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581.
582.
583.
Mobility of trace metals associated with urban particles exposed to natural waters of various salinities from the Gironde Estuary, France 总被引:1,自引:1,他引:0
Jörg Schäfer Stefan Norra Daniel Klein Gérard Blanc 《Journal of Soils and Sediments》2009,9(4):374-392
Background, aim and scope Urban systems are hot spots of environmental pollution caused by manifold anthropogenic activities generating traffic-related,
industrial and domestic emissions. Besides air, soil and groundwater pollution, pollution of surface water systems is of major
concern because they are often (ab)used to export waste of various consistence out of urban areas and become contaminated
on varying scales. The Gironde Estuary (southwest France) is affected by various anthropogenic contaminations derived from
historic polymetallic pollution mainly due to former mining and ore-treatment and, additionally, from agriculture and urban
areas. Although detailed knowledge is available on the impact of mining and anthropogenic activities on the water quality
of the Gironde Estuary, almost nothing is known on the urban impact, even though the Garonne Branch which is one tributary
of the Gironde system crosses the large urban agglomeration of Bordeaux. The present work links urban geochemistry and estuary
research and aims at evaluating the mobility of potentially toxic trace elements (Cd, Cu, Zn, V, Co, Mo, Pb) associated with
urban particles under estuarine conditions owing to the particles' role as potential vectors transporting urban pollutants
into the estuary. For this, environmentally available fractions of trace elements in representative urban particles (urban
dust, road sediment, riverbank sediment, construction materials) from the city of Bordeaux were extracted by natural estuarine
waters of varying salinities and compared to commonly applied HNO3 extractions.
Materials and methods For the assessment of the urban particles' contribution to the pollution of the Gironde/Garonne system, various particle types
were sampled in Bordeaux: road sediments, urban bulk deposition, construction materials (concrete, asphalt, tile and gravel)
and flood sediments. Potentially environmental available fractions of Cd, Cu, Zn, V, Co, Mo and Pb were extracted by means
of concentrated HNO3, estuarine freshwaters and waters of two different salinities (S = 15 and S = 31). Analysis of trace elements was carried out by means of quadrupole inductively coupled plasma-mass spectrometry. Furthermore,
single particles from road sediments were characterised with scanning electron microscopy (SEM).
Results SEM analysis clearly showed that some particles contained fairly high concentrations of potentially toxic trace elements.
Extractions of materials investigated by varying acidities and salinities documented that the potentially bioavailable fractions
extracted by concentrated HNO3 may cover wide concentration ranges. Natural estuarine waters of various salinities (S = 0.5; S = 15; S = 31) extracted high proportions of Co, Ni, Cu, Zn and Cd from urban particles, especially for high-salinity water (S = 31). Extractions with freshwater revealed the lowest concentrations of desorbed trace elements. Particulate Mo, Pb and
V showed similar or lower mobility in saline water compared with freshwater, depending on the sample type.
Discussion Trace element mobility in estuarine waters varied according to the type of urban particles and depended on salinity for Co,
Ni, Cu, Zn and Cd. This is of high importance for towns located directly at the coast or for cities like Bordeaux, where water
courses crossing the agglomerations are connected to saline water masses. Since trace elements desorbed from particles in
saline waters may become highly bioavailable, they bear a potential risk for organisms. Comprehensive studies on the behaviour
of urban particles in estuarine waters and the related potential environmental impact are still missing.
Conclusions Saline waters mobilise relatively high amounts of Co, Ni, Cu, Zn and Cd from urban particles suggesting considerable metal
fluxes from riverine urban systems into coastal waters. Although estimates of trace metal inputs by urban bulk deposition
(urban dust) and other types of urban particles are preliminary for Bordeaux and may bear important uncertainties due to several
assumptions and extrapolation to the annual timescale, the orders of magnitude are probably realistic. Thus, these fluxes
are not negligible and need (1) further and improved observation and (2) to be taken into account in both mass budgets at
the estuary scale and emission control strategies.
