共查询到20条相似文献,搜索用时 15 毫秒
1.
Despite its importance for the understanding of element cycles in ecosystems, organic matter (OM) quality has remained an elusive property that is difficult to measure. In this study, two new approaches, both of which taking into account the complete biochemical composition of the organic material during the decomposition process, have been combined to solve this problem. First, following the continuous-quality theory where quality is defined as a measure of substrate availability to the decomposers, initial litter OM qualities of a range of plant species from two experiments on litter decomposition were estimated and resulted in highly accurate fits of observed mass loss during decomposition. Applying the same theory, qualities of the litters at all stages of decomposition were then calculated. By comparison, the initial qualities of the same litters were estimated from conventional chemical fractions and resulted in much lower accurate fits. Second, near-infrared reflectance spectroscopy (NIRS), a highly precise physical method of characterising biochemical composition of OM, was used to obtain a unique spectral signature of each sample. Calibrations were performed between spectral data and calculated qualities on the first half of the sample set and the calibration equations were applied to the second half of the sample set. Results show that theoretical litter OM quality can be calibrated and predicted precisely using NIRS. OM quality, defined according to a theoretical concept of substrate availability to decomposers, then contains and summarises all the relevant biochemical information. We demonstrate how the combination of NIRS and theory allows us to accurately measure OM quality. Measurement of OM quality provides an access to a fundamental property of organic matter and opens up new possibilities for studying element cycles in ecosystems. 相似文献
2.
Xiao Wei Xin Chen Xia Wang Weiwei Zheng Dong Zhang Dajun Tian Songhui Jiang Choon Nam Ong Gengsheng He Weidong Qu 《PloS one》2013,8(3)
Drinking water chlorination plays a pivotal role in preventing pathogen contamination against water-borne disease. However, chemical disinfection leads to the formation of halogenated disinfection by products (DBPs). Many DBPs are highly toxic and are of health concern. In this study, we conducted a comprehensive measurements of DBPs, including iodoacetic acid (IAA), iodoform (IF), nine haloacetic acids and four trihalomethanes in drinking waters from 13 water plants in Shanghai, China. The results suggested that IAA and IF were found in all the water treatment plants, with maximum levels of 1.66 µg/L and 1.25 µg/L for IAA and IF, respectively. Owing to deterioration of water quality, the Huangpu River has higher IAA and IF than the Yangtze River. Our results also demonstrated that low pH, high natural organic matter, ammonia nitrogen, and iodide in source waters increased IAA and IF formation. Compared to chlorine, chloramines resulted in higher concentration of iodinated DBP, but reduced the levels of trihalomethanes. This is the first study to reveal the widespread occurrence of IAA and IF in drinking water in China. The data provide a better understanding on the formation of iodinated disinfection byproducts and the findings should be useful for treatment process improvement and disinfection byproducts controls. 相似文献
3.
Evelyn Krull Deborah Haynes Sébastien Lamontagne Peter Gell David McKirdy Gary Hancock Janine McGowan Ronald Smernik 《Biogeochemistry》2009,92(1-2):9-25
Like many other coastal systems across the world, the Coorong lagoonal ecosystem (South Australia) has degraded over the last 100 years; in this case as a result of extensive regulation and diversions of water across the Murray-Darling Basin following European settlement. To evaluate whether the sources of organic matter (OM) supporting its food-web have changed since the inception of water management and barrage construction, sedimentary OM was characterised in cores spanning the Coorong’s salinity gradient at depths representative of the last 100 years over which the management alterations to river and estuarine flow were most marked. Detailed 210Pb, 137Cs and Pu dating in conjunction with palaeolimnological data (Pinus pollen) allowed for the reconstruction of the timing of substantial changes observed in the composition of the OM, most of which occur during the early 1950s, concurrent with management-related variations in water flow and salinity. Negative shifts in δ13C of up to 8.3‰ in the 2–10 and <2 μm fractions after the 1950s suggest a pronounced alteration in biogeochemical cycling or in the origin of OM. Elemental ratios and δ13C values of potential sources are inconclusive as to the cause of these biogeochemical changes. However, 13C-NMR spectra of the sediments suggest that degraded phytoplankton constitutes a large proportion of today’s OM and also reveal that an OM source rich in lignin was present prior to the 1950s. The high δ13C (?18.3‰) and low C/N (7.5) signatures of the lignin-bearing sediments are inconsistent with a C3 terrestrial OM source and instead suggest that the lignin-bearing seagrass Ruppia megacarpa (δ13C of ?13‰) contributed to a large degree to the sediment of the North Lagoon. R. megacarpa once was abundant in the North Lagoon but today has all but vanished from the system. Thus, only through a combination of isotopic and spectroscopic techniques was it possible to effectively decipher the changes in the composition of OM deposited throughout the Coorong over space and time. These results have important implications for research in estuarine OM dynamics in other geographic locations. Specifically, utilising complementary analytical techniques may sometimes be essential in reliably determining OM sources and processes in estuaries and lagoons. 相似文献
4.
