Ox Concentration Research Articles

Major air pollutants in Bursa, Turkey: their levels, temporal changes, interactions, and sources

Bursa is one of the largest cities of Turkey and it hosts 17 organized industrial zones. Parallel to the increase in population, rapidly growing energy consumption, and increased numbers of transport vehicles have impacts on the air quality of the city. In this study, regularly calibrated automatic samplers were employed to get the levels of air pollution in Bursa. The concentrations of CH4 and N-CH4 as well as the major air pollutants including PM10, PM2.5, NO, NO2, NOx, SO2, CO, and O3, were determined for 2016 and 2017 calendar years. Their levels were 1641.62 ± 718.25, 33.11 ± 5.45, 42.10 ± 10.09, 26.41 ± 9.01, 19.47 ± 16.51, 46.73 ± 16.56, 66.23 ± 32.265, 7.60 ± 3.43, 659.397 ± 192.73, and 51.92 ± 25.63 µg/m3 for 2016, respectively. Except for O3, seasonal concentrations were higher in winter and autumn for both years. O3, CO, and SO2 had never exceeded the limit values specified in the regulations yet PM10, PM2.5, and NO2 had violated the limits in some days. The ratios of CO/NOx, SO2/NOx, and PM2.5/PM10 were examined to characterize the emission sources. Generally, domestic and industrial emissions were dominated in the fall and winter seasons, yet traffic emissions were effective in spring and summer seasons. As a result of the correlation process between Ox and NOx, it was concluded that the most important source of Ox concentrations in winter was NOx and O3 was in summer.

Spectroscopic speciation of aqueous Am(iii)-oxalate complexes.

Transportation of actinides through the geosphere is facilitated by complexation with organic ligands dissolved in groundwater. Carboxylic groups can interact directly with actinide ions and are found among the most abundant organic ligands in alkaline aquatic systems like underground water. In this study, the complexation of organic carboxylic groups with Am(iii) was investigated by monitoring the interactions of Am(iii) with oxalate (Ox), the simplest dicarboxylate ligand, in solution. UV-Vis spectrophotometry coupled with a liquid waveguide capillary cell (100 cm optical path-length) and time-resolved laser fluorescence spectroscopy were employed for quantitative detection of the respective Am(iii)-Ox species. Increasing the Ox concentration caused significant spectral changes, i.e., red-shifts in both the absorption and luminescence maxima with increased molar absorption coefficients, enhanced luminescence intensities, and prolonged luminescence lifetimes. Individual spectra of AmOx+(aq), Am(Ox)2-(aq), and Am(Ox)33-(aq) were resolved by deconvolution of the absorption spectra, with apparent formation constants of log β1,1 = 5.34 ± 0.05, log β1,2 = 9.14 ± 0.18, and log β1,3 = 11.49 ± 0.30, respectively, in I = 0.1 M NaClO4 and 0-30 mM Na2Ox. The absorption and luminescence spectral changes suggest bidentate complexation of Ox with Am(iii) via inner-sphere interactions. The geometry of the Am(iii)-Ox complexes was optimized by density functional theory, where the bonding characteristics were in good agreement with the experimental results. Thorough spectroscopic characterization enabled speciation of the Am(iii)-Ox complexes and determination of their formation constants. This spectroscopic approach is generally applicable in the investigation of molecular interactions between Am(iii) and various ligands in aqueous solution.

Association of short-term exposure to fine particulate air pollution and mortality: effect modification by oxidant gases

Short term changes in exposure to outdoor fine particulate matter (PM2.5) concentrations are associated with an increased risk of mortality. However, less is known about how oxidant gases may modify the acute health effects of PM2.5. Our objective was to investigate whether associations between acute exposure to PM2.5 and mortality were modified by the oxidant gases O3 and NO2 using their redox-weighted average (Ox). We conducted a multi-city case-crossover study in 24 cities across Canada between 1998–2011 including 1,179,491 nonaccidental mortality events. Interquartile increases in lag-0 and 3-day mean PM2.5 and Ox concentrations were each associated with small increases in nonaccidental and cardiovascular mortality. In stratified analyses, associations between PM2.5 and nonaccidental and cardiovascular mortality tended to be greatest in the highest tertile of Ox with a significant interaction observed between lag 0 PM2.5 and 3-day mean Ox (interaction p-value = 0.04). There was no evidence of effect modification by Ox in the relationship between PM2.5 and respiratory mortality. Overall, the relationship between short-term changes in outdoor PM2.5 and nonaccidental mortality may be greater when oxidant gas concentrations are also elevated. In some regions, reductions in oxidant gas concentrations may also reduce the acute health impacts of PM2.5.

