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1.
Since primary environmental concept for long storage of nuclear waste involved assessment of water in uranium complexes depending on migration processes, the paper emphasized solid-state matrix-assisted laser desorption/ionization (MALDI) mass spectrometric (MS) and IR spectroscopic determination of UO 2(NO 3) 2·6H 2O; UO 2(NO 3) 2·3H 2O, α-, β-, and γ-UO 3 modifications; UO 3· xH 2O ( x?=?1 or 2); UO 3·H 2O, described chemically as UO 2(OH) 2, β- and γ-UO 2(OH) 2 modifications; and UO 4·2H 2O, respectively. Advantages and limitation of vibrational spectroscopic approach are discussed, comparing optical spectroscopic data and crystallographic ones. Structural similarities occurred in α–γ modifications of UO 3, and UO 2(OH) 2 compositions are analyzed. Selective speciation achieved by solid-state mass spectrometry is discussed both in terms of its analytical contribution for environmental quality assurance and assessment of radionuclides, and fundamental methodological interest related the mechanistic complex water exchange of UO 3·H 2O forms in the gas phase. In addition to high selectivity and precision, UV-MALDI-MS, employing an Orbitrap analyzer, was a method that provided fast steps that limited sample pretreatment techniques for direct analysis including imaging. Therefore, random and systematic errors altering metrology and originating from the sample pretreatment stages in the widely implemented analytical protocols for environmental sampling determination of actinides are significantly reduced involving the UV-MALDI-Orbitrap-MS method. The method of quantum chemistry is utilized as well to predict reliably the thermodynamics and nature of U–O bonds in uranium species in gas and condensed phases. 相似文献
2.
The effects of elevated CO 2 on metal species and mobility in the rhizosphere of hyperaccumulator are not well understood. We report an experiment designed to compare the effects of elevated CO 2 on Cd/Zn speciation and mobility in the rhizosphere of hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii grown under ambient (350 μl l ?1) or elevated (800 μl l ?1) CO 2 conditions. No difference in solution pH of NHE was observed between ambient and elevated CO 2 treatments. For HE, however, elevated CO 2 reduced soil solution pH by 0.22 unit, as compared to ambient CO 2 conditions. Elevated CO 2 increased dissolved organic carbon (DOC) and organic acid levels in soil solution of both ecotypes, but the increase in HE solution was much greater than in NHE solution. After the growth of HE, the concentrations of Cd and Zn in soil solution decreased significantly regardless of CO 2 level. The visual MINTEQ speciation model predicted that Cd/Zn–DOM complexes were the dominant species in soil solutions, followed by free Cd 2+ and Zn 2+ species for both ecotypes. However, Cd/Zn–DOM complexes fraction in soil solution of HE was increased by the elevated CO 2 treatment (by 8.01 % for Cd and 8.47 % for Zn, respectively). Resin equilibration experiment results indicated that DOM derived from the rhizosphere of HE under elevated CO 2 (HE-DOM-E) (90 % for Cd and 73 % for Zn, respectively) showed greater ability to form complexes with Cd and Zn than those under ambient CO 2 (HE-DOM-A) (82 % for Cd and 61 % for Zn, respectively) in the undiluted sample. HE-DOM-E showed greater ability to extract Cd and Zn from soil than HE-DOM-A. It was concluded that elevated CO 2 could increase the mobility of Cd and Zn due to the enhanced formation of DOM–metal complexes in the rhizosphere of HE S. alfredii. 相似文献
3.