Jean-Baptiste Poitelon Michel Joyeux Bénédicte Welté Jean-Pierre Duguet Eric Prestel Michael S. DuBow 《Journal of industrial microbiology & biotechnology》2010,37(2):117-128
We examined the variations of bacterial populations in treated drinking water prior to and after the final chlorine disinfection
step at two different surface water treatment plants. For this purpose, the bacterial communities present in treated water
were sampled after granular activated carbon (GAC) filtration and chlorine disinfection from two drinking water treatment
plants supplying the city of Paris (France). Samples were analyzed after genomic DNA extraction, polymerase chain reaction
(PCR) amplification, cloning, and sequencing of a number of 16S ribosomal RNA (rRNA) genes. The 16S rDNA sequences were clustered
into operational taxonomic units (OTUs) and the OTU abundance patterns were obtained for each sample. The observed differences
suggest that the chlorine disinfection step markedly affects the bacterial community structure and composition present in
GAC water. Members of the Alphaproteobacteria and Betaproteobacteria were found to be predominant in the GAC water samples after phylogenetic analyses of the OTUs. Following the chlorine disinfection
step, numerous changes were observed, including decreased representation of Proteobacteria phylotypes. Our results indicate that the use of molecular methods to investigate changes in the abundance of certain bacterial
groups following chlorine-based disinfection will aid in further understanding the bacterial ecology of drinking water treatment
plants (DWTPs), particularly the disinfection step, as it constitutes the final barrier before drinking water distribution
to the consumer’s tap. 相似文献
5.
Jennifer A. J. Dungait Andrew S. Gregory Andrew P. Whitmore 《Global Change Biology》2012,18(6):1781-1796
Mechanisms to mitigate global climate change by sequestering carbon (C) in different ‘sinks' have been proposed as at least temporary measures. Of the major global C pools, terrestrial ecosystems hold the potential to capture and store substantially increased volumes of C in soil organic matter (SOM) through changes in management that are also of benefit to the multitude of ecosystem services that soils provide. This potential can only be realized by determining the amount of SOM stored in soils now, with subsequent quantification of how this is affected by management strategies intended to increase SOM concentrations, and used in soil C models for the prediction of the roles of soils in future climate change. An apparently obvious method to increase C stocks in soils is to augment the soil C pools with the longest mean residence times (MRT). Computer simulation models of soil C dynamics, e.g. RothC and Century, partition these refractory constituents into slow and passive pools with MRTs of centuries to millennia. This partitioning is assumed to reflect: (i) the average biomolecular properties of SOM in the pools with reference to their source in plant litter, (ii) the accessibility of the SOM to decomposer organisms or catalytic enzymes, or (iii) constraints imposed on decomposition by environmental conditions, including soil moisture and temperature. However, contemporary analytical approaches suggest that the chemical composition of these pools is not necessarily predictable because, despite considerable progress with understanding decomposition processes and the role of decomposer organisms, along with refinements in simulation models, little progress has been made in reconciling biochemical properties with the kinetically defined pools. In this review, we will explore how advances in quantitative analytical techniques have redefined the new understanding of SOM dynamics and how this is affecting the development and application of new modelling approaches to soil C. 相似文献
6.
