Reactive Halogen Research Articles

Insights into peroxymonosulfate activation for carbofuran degradation under visible LED via a double-component photocatalyst of Fe (III) impregnated N-doped TiO2

A hybrid process was proposed for carbofuran (CBF) degradation, a carbamate pesticide with a special refractory property, through peroxymonosulfate (PMS) activation under visible LED (Vis LED) by FeIII impregnated N-doped TiO2 photocatalyst (FeNT). An in-depth investigation was conducted to examine the synergistic effect of the FeNT/PMS/Vis LED process under various reaction conditions. An increase in the rate constant was observed with the increment of pH from 2.4 to 7.4, implying the feasibility of the process at neutral pH. A further increase in pH from 8.9 to 11 showed a sudden drop in the rate constant (if the role of base activation is ignored). The efficiency of CBF degradation is still more than 70% after adding NO3−, SO42−, HCO3−, and Cl−. Interestingly, the efficiency was not influenced even after the further increment of nitrate concentration. Furthermore, the high chloride concentrations caused an enhanced efficiency due to the generation of reactive halogens through two-electron transfer. Sixteen major intermediates were recognized and eight of them were never reported in the previous studies. Surprisingly, a new degradation pathway was noted in this study via H-abstractions and cyclization mechanisms. The FeNT/PMS/Vis LED process exhibited a dual functionality in terms of mineralization efficiency and about 90% TOC reduction can be achieved. Therefore, these findings provide new insights into the mechanism of PMS activation under Vis LED after coupling non-metal doped TiO2 photocatalyst with a metal component, and its implications for degradation of refractory and non-biodegradable pollutants in wastewater.

Reaction Rates Control High-Temperature Chemistry of Volcanic Gases in Air

When volcanic gases enter the atmosphere, they encounter a drastically different chemical and physical environment, triggering a range of rapid processes including photochemistry, oxidation and aerosol formation. These processes are critical to understanding the reactivity and evolution of volcanic emissions in the atmosphere yet are typically challenging to observe directly at the lava-atmosphere interface due to the nature of volcanic activity. Inferences are instead drawn largely from observations of volcanic plumes as they drift across a crater’s edge and further downwind and the application of thermodynamic models that neglect reaction kinetics as gas and air mix and thermally equilibrate. Here, we foreground chemical kinetics in simulating this critical zone. Volcanic gases are injected into a chain-of-reactors model that simulates time-resolved high-temperature chemistry in the dispersing plume. Boundary conditions of decreasing temperature and increasing proportion of air interacting with volcanic gases are specified with time according to an offline plume dynamics model. In contrast to equilibrium calculations, our chemical kinetics model predicts that CO is only partially oxidised, consistent with observed CO in volcanic plumes downwind from source. Formation of sulfate precursor SO3 at SO3/SO2 = 10-3 mol/mol is consistent with the range of reported sulfate aerosol to SO2 ratios observed close to crater rims. High temperature chemistry also forms oxidants OH, HO2, and H2O2. The H2O2 will likely augment volcanic sulfate yields by reacting with SO2(aq) in the cooled-condensed plume. Calculations show that high-temperature OH will react with volcanic halogen halides (HBr, HCl) to yield reactive halogens (Br, Cl) in the young plume. Strikingly, high-temperature production of radical oxidants (including HOx) is enhanced by volcanic emissions of reduced gases (CO, H2, H2S) due to chemical feedback mechanisms, although the kinetics of some reactions are uncertain, especially regarding sulfur. Our findings argue strongly that the chemistry of the hot near-source plume cannot be captured by equilibrium model assumptions, and highlight the need for development of more sophisticated, kinetics-based, high-temperature CHONS-halogen reaction models.

Direct detection of atmospheric atomic bromine leading to mercury and ozone depletion.

