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1.
Pierre Sicard Patrice Coddeville Stéphane Sauvage Jean-Claude Galloo 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):49-58
The long-term monitoring of precipitation and its chemical composition are important for identifying trends in rain quality
and for assessing the effectiveness of pollution control strategies. A statistical test has been used to the atmospheric concentrations
measured in the French rural monitoring network (MERA) in order to bring out spatio-temporal trends in precipitation quality
in France over the period 1990–2003. The non-parametric Mann–Kendall test which has been developed for detecting and estimating
monotonic trends in the time series was used and applied in our study at annual values of wet-only precipitation concentrations.
The emission data suggest that SO2 and NO
x
emissions decreased (−3.3 and −2.0% year−1, respectively) contrary to NH3 emissions that increased slightly (+0.2% year−1) over the period 1990–2002 in France. On the national scale, the pH values have a significant decreasing trend of −0.025 ± 0.02
unit pH year−1. and concentrations in precipitation have a significant decreasing trend, −3.0 ± 1.6 and −3.3 ± 0.6% year−1, respectively, corresponding with the downward trends in SO2 emissions in France (−3.3% year−1). A good correlation (R
2 = 0.84) between SO2 emissions and concentrations was obtained. The decreasing trend of was more significant (−5.4 ± 5.2% year−1) than that of (−1.3 ± 2.4% year−1). Globally, the concentration of the major ions showed a clear downward trend including marine and alkaline ions. In addition,
the relative contribution of HNO3 to acidity precipitation increased by 51% over the studied period. 相似文献
2.
Masaru Watanabe Shuhei Sawamoto Tadafumi Adschiri Kunio Arai 《Journal of Material Cycles and Waste Management》2001,3(2):99-102
This paper gives the results of partial oxidation experiments of polyethylene (PE) in supercritical water (SCW). The experiments
were carried out at a reaction temperature of 693K and a reaction time of 30 min using 6 cm3 of a batch-type reactor. The loaded sample weight was 0.3 g and there was 2.52 g water (0.42 g/cm3). The ratio of oxygen atoms to carbon atoms was 0.3. The results show a significant CO formation in O2–SCW, and the 1-alkene/n-alkane ratio in partial oxidation was higher than that in SCW pyrolysis. These results suggest the possibility of the hydrogenation
of hydrocarbon through partial oxidation followed by a water–gas shift reaction.
Received: July 19, 2000 / Accepted: September 28, 2000 相似文献
3.
Cootes Paradise is a coastal wetland, adjacent to Hamilton Harbour at the western tip of Lake Ontario. The marsh has been
considerably degraded due to the excessive sediment and nutrient input from sewage treatment plants (STPs), marsh tributaries
and Combined Sewer Overflows (CSOs). Although there has been reduction in nutrient loadings from external sources, high nutrient
levels, and a prolific algal growth remain a problem in Cootes Paradise. To assess the importance of external versus internal nutrient loadings to the marsh, nutrient fluxes from sediments were estimated using porewater profiles at three
locations from 2001 and five additional sites from 2002. The fluxes varied between 0.27 and 5.25 mg P m−2 day−1, with sites receiving outfalls of STP and CSO having highest fluxes (∼5 mg P m−2 day−1). Mean phosphorus release rate of 2.02 mg P m−2 day−1 was calculated from the spatial distribution of the non-apatite inorganic phosphorus (NAI-P) in sediments, employing a relationship
between the NAI-P and P fluxes. The results confirm that sediment P geochemistry is important in regulating the P pool in
porewater which, consequently, governs the P fluxes from sediments. 相似文献
4.
Regular additions of NH4NO3 (35–140 kg N ha−1 yr−1) and (NH4)2SO4 (140 kg N ha−1 yr−1) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the
indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure
and composition of this calcareous bryophyte community. The lowest NH4NO3 additions of 35 kg N ha−1 yr−1 produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH4NO3 application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH4NO3 and (NH4)2SO4 additions provided conditions conducive for the establishment of two typical calcifuges – Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH4NO3 deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of
>1 pH unit, between the NH4NO3 and (NH4)2SO4 treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of
35 kg N ha−1 yr−1 or less. These effects are of particular concern for rare or endangered species of low frequency. 相似文献
5.