Purpose The interaction between triclosan (TCS) and human serum albumin (HSA) was investigated in order to obtain the binding mechanism, binding constant, the type of binding force, the binding distance between the donor and acceptor, and the effect of TCS on the conformation change of HSA. Methods A HSA solution was added to the quartz cell and then titrated by successive addition of TCS. The fluorescence quenching spectra and synchronous spectra were recorded with the excitation and emission slits of the passage of band set at 10 and 20 nm. Three-dimensional fluorescence spectra of HSA were recorded before and after the addition of TCS. The capillary electrophoresis was conducted with the pressure injection mode at 0.5 psi for 5 s, separation under 25 kV, and detection at 214 nm. Results Fluorescence data indicated the fluorescence quenching of HSA by TCS was static quenching, and the quenching constants ( K a ) were 1.14?×?10 5, 8.75?×?10 4, 6.67?×?10 4, and 5.00?×?10 4 at 293, 298, 303, and 309 K, respectively. The thermodynamic parameters, enthalpy change ( ??H) and entropy change ( ??S) for the interaction were calculated to be ?37.9 kJ mol ?1 and 32.6 J?mol ?1 K ?1. The binding distance between TCS and tryptophan residues of HSA was obtained to be 1.81 nm according to F??rster nonradioactive energy transfer theory. The UV-Vis absorption spectroscopy, the synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, and circular dichroism spectroscopy revealed the alterations of HSA secondary structure in the presence of TCS. Finally, the interaction between TCS and HSA was further confirmed by capillary electrophoresis. Conclusions TCS was bound to HSA to form the TCS-HSA complex, with the binding distance of 1.81 nm. Hydrophobic interaction and hydrogen bond were dominated in the binding. TCS could change the secondary conformation of HSA. This work provides an insight into noncovalent interaction between emerging pollutants and protein, helping to elucidate the toxic mechanism of such pollutants. 相似文献
4.
Recent studies have shown up to 6 % of rivers in England and Wales to be impacted by discharges from abandoned metal mines. Despite the large extent of impacts, there are still many areas where mine water impact assessments are limited by data availability. This study provides an overview of water quality, trace element composition and flux arising from one such area; the Yorkshire Pennine Orefield in the UK. Mine drainage waters across the orefield are characterised by Ca–HCO 3–SO 4-type waters, with moderate mineralization (specific electrical conductance: 160–525 μS cm ?1) and enrichment of dissolved Zn (≤2003 μg?L ?1), Ba (≤971 μg?L ?1), Pb (≤183 μg?L ?1) and Cd (≤12 μg?L ?1). The major ion composition of the waters reflects the Carboniferous gritstone and limestone-dominated country rock, the latter of which is heavily karstified in parts of the orefield, while sulphate and trace element enrichment is a product of the oxidation of galena, sphalerite and barite mineralization. Contaminant flux measurements at discharge sites highlight the disproportionate importance of large drainage levels across the region, which generally discharge into first-order headwater streams. Synoptic metal loading surveys undertaken in the Hebden Beck sub-catchment of the river Wharfe highlight the importance of major drainage levels to instream baseflow contamination, with diffuse sources from identifiable expanses of waste rock becoming increasingly prominent as river flows increase. 相似文献
5.
Acrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon. These compounds are widely used in the production of plastics and resins. Atmospheric degradation processes of these compounds are currently not well understood. The kinetics of the gas phase reactions of OH radicals with methyl 3-methylacrylate and methyl 3,3-dimethylacrylate were determined using the relative rate technique in a 50 L Pyrex photoreactor using in situ FTIR spectroscopy at room temperature (298?±?2 K) and atmospheric pressure (708?±?8 Torr) with air as the bath gas. Rate coefficients obtained were (in units cm 3 molecule ?1 s ?1): (3.27?±?0.33)?×?10 ?11 and (4.43?±?0.42)?×?10 ?11, for CH 3CH═CHC(O)OCH 3 and (CH 3) 2CH═CHC(O)OCH 3, respectively. The same technique was used to study the gas phase reactions of hexyl acrylate and ethyl hexyl acrylate with OH radicals and Cl atoms. In the experiments with Cl, N 2 and air were used as the bath gases. The following rate coefficients were obtained (in cm 3 molecule ?1 s ?1): k 3 (CH 2═CHC(O)O(CH 2) 5CH 3?+?Cl)?=?(3.31?±?0.31)?×?10 ?10, k 4(CH 2═CHC(O)OCH 2CH(CH 2CH 3)(CH 2) 3CH 3?+?Cl)?=?(3.46?±?0.31)?×?10 ?10, k 5(CH 2═CHC(O)O(CH 2) 5CH 3?+?OH)?=?(2.28?±?0.23)?×?10 ?11, and k 6(CH 2═CHC(O)OCH 2CH(CH 2CH 3)(CH 2) 3CH 3?+?OH)?=?(2.74?±?0.26)?×?10 ?11. The reactivity increased with the number of methyl substituents on the double bond and with the chain length of the alkyl group in –C(O)OR. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for these compounds is their daytime reaction with the hydroxyl radical. In coastal areas and in some polluted environments, Cl atom-initiated degradation of these compounds can be significant, if not dominant. Maximum Incremental Reactivity (MIR) index and global warming potential (GWP) were also calculated, and it was concluded that these compounds have significant MIR values, but they do not influence global warming. 相似文献
6.