Bromine atoms play a central role in atmospheric reactive halogen chemistry, depleting ozone and elemental mercury, thereby enhancing deposition of toxic mercury, particularly in the Arctic near-surface troposphere. However, direct bromine atom measurements have been missing to date, due to the lack of analytical capability with sufficient sensitivity for ambient measurements. Here we present direct atmospheric bromine atom measurements, conducted in the springtime Arctic. Measured bromine atom levels reached 14 parts per trillion (ppt, pmol mol-1; 4.2 × 108 atoms per cm-3) and were up to 3-10 times higher than estimates using previous indirect measurements not considering the critical role of molecular bromine. Observed ozone and elemental mercury depletion rates are quantitatively explained by the measured bromine atoms, providing field validation of highly uncertain mercury chemistry. Following complete ozone depletion, elevated bromine concentrations are sustained by photochemical snowpack emissions of molecular bromine and nitrogen oxides, resulting in continued atmospheric mercury depletion. This study provides a breakthrough in quantitatively constraining bromine chemistry in the polar atmosphere, where this chemistry connects the rapidly changing surface to pollutant fate.

Halide-specific enhancement of photodegradation for sulfadiazine in estuarine waters: Roles of halogen radicals and main water constituents

Although photochemical transformation is a major degradation pathway for antibiotics in surface freshwaters, the photodegradation of antibiotics from freshwaters downstream into seawater is largely unknown. Herein, sulfadiazine was adopted as a representative antibiotic to probe the alteration of photolytic kinetics along freshwater to seawater sampled from Qinzhou Bay, China. The results showed that the photodegradation rate constants of sulfadiazine significantly increased in estuarine waters along freshwaters to seawaters. Experiments in synthetic water samples with isolated local dissolved organic matter (IL-DOM) indicated that the increased photodegradation of sulfadiazine is attributed to the integrative effect of both IL-DOM and halide ions. Radical quenching experiments with tert-butanol (quenching of ·OH) and isopropanol (quenching of both ·OH and reactive halogen species, RHS) demonstrated that RHS are largely responsible for the halide-specific enhancement in the photodegradation of sulfadiazine, rather than other reactive species, such as triplet-excited IL-DOM and ·OH. However, triplet-excited IL-DOM was involved in the production of RHS by the oxidation of halide ions by the triplet-excited states. Experiments conducted with DOM analogues verified DOM-sensitized RHS formation, and the degradation induced by RHS is positively correlated with the triplet-excited reduction potentials of DOM analogues. These findings are helpful in deeply understanding the transformation of antibiotics, and demonstrate the importance of RHS-induced degradation in antibiotics fate models in estuarine water systems.

Physicochemical properties of lactoferrin under oxidative/halogenative stress

Lactoferrin (Lf) was discovered in the thirties of the twentieth century. Since that time a number of useful properties of Lf (antibacterial, antiviral, pro- and anti-inflammatory, etc.) have been found. That’s why Lf became a promising candidate for pharmaceuticals use. The concentration of Lf strikingly increases in inflammatory focuses due to neutrophil degranulation. At the same time, activated neutrophils starts to generate reactive oxygen and halogen species (ROS and RHS), which leads to the development of oxidative/halogenative stress. In this work, using the fluorescence analysis we found the change of the Lf structure and properties in the inflammation conditions (under oxidatives/halogenative stress). We use two forms of Lf – human Lf, excreted from human milk, and recombinant Lf, excreted from milk of transgenic goats. It was established that the amino acids of Lf (decreasing the number of tryptophanils and primary amines) and protein restructuring undergo modification under the HOCl action, while H2O2 has no influence. These changes in the molecule under the HOCl treatment result in decreasing the iron-binding capacity of Lf.

Importance of reactive halogens in the tropical marine atmosphere: a regional modelling study using WRF-Chem

