Gas-Phase Kinetic Investigation of the OH-Initiated Oxidation of a Series of Methyl-Butenols under Simulated Atmospheric Conditions.

Five biogenic unsaturated alcohols have been investigated under simulated atmospheric conditions regarding their gas-phase OH reactivity. The gas-phase rate coefficients of OH radicals with 2-methyl-3-buten-2-ol (k1), 3-methyl-2-buten-1-ol (k2), 3-methyl-3-buten-1-ol (k3), 2-methyl-3-buten-1-ol (k4), and 3-methyl-3-buten-2-ol (k5) at 298 ± 2 K and 1000 ± 10 mbar total pressure of synthetic air were determined under low- and high-NOx conditions using the relative kinetic technique. The present work provides for the first time the rate coefficients of gas-phase reactions of hydroxyl radicals with 2-methyl-3-buten-1-ol and 3-methyl-3-buten-2-ol. The following rate constants were measured (in 10-11 cm3 molecule-1 s-1): k1 = 6.32 ± 0.49, k2 = 14.55 ± 0.93, k3 = 10.04 ± 0.78, k4 = 5.31 ± 0.37, and k5 = 11.71 ± 1.29. No significant differences in the measured rate coefficients were obtained when either 365 nm photolysis of CH3ONO in the presence of NO or 254 nm photolysis of H2O2 was used as a source of OH radicals. Reactivity toward other classes of related compounds such as alkenes and saturated alcohols is discussed. A comparison of the structure-activity relationship (SAR) estimates derived from the available accepted methodologies with experimental data available for unsaturated alcohols is provided. Atmospheric lifetimes for the investigated series of alkenols with respect to the main atmospheric oxidants are given and discussed.

Offline analysis of secondary formation markers in ambient organic aerosols by liquid chromatography coupled with time-of-flight mass spectrometry.

The present study provides a comprehensive assessment of the quantitative analysis by high-performance liquid chromatography coupled with dual orthogonal electrospray ionization time-of-flight mass spectrometry (HPLC-ESI-TOF-MS) of pinene markers, biomass-burning related phenols, and other relevant carboxylic acids in atmospheric aerosol samples. Significant insights into the quantitative determination are offered on the basis of systematic experiments targeting the optimization of chromatographic separation, ionization source, and mass spectrometer performance. After testing three analytical columns, the best separation of the compounds of interest was achieved on a Poroshell 120 ECC18 column (4.6 × 50 mm, 2.7 µm) thermostated at 35 °C, operating in gradient elution mode with 0.1% acetic acid in water and acetonitrile at a 0.8 mL min-1 flow rate. Optimal operational conditions for the ESI-TOF-MS instrument were identified as a 350 °C drying gas temperature, 13 L min-1 drying gas flow rate, 60 psig nebulizer pressure, 3000 V for the ion transfer capillary, 60 V for the skimmer, and 150 V for the fragmentor. Additionally, the matrix effect on the ESI efficiency and the spike recovery factors of the compounds were tested. Method quantification limits can go as low as in the 0.88-48.0 µg L - 1 (3.67-200 pg m - 3, at 120 m3 of sampled air) range. The developed method was shown to be reliable for the quantification of the targeted compounds in real atmospheric aerosol samples. The accuracy in the molecular mass determination of less than 5 ppm and the acquisition in the full scan mode were shown to bring additional insights into the organic constituents in atmospheric aerosols.

First insights into the molecular characteristics of atmospheric organic aerosols from Iasi, Romania: Behavior of biogenic versus anthropogenic contributions and potential implications.

