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71.
Photoreactivity of humic substances: relationship between fluorescence and singlet oxygen production 总被引:1,自引:0,他引:1
Christian Coelho Ghislain Guyot Alexandra ter Halle Luciano Cavani Claudio Ciavatta Claire Richard 《Environmental Chemistry Letters》2011,9(3):447-451
Humic substances are natural compounds abundantly present in the environment. They play a significant role in the natural
attenuation of pollution in surface water due to their capacity to generate reactive species upon solar light excitation.
Finding physico chemical parameters related to this property would be of a great help in the prediction studies of the organic
pollutants fate. In this work, we investigated relationships between the ability of the humic substances to produce singlet
oxygen and their fluorescence properties. For this, a series of sixteen humic acids, fulvic acids, and water-extractable organic
matter from soils were studied. The steady-state singlet oxygen concentrations in the irradiated humic substances solutions
were measured by monitoring the loss of furfuryl alcohol added as a singlet oxygen scavenger. The emission spectra of the
sixteen samples were also recorded. Values of the steady-state singlet oxygen concentrations and the emission intensities
showed significant variations among the humic samples and a parallel increase. Thus, here we demonstrate that the rate of
singlet oxygen production and the emission intensity of the humic samples are correlated, the best correlation being obtained
for emission wavelengths between 500 and 580 nm. This correlation which was never reported until now can be used to estimate
the singlet oxygen-production capacity of the humic substances based on their fluorescent properties. 相似文献
72.
Céline Dupont Francesca Romana Grati Kwong Wai Choy Sylvie Jaillard Jérôme Toutain Marie-Laure Maurin Jose Antonio Martínez-Conejero Claire Beneteau Aurélie Coussement Denise Molina-Gomes Nina Horelli-Kuitunen Azzedine Aboura Anne-Claude Tabet Justine Besseau-Ayasse Bettina Bessieres-Grattagliano Giuseppe Simoni Gustavo Ayala Brigitte Benzacken François Vialard 《黑龙江环境通报》2015,35(1):35-43
73.
74.
Luanne Y. Steffy Angela L. McGinty Claire Welty Susan S. Kilham 《Journal of the American Water Resources Association》2004,40(5):1269-1275
ABSTRACT: Valley Creek watershed is a small stream system that feeds the Schuylkill River near Philadelphia, Pennsylvania. The watershed is highly urbanized, including over 17 percent impervious surface cover (ISC) by area. Imperviousness in a watershed has been linked to fish community structure and integrity. Generally, above 10 to 12 percent ISC there is marked decline in fish assemblages with fish being absent above 25 percent ISC. This study quantifies the importance of ground water in maintaining fish species diversity in subbasins with over 30 percent ISC. Valley Creek contains an atypical fish assemblage in that the majority of the fish are warm‐water species, and the stream supports naturally reproducing brown trout, which were introduced and stocked from the early 1900s to 1985. Fish communities were quantified at 13 stations throughout the watershed, and Simpson's species diversity index was calculated. One hundred and nine springs were located, and their flow rates measured. A cross covariance analysis between Simpson's species diversity index and spring flow rates upstream of fish stations was performed to quantify the spatial correlation between these two variables. The correlation was found to be highest at lag distances up to about 400 m and drop off significantly beyond lag distances of about 800 m. 相似文献
75.
Legislation on the protection of biodiversity (e.g., European Union Habitat and Bird Directives) increasingly requires ecological impact assessment of human activities. However, knowledge and understanding of relevant ecological processes and species responses to different types of impact are often incomplete. In this paper we demonstrate with a case study how impact assessment can be carried out for situations where data are scarce but some expert knowledge is available. The case study involves two amphibian species, the great crested newt (Triturus cristatus) and the natterjack toad (Bufo calamita) in the nature reserve the Meinweg in the Netherlands, for which plans are being developed to reopen an old railway track called the Iron Rhine. We assess the effects of this railway track and its proposed alternatives (scenarios) on the metapopulation extinction time and the occupancy times of the patches for both species using a discrete-time stochastic metapopulation model. We quantify the model parameters using expert knowledge and extrapolated data. Because of our uncertainty about these parameter values, we perform a Monte Carlo uncertainty analysis. This yields an estimate of the probability distribution of the model predictions and insight into the contribution of each distinguished source of uncertainty to this probability distribution. We show that with a simple metapopulation model and an extensive uncertainty analysis it is possible to detect the least harmful scenario. The ranking of the different scenarios is consistent. Thus, uncertainty analysis can enhance the role of ecological impact assessment in decision making by making explicit to what extent incomplete knowledge affects predictions. 相似文献
76.
Jeffrey L. Arthur Robert G. Haight Claire A. Montgomery Stephen Polasky 《Environmental Modeling and Assessment》2002,7(2):81-89
Two approaches to formulating the reserve site selection problem when species occurrence data is probabilistic were solved for terrestrial vertebrates in a small set of potential reserve sites in Oregon. The expected coverage approach, which maximizes the sum of the occurrence probabilities, yielded solutions that covered more species on average in Monte Carlo simulations than the threshold approach, which maximizes the number of species for which the occurrence probability exceeds some threshold. 相似文献
77.
