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1.
The purpose of this research was to apply near-infrared (NIR) spectroscopy with chemometrics to predict the change of pharmaceutical
properties of antipyrine granules during granulation by regulation of the amount of water added. The various kinds of granules
(mean particle size, 70–750 μm) were obtained from the powder mixture (1 g of antipyrine, 6 g of hydroxypropylcellulose, 140
g of lactose, and 60 g of potato starch) by regulation of the added water amount (11–19 wt/wt%) in a high-speed mixer. The
granules were characterized by mean particle size, angle of repose, compressibility, tablet porosity, and tablet hardness
as parameters of pharmaceutical properties. To predict the pharmaceutical properties, NIR spectra of the granules were measured
and analyzed by principal component regression, (PCR) analysis. The mean particle size of the granules increased from 81 μm
to 650 μm with an increase in the amount of water, and it was possible to make larger spherical granules with narrow particle
size distribution using a high-speed mixer. Angle of repose, compressibility, and porosity of the tablets decreased with an
increase of added water, but tablet hardness increased. The independent calibration models to evaluate particle size, angle
of repose, and tablet porosity and hardness were established by using PCR based on NIR spectra of granules, respectively.
The correlation coefficient constants of calibration curves for prediction of mean particle size, angle of repose, tablet
porosity, and tablet hardness were 0.9109, 0.8912, 0.7437, and 0.8064, respectively. It is possible that the pharmaceutical
properties of the granule, such as mean particle size, angle of repose, tablet porosity, and tablet hardness, could be predicted
by an NIR-chemometric method. 相似文献
2.
The present work focuses on the study of the physical characteristics of olive stone wooden residues at the prospect of its
use as a bulking material in compost process. The physical characteristics that were studied according to particle mesh classification,
were the apparent density, porosity, water holding capacity, air free space and air pressure drop. From the experimental results,
it was proved that only the fraction of 6.8–12.5 mesh, which is 29.40% of the substrate, could maintain the moisture in the
optimum range 40–60%. The fraction of the particles of 2.6–23.6 mesh, which was 74.68% of the substrate, had appropriate porosity
for composting. It was also proved that for dried substrate and air velocity 300 m h−1, acceptable pressure drop (10 cm H2O m−1) was observed for the fraction of the particles of 2.6–27.5 mesh, which was 80.08% of the substrate, while for dried substrate
and air velocity 150 m h−1, the respective fraction was particles of 2.6–37.9 mesh which accounted for the 89.48% of the substrate. Conclusively, olive
oil processing solid residues have the physical characteristics, so as to be used for composting or as a substrate for co-composting
with high strength wastewater. 相似文献
3.
It is well known that pulp density and particle size determine the available surface area concentration and have an influence
in the overall rate of bioleaching of minerals. As metal solubilization takes place through the surface area of the particles,
it can be expected that different combinations of pulp densities and particle sizes giving the same surface area concentration
would determine the same leaching rate. The objective of this work was to test this hypothesis on the effect of surface area
concentration, pulp density and particle size of the biooxidation of a pyritic gold concentrate by the thermophilic Archaeon
Sulfolobus metallicus in shake flasks. The gold concentrate was used at 2.5%, 5%, 10%, and 15% w/v pulp density and at four size fractions: 150–106,
106–75, 75–38 and –38 μm. Temperature was 68°C and the initial pH was 2.0. Results showed that the volumetric productivities
of iron and sulfate depend not only on the surface area concentration but also on pulp density and particle size considered
separately. These two variables not only determine surface area but also exert additional effects on the process, so the hypothesis
was not confirmed. Maximum attained iron productivity was 1.042 g/l day with the 75–38 μm fraction at 5% pulp density. Maximum
sulfate productivity was 4.279 g/l day with the 75–38 μm fraction at 10% pulp density. 相似文献
4.
