Effect of ammonium and oxygen on methane and nitrous oxide fluxes across sediment-water interface in a eutrophic lake

Eutrophication has decreased the O(2) content and increased the NH(4)(+) availability in freshwaters. These changes may affect carbon and nitrogen transformation processes and the production of CH(4) and N(2)O, which are important greenhouse gases. We studied release of CH(4) and N(2)O from a eutrophic lake sediment under varying O(2) and NH(4)(+) conditions. Intact sediment cores were incubated in a laboratory microcosm with a continuous anoxic or oxic water flows containing 0, 50, 500, 5,000, or 15000 microM NH(4)(+). With the anoxic flow, the sediment released CH(4), up to 7.9 mmol m(-2)d(-1). With the oxic flow, the CH(4) emissions were small indicating limited CH(4) production and/or effective CH(4) oxidation. Addition of NH(4)(+) did not affect sediment CH(4) release, evidence that the CH(4) oxidizing bacteria were not disturbed by the extra NH(4)(+). The release of N(2)O from the sediment was highest, up to 7.6 micromol m(-2)d(-1), with the oxic flow without NH(4)(+) addition. Oxygen was the key factor regulating the production of NO(3)(-), which enabled denitrification and production of N(2)O. However, the highest NH(4)(+) addition increased nitrification and associated O(2) consumption causing a decrease in sediment O(2) content and in accumulation of NO(3)(-) and N(2)O, which were effectively reduced to N(2) in denitrification. In summary, sediment CH(4) and N(2)O dynamics are regulated more by the availability of O(2) than extra NH(4)(+). Anoxia in eutrophic lakes favouring the CH(4) production, is the major contributor to the atmospheric consequences of water eutrophication.     

Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent

In this paper, a comparison of various advanced oxidation processes (O3, O3/UV, H2O2/UV, O3/H2O2/UV, Fe2+/H2O2) and chemical treatment methods using Al2(SO4)3.18H2O, FeCl3 and FeSO4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color and COD removal for the textile effluent used in this study was 50% and 60%, respectively. Although O3/H2O2/UV combination among other AOPs methods studied in this paper was found to give the best result (99% removal for COD and 96% removal for color), use of Fe2+/H2O2 seems to show a satisfactory COD and color removal performance and to be economically more viable choice for the acetate and polyester fiber dyeing effluent on the basis of 90% removal.     

The promoter effect and a rate expression of the catalytic incineration of (CH3)2S2 over an improved CuO-MoO3/gamma-Al2O3 catalyst

The CuO-MoO3/gamma-Al2O3 catalyst, confirmed previously as having good activity in the catalytic incineration of (CH3)2S2, was employed as the principal catalyst in this study. With the aim of improving catalyst activity and resistance to deactivation by sulfur compounds, a promoter was added either before adding the precursors of Cu and Mo or together with Cu and Mo onto the gamma-Al2O3. Promoters included transition metals and elements from groups IA-VIIA in the chemical periodic table. Experimental results reveal Cr2O3 as the most effective promoter, with an optimal composition of 5 wt.% Cu, 6 wt.% Mo and 4 wt.% Cr (designated as Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3). Knowing that higher acidity can improve activity, we further investigated the effect of acid treatment on the performance of the Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3 catalyst. Experimental results indicate the H2SO4-treated catalyst (Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3) has a better activity and durability. A study for finding an appropriate rate expression for the catalytic incineration of (CH3)2S2 by Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3 was carried out in a differential reactor. The results show that the Mars-Van Krevelen model is applicable to this destructive oxidation reaction. Results additionally reveal that competitive adsorption of CH4 reduces conversion of (CH3)2S2.     

Fabrication and characterization of 3,4-diaminobenzophenone-functionalized magnetic nanoadsorbent with enhanced VOC adsorption and desorption capacity

Environmental Science and Pollution Research - The present study, for the first time, utilized 3,4-diaminobenzophenone (DABP)-functionalized Fe3O4/AC@SiO2 (Fe3O4/AC@SiO2@DABP) magnetic...     

