Janus 《Estuaries and Coasts》1989,12(3):138-141

A dockside experiment was designed at the mouth of the Pascagoula River in Pascagoula, Mississippi, to evaluate corrosion in welded Cu/Ni piping systems. Localized corrosion was shown to be due to the following sequence of events: (1) metal segregation during welding processes, (2) settlemnt of sulfide-producing bacteria in welds, (3) disruption of surface films by turbulence, and (4) formation of adjacent cathodic and anodic areas.  相似文献   

Inverted clast stratigraphy in an eolian archaeological environment     

Brenda J. Buck  John Kipp  H. Curtis Monger 《Geoarchaeology》2002,17(7):665-687

Understanding the geomorphic history of eolian basins is important in interpreting the archaeological record and human responses to past environments. One hundred forty soil profiles were excavated and described in southern New Mexico and West Texas. Seven major late Quaternary stratigraphic units were found: La Mesa, eolian Jornada (I, II), eolian Isaacks' Ranch, eolian Organ (I, II, and III), Historical Blowsand, and the playa deposits of Petts Tank and Lake Tank. Each unit represents a period of landscape instability, eolian erosion, and concurrent deposition, followed by landscape stability and soil formation. Eolian erosion can form local surficial lag deposits if materials larger than the competence of the wind are present. However, erosional processes alone cannot explain the presence of older clasts at the surface with intact, younger deposits underneath. We propose a combination of processes: deflation in eolian windows, followed by lateral movement of clasts over areas that have not been deflated. The effects of these processes on artifact stratigraphy and archaeological interpretations could be significant. © 2002 Wiley Periodicals, Inc.  相似文献   

A comparison of intertidal species richness and composition between Central California and Oahu,Hawaii     

Chela J. Zabin  Eric M. Danner  Erin P. Baumgartner  David Spafford  Kathy Ann Miller  John S. Pearse 《Marine Ecology》2013,34(2):131-156

The intertidal zone of tropical islands is particularly poorly known. In contrast, temperate locations such as California's Monterey Bay are fairly well studied. However, even in these locations, studies have tended to focus on a few species or locations. Here we present the results of the first broadscale surveys of invertebrate, fish and algal species richness from a tropical island, Oahu, Hawaii, and a temperate mainland coast, Central California. Data were gathered through surveys of 10 sites in the early 1970s and again in the mid‐1990s in San Mateo and Santa Cruz counties, California, and of nine sites in 2001–2005 on Oahu. Surveys were conducted in a similar manner allowing for a comparison between Oahu and Central California and, for California, a comparison between time periods 24 years apart. We report a previously undocumented richness of intertidal species in both locations: 516 for Oahu and 801 for Central California. Surprisingly, when differences in search efforts are controlled, overall (alpha) diversity appears to be similar between locations, although site level (beta) diversity is much higher in California. Species richness in California generally increased along a wave exposure gradient and distance from an urban area. Much higher numbers of both invasive and endemic species were found on Oahu. In California, more invertebrate species were found in the 1990s, likely due to an improvement in taxonomic resources since the 1970s, and species composition was different in the two surveys due to the high incidence of rare species. Although some southern species increased in number between the two time periods and some northern species decreased, we detected little evidence of change favoring southern or northern species. These results are in line with recent findings that water temperatures in the Monterey Bay have been in a cooling trend since the 1980s, in contrast to many locations elsewhere in the world.  相似文献   

Explaining divided cities in China   总被引：1，自引：0，他引：1  

Brenda Madrazo  Ronald van Kempen 《Geoforum》2012,43(1):158-168

Explanations of the existence of socio-spatial divisions in Western Europe and the United States revolve around the importance of economic, demographic, political, and socio-cultural macro developments and often also on the role of globalization. Much of the literature also emphasizes the role of institutions, especially the national and local state as well as individual and household constraints and opportunities. Many authors explain socio-spatial divisions by a mix of these factors and developments. This paper provides an account of the current state of affairs concerning the literature and theory on divided cities in China. Concentrating on a selection of 88 articles published in international journals during the last decade, we examine how authors explain urban socio-spatial divisions in Chinese cities. The paper indicates that a five-category framework of trends, policies, players, position, and preferences are useful in addressing the complexity of explanations attributed to current urban divisions and inequalities in Chinese cities. While the spatial patterns in the Western and Chinese contexts share rather similar characteristics, the interplay of mechanisms is significantly different. The influence of the state, its institutions, and the cultural background has a much stronger explanatory power in China than in the West.  相似文献   

First record of Odontaster penicillatus populations (Philippi, 1870) (Echinodermata: Asteroidea) in the Atacama and Antofagasta regions,Chile (Southeast Pacific)     

Leonardo Campos  Fernando Berrios  Brenda B. Hermosillo-Nú?ez  Marco Ortiz 《海洋学报(英文版)》2022,41(12):152-155

We report for the first time the presence of local populations of the starfish Odontaster penicillatus in the regions of Atacama and Antofagasta, Chile. This finding indicates an extension of the distribution limit of 500 km with respect to the last observation made in 2007 in Isla Grande de Atacama. A total of 121 specimens of O. penicillatus were recorded at depths of between 8 m and 24 m. They were associated with rocky substrate and with different species of barnacles, sponges and bryozoans. The presence of O. penicillatus expands the knowledge of the benthic biodiversity of the region, and the development of studies on its ecological importance will be promoted.  相似文献   