The aim of the present investigation was to develop and optimize gastroretentive floating system of amoxicillin for the efficient
treatment of peptic ulcer induced by Helicobacter pylori infection. Floating microballoons were developed using central composite design (CCD), and optimization was done by employing
response surface methodology. The selected independent variables were cellulose acetate phthalate, drug–Eudragit S100 ratio,
and the ratio of dichloromethane/ethanol/isopropyl alcohol. The selected dependent variables were yield, mean particle size,
buoyancy, encapsulation efficiency, and drug release within 8 h. A quadratic polynomial model was generated which had linear,
interaction, and quadratic terms to predict and evaluate the independent variables with respect to the dependent variables.
Results showed that selected independent variables significantly affect the yield (30.53–82.71%), particle size (31.62–47.03 μm),
buoyancy (42.68–95.75%), encapsulation efficiency (56.96–93.13%), and cumulative drug release from the microballoons (34.01–74.65%).
The interaction and quadratic terms were also found to affect the process variables. An excellent agreement was found between
the actual value and predicted value. In conclusion, it can be said that CCD is a valuable second-degree design to develop
and optimize GFS of amoxicillin which in turn provides a basis to localize the drug release in the gastric region for effective
treatment of H. pylori-mediated infection. 相似文献
5.
The purpose of this research was to obtain directly compressible agglomerates of naproxen containing disintegrant by spherical
crystallization technique. Acetone–water containing hydroxypropyl celloluse (HPC) and disintegrant was used as the crystallization
system. In this study croscarmellose sodium (Ac–Di–Sol) was employed as disintegrant. The agglomerates were characterized
by differential scanning calorimetry (DSC), powder X-ray diffraction (XRPD), and scanning electron microscopy and were evaluated
for flow, packing and tableting properties and drug release. The growth of particle size and the spherical form of the agglomerates
resulted in formation of products with good flow and packing properties. The improved compaction properties of the agglomerated
crystals were due to their fragmentation occurred during compression. DSC and XRPD studies showed that naproxen particles,
crystallized in the presence of HPC and Ac–Di–Sol did not undergo structural modifications. The dissolution rate of naproxen
from tablets made of naproxen–(Ac–Di–Sol) agglomerates was enhanced significantly because of including the disintegrant in
to the particles. This was attributed to an increase in the surface area of the practically water insoluble drug is exposed
to the dissolution medium. In conclusion the spherical crystallization technique developed in this study is suitable for obtaining
agglomerates of drug with disintegrant. 相似文献
6.
Havránek Vladimír Kučera Jan Horáková Jitka Voseček Václav Smolík JiŘí Schwarz Jaroslav Sýkorová Ivana 《Biological trace element research》1999,(1):431-442
A comparison of instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) results for sizefractionated
atmospheric aerosols (“coarse” and “fine” fractions with an equivalent aerodynamic diameter of 2–10 Μm and < 2 Μm, respectively,
or the PM10 fraction) showed that PIXE yielded significantly lower results for the PM10 and coarse fractions, especially for
elements with a low Z resulting from a particle size effect. Somewhat lower PIXE results were also obtained for the fine fraction
of atmospheric aerosols. A correction is also needed for irregularly shaped deposits of combustion aerosols collected by a
cascade impactor in 11 size fractions ranging from 0.016 to 14.3 Μm, as well as for thick samples of fly and bottom ashes.
An equivalent layer thickness (ELT) model is proposed to correct the matrix effects in PIXE. The approaches for the calculation
of ELT using a comparison of PIXE and INAA results or by comparing PIXE results obtained using two different incident proton
beam energies (1.31 and 2.35 MeV) are described. The correction for the ash pellets and irregular deposits are also discussed. 相似文献
7.
8.
Takahito Yoshioka Khan M. G. Mostofa Eiichi Konohira Eiichiro Tanoue Kazuhide Hayakawa Mikio Takahashi Shingo Ueda Masanori Katsuyama Tamara Khodzher Nadezhda Bashenkhaeva Irina Korovyakova Larisa Sorokovikova Ludomira Gorbunova 《Limnology》2007,8(1):29-44
Distributions of molecular size and fluorescence properties of dissolved organic matter (DOM) in the Lake Biwa and Lake Baikal
watersheds were investigated using the cross-flow ultrafiltration technique and three-dimensional fluorescence measurements.