Observation volumes and {gamma}-factors in two-photon fluorescence fluctuation spectroscopy
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Fluorescence fluctuation spectroscopy has become an important measurement tool for investigating molecular dynamics, molecular interactions, and chemical kinetics in biological systems. Although the basic theory of fluctuation spectroscopy is well established, it is not widely recognized that saturation of the fluorescence excitation can dramatically alter the size and profile of the fluorescence observation volume from which fluorescence fluctuations are measured, even at relatively modest excitation levels. A precise model for these changes is needed for accurate analysis and interpretation of fluctuation spectroscopy data. We here introduce a combined analytical and computational approach to characterize the observation volume under saturating conditions and demonstrate how the variation in the volume is important in two-photon fluorescence correlation spectroscopy. We introduce a simple approach for analysis of fluorescence correlation spectroscopy data that can fully account for the effects of saturation, and demonstrate its success for characterizing the observed changes in both the amplitude and relaxation timescale of measured correlation curves. We also discuss how a quantitative model for the observed phenomena may be of broader importance in fluorescence fluctuation spectroscopy. 相似文献
7.
Jennifer L. A. Shaw Paul Monis Laura S. Weyrich Emma Sawade Mary Drikas Alan J. Cooper 《Applied and environmental microbiology》2015,81(18):6463-6473
Drinking water assessments use a variety of microbial, physical, and chemical indicators to evaluate water treatment efficiency and product water quality. However, these indicators do not allow the complex biological communities, which can adversely impact the performance of drinking water distribution systems (DWDSs), to be characterized. Entire bacterial communities can be studied quickly and inexpensively using targeted metagenomic amplicon sequencing. Here, amplicon sequencing of the 16S rRNA gene region was performed alongside traditional water quality measures to assess the health, quality, and efficiency of two distinct, full-scale DWDSs: (i) a linear DWDS supplied with unfiltered water subjected to basic disinfection before distribution and (ii) a complex, branching DWDS treated by a four-stage water treatment plant (WTP) prior to disinfection and distribution. In both DWDSs bacterial communities differed significantly after disinfection, demonstrating the effectiveness of both treatment regimes. However, bacterial repopulation occurred further along in the DWDSs, and some end-user samples were more similar to the source water than to the postdisinfection water. Three sample locations appeared to be nitrified, displaying elevated nitrate levels and decreased ammonia levels, and nitrifying bacterial species, such as Nitrospira, were detected. Burkholderiales were abundant in samples containing large amounts of monochloramine, indicating resistance to disinfection. Genera known to contain pathogenic and fecal-associated species were also identified in several locations. From this study, we conclude that metagenomic amplicon sequencing is an informative method to support current compliance-based methods and can be used to reveal bacterial community interactions with the chemical and physical properties of DWDSs. 相似文献
8.
Zhongmou Liu Xianze Wang Zhen Luo Mingxin Huo Jinghui Wu Hongliang Huo Wu Yang 《PloS one》2015,10(12)
The magnetic graphene oxide (MGO) was successfully synthesised by the in situ chemical co-precipitation method with Fe3+, Fe2+ and graphene oxide (GO) in laboratory and, was used as an adsorbent for disinfection by-product (DBP) precursors removing from four natural surface water samples. The results indicate that various DBPs formation significantly decreased by 7–19% to 78–98% for the four samples after MGO treatment and, the treatment process was rapidly reached equilibrium within 20 minutes. The DBP precursors removal efficiency decreased with the increasing pH value from 4 to 10. Hydrophobic compounds (humic acid and fulvic acid) are more sensitive to MGO, whereas hydrophilic and nitrogenous compounds (aromatic proteins) are more insensitive. MGO could be regenerated by using 20% (v/v) ethanol and, the DBP precursors removal efficiency can stay stable after five cycles. These results indicate that MGO can be utilized as a promising adsorbent for the removal of DBP precursors from natural surface water. 相似文献
9.
A microwave technique for digesting foliage samples was developed and evaluated for quantifying low levels of Hg by cold vapor atomic fluorescence spectroscopy, CVAFS. The method meets three criteria: (1) to digest all sample material completely and consistently, (2) to reduce sample digestion time to less than one hour, and (3) to maintain a low analytical blank. Mean recovery of NIST standards was 90±6%. Samples that were analyzed by this technique and by Instrumental Neutron Activation Analysis compared within 15%. This method also compared within 15% of hot acid digestion methods on samples prepared and analyzed by CVAFS at different laboratories in the First International Mercury in Foliage Intercomparison of Methods (FIM)2. The largest source of variability in all of the interlaboratory comparisons was sample inhomogeneity rather than analytical error. 相似文献
10.