Fluxes of N2O, CH4 and CO2 in a meadow ecosystem exposed to elevated ozone and carbon dioxide for three years

Open-top chambers (OTCs) were used to evaluate the effects of moderately elevated O3 (40-50 ppb) and CO2 (+100 ppm) and their combination on N2O, CH4 and CO2 fluxes from ground-planted meadow mesocosms. Bimonthly measurements in 2002-2004 showed that the daily fluxes of N2O, CH4 and CO2 reacted mainly to elevated O3, while the fluxes of CO2 also responded to elevated CO2. However, the fluxes did not show any marked response when elevated O3 and CO2 were combined. N2O and CO2 emissions were best explained by soil water content and air and soil temperatures, and they were not clearly associated with potential nitrification and denitrification. Our results suggest that the increasing O3 and/or CO2 concentrations may affect the N2O, CH4 and CO2 fluxes from the soil, but longer study periods are needed to verify the actual consequences of climate change for greenhouse gas emissions.     

Predicting ozone-induced soybean losses: sensitivity to model form and inputs

In this study, alternative dose-response equations for assessing the effects of O3 on soybeans (Glycine max (L.) Merr.) were established. For each of three soybean cultivars, three models (linear, quadratic, and Weibull) were fitted to relate different measures of O3 dose, during the soybean flowering maturity period, to the soybean yield. The dose measures were 7-h (9:00 a.m. to 4:00 p.m.) and 12-h (7:00 a.m. to 7:00 p.m.) means, 7-h and 12-h total doses, and the 90th and 75th percentile O3 concentrations. Using data for primarily rural and small city O3 monitoring sites, county-level O3 doses were calculated, and soybean losses due to O3 were predicted for Illinois, Kentucky, and Virginia. The sensitivity of O3-induced soybean loss predictions to model forms and inputs was determined with regard to: (1) inter-year differences in ambient O3, (2) differences among the six dose measures, (3) differences among the three different model forms, (4) the impact of the agricultural practice of double-cropped soybean production, and (5) variance in response to O3 among three different soybean cultivars.     

Efficient use of Fe metal as an electron transfer agent in a heterogeneous Fenton system based on Fe0/Fe3O4 composites

In this work a novel heterogeneous Fenton system based on Fe(0)/Fe3O4 composites is described. The composites with several Fe(0)/Fe3O4 ratios were prepared by two different methods, i.e. mechanical alloying of Fe(0) and Fe3O4 powders and controlled reduction of Fe3O4 with H2. Reaction studies and detailed Conversion Electron M?ssbauer surface characterization of the composites Fe(0)/Fe3O4, Fe(0), Fe3O4, alpha-Fe2O3 and gamma-Fe2O3 suggested that Fe2+surf species are essential to produce an active Fenton system. Kinetic studies for the oxidation of the dye methylene blue, used as an organic model molecule, and for the peroxide decomposition suggest that the reactions proceed via HO* radicals generated from Fe2+surf species and H2O2 in a Fenton like mechanism. The increase in activity caused by the addition of Fe(0) is discussed in terms of a creation of Fe2+surf species during the preparation of the composite and by an electron transfer mechanism from Fe(0) to Fe3+surf during the Fenton reaction to regenerate the Fe2+surf active species.     

Temporal variation in daily concentrations of ozone and acid-related substances at Saturna Island, British Columbia