From the fluorescence properties, protein-like substances were usually found in the 0.1 μm-GF/F fraction (the Durapore membrane
retentate of the GF/F filtrate) of the lake DOM. The results indicated autochthonous production of protein-like organic-matters
in the lake environment. Fulvic acid (FA)-like components were composed of two fractions with respect to fluorescence properties
and molecular size. Two FA-like fluorescence peaks, which showed different fluorescence peak positions in the excitation-emission
matrix (EEM), were partly fractionated by the molecular size of 5000 daltons (5 kDa). The FA-like fluorescence peak position
of the <5-kDa fraction was observed at the shorter wavelength region compared with that of the fraction between 5 kDa and
0.1 μm (5 kDa20.1 μm fraction). A blue shift of the FA-like fluorescence peak position as well as a decrease in the molecular
size of the DOM was observed in lake samples. The relative contribution of the <5 kDa fraction to the DOC concentration was
high in lake waters (68%–79%) compared with river waters (44%–68%), suggesting characteristic changes in molecular size between
riverine and lacustrine DOM. DOM of the 5 kDa–0.1 μm fraction was relatively higher in river waters than in lake waters. These
findings coincided with in situ distributions of the fluorescence properties and molecular size of DOM found in both stream
and lake environments. These results indicate that FA-like substances from forested watersheds are decomposed qualitatively
and quantitatively in the river-lake environment by photochemical and biological processes. 相似文献
9.
Mamdouh M. Ghorab Heba M. Abdel-Salam Marwa A. El-Sayad Mohammed M. Mekhel 《AAPS PharmSciTech》2004,5(4):63-68
The purpose of this research was to evaluate β-cyclodextrin (β-CD) as a vehicle, either singly or in blends with lactose (spray-dried
or monohydrate), for preparing a meloxicam tablet. Aqueous solubility of meloxicam in presence of β-CD was investigated. The
tablets were prepared by direct compression and wet granulation techniques. The powder blends and the granules were evaluated
for angle of repose, bulk density, compressibility index, total porosity, and drug content. The tablets were subjected to
thickness, diameter, weight variation test, drug content, hardness, friability, disintegration time, and in vitro dissolution
studies. The effect of β-CD on the bioavailability of meloxicam was also investigated in human volunteers using a balanced
2-way crossover study. Phase-solubility studies indicated an AL-type diagram with inclusion complex of 1∶1 molar ratio. The powder blends and granules of all formulations showed satisfactory
flow properties, compressibility, and drug content. All tablet formations prepared by direct compression or wet granulation
showed acceptable mechanical properties. The dissolution rate of meloxicam was significantly enhanced by inclusion of β-CD
in the formulations up to 30%. The mean pharmacokinetic parameters (Cmax, Ke, and area under the curve [AUC]0−∞) were significantly increased in presence of β-CD. These results suggest that β-CD would facilitate the preparation of meloxicam
tablets with acceptable mechanical properties using the direct compression technique as there is no important difference between
tablets prepared by direct compression and those prepared by wet granulation. Also, β-CD is particularly useful for improving
the oral bioavailablity of meloxicam. 相似文献
10.
Summary The possible use of particle size separation of soils in water was tested for preparing fractions rich in ‘unknown’-N, which
constitutes between 41 and 46% of the total N. Ten particle size fractions ranging from <0.2 to>1,000.0 μm were separated
from the A horizon of the Bainsville soil, an Orthic Humic Gleysol, and from the Bh horizon of the Armadale soil, a poorly
drained Podzol. The distribution of N (hydrolyzable-, amino acid-, protein-, amino sugar-, ammonia-, ‘unknown’-and unidentified-N)
in the initial soils and in each size fraction was determined. While particle size separation did not yield fractions which
contained essentially only ‘unknown’-N and few known N-components, it was possible to isolate fractions which were either
rich in amino acid-or protein-N or in NH3-N. In general, the finer size fractions tended to be enriched in amino acid-N while NH3-N was more prominent in the coarser fractions. The amino sugar-N content of all size fractions was low. 相似文献
11.
