The impact of ambient ozone on mountain spruce forests in the Czech Republic as indicated by malondialdehyde

Malondialdehyde (MDA), a product of lipid peroxidation and biomarker of oxidative stress, is measured over the long term in spruce Picea abies needles under real conditions in three Czech mountain border areas. The trends presented collate the MDA content in spruce needles with ambient ozone, temperature and precipitation as casual, and defoliation as a subsequent factor for the period 1994-2006. We have found the overall decreasing trends in MDA and defoliation. The highest MDA and defoliation are recorded in the Jizerske, the lowest in the Krusne hory Mts. Out of the examined variables the MDA is predicted best by mean temperature in vegetation season, median of O₃ concentrations and AOT40; these three variables account for 34% of MDA1 and 36% of MDA2 variability. Our hypothesis that higher ambient O₃ exposure results in higher MDA contents in P. abies needles under real conditions has not been approved.     

脉冲电晕低温等离子体提高一氧化氮氧化效率的实验研究

提高一氧化氮（NO）的氧化效率对于提高生物法处理该类废气的净化效率具有重要意义。实验研究了低温等离子体在脉冲电晕条件下氧化废气中NO的过程,考察了不同峰值电压、氧气含量、气体停留时间和添加有机物等因素对提高NO氧化效率的影响。结果表明：低温等离子法可有效地提高NO的氧化效率,主要产物为NO₂;室温条件下,当进气NO浓度590 mg/m³、脉冲频率50 Hz时,增大峰值电压、气体停留时间和进气中的氧气含量可提高NO的氧化效率;在最适峰值电压15 kV,气体停留时间5 s时,NO氧化效率为20%;在进气NO中添加甲苯、乙醇后,NO氧化效率可增加至30%以上,甲苯的效果要好于乙醇。     

Contribution of isoprene to formaldehyde and ozone formation based on its oxidation products measurement in Beijing,China

The atmospheric mixing ratios of methacrolein (MACR) and methyl vinyl ketone (MVK), the two specific products from isoprene oxidation in the atmosphere, were measured in Beijing from March to November, 2006. Distinct amounts of MACR and MVK were detected during vegetable growing seasons from April to October with ambient levels of 0.11–0.67 ppbv and 0.19–1.36 ppbv, respectively. The reacted isoprene and its ozone formation potentials (OFPs) in Beijing were evaluated in the range of 0.49–3.46 ppbv and 6.4–44.7 ppbv, respectively, from April to October. OFP of the reacted isoprene accounted for 10.6–23.6% of the total OFPs of VOCs (including carbonyls and isoprene) and 6.38–29.9% of the photo-chemically produced ozone. The maximum OFP of the original emitted isoprene prior to its photo-oxidation was calculated as 56.0 ppbv in August. The contribution from the reacted isoprene in Beijing to HCHO formation was also estimated to be in the range of 0.35–2.45 ppbv from April to October, which accounted for 4.6–11.5% of ambient HCHO.     

A kinetic study on oxidation of pentachlorophenol by ozone

The kinetics of pentachlorophenol (PCP) ozonation in terms of the gaseous O3 and dissolved PCP concentrations has been investigated. When the O3 concentration in the gas phase was in the range of 10 to 40 g O3/m3, the O3 dissolved for a short time period was proportional to the gaseous O3 concentration. In this range, the ozonation reaction was first order for each reactant and the overall reaction was second order. At 25 degrees C, in an aqueous solution, the reaction rate constant was estimated to be 10.048 L/mol.sec. The reaction rate was much greater than the mass-transfer rate, indicating that the reaction of O3 and PCP was an interface reaction on the surface of gaseous O3 bubbles. The final product of the PCP ozonation was oxalic acid, with the carbon yield of the reaction being 59.4%. The ozonation of PCP in the aqueous solution was not a radical reaction but a direct reaction between O3 and PCP molecules under the conditions investigated in this study, since O3 has a high selectivity toward PCP. The reaction rate increased with the reaction temperature up to 35 degrees C but decreased at temperatures greater than 35 degrees C due to the decreased solubility of O3. The addition of H2O2 did not increase the reaction rate significantly.     