The enhanced effect of oxalic acid on the electroreduction of Cr(VI) via formation of intermediate Cr(VI)-oxalate complex

ABSTRACTIn this study, the enhanced effect of oxalic acid (Ox) on Cr(VI) electroreduction was evaluated. It was found that for Cr(VI)-contaminated solution ([Cr(VI)]0 = 1.0 mM, pH = 3.0), addition of 5.0 mM Ox can significantly increase Cr(VI) reduction from 0.36 to 1.0 mM within 90 min electrolysis reaction, accompanying with the increase of current efficiency from 19% to 53%. Increasing initial Ox concentration (0–10 mM) and electric current (10–40 mA) facilitated Cr(VI) reduction, whereas it was inhibited with decreasing solution pH value (2.0–3.5) and elevating Cr(VI) concentration (0.1–2.0 mM), respectively. Results show that reactive electron was the primary reductant for the heterogeneous reduction of Cr(VI) on the cathode. In addition, Ox can also serve as an electron donor for the homogeneous reduction of Cr(VI). During this process, the formation of Cr(VI)-oxalate complex is indispensable for the enhanced Cr(VI) reduction. The coordination of Ox with Cr(VI) did not only make the structure of Cr(VI) more distorted but also improved the reactivity of Cr(VI) in Cr(VI)-oxalate complex toward reduction reaction. In general, this study provides an energy-efficient and environmentally benign strategy for the treatment of Ox and Cr(VI) co-contaminated wastewater.

Comparisons of combined oxidant capacity and redox-weighted oxidant capacity in their association with increasing levels of FeNO

BackgroundSome ozone (O3) and nitrogen dioxides (NO2) health effects studies use Ox (sum value) as a surrogate. However, little is known about how this related to Oxwt (weighted value). ObjectiveWe investigated the effects of redox-weighted oxidant capacity (Oxwt) on fractional exhaled nitric oxide (FeNO), a biomarker of airway inflammation, in a set of chronic obstructive pulmonary disease (COPD) patients. We also compare combined oxidant capacity (Ox) and Oxwt in their associations with increasing levels of FeNO. MethodsWe measured FeNO values in 600 participants who have COPD at Shanghai Pulmonary Hospital. Ox was calculated directly by the sum of O3 and NO2. The redox-weighted oxidant capacity was calculated by denoting Oxwt as the weighted average of redox potentials. We applied generalized additive models (GAM) to investigate the impacts of Ox and Oxwt on FeNO levels, respectively. We fitted the same models for the influence of O3 and NO2 individually and jointly on FeNO levels to compare the result of Ox and Oxwt. ResultsOxwt were significantly linked with FeNO levels. The impact was robustest in current day after exposure, and were closely linked with the adjustment of PM2.5. A 10 μg m−3 increase in average Oxwt concentrations was linked to 0.88 (95% CI: −1.46, 3.28) increase, whereas a 10 μg m−3 increase in average Ox concentration was linked to 0.62 (95% CI: −0.79, 2.07) increase in FeNO. In two-pollutant models, an increase of 10 μg m−3 in average O3 concentrations with adjustment of NO2 was associated with 0.57 (95% CI: −1.26, 2.01) increase in FeNO. The impact estimates of Ox and Oxwt were statistically significant among males, non-smoking and elders who age above 65 years old. ConclusionsThis analysis demonstrated that Oxwt is used as a better indicator of atmospheric oxidative capacity as a proxy of O3 and NO2 in further epidemiological studies.

Influence of intense secondary aerosol formation and long-range transport on aerosol chemistry and properties in the Seoul Metropolitan Area during spring time: results from KORUS-AQ