To clarify the ecological significance of the association of sulfate-reducing bacteria (SRB) with sediment particle size,
SRB utilizing lactate (l-SRB), propionate (p-SRB) and acetate (a-SRB) were examined with different sizes of sediment particles in a hypertrophic freshwater lake using the anaerobic plate
count method. The numbers ofl-SRB anda-SRB were 104–105 colony forming units (CFU) per ml in the 0–3 cm layer and 102–103 CFU ml−1 in the 10–13 cm layer while the numbers ofp-SRB were one or two orders lower than those ofl-SRB anda-SRB. A sediment suspension was fractionated into four fractions (<1, 1–10, 10–94 and >94 μm). The highest proportions ofl-SRB anda-SRB were found in the 10–94 μm fraction: 66–97% forl-SRB and 53–98% fora-SRB. The highest proportion ofp-SRB was found in the >94 μm fraction (70–74%). These results indicate that most SRB were associated with sediment particles.
One isolate from an acetate-utilizing enrichment culture was similar toDesulfotomaculum acetoxidans, a spore-forming sulfate-reducing bacterium. When lactate and sulfate were added to sediment samples,l-SRB anda-SRB in the <10 μm-fraction grew more rapidly than those in whole sediment for the first 2 days. This result suggests that
nutrients uptake by free-living and small particle-associated (<10 μm) SRB is higher than that by SRB associated with larger
particles. 相似文献
12.
Stability of oil-in-water emulsions during freezing and thawing is regulated by the phase transitions occurring in the continuous
and dispersed phases upon thermal treatments and by the composition of the interfacial membrane. In the present study, the
impact of the water phase formulation (0–2.5–5–10–20–30–40% w/w sucrose), the interfacial composition [whey protein isolates (WPI) or sodium caseinate (NaCas) used at different concentrations],
and the particle size on the stability of hydrogenated palm kernel oil (30% w/w)-in-water systems was investigated. Phase/state behaviour of the continuous and dispersed phases and emulsion destabilisation
were studied by differential scanning calorimetry. System morphology was observed by particle size analysis and optical microscopy.
The presence of sucrose in the aqueous phase and reduced particle size distribution significantly improved emulsion stability.
WPI showed better stabilising properties than NaCas at lipid to protein ratios of 10:1, 7.5:1, 5:1 and 4:1. Increased WPI
concentration significantly improved emulsion resistance to breakdown during freeze–thaw cycling. NaCas showed poor stabilising
properties and was ineffective in reducing emulsion destabilisation at 0% sucrose at all the lipid to protein ratios. 相似文献
13.
The purpose of the research was to evaluate Sterculia foetida gum as a hydrophilic matrix polymer for controlled release preparation. For evaluation as a matrix polymer; characterization
of Sterculia foetida gum was done. Viscosity, pH, scanning electronmicrographs were determined. Different formulation aspects considered were:
gum concentration (10–40%), particle size (75–420 μm) and type of fillers and those for dissolution studies; pH, and stirring
speed were considered. Tablets prepared with Sterculia foetida gum were compared with tablets prepared with Hydroxymethylcellulose K15M. The release rate profiles were evaluated through
different kinetic equations: zero-order, first-order, Higuchi, Hixon-Crowell and Korsemeyer and Peppas models. The scanning
electronmicrographs showed that the gum particles were somewhat triangular. The viscosity of 1% solution was found to be 950
centipoise and pH was in range of 4–5. Suitable matrix release profile could be obtained at 40% gum concentration. Higher
sustained release profiles were obtained for Sterculia foetida gum particles in size range of 76–125 μm. Notable influences were obtained for type of fillers. Significant differences were
also observed with rotational speed and dissolution media pH. The in vitro release profiles indicated that tablets prepared from Sterculia foetida gum had higher retarding capacity than tablets prepared with Hydroxymethylcellulose K15M prepared tablets. The differential
scanning calorimetry results indicated that there are no interactions of Sterculia foetida gum with diltiazem hydrochloride. It was observed that release of the drug followed through surface erosion and anomalous
diffusion. Thus, it could be concluded that Sterculia foetida gum could be used a controlled release matrix polymer. 相似文献
14.
