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1.
The influence of dissolved NO 2 and iron on the oxidation rate of S(IV) species in the presence of dissolved oxygen is presented. To match the conditions in the real environment, the concentration of iron in the reaction solution and trace gases in the gas mixture was typical for a polluted atmosphere. The time dependence of HSO 3−, SO 42−, NO 2− and NO 3− and the concentration ratio between Fe(II) and total dissolved iron were monitored. Sulphate formation was the most intensive in the presence of an SO 2/NO 2/air gas mixture and Fe(III) in solution. The highest contribution to the overall oxidation was from Fe-catalysed S(IV) autoxidation. The reaction rate in the presence of both components was equal to the sum of the reaction rates when NO 2 and Fe(III) were present separately, indicating that under selected experimental conditions there exist two systems: SO 2/NO 2/air and SO 2/NO 2/air/Fe(III), which are unlikely to interact with each other. The radical chain mechanism can be initiated via reactions Fe(III)–HSO 3− and NO 2–SO 32−/HSO 3−. 相似文献
2.
Phosphorus (P) loading from non-point or point sources increases the eutrophication risk of natural waters. The functioning of constructed wetlands (CWs) used as natural water treatment systems can be improved by means of additional materials adsorbing soluble P. In this study, light expanded clay aggregates (LECA) and LECA coated with aluminum (Al) oxide (Al-LECA) or iron (Fe) oxide (Fe-LECA) were tested for their efficiency as P sorbents in the pH range 3–8. The oxide coatings duplicated the actual sorption capacity calculated from the sorption isotherms at the P concentration in the equilibrium solution of 20 μg L −1, assumed to be the allowable P level in purified water. In the oxide-coated LECAs the sorption was fast and followed both the first- and second-order Lagergren kinetic models, suggesting that the formation of a binuclear surface complex was feasible. In LECA, sorption was markedly slower and followed the first-order kinetic model, indicating that retention occurred through a monodentate attachment. These findings were in harmony with the degree of P saturation (DPS) of the sorbent surfaces at the highest P addition level (200 μg L −1), DPS being decisively higher for LECA than for the oxide-coated sorbents. Accordingly, at higher pH values the competition by hydroxyl ions diminished the sorption in LECA relatively more than that in the coated sorbents. In agreement with the acidity of Al 3+ being 100 times lower than that of Fe 3+, at elevated pH the sorption by Al-LECA proved to be less reversible than that by Fe-LECA. The results provide evidence that in CWs Al-coated sorbents are superior to Fe-coated ones that are also redox-sensitive and may lose their sorption properties in anoxic conditions. 相似文献
3.
Introduction The aims of the present study are to investigate the effects of Ce 3+ on the growth and some antioxidant metabolisms in rice seedlings ( Oryza sativa L. cv Shengdao 16). Materials and methods The rice was treated with 0, 0.05, 0.1, 0.5, 1.0, and 1.5?mM Ce 3+, respectively. The growth index of rice was measured. The chlorophyll content; catalase, superoxide dismutase, and peroxidase activities; and the level of hydrogen peroxide (H 2O 2), superoxide anion (O 2 ·? ), and malondialdehyde were assayed. The accumulation of Ce 3+ and the uptake of mineral nutrition elements were analyzed with ICP-SF-MS. Results and discussion Hormetic effects of Ce 3+ on the growth and some antioxidant metabolisms were found in the roots and shoots of rice. The roots can accumulate a much higher content of Ce 3+ than shoots and Ce 3+ mainly located in the cell wall of roots. Moreover, the uptake of K, Mg, Ca, Na, Fe, Mn, Zn, Cu, and Mo in the roots and shoots was affected with the exposure of different Ce 3+ treatments, which indicated that Ce 3+ affected the nutritional status of roots and shoots and further affected the growth of rice. Conclusion The appropriate amount of Ce 3+ improved the defense system and growth of rice. The roots can accumulate a much higher content of Ce 3+ than shoots. Moreover, the uptake of K, Mg, Ca, Na, Fe, Mn, Zn, Cu, and Mo in the roots and shoots was affected with the exposure of different Ce 3+ treatments. 相似文献
4.