Horwell CJ Allen AG Mather TA Patterson JE 《Journal of environmental monitoring : JEM》2004,6(7):630-635
A novel, low-cost passive sampling procedure for monitoring of volcanogenic hydrogen sulfide is reported. The technique is based on absorption of H2S onto treated sections of photographic paper, which are housed in plastic film canisters during exposure. The H2S reacts with silver halide in the photographic paper, causing a colour-change reaction from white, through brown, to black, depending on concentration of atmospheric H2S. The sampler is sensitive to < 30 ppb to approximately 1000 ppb of H2S. Here we present results from a series of optimization and quantification experiments. An active sampling procedure for rapid H2S measurement is also reported, based on absorption of H2S onto Whatman No. 41 cellulose filters treated with silver nitrate, and was shown to be quantitative using a single filter at flow rates <1.0 L min(-1) for collection of <200 microg of sulfide (as H2S). Determination of sulfide collected on the substrates was performed using a rapid flow-injection technique based on the fluorescence quenching of fluorescein mercuric acetate (FMA) by sulfide. This was optimized at a FMA concentration of 8 mg L(-1), at which 100% quenching was obtained at a solution sulfide concentration of 3 mg L(-1). 相似文献
78.
Claire L. Schelske 《Journal of the American Water Resources Association》1989,25(6):1119-1130
ABSTRACT: Lake Okeechobee, the third largest lake in the United States, is a shallow, mixing basin with annual total phosphorus concentrations ranging from 50–100 μg P/L. Data, mainly from unpublished agency reports, are analyzed to determine if nutrients limit phytoplankton, to describe spatial and temporal variability in trophic state parameters, and to evaluate conclusions obtained from empirical trophic state models. Algal bioassay experiments that have been used to assess nutrient limitation have produced equivocal results. However, seasonal minima in orthophosphorus and inorganic nitrogen indicate that both nutrients may be limiting seasonally. Strong, but reverse north-south gradients and large seasonal changes in phosphorus and nitrogen concentrations, show that empirical models based on annual phosphorus loadings or concentrations are not adequate to predict chlorophyll concentrations or other trophic state variables. Spatially-segmented, multi-class phytoplankton-nutrient models of seasonal phytoplankton responses that are coupled with hydrodynamic models may provide predictability in assessing effects of changing nutrient loads on phytoplankton composition and standing crop. Successful modeling efforts of responses to nutrients also must deal with resuspended and benthic algae, periphyton, and emergent and submergent aquatic plants that must play important trophic roles in some of the lake basin. 相似文献
79.
80.
Art Daniel Zhanhe Wu Bruce Bennetts Howard Slater Robert Osborn Julianne Jackson Vladimir Pupko John Nelson Geoff Watson Claire Cooke-Yarborough Christine Loo 《黑龙江环境通报》2001,21(12):1034-1048
The parental origin of triploidy in 19 cases was examined by inheritance of DNA microsatellites and by methylation patterns of SNRPN or PW71 (where parents' blood was unavailable). The fetal and placental morphology on these cases was reviewed. The phenotype of the fetuses with non-mosaic triploidy was assessed in relation to the two types described by McFadden and Kalousek. Of the diandric fetuses three of the six showed mild-to-moderate symmetrical growth retardation and the other three had growth characteristics in accordance with their gestational ages. This study would suggest the fetal triploid ‘Type 1’ definition be modified to ‘well grown to moderate symmetrical IUGR’ to allow for such variation. In the digynic fetuses (McFadden/Kalousek Type 2) there were poor growth characteristics with IUGR being more severe and asymmetrical. The diandric fetuses were as common as digynic fetuses in this series. The ratio of diandric to digynic specimens was 11:8 but if only fetal specimens (not embryos or mosaic children) were included the ratio was 6:5. Many diandric conceptions end as partial moles but later in gestation diandric fetuses may be well grown. It is proposed that there may be a survival barrier for diandric fetuses early in gestation (possibly based on the proportion of vascularised placental villi), although once this is passed the diandric fetuses are comparatively more viable and better grown than digynic fetuses. In the XXY triploid fetuses, 5/6 had hypoplastic or ambiguous external genitalia (two were recorded as of female phenotype) as has been reported previously. In these, the gonadal histology was testicular in all the diandrics but in the single digynic XXY case, sex reversal was complete with normal uterus and Fallopian tubes and the gonads were histologically ovaries. Two triploid/diploid mosaics were proven to be due to digyny. The probable cause is delayed incorporation of the second polar body into a blastomere and there was evidence of identical alleles from the same sperm being present in both diploid and triploid cells. In one of these triploid/diploid mosaics in which there was a termination of pregnancy (TOP) after prenatal karyotyping the diploid cell line had trisomy 16 which was not evident in the triploid line. This trisomy was probably of post-zygotic origin and we suggest the fetus was rescued by the prominence of the triploid line. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献