Abstract. Non-refractory submicrometer particulate matter (NR-PM1) was measured in the Seoul Metropolitan Area (SMA), Korea, using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) from 14 April to 15 June 2016, as a part of the Korea-US Air Quality Study (KORUS-AQ) campaign. This was the first highly time-resolved, real-time measurement study of springtime aerosol in SMA and the results reveal valuable insights into the sources and atmospheric processes that contribute to PM pollution in this region. The average concentration of submicrometer aerosol (PM1 = NR-PM1 + black carbon (BC)) was 22.1 µg m−3, which was composed of 44 % organics, 20 % sulfate, 17 % nitrate, 12 % ammonium, and 7 % BC. Organics had an average atomic oxygen-to-carbon (O ∕ C) ratio of 0.49 and an average organic mass-to-carbon (OM/OC) ratio of 1.82. Four distinct sources of OA were identified via positive matrix factorization (PMF) analysis of the HR-ToF-AMS data: vehicle emissions represented by a hydrocarbon-like OA factor (HOA; O ∕ C = 0.15; 17 % of OA mass), food cooking activities represented by a cooking-influenced OA factor (COA; O ∕ C = 0.19; 22 % of OA mass), and secondary organic aerosol (SOA) represented by a semi-volatile oxygenated OA factor (SV-OOA; O ∕ C = 0.44; 27 % of OA mass) and a low-volatility oxygenated OA factor (LV-OOA; O ∕ C = 0.91; 34 % of OA mass). Our results indicate that air quality in SMA during KORUS-AQ was influenced strongly by secondary aerosol formation, with sulfate, nitrate, ammonium, SV-OOA, and LV-OOA together accounting for 76 % of the PM1 mass. In particular, the formation of LV-OOA and sulfate was mainly promoted by elevated ozone concentrations and photochemical reactions during daytime, whereas SV-OOA and nitrate formation was contributed by both nocturnal processing of VOC and nitrogen oxides, respectively, and daytime photochemical reactions. In addition, lower nighttime temperature promoted gas-to-particle partitioning of semivolatile species and formation of SV-OOA and nitrate. During a period of 4 days (from 20 to 23 May ), LV-OOA increased dramatically and accounted for up to 41 % of the PM1 mass. This intense LV-OOA formation event was associated with large enhancements of both anthropogenic and biogenic VOCs (e.g., isoprene and toluene), high concentration of Ox ( = O3 + NO2), strong solar radiation, and stagnant conditions, suggesting that it was mainly driven by local photochemical formation. We have also investigated the formation and evolution mechanisms of severe haze episodes. Unlike the winter haze events which were mainly caused by intense local emissions coupled with stagnant meteorological conditions, the spring haze events appeared to be influenced by both regional and local factors. For example, there were episodes of long-range transport of plumes followed by calm meteorology conditions, which promoted the formation and accumulation of local secondary species, leading to high concentrations of PM. Overall, our results indicate that PM pollutants in urban Korea originate from complex emission sources and atmospheric processes and that the concentrations and composition of PM are controlled by various factors, including meteorological conditions, local anthropogenic emissions, and upwind sources.

Phenomenology of summer ozone episodes over the Madrid Metropolitan Area, central Spain

Abstract. Various studies have reported that the photochemical nucleation of new ultrafine particles (UFPs) in urban environments within high insolation regions occurs simultaneously with high ground ozone (O3) levels. In this work, we evaluate the atmospheric dynamics leading to summer O3 episodes in the Madrid air basin (central Iberia) by means of measuring a 3-D distribution of concentrations for both pollutants. To this end, we obtained vertical profiles (up to 1200 m above ground level) using tethered balloons and miniaturised instrumentation at a suburban site located to the SW of the Madrid Metropolitan Area (MMA), the Majadahonda site (MJDH), in July 2016. Simultaneously, measurements of an extensive number of air quality and meteorological parameters were carried out at three supersites across the MMA. Furthermore, data from O3 soundings and daily radio soundings were also used to interpret atmospheric dynamics. The results demonstrate the concatenation of venting and accumulation episodes, with relative lows (venting) and peaks (accumulation) in O3 surface levels. Regardless of the episode type, the fumigation of high-altitude O3 (arising from a variety of origins) contributes the major proportion of surface O3 concentrations. Accumulation episodes are characterised by a relatively thinner planetary boundary layer (< 1500 m at midday, lower in altitude than the orographic features), light synoptic winds, and the development of mountain breezes along the slopes of the Guadarrama Mountain Range (located W and NW of the MMA, with a maximum elevation of > 2400 m a.s.l.). This orographic–meteorological setting causes the vertical recirculation of air masses and enrichment of O3 in the lower tropospheric layers. When the highly polluted urban plume from Madrid is affected by these dynamics, the highest Ox (O3+ NO2) concentrations are recorded in the MMA. Vertical O3 profiles during venting episodes, with strong synoptic winds and a deepening of the planetary boundary layer reaching > 2000 m a.s.l., were characterised by an upward gradient in O3 levels, whereas a reverse situation with O3 concentration maxima at lower levels was found during the accumulation episodes due to local and/or regional production. The two contributions to O3 surface levels (fumigation from high-altitude strata, a high O3 background, and/or regional production) require very different approaches for policy actions. In contrast to O3 vertical top-down transfer, UFPs are formed in the planetary boundary layer (PBL) and are transferred upwards progressively with the increase in PBL growth.