Abstract. This study investigates the impact of reactive halogen species (RHS, containing chlorine (Cl), bromine (Br) or iodine (I)) on atmospheric chemistry in the tropical troposphere and explores the sensitivity to uncertainties in the fluxes of RHS to the atmosphere and their chemical processing. To do this, the regional chemistry transport model WRF-Chem has been extended to include Br and I, as well as Cl chemistry for the first time, including heterogeneous recycling reactions involving sea-salt aerosol and other particles, reactions of Br and Cl with volatile organic compounds (VOCs), along with oceanic emissions of halocarbons, VOCs and inorganic iodine. The study focuses on the tropical east Pacific using field observations from the Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) campaign (January–February 2012) to evaluate the model performance. Including all the new processes, the model does a reasonable job reproducing the observed mixing ratios of bromine oxide (BrO) and iodine oxide (IO), albeit with some discrepancies, some of which can be attributed to difficulties in the model's ability to reproduce the observed halocarbons. This is somewhat expected given the large uncertainties in the air–sea fluxes of the halocarbons in a region where there are few observations of their seawater concentrations. We see a considerable impact on the inorganic bromine (Bry) partitioning when heterogeneous chemistry is included, with a greater proportion of the Bry in active forms such as BrO, HOBr and dihalogens. Including debromination of sea salt increases BrO slightly throughout the free troposphere, but in the tropical marine boundary layer, where the sea-salt particles are plentiful and relatively acidic, debromination leads to overestimation of the observed BrO. However, it should be noted that the modelled BrO was extremely sensitive to the inclusion of reactions between Br and the oxygenated VOCs (OVOCs), which convert Br to HBr, a far less reactive form of Bry. Excluding these reactions leads to modelled BrO mixing ratios greater than observed. The reactions between Br and aldehydes were found to be particularly important, despite the model underestimating the amount of aldehydes observed in the atmosphere. There are only small changes to the inorganic iodine (Iy) partitioning and IO when the heterogeneous reactions, primarily on sea salt, are included. Our model results show that tropospheric Ox loss due to halogens ranges between 25 % and 60 %. Uncertainties in the heterogeneous chemistry accounted for a small proportion of this range (25 % to 31 %). This range is in good agreement with other estimates from state-of-the-art atmospheric chemistry models. The upper bound is found when reactions between Br and Cl with VOCs are not included and, consequently, Ox loss by BrOx, ClOx and IOx cycles is high (60 %). With the inclusion of halogens in the troposphere, O3 is reduced by 7 ppbv on average. However, when reactions between Br and Cl with VOCs are not included, O3 is much lower than observed. Therefore, the tropospheric Ox budget is highly sensitive to the inclusion of halogen reactions with VOCs and to the uncertainties in current understanding of these reactions and the abundance of VOCs in the remote marine atmosphere.

CuO nanoparticles as haloperoxidase-mimics: Chloride-accelerated heterogeneous Cu-Fenton chemistry for H2O2 and glucose sensing

CuO nanoparticles (CuO NPs) were demonstrated as a novel nanoenzyme, i.e., haloperoxidase mimic, which catalyzes the oxidation of halide ions to form reactive halogen species (RHS). Two functions of CuO NPs have been demonstrated in the work. First, RHS halogenate bacterial signaling molecules, thus preventing biofilm formation. Second, CuO is used in sensitive colorimetric assays for H2O2 and glucose.