This study investigated the characteristics of iron corrosion scales in pipes at tube well, overhead tank, and consumers’ end in older untreated water distribution system in Peshawar city, Pakistan. Effect of water quality conditions on corrosion scales and that of scales on drinking water quality in such systems was also assessed by undertaking a comparison with new piped distribution systems. The scales were analyzed for chemical composition and morphology using X-ray diffraction (XRD), inductively coupled plasma (ICP), and a scanning electron microscope (SEM), while water quality was examined for physicochemical and biological characteristics. The main crystalline phases of corrosion scales were goethite, magnetite, siderite, and quartz. From tube well to consumers’ end, goethite increased from 36 up to 48%, quartz declined from 22 to 15%, while magnetite fluctuated and siderite disappeared. Elemental composition of scales showed the deposition of Zn, Al, Mn, Cr, Pb, Cu, As, and Cd with Zn (13.9 g/kg) and Al (3.6 g/kg) in highest proportion. The SEM analysis illustrated the presence of microbial communities indicating the formation of biofilms in the corrosion scales. The significant difference (P <?0.05) in levels of dissolved oxygen (DO), Cl?, SiO44?, electrical conductivity (EC), SO42?, NO3?, alkalinity, hardness, and trace metals between old (DS-O) and new piped systems indicated their role in corrosion scale formation/destabilization and the effect of scale dissolution on water quality. In DS-O, EC, Cu, and Mn were significantly higher (P?<?0.05), whereas turbidity, EC, DO, and SiO44? significantly increased from source to consumers’ end implying a higher dissolution of scales and lowered corrosion rates in DS-O to utilize SiO44? and DO for iron oxidation. 相似文献
5.
The iron (Fe) (hydro)oxides deposited around rice roots play an important role in arsenic (As) sequestration in paddy soils, but there is no systematic study on the relative importance of Fe (hydro)oxides on root surface and in rhizosphere soil in limiting As bioavailability. Twenty-seven rice genotypes were selected to investigate effects of Fe (hydro)oxides on As uptake by rice in an alkaline paddy soil. Results indicated that the As content was positively correlated with the Fe content on root surface, and most of As (88–97%) was sequestered by poorly crystalline and crystalline Fe (hydro)oxides in the alkaline paddy soil. The As sequestration by Fe (hydro)oxides on root surface (IASroot 16.8–25.0 mg As/(g Fe)) was much higher than that in rhizosphere (IASrhizo 1.4–2.0 mg As/(g Fe)); therefore, in terms of As immobilization, the Fe (hydro)oxides on root surface were more important than that in rhizosphere. However, the As content in brown rice did not have significant correlation with the As content on root surface but was significantly correlated (R2?=?0.43, P?<?0.05) with the partition ratio (PRAs?=?IASroot/IASrhizo) of As sequestration on root surface and in rhizosphere, which suggested that Fe (hydro)oxides on root surface did not play the controlling role in lowering As uptake, and the partition ratio PRAs would be a better indicator to evaluate effects of Fe (hydro)oxides around roots on As uptake by rice. 相似文献
6.
The aims of this study are to investigate whether and how the nitrogen form (nitrate (NO 3 –) versus ammonium (NH 4 +)) influences cadmium (Cd) uptake and translocation and subsequent Cd phytoextraction by the hyperaccumulator species Sedum plumbizincicola. Plants were grown hydroponically with N supplied as either NO 3 – or NH 4 +. Short-term (36 h) Cd uptake and translocation were determined innovatively and quantitatively using a positron-emitting 107Cd tracer and positron-emitting tracer imaging system. The results show that the rates of Cd uptake by roots and transport to the shoots in the NO 3 – treatment were more rapid than in the NH 4 + treatment. After uptake for 36 h, 5.6 (0.056 μM) and 29.0 % (0.290 μM) of total Cd in the solution was non-absorbable in the NO 3 – and NH 4 + treatments, respectively. The local velocity of Cd transport was approximately 1.5-fold higher in roots (3.30 cm h ?1) and 3.7-fold higher in shoots (10.10 cm h ?1) of NO 3 –- than NH 4 +-fed plants. Autoradiographic analysis of 109Cd reveals that NO 3 – nutrition enhanced Cd transportation from the main stem to branches and young leaves. Moreover, NO 3 – treatment increased Cd, Ca and K concentrations but inhibited Fe and P in the xylem sap. In a 21-day hydroponic culture, shoot biomass and Cd concentration were 1.51 and 2.63 times higher in NO 3 –- than in NH 4 +-fed plants. We conclude that compared with NH 4 +, NO 3 – promoted the major steps in the transport route followed by Cd from solution to shoots in S. plumbizincicola, namely its uptake by roots, xylem loading, root-to-shoot translocation in the xylem and uploading to the leaves. S. plumbizincicola prefers NO 3 – nutrition to NH 4 + for Cd phytoextraction. 相似文献
7.