Estimated washout coefficients for sulphur dioxide,nitric oxide,nitrogen dioxide and ozone

The washout coefficient of a gas in air is the fraction of it removed in unit time by rain below cloud base. The ‘apparent’ coefficients were estimated by statistically comparing hourly ground-level concentrations just before and at the onset of heavy, non-frontal rain. The concentrations were obtained from 5 y of continuous monitoring at a rural site.The coefficient (s⁻¹) estimated for SO₂ was (2.61 ± 0.14) × 10⁻⁵ times the rate of rainfall (mm h ⁻¹). This is completely consistent with a previously published value derived from the data from 10 rural sites for one year, and both estimates are consistent with published values of dissolved SO₂ in rainwater at another rural site, giving some confidence in the technique.The values of the coefficients estimated for NO and NO₂ were about 40 and 80%, respectively of that for SO₂. Some nitrite is found in rainwater, but not enough to explain the washout found. However, the analysers used would measure HNO₃ aerosols as NO₂, and these are very soluble. In addition, fast reactions are known which can convert oxides of nitrogen into soluble nitrates, present in sufficient concentration in rainwater.The statistical process leads to the coefficient estimated for O₃ being negative, implying that O₃ is produced at the time of rain. This is most probably due to the strong winds and turbulence which accompany heavy rain, giving replenishment of low-level O₃ from upper air levels where O₃ is normally produced. No systematic changes in the other gas concentrations accompany the changes in O₃ values.     

The exchange of nitric oxide, nitrogen dioxide and ozone between pasture and the atmosphere

Fluxes of NO, NO2 and O3 were determined over a drained marshland pasture in south-east England by using flux-gradient techniques. Nitric oxide was found to be emitted at rates of up to 40 ng m(-2) s(-1), the rate of emission being related to the magnitude of the eddy diffusivity. Nitrogen dioxide deposited at rates of up to 90 ng m(-2) s(-1) under the control of stomatal resistance, a clear diurnal cycle being observed. Minimum canopy resistance was of the order of 80 s m(-1). Ozone deposition was also controlled by stomatal resistance, the minimum canopy resistance being around 100 s m(-1) and fluxes reaching a maximum of 220 ng m(-2) s(-1). Corrections made to NO and NO2 fluxes to compensate for chemical reactions showed flux divergences of the order of 30% for NO and NO2, but these were not statistically significantly different from the measured fluxes. The pasture was found to be a net sink for nitrogen in the form of NOx.     

Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions

This paper is particularly related to elemental mercury (Hg0) oxidation and divalent mercury (Hg2+) reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO2). As a powerful oxidant and chlorinating reagent, Cl2 has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO2, NO, as well as H2O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO2 and NO on Hg0 oxidation and Hg2+ reduction with the intent of unraveling unrecognized interactions among Cl species, SO2, and NO most importantly in the presence of H2O. The experimental results demonstrated that SO2 and NO had pronounced inhibitory effects on Hg0 oxidation at high temperatures when H2O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg2+ back into its elemental form. Data revealed that SO2 and NO were capable of promoting homogeneous reduction of Hg2+ to Hg0 with H2O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H2O was removed from the gas blend.     

Relationship between Pd oxidation states on TiO2 and the photocatalytic oxidation behaviors of nitric oxide

This study has been undertaken to investigate the relationship between Pd oxidation states on TiO₂ photocatalysts and their photocatalytic oxidation behaviors of NO. Three types of Pd-modified TiO₂ with different Pd oxidation states were prepared by wet impregnation method, neutralization method and photodeposition method, respectively. And these Pd-modified photocatalysts were characterized by X-ray diffraction analysis, X-ray photoelectron spectrum analysis (XPS), UV–Vis diffuse reflectance spectra and temperature programmed desorption (TPD). It was found from XPS results that the dominant oxidation states of Pd on these Pd-modified TiO₂ catalysts were Pd²⁺, PdO, and Pd⁰, respectively. NO-TPD results showed that the NO adsorption capacity was improved greatly by the modification of Pd²⁺ ions. The activity tests showed that Pd-modified TiO₂ by a wet impregnation method increased photocatalytic activity compared to pure TiO₂ (Degussa P25). It was concluded that Pd²⁺ ions on as-prepared TiO₂ catalysts provided key contributions to the improvement of photocatalytic activity. However, Pd⁰ and PdO deposits on TiO₂ almost had no positive effect on NO oxidation. The mechanism of photocatalytic oxidation of NO in gas phase over Pd-modified TiO₂ was also proposed.     