Solubilization and insertion into reverse micelles of the major myelin transmembrane proteolipid 总被引:1,自引:0,他引:1
The Folch-Pi proteolipid has been isolated from bovine white matter and characterized with respect to phospholipid and glycolipid composition. The protein-lipid complex has been solubilized in aqueous reverse micelles of di(2-ethylhexyl) sodium sulfosuccinate and isooctane. Solubilization of this otherwise water-insoluble proteolipid requires small amounts of water, the percent of solubility being maximum for a low molar ratio of water to surfactant (Wo = 5.6). Unlike hydrophilic proteins, the extent of incorporation into the micellar system is negligible at 50 mM surfactant and reaches 90Vo only at 300 mM. However, the conformation of the proteolipid in reverse micelles as studied by fluorescence emission spectroscopy and circular dichroism was not affected by variations of the surfactant concentration. These results are consistent with the peculiar properties of the aqueous environment of the proteolipid within the reverse micelles and may reflect the membrane-like character of these bio-assemblies. 相似文献
11.
Caslake LF Connolly DJ Menon V Duncanson CM Rojas R Tavakoli J 《Applied and environmental microbiology》2004,70(2):1145-1150
Contaminated water causes an estimated 6 to 60 billion cases of gastrointestinal illness annually. The majority of these cases occur in rural areas of developing nations where the water supply remains polluted and adequate sanitation is unavailable. A portable, low-cost, and low-maintenance solar unit to disinfect unpotable water has been designed and tested. The solar disinfection unit was tested with both river water and partially processed water from two wastewater treatment plants. In less than 30 min in midday sunlight, the unit eradicated more than 4 log10 U (99.99%) of bacteria contained in highly contaminated water samples. The solar disinfection unit has been field tested by Centro Panamericano de Ingenieria Sanitaria y Ciencias del Ambiente in Lima, Peru. At moderate light intensity, the solar disinfection unit was capable of reducing the bacterial load in a controlled contaminated water sample by 4 log10 U and disinfected approximately 1 liter of water in 30 min. 相似文献
12.
Large amounts of labile organic carbon in permafrost soils of northern Alaska 总被引:1,自引:0,他引:1
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Carsten W. Mueller Janet Rethemeyer Jenny Kao‐Kniffin Sebastian Löppmann Kenneth M. Hinkel James G. Bockheim 《Global Change Biology》2015,21(7):2804-2817
Permafrost‐affected soils of the northern circumpolar region represent 50% of the terrestrial soil organic carbon (SOC) reservoir and are most strongly affected by climatic change. There is growing concern that this vast SOC pool could transition from a net C sink to a source. But so far little is known on how the organic matter (OM) in permafrost soils will respond in a warming future, which is governed by OM composition and possible stabilization mechanisms. To investigate if and how SOC in the active layer and adjacent permafrost is protected against degradation, we employed density fractionation to separate differently stabilized SOM fractions. We studied the quantity and quality of OM in different compartments using elemental analysis, 13C solid‐phase nuclear magnetic resonance (13C‐NMR) spectroscopy, and 14C analyses. The soil samples were derived from 16 cores from drained thaw lake basins, ranging from 0 to 5500 years of age, representing a unique series of developing Arctic soils over time. The normalized SOC stocks ranged between 35.5 and 86.2 kg SOC m?3, with the major amount of SOC located in the active layers. The SOC stock is dominated by large amounts of particulate organic matter (POM), whereas mineral‐associated OM especially in older soils is of minor importance on a mass basis. We show that tremendous amounts of over 25 kg OC per square meter are stored as presumably easily degradable OM rich in carbohydrates. Only about 10 kg OC per square meter is present as presumably more stable, mineral‐associated OC. Significant amounts of the easily degradable, carbohydrate‐rich OM are preserved in the yet permanently frozen soil below the permafrost table. Forced by global warming, this vast labile OM pool could soon become available for microbial degradation due to the continuous deepening of the annually thawing active layer. 相似文献
13.