Daniel W. Pollock Rai S. Kookana Raymond L. Correll 《Water, Air, & Soil Pollution: Focus》2005,5(1-2):67-88
The pesticide impact rating index (PIRI) has been integrated with a Geographic Information System (GIS) to enable regional
assessment of pesticide impact on groundwater and surface water resources. The GIS version of PIRI (PIRI-GIS) was used to
assess the impact of pre-planting atrazine use in the pine plantations on the Gnangara Mound, Western Australia. The impact
on groundwater was found to be spatially variable, mainly dependent on soil type and depth to groundwater, because land use
variables were spatially constant. Areas with the greatest impact on groundwater were those where the soil had a low sorption
capacity for atrazine. Knowledge of the spatial distribution of the sorption coefficient based on organic carbon (K
oc) for atrazine was found to significantly improve the results from PIRI-GIS. Average values for K
oc (i.e. based on overseas data) were too low for most of the local soil types, resulting in a general overestimation of pesticide
impact on groundwater resources, but an underestimation of impact in areas that should be of greatest concern (i.e. where
the soil has a low sorption capacity for atrazine). 相似文献
6.
Effects of Nitrogen Supply on the Sensitivity to O3 of Growth and Photosynthesis of Japanese Beech (Fagus crenata) Seedlings 总被引:1,自引:0,他引:1
Masahiro Yamaguchi Makoto Watanabe Naoki Matsuo Junichi Naba Ryo Funada Motohiro Fukami Hideyuki Matsumura Yoshihisa Kohno Takeshi Izuta 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):131-136
To obtain basic information for evaluating critical levels of O3 under different nitrogen loads for protecting Japanese beech forests, two-year-old seedlings of Fagus crenata Blume were grown in potted andisol supplied with N as NH4NO3 solution at 0, 20 or 50 kg ha−1 year−1 and exposed to charcoal-filtered air or O3 at 1.0, 1.5 and 2.0 times the ambient concentration from 16 April to 22 September 2004. The O3 induced significant reductions in the whole-plant dry mass, net photosynthetic rate at 380 μmol mol−1 CO2 (A
380), carboxylation efficiency (CE) and concentrations of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and total soluble protein (TSP) in the leaves.
The concentrations of Rubisco and TSP were negatively correlated with the concentration of leaf acidic amino acid, suggesting
that O3 enhanced the degradation of protein such as Rubisco. The N supply to the soil did not significantly change the whole-plant
dry mass and A
380, whereas it significantly increased the CE and concentrations of Rubisco and total amino acid. No significant interactive effects of O3 and N supply to the soil were detected on the growth, photosynthetic parameters and concentrations of protein and amino acid
in the leaves. In conclusion, N supply to the soil at ≤50 kg ha−1 year−1 does not significantly change the sensitivity to O3 of growth and net photosynthesis of Fagus crenata seedlings. 相似文献
7.
Hirotoshi Kawabata Bokka Yabunaka Masayuki Tanabe Tateo Usui Katsukiyo Marukawa Shigeta Hara Toshihiro Tanaka 《Journal of Material Cycles and Waste Management》2007,9(1):80-89
A simple, low-cost method for suppression of dioxins/furans (hereinafter referred to as dioxins) is required because many
middle- and, especially, small-scale incinerators have fallen into disuse or have been dismantled because of the high running
and system costs of measures for the suppression of dioxins. Therefore, the purpose of the present study was to develop a
simple removal method for dioxins from combustion gas and to evaluate the basic removal rate of dioxins. The removal method
for suspended matter in a gas mixture (cold model) and dioxins in exhaust gases (hot model) has been investigated by means
of gas injection into water, the mechanism of which is that the suspended matter in the gas gathers at the gas–liquid interface.
In the cold model, the removal ratio of fine particles (RP) by gas injection into water was reproduced well by the following equation: RP (%) = 100 × {1−exp(−0.8 · SS · tC)}, where SS (cm2/cm3) is the specific surface area of bubbles and tC (s) is the residence time of bubbles in water. The removal ratio of fine particles increased as the product Ss · tC increased. In a hot model using the exhaust gas from combustion experiments of polyvinyl chloride, the removal ratio of dioxins
(RD) by injecting the exhaust gas into water was estimated by the following equation: RD (%) = 100 × {1−exp(−0.8 · SS · tC · CD0
0.07)}, where CD0 [ng/cm3 (at standard temperature and pressure)] is the dioxins concentration in the exhaust gas before injection into water. RD depends greatly on the specific surface area of bubbles and the residence time of the bubbles in water, and only weakly on
the dioxins concentration in the exhaust gas. Injection of the exhaust gas into water has been shown to be effective and was
evaluated as a simple method for the removal of dioxins from exhaust gas. 相似文献
8.