Satyabrata Mohapatra Y. K. Mishra A. M. Warrier Reji Philip S. Sahoo A. K. Arora D. K. Avasthi 《Plasmonics (Norwell, Mass.)》2012,7(1):25-31
Nanocomposite thin films consisting of Cu nanoparticles embedded in silica matrix were synthesized by atom beam co-sputtering
technique. Plasmonic, optical, and structural properties of the nanocomposite films were investigated by using ultraviolet
(UV)–visible absorption spectroscopy, nonlinear optical transmission, X-ray diffraction (XRD), and low-frequency Raman scattering.
UV–visible absorption studies revealed the surface plasmon resonance absorption at 564 nm which showed a red shift with increase
in Cu fraction. XRD results together with surface plasmon resonance absorption confirmed the presence of Cu nanoparticles
of different size. Low-frequency Raman studies of nanocomposite films revealed breathing modes in Cu nanoparticles. Nanocomposites
with lower metal fractions were found to behave like optical limiters. The possibility of controllably tuning the optical
nonlinearity of these nanocomposites could enable them to be the potential candidates for applications in nanophotonics. 相似文献
15.
Saeed Shojaee Parastou Emami Ahmad Mahmood Yemisi Rowaiye Alusine Dukulay Waseem Kaialy Iain Cumming Ali Nokhodchi 《AAPS PharmSciTech》2015,16(6):1281-1289
Polyethylene oxide has been researched extensively as an alternative polymer to hydroxypropyl methylcellulose (HPMC) in controlled drug delivery due to its desirable swelling properties and its availability in a number of different viscosity grades. Previous studies on HPMC have pointed out the importance of particle size on drug release, but as of yet, no studies have investigated the effect of particle size of polyethylene oxide (polyox) on drug release. The present study explored the relationship between polymer level and particle size to sustain the drug release. Tablets produced contained theophylline as their active ingredient and consisted of different polyethylene oxide particle size fractions (20–45, 45–90, 90–180 and 180–425 μm). It was shown that matrices containing smaller particle sizes of polyox produced harder tablets than when larger polyox particles were used. The release studies showed that matrices consisting of large polyox particles showed a faster release rate than matrices made from smaller particles. Molecular weight (MW) of the polymer was a key determining step in attaining sustained release, with the high MW of polyox resulting in a delayed release profile. The results showed that the effect of particle size on drug release was more detrimental when a low concentration of polyox was used. This indicates that care must be taken when low levels of polyox with different particle size fractions are used. More robust formulations could be obtained when the concentration of polyox is high. Differential scanning calorimetry (DSC) traces showed that particle size had no major effect on the thermal behaviour of polyox particles.KEY WORDS: DSC traces, particle size, polyox, sustained release, theophylline 相似文献
16.