Derivatization strategies for the determination of biogenic amines in wines by chromatographic and electrophoretic techniques 总被引:1,自引:0,他引:1
Hernández-Cassou S Saurina J 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2011,879(17-18):1270-1281
This paper revises the derivatization approaches for the determination of biogenic amines in wines. Since most of these amines display poor spectroscopic features to be detected by UV absorption or emission (fluorescence) spectroscopy, derivatization is necessary to attain the desired sensitivity. Reagents such as o-phthaldialdehyde, fluorenylmethylchloroformate, dansyl-Cl and dabsyl-Cl have widely been used for analytical labeling through amino group. A comparison of features of off- and on-line pre- and post chromatographic/electrophoretic labeling is given using 1,2-naphthoquinone-4-sulfonate (NQS) as an example. The evaluation of the influence of the wine sample composition on the derivatization process indicates that pre-column labeling may undergo more severe matrix effects. 相似文献
14.
Laurie F. Caslake Daniel J. Connolly Vilas Menon Catriona M. Duncanson Ricardo Rojas Javad Tavakoli 《Applied microbiology》2004,70(2):1145-1150
Contaminated water causes an estimated 6 to 60 billion cases of gastrointestinal illness annually. The majority of these cases occur in rural areas of developing nations where the water supply remains polluted and adequate sanitation is unavailable. A portable, low-cost, and low-maintenance solar unit to disinfect unpotable water has been designed and tested. The solar disinfection unit was tested with both river water and partially processed water from two wastewater treatment plants. In less than 30 min in midday sunlight, the unit eradicated more than 4 log10 U (99.99%) of bacteria contained in highly contaminated water samples. The solar disinfection unit has been field tested by Centro Panamericano de Ingenieria Sanitaria y Ciencias del Ambiente in Lima, Peru. At moderate light intensity, the solar disinfection unit was capable of reducing the bacterial load in a controlled contaminated water sample by 4 log10 U and disinfected approximately 1 liter of water in 30 min. 相似文献
15.
16.
Wenbo Ding Jianfeng Zhou Jia Cheng Zhaozheng Wang Hengyu Guo Changsheng Wu Sixing Xu Zhiyi Wu Xing Xie Zhong Lin Wang 《Liver Transplantation》2019,9(27)
Water disinfection at the point of use (POU) has enormous social and economic significance, especially for rural areas or catastrophes. To tackle the requirements of power independence and cost control in such applications, the concept of TriboPump is proposed, which is a low‐cost, hand‐powered water disinfection system. The system consists of three functional parts: a tubular coaxial‐electrode copper ionization cell (CECIC) as the disinfection device, a disk triboelectric nanogenerator (D‐TENG) as the power source, and a coaxial mechanical structure including the water pump. The adoption of D‐TENG can make the system adaptive to varying system resistances without additional power management circuits. Moreover, the integration of CECIC and TENG can successfully turn their intrinsic limitations into advantages and a synergic effect is achieved. With the integrated design, the system can effectively disinfect the water while pumping it solely by hand power. The cost estimate of the whole system can be as low as $10 for a 2‐year service. It is believed that the whole system design provides a feasible one‐stop and cost‐efficient solution for POU water pumping and disinfection, which will ideally be suitable the rural areas or sudden‐onset catastrophes. 相似文献
17.
《IRBM》2008,29(1):13-19
Raman spectroscopy is a useful tool to investigate the molecular composition of biological samples. Source separation methods can be used to efficiently separate dense information recorded by Raman spectra. Distorting effects such as fluorescence background, peak misalignment or peak width heterogeneity break the linear generative model required by the source separation methods. Preprocessing steps are needed to compensate these deforming effects and make recorded Raman spectra fit the linear generative model of source separation methods. We show in this paper how efficiency of source separation methods is deeply dependent on preprocessing steps applied to raw dataset. Resulting improvements are illustrated through the study of the numerical dewaxing of Raman signal of a human skin biopsy. The applied source separation methods are a classical independent component analysis (ICA) algorithm named joint approximate diagonalization of eigenmatrices (JADE), and two positive source separation methods called non-negative matrix factorization (NMF) and maximum likelihood positive source separation (MLPSS). 相似文献
18.