A multiple linear regression model was used to investigate seasonal and long-term trends in concentrations of ozone (O3) and acid-related substances at the Saturna Island monitoring station in southwestern British Columbia from 1991 to 2000. Statistically significant primary (dominant) cycles with a period of 1 yr were found for O3, sulfur dioxide (SO2), nitric acid (HNO3), and aerosol concentrations of sulfate (SO4(2-)), calcium (Ca2+) and chloride (Cl-). Of these, peak median concentrations occurred during the spring for O3 and Ca2+, during the warmer, drier months (April-September) for SO4(2-) and HNO3, and during the cooler, wetter months (October-March) for SO2 and Cl-. Statistically significant secondary cycles of 6 months duration were seen for concentrations of O3, SO4(2-), HNO3, Ca2+, and Cl-. Daily maximum O3 concentrations exhibited a statistically significant increase over the period of record of 0.33 +/- 0.26 ppb/yr. Statistically significant declines were found for concentrations of SO2, SO4(2-), HNO3, Ca2+, and potassium, ranging from 20 to 36% from levels at the start of the sampling period. Declines in ambient concentrations of SO2, SO4(2-), and HNO3 reflect local declines in anthropogenic emissions of the primary precursors SO2 and NOx over the past decade. Trends in Ca2+ and potassium ion concentrations are in line with a broader North American declining trend in acid-neutralizing cations.     

Removing and recovering gas-phase elemental mercury by Cu(x)Co(3-x)O(4) (0.75< or = x < or =2.25) in the presence of sulphur compounds

The Hg(0) oxidation ability and reusability of Cu(x)Co(3-x)O(4) were investigated in an attempt to improve SO(2) anti-poisoning ability of metal oxide and produce more economic and effective sorbents for the control of Hg(0) emission from combustion processes. The influence of copper content on Cu(x)Co(3-x)O(4)'s (0.75< or = x < or =2.25) oxidation ability of Hg(0) in the presence of SO(2) was investigated. According to the X-ray diffraction, Brunauer-Emmett-Teller (BET) and mass balance analysis on mercury, we found that Cu(1.5)Co(1.5)O(4) showed the highest S(BET) and best Hg(0) oxidation ability. With continuous increase of x from 0.75 to 2.25, Cu(x)Co(3-x)O(4)'s SO(2) anti-poisoning ability increased. The analysis results of the X-ray photoelectron spectroscopy manifested that the adsorptive mercury species on spent Cu(1.5)Co(1.5)O(4) was HgO. The spent Cu(1.5)Co(1.5)O(4) could be regenerated by thermal decomposition at 673K and regenerated Cu(1.5)Co(1.5)O(4) showed higher Hg(0) oxidation ability due to Hg-doping. Regenerated enrichment Hg(0) was collected using activated carbon at an ambient temperature to eliminate the secondary pollution.     

Responses of sensitive and tolerant bush beans (Phaseolus vulgaris L.) to ozone in open-top chambers are influenced by phenotypic differences, morphological characteristics, and the chamber environment

Responses of bush bean (Phaseolus vulgaris L.) lines 'S156' (O(3)-sensitive) and 'R123' (O(3)-tolerant), and cultivars 'BBL 290' (O(3)-sensitive) and 'BBL 274' (O(3)-tolerant) to ambient ozone (O(3)) were investigated during the 2001 and 2002 growing seasons. Seedlings were grown in pots inside open-top chambers (OTCs), with charcoal filtered (CF) and non-filtered (NF) ambient air, and in non-chambered ambient air (AA) plots. Growth parameters from individual plants were evaluated after harvests at the end of vegetative (V(4)) and reproductive (R(10)) growth phases. Results at V(4) indicated that CF did not provide additional benefits over NF in 'S156' in 2001 and 2002. In contrast, exposure to CF significantly impaired the growth of 'R123'. At the end of R(10), 'S156' produced more pods, most of which remained immature, and contained fewer seeds or were more frequently aborted, whereas pods produced in 'R123' reached pod maturation and senescence more consistently. Despite increased seed weights inside the OTCs, as observed in 'S156', differences between the two lines were insignificant when grown outside OTCs. Results from the 'BBL 290'/'BBL 274' pair, especially at V(4) phase, remained inconclusive. Plant morphological characteristics, variabilities in environmental conditions, and 'chamber effects' inside OTCs were influential in determining plant response to ambient O(3).     