J. Y. Kim M.-C. Shin J.-R. Park K. Nam 《Journal of Material Cycles and Waste Management》2003,5(1):0055-0062
The effect of the soil solids concentration in batch tests on the measured values of the partition coefficient (K
p) of organic pollutants in landfill liner-soil material was investigated. Since this study was based on the results of batch
and column tests conducted independently, there were limitations to the conclusions derived. The organic compounds tested
were benzene, methylene chloride, toluene, trichloroethylene, and p-xylene. The results of this study showed that as soil solids concentrations increased, the measured K
p values of these organic compounds strongly decreased. The observed values of K
p stabilized when the soil solids concentration was above a certain value. Typical K
p values obtained from batch tests conducted under high soil solids concentrations were close to those obtained from column
tests. It was concluded that the K
p values of organic compounds measured under low soil solids concentrations, i.e., less than 100 g/l, may not correctly simulate
the field situation. Consequently, the values of K
p obtained with low soil solids concentrations can result in an overestimation of the retardation factor of the landfill liner
material.
Received: March 14, 2002 / Accepted: August 25, 2002 相似文献
9.
Sorption of Sr on bentonite was studied using the batch technique. Distribution coefficients (Kd) were determined as a function of contact time, pH, sorbent and sorbate concentration and temperature. The data were interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich isotherms. Thermodynamic parameters for the sorption system were determined at three different temperatures. The positive value of the heat of sorption, ΔH° = 30.62 kJ/mol at 298 K, shows that the sorption of strontium on bentonite is endothermic. The negative value of the free energy of sorption, ΔG° = −10.69 kJ/mol at 298 K, shows the spontaneity of the reaction. ΔG° becomes more negative with increasing temperature, which shows that the sorption process is more favorable at higher temperatures. The mean free energy for sorption, E 9 kJ/mol, suggests that ion exchange is the predominant mode of sorption in the Sr concentration range studied, i.e. 0.01 – 0.3 mol/dm3. The presence of complementary cations depresses the sorption of strontium on bentonite in the order Ca2+>Mg2+>K+>Na+. Some organic complexing agents and natural ligands also affect the sorption of strontium. The desorption studies with ground water at low strontium loadings on bentonite show that about 90% of Sr is irreversibly sorbed on the bentonite. 相似文献
10.
Water transport in polylactic acid (PLA), PLA/ polycaprolactone copolymers, and PLA/polyethylene glycol blends 总被引:1,自引:0,他引:1
Georgette L. Siparsky Kent J. Voorhees John R. Dorgan Kevin Schilling 《Journal of Polymers and the Environment》1997,5(3):125-136
Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester, and water vapor permeability may have a significant
influence on the rate of degradation. A method is devised to use bags prepared from PLA films and filled with molecular sieves
to determine the water vapor permeability in the polymer, its copolymers with caprolactone, and blends with polyethylene glycol.
The “solution-diffusion” model is used to determine the permeability parameters. These include the solubility coefficient,S, a measure of the equilibrium water concentration available for hydrolysis and the diffusion coefficient,D, which characterizes the rate of water vapor diffusion into the film under specific conditions. Values ofS andD at 50‡C and 90% relative humidity ranged from 400 × 10-6 to 1000 × 10-6 cm3 (STP)/(cm3 Pa) and 0.20 × 10-6 to 1.0 × 10-6 cm2/s, respectively. TheS andD coefficients were also measured at 20 and 40‡C and compared to those of other polymers. The degree of crystallinity was found
to have little influence on the measured permeability parameters. The heat of sorption, δHS, and the activation energy of diffusion, ED, were used to show that the permeability process is best described by the “water cluster” model for hydrophobic polymers.
Finally, the diffusion coefficient is used to compare the rate of water diffusion to the rate of water consumption by ester
hydrolysis. Results indicate that hydrolytic degradation of PLA is reaction-controlled. 相似文献
11.
Airborne particulate matter (PM) concentrations were measured in Iksan, a suburban area in South Korea during April, 2003.