K. Bunzl W. Kracke G. I. Agapkina A. Tikhomirov A. I. Shcheglov 《Radiation and environmental biophysics》1998,37(3):195-200
Radiocesium is normally bound only rather weakly and unspecifically by humic substances, in contrast to the actinides Pu
and Am. Recently, however, it was observed that fallout 137Cs in the soil solution from an Of-horizon of a podzol forest soil (slightly decomposed plant material) was associated essentially
only with one single size fraction of the humic substances. In deeper soil layers with well humified material (AOh-horizon),
radiocesium was associated with all size fractions of the dissolved organic matter (DOM). To examine whether this unexpected
behaviour is also observable for DOM isolated from other soils, we determined the association of fallout 137Cs,90Sr,238Pu, 239+240Pu and 241Am with various size fractions of DOM from in situ soil solutions isolated from two layers (0–2 cm and 2–5 cm) of two grassland
soils (a soddy podzolic soil and a peat soil) within the 10 km zone of the nuclear reactor at Chernobyl (Ukraine). The four
size fractions of DOM as obtained by gel filtration of the soil solution were (mean nominal molecular weight in daltons):
fraction I: ≥2000, fraction II: 1300; fraction III: 560, fraction IV: inorganic compounds. The results for the well humified
DOM (humus accumulation horizon of podzol, deeper layer of peat soil) showed that Pu and Am are essentially associated with
the high molecular weight fractions, while Sr is present only in the `inorganic' fraction. Radiocesium is found in all the
size fractions separated. A quite similar pattern was also found for Pu, Am, and Sr in the soil solution from only slightly
decomposed plant material (0–2 cm of peat soil), but not for radiocesium. This radionuclide was again essentially only observable
in one single low molecular weight fraction of DOM. The above results thus support our recent observations in the different
horizons of a forest podzol mentioned above, even though no reason for the different binding of radiocesium by well humified
soil organic matter and by only slightly decomposed plant material can be given at present. The data demonstrate, however,
that information on only the total amount of a radionuclide in the soil solution will not be sufficient to interpret or predict
its fate adequately in the soil.
Received: 13 February 1998 / Accepted in revised form: 14 July 1998 相似文献
17.
Daraghmeh N Rashid I Al Omari MM Leharne SA Chowdhry BZ Badwan A 《AAPS PharmSciTech》2010,11(4):1558-1571
A co-processed excipient was prepared from commercially available crystalline mannitol and α-chitin using direct compression
as well as spray, wet, and dry granulation. The effect of the ratio of the two components, percentage of lubricant and particle
size, on the properties of the prepared co-processed excipient has been investigated. α-Chitin forms non-hygroscopic, highly
compactable, disintegrable compacts when co-processed with crystalline mannitol. The compaction properties of the co-processed
mannitol–chitin mixture were found to be dependent upon the quantity of mannitol added to chitin, in addition to the granulation
procedure used. Optimal physicochemical properties of the excipient, from a manufacturing perspective, were obtained using
a co-processed mannitol–chitin (2:8, w/w) mixture prepared by wet granulation (Cop-MC). Disintegration time, crushing strength, and friability of tablets, produced
from Cop-MC using magnesium stearate as a lubricant, were found to be independent of the particle size of the prepared granules.
The inherent binding and disintegration properties of the compressed Cop-MC are useful for the formulation of poorly compressible,
high-strength, and low-strength active pharmaceutical ingredients. The ability to co-process α-chitin with crystalline mannitol
allows chitin to be used as a valuable industrial pharmaceutical excipient. 相似文献
18.
Sustained release mucoadhesive amoxicillin tablets with tolerance to acid degradation in the stomach were studied. The sustained-release
tablets of amoxicillin were prepared from amoxicillin coated with ethyl cellulose (EC) and then formulated into tablets using
chitosan (CS) or a mixture of CS and beta-cyclodextrin (CD) as the retard polymer. The effects of various (w/w) ratios of EC/amoxicillin, the particle sized of EC coated amoxicillin and the different (w/w) ratios of CS/CD for the retard polymer, on the amoxicillin release profile were investigated. The physicochemical properties
of the EC coated amoxicillin particles and tablets were determined by scanning electron microscopy, Fourier-transform infrared
spectroscopy, X-ray diffraction, and differential scanning calorimetry. The result showed that the release profiles of amoxicillin
were greatly improved upon coating with EC, while the inclusion of CD to the CS retardant additionally prolonged the release
of the drug slightly. Overall, a sustained release of amoxicillin was achieved using amoxicillin coated with EC at a (w/w) ratio of 1:1 and a particle size of 75–100 μm. Therefore, the tablet formulation of amoxicillin may be an advantageous alternative
as an orally administered sustained-release formulation for the treatment of peptic ulcers. 相似文献
19.