Oxidant air pollution effects on plants of Joshua Tree National Monument

Joshua Tree National Monument (JOTR) is located about 100 km east of the Los Angeles Basin, site of the heaviest concentration of photochemical oxidant (O(3)) air pollution in the US. This investigation was conducted to measure O(3) concentrations in JOTR and to determine the effects of O(3) on vegetation in the park. Potentially phytotoxic concentrations of O(3) were recorded in JOTR in 1984 and 1985, but peak concentration occurred at night, when most plant species would be less sensitive to O(3). No O(3) effects were observed on permanent vegetation observation plots in JOTR in 1984 or 1985. Controlled exposures of native summer annual and woody perennial species to O(3) showed that most did not develop visible O(3) injury symptoms except at concentrations higher than those expected in the park. However, Rhus trilobata Nutt. was injured at 0.10 ppm O(3), 4 h per day for 4 days. This species would be a useful bioindicator to assess the effects of O(3) on native desert plants.     

Effect of liquefied petroleum gas on ozone formation in Guadalajara and Mexico City

Leakages of liquefied petroleum gas (LPG) are suspected to contribute greatly to ozone (O3) formation in Mexico City. We tested such a hypothesis by outdoor captive-air irradiation (CAI) experiments in the two largest Mexican metropolitan areas: Guadalajara (GMA) in 1997 and Mexico City (MCMA) in 2000. O3 was monitored in each city for 20 days (8:00 a.m.-6:00 p.m.) in smog chambers containing unaltered morning air or morning air enriched with either commercial LPG or LPG synthetic mixture 60/40 (propane and butane). Tested additions of both components were 35% (by volume) in GMA and 60% (by volume) in MCMA. The addition effects on O3 (max) were compared with effects from diluting LPG components or total nonmethane hydrocarbons (tNMHCs) by 50%. Diluting tNMHCs had the greatest absolute effect at both cities: it lowered O3 (max) by 24% in GMA and 55% in MCMA. Adding commercial LPG increased O3 (max) by 6% in GMA and 28% in MCMA; whereas adding LPG synthetic mixture 60/40 caused a similar increase in O3 (max), 4 and 21% in GMA and MCMA, respectively. Compared with dilution of tNMHCs, dilution of LPG-associated compounds had a smaller decreasing effect on O3 (max), only 4% in GMA and 15% in MCMA. These results show that commercial LPG and LPG synthetic mixture 60/40 affect O3 formation to a lesser extent than estimated previously.     

臭氧/高锰酸盐预氧化对生物过滤净水效能的影响

比较了臭氧(O3)和高锰酸盐复合药剂(PPC)对水源水预氧化的助凝效果及其对后续陶粒生物过滤净水效能的影响.结果表明,两种预氧化剂投加量均为2 mg/L时,PPC的助凝效果较为明显,浊度和溶解性有机碳(DOC)的去除率分别由未投加氧化剂时的85.7%和24.2%提高到88.3Z和35.2%;O3能够增加沉淀后水的可生化性,使特征紫外吸光度(SUVA)由0.97L/(m·mg)降至0.89 L/(m·mg).PPC预氧化有助于生物过滤对浊度的稳定去除,而O3预氧化则有助于生物过滤对DOC的去除.与O3预氧化相比,PPC预氧化有利于后续生物过滤运行初期对NH4 -N的去除,二者后续生物过滤在前3个月对NH4 -N的平均去除率分别为26.6%和73.1%,运行后期二者NH4 -N去除率接近.当进水NH4 -N大于2.0 mg/L时,DO是其去除的主要限制因素.     

