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1.
This study quantifies the uncertainty involved in predicting micropollutant oxidation during drinking water ozonation in a pilot plant reactor. The analysis is conducted for geosmin, methyl tert-butyl ether (MTBE), isopropylmethoxypyrazine (IPMP), bezafibrate, β-cyclocitral and ciprofloxazin. These compounds are representative for a wide range of substances with second order rate constants between 0.1 and 1.9 × 104 M−1 s−1 for the reaction with ozone and between 2 × 109 and 8 × 109 M−1 s−1 for the reaction with OH-radicals. Uncertainty ranges are derived for second order rate constants, hydraulic parameters, flow- and ozone concentration data, and water characteristic parameters. The uncertain model factors are propagated via Monte Carlo simulation and the resulting probability distributions of the relative residual micropollutant concentrations are assessed. The importance of factors in determining model output variance is quantified using Extended Fourier Amplitude Sensitivity Testing (Extended-FAST). For substances that react slowly with ozone (MTBE, IPMP, geosmin) the water characteristic Rct-value (ratio of ozone- to OH-radical concentration) is the most influential factor explaining 80% of the output variance. In the case of bezafibrate the Rct-value and the second order rate constant for the reaction with ozone each contribute about 30% to the output variance. For β-cyclocitral and ciprofloxazin (fast reacting with ozone) the second order rate constant for the reaction with ozone and the hydraulic model structure become the dominating sources of uncertainty.  相似文献   

2.
A combination of experimental methods was applied at a clogged, horizontal subsurface flow (HSSF) municipal wastewater tertiary treatment wetland (TW) in the UK, to quantify the extent of surface and subsurface clogging which had resulted in undesirable surface flow. The three dimensional hydraulic conductivity profile was determined, using a purpose made device which recreates the constant head permeameter test in-situ. The hydrodynamic pathways were investigated by performing dye tracing tests with Rhodamine WT and a novel multi-channel, data-logging, flow through Fluorimeter which allows synchronous measurements to be taken from a matrix of sampling points. Hydraulic conductivity varied in all planes, with the lowest measurement of 0.1 m d−1 corresponding to the surface layer at the inlet, and the maximum measurement of 1550 m d−1 located at a 0.4 m depth at the outlet. According to dye tracing results, the region where the overland flow ceased received five times the average flow, which then vertically short-circuited below the rhizosphere. The tracer break-through curve obtained from the outlet showed that this preferential flow-path accounted for approximately 80% of the flow overall and arrived 8 h before a distinctly separate secondary flow-path. The overall volumetric efficiency of the clogged system was 71% and the hydrology was simulated using a dual-path, dead-zone storage model. It is concluded that uneven inlet distribution, continuous surface loading and high rhizosphere resistance is responsible for the clog formation observed in this system. The average inlet hydraulic conductivity was 2 m d−1, suggesting that current European design guidelines, which predict that the system will reach an equilibrium hydraulic conductivity of 86 m d−1, do not adequately describe the hydrology of mature systems.  相似文献   

3.
The results of a comprehensive testing program conducted to evaluate the hydraulic conductivity (k) of two geosynthetic clay liners (GCLs) considered as a liner component for a tailings impoundment at a proposed zinc and copper mine are reported. The two GCLs were permeated with a relatively low ionic-strength ground water (GW) from the mine site and two electrolyte solutions, a process water (PW) and a simulated leachate (SL), with chemical compositions consistent with those expected during operation of the impoundment. A total of 22 flexible-wall tests were performed to determine the effects of prehydration with the GW, type of GCL, type of permeant liquid, and duration of the back-pressure stage of the test. The k values for both GCLs permeated with the GW were 1.7 × 10−9 cm/s, which is within the range 1–3 × 10−9 cm/s typically reported for GCLs permeated with low ionic-strength liquids, such as deionized water. However, the mean values of k based on permeation of duplicate specimens of both types of GCL with either PW or SL relative to the values of k based on permeation with GW, or k/kw, ranged from a factor of 200 (2.3 orders of magnitude) to a factor of 7600 (3.9 orders of magnitude). Thus, both tailings impoundment solutions had significant adverse impacts on the hydraulic performance of both GCLs. Given the overall range of k/kw values, factors such as prehydration, type of GCL, type of permeant liquid, and duration of back pressure, were relatively insignificant. The results of this study serve to emphasize the need to perform hydraulic conductivity testing using site specific materials.  相似文献   