Upon completion of exploration and extraction of mineral resources, many mining sites have been abandoned without previously putting environmental protection measures in place. As a consequence, mine waters originating from such sites are discharged freely into surface water. Regional scale analyses were conducted to determine the hydrochemical characteristics of mine waters from abandoned sites featuring metal (Cu, Pb–Zn, Au, Fe, Sb, Mo, Bi, Hg) deposits, non-metallic minerals (coal, Mg, F, B) and uranium. The study included 80 mine water samples from 59 abandoned mining sites. Their cation composition was dominated by Ca 2+, while the most common anions were found to be SO 4 2? and HCO 3 ?. Strong correlations were established between the pH level and metal (Fe, Mn, Zn, Cu) concentrations in the mine waters. Hierarchical cluster analysis was applied to parameters generally indicative of pollution, such as pH, TDS, SO 4 2?, Fe total, and As total. Following this approach, mine water samples were grouped into three main clusters and six subclusters, depending on their potential environmental impact. Principal component analysis was used to group together variables that share the same variance. The extracted principal components indicated that sulfide oxidation and weathering of silicate and carbonate rocks were the primary processes, while pH buffering, adsorption and ion exchange were secondary drivers of the chemical composition of the analyzed mine waters. Surface waters, which received the mine waters, were examined. Analysis showed increases of sulfate and metal concentrations and general degradation of surface water quality. 相似文献
7.
The mass concentration of carbonaceous species, organic carbon (OC), and elemental carbon (EC) using a semicontinuous thermo-optical EC-OC analyzer, and black carbon (BC) using an Aethalometer were measured simultaneously at an urban mega city Delhi in Ganga basin from January 2011 to May 2012. The concentrations of OC, EC, and BC exhibit seasonal variability, and their concentrations were ~2 times higher during winter (OC 38.1?±?17.9 μg m ?3, EC 15.8?±?7.3 μg m ?3, and BC 10.1?±?5.3 μg m ?3) compared to those in summer (OC 14.1?±?4.3 μg m ?3, EC 7.5?±?1.5 μg m ?3, and BC 4.9?±?1.5 μg m ?3). A significant correlation between OC and EC ( R?=?0.95, n?=?232) indicate their common emission sources with relatively lower OC/EC ratio (range 1.0–3.6, mean 2.2?±?0.5) suggests fossil fuel emission as a major source of carbonaceous aerosols over the station. On average, mass concentration of EC was found to be ~38 % higher than BC during the study period. The measured absorption coefficient (b abs) was significantly correlated with EC, suggesting EC as a major absorbing species in ambient aerosols at Delhi. Furthermore, the estimated mass absorption efficiency (σ abs) values are similar during winter (5.0?±?1.5 m 2 g ?1) and summer (4.8?±?2.8 m 2 g ?1). Significantly high aerosol loading of carbonaceous species emphasize an urgent need to focus on air quality management and proper impact assessment on health perspective in these regions. 相似文献
8.
In this paper, stable carbon isotope ratios ( δ 13C) were determined in the atmosphere by using a Ca-based sorbent, CaO/Ca 12Al 14O 33 75:25 w/w, for passively collecting atmospheric CO 2, in both field and laboratory experiments. Field measurements were conducted in three environments characterized by different carbon dioxide sources. In particular, the environments under consideration were a rather heavily trafficked road, where the source of CO 2 is mostly vehicle exhaust, a rural unpolluted area, and a private kitchen where the major source of CO 2 was gas combustion. Samplers were exposed to the free atmosphere for 3 days in order to allow collection of sufficient CO 2 for δ 13C analysis, then the collected CO 2 was desorbed from the adsorbent with acid treatment, and directly analyzed by nondispersive infrared (NDIR) instrument. δ 13C results confirmed that the samplers collected representative CO 2 samples and no fractionation occurred during passive trapping, as also confirmed by an appositely designed experiment conducted in the laboratory. Passive sampling using CaO/Ca 12Al 14O 33 75:25 w/w proved to be an easy and reliable method to collect atmospheric carbon dioxide for δ 13C analysis in both indoor and outdoor places. 相似文献
9.
