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61.
Loraine C.V. Jacobs Patricio Peralta-Zamora Francinete Ramos Campos Roberto Pontarolo 《Chemosphere》2013,90(4):1552-1557
In this work, the photocatalytic degradation of aqueous microcystin-LR was studied using TiO2 and ZnO as photocatalysts. The process was optimised and characterised at the bench scale (200 mL); both semiconductors exhibited a high degradation capacity at reaction times of 1 min (degradation greater than 95%). The transient species that were observed indicate that the degradation occurs via the multiple hydroxylation and elimination of the labile peptide residues of the molecule. When photocatalysis was applied in a continuous treatment system (20–50 L), the photocatalytic process exhibited a high degradation efficiency, which resulted in residual microcystin-LR concentrations that were less than 1 μg L?1 (C0 = 5 μg L?1). 相似文献
62.
Molecular methods are useful both to monitor natural communities of bacteria, and to track specific bacterial markers in complex environments. Length-heterogeneity polymerase chain reaction (LH-PCR) and terminal restriction fragment length polymorphism (T-RFLP) of 16S rDNAs discriminate among 16S rRNA genes based on length polymorphisms of their PCR products. With these methods, we developed an alternative indicator that distinguishes the source of fecal pollution in water. We amplify 16S rRNA gene fragments from the fecal anaerobic genus Bacteroides with specific primers. Because Bacteroides normally resides in gut habitats, its presence in water indicates fecal pollution. Molecular detection circumvents the complexities of growing anaerobic bacteria. We identified Bacteroides LH-PCR and T-RFLP ribosomal DNA markers unique to either ruminant or human feces. The same unique fecal markers were recovered from polluted natural waters. We cloned and sequenced the unique markers; marker sequences were used to design specific PCR primers that reliably distinguish human from ruminant sources of fecal contamination. Primers for more species are under development. This approach is more sensitive than fecal coliform assays, is comparable in complexity to standard food safety and public health diagnostic tests, and lends itself to automation and high-throughput. Thus molecular genetic markers for fecal anaerobic bacteria hold promise for monitoring bacterial pollution and water quality. 相似文献
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Degradation of nitrogen containing organic compounds by combined photocatalysis and ozonation 总被引:10,自引:0,他引:10
The combination of TiO2-assisted photocatalysis and ozonation in the degradation of nitrogen-containing substrates such as alkylamines, alkanolamines, heterocyclic and aromatic N-compounds has been investigated. A laboratory set-up was designed and the influence of the structure of the N-compound, the TiO2 and ozone concentration on the formation of breakdown products were examined. The experimental results showed that a considerable increase in the degradation efficiency of the N-compounds is obtained by a combination of photocatalysis and ozonation as compared to either ozonation or photocatalysis only. The mineralization of the model substances was monitored by measurements of the TOC and ion-chromatographic determinations of the formed NO2- and NO3-. The temporal changes of concentrations of breakdown products, such as NH4+, short chain alkyl- and alkanolamines were determined by single column ion chromatography (SCIC) and as well as by electrospray mass spectrometry (EI-MS). 相似文献
66.
Increasing attention is being placed on capping as a relatively new option in managing both contaminated sediments and dredged materials, due to its economic and environmental benefits. Capping denotes the placement of a cover onto potentially hazardous sediments or dredged material dumps to inhibit the transfer of contaminants into the water column. Retention of divalent iron and manganese cations using sandy capping layers containing natural zeolites as a reactive additive (active barrier systems, ABS) is evaluated in this study. Three different natural zeolite (clinoptilolite) rocks, two from deposits in Australia and one from a North-American deposit, were investigated and compared with respect to their mineralogical, physical and chemical properties. In particular, results from batch and column experiments show that ABS based on these materials can efficiently demobilise iron and manganese from percolating, anoxic pore water by cation exchange under favourable conditions. The retention, however, may be reduced strongly where competitive exchange with divalent cations such as calcium prevails or where mobile colloidal pore water constituents such as clay minerals or humic substances bind fractions of the dissolved iron or manganese. Therefore, the potential of ABS as a means for in situ remediation has to be evaluated diligently with particular regard to the pore water composition of the sediment to be capped. 相似文献
67.