研究Fe/Cr6+比值和不同浓度的NO3-、Cl-和SO42-对金属铁去除Cr6+效果的影响.结果表明,金属铁对水中Cr6+有很好的还原去除效果;当金属铁的使用量为Cr6+量的1/2000时,铁对Cr6+的去除效果较差且易失去活性,而当金属铁的使用量为Cr6+量的8 000倍时,铁对Cr6+的去除效果较好且其活性的持续... 相似文献
8.
The total (wet and dry) deposition of trace and major elements from the atmosphere was measured throughout 1 year at twelve sampling stations in the ‘Campo de Gibraltar’, an industrial zone where there are important residential areas. The data included in this paper have contributed to a better knowledge of the regional deposition of Al, Cr, Fe, Mn, Ni, Pb, V, Zn, Ca, Mg, K, Na, Cl −, NH 4+, NO 3−and SO 42− in both soluble and insoluble form. 相似文献
9.
Size-segregated aerosol samples (PM 2.5 and PM 10) were collected during Jan–Dec-2007 from a high-altitude site located in a semi-arid region (Mt. Abu, 24.6 °N, 72.7 °E, 1680 m asl) in order to asses the temporal variability in the abundance of atmospheric mineral dust and its elemental composition over western India. The mass concentrations of fine (PM 2.5) and coarse (PM 10–2.5) mode aerosols varied from 1.6 to 46.1 and 2.3 to 102 μg m ?3 respectively over the annual seasonal cycle; with dominant and uniform contribution of mineral dust (60–80%) in the coarse mode relative to large temporal variability (11–75%) observed in the fine mode. The coarse mass fraction shows a characteristic increase with the wind speed during summer months (Mar to Jun); whereas fine aerosol mass and its elemental composition exhibit conspicuous temporal pattern associated with north-easterlies during wintertime (Oct–Feb). The Fe/Al weight ratio in PM 2.5 ranges from 0.5 to 1.0 during winter months. The relative enrichment of Fe in fine mode, compared to the crustal ratio of 0.44, is attributed to the down-wind advective transport of combustion products derived from large-scale biomass burning, industrial and automobile emission sources located in the Indo-Gangetic Plain (northern India). In contrast, Ca/Al and Mg/Al weight ratios show relative enrichment of Ca and Mg in the coarse mode; indicating their dominant contribution from carbonate minerals. This has implication to efficient neutralization of atmospheric acidic species (SO 42? and NO 3?) by mineral dust over western India. 相似文献
10.
Most studies on the treatment of chlorinated contaminants by Fe(0) focus on aqueous system tests. However, few is known about the effectiveness of these tests for degrading chlorinated contaminants such as 1,1,1-trichloroethane (TCA) in soil. In this work, the reductive degradation performance of 1,1,1-TCA by Fe(0) was thoroughly investigated in a soil slurry system. The effects of various factors including acid-washed iron, the initial 1,1,1-TCA concentration, Fe(0) dosage, slurry pH, and common constituents in groundwater and soil such as Cl ?, HCO 3 ?, SO 4 2?, and NO 3 ? anions and humic acid (HA) were evaluated. The experimental results showed that 1,1,1-TCA could be effectively degraded in 12 h for an initial Fe(0) dosage of 10 g L ?1 and a soil/water mass ratio of 1:5. The soil slurry experiments showed two-stage degradation kinetics: a slow reaction in the first stage and a fast reductive degradation of 1,1,1-TCA in the second stage. The reductive degradation of 1,1,1-TCA was expedited as the mass concentration of Fe(0) increased. In addition, high pHs adversely affected the degradation of 1,1,1-TCA over a pH range of 5.4–8.0 and the reductive degradation efficiency decreased with increasing slurry pH. The initial 1,1,1-TCA concentration and the presence of Cl ? and SO 4 2? anions had negligible effects. HCO 3 ? anions had a accelerative effect on 1,1,1-TCA removal, and both NO 3 ? and HA had inhibitory effects. A Cl ? mass balance showed that the amount of Cl ? ions released into the soil slurry system during the 1,1,1-TCA degradation increased with increasing reaction time, suggesting that the main degradation mechanism of 1,1,1-TCA by Fe(0) in a soil slurry system was reductive dechlorination with 1,1-DCA as the main intermediate. In conclusion, this study provides a theoretical basis for the practical application of the remediation of contaminated sites containing chlorinated solvent. 相似文献
11.