The present study reports first data on the organic molecular composition and evolution of secondary organic aerosols (SOAs) markers in aerosol samples from an urban environment in Romania. Targeted and non-targeted approaches of liquid chromatography tandem with time-of-flight mass spectrometry (LC-ToF-MS) were used as powerful analytical approaches for aerosol characterization at the molecular level. Four distinct organic molecular groups (CHO, CHON, CHONS, and CHOS) were classified as relevant for both warm (with 847 assigned molecular formulae) and cold (with 432 assigned molecular formulae) periods. Different formation mechanisms, physico-chemical processing, meteorological conditions, and sources origin or strengths (biogenic versus anthropogenic), were identified as governing factors of the mass concentration size distribution for the first generation and second-generation oxidation products of α-/ß-pinene and two nitroaromatics (i.e., 4-nitrophenol and 4-nitrocatechol). Aromaticity equivalent (XC), carbon oxidation state (OSC), H/C and O/C ratios, and van Krevelen diagrams, were used to discriminate between: i) the aliphatic or aromatic nature of the identified organic aerosol constituents, ii) the oxidation state of the aerosol samples (e.g., more oxidized molecular formulae during the highly insolated period, more intense photochemistry), and iii) sources role in controlling OAs constituents abundances and behavior (e.g., higher relative contributions of aliphatic CHO formulae with a wider range of carbon numbers and CHOS molecular group with higher contribution during the warm period due to increased biogenic emissions or secondary formation from the biogenic precursors). Since in the present study >88 % of the 4-nitrocatechol and 4-nitrophenol was determined in the aerosol size fraction below 1 µm, it is believed that determination of their abundances and size distribution in ambient aerosols might provide direction for future studies such as to enhance the knowledge on their toxic potential levels for the human health.

Evaluation of the Environmental Fate of a Semivolatile Transformation Product of Ibuprofen Based on a Simple Two-Media Fate Model.

Partitioning between surface waters and the atmosphere is an important process, influencing the fate and transport of semi-volatile contaminants. In this work, a simple methodology that combines experimental data and modeling was used to investigate the degradation of a semi-volatile pollutant in a two-phase system (surface water + atmosphere). 4-Isobutylacetophenone (IBAP) was chosen as a model contaminant; IBAP is a toxic transformation product of the non-steroidal, anti-inflammatory drug ibuprofen. Here, we show that the atmospheric behavior of IBAP would mainly be characterized by reaction with •OH radicals, while degradation initiated by •NO3 or direct photolysis would be negligible. The present study underlines that the gas-phase reactivity of IBAP with •OH is faster, compared to the likely kinetics of volatilization from aqueous systems. Therefore, it might prove very difficult to detect gas-phase IBAP. Nevertheless, up to 60% of IBAP occurring in a deep and dissolved organic carbon-rich water body might be eliminated via volatilization and subsequent reaction with gas-phase •OH. The present study suggests that the gas-phase chemistry of semi-volatile organic compounds which, like IBAP, initially occur in natural water bodies in contact with the atmosphere is potentially very important in some environmental conditions.

Development and application of an analysis method for the determination of rare earth elements in silicate-rich samples by Na2O2 sintering and ICP-MS analysis.

The performance of a fast and simple analytical procedure for rare earth elements (REEs) quantification from secondary sources was investigated in the present work. Seven silicate-rich certified reference materials (CRMs) in the form of Andesite (JA-1), Basalt (JB-3), Rhyolite (JR-1, JR-2), Granite (JG-2), Granodiorite (JG-3), and Till (TILL-1), were used for the optimization and characterization of the analysis method. The optimized method was used in the analysis of nine mining wastes selected within the ENVIREE project, under the ERA-MIN Program of the 7th Framework, having as the main aim to ensure a policy securing long-term access of REEs secondary sources at reasonable costs. For silicate-rich samples efficient solid dissolution involves sintering with Na2O2 at 460 °C and a sample to oxidizing reagent ratio of 1:6.5. Inductively coupled plasma-mass spectrometry (ICP-MS) was used in the quantification of the REEs with aerosol dilution of samples applied to minimize the salt effect on the plasma and interface regions. The work performed in the present study clearly shows that accurate reports on the REE concentrations from geological matrices also involves as mandatory the estimation of the overall uncertainty from various sources (sample preparation or analyte measurements). In the analysis of geological samples, the proposed analysis method has on average 23% of the overall uncertainty explained by the sample preparation and 77% accounted by the analysis steps. Moreover, the method described by effective, cheap, robust and safe attributes, can be recommended as an accessible alternative to the HF wet digestion method. Although from all the investigated tailings samples, only those from Sweden and Czech Republic can be regarded as potential secondary sources for REEs, investigation of other resources with interest at European level might bring a great benefit in the general attempt to develop an economically viable method for the production of rare earth elements.