Association between daily ambient air pollution and respiratory symptoms in children with asthma and healthy children in western Japan

ABSTRACTObjective: In recent years, air pollutant concentrations in Japan have decreased slightly; however, there are growing concerns about the influences of transnational air pollution on respiratory illness. We aimed to clarify the short-term association between the ambient air pollution and respiratory symptoms among children without asthma, children with asthma not using long-term medications (CA-nonLTM), and those using them (CA-LTM). Methods: A total of 138 children attending 2 primary schools and 71 children with asthma regularly visiting cooperating medical institutions were recruited. Study participants measured peak expiratory flow (PEF) twice a day and recorded coughing, nasal symptoms, and medication use in a diary. Predicted associations between daily air pollutant concentrations and respiratory symptoms, and PEF were evaluated using case-crossover and generalized estimate equation models. Results: Changes in %maxPEF per 10 ppb oxidant (Ox) increase in children without asthma, CA-nonLTM, and CA-LTM were −0.26% (95% CI: −0.49, −0.03), −0.51% (95% CI: −0.89, −0.12), and −0.20% (95% CI: −0.42, 0.01), respectively. The odds ratios for coughing per 10 ppb Ox increase in the Lag0 model were 1.34 (95% CI: 1.11, 1.60), 1.52 (95% CI: 1.12, 2.07), and 1.06 (95% CI: 0.93, 1.20), respectively. These suggested that the Ox concentration has graded effects on %maxPEF and coughing, in the following descending order, CA-nonLTM, children without asthma, and CA-LTM. The Ox concentration was also positively associated with nasal symptoms in children without asthma and CA-LTM. Conclusion: Our results suggest that using long-term medications to manage asthma may play an important role in preventing exacerbation of respiratory symptoms due to air pollution.

Impact of Oxidant Gases on the Relationship between Outdoor Fine Particulate Air Pollution and Nonaccidental, Cardiovascular, and Respiratory Mortality

Outdoor fine particulate air pollution (PM2.5) is known to increase mortality risk and is recognized as an important contributor to global disease burden. However, less is known about how oxidant gases may modify the chronic health effects of PM2.5. In this study, we examined how the oxidant capacity of O3 and NO2 (using a redox-weighted average, Ox) may modify the relationship between PM2.5 and mortality in the 2001 Canadian Census Health and Environment Cohort. In total, 2,448,500 people were followed over a 10.6-year period. Each 3.86 µg/m3 increase in PM2.5 was associated with nonaccidental (Hazard Ratio (HR) = 1.095, 95% CI: 1.077, 1.112), cardiovascular (HR = 1.088, 95% CI: 1.059, 1.118), and respiratory mortality (HR = 1.110, 95% CI: 1.051, 1.171) in the highest tertile of Ox whereas weaker/null associations were observed in the middle and lower tertiles. Analysis of joint non-linear concentration-response relationships for PM2.5 and Ox suggested threshold concentrations between approximately 23 and 25 ppb with Ox concentrations above these values strengthening PM2.5-mortality associations. Overall, our findings suggest that oxidant gases enhance the chronic health risks of PM2.5. In some areas, reductions in Ox concentrations may have the added benefit of reducing the public health impacts of PM2.5 even if mass concentrations remain unchanged.

Alteration of exosomes secreted from renal tubular epithelial cells exposed to high-concentration oxalate.

Oxalate (Ox) is a metabolic end product that is produced by the kidneys and is associated with several pathological conditions. The accumulation of oxalate in the body is one of the factors that lead to calcium oxalate kidney stones. To simulate the high-concentration Ox environment in vivo, we established an in vitro model of high Ox using renal tubular epithelial (HK-2) cells. Cell viability and proliferation were assessed to evaluate the effects of various concentrations (0, 0.25, 0.5, 1, 2, 4, 5, 8 and 10Mm) of Ox on HK-2 cells to select the optimum concentration and time to extract the exosomes. Treatment with 0, 1, or 2 mM Ox altered the morphology and secretion capacity of exosomes. As the concentration of Ox increased, peak and mean particle size decreased, but exosomes particle concentration, exosome RNA, and exosome protein increased. Size, distribution, and rate of secretion, as well as RNA and protein content, differed among extracellular vesicle subtypes. Furthermore, the three subtypes of exosomes delivered different signal factors in the microenvironment. We therefore speculated that three subtypes of exosomes may play differing roles in intercellular signal communication and the formation of CaOx kidney stones.