Nitrogen-doped titanium dioxide (TiO2) and Fe–N-codoped TiO2 layers on fly ash cenospheres (FAC) as floating photocatalyst were successfully prepared through sol–gel method. Photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)–Vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption analyses for Brunauer–Emmett–Teller (BET) specific surface area. Photocatalytic efficiency of the prepared catalyst was evaluated through using the decomposition of Rhodamine B (RhB) as a model compound under visible light irradiation. Photocatalytic activity and kinetics of catalyst under visible light were detected in details from different Fe/Ti mole ratios by detecting photodegradation of RhB. Experimental results show that when the calcination temperature was 550 °C, the dosage of FAC was 3.0 g, and the mole ratio of Fe/Ti was 0.71 %; the synthesized Fe–N-TiO2/FAC photocatalyst presented as anatase phase and that N and Fe ions were doped into TiO2 lattice. The material’s specific surface area was 34.027 m2/g, and UV–Vis diffuse reflectance spectroscopy shows that the edge of the photon absorption has been red shifted up to 400–500 nm. Fe–N-codoped titanium dioxide on FAC had excellent photocatalytic activity during the process of photodegradation of RhB under visible light irradiation. 相似文献
12.
Potential source contribution function (PSCF) was employed to study the source receptor relationships for 14 chemical species (Mn, SO 42−, Zn, Al, Fe, Cu, Cr, Ni, Cd, NO 3, NH 4+, K +, Mg 2+,and Pb) found in precipitation collected at Lewes, Delaware. This study identified areas of the Eastern United States as possible emission source areas that could have contributed to the 14 element concentrations observed at Lewes. The identified regions in the Eastern United States generally coincide well with known emission source areas. The likely emission sources for these chemical species include oil- and coal-fired power plants, incinerators, motor vehicles, and iron and steel mills. 相似文献
13.
Experiments were conducted to assess the impact of citric acid (CA) and rhizosphere bacteria on metal uptake in Phragmites australis cultured in a spiked acid mine drainage (AMD) soil. Rhizosphere iron-oxidizing bacteria (Fe(II)OB) enhanced the formation of Fe plaque on roots, which decreased the uptake of Fe and Mn. CA inhibited the growth of Fe(II)OB, decreased the formation of metal plaque, raised the metal mobility in soil, and increased the accumulation of metals in all tissues of the reeds. The higher the CA dosage, the more metals accumulated into reeds. The total amount of metals in reeds increased from 7.8?±?0.5?×?10 ?6 mol plant ?1 (Mn), 1.4?±?0.1?×?10 ?3 mol plant ?1 (Fe), and 1.0?±?0.1?×?10 ?4 mol plant ?1 (Al) in spiked soil without CA to 22.2?±?0.5?×?10 ?6 mol plant ?1 (Mn), 3.5?±?0.06?×?10 ?3 mol plant ?1 (Fe), and 5.0?±?0.2?×?10 ?4 mol plant ?1 (Al) in soil added with 33.616 g C 6H 8O 7·H 2O for per kilogram soil. CA could be effective at enhancing the phytoremediation of metals from AMD-contaminated soil. 相似文献
14.