4.
Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) may cause adverse health effects. However, PCDD/F emissions from burning incense in temples have rarely been addressed. This study investigates PCDD/F emissions from burning incense in a temple. The mean total PCDD/F concentrations were 72.4-82.2 pg Nm− 3 at two indoor sites; their corresponding mean total PCDD/Fs I-TEQ concentrations (0.24-0.27 pg I-TEQ Nm− 3) were ~ 11 times that at a background location. In air samples collected from burning incense, OCDFs accounted for approximately 90% of total PCDD/Fs at the two indoor sites and an outdoor site near the temple, while the major PCDD/Fs in incense ash were PCDDs. The total PCDD/F content and toxic equivalent value of incense ash were 617 pg g− 1 and 1.55 pg I-TEQ g− 1, respectively. At the three sites inside/outside the temple, the air and ash samples contained the same four primary PCDD/Fs-OCDD, 1,2,3,4,6,7,8-HpCDD, OCDF and 1,2,3,4,6,7,8-HpCDF. The Cl emission factor, which is related to the PCDD/F formation, from burning incense was 0.454 mg g− 1. The resultant lifetime average daily dose and cancer risk for temple workers were 0.00964 pg I-TEQ day− 1 kg− 1 and 9.64 × 10− 6, respectively, approximately 2 times that for residents near the temple (0.00489 pg I-TEQ day− 1 kg− 1 and 4.89 × 10− 6, respectively). We suggest that the chlorine content in incense must be regulated, and the high risk of PCDD/F exposure from burning incense for temple workers and visitors should be of concern.  相似文献   

5.
Ca-loaded Pelvetia canaliculata biomass was used to remove Pb2+ in aqueous solution from batch and continuous systems. The physicochemical characterization of algae Pelvetia particles by potentiometric titration and FTIR analysis has shown a gel structure with two major binding groups - carboxylic (2.8 mmol g−1) and hydroxyl (0.8 mmol g−1), with an affinity constant distribution for hydrogen ions well described by a Quasi-Gaussian distribution. Equilibrium adsorption (pH 3 and 5) and desorption (eluents: HNO3 and CaCl2) experiments were performed, showing that the biosorption mechanism was attributed to ion exchange among calcium, lead and hydrogen ions with stoichiometry 1:1 (Ca:Pb) and 1:2 (Ca:H and Pb:H). The uptake capacity of lead ions decreased with pH, suggesting that there is a competition between H+ and Pb2+ for the same binding sites. A mass action law for the ternary mixture was able to predict the equilibrium data, with the selectivity constants αCaH = 9 ± 1 and αCaPb = 44 ± 5, revealing a higher affinity of the biomass towards lead ions. Adsorption (initial solution pH 4.5 and 2.5) and desorption (0.3 M HNO3) kinetics were performed in batch and continuous systems. A mass transfer model using the Nernst-Planck approximation for the ionic flux of each counter-ion was used for the prediction of the ions profiles in batch systems and packed bed columns. The intraparticle effective diffusion constants were determined as 3.73 × 10−7 cm2 s−1 for H+, 7.56 × 10−8 cm2 s−1 for Pb2+ and 6.37 × 10−8 cm2 s−1 for Ca2+.  相似文献   

6.
Kinetic of benzotriazole oxidation by ozone and hydroxyl radical   总被引:3,自引:0,他引:3  
Ozonation experiments were performed in batch reactors in order to determine the rate constants for the reaction of molecular ozone and OH radicals with benzotriazole (BT) at different pHs. The first group of ozonation experiments was carried out for the determination of the rate constant for the direct reactions between ozone and BT. Two different kinetic models were used for the determination of kinetic rate constants: (i) the log-reduction of BT with ozone in excess, (ii) the competition kinetic model. The second-order rate constants for BT with molecular ozone were determined to be 36.4 ± 3.8 M−1 s−1 and 18.4 ± 0.8 M−1 s−1 at pH 2 from the two methods respectively. With the competition method, the value at pH 5 was found to be 22.0 ± 2.0 M−1 s−1. In a following stage, the reaction of BT with OH radicals was investigated at pH values ranging from 2 to 10.2. Using a method involving two probe compounds during the ozonation, the second-order rate constants of the BT reaction with hydroxyl radicals were determined. The rate constants were found to vary from 6.2 × 109 M−1 s−1 at pH 10.2 to 1.7 × 1010 M−1 s−1 at pH 2.  相似文献   