Recommendations and perspectives New approaches combining geochemical and mineralogical characterisation of single urban particle types help identify their
role in metal emission into the environment and develop potential limitation strategies (e.g. the ban of priority pollutants
in tyres, etc.). Therefore, prioritisation of urban particle sources in terms of fluxes, reactivity of associated pollutants
and feasibility of emission reduction is strongly recommended. Coastal cities should integrate extractions of urban particles
with saline water into their environmental monitoring programs owing to the fact that saline conditions might cause efficient
desorption of potentially toxic trace elements. In continental cities, winter salting is likely to induce intense mobilisation
of metals from road sediments that may then reach the aquatic environment, instead of being retained in runoff decantation
reservoirs followed by subsequent disposal/treatment with road sediments. However, also particles from continental cities
reach coastal waters via rivers and have to be assessed with respect to trace metal desorption under various salinities. There
is a strong need for the quantification of fluxes and for the identification of carrier phases and reactivity of metals exported
from urban areas to aquatic systems. 相似文献
584.
The glmS ribozyme is the only natural catalytic RNA known to require a small-molecule activator for catalysis. This catalytic RNA functions as a riboswitch, with activator-dependent RNA cleavage regulating glmS messenger RNA expression. We report crystal structures of the glmS ribozyme in precleavage states that are unliganded or bound to the competitive inhibitor glucose-6-phosphate and in the postcleavage state. All structures superimpose closely, revealing a remarkably rigid RNA that contains a preformed active and coenzyme-binding site. Unlike other riboswitches, the glmS ribozyme binds its activator in an open, solvent-accessible pocket. Our structures suggest that the amine group of the glmS ribozyme-bound coenzyme performs general acid-base and electrostatic catalysis. 相似文献
585.
Habashi JP Judge DP Holm TM Cohn RD Loeys BL Cooper TK Myers L Klein EC Liu G Calvi C Podowski M Neptune ER Halushka MK Bedja D Gabrielson K Rifkin DB Carta L Ramirez F Huso DL Dietz HC 《Science (New York, N.Y.)》2006,312(5770):117-121
Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-beta (TGF-beta) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-beta signaling and can be prevented by TGF-beta antagonists such as TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder. 相似文献
586.
A E Klein J Freiberg S Same M A Carroll 《Journal of the Association of Official Analytical Chemists》1989,72(6):881-882
A new colorimetric method is described for the determination of enzymatic activity of subtilisin in cleaning products. The procedure is more rapid and precise than the casein digestion methods commonly used to assay protease activity. The principle of the colorimetric method depends on the determination rate of p-nitrophenol released on hydrolysis of N-CBZ-L-leucine-p-nitrophenyl ester at pH 8.0 by subtilisin, with correction for any nonenzymatic (spontaneous) hydrolysis of the substrate. Because of the broad range of hydrolytic activity of this enzyme, and the difficulties in predicting its proteolytic activity, this hydrolytic rate was chosen as a general indicator of subtilisin enzyme behavior. The slope for 7 replicate standard curves generated over a 6 week period exhibited a relative standard deviation of 7.5%, and 8.0% for 20 replicates with an enzyme cleaning product. Papain does not interfere with this assay. 相似文献
587.
Hong Jie Di Keith C. Cameron Andriy Podolyan Grant R. Edwards Cecile A. M. de Klein Robyn Dynes Roshean Woods 《Journal of Soils and Sediments》2016,16(9):2252-2262
Purpose
In grazed pastures, nitrous oxide (N2O), a powerful greenhouse gas and an ozone depletion substance, is mostly emitted from animal excreta, particularly animal urine-N returned to the soil during grazing. We conducted a series of four field lysimeter and plot experiments to assess the potential of using gibberellic acid (GA) and/or alternative pastures or forage crops to mitigate N2O emissions from outdoor dairy farming systems.Materials and methods
Pasture and forage plants assessed in the experiments included Italian ryegrass (Lolium multiflorum L.), lucerne (Medicago sativa L.), diverse pastures (including plantain (Plantago lanceolata L.), chicory (Cichorium intybus L.), perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.)), fodder beet (Beta vulgaris L.), kale (Brassica oleracea L.), as well as the standard perennial ryegrass and white clover (RG/WC) pastures. N2O was determined using a standard static chamber method in the field either on top of lysimeters or field plots.Results and discussion
The results showed that the application of GA to urine-treated lysimeters with Italian ryegrass, lucerne or RG/WC pastures did not result in lower N2O emissions. However, the use of diverse pastures which included plantain with a lower urine-N loading rate at about 500 kg N ha?1 significantly decreased N2O emissions by 46 % compared with standard RG/WC with a urine-N loading rate at 700 kg N ha?1. However, when urine-N was applied at the same rates (at 500 or 700 kg N ha?1), the N2O emissions were similar between the diverse and the standard RG/WC pastures. This would indicate that it is the N-loading rate in the urine from the different pastures that determines the N2O emissions from different pastures or forages, rather than the plants per se. The N2O emissions from cow urine from fodder beet were 39 % lower than from kale with the same urine-N application rate (300 kg N ha?1).Conclusions
These results suggest that N2O emissions can potentially be reduced by incorporating diverse pastures and fodder beet into the grazed pasture farm system. Further studies on possible mechanisms for the lower N2O emissions from the different pastures or forages would be useful.588.