PM2.5 (particles with an aerodynamic diameter less than 2.5 μm) and PM10 (particles with an aerodynamic diameter less than 10 μm) samples were collected, and the chemical characteristics of particles
were examined for diurnal patterns, yellow dust/rainfall influences, and scavenging effects. Average concentrations of PM2.5 and PM10 mass measured were 37.3 ± 16.2 μg m−3 and 60.8 ± 29.5 μg m−3, respectively. The sum of ionic chemical species concentrations for PM2.5 and PM10 was 16.9 ± 7.3 and 23.1 ± 10.1 μg/m3, respectively. A significant reduction in PM mass concentrations during rainfall days was observed for coarse mode (PM2.5 − 10) particles, but less reduction was found for fine (PM2.5) mass concentration. SO4
2−, NH4
+, and K+ predominated in fine particulate mode, NO3
− and Cl− predominated in fine particle mode and coarse particle mode, but Na+, Mg2+, and Ca2+ mostly existed in coarse mode. The high concentration of ammonium due to local emissions and long-range transport neutralized
sulfate and nitrate to ammonium sulfate and ammonium nitrate, which were major forms of airborne PM in Iksan. Average mass
concentrations of PM10 in daytime and at night were 57.6 and 70.0 μg m−3, and those of PM2.5 were 35.4 and 42.5 μg m−3, respectively. NO3
− and Cl− in both PM2.5 and PM10 were about double at night than in the daytime, while the rest of the chemical species were equal or a little higher at night
than in the daytime. The results suggest the formation of ammonium nitrate and chloride when high ammonia concentration and
low air temperature are allowed. Backward air trajectory analyses showed that air masses arriving at the site during yellow
dust period were transported from arid Chinese regions, which resulted in high concentrations of airborne PM mass concentrations.
In the meantime, air mass trajectories during a rainfall period were mostly from the Pacific Ocean or the East China Sea,
along with a relatively low PM concentration. 相似文献
12.
Satoru Fujita Kenzi Suzuki Yasuo Shibasaki Toshiaki Mori 《Journal of Material Cycles and Waste Management》2002,4(1):70-76
Hydrogarnet was synthesized hydrothermally below 200°C using molten slag obtained from municipal solid waste. For comparison,
it was also synthesized using pure-phase CaO–Al2O3–SiO2–H2O, as reported previously. The structural and textural properties of this material were investigated using various analytical
and spectroscopic techniques such as X-ray diffraction, X-ray fluorescence spectrometry, atomic absorption spectrometry (AAS),
thermogravimetry/differential thermal analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy.
The Cl− fixation ability of hydrogarnet was investigated in the temperature range 500–800°C in a fixed-bed flow reactor using a HCl
concentration (1000 p.p.m.v.) similar to that of incinerator exhaust gas. Under these experimental conditions, the hydrogarnet
was capable of reducing the HCl gas level to less than 1 p.p.m.v. Analysis of the spent catalyst revealed that the hydrogarnet
was being transformed into wadalite and CaCl2 at high temperatures. The elution test for chromium ions in hydrogarnet obtained from slag was also used, and it was found
that chromium ions were not eluted from hydrogarnet.
Received: January 27, 2001 / Accepted: October 11, 2001 相似文献
13.
Junya Katagiri Siqingaowa Borjigin Toshiaki Yoshioka Tadaaki Mizoguchi 《Journal of Material Cycles and Waste Management》2010,12(2):136-146
The formation and decomposition of tetrafluoroborate ions (BF4−) in H3BO3-Al3+-F− solutions were investigated via experiments and thermodynamic calculations. The concentration of the formed BF4− increased with decreasing pH, raising the total fluoride concentration and lowering the total aluminum ion concentration.
Once formed, BF4− was stable under neutral and alkaline conditions. Fluoride in the form of BF4− was converted to fluoroaluminate ions by adding an aluminum compound under acidic conditions. A method for removing fluoride
in the form of BF4− is proposed whereby fluoroaluminate ions formed by the reaction of BF4− with aluminum are decomposed with calcium ions. This process was applied to the treatment of wastewater from flue gas desulfurization
plants, and resulted in a satisfying level of reduction in the range of the fluoride emission limit of 8 mg/l. 相似文献
14.