7.
Helminth parasite eggs in low quality water represent health risks when used for irrigation of crops. The settling velocities of helminth eggs (Ascaris suum, Trichuris suis, and Oesophagostomum spp.) and wastewater particles were experimentally determined in tap water and in wastewater using Owen tubes. The settling velocities of eggs in tap water was compared with theoretical settling velocities calculated by Stoke’s law using measurements of size and density of eggs as well as density and viscosity of tap water. The mean settling velocity in tap water of 0.0612 mm s−1 found for A. suum eggs was significantly lower than the corresponding values of 0.1487 mm s−1 for T. suis and 0.1262 mm s−1 for Oesophagostomum spp. eggs. For T. suis and Oesophagostomum spp. eggs the theoretical settling velocities were comparable with the observed velocities in the Owen tubes, while it was three times higher for A. suum eggs. In wastewater, the mean settling velocity for A. suum eggs (0.1582 mm s−1) was found to be different from T. suis (0.0870 mm s−1), Oesophagostomum spp. (0.1051 mm s−1), and wastewater particles (0.0474 mm s−1). This strongly indicates that in low quality water the eggs are incorporated into particle flocs with different settling velocities and that the settling velocity of eggs and particles is closely associated. Our results document that there is a need to differentiate the sedimentation of different types of helminth eggs when assessing the quality of low quality water, e.g. for irrigation usage. The results can also be used to improve existing models for helminth egg removal.  相似文献   

8.
Geosynthetic clay liners (GCLs) are used in landfill liner applications due primarily to their low hydraulic conductivity to water. The low hydraulic conductivity of GCLs comes from the structure of the clay in the bentonite. However, the interaction between clay and aggressive liquids may alter the structure of the clay and, thus, result in an increase in the hydraulic conductivity of the GCL. This paper presents the results of a project aimed at evaluating the impact of a synthetic leachate on the structure of four different bentonites used in the manufacturing of GCLs. The preparation of bentonite dispersions increased the interaction between the bentonites and the various liquids. The hydraulic properties of the dispersions also were tested using filter press tests to obtain flow curves. Results of these tests were correlated with the cationic concentration, electrical conductivity and pH of the dispersions, swell indexes of the bentonite extracted from the GCLs, and permittivities of the intact GCLs determined in oedopermeameter tests. The results showed that one bentonite was more sensitive to the synthetic leachate than the other bentonites. For example, the permittivities of the more sensitive bentonite based on the oedopermeameter tests and filter press tests were respectively 2.11 × 10−8 s−1 and 5.6 × 10−8 s−1, whereas the permittivities for other bentonites, including a natural sodium bentonite and two sodium-activated calcium bentonites, were respectively 5.7 to 6.5 × 10−9 s−1 and 3.2 to 3.5 × 10−8 s−1. The filter press test served as a quick and easy-to-use test to compare the performance of the various bentonites in containing a given liquid. However, the oedopermeameter test or direct permeation test is preferable to filter press tests or fluid loss tests for evaluating the long-term impact of a liquid on a bentonite.  相似文献   

9.
The biological toxicity of CdTe quantum dots (QDs) to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by CdTe QDs was a static quenching process and the binding constant is 6.05 × 103 and the number of binding sites is 0.7938. The thermodynamic parameters (ΔH = − 62.33 kJ mol− 1, ΔG = − 21.21 kJ mol− 1, and ΔS = − 140.3 J mol− 1 s− 1) indicate that hydrogen bonds and van der Waals forces between the protein and the QDs are the main binding forces stabilizing the complex. In addition, UV-vis and CD results showed that the addition of CdTe QDs changed the conformation of BSA.  相似文献   

10.
A novel and straight forward method is adopted to segregate the contribution of primary and secondary sources of formaldehyde based on the rates of its formation and removal at different times in the urban atmosphere of Kolkata. To achieve the above objective, the diurnal and seasonal mixing ratios of formaldehyde were measured during dry season at two busy roadside locations. The maximal secondary formation fluxes of formaldehyde during summer and winter were found to be 6.63 × 107 and 1.23 × 107 molecules cm− 3 s− 1, respectively. Apart from formaldehyde (C1), several other carbonyls were quantified in this study. An overall good correlation between acetaldehyde (C2) and propanal (C3) indicates the contribution of vehicular emission to the carbonyl budget. The secondary formaldehyde contributions in summer and winter were about 71% and 32%, respectively. The relative mean contributions of C1, C2 and ozone towards generation of OH fluxes in summer were found to be 1.56 × 107, 6.96 × 105, and 1.29 × 107 molecules cm− 3 s− 1, respectively, which were 3.2, 3.4 and 1.6 times higher than those in winter.  相似文献   