W.?Dana?FlandersEmail author Mitch?Klein Paige?Tolbert 《Journal of Agricultural, Biological & Environmental Statistics》2005,10(2):246-257
Generalized additive models (GAMs) have become popular in the air pollution epidemiology literature. Two problems, recently
surfaced, concern implementation of these semiparametric models. The first problem, easily corrected, was laxity of the default
convergence criteria. The other, noted independently by Klein, Flanders, and Tolbert, and Ramsay, Burnett, and Krewski concerned
variance estimates produced by commercially available software. In simulations, they were as much as 50% too small. We derive
an expression for a variance estimator for the parametric component of generalized additive models that can include up to
three smoothing splines, and show how the standard error (SE) estimated by this method differs from the corresponding SE estimated
with error in a study of air pollution and emergency room admissions for cardiorespiratory disease. The derivation is based
on asymptotic linearity. Using Monte Carlo experiments, we evaluated performance of the estimator in finite samples. The estimator
performed well in Monte Carlo experiments, in the situations considered. However, more work is needed to address performance
in additional situations. Using data from our study of air pollution and cardiovascular disease, the standard error estimated
using the new method was about 10% to 20% larger than the biased, commercially available standard error estimate. 相似文献
589.
E. A. Henry L. J. Dodge-Murphy G. N. Bigham S. M. Klein 《Water, air, and soil pollution》1995,80(1-4):489-498
A mass balance model was developed to simulate mercury (Hg) cycling in Onondaga Lake, New York. MERC4, a U.S. Environmental Protection Agency model of the physical and biogeochemical transport and transformation of Hg, was modified by the addition of input from two supporting models (Fish Bioenergetics Model 2 and a lake eutrophication model) to model the transport of Hg into and out of plankton and fish. The model calculates the concentrations of total Hg, methylmercury, elemental Hg, and ionic Hg in both dissolved and particulate forms in the water column. The model was calibrated to an extensive data set of temporally and spatially variable Hg concentrations in Onondaga Lake in 1992. In addition to standard transport processes of advection and dispersion included in MERC4, the Onondaga Lake Mercury Model includes remineralization to simulate release of Hg from settling particulates before incorporation into sediment. The model provides an analytical framework for understanding and predicting the behavior of Hg in Onondaga Lake and has potential use in evaluating the relative impact of different source control and remedial alternatives. 相似文献
590.
Maureen M. Jennings Timothy D. Perkins Mark T. Hemmerlein Richard M. Klein 《Water, air, and soil pollution》1992,65(3-4):237-244
A flow-through system for in situ, near real-time, sequential measurements of rainfall pH and depth was developed for monitoring of precipitation in sites lacking electric power. The system is easily fabricated from readily available instruments and materials, portable, relatively inexpensive and requires minimal maintenance. It also operates independently of AC power making it ideal for use in remote areas. Initial field testing of this system on Camels Hump, Vermont, took place over the period of July to August 1990, during which twenty-seven individual storm events were monitored. The system proved to be robust and reliable, providing rainfall pH and depth information with high (programmable) temporal resolution for unattended periods of up to a week. 相似文献