A novel dual coagulant system of polyaluminum chloride sulfate (PACS) and polydiallyldimethylammonium chloride (PDADMAC) was used to treat natural algae-laden water from Meiliang Gulf, Lake Taihu. PACS (Al n(OH) mCl 3n-m-2k(SO 4) k) has a mass ratio of 10 %, a SO 4 2?/Al 3 + mole ratio of 0.0664, and an OH/Al mole ratio of 2. The PDADMAC ([C 8H 16NCl] m) has a MW which ranges from 5?×?10 5 to 20?×?10 5 Da. The variations of contaminants in water samples during treatments were estimated in the form of principal component analysis (PCA) factor scores and conventional variables (turbidity, DOC, etc.). Parallel factor analysis determined four chromophoric dissolved organic matters (CDOM) components, and PCA identified four integrated principle factors. PCA factor 1 had significant correlations with chlorophyll-a ( r?=?0.718), protein-like CDOM C1 (0.689), and C2 (0.756). Factor 2 correlated with UV 254 (0.672), humic-like CDOM component C3 (0.716), and C4 (0.758). Factors 3 and 4 had correlations with NH 3-N (0.748) and T-P (0.769), respectively. The variations of PCA factors scores revealed that PACS contributed less aluminum dissolution than PAC to obtain equivalent removal efficiency of contaminants. This might be due to the high cationic charge and pre-hydrolyzation of PACS. Compared with PACS coagulation (20 mg L ?1), the removal of PCA factors 1, 2, and 4 increased 45, 33, and 12 %, respectively, in combined PACS–PDADMAC treatment (0.8 mg L ?1?+?20 mg L ?1). Since PAC contained more Al (0.053 g/1 g) than PACS (0.028 g/1 g), the results indicated that PACS contributed less Al dissolution into the water to obtain equivalent removal efficiency. 相似文献
10.
The ubiquitous β-Proteobacterium Gallionella ferruginea is known as stalk-forming, microaerophilic iron(II) oxidizer, which rapidly produces iron oxyhydroxide precipitates. Uranium and neptunium sorption on the resulting intermixes of G. ferruginea cells, stalks, extracellular exudates, and precipitated iron oxyhydroxides (BIOS) was compared to sorption to abiotically formed iron oxides and oxyhydroxides. The results show a high sorption capacity of BIOS towards radionuclides at circumneutral pH values with an apparent bulk distribution coefficient (Kd) of 1.23 × 104 L kg?1 for uranium and 3.07 × 105 L kg?1 for neptunium. The spectroscopic approach by X-ray absorption spectroscopy (XAS) and ATR FT-IR spectroscopy, which was applied on BIOS samples, showed the formation of inner-sphere complexes. The structural data obtained at the uranium LIII-edge and the neptunium LIII-edge indicate the formation of bidentate edge-sharing surface complexes, which are known as the main sorption species on abiotic ferrihydrite. Since the rate of iron precipitation in G. ferruginea-dominated systems is 60 times faster than in abiotic systems, more ferrihydrite will be available for immobilization processes of heavy metals and radionuclides in contaminated environments and even in the far-field of high-level nuclear waste repositories. 相似文献
11.