Evaluation of the photooxidation efficiency of As(III) applying the UVC/oxalate technique

In this study, the photooxidation capacity of UVC/Oxalate (Ox) was evaluated using As(III) as a typical pollutant. The results show that the direct oxidation amount of As(III) induced by UVC in water was negligible, but the presence of Ox remarkably accelerated the oxidation rate of As(III). Under UVC irradiation, 50 μM As(III) can be completely oxidized to As(V) in the case of Ox concentration above 300 μM within 60 min. As(III) oxidation was found greatly related with the photodecomposition of Ox. Much more Ox can be mineralized in more acidic solution. At the same time, the photooxidation of As(III) was significantly favored at decreased initial pH from 8.0 to 3.0. In this reaction system, the role of oxygen was indispensable for Ox photodecomposition and As(III) photooxidation, which can be ascribed to its special roles as a precursor of reactive superoxide and an electron acceptor. In oxygen-present atmosphere, the in situ production of H2O2 was detected during the photolysis of Ox and its photolysis product, i.e., OH primarily contributed to the oxidation of As(III). However, the photodecomposition of Ox and photooxidation of As(III) were significantly inhibited in the anaerobic environment. In general, the homogeneous photolysis of Ox in many commonly practiced UVC oxidation processes can be also proposed as a supplementary method of generating highly oxiditive species in aerobic condition.

New System for Measuring the Photochemical Ozone Production Rate in the Atmosphere.

We have developed a new system for measuring photochemical ozone production rates in the atmosphere. Specifically, the system measures the net photochemical oxidant (Ox: the sum of ozone (O3) and nitrogen dioxide (NO2)) production rates (P-L(Ox)). Measuring Ox avoids issues from perturbations to the photostationary states between nitrogen oxides (NOx) and O3. This system has "reaction" and "reference" chambers. Ambient air is introduced into both chambers, and Ox is photochemically produced in the reaction chamber and not generated in the reference chamber. Air from the chambers is alternately introduced into an NO-reaction (NO: nitric oxide) tube to convert O3 to NO2, and then the Ox concentration is measured as NO2 using a laser-induced fluorescence technique. P-L(Ox) was obtained by dividing the difference in Ox concentrations between air samples from the two chambers by the mean residence time of the air in the reaction chamber. In this study, the P-L(Ox) measurement system was characterized, and the current detection limit of P-L(Ox) was determined to be 0.54 ppbv h-1 with an integration time of 60 s (S/N = 2), assuming an ambient Ox concentration of 100 ppbv. Field measurements of P-L(Ox) were conducted using the system at a remote forest location.

Observation of regional air pollutant transport between the megacity Beijing and the North China Plain