Gas-Phase Ozone Reaction Kinetics of C5-C8 Unsaturated Alcohols of Biogenic Interest.

Unsaturated alcohols are volatile organic compounds (VOCs) that characterize the emissions of plants. Changes in climate together with related increases of biotic and abiotic stresses are expected to increase these emissions in the future. Ozonolysis is one of the oxidation pathways that control the fate of unsaturated alcohols in the atmosphere. The rate coefficients of the gas-phase O3 reaction with seven C5-C8 unsaturated alcohols were determined at 296 K using both absolute and relative kinetic methods. The following rate coefficients (cm3 molecule-1 s-1) were obtained using the absolute method: (1.1 ± 0.2) × 10-16 for cis-2-penten-1-ol, (1.2 ± 0.2) × 10-16 for trans-2-hexen-1-ol, (6.4 ± 1.0) × 10-17 for trans-3-hexen-1-ol, (5.8 ± 0.9) × 10-17 for cis-3-hexen-1-ol, (2.0 ± 0.3) × 10-17 for 1-octen-3-ol, and (8.4 ± 1.3) × 10-17 for trans-2-octen-1-ol. The following rate coefficients (cm3 molecule-1 s-1) were obtained using the relative method: (1.27 ± 0.11) × 10-16 for trans-2-hexen-1-ol, (5.01 ± 0.30) × 10-17 for trans-3-hexen-1-ol, (4.13 ± 0.34) × 10-17 for cis-3-hexen-1-ol, and (1.40 ± 0.12) × 10-16 for trans-4-hexen-1-ol. Alkenols display high reactivities with ozone with lifetimes in the hour range. Rate coefficients show a strong and complex dependence on the structure of the alkenol, particularly the relative position of the OH group toward the C═C double bond. The results are discussed and compared to both the available literature data and four structure-activity relationship (SAR) methods.

Assessment of the Anthropogenic Impact and Distribution of Potentially Toxic and Rare Earth Elements in Lake Sediments from North-Eastern Romania.

Chemical analysis was performed on sediment samples collected in two sampling sessions (July and October) from Podu Iloaiei Dam Lake, one of the most important water resources used for aquaculture in north-eastern Romania. The concentration of 15 trace elements (TEs), 8 refractory elements (REs), and 15 rare earth elements (REEs)-determined using inductively coupled plasma mass spectrometry-showed variability largely dependent of the sampling points and collection time. Manganese was the most abundant TE, V and Cr were the most abundant REs, while Ce was one of the most abundant REEs. The cerium negative anomaly and Gd positive anomaly were observed in the Chondrite-normalized distributions. In October, the Ce anomaly showed significant negative correlation with Mn, emphasizing the water body oxidation potential. The identified positive Gd anomaly was most likely associated with the use of Gd-chelating agents in magnetic resonance imaging in Iasi, the largest medical hub in north-eastern Romania. Principal component analysis extracted three factors explaining 96.0% of the observed variance, i.e., rock weathering, leaching from soil surface, contributions from urban stormwater and atmospheric deposition (50.9%), pedological contributions (23.7%), and mixed anthropogenic sources (e.g., traffic, waste discharge, agricultural activities; 21.4%). The evaluation of pollution indices highlighted low and moderate degrees of contamination for most of the elements and a considerable degree of contamination for Cd. Assigned Cd sources included fertilizers and pesticides used in the near agricultural areas or the high traffic road located near the lake. Since contamination of aquatic ecosystems with harmful elements is a human health concern, further monitoring of specific vectors in the food chain of the investigated dam lake will be of the utmost importance.

Gas-phase IR cross-sections and single crystal structures data for atmospheric relevant nitrocatechols.