Assessing water quality in Marine Protected Areas from Southern California, USA     

Schiff K  Luk B  Gregorio D  Gruber S 《Marine pollution bulletin》2011,62(12):2780-2786

Despite the regulatory mandate to maintain “natural water quality”, there are ?271 storm drain discharges that potentially threaten the 14 designated marine water quality protected areas in Southern California called Areas of Special Biological Significance (ASBS). After sampling 35 site-events, the geomean concentrations of total suspended solids, nutrients, total and dissolved trace metals, and polycyclic aromatic hydrocarbons in the ocean following storm events were similar between reference drainages and ASBS discharge sites. Concentrations of chlorinated hydrocarbons were nondetectable and no post-storm sample exhibited significant toxicity to the endemic purple sea urchin (Strongylocentrotus purpuratus) near ASBS discharge sites. A reference-based threshold was developed and, despite the similarities in average concentrations, there were some individual ASBS discharge sites that were greater than reference background. Cumulatively across all ASBS, the constituents that were most frequently greater than the reference-based threshold were nutrients and general constituents, followed by dissolved and total trace metals.  相似文献   

Gross erosion,net erosion and gross deposition of dust by wind: field data from 17 desert surfaces     

Dirk Goossens  Brenda Buck 《地球表面变化过程与地形》2011,36(5):610-623

Wind erosion measurements were carried out in Nellis Dunes Recreation Area, southern Nevada, USA. Gross erosion (the total mass of sediment effectively blown away from a surface), gross deposition (the total mass of sediment effectively depositing on a surface) and net erosion (the difference in sediment mass before and after an event) were measured for 1 year, on 17 different types of surfaces developed on loose dune sand, compacted sand, loose silt, compacted and/or aggregated silt, rock‐covered sands and silts, mixtures of sand, silt and clay, exposed petrocalcic horizons, gravelly substrata and bedrock. Results showed that net erosion, which is the type of erosion measured in field and laboratory experiments, strongly differs from gross erosion. Activity on a surface is much higher than classic net erosion measurements suggest. Future studies on wind erosion should better acknowledge the distinction between the two types of process. Also, a grain diameter of maximum susceptibility to wind erosion (‘optimum deflation diameter’) near 70 µm as proposed by the aeolian literature only exists for net wind erosion. No such optimum diameter was found for gross wind erosion within the particle range 0–100 µm delineating the transport modes of suspension and modified saltation. In addition, desert surfaces predominantly composed of sand did not show an optimum deflation diameter (for net erosion) around 70 µm. Instead, there was a preferential grain size around 15 µm at which particles were most vulnerable to net emission. Desert surfaces poor in sand showed the classic value of 70 µm. This suggests that interactions exist between the type of surface and the susceptibility of particles to wind erosion. This study is solely based on field data. Although results are supported by two previous wind tunnel studies, more wind tunnel experiments documenting the interactions between gross erosion and gross deposition are necessary. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Post-glacial regional climate variability along the East Antarctic coastal margin—Evidence from shallow marine and coastal terrestrial records     

Elie Verleyen  Dominic A. Hodgson  Koen Sabbe  Holger Cremer  Steven D. Emslie  John Gibson  Brenda Hall  Satoshi Imura  Sakae Kudoh  Gareth J. Marshall  Andrew McMinn  Martin Melles  Louise Newman  Donna Roberts  Steve J. Roberts  Shiv M. Singh  Mieke Sterken  Ines Tavernier  Sergey Verkulich  Evelien Van de Vyver  Wim Van Nieuwenhuyze  Bernd Wagner  Wim Vyverman 《Earth》2011,104(4):199-212

We review the post-glacial climate variability along the East Antarctic coastline using terrestrial and shallow marine geological records and compare these reconstructions with data from elsewhere. Nearly all East Antarctic records show a near-synchronous Early Holocene climate optimum (11.5–9 ka BP), coinciding with the deglaciation of currently ice-free regions and the optimum recorded in Antarctic ice and marine sediment cores. Shallow marine and coastal terrestrial climate anomalies appear to be out of phase after the Early Holocene warm period, and show complex regional patterns, but an overall trend of cooling in the terrestrial records. A Mid to Late Holocene warm period is present in many East Antarctic lake and shallow coastal marine records. Although there are some differences in the regional timing of this warm period, it typically occurs somewhere between 4.7 and 1 ka BP, which overlaps with a similar optimum found in Antarctic Peninsula terrestrial records. The differences in the timing of these sometimes abrupt warm events in different records and regions points to a number of mechanisms that we have yet to identify. Nearly all records show a neoglacial cooling from 2 ka BP onwards. There is no evidence along the East Antarctic coastline for an equivalent to the Northern Hemisphere Medieval Warm Period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the Northern Hemisphere's Little Ice Age. There is a need for well-dated, high resolution climate records in coastal East Antarctica and particularly in Terre Adélie, Dronning Maud Land and Enderby Land to fully understand the regional climate anomalies, the disparity between marine and terrestrial records, and to determine the significance of the heterogeneous temperature trends being measured in the Antarctic today.  相似文献