The objectives of this research were to study the effects of Na 2SiO 3 application on the uptake, translocation, and accumulation of Pb in rice and to investigate the mechanisms of Pb immobilization by Na 2SiO 3 in paddy rice soils and rice plants. Pot experiments were conducted using a Cd-Pb-Zn-polluted soil and Oryza sativa L. ssp . indica cv. Donglian 5. L 3-edge X-ray absorption spectroscopy was used to identify Pb species in soils and roots. The results showed that the application of Na 2SiO 3 increased soil pH and available soil Si but decreased DTPA-extractable Pb in the soil. High dose of Na 2SiO 3 (12.5 g/kg) reduced the Pb level in brown rice as it inhibited Pb transfer from soil to rice grains, especially Pb transfer from the root to the stem. The Pb X-ray absorption near-edge spectroscopic analysis revealed that application of high dose of Na 2SiO 3 increased Pb-ferrihydrite and PbSiO 3 precipitates in the soil and in the root while it reduced Pb-humic acids (Pb-HAs) in the soil and Pb-pectin in the root. The decrease in Pb availability in the soil can be partly attributed to increase the precipitation of PbSiO 3 and the association of Pb 2+ with Fe oxides in the soil. The inhibition of the root-to-stem translocation of Pb was partially due to the precipitation of PbSiO 3 on the root surfaces or inside the roots. 相似文献
15.
ABSTRACT A previous paper 1 discusses the methodology for a new method for deriving the nitrogen dioxide/nitrogen oxide (NO 2/NO x) ratio in plumes that originally are composed mainly of (NO x). It is called the Plume Volume Molar Ratio Method (PVMRM). This paper documents its performance against six different data sets. These performance evaluations show that the PVMRM can realistically predict the NO 2 fraction at close-in receptors yet still provide conservative estimates so that the air quality standards can be protected. 相似文献
16.
The effects of the burning of fireworks on air quality in Beijing was firstly assessed from the ambient concentrations of various air pollutants (SO 2, NO 2, PM 2.5, PM 10 and chemical components in the particles) during the lantern festival in 2006. Eighteen ions, 20 elements, and black carbon were measured in PM 2.5 and PM 10, and the levels of organic carbon could be well estimated from the concentrations of dicarboxylic acids. Primary components of Ba, K, Sr, Cl −, Pb, Mg and secondary components of C 5H 6O 42−, C 3H 2O 42−, C 2O 42−, C 4H 4O 42−, SO 42−, NO 3− were over five times higher in the lantern days than in the normal days. The firework particles were acidic and of inorganic matter mostly with less amounts of secondary components. Primary aerosols from the burning of fireworks were mainly in the fine mode, while secondary formation of acidic anions mainly took place on the coarse particles. Nitrate was mainly formed through homogeneous gas-phase reactions of NO 2, while sulfate was largely from heterogeneous catalytic transformations of SO 2. Fe could catalyze the formation of nitrate through the reaction of α-Fe 2O 3 with HNO 3, while in the formation of sulfate, Fe is not only the catalyst, but also the oxidant. A simple method using the concentration of potassium and a modified method using the ratio of Mg/Al have been developed to quantify the source contribution of fireworks. It was found that over 90% of the total mineral aerosol and 98% of Pb, 43% of total carbon, 28% of Zn, 8% of NO 3−, and 3% of SO 42− in PM 2.5 were from the emissions of fireworks on the lantern night. 相似文献
17.
Traffic-generated air pollutant emissions can be classified into exhaust and non-exhaust emissions. Increased attention is focussing on non-exhaust emissions as exhaust emissions are progressively limited by regulations. To characterise metal-rich emission from abrasion processes, size-segregated analysis of atmospheric aerosol particles sampled with micro-orifice uniform deposit impactors (MOUDI) in March 2007 in London was performed. The samples were collected at a roadside and a background site and were analysed for Al, Ba, Cu, Fe, Sb, Ti, V, Zn, Ca 2+, K +, Mg 2+, Na +, and NH 4+. Most components showed a clear roadside increment, which was evident as a higher mass concentration and a change in the size distribution. In particular, Fe, Cu, Ba, and Sb correlated highly, indicative of a common traffic-related source. Using complementary information on the fleet composition, vehicle number and average speed, the brake wear emission was calculated using the EMEP/CORINAIR emission database. The total PM 10 and barium emission of the traffic was determined by ratio to NO x whose source strength was estimated from published emission factors. Barium was found to comprise 1.1% of brake wear (PM 10) particles from the traffic fleet as a whole, allowing its use as a quantitative tracer of brake wear emissions at other traffic-influenced sites. 相似文献
18.