The gas-phase IR absorption cross sections for 3-nitrocatechol, 5-methyl-3-nitrocatechol, 4-nitrocatechol and 4-methyl-5-nitrocatechol were evaluated using the ESC-Q-UAIC (the environmental simulation chamber made of quartz from the "Alexandru Ioan Cuza" University of Iasi, Romania) photoreactor facilities. Specific infrared absorptions and integrated band intensities in the range of 650-4000 cm-1 were investigated by long path gas-phase FT-IR technique. Two different addition methods (solid and liquid transfer methods) of nitrocatechols into the reactor were employed in these investigations. All investigated nitrocatechols were synthesized and characterized by X-ray diffraction spectroscopy techniques beside traditional nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy in order to evaluate their structure-properties relationship in gas and solid phase. This study reports for the first time the gas-phase infrared cross sections and the X-ray diffraction analysis for (methyl) nitrocatechols.

Size-resolved measurements of PM2.5 water-soluble elements in Iasi, north-eastern Romania: Seasonality, source apportionment and potential implications for human health.

The present paper reports the first size-resolved element measurements in the PM2.5 fraction collected throughout 2016 in the Iasi urban area in north-eastern Romania. Concentrations of water-soluble elements (Ag, Al, As, B, Ba, Be, Bi, Cd, Co, Cu, Cr, Fe, Ga, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sr, Te, Ti, U, V, Zn) were determined using inductively coupled plasma mass spectrometry. Several water-soluble heavy metals (Al, Fe, Zn, As, Cr, Pb) exhibit clear seasonal patterns with maxima over the cold season and minima over the warm season. Elements as Al, Fe, Mg, Zn, Ni, Mn, and Cu present the highest levels in the PM2.5 fraction, indicating significant contributions from soil-dust resuspension or brake lining and tires. Clear fine mode size-dependent distributions were observed for anthropogenic source-origin elements (Pb, Zn, Cd, V, etc.) due to an acidity-driven metals dissolution process. Positive matrix factorization, concentration weighted trajectory and bivariate polar plot analyses were applied to the entire PM2.5 database. Based on relative concentrations of various elements, five factors associated with specific sources were identified. The most important contributions to the total PM2.5 mass concentration (during the total period) come from secondary formation of the ammonium sulfate form (~44%) and from nitrate (~37%). Resuspended dust accounts for a contribution of about 16%, while biomass burning mixed with NaCl salt/sea-salt sources contribute as much as ~3%. Traffic and industrial sources seem to yield little contribution (<0.05%). An assessment investigation of non-carcinogenic and carcinogenic health risks revealed water-soluble arsenic and chromium (VI) as elements with the largest incremental carcinogenic risks. Both metals have traffic and industrial related sources and therefore it is believed that in the future, at the local/regional level, these sources should receive attention by implementing appropriate emission control measures.

Adsorptive Performance of Soy Bran and Mustard Husk Towards Arsenic (V) Ions from Synthetic Aqueous Solutions.

Recently, there is growing attention on the use of low-cost sorbents in the depollution of contaminated waters. As a consequence, the present work investigates the potential of soy bran and mustard husk as possible sorbent for the removal of arsenic(V) from residual water. Effects of various operating parameters such as: contact time, pH, initial arsenic concentration, pH, sorbent dose, temperature were investigated to determine the removal efficiency of arsenic(V). Thermodynamic parameters that characterize the process indicated that the adsorption is spontaneous and endothermic. The values for the separation factor, RL were less than one which confirms that the adsorption process was favorable. Equilibrium data fitted well to the Langmuir model with a higher adsorption capacity of soy bran (74.07 mg g-1) towards arsenic(V) ions than mustard husk (65.79 mg g-1). It was found that the pseudo-second order kinetic model was the best applicable model to describe the adsorption kinetic data.

A novel polymer inclusion membrane applied in chromium (VI) separation from aqueous solutions.