11.
Release of submicrometer-sized fungal fragments (< 1.0 μm) was discovered in earlier studies, which investigated the aerosolization of spores from moldy surfaces. However, the contribution of fungal fragments to total mold exposure is poorly characterized. The purpose of this study was to investigate the size-fractionated concentrations of particulate (1 → 3)-β-D-glucan and numbers of particles aerosolized from the surface of artificially mold-contaminated materials using a novel sampling methodology. Aspergillus versicolor and Stachybotrys chartarum were grown on malt extract agar and building materials (ceiling tiles and gypsum board) for one to six months. Fungal particles released from these materials were collected size-selectively by a newly developed Fragment Sampling System, and (1 → 3)-β-D-glucan in air samples was analyzed by Limulus Amebocyte lysate (LAL) assay. The concentrations of (1 → 3)-β-D-glucan varied from 0.4 × 100 to 9.8 × 102 ng m− 3 in the fragment size and from 1.0 × 101 to 4.7 × 104 ng m− 3 in the spore size range. Numbers of submicrometer-sized particles aerosolized from 6-month old cultures were always significantly higher that those from 1-month old (P < 0.001). This can be attributed to increased dryness on the surface of material samples and an increase in fungal biomass over time. The average fragment to spore ratios both in particle numbers and (1 → 3)-β-D-glucan mass were higher for S. chartarum than for A. versicolor. The results indicate that long-term mold damage in buildings may lead to increased contribution of fragments to the total mold exposure. Therefore, the health impact of these particles may be even greater than that of spores, considering the strong association between numbers of fine particles and adverse health effects reported in other studies. Furthermore, the contribution of fragments may vary between species and appears to be higher for S. chartarum than for A. versicolor.  相似文献   

12.
Sun Y  Liang L  Zhao X  Yu L  Zhang J  Shi G  Zhou T 《Water research》2009,43(1):41-9305
Aromatic amines such as aniline and its derivatives are an important class of environmental water pollutants. A method based on capillary zone electrophoresis with amperometric detection (CZE-AD) at carbon disk electrode was developed for the determination of aromatic amines in water samples. The effects of working potential, pH and concentration of running buffer, separation voltage and injection time were investigated. Under the optimum conditions, 2,3-diaminonaphthalene, aniline, o-phenylenediamine and p-chloroaniline could be separated in 0.16 mol/L Na2HPO4-citric acid buffer (pH 4.6) within 23 min. The detection limits of them were 1.0 × 10−7, 3.3 × 10−8, 5.0 × 10−8, and 1.3 × 10−7 mol/L (S/N = 3), respectively. The method can be applied directly for the determination of aromatic amines in real water samples with satisfactory results.  相似文献   

13.
Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO2-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH3, CH4, CO2 and N2O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO2-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO2-balance. The AFRs, subject to TGT, were 0.12 m3 s−1 m−2, 1.15 m3 s−1 cow−1, 0.88 m3 s−1 LU−1, 56 h−1, 395 m3 s−1 and 470 kg s−1 through summer seasons, and 0.08 m3 s−1 m−2, 0.83 m3 s−1 cow−1, 0.64 m3 s−1 LU−1 39 h−1, 275 m3 s−1 and 328 kg s−1 through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h−1 cow−1; and through winter seasons were 4.8, 19, 2332 and 2.6 g h−1 cow−1, for NH3, CH4, CO2 and N2O, respectively.  相似文献   

14.
Design parameters for sludge reduction in an aquatic worm reactor   总被引:3,自引:0,他引:3  
Reduction and compaction of biological waste sludge from waste water treatment plants (WWTPs) can be achieved with the aquatic worm Lumbriculus variegatus. In our reactor concept for a worm reactor, the worms are immobilised in a carrier material. The size of a worm reactor will therefore mainly be determined by the sludge consumption rate per unit of surface area. This design parameter was determined in sequencing batch experiments using sludge from a municipal WWTP. Long-term experiments using carrier materials with 300 and 350 μm mesh sizes showed surface specific consumption rates of 45 and 58 g TSS/(m2 d), respectively. Using a 350 μm mesh will therefore result in a 29% smaller reactor compared to using a 300 μm mesh. Large differences in consumption rates were found between different sludge types, although it was not clear what caused these differences. Worm biomass growth and decay rate were determined in sequencing batch experiments. The decay rate of 0.023 d−1 for worms in a carrier material was considerably higher than the decay rate of 0.018 d−1 for free worms. As a result, the net worm biomass growth rate for free worms of 0.026 d−1 was much higher than the 0.009-0.011 d−1 for immobilised worms. Finally, the specific oxygen uptake rate of the worms was determined at 4.9 mg O2/(g ww d), which needs to be supplied to the worms by aeration of the water compartment in the worm reactor.  相似文献   