Particle size effects in bioleaching of pyrite by acidophilic thermophile Sulfolobus metallicus (BC) 总被引:4,自引:0,他引:4
The effect of mineral particle size on the bioleaching of pyrite by the acidophilic thermophile Sulfolobus metallicus was investigated in a batch bioreactor. Decreasing the particle size from a mean diameter of 202 micron (size fraction: 150–180 micron)
to a mean diameter of 42.5 micron (size fraction: 25–45 micron) enhanced the bioleaching rate from 0.05 kg m−3 h−1 to 0.098 kg m−3 h−1. The particle size distribution of the mineral in this range did not influence the morphology and growth kinetics of the
cells. The values of specific growth rate (μ) and yield factor (Y) were 0.018–0.025 h−1 and 0.67 × 1011–1.45 × 1011 cells (g iron)−1, respectively. Decreasing the particle size of the mineral to a mean diameter of 6.40 micron (size fraction <25 micron) adversely
influenced the activity of the cells. The presence of fine particles apparently damaged the structure of the cells, resulting
in their inability to oxidise pyrite.
Received: 11 December 1998 / Accepted: 9 April 1999 相似文献
20.
Nitrogen deposition effects on soil organic matter chemistry are linked to variation in enzymes,ecosystems and size fractions 总被引:2,自引:0,他引:2
A. Stuart Grandy Robert L. Sinsabaugh Jason C. Neff Martina Stursova Donald R. Zak 《Biogeochemistry》2008,91(1):37-49
Recent research has dramatically advanced our understanding of soil organic matter chemistry and the role of N in some organic
matter transformations, but the effects of N deposition on soil C dynamics remain difficult to anticipate. We examined soil
organic matter chemistry and enzyme kinetics in three size fractions (>250 μm, 63–250 μm, and <63 μm) following 6 years of
simulated atmospheric N deposition in two ecosystems with contrasting litter biochemistry (sugar maple, Acer saccharum—basswood, Tilia americana and black oak, Quercus velutina—white oak, Q. alba). Ambient and simulated (80-kg NO3
−–N ha−1 year−1) atmospheric N deposition were studied in three replicate stands in each ecosystem. We found striking, ecosystem-specific
effects of N deposition on soil organic matter chemistry using pyrolysis gas chromatography/mass spectrometry. First, furfural,
the dominant pyrolysis product of polysaccharides, was significantly decreased by simulated N deposition in the sugar maple–basswood
ecosystem (15.9 vs. 5.0%) but was increased by N deposition in the black oak–white oak ecosystem (8.8 vs. 24.0%). Second,
simulated atmospheric N deposition increased the ratio of total lignin derivatives to total polysaccharides in the >250 μm
fraction of the sugar maple–basswood ecosystem from 0.9 to 3.3 but there were no changes in other size classes or in the black
oak–white oak ecosystem. Third, simulated N deposition increased the ratio of lignin derivatives to N-bearing compounds in
the 63–250 and >250 μm fractions in both ecosystems but not in the <63 μm fraction. Relationships between enzyme kinetics
and organic matter chemistry were strongest in the particulate fractions (>63 μm) where there were multiple correlations between
oxidative enzyme activities and concentrations of lignin derivatives and between glycanolytic enzyme activities and concentrations
of carbohydrates. Within silt-clay fractions (<63 μm), these enzyme-substrate correlations were attenuated by interactions
with particle surfaces. Our results demonstrate that variation in enzyme activity resulting from atmospheric N deposition
is directly linked to changes in soil organic matter chemistry, particularly those that occur within coarse soil size fractions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献