In the present work, we analyze the transport properties of a novel polymer inclusion membrane (PIM) containing a poly-vinyl chloride (PVC) polymer matrix and the organic anion exchanger Aliquat 336 as a specific carrier, without addition of plasticizers. The study was specifically focused on the transport properties of Cr(VI) in conditions simulating industrial wastewaters. We analyzed the impact of several parameters on the Cr(VI) transport process such as: the carrier content of the PIM, the pH, and the phases' composition. We concluded that efficient transport processes occur through a PIM containing 40% Aliquat 336/60% PVC (w/w). The process is very fast and efficient for solutions of initial Cr(VI) concentration smaller than 10(-3)mol/L, in which nearly all of Cr(VI) is removed within 3h. The performed experiments prove that Cr(VI) transport through the membrane is a facilitated counter-transport process. The obtained results sustain that this novel non-plasticized membrane possesses enhanced transport properties towards other liquid membranes and plasticized PIMs previously reported as used for Cr(VI) transport. Additionally, it possesses an excellent reliability and a high selectivity for Cr(VI) from mixtures with other metal ions and anions existing in the real industrial effluents. The PIM characterization highlights the plasticizing role of the carrier Aliquat 336.

Inhibition vs. enhancement of the nitrate-induced phototransformation of organic substrates by the *OH scavengers bicarbonate and carbonate.

Contrary to common expectations, the hydroxyl scavengers, carbonate and bicarbonate, are able to enhance the phototransformation by nitrate of a number of substituted phenols. Carbonate and bicarbonate, in addition to modifying the solution pH, are also able to induce a considerable formation of the carbonate radicals upon nitrate photolysis. The higher availability of less-reactive species than the hydroxyl radical would contribute to substantially enhance the photodegradation of the phenols/phenolates that are sufficiently reactive toward the carbonate radical. This phenomenon has a potentially important impact on the fate of the relevant compounds in surface waters. In contrast, the degradation of compounds that are not sufficiently reactive toward CO(3)(-*) is inhibited by carbonate and bicarbonate because of the scavenging of *OH.

Analysis of cyanogens with resorcinol and picrate.

The total cyanogenic potential of various substrates (flax seed, stones of peach, plum, nectarine and apricot as well as apple seeds, and various model compounds) was investigated by using the acid hydrolysis method, picrate method, and a novel method based on the reaction of cyanide liberated from plants with resorcinol and picrate. The hydrocyanic acid liberated from cyanogens was trapped by using a 1% sodium bicarbonate. Then, 1 ml of extract was mixed with 1 ml of working reagent containing 160 microg of resorcinol, 320 microg of picric acid, and 30 mg of sodium carbonate, and heated on a boiling water bath for 10 min. The absorbance was measured at 488 nm in 1cm glass cuvettes at room temperature. The color system obeys Beer's law in the range of 0-5 microg ml(-1) total HCN. Using model compounds and real samples including replicate analyses on prunasin, the resorcinol method proved to be more accurate, reproducible, and especially more sensitive than the known spectrophotometric methods such as the acid hydrolysis method and the picrate method.

Formation of organobrominated compounds in the presence of bromide under simulated atmospheric aerosol conditions.

Photobromination of phenol takes place upon UV/Vis irradiation of FeIII and bromide under acidic conditions, and most likely involves the brominating agent Br2(-*). Bromination is also observed in the presence of nitrate and bromide under UV irradiation, most likely involving Br2(-*) formed upon oxidation of bromide by *OH. Moreover, quantitative bromination of phenol is observed in the dark in the presence of hydrogen peroxide and bromide. This process is strongly favored under acidic conditions, but a residual, pH-independent bromination pathway is also present. The rates and yields of bromination (up to 100%) are considerably higher than those reported for chlorination under comparable conditions, suggesting that the higher activity of bromine species could compensate for the lower concentration of bromide ions in aerosol compared to chlorides. The reported processes are potent tial sources of reactive bromine species (Br2(-*), HBrO) and aromatic bromo derivatives in atmospheric aerosols, in particular after the acidification process linked with aerosol aging.

Sources and sinks of hydroxyl radicals upon irradiation of natural water samples.