15.
Dong-Hoon Kim  Sae-Eun Oh 《Water research》2010,44(10):3093-12378
The individual effects of alkaline (pH 8-13) and ultrasonic (3750-45,000 kJ/kg TS) pretreatments on the disintegration of sewage sludge were separately tested, and then the effect of combining these two methods at different intensity levels was investigated using response surface methodology (RSM). In the combined pretreatment, ultrasonic treatment was applied to the alkali-pretreated sludge. While the solubilization (SCOD/TCOD) increase was limited to 50% in individual pretreatments, it reached 70% in combined pretreatment, and the results clearly showed that preconditioning of sludge at high pH levels played a crucial role in enhancing the disintegration efficiency of the subsequent ultrasonic pretreatment. By applying regression analysis, the disintegration degree (DD) was fitted based on the actual value to a second order polynomial equation: Y = −172.44 + 29.82X1 + 5.30 × 10−3X2 − 7.53 × 10−5X1X2 − 1.10X12 − 1.043 × 10−7X22, where X1, X2, and Y are pH, specific energy input (kJ/kg TS), and DD, respectively. In a 2D contour plot describing the tendency of DD with respect to pH and specific energy input, it was clear that DD increased as pH increased, but it seemed that DD decreased when the specific energy input exceeded about 20,000 kJ/kg TS. This phenomenon tells us that there exists a certain point where additional energy input is ineffective in achieving further disintegration. A synergetic disintegration effect was also found in the combined pretreatment, with lower specific energy input in ultrasonic pretreatment yielding higher synergetic effect. Finally, in order to see the combined pretreatment effect in continuous operation, the sludge pretreated with low intensity alkaline (pH 9)/ultrasonic (7500 kJ/kg TS) treatment was fed to a 3 L of anaerobic sequencing batch reactor after 70 days of control operation. CH4 production yield significantly increased from 81.9 ± 4.5 mL CH4/g CODadded to 127.3 ± 5.0 mL CH4/g CODadded by pretreatment, and this enhanced performance was closely related to the solubilization increase of the sludge by pretreatment. However, enhanced anaerobic digestion resulted in 20% higher soluble N concentration in the reactor, which would be an additional burden in the subsequent nitrogen removal system.  相似文献   

16.
N,N′-Diethyl-m-toluamide (DEET) is widely used as an insect repellent and has therefore been detected as a contaminant in numerous waste and surface waters. In this study we have determined the absolute reaction rate constants of DEET with the hydroxyl radical and the hydrated electron in aqueous solution as (4.95 ± 0.18) × 109 and (1.34 ± 0.04) × 109 M−1 s−1, respectively, using pulse radiation. To provide additional information on the radicals formed upon oxidation, transient spectra were measured from 1 to 150 μs, with transient decay rates determined from the time-dependence of the maximum absorption at 330 nm. These data suggest simple decay of the initially formed radical to stable products. Radical-based destruction mechanisms for destruction of DEET are proposed based on the LC-MS determination of the stable compounds produced by 60Co γ-irradiation of DEET solutions. These data will be useful in evaluating potential advanced oxidation/reduction processes for the control of DEET and understanding its fate and transport in surface water where analogous radical chemistry is operative.  相似文献   

17.
The effect of chemical oxygen demand/sulfate (COD/SO42−) ratio on fermentative hydrogen production using enriched mixed microflora has been studied. The chemostat system maintained with a substrate (glucose) concentration of 15 g COD L−1 exhibited stable H2 production at inlet sulfate concentrations of 0-20 g L−1 during 282 days. The tested COD/SO42− ratios ranged from 150 to 0.75 (with control) at pH 5.5 with hydraulic retention time (HRT) of 24, 12 and 6 h. The hydrogen production at HRT 6 h and pH 5.5 was not influenced by decreasing the COD/SO42− ratio from 150 to 15 (with control) followed by noticeable increase at COD/SO42− ratios of 5 and 3, but it was slightly decreased when the COD/SO42− ratio further decreased to 1.5 and 0.75. These results indicate that high sulfate concentrations (up to 20,000 mg L−1) would not interfere with hydrogen production under the investigated experimental conditions. Maximum hydrogen production was 2.95, 4.60 and 9.40 L day−1 with hydrogen yields of 2.0, 1.8 and 1.6 mol H2 mol−1 glucose at HRTs of 24, 12 and 6 h, respectively. The volatile fatty acid (VFA) fraction produced during the reaction was in the order of butyrate > acetate > ethanol > propionate in all experiments. Fluorescence In Situ Hybridization (FISH) analysis indicated the presence of Clostridium spp., Clostridium butyricum, Clostridium perfringens and Ruminococcus flavefaciens as hydrogen producing bacteria (HPB) and absence of sulfate reducing bacteria (SRB) in our study.  相似文献   