Comparison of AC/O3-BAC and O3-BAC processes for removing organic pollutants in secondary effluent

AC (activated carbon)/O3-BAC (biological activated carbon) process was employed to treat secondary effluent and compared to O3-BAC process. The effects of ozone dosages and empty bed contact time (EBCT) in BAC on dissolved organic carbon (DOC) removal were investigated. The results showed that the presence of AC improved ozone utilization and biodegradability of the effluent. DOC removal increased with ozone dosage and EBCT in BAC, however, 3 mg l(-1) ozone dosage with 15 min oxidation time and 15 min EBCT in BAC were more economical and efficient. For DOC removal, AC/O3-BAC was more efficient than O3-BAC and its synergetic effect was more than that in O3-BAC process. The biomass of the subsequent BAC unit in AC/O3-BAC process was more than that in O3-BAC process and much more than that in BAC alone. Except for organic pollutants with molecular weight (MW) >10 kDa, those of other MW range were decomposed much more by AC/O3 process than by O3 process. GC/MS analysis showed that dibutyl phthalate, bis(2-ethylhexyl) phthalate, 4-bromo-3-chloroaniline, 2-propanone-ethylhydrazone and phenol derivatives were prevalent organic compounds in the secondary effluent. Some aromatic compounds, such as 4-bromo-3-chloroaniline and 2,4-dichloro-benzenamine disappeared after AC/O3 treatment. However, some small molecules were generated, after further biological treatment by BAC, the kinds and concentration of organic compounds were greatly reduced.     

Effects of fulvic acid on aggregation,sedimentation, and adsorption of Fe3O4 magnetic nanoparticles

Environmental Science and Pollution Research - Environmental behavior, bioavailability, and risks posed by Fe3O4, magnetic nanoparticles (Fe3O4 NPs) in surface waters are affected by complex...     

Multifunctional ZnO-Co3O4 @ polymer hybrid nanocoatings with controlled adsorption,photocatalytic and anti-microbial functions for polluted water systems

Environmental Science and Pollution Research - Triple action pollutant responsive multi-layer hybrid nanocoatings of architecture PEI(PAA/ZnO-Co3O4)n were constructed through ZnO-Co3O4 binary oxide...     

Tomato response to concurrent and sequential NO2 and O3 exposures

In the ambient environment, concentrations of air pollutants vary on a diurnal cycle, resulting in various patterns of concurrent and sequential exposures of plants. The response of tomato plants to sequential and concurrent NO2 and O3 exposures was determined using pollutant levels equal to the maximum acceptable levels recommended by the National Ambient Air Quality Objectives of Environment Canada for a 1 h average. The concurrent treatment, 1 h of NO2 + O3, was compared to 1 h of NO20, O3 or control in plants at the 4 to 6 or the 9 to 11 leaf stage. At the 4 to 6 leaf stage, leaf and stem fresh weights were significantly reduced by the NO2 + O3 treatment relative to control, whereas these growth parameters were not reduced relative to control by the single pollutants indicating a coalitive response. Leaf area was significantly smaller as a result of the NO2 + O3 treatment relative to the NO2 treatment. A main effect of O3 was observed on leaf dry weight. The sequential treatments were: NO2 followed by O3 (NO2-O3); O3 followed by NO2 (O3-NO2); NO2 at night followed by O3 during the daytime (NO2(N)-O3(D)). Each gas exposure was 1 h; only plants at the 4 to 6 leaf stage were treated. Only the O3-NO2 treatment significantly reduced leaf area, leaf fresh weight and stem fresh and dry weights relative to control plants. Inconsistencies among treatments occurring at different time periods of the day suggest that time period of exposure should reflect ambient time periods. The coalitive action, and the sequential treatment response, of these pollutants indicated that criteria based on single pollutants may not be adequate to establish air quality objectives when these pollutants occur together.     