Weathering of sulphide minerals produces a great variety of efflorescences of soluble sulphate salts. These minerals play an important role for environmental pollution, since they can be either a sink or a source for acidity and trace elements. This paper aims to characterise surface waters affected by mining activities in the Sierra Minera of Cartagena-La Union (SE, Spain). Water samples were analysed for trace metals (Zn, Cd, Pb, Cu, As and Fe), major ions (Na +, K +, Ca 2+ and Mg 2+) and anions (F ?, Cl ?, NO 3 ?, CO 3 2?, SO 4 2?) concentrations and were submitted to an “evaporation-precipitation” experiment that consisted in identifying the salts resulting from the evaporation of the water aliquots sampled onsite. Mineralogy of the salts was studied using X-ray diffraction and compared with the results of calculations using VISUAL MINTEQ. The study area is heavily polluted as a result of historical mining and processing activities that has produced large amount of wastes characterised by a high trace elements content, acidic pH and containing minerals resulting from the supergene alteration of the raw materials. The mineralogical study of the efflorescences obtained from waters shows that magnesium, zinc, iron and aluminium sulphates predominate in the acid mine drainage precipitates. Minerals of the hexahydrite group have been quantified together with minerals of the rozenite group, alunogen and other phases such as coquimbite and copiapite. Calcium sulphates correspond exclusively to gypsum. In a semiarid climate, such as that of the study area, these minerals contribute to understand the response of the system to episodic rainfall events. MINTEQ model could be used for the analysis of waters affected by mining activities but simulation of evaporation gives more realistic results considering that MINTEQ does not consider soluble hydrated salts. 相似文献
12.
This study investigates the water-soluble ionic constituents (Na +, K +, NH 4 +, Ca 2+, Mg 2+, Cl ?, NO 3 ?, SO 4 2?) associated to PM 2.5 particle fraction at two urban sites in the city of Thessaloniki, northern Greece, an urban traffic site (UT) and urban background site (UB). Ionic constituents represent a significant fraction of PM 2.5 mass (29.6 at UT and 41.5 % at UB). The contribution of marine aerosol was low (<1.5 %). Secondary inorganic aerosols (SIA) represent a significant fraction of PM 2.5 mass contributing to 26.9?±?12.4 % and 39.2?±?13.2 % at UT and UB sites, respectively. Nitrate and sulfate are fully neutralized by ammonium under the existing conditions. The ionic constituents were evaluated in relation to their spatial and temporal variation, their gaseous precursors, meteorological conditions, local and long-range transport. 相似文献
13.
AbstractMonensin (MON) is a coccidiostat used as a growth promoter that can reach the environment through fertilization with manure from farm animals. To verify whether field-relevant concentrations of this drug negatively influence the structure and activity of tropical soil bacteria, plate counts, CO 2 efflux measurements, phospholipid fatty acids (PLFA) and community-level physiological profiling (CLPP) profiles were obtained for soil microcosms exposed to 1 or 10?mg kg ?1 of MON across 11?days. Although 53% (1?mg kg ?1) to 40% (10?mg kg ?1) of the MON concentrations added to the microcosms dissipated within 5?days, a subtle concentration-dependent decrease in the number of culturable bacteria (<1 log CFU g ?1), reduced (?20 to ?30%) or exacerbated (+25%) soil CO 2 effluxes, a marked shift of non-bacterial fatty acids, and altered respiration of amines (1.22-fold decrease) and polymers (1.70-fold increase) were noted in some of the treatments. These results suggest that MON quickly killed some microorganisms and that the surviving populations were selected and metabolically stimulated. Consequently, MON should be monitored in agronomic and environmental systems as part of One Health efforts. 相似文献
14.
Total suspended particulate (TSP) samples were collected during dust, haze, and two festival events (Holi and Diwali) from February 2009 to June 2010. Pollutant gases (NO 2, SO 2, and O 3) along with the meteorological parameters were also measured during the four pollution events at Agra. The concentration of pollutant gases decreases during dust events (DEs), but the levels of the gases increase during other pollution events indicating the impact of anthropogenic emissions. The mass concentrations were about two times higher during pollution events than normal days (NDs). High TSP concentrations during Holi and Diwali events may be attributed to anthropogenic activities while increased combustion sources in addition to stagnant meteorological conditions contributed to high TSP mass during haze events. On the other hand, long-range transport of atmospheric particles plays a major role during DEs. In the dust samples, Ca 2+, Cl ?, NO 3 ?, and SO 4 2? were the most abundant ions and Ca 2+ alone accounted for 22 % of the total ionic mass, while during haze event, the concentrations of secondary aerosols species, viz., NO 3 ?, SO 4 2?, and NH 4 +, were 3.6, 3.3, and 5.1 times higher than the normal days. During Diwali, SO 4 2? concentration (17.8 μg?m ?3) was highest followed by NO 3 ?, K +, and Cl ? while the Holi samples were strongly enriched with Cl ? and K + which together made up 32.7 % of the total water-soluble ions. The ion balances indicate that the haze samples were acidic. On the other hand, Holi, Diwali, and DE samples were enriched with cations. The carbonaceous aerosol shows strong variation with the highest concentration during Holi followed by haze, Diwali, DEs, and NDs. However, the secondary organic carbon concentration follows the order haze > DEs > Diwali > Holi > NDs. The scanning electron microscope/EDX results indicate that KCl and carbon-rich particles were more dominant during Holi and haze events while DE samples were enriched with particles of crustal origin. 相似文献
15.