Oxygen isotope anomaly (Δ<sup>17</sup>O) in atmospheric nitrate: A review

The nitrate is a significant component in atmospheric aerosol and has a great impact on the atmospheric chemistry, fine particulate formation, radiative balance and human health. The oxygen isotope anomaly (Δ17O) is quantified as Δ17O= δ 17O-0.52× δ 18O and it represents the enrichment in 17O relative to 18O over the expected relationship ( δ 17O~0.5× δ 18O) in mass dependent fractionation processes. The Δ17O values in atmospheric nitrate (Δ17NO3-) depend on the mixing of oxygen sources (e.g. O3, H2O and O2) when NO x is photochemically converted into nitrate. In that case, the observation of Δ17NO3- coupled with photochemical modeling can be used to quantify the relative contribution of each pathway. Here, the recent research progresses of oxygen isotope anomaly of atmospheric nitrate are reviewed. Firstly, the preparation of the triple oxygen isotope (16O, 17O, 18O) measurement of atmospheric nitrate are compared: (1) The precision of the pyrolysis technique is high (±0.3‰), but this method requires relatively large amount of nitrate (>50 μmol NO3-) and complicated preparations. (2) The size and purification limitations are largely overcomed by the denitrification method conducted with Pseudomonas aureofaciens bacteria. It is suitable for isotopic analysis of nanomolar amounts of nitrate with a precision in Δ17O of ±0.6‰. (3) The reduction-azide technique also has the advantage of high precision (±0.2‰), low detection limit and sample preparation. But the utility of toxic substances (cadmium and azide) are unavoidable in the reduction. Secondly, the global characterization of Δ17NO3- are compared. Δ17NO3- tends to be higher in high latitudes than in mid-latitudes, whereas Δ17NO3- in cold seasons are higher than that in warm seasons. Thirdly, the possible formation pathways of atmospheric nitrate are summarized. NO can be converted to NO2 by O3 or HO2/RO2 in NO x cycle, and then oxidized into nitrate via NO2+·OH, NO3+HC/DMS or N2O5 hydrolysis. Reactive halogen (e.g. BrO) and HNO4 photolysis can also play an important role in nitrate formation in polar regions. Nitrate oxidized by ·OH have lower Δ17O values, and higher Δ17NO3- normally suggests more O3 oxidation. Fourthly, the Δ17O values of oxygen sources that contribute to nitrate are introduced. Among all the oxygen sources (O3, ·OH, HO2/RO2, O2 and tropospheric water), only the Δ17O of ozone is exhibited with high value (25‰–37‰), other compounds are considered to have Δ17O ~0‰. Therefore, the Δ17NO3- from each pathway can be presented based on these values. Next, the photochemical box model and other atmospheric chemical models simulating the Δ17NO3- on regional and global scale are summarized. The photochemical box model is limited for not considering the transport of atmospheric nitrate from neighboring regions. The 3-D model is more advanced than the box model for including vertical and horizontal transport, and incorporating spatial variations in surface fluxes of important primary pollutants such as NO x and VOCs. Finally, the future directions and the application of the researches on Δ17NO3- in the field of atmospheric chemistry are proposed: (1) The target areas of Δ17NO3- observation should be expanded to cover more different regions such as polluted urban and rural areas. (2) More studies are in need for decreasing the uncertainties in the simulation of Δ17NO3-. (3) The nitrate formation mechanism under different atmospheric conditions in various regions still needs to be better understood. (4) The study of oxygen isotope anomaly should be coupled with other approaches in atmospheric research (e.g. air quality modeling and online observation of chemical composition in atmospheric aerosols).

A Copper Halide Promoted Regioselective Halogenation of Coumarins Using N-Halosuccinimide as Halide Source

A safe, convenient, and regioselective synthesis of 3-halo coumarins using a metal halide (CuX2 alone or with ZnX2) promoted halogenation with N-halosuccinimide (NXS) as halide source is reported. The synthesis involved the steady in situ generation of highly reactive positive halogen (X+) by the coordination of copper or zinc with the N-halosuccinimide and subsequent electrophilic aromatic substitution of the electron-deficient coumarins. This procedure works well also for the halogenation of less electron-rich naphthoquinones, flavones, and methoxypsoralen in moderate to quantitative yields. This protocol features simple experimental conditions using readily available inexpensive reagents and provides a convenient approach to the chlorination or bromination of some useful heteroaromatic compounds.

Effect of electrolytes on the simultaneous electrochemical oxidation of sulfamethoxazole, propranolol and carbamazepine: behaviors, by-products and acute toxicity.

In this work, the effect of supporting electrolytes on the simultaneous electrochemical oxidation of the pharmaceuticals sulfamethoxazole (SMX), propranolol (PRO), and carbamazepine (CBZ) in aqueous solutions has been studied. Based on the identified by-products, the degradation mechanisms were proposed and the acute toxicity was evaluated for each electrolyte. Assays were carried out in batch mode in a 2L undivided reactor using a niobium coated with boron-doped diamond (Nb/BDD) mesh anode and Ti cathode at 2.5A in presence of different supporting electrolytes (Na2SO4, NaCl, or NaBr) at the same concentration of 7mM. The degradation rates were higher in the assays with NaCl and NaBr. Reaction by-products were identified by gas chromatography-mass spectrometry. Indirect oxidation by electrogenerated reactive halogen species (RHS) was the main mechanism when halide ions were used as electrolytes. Ten by-products were detected using Na2SO4 as electrolyte, while 19 (12 non-halogenated and 7 halogenated) and 20 (10 non-halogenated and 10 halogenated) using NaCl and NaBr respectively. The proposed degradation pathways involve transformation (hydroxylation, deamination, desulfonation, and halogenation) and bond rupture to produce less molecular weight compounds and their further transformation until total degradation. Chlorinated and brominated by-products confirm halogenation reactions. The electrogenerated RHS presented a significant inhibition effect on Vibrio fischeri; nevertheless, acute toxicity was not presented using Na2SO4 as electrolyte and a pharmaceutical concentration of 5μg/L. In this view, the role of the supporting electrolyte in electrochemical oxidation process is crucial since it strongly influence degradation rate, by-products, and acute toxicity.