José L. J. Ledesma Martyn N. Futter M. Blackburn Fredrik Lidman Thomas Grabs Ryan A. Sponseller Hjalmar Laudon Kevin H. Bishop Stephan J. Köhler 《Ecosystems》2018,21(2):297-315
The boreal ecoregion supports about one-third of the world’s forest. Over 90% of boreal forest streams are found in headwaters, where terrestrial–aquatic interfaces are dominated by organic matter (OM)-rich riparian zones (RZs). Because these transition zones are key features controlling catchment biogeochemistry, appropriate RZ conceptualizations are needed to sustainably manage surface water quality in the face of a changing climate and increased demands for forest biomass. Here we present a simple, yet comprehensive, conceptualization of RZ function based on hydrological connectivity, biogeochemical processes, and spatial heterogeneity. We consider four dimensions of hydrological connectivity: (1) laterally along hillslopes, (2) longitudinally along the stream, (3) vertically down the riparian profile, and (4) temporally through event-based and seasonal changes in hydrology. Of particular importance is the vertical dimension, characterized by a ‘Dominant Source Layer’ that has the highest contribution to solute and water fluxes to streams. In addition to serving as the primary source of OM to boreal streams, RZs shape water chemistry through two sets of OM-dependent biogeochemical processes: (1) transport and retention of OM-associated material and (2) redox-mediated transformations controlled by RZ water residence time and availability of labile OM. These processes can lead to both retention and release of pollutants. Variations in width, hydrological connectivity, and OM storage drive spatial heterogeneity in RZ biogeochemical function. This conceptualization provides a useful theoretical framework for environmental scientists and ecologically sustainable and economically effective forest management in the boreal region and elsewhere, where forest headwaters are dominated by low-gradient, OM-rich RZs. 相似文献
19.
LC-MS based global metabolite profiling of grapes: solvent extraction protocol optimisation 总被引:1,自引:0,他引:1
Georgios Theodoridis Helen Gika Pietro Franceschi Lorenzo Caputi Panagiotis Arapitsas Mattias Scholz Domenico Masuero Ron Wehrens Urska Vrhovsek Fulvio Mattivi 《Metabolomics : Official journal of the Metabolomic Society》2012,8(2):175-185
Optimal solvent conditions for grape sample preparation were investigated for the purpose of metabolite profiling studies,
with the aim of obtaining as many features as possible with the best analytical repeatability. Mixtures of water, methanol
and chloroform in different combinations were studied as solvents for the extraction of ground grapes. The experimental design
used a two stage study to find the optimum extraction medium. The extracts obtained were further purified using solid phase
extraction and analysed using a UPLC full scan TOF MS with both reversed phase and hydrophilic interaction chromatography.
The data obtained were processed using data extraction algorithms and advanced statistical software for data mining. The results
obtained indicated that a fairly broad optimal area for solvent composition could be identified, containing approximately
equal amounts of methanol and chloroform and up to 20% water. Since the water content of the samples was variable, the robustness
of the optimal conditions suggests these are appropriate for large scale profiling studies for characterisation of the grape
metabolome. 相似文献
20.
Pulmonary delivery of therapeutic peptides and proteins has many advantages including high relative bioavailability, rapid
systemic absorption and onset of action and a non-invasive mode of administration which improves patient compliance. In this
study, we investigated the effect of spray-drying (SD) and spray freeze-drying processes on the stability and aerosol performance
of parathyroid hormone (PTH) (1-34) microparticles. In this study, the stabilisation effect of trehalose (a non-reducing sugar)
and Brij 97 (a non-ionic surfactant) on spray-dried PTH particles was assessed using analytical techniques including circular
dichroism (CD), fluorescence spectroscopy, modulated differential scanning calorimetry and an in vitro bioactivity assay. Physical characterisation also included electron microscopy, tap density measurement and laser light diffraction.
The aerosol aerodynamic performance of the formulations was assessed using the Andersen cascade impactor. Based on these studies,
a formulation for spray freeze-drying was selected and the effects of the two particle engineering techniques on the biophysical
stability and aerosol performance of the resulting powders was determined. CD, fluorescence spectroscopy and bioactivity data
suggest that trehalose when used alone as a stabilising excipient produces a superior stabilising effect than when used in
combination with a non-ionic surfactant. This highlights the utility of CD and fluorescence spectroscopy studies for the prediction
of protein bioactivity post-processing. Therefore, a method and formulation suitable for the preparation of PTH as a dry powder
was developed based on spray-drying PTH with trehalose as a stabiliser with the bioactivity of SD PTH containing trehalose
being equivalent to that of unprocessed PTH. 相似文献