Carbonic anhydrase II (CA II) can catalyze the reversible hydration reaction of CO 2 at a maximum of 1.4?×?10 6 molecules of CO 2 per second. The crude intracellular enzyme extract containing CA II was derived from Chlorella vulgaris. A successful CO 2 capture experiment with the presence of calcium had been conducted on the premise that the temperature was conditioned at a scope of 30?C40?°C, that the biocatalyst-nurtured algal growth period lasted 3?days, and that pH ranged from7.5 to 8.5. Ions of K +, Na +, Ca 2+, Co 2+, Cu 2+, Fe 3+, Mg 2+, Mn 2+, and Zn 2+ at 0.01, 0.1, and 0.5?M were found to exhibit no more than 30?% inhibition on the residual activity of the biocatalyst. It is reasonable to expect that calcification catalyzed by microalgae presents an alternative to geological carbon capture and sequestration through a chain of fundamental researches carried on under the guidance of sequestration technology. 相似文献
16.
Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO 2) was performed under different conditions. Suspensions of the TiO 2 were used to compare the degradation efficiency of BPA (20 mg L ?1) in batch and compound parabolic collector (CPC) reactors. A TiO 2 catalyst supported on glass spheres was prepared (sol–gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L ?1). The influence of OH·, O 2 ·?, and h + on the BPA degradation were evaluated. The radicals OH· and O 2 ·? were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO 2 to degrade BPA in batch or CPC reactors was 0.1 g L ?1. According to biological tests, the BPA LC 50 in 24 h for E. andrei was of 1.7?×?10 ?2 mg cm ?2. The photocatalytic degradation of BPA mediated by TiO 2 supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment. 相似文献
17.
The influences of HCO 3 ?, Cl ?, and other components on the UV/TiO 2 degradation of the antineoplastic agents ifosfamide (IFO) and cyclophosphamide (CP) were studied in this work. The results indicated that the presence of HCO 3 ?, Cl ?, NO 3 ?, and SO 4 2? in water bodies resulted in lower degradation efficiencies. The half-lives of IFO and CP were 1.2 and 1.1 min and increased 2.3–7.3 and 3.2–6.3 times, respectively, in the presence of the four anions (initial compound concentration = 100 μg/L, TiO 2 loading =100 mg/L, anion concentration = 1000 mg/L, and pH = 8). Although the presence of HCO 3 ? in the UV/TiO 2/HCO 3 ? system resulted in a lower degradation rate and less byproduct formation for IFO and CP, two newly identified byproducts, P11 (M.W. = 197) and P12 (M.W. = 101), were formed and detected, suggesting that additional pathways occurred during the reaction of ?CO 3 ? in the system. The results also showed that ?CO 3 ? likely induces a preferred ketonization pathway. Besides the inorganic anions HCO 3 ?, Cl ?, NO 3 ?, and SO 4 2?, the existence of dissolved organic matter in the water has a significant effect and inhibits CP degradation. Toxicity tests showed that higher toxicity occurred in the presence of HCO 3 ? or Cl ? during UV/TiO 2 treatment and within 6 h of reaction time, implying that the effects of these two anions should not be ignored when photocatalytic treatment is applied to treat real wastewater. 相似文献
18.