Ulf Sikström 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):137-142
Liming and/or application of specific nutrients have been proposed as countermeasures to the acidification of forest soils
in southern Sweden. In this study the stem growth of Picea abies (L.) Karst. growing on acidic mineral soils in SW Sweden was investigated 10 years after additions of lime (Ca; 3000 kg lime
ha−1), lime plus P (25 kg ha−1) and K (80 kg ha−1), or N in low doses (2 × 10 kg ha−1 yr−1) (treatments: CaPK, Ca, N, CaPKN, and 2Ca2P2K, respectively). Compared with the control, stem growth was increased following
all treatments involving lime additions, including liming alone. The PK addition did not seem to affect growth. The most plausible
cause of the observed growth increases was that the lime additions indirectly increased the supply of plant-available N. The
annual low-dose N addition did not significantly affect growth. This suggests that air-borne deposition of N, which supplies
very small doses of N throughout the year, has a minor or even negligible influence on P. abies growth. 相似文献
15.
V. Y. Hoang H. Jupsin V. C. Le J.-L. Vasel 《Journal of Material Cycles and Waste Management》2012,14(1):3-13
A process of partial nitrification and denitrification in a sequencing batch reactor (SBR) treating leachate was simulated
by applying a modified version of activated sludge model no. 3 (ASM3), named ASM3_2step. This model modifies the ASM3 model
by separating nitrification and denitrification into two steps with nitrite as an intermediate substrate. Three periods, including
long term period, steady state and cycle evolution, were used for calibration. Three main processes were observed, including
biomass production, nitrification (focusing on nitrite accumulation) and denitrification. The kinetic and stoichiometric parameters
(
m\textA_NH \mu_{{{\text{A\_NH}}}} ,
Y\textA_NH Y_{{{\text{A\_NH}}}} ,
Y\textA_\textNO2 Y_{{{\text{A}}\_{\text{NO}}_{2} }} ,
Y\textH_\textO2 Y_{{{\text{H}}\_{\text{O}}_{2} }} , b
A,
K\textA_NH K_{{{\text{A\_NH}}}} ), were determined from biokinetic and respirometry tests. Some of the default values of kinetic and stoichiometric parameters
available in the ASM3 model and in the literature were kept constant, while some others were adjusted step by step until observed
state variables fit with experimental data. The maximum specific growth rate of nitrite oxidizing bacteria (0.108 day−1) (simulated by the model) and that of ammonium oxidizing bacteria (0.61 day−1) (from biokinetic tests) are the parameters which have the highest influence on the nitrite accumulation, even more than
oxygen supply intensity or Kla value. Other important parameters were
K\textAO_NH K_{{{\text{AO\_NH}}}} and
K\textAO_\textNO2 K_{{{\text{AO}}\_{\text{NO}}_{2} }} , calibrated at the values of 1.37 and 1.59 mg O2/L, respectively. The modified model and values of the kinetic and stoichiometric parameters obtained from the modeling process
will be used for optimization of the partial nitrification in the next study. 相似文献
16.
Bohan Liao Zhaohui Guo Qingru Zeng Anne Probst Jean-Luc Probst 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):151-161
Leaching experiments of rebuilt soil columns with two simulated acid rain solutions (pH 4.6–3.8) were conducted for two natural
soils and two artificial contaminated soils from Hunan, south-central China, to study effects of acid rain on competitive
releases of soil Cd, Cu, and Zn. Distilled water was used in comparison. The results showed that the total releases were Zn>Cu>Cd
for the natural soils and Cd>Zn≫Cu for the contaminated soils, which reflected sensitivity of these metals to acid rain. Leached
with different acid rain, about 26–76% of external Cd and 11–68% external Zn were released, but more than 99% of external
Cu was adsorbed by the soils, and therefore Cu had a different sorption and desorption pattern from Cd and Zn. Metal releases
were obviously correlated with releases of TOC in the leachates, which could be described as an exponential equation. Compared
with the natural soils, acid rain not only led to changes in total metal contents, but also in metal fraction distributions
in the contaminated soils. More acidified soils had a lower sorption capacity to metals, mostly related to soil properties
such as pH, organic matter, soil particles, adsorbed SO4
2−, exchangeable Al3+ and H+, and contents of Fe2O3 and Al2O3. 相似文献
17.