Abstract. Megacities have strong interactions with the surrounding regions through transport of air pollutants. It has been frequently addressed that the air quality of Beijing is influenced by the influx of air pollutants from the North China Plain (NCP). Estimations of air pollutant cross-boundary transport between Beijing and the NCP are important for air quality management. However, evaluation of cross-boundary transport using long-term observations is very limited. Using the observational results of the gaseous pollutants SO2, NO, NO2, O3, and CO from August 2006 to October 2008 at the Yufa site, a cross-boundary site between the megacity Beijing and the NCP, together with meteorological parameters, we explored a method for evaluating the transport flux intensities at Yufa, as part of the “Campaign of Air Quality Research in Beijing and Surrounding Region 2006–2008” (CAREBeijing 2006–2008). The hourly mean ± SD (median) concentration of SO2, NO, NO2, NOx, O3, Ox, and CO was 15 ± 16 (9) ppb, 12 ± 25 (3) ppb, 24 ± 19 (20) ppb, 36 ± 39 (23) ppb, 28 ± 27 (21) ppb, 52 ± 24 (45) ppb, and 1.6 ± 1.4 (1.2) ppm during the observation period, respectively. The bivariate polar plots showed the dependence of pollutant concentrations on both wind speed and wind direction, and thus inferred their dominant transport directions. Surface flux intensity calculations further demonstrated the regional transport influence of Beijing and the NCP on Yufa. The net surface transport flux intensity (mean ± SD) of SO2, NO, NO2, NOx, O3, Ox, and CO was 6.2 ± 89.5, −4.3 ± 29.5, −0.6 ± 72.3, −4.9 ± 93.0, 14.7 ± 187.8, 14.8 ± 234.9, and 70 ± 2830 µg s−1 m−2 during the observation period, respectively. For SO2, CO, O3, and Ox the surface flux intensities from the NCP to Yufa surpassed those from Beijing to Yufa in all seasons except winter, with the strongest net fluxes largely in summer, which were about 4–8 times those of other seasons. The surface transport flux intensity of NOx from Beijing to Yufa was stronger than that from the NCP to Yufa except in summer, with the strongest net flux in winter, which was about 1.3–8 times that of other seasons. The flux intensities were then assigned to the corresponding trajectories in the potential source contribution function analysis (PSCF), which confirmed the results of flux intensity calculations. Our study also suggested that various factors, such as the wind field, emission inventory, and photochemical reactions, could influence transport of air pollutants. The decrease of surface flux intensity during the Olympic Games implied the role of both local emission reduction and regional cooperation in successful air quality management. Three dimensional observations are needed for further comprehensive discussion of the regional transport between Beijing and the NCP.

Investigating the evolution of summertime secondary atmospheric pollutants in urban Beijing

Understanding the formation of tropospheric ozone (O3) and secondary particulates is essential for controlling secondary pollution in megacities. Intensive observations were conducted to investigate the evolution of O3, nitrate (NO3−), sulfate (SO42−) and oxygenated organic aerosols ((OOAs), a proxy for secondary organic aerosols) and the interactions between O3, NOx oxidation products (NOz) and OOA in urban Beijing in August 2012. The O3 concentrations exhibited similar variations at both the urban and urban background sites in Beijing. Regarding the O3 profile, the O3 concentrations increased with increasing altitude. The peaks in O3 on the days exceeding the 1h or 8h O3 standards (polluted days) were substantially wider than those on normal days. Significant increases in the NOz mixing ratio (i.e., NOy - NOx) were observed between the morning and early afternoon, which were consistent with the increasing oxidant level. A discernable NO3− peak was also observed in the morning on the polluted days, and this peak was attributed to vertical mixing and strong photochemical production. In addition, a SO42− peak at 18:00 was likely caused by a combination of local generation and regional transport. The OOA concentration cycle exhibited two peaks at approximately 10:00 and 19:00. The OOA concentrations were correlated well with SO42− ([OOA]=0.55×[SO42−]+2.1, r2=0.69) because they both originated from secondary transformations that were dependent on the ambient oxidization level and relative humidity. However, the slope between OOA and SO42− was only 0.35, which was smaller than the slope observed for all of the OOA and SO42− data, when the RH ranged from 40 to 50%. In addition, a photochemical episode was selected for analysis. The results showed that regional transport played an important role in the evolution of the investigated secondary pollutants. The measured OOA and Ox concentrations were well correlated at the daily scale, whereas the hourly OOA and Ox concentrations were insignificantly correlated in urban Beijing. The synoptic situation and the differences in the VOC oxidation contributing to O3 and SOAs may have resulted in the differences among the correlations between OOA and Ox at different time scale. We calculated OOA production rates using the photochemical age (defined as –log10(NOx/NOy)) in urban plumes. The CO-normalized OOA concentration increased with increasing photochemical age, with production rates ranging from 1.1 to 8.5μgm−3ppm−1h−1 for the plume from the NCP.

Comprehensive morpho-constitutional analysis of urinary stones improves etiological diagnosis and therapeutic strategy of nephrolithiasis