The utilization of sustainable and biodegradable lignocellulosic fiber to detoxify the noxious Cr(VI) from wastewater is considered a versatile approach to clean up a contaminated aquatic environment. The aim of the present research is to assess the proficiency and mechanism of biosorption on Ficus carica bast fiber via isotherm models (Langmuir, Freundlich, Temkin, Harkin’s–Jura, and Dubinin–Radushkevich), kinetic models, and thermodynamic parameters. The biomass extracted from fig plant was characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. To optimize the maximum removal efficiency, different parameters like effect of initial concentration, effect of temperature, pH, and contact time were studied by batch method. The equilibrium data were best represented by the Langmuir isotherm model, and the maximum adsorption capacity of Cr(VI) onto biosorbent was found to be 19.68 mg/g. The pseudo-second-order kinetic model adequately described the kinetic data. The calculated values of thermodynamic parameters such as enthalpy change (? H 0), entropy change (? S 0), and free energy change (? G 0) were 21.55 kJ/mol, 76.24 J/mol?K, and ?1.55 kJ/mol, respectively, at 30 °C which accounted for spontaneous and endothermic processes. The study of adsorbent capacity for Cr(VI) removal in the presence of Na +, Mg 2+, Ca 2+, SO 4 2? , HCO 3 ? and Cl ? illustrated that the removal of Cr(VI) increased in the presence of HCO 3? ions; the presence of Na +, SO 4 2? or Cl ? showed no significant influence on Cr(VI) adsorption, while Ca 2+ and Mg 2+ ions led to an insignificant decrease in Cr(VI) adsorption. Further, the desorption studies illustrated that 31.10 % of metal ions can be removed from an aqueous system, out of which 26.63 % of metal ions can be recovered by desorption in first cycle and the adsorbent can be reused. The results of the scale-up study show that the ecofriendly detoxification of Cr(VI) from aqueous systems was technologically feasible. 相似文献
19.
This article reports a dataset on 8 years of monitoring carbon fluxes in a subarctic palsa mire based on micrometeorological eddy covariance measurements. The mire is a complex with wet minerotrophic areas and elevated dry palsa as well as intermediate sub-ecosystems. The measurements document primarily the emission originating from the wet parts of the mire dominated by a rather homogenous cover of Eriophorum angustifolium. The CO 2/CH 4 flux measurements performed during the years 2001–2008 showed that the areas represented in the measurements were a relatively stable sink of carbon with an average annual rate of uptake amounting to on average ?46 g C m ?2 y ?1 including an equally stable loss through CH 4 emissions (18–22 g CH 4–C m ?2 y ?1). This consistent carbon sink combined with substantial CH 4 emissions is most likely what is to be expected as the permafrost under palsa mires degrades in response to climate warming. 相似文献
20.
Considerable researches have documented the negative effects of ozone on woody species in North America and Europe; however, little is known about how woody tree species respond to elevated O 3 in subtropical China, and most of the previous studies were conducted using pot experiment. In the present study, Machilus ichangensis Rehd. et Wils ( M. ichangensis) and Taxus chinensis (Pilger) Rehd. ( T. chinensis), evergreen tree species in subtropical China, were exposed to non-filtered air (NF), 100 nmol mol ?1 O 3 (E1) and 150 nmol mol ?1 O 3 (E2), in open-top chambers under field conditions from 21st March to 2nd November 2015. In this study, O 3 fumigation significantly reduced net photosynthesis rate (Pn) in M. ichangensis in the three measurements and in T. chinensis in the last measurement. Also, non-stomatal factors should be primarily responsible for the decreased Pn. O 3 fumigation-induced increase in malondialdehyde, superoxide dismutase, and reduced ascorbic acid levels indicated that antioxidant defense mechanism had been stimulated to prevent O 3 stress and repair the oxidative damage. Yet, the increase of antioxidant ability was not enough to counteract the harm of O 3 fumigation. Because of the decrease in CO 2 assimilation, the growth of the two tree species was restrained ultimately. The sensitivity of the two tree species to O 3 can be determined: M. ichangensis > T. chinensis. It suggests a close link between the rising O 3 concentrations and the health risk of some tree species in subtropics in the near future. 相似文献
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