Ping-Ping Shen Hong Zhou Ho-Yan Lai Ji-Dong Gu 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):575-581
Benthic infaunal communities at Mai Po Inner Deep Bay mudflat, Hong Kong were investigated between August 2002 and August
2003. A total of 55 species belonging to 8 Phyla from more than 99,074 specimens were recorded. The species richness varied
between 13 at Station B in August 2002 and 28 at Station D in August 2003 with an average of 21 across the mudflat and the
species diversity was low [H′(log2) = 0.7–3.5 with an average H′ = 2.4]. Seasonal variations were also observed through abundance and biomass across the mudflat among the seasons. The abundance
density was between 8,977 individuals m−2 at Station D in February 2003 and 77,256 individuals m−2 at Station B in November 2002 and the overall average density was 25,274 individuals m−2 for the four stations. The benthic infauna were dominated by pollution tolerant species at this wetland mudflat. 相似文献
18.
Johan Bergholm Hooshang Majdi Tryggve Persson 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):225-234
A nitrogen (N) budget was constructed for a period of 6 years (1988–1993) in a Norway spruce stand with current deposition
of 19 kg N and 22 kg S ha−1 year−1. The stand was fertilized annually by addition of 100 kg N and 114 kg S ha−1 (NS). Above and below ground biomass, litterfall, fine- root litter production, soil solution and net mineralization were
measured to estimate pools, fluxes and accumulation of nitrogen. The average needle litterfall in control (C) and NS plots
in 1993 was 2.2 and 2.5 ton ha−1 year−1, respectively. The fine root litter production prior to treatment (1987) was 4.4 ton ha−1 year−1 and after treatment (1993) it was 4.5 and 3.9 ton ha−1 year−1 in C and NS plots, respectively. Net N mineralization in the soil profile down to 50 cm was estimated to be 86 and 115 kg
ha−1 year−1 in C and NS plots, respectively in 1992. During the treatment period the uptake of N in the needle biomass in C and NS plots
was 29 and 77 kg ha−1 year−1, respectively. No N was accumulated in needles of C plot where the NS plots accumulated 34 kg ha−1 year−1. Of the annually added inorganic N to NS plots 47% was accumulated in the above and below ground biomass and 37% in the soil.
N fluxes via fine-root litter production in the C plots were much higher (54 kg ha−1 year−1) than that via litterfall (29 kg ha−1 year−1). The corresponding values in the NS plots were 65 and 43 kg ha−1 year−1, respectively. Most of the net N mineralization occurred in the FH layer and upper mineral soil. It is concluded that fine
root litter and litterfall play an important role in the cycling of N. Despite a high N uptake the losses of N in litterfall
and fine root litter resulted in an incorporation of N in soil organic matter. 相似文献
19.
Studies on the moisture sorption characteristics of chitosan/polyethylene oxide (PEO) blended films have been carried out
at 27 °C for water activity (a
w) from 0.1 to 0.9. The sorption data at different a
w were used to fit 12 different sorption isotherm models proposed in the literature. The model constants were determined by
linear fitting of the sorption equations. The ranges of applicability of water activity for the isotherms reported in the
article lie between 0.11 to 0.44 (monomolecular layer) for the BET model and between 0.11 to 0.86 (monolayer & multilayer’s)
for Smith, Caurie, Bradley and Oswin. The water activity for Halsey and Chung & Pfost models lies between 0.44 to 0.86 (multilayer)
and 0.33 to 0.86 for Henderson and Freundlich models and 0.11 to 0.65 for Kuhn, Linear and Iglesias & Chirife models. The
high coefficient of determination R
2 (ranges from 0.82 to 1) confirms the applicability of the equations employed. The study on the application of such water
activity data of chitosan/PEO blended films on different model equations will be helpful in prediction of durability and functional
behavior of moisture sensitive biopolymeric films 相似文献
20.
Atmospherically deposited lead in the upper layer of the heavily eroded peatlands of the Peak District, southern Pennines,
UK, reaches concentrations in excess of 1,000 mg kg−1. Erosion of the upper peat layer in this region is releasing lead, associated with eroded peat particles, into the fluvial
system. Understanding the process mechanisms that control dissolved lead concentrations in contaminated peatland streams is
vital for understanding lead cycling and transport in peatland streams. Many headwater streams of the southern Pennines recharge
drinking water reservoirs. Measurements in the Upper North Grain (UNG) study catchment show that mean sediment-associated
and dissolved lead concentrations are 102 ± 39.4 mg kg−1 and 5.73 ± 2.16 μg l−1, respectively. Experimental evidence demonstrates that lead can desorb from suspended sediments, composed of contaminated
peat, into stream waters. In-stream processing could therefore account for the elevated dissolved lead concentrations in the
fluvial system of UNG. 相似文献