NO X fluxes from three kinds of vegetable lands and a rice field were measured during summer–autumn in the Yangtze Delta, China. The average NO fluxes from the rice fields (RF), celery field (CE), maize field (MA) and cowpea field (CP) were 4.1, 30.8, 54 and 32.2 ng N m ?2 s ?1, respectively; and the average NO 2 fluxes were ?2.12, 0.68, 1.33 and 0.5 ng N m ?2 s ?1, respectively. The liquid N fertilizer (the mixture of swine excrement and urine) which is widely applied to vegetable lands by Chinese farmers was found to quickly stimulate NO emission, and have significant contribution to NO emission from the investigated vegetable lands. Apparent linearity correlations were found between NO 2 fluxes and the ambient concentrations of the rice fields, with a compensation point of about 2.84 μg m ?3. Total emissions of NO during summer–autumn time from this area were roughly estimated to be 4.1 and 8.4 Gg N for rice field and vegetable lands, respectively. 相似文献
19.
A sampling campaign of re-suspended road dust samples from 53 sites that could cover basically the entire Beijing, soil samples from the source regions of dust storm in August 2003, and aerosol samples from three representative sites in Beijing from December 2001 to September 2003, was carried out to investigate the characteristics of re-suspended road dust and its impact on the atmospheric environment. Ca, S, Cu, Zn, Ni, Pb, and Cd were far higher than its crustal abundances and Ca 2+, SO 42−, Cl −, K +, Na +, NO 3− were major ions in re-suspended road dust. Al, Ti, Sc, Co, and Mg in re-suspended road dust were mainly originated from crustal source, while Cu, Zn, Ni, and Pb were mainly derived from traffic emissions and coal burning, and Fe, Mn, and Cd were mainly from industrial emissions, coal combustion and oil burning. Ca 2+ and SO 42− mainly came from construction activities, construction materials and secondary gas-particle conversions, Cl − and Na + were derived from industrial wastewater disposal and chemical industrial emissions, and NO 3− and K + were from vehicle emissions, photochemical reactions of NO X, biomass and vegetable burning. The contribution of mineral aerosol from inside Beijing to the total mineral aerosols was ∼30% in spring of 2002, ∼70% in summer of 2002, ∼80% in autumn of 2003, ∼20% in PM 10 and ∼50% in PM 2.5, in winter of 2002. The pollution levels of the major pollution species, Ca, S, Cu, Zn, Ni, Pb, Fe, Mn, and Cd in re-suspended road dust reached ∼76%, ∼87%, ∼75%, ∼80%, ∼82%, ∼90%, ∼45%, ∼51%, and ∼94%, respectively. Re-suspended road dust from the traffic and construction activities was one of the major sources of pollution aerosols in Beijing. 相似文献
20.
Abstract Air pollutants were collected in Logan, Cache County, UT, in February 1993 during two periods of atmospheric inversion accompanied by fog. The following atmospheric species were determined: (1) gaseous SO 2, NO 2 (semi-quantitatively),HNO3, NH3, and HF; (2) fine particulate SO 4 =, NO 3 -, NH 4 +, F–, H +, C, Si, S, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Pb, Se, Br, and Sr, and; (3) fine particulate mass, which was calculated. The major components of fine particulate matter were carbonaceous material, ammonium nitrate, and ammonium sulfate, while the soil component was small. Calculated, fine particulate mass averaged 80 μg/m 3 and reached concentrations as high as 120 μg/m 3. SO 2/So x and NO 2/NO y mole ratios generally varied between 0.2 and 0.1 during inversions. These ratios also showed moderate but consistent diurnal patterns. The emission inventory for Cache County indicates sources of SO 2 and NO x but not significant amounts of primary sulfate and nitrate. The observations reported here indicate there is significant conversion of SO 2 and NO x in the presence of excess oxidants to sulfuric and nitric acid that are neutralized by excess ammonia. 相似文献
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