臭氧氧化降解含染料废水的研究

探讨了臭氧氧化技术处理染料 (酸性、直接、活性、分散和还原颜料 )模拟废水的影响因素———pH值、初始浓度和臭氧含量等对其的影响 ;臭氧氧化能提高染料废水的可生化性 ,可用来作为高浓度染料废水的预处理手段     

Photochemical ozone and nitric oxide formation in air-nitrogen dioxide mixtures containing sulfur dioxide or chlorine

Experiments were performed to investigate the effects of sulfur dioxide (0–10 ppm) and chlorine (0–15 ppm) on ozone and nitric oxide concentrations in irradiated mixtures of nitrogen dioxide (1–5 ppm) and air. The mixtures were irradiated by ultraviolet fluorescent lamps while flowing at a steady speed through a 9m long, 15.2cm i.d. Pyrex tube. The presence of sulfur dioxide produced no measurable change in the ozone and nitric oxide concentrations. The addition of small quantities of chlorine increased the ozone concentration in much the same manner as the addition of a hydrocarbon. A reaction model was developed for the chlorine-nitrogen dioxide-air mixtures. The observed increase in ozone concentration could only be predicted if the following two reactions were included : ClOO + NO → NO₂ + ClO and ClOO + NO → ClNO + O₂. Significant quantities of unexpected condensation nuclei were also observed in the chlorine-nitrogen dioxide-air mixtures.     

等离子体催化脱氮的实验研究

研究了等离子体和催化剂共同作用下氮氧化物的脱除情况 ,催化剂采用分子筛Cu ZSM 5。实验证明 ,在有催化剂存在的条件下 ,等离子体反应器的脱氮效率有了很大的提高 ,同时电源功率、烟气成分、温度、添加剂也都是影响实验结果的重要因素。     

Influence of ozone, relative humidity, and flow rate on the deposition and oxidation of sulfur dioxide on yellow sand

To evaluate the influences of O₃, relative humidity (RH), and flow rate on the reaction between yellow sand and SO₂, the SO₂ deposition velocity and the oxidation state of sulfur were investigated by means of exposure experiments in a cylindrical flow reactor. Early in the reaction, the deposition velocity was not influenced by the RH or the presence of O₃; as the reaction progressed, however, the deposition velocity increased in the presence of O₃ and at high humidity. The oxidation of sulfur from S(IV) to S(VI) was also enhanced under these conditions. The amount of sulfur oxidation was positively correlated with the amount of deposited O₃. Furthermore, the SO₂ deposition velocity increased with increasing flow rate. However, changes in the flow rate had no noticeable effect on the amount of SO₂ oxidation.     

Effects of airflow rate and plant species on formaldehyde removal by active green walls

Environmental Science and Pollution Research - Formaldehyde is a hazardous volatile organic compound (VOC) listed as a Group 1 carcinogen by the International Agency for Research on Cancer. The...     

Relationship between release of nitric oxide and CO2 and their dependence on oxidation reduction potential in wastewater treatment