Yield loss assessments for cultivars of broccoli, lettuce, and onion exposed to ozone

The effects of the photochemical oxidant air pollutant ozone (O(3)) on growth and yield of three garden crops, broccoli (Brassica oleracea L.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.) were studied in an open-top chamber experiment conducted in the field in southern California. Four cultivars each of leaf lettuce, broccoli, and globe onion were exposed to charcoal-filtered air (CF), non-filtered (NF) air, or NF plus 1.5 times ambient O(3) concentration from 4 weeks after germination in January or February until harvest. Exposures lasted 31 days for lettuce, 55 to 78 days for broccoli, and 105 days for onion. Results showed that despite severe O(3) injury to outer leaves, lettuce yields were not affected by O(3). Broccoli also was resistant to O(3) and no growth reduction was observed at ambient O(3) concentrations. Onions were more susceptible to O(3), but only one cv. 'Rio Bravo' had significant yield losses (ca. 5%) at ambient O(3) levels. These results suggest that, in general, concentrations of O(3) in the winter and spring may be below the threshold for adverse effects on yields of broccoli, lettuce and onion.     

Mercury volatilisation and phytoextraction from base-metal mine tailings

Experiments were carried out in plant growth chambers and in the field to investigate plant-mercury accumulation and volatilisation in the presence of thiosulphate (S2O3)-containing solutions. Brassica juncea (Indian mustard) plants grown in Hg-contaminated Tui mine tailings (New Zealand) were enclosed in gastight volatilisation chambers to investigate the effect of ammonium thiosulphate ([NH4]2 S2O3) on the plant-Hg volatilisation process. Application of (NH4)2 S2O3 to substrates increased up to 6 times the Hg concentration in shoots and roots of B. juncea relative to controls. Volatilisation rates were significantly higher in plants irrigated only with water (control) when compared to plants treated with (NH4)2 S2O3. Volatilisation from barren pots (without plants) indicated that Hg in tailings is subject to biological and photochemical reactions. Addition of sodium thiosulphate (Na2S2O3) at 5 g/kg of substrate to B. juncea plants grown at the Tui mine site confirmed the plant growth chambers studies showing the effectiveness of thio-solutions at enhancing shoot Hg concentrations. Mercury extraction from the field plots yielded a maximum value of 25 g/ha. Mass balance studies revealed that volatilisation is a dominant pathway for Hg removal from the Tui mine site. A preliminary assessment of the risks of volatilisation indicated that enhanced Hg emissions by plants would not harm the local population and the regional environment.     

Mechanisms of NOx removal from flue gas by zero valent iron

Chemical reaction between nitric oxide (NO) andzero valent iron (ZVI) was studied in a packed-bed column process with high temperatures based on ZVI strong reducing abilities. For six controlled temperatures of 523-773 K and 400 ppm of NO (typical flue gas temperature and concentration), under short empty bed contacttime ([EBCT] 0.0226-0.0679 sec), NO was completely removed for temperature of 573-773 K but not for 523 K. Break-through curves were conducted for the five working temperatures, and the results indicated that NO reductions by ZVI were varied from 2 to 26.7 mg NO/g ZVI. Higher temperature and longer EBCT achieved better NO removal efficiency. X-ray diffraction (XRD) and electron spectroscopy for chemical analysis (ESCA) were conducted to analyze the crystal structure and oxidation state of the reacted ZVI. Three layers of iron species were detected by XRD: ZVI, Fe3O4, and Fe2O3. ZVI was the most prevalent species, and Fe3O4 and Fe2O3 were less from the XRD analysis. By ESCA, the oxidation state on the reacted ZVI surface was determined, and the species was identifled as Fe2O3, which is the most oxidizing species for iron. Therefore, three layers from the ZVI core to the ZVI surface can be identified: ZVI, Fe3O4, and Fe2O3. Combining the results from XRD and ESCA, the mechanisms for ZVI and NO can be proposed as two consecutive reactions from lower oxidation state (ZVI) in the core to higher oxidation state on the iron surface (Fe2O3): 3Fe + 4NO<--(high temperature)-->Fe3O4 + 2N2 (A1), 4Fe3O4 + 2NO<--(high temperature)-->6Fe2O3 + N2* (A2) Because there was only <5% ZVI used to remove NO comparing to theoretical ZVI used based on the proposed stoichiometry, it can be concluded that the heterogeneous reaction only occurred on the ZVI surface instead of on bulk of the ZVI.