David W. Wolfe Lewis Ziska Curt Petzoldt Abby Seaman Larry Chase Katharine Hayhoe 《Mitigation and Adaptation Strategies for Global Change》2008,13(5-6):555-575
Most prior climate change assessments for U.S. agriculture have focused on major world food crops such as wheat and maize. While useful from a national and global perspective, these results are not particularly relevant to the Northeastern U.S. agriculture economy, which is dominated by dairy milk production, and high-value horticultural crops such as apples (Malus domestica), grapes (Vitis vinifera), sweet corn (Zea mays var. rugosa), cabbage (Brassica oleracea var. capitata), and maple syrup (sugar maple, Acer saccharum). We used statistically downscaled climate projections generated by the HadCM3 atmosphere–ocean general circulation model, run with Intergovernmental Panel on Climate Change future emissions scenarios A1fi (higher) and B1 (lower), to evaluate several climate thresholds of direct relevance to agriculture in the region. A longer (frost-free) growing season could create new opportunities for farmers with enough capital to take risks on new crops (assuming a market for new crops can be developed). However, our results indicate that many crops will have yield losses associated with increased frequency of high temperature stress, inadequate winter chill period for optimum fruiting in spring, increased pressure from marginally over-wintering and/or invasive weeds, insects, or disease, or other factors. Weeds are likely to benefit more than cash crops from increasing atmospheric carbon dioxide. Projections of thermal heat index values for dairy cows indicate a substantial potential negative impact on milk production. At the higher compared to lower emissions scenario, negative climate change effects will occur sooner, and impact a larger geographic area within the region. Farmer adaptations to climate change will not be cost- or risk-free, and the impact on individual farm families and rural communities will depend on commodity produced, available capital, and timely, accurate climate projections. 相似文献
68.
Regional climate change projections for the Northeast USA 总被引:1,自引:0,他引:1
Katharine Hayhoe Cameron Wake Bruce Anderson Xin-Zhong Liang Edwin Maurer Jinhong Zhu James Bradbury Art DeGaetano Anne Marie Stoner Donald Wuebbles 《Mitigation and Adaptation Strategies for Global Change》2008,13(5-6):425-436
Climate projections at relevant temporal and spatial scales are essential to assess potential future climate change impacts on climatologically diverse regions such as the northeast United States. Here, we show how both statistical and dynamical downscaling methods applied to relatively coarse-scale atmosphere-ocean general circulation model output are able to improve simulation of spatial and temporal variability in temperature and precipitation across the region. We then develop high-resolution projections of future climate change across the northeast USA, using IPCC SRES emission scenarios combined with these downscaling methods. The projections show increases in temperature that are larger at higher latitudes and inland, as well as the potential for changing precipitation patterns, particularly along the coast. While the absolute magnitude of change expected over the coming century depends on the sensitivity of the climate system to human forcing, significantly higher increases in temperature and in winter precipitation are expected under a higher as compared to lower scenario of future emissions from human activities. 相似文献
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The multiphase optimization strategy (MOST) and the sequential multiple assignment randomized trial (SMART): two novel evaluation methods for developing optimal training programs 下载免费PDF全文
Current methodologies in training evaluation studies largely employ a single method entitled random confirmatory trials, prompting several concerns. First, practitioners and researchers often analyze the effectiveness of their entire omnibus training, rather than the individual elements or identifiable components of the training program. This slows the testing of theory and development of optimal training programs. Second, a common training is typically administered to all employees within an organization or workgroup; however, certain factors may cause individualized training to be more effective. Given these concerns, the current paper presents two training evaluation methodologies to overcome these problems: the multiphase optimization strategy and sequential multiple assignment randomized trials. The multiphase optimization strategy is a method to evaluate a standard training, which emphasizes the importance of a multi‐stage training evaluation process to analyze individual training elements. In contrast, sequential multiple assignment randomized trial is used to evaluate an adaptive training that varies over time and/or trainees. These methodologies jointly overcome the problems noted earlier, and they can be integrated to address several of the key challenges facing training researchers and practitioners. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献