Nitric oxide (NO) is an intermediate of denitrification process and can be produced by denitrifiers, nitrifiers and other bacteria. In our experiments we measured the dynamic flow of NO depending on oxidation reduction potential (ORP). Different ORP-ranges were related to various carbon loading stages in the wastewater treatment pilot plant. Nitrification and denitrification were achieved by a sequence of aeration and non-aeration periods. Our measurements show that different carbon loading conditions (low feed, balanced and overloaded conditions) did not change the range of the mixing ratio of NO emissions when the aeration conditions like air-flow and temperature were kept constant. Minimum and maximum NO mixing ratios were 34.7 and 91.8 ppbv; 52.3 and 91.3 ppbv; 57.6 and 109 ppbv for low feed, balanced and overloaded conditions, respectively. The curve of the NO graph relied on nitrification/denitrification dynamics. The dependence of NO release on different ORP and CO2-release during the various conditions are shown. Longer aeration times resulted in an increased release of gaseous NO. The net-release of NO g(-1) nitrogen removed was between 0.014% and 0.028%. The NO fluxes to the air were observed between 8.3 and 14.9 mg m(-2) d(-1) NO. The major release occurred during high aeration periods whereas the concentration of dissolved [NOaq] in the wastewater was less than 0.05% of the gaseous release due to very low solubility of the NO.     

The effects of meteorology on ozone in urban areas and their use in assessing ozone trends

The United States Environmental Protection Agency issues periodic reports that describe air quality trends in the US. For some pollutants, such as ozone, both observed and meteorologically adjusted trends are displayed. This paper describes an improved statistical methodology for meteorologically adjusting ozone trends as well as characterizes the relationships between individual meteorological parameters and ozone. A generalized linear model that accommodates the nonlinear effects of the meteorological variables was fit to data collected for 39 major eastern US urban areas. Overall, the model performs very well, yielding R² statistics as high as 0.80. The analysis confirms that ozone is generally increasing with increasing temperature and decreasing with increasing relative humidity. Examination of the spatial gradients of these responses show that the effect of temperature on ozone is most pronounced in the north while the opposite is true of relative humidity. By including HYSPLIT-derived transport wind direction and distance in the model, it is shown that the largest incremental impact of wind direction on ozone occurs along the periphery of the study domain, which encompasses major NO_x emission sources.     

应用臭氧氧化技术深度处理油船含油压载水的实验研究

油船含油压载水大量排放入海会对海洋生态环境产生较大的危害。在研究中,通过强电离放电技术制取高浓度臭氧,应用臭氧氧化方法来深度处理含油压载水,模拟实验表明在臭氧投加浓度达到120mg/L,在较短的接触时间(2min)内,臭氧对不同浓度的含油压载水中的油去除率可达到50%以上,同时使芳香族类物质显著减少,降低含油污水的生物毒性,处理方法具有可观的应用前景。     

Aqueous phase oxidation of sulfites by ozone in the presence of iron and manganese

The oxidation of sulfur^IVspecies by ozone in aqueous solution was studied at 295 K, with pH between 4 and 6, pO₃ between 0.3 and 2.0 ppm (v), S^IV between 5 × 10⁻⁶ and 1 × 10⁻⁶ M, and Fe and Mn between 1 × 10⁻⁴and 5 × 10⁻⁶ M. Throughout this range the oxidation rates were simultaneously first order in S^IV and pO₃, and in the absence of added Fe or Mn displayed a rate coefficient equal to 0.12 + 0.02 mm⁻¹ ppm (v)⁻¹. With added Fe or Mn at concentrations above 10⁻⁵ M the rate coefficients each show maxima near to pH 4.5 of 0.27± 05 × 10⁵M⁻¹ min⁻¹ ppm⁻¹and 0.68 ±.08 × 10⁵M⁻¹ min⁻¹ ppm⁻¹. respectively. Near this pH the rates were first order with respect to concentrations of the metal ions. A phosphate citrate buffer system at 10⁻⁴ M slows the Fe catalyzed oxidation. No non-additive effect of simultaneous catalysis by Fe and Mn was observed.     

臭氧催化氧化处理活性蓝染料废水及催化剂的研究

进行了臭氧化学氧化体系和臭氧催化氧化体系对活性蓝处理效果的比较。提出了常温常压下臭氧催化氧化预处理活性蓝染料废水的新方法。实验结果表明,臭氧催化氧化处理COD为13 800 mg/L的活性蓝染料废水时,最佳反应pH值为5～6,臭氧用量为80 mg/L时,反应时间约40 min,COD去除率大于80%,色度去除率大于90%,达到了预处理要求。