18.
Radionuclides released to the atmosphere during dry weather (e.g. after a nuclear accident) may contaminate vegetable foods and cause exposure to humans via the food chain. To obtain experimental data for an appropriate assessment of this exposure path, dry deposition of radionuclides to leafy vegetables was studied under homogeneous and controlled greenhouse conditions. Gaseous 131I-tracer in predominant elemental form and particulate 134Cs-tracer at about 1 μm diameter were used to identify susceptible vegetable species with regard to contamination by these radionuclides. The persistence was examined by washing the harvested product with water. The vegetables tested were spinach (Spinacia oleracea), butterhead lettuce (Lactuca sativa var. capitata), endive (Cichorium endivia), leaf lettuce (Lactuca sativa var. crispa), curly kale (Brassica oleracea convar. acephala) and white cabbage (Brassica oleracea convar. capitata). The variation of radionuclides deposited onto each vegetable was evaluated statistically using the non-parametric Kruskal-Wallis Test and the U-test of Mann-Whitney. Significant differences in deposited 131I and 134Cs activity concentration were found among the vegetable species.For 131I, the deposition velocity to spinach normalized to the biomass of the vegetation was 0.5-0.9 cm3 g− 1 s− 1 which was the highest among all species. The particulate 134Cs deposition velocity of 0.09 cm3 g− 1 s− 1 was the highest for curly kale, which has rough and structured leaves. The lowest deposition velocity was onto white cabbage: 0.02 cm3 g− 1 s− 1 (iodine) and 0.003 cm3 g− 1 s− 1 (caesium). For all species, the gaseous iodine deposition was significantly higher compared to the particulate caesium deposition. The deposition depends on the sensitive parameters leaf area, stomatal aperture, and plant morphology. Decontamination by washing with water was very limited for iodine but up to a factor of two for caesium.  相似文献   

19.
Combined passive treatment technologies have been used to treat acidic rock drainage (ARD), the well-known acute and costly environmental problem facing the mining industry. It is shown that geosynthetic clay liners (GCLs) were able to attenuate metals from lime treated ARD water, and maintain a neutral pH and low hydraulic conductivity (less than 4.0 × 1011 m/s) after 16 pore volumes of permeation; this implies their usefulness as a potentially significant component in combined passive treatment systems. Presented are laboratory breakthrough data for Cu, Cd, Ni, Mn, and Zn from the permeation of GCLs with 16 pore volumes of ARD, treated ARD (TARD), and a landfill leachate. Metal retention occurred in all solutions, but was greatest for the TARD, producing removal efficiencies of greater than 80%.  相似文献   

20.
By using spectroscopic methods, we probed the interaction of Ag+ with bovine serum albumin (BSA) in an aqueous environment. Fluorescence of BSA quenched by Ag+ is a dynamic quenching process. Two binding modes-a strong one at low concentration of Ag+ and a weak one at high concentration were found. The association constant (KA) and the number of binding sites (n) were 4.88 × 103 M− 1 and 1.17 for strong binding, and 17.6 M− 1 and 0.547 for weak binding at 293 K. The results of thermodynamic parameters ΔHθ, ΔGθ and ΔSθ for instinct binding modes at different temperatures indicated that the hydrogen bonding and van der Waals interaction play a major role for low Ag+/BSA ratio while electrostatic association for high Ag+/BSA ratio. Data of UV-Vis and Circular dichroism (CD) suggested that with the increasing amount of Ag+, the secondary structure undergoes a decrease in α-helix and an increase in β content and the backbone of BSA experiences a micro-environmental alteration. Furthermore, the distance r between donor (Trp-212) and acceptor (Ag+) was evaluated to be 10 nm according to nonradiative energy transfer theory.  相似文献   

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