The generalized use of physical methods, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) decisively improved urinary stone analysis by allowing to accurately identify the chemical nature, crystalline phases and relative proportions of stone constituents. Such compositional analysis is sufficient to identify stone diseases involving a single specific component such as cystine, 2,8-dihydroxyadenine (DHA), struvite, uric acid, ammonium hydrogen urate or a drug. However, for common calcium nephrolithiasis, which represents by far the largest part of urinary stones throughout the world, the simple identification of calcium oxalate (CaOx) and/or calcium phosphate (CaP) as constituents provides incomplete etiologic information because a same elemental stone composition may result from different lithogenic processes. A more comprehensive method combining careful morphologic examination of the surface and the section of stones with detailed FTIR analysis of the nature, location, crystalline phases and a respective proportion of stone constituents, therefore termed ‘morpho-constitutional’ analysis, as used in our laboratory for four decades provides more complete etiologic information. In common idiopathic CaOx nephrolithiasis, the predominance of the monohydrate form (COM) was shown to be associated with elevated urine Ox concentration, whereas the dihydrate form (COD) was associated with hypercalciuria, thus orienting dietary and/or pharmacological intervention. A major contribution of the method is to immediately orient the diagnosis of rare, but severe, diseases leading to a loss of renal function, when stone analysis reveals a peculiar morphology of common constituents. The most salient examples are the type Ic morphology of COM stones, pathognomonic of primary hyperoxaluria, type Ie morphology, which is highly suggestive of absorptive hyperoxaluria as seen in inflammatory bowel diseases and pathologies inducing steatorrhea, type IIId morphology of ammonium urate stones, which orientates towards chronic diarrhea with dietary imbalance and loss of electrolytes, and type IVa2 morphology of carbapatite, specific of distal renal tubular acidosis of congenital or acquired origin, and distinctive aspect of 2,8-DHA stones. In conclusion, the proposed morpho-constitutional method should be recommended for routine stone analysis, inasmuch as it is simple, rapid, reliable, clinically relevant and cost-effective.

Oxalate-assisted oxidative degradation of 4-chlorophenol in a bimetallic, zero-valent iron-aluminum/air/water system.

The reaction of zero-valent iron and aluminum with oxygen produced reactive oxidants that can oxidize 4-chlorophenol (4-CP). However, oxidant yield without metal surface cleaning to dissolve the native oxide layer or in the absence of ligands was too low for practical applications. The addition of oxalate (ox) to dissolved oxygen-saturated solution of Fe(0)-Al(0) significantly increased oxidant yield because of the dissolution, pH buffer, and complexing characteristics of ox. Ox-enhanced reactive oxidant generation was affected by ox concentration and solution pH. The critical effect of ox dosing was confirmed with the reactive species of [Fe(II)(ox)0] and [Fe(II)(ox)2 (2-)]. Systematic studies on the effect of the initial and in situ solution pH revealed that 4-CP oxidation was controlled by the continuous release of dissolved Fe(2+) and Al(3+), their fate, and the activation mechanisms of O2 reduction. The degradation pathway of 4-CP in ox-enhanced Fe(0)-Al(0)/O2 may follow the 4-chlorocatechol pathway. The robustness of the ox-enhanced Al(0)-Fe(0)-O2 process was determined with one-time dosing of ox. Therefore, ox is an ideal additive to enhancing the Fe(0)-Al(0)/O2 system for the oxidative degradation of aqueous organic pollutants.

Temporal persistence of intra-urban spatial contrasts in ambient NO2, O3 and Ox in Edinburgh, UK

Ambient NO2, O3 and Ox (the sum of NO2 and O3) are associated with adverse health outcomes. Quantitative assessment of the health burden from these pollutants requires knowledge of small-scale variations in their concentrations in urban environments. In particular, we were interested in the temporal stability of intra-urban spatial contrasts in these pollutants. This was investigated by concurrent measurements of NO2 and O3 by passive samplers at 30 sites in Edinburgh, UK, repeated 12 × 1-weekly for NO2 and 6 × 2-weekly for O3 in summer and winter. Temporally persistent and large spatial variations in both NO2 and O3 concentrations were observed. Concentrations of NO2 across the sites ranged on average by a factor of 14 between suburban parks and heavily-trafficked roadsides, corresponding to a difference in NO2 on average of ∼80 μg m−3. Intra-urban O3 concentrations also varied substantially, on average by a factor of 4 (average range 45 μg m−3) and with strong anticorrelation to NO2 concentrations across the 30 sites. Consequently intra-urban variability was considerably lower for Ox than for NO2 and O3. The temporal stability in relative NO2 and O3 concentrations indicate potential for deriving intra-urban spatial fields of NO2 and O3 at different times by scaling models of long-term spatial patterns of NO2 and O3 by the measurements at a single site. If Ox is a key determinant of adverse health then the large intra-urban spatial contrasts in NO2 and O3 may be less relevant, with Ox concentrations across an urban area determined at a suitable background site.

Photo-Fenton degradation of the herbicide 2,4-D in aqueous medium at pH conditions close to neutrality

A theoretical and experimental study of the photo-Fenton degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in water is presented. A kinetic model derived from a reaction sequence is proposed using the ferrioxalate complex as iron source for conditions of pH = 5. The kinetic model was employed to predict the concentrations of 2,4-D, 2,4-dichlorophenol (2,4-DCP), hydrogen peroxide (HP) and oxalate (Ox) in a flat plate laboratory reactor irradiated with a solar simulator. Two types of incident irradiation levels were tested by different combinations of attenuation filters. The effects of the oxalate/Fe+3 molar ratio (Ox/Fe), the reaction temperature (T) and the 2,4-D/HP molar ratio (R) on the photo-Fenton process were also investigated. For low radiation level and operating conditions of R = 50 and T = 50 °C, a 2,4-D conversion of 95.6% was obtained after 180 min. Moreover, the 2,4-D conversion was almost 100% in only 120 min when the system was operated under the same operating conditions and high radiation level. From the proposed model and the experimental data, the corresponding kinetic parameters were estimated applying a nonlinear regression method. A good agreement between the kinetic model and experimental data, for a wide range of simulated solar operating conditions, was observed. For 2,4-D, 2,4-DCP, HP and Ox concentrations, the calculated RMSE were 1.21 × 10−2, 5.45 × 10−3, 2.86 × 10−1 and 2.65 × 10−2 mM, respectively.

Examining the major contributors of ozone pollution in a rural area of the Yangtze River Delta region during harvest season

Abstract. Open biomass burning (OBB) emits significant amounts of non-methane hydrocarbons (NMHCs), and the mixing of OBB with urban plumes could exacerbate regional ozone (O3) pollution. In the present study, an observational field campaign was performed in a rural area at the northern edge of the Yangtze River Delta region (YRDR) from 15 May to 24 June 2010, during intensive open burning of wheat residues. The net photochemical production rate of oxidant (Ox = O3 + NO2) at the site was evaluated based on a box model (Regional Atmospheric Chemical Mechanism, Version 2) constrained by real-time ambient measurements (e.g., O3, volatile organic compounds (VOCs), NOx (NO2 + NO), J values). Our results showed that both in situ photochemistry and direct transport from urban areas in the YRDR were responsible for the high Ox concentration at the site. During an OBB-impact case, net photochemical production of Ox in the daytime was pronounced, with a 6 h averaged Ox production rate of 13 ± 4 ppbv h−1 (maximum value of 21 ppbv h−1 at 12:00 CST). Photochemical Oxproduction changed from VOC-limited in the morning to NOx-limited in the afternoon due to the rapid photochemical consumption of NOx during the day. A combined analysis with positive matrix factorization demonstrated that O3 pollution in the rural area of the YRDR was largely affected by urban emission, and OBB-related emissions also contributed to in situ photochemical production, particularly in the afternoon. Our study suggested that a joint effort in reducing both NMHCs (e.g., aromatics) and NOx emissions in the urban area, as well as local OBB activities, may be effective in eliminating high-O3 pollution risk in the rural areas of the YRDR.

Investigation into relationships among NO, NO2, NOx, O3, and CO at an urban background site in Delhi, India

High resolution concentrations of nitric oxide (NO), nitrogen dioxide (NO2), oxides of nitrogen (NOx), and Ozone (O3) were measured at a urban site (urban background) in New Delhi, India for a period of two years from September 2010 to August 2012. During the study period, the mean concentrations of NO, NO2, NOx, O3 (ppb), and CO (ppm) were observed to be 17.2, 12.5, 29.3, 23.6, and 1.97, respectively. This data was then employed to investigate the relationships between NO, NO2, and O3 as a function of NOx. The highest mean concentrations of NO were observed from midnight 00:00 to 05:00h local time (LT) in the morning as a result of an increase in traffic emissions and a reduction in boundary layer height during the night. The total levels of oxidant [OX], which are considered to be the sum of O3 and NO2, were determined. A study of variation of [OX] and NOx identified two distinct contributions to ambient OX concentrations, i.e., NOx independent and NOx dependent. The NOx-dependent contribution corresponds to the local production of ozone, and the NOx-independent contribution corresponds to regional concentrations, which at this site is the background level of ozone. The monthly and diurnal variations of [OX] are discussed. Wind directions were used to identify possible regional sources of [OX]. The analysis suggests that [OX] concentrations were about six times higher with winds originating from the Northwest direction (NW) compared to those from the East.