Hydroxyl radical formation rates, steady-state concentration, and overall scavenging rate constant were measured by irradiation of surface lake water samples from Piedmont (NW Italy) and nitrate-rich groundwater samples from Moldova (NE Romania). Dissolved organic matter (DOM) was the main source and sink of *OH upon lake water irradiation, with [*OH] being independent of DOM amount. Water oxidation by photoexcited DOM is a likely *OH source in the presence of very low levels of nitrate and dissolved iron. Under different circumstances it is not possible to exclude other processes, e.g., DOM-enhanced photo-Fenton reactions. Under the hypotheses of no interaction and absence of mutual screening of radiation, nitrate would prevail over DOM as *OH source for a NO3-/DOM ratio higher than 3.3 x 10(-5) (mol NO3-) (mg C)(-1), DOM prevailing for lower values. Substantial DOM photolability was observed upon irradiation of nitrate-rich groundwater, mainly due to the elevated *OH generation rate. For the first time to our knowledge, evidence was also obtained of the photoformation of potentially toxic and/or mutagenic nitroaromatic compounds upon irradiation of natural lake water and groundwater samples, proportionally to the nitrate levels.

Photochemical reactions in the tropospheric aqueous phase and on particulate matter.

This paper is a tutorial review in the field of atmospheric chemistry. It describes some recent developments in tropospheric photochemistry in the aqueous phase and on particulate matter. The main focus is regarding the transformation processes that photochemical reactions induce on organic compounds. The relevant reactions can take place both on the surface of dispersed particles and within liquid droplets (e.g. cloud, fog, mist, dew). Direct and sensitised photolysis and the photogeneration of radical species are the main processes involved. Direct photolysis can be very important in the transformation of particle-adsorbed compounds. The significance of direct photolysis depends on the substrate under consideration and on the colour of the particle: dark carbonaceous material shields light, therefore protecting the adsorbed molecules from photodegradation, while a much lower protection is afforded for the light-shaded mineral fraction of particulate. Particulate matter is also rich in photosensitisers (e.g. quinones and aromatic carbonyls), partially derived from PAH photodegradation. These compounds can induce degradation of other molecules upon radiation absorption. Interestingly, substrates such as methoxyphenols, major constituents of wood-smoke aerosol, can also enhance the degradation of some sensitisers. Photosensitised processes in the tropospheric aqueous phase have been much less studied: it will be interesting to assess the photochemical properties of Humic-Like Substances (HULIS) that are major components of liquid droplets. The main photochemical sources of reactive radical species in aqueous solution and on particulate matter are hydrogen peroxide, nitrate, nitrite, and Fe(iii) compounds and oxides. The photogeneration of hydroxyl radicals can be important in polluted areas, while their transfer from the gas phase and dark generation are usually prevailing on an average continental scale. The reactions involving hydroxyl radicals can induce very fast transformation of compounds reacting with (*)OH at a diffusion-controlled rate (10(10) M(-1) s(-1)), with time scales of an hour or less. The hydroxyl-induced reactivity in solution can be faster than in the gas phase, influencing the degradation kinetics of water-soluble compounds. Moreover, photochemical processes in fog and cloudwater can be important sources of secondary pollutants such as nitro-, nitroso-, and chloro-derivatives.

Formation of methane sulfinic acid in the gas-phase OH-radical initiated oxidation of dimethyl sulfoxide.

Dimethyl sulfoxide (CH3S(O)CH3: DMSO) is an important product of dimethyl sulfide (CH3SCH3: DMS) photooxidation. The mechanism of the OH-radical initiated oxidation of DMSO is still highly uncertain and a major aim of recent studies has been to establish if methane sulfinic acid (CH3S(O)OH: MSIA) is a major reaction product In the present work the products of the OH-radical gas-phase oxidation of dimethyl sulfoxide have been investigated in the absence and presence of NOx All experiments were performed in a 1,080 L reaction chamber in 1,000 mbar synthetic air at 284 +/- 2 K using long-path FT-IR spectroscopy and ion chromatography to monitor and quantify reactants and reaction products. Formation of methane sulfinic acid in high yield (80-99%) was observed in both in the absence and presence of NOx, and the results support that it is the major primary reaction product Other products observed included dimethyl sulfone (CH3S(O)2CH3: DMSO2), sulfur dioxide (SO2), methane sulfonic acid (CH3S(O)2OH: MSA), and methane sulfonyl peroxynitrate (CH3S(O)2OONO2: MSPN). The formation behavior of these products is in line with their source being mainly secondary production via oxidation of a primary product, i.e. MSIA.