Conical microstructuring of titanium by reactive gas assisted laser texturing.

Femtosecond laser micromachining is an important and flexible method to generate precisely targeted surfaces on various materials. On titanium, the laser structuring process strongly depends on the laser parameters. For example, an increasement of the pulse length and repetition rate favors melting processes instead of ablation and microstructuring. We report on an investigation of reactive halogens (iodine, bromine, chlorine) and halocarbons as additives to the laser structuring process of pure titanium and the common alloy Ti-6Al-4V with 0.75 ps laser pulses. The choice of the halogen allows control of whether solely the chemical composition or the surface microstructure should be altered. Bromine was found to be an efficient additive to generate homogeneous microstructures based on micropillars at convenient conditions (air, atmospheric pressure). The resulting surfaces have been characterised by scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal emission infrared photography, reflective UV/Vis spectroscopy and contact angle measurements. The bromine/air processed titanium surfaces revealed superhydrophilicity, strongly increased thermal emissivity and a high absorptivity (“black metal”).

Seasonal and spatial variations of chloroform, trichloroethylene, tetrachloroethylene, chlorodibromomethane and bromoform in the Northern Yellow Sea and Bohai Sea

Environmental contextVolatile halocarbons play significant roles as halogen carriers in atmospheric chemistry where they contribute to global warming. We studied temporal and spatial variations of volatile halocarbons in the Northern Yellow Sea and Bohai Sea, and showed that their concentrations were governed by terrestrial input, hydrographic features and biological activity. The emission of volatile halocarbons from coastal regions could have important impacts on the budgets of atmospheric reactive halogen. AbstractConcentrations of five volatile halocarbons (VHCs), namely, chloroform (CHCl3), trichloroethylene (C2HCl3), tetrachloroethylene (C2Cl4), chlorodibromomethane (CHBr2Cl) and bromoform (CHBr3), in the Northern Yellow Sea and Bohai Sea were determined during the spring of 2013 and autumn of 2012. Strong seasonality in the concentrations of VHCs (except for CHCl3) were observed. Concentrations of CHCl3 were markedly higher (1.5 fold) to coincide with the higher concentration of chlorophyll a during the spring. The elevated concentrations of C2HCl3, C2Cl4, CHBr2Cl and CHBr3 were found to match with the higher inputs of land runoff during autumn. The VHCs distributions evidently decreased along the freshwater plume from the mouth of rivers, such as Yellow and Yalu Rivers, to the open sea. The elevated concentrations of the selected halocarbons arise from terrestrial input, complicated hydrographic features, such as the Yellow River effluent, Yalu River, Yellow Sea Coastal Current and Yellow Sea Cold Water, and biological release by phytoplankton. Correlation analyses were conducted among Chl-a, salinity and the concentrations of these gases to investigate possible controls for the concentrations of these gases. Significant correlation was only observed between the concentrations of CHBr2Cl and Chl-a in the surface layer during spring. We made the tentative conclusion that phytoplankton biomass might not be the main limiting factor of sources of VHCs in the surface water. The sea-to-air fluxes indicated that the Northern Yellow Sea and Bohai Sea act as sources of gas in the atmosphere during spring and autumn.

Snowpack measurements suggest role for multi-year sea ice regions in Arctic atmospheric bromine and chlorine chemistry

As sources of reactive halogens, snowpacks in sea ice regions control the oxidative capacity of the Arctic atmosphere. However, measurements of snowpack halide concentrations remain sparse, particularly in the high Arctic, limiting our understanding of and ability to parameterize snowpack participation in tropospheric halogen chemistry. To address this gap, we measured concentrations of chloride, bromide, and sodium in snow samples collected during polar spring above remote multi-year sea ice (MYI) and first-year sea ice (FYI) north of Greenland and Alaska, as well as in the central Arctic, and compared these measurements to a larger dataset collected in the Alaskan coastal Arctic by Krnavek et al. (2012). Regardless of sea ice region, these surface snow samples generally featured lower salinities, compared to coastal snow. Surface snow in FYI regions was typically enriched in bromide and chloride compared to seawater, indicating snowpack deposition of bromine and chlorine-containing trace gases and an ability of the snowpack to participate further in bromine and chlorine activation processes. In contrast, surface snow in MYI regions was more often depleted in bromide, indicating it served as a source of bromine-containing trace gases to the atmosphere prior to sampling. Measurements at various snow depths indicate that the deposition of sea salt aerosols and halogen-containing trace gases to the snowpack surface played a larger role in determining surface snow halide concentrations compared to upward brine migration from sea ice. Calculated enrichment factors for bromide and chloride, relative to sodium, in the MYI snow samples suggests that MYI regions, in addition to FYI regions, have the potential to play an active role in Arctic boundary layer bromine and chlorine chemistry. The ability of MYI regions to participate in springtime atmospheric halogen chemistry should be considered in regional modeling of halogen activation and interpretation of satellite-based tropospheric bromine monoxide column measurements.

KANDUNGAN FLUORIDE DALAM AIR MINUM ISI ULANG DI KOTA BATAM

Water needs are very good for humans because they are human body-forming substances. Public awareness of getting water that meets health requirements is increasing. People tend to choose more practical methods with relatively low costs in meeting drinking water needs, especially in the city of Batam. One of the fulfillment of drinking water needs that is an alternative is to use refill drinking water. The source of raw water for drinking water in the city of Batam comes from reservoir water. Water is a source of high fluoride intake. Thus, fluoride levels in water used for consumption must be considered so as not to overdo it. Fluoride is a highly reactive halogen, so it is always obtained in the form of compounds. Inorganic fluorides are toxic and more irritant than organic ones. Chronic poisoning causes people to become thin, disrupted body growth, dental fluorosis and skeletal and digestive disorders that can be accompanied by dehydration. The method used in this study is simple randomized sampling. The standard method of analysis for fluoride parameters (F) is the 4500-F-D method (SPADNS colorimetric method) used in the laboratory of PT. Sucofindo Batam. Laboratory test results of PT. Sucofindo Batam from the six refill drinking water samples taken, namely Fun Qua Batu Ampar, Salsabila Batam Center, Pak De Qua Tiban, Fresh Qua, Bengkong and Salwa Qua Tembesi obtained results of fluoride level analysis of <0.06 mg / L. While the results of fluoride level analysis from Alam Qua Piayu were obtained at 0.43 mg / L. Refill water treatment from 6 locations of drinking water depots based on by Regulation of the Minister of Health No. 492 of 2010 still meets the quality standards set at 1.5 mg / L.

Airborne Observations of Reactive Inorganic Chlorine and Bromine Species in the Exhaust of Coal-Fired Power Plants.

We present airborne observations of gaseous reactive halogen species (HCl, Cl2, ClNO2, Br2,BrNO2, and BrCl), sulfur dioxide (SO2), and nonrefractory fine particulate chloride (pCl) and sulfate(pSO4) in power plant exhaust. Measurements were conducted during the Wintertime INvestigation of Transport, Emissions, and Reactivity campaign in February-March of 2015 aboard the NCAR-NSF C-130 aircraft. Fifty air mass encounters were identified in which SO2 levels were elevated ~5 ppb above ambient background levels and in proximity to operational power plants. Each encounter was attributed to one or more potential emission sources using a simple wind trajectory analysis. In case studies, we compare measured emission ratios to those reported in the 2011 National Emissions Inventory and present evidence of the conversion of HCl emitted from power plants to ClNO2. Taking into account possible chemical conversion downwind, there was general agreement between the observed and reported HCl: SO2 emission ratios. Reactive bromine species (Br2, BrNO2, and/or BrCl) were detected in the exhaust of some coal-fired power plants, likely related to the absence of wet flue gas desulfurization emission control technology. Levels of bromine species enhanced in some encounters exceeded those expected assuming all of the native bromide in coal was released to the atmosphere, though there was no reported use of bromide salts (as a way to reduce mercury emissions) during Wintertime INvestigation of Transport, Emissions, and Reactivity observations. These measurements represent the first ever in-flight observations of reactive gaseous chlorine and bromine containing compounds present in coal-fired power plant exhaust.

Heterogeneity of hypochlorous acid production in individual neutrophil phagosomes revealed by a rhodamine-based probe

The rhodamine-based probe R19-S has been shown to react with hypochlorous acid (HOCl) to yield fluorescent R19, but not with some other oxidants including hydrogen peroxide. Here, we further examined the specificity of R19-S and used it for real-time monitoring of HOCl production in neutrophil phagosomes. We show that it also reacts rapidly with hypobromous acid, bromamines, and hypoiodous acid, indicating that R19-S responds to these reactive halogen species as well as HOCl. Hypothiocyanous acid and taurine chloramine were unreactive, however, and ammonia chloramine and dichloramine reacted only very slowly. MS analyses revealed additional products from the reaction of HOCl with R19-S, including a chlorinated species as a minor product. Of note, phagocytosis of opsonized zymosan or Staphylococcus aureus by neutrophils was accompanied by an increase in R19 fluorescence. This increase depended on NADPH oxidase and myeloperoxidase activities, and detection of chlorinated R19-S confirmed its specificity for HOCl. Using live-cell imaging to track individual phagosomes in single neutrophils, we observed considerable heterogeneity among the phagosomes in the time from ingestion of a zymosan particle to when fluorescence was first detected, ranging from 1 to >30 min. However, once initiated, the subsequent fluorescence increase was uniform, reaching a similar maximum in ∼10 min. Our results confirm the utility of R19-S for detecting HOCl in real-time and provide definitive evidence that isolated neutrophils produce HOCl in phagosomes. The intriguing variability in the onset of HOCl production among phagosomes identified here could influence the way they kill ingested bacteria.

DMS oxidation and sulfur aerosol formation in the marine troposphere: a focus on reactive halogen and multiphase chemistry

Abstract. The oxidation of dimethyl sulfide (DMS) in the troposphere and subsequent chemical conversion into sulfur dioxide (SO2) and methane sulfonic acid (MSA) are key processes for the formation and growth of sulfur-containing aerosol and cloud condensation nuclei (CCN), but are highly simplified in large-scale models of the atmosphere. In this study, we implement a series of gas-phase and multiphase sulfur oxidation mechanisms into the Goddard Earth Observing System-Chemistry (GEOS-Chem) global chemical transport model – including two important intermediates, dimethyl sulfoxide (DMSO) and methane sulphinic acid (MSIA) – to investigate the sulfur cycle in the global marine troposphere. We found that DMS is mainly oxidized in the gas phase by OH (66 %), NO3 (16 %) and BrO (12 %) globally. DMS + BrO is important for the model's ability to reproduce the observed seasonality of surface DMS mixing ratio in the Southern Hemisphere. MSA is mainly produced from multiphase oxidation of MSIA by OH(aq) (66 %) and O3(aq) (30 %) in cloud droplets and aerosols. Aqueous-phase reaction with OH accounts for only 12 % of MSA removal globally, and a higher MSA removal rate is needed to reproduce observations of the MSA ∕ nssSO42- ratio. The modeled conversion yield of DMS into SO2 and MSA is 75 % and 15 %, respectively, compared to 91 % and 9 % in the standard model run that includes only gas-phase oxidation of DMS by OH and NO3. The remaining 10 % of DMS is lost via deposition of intermediates DMSO and MSIA. The largest uncertainties for modeling sulfur chemistry in the marine boundary layer (MBL) are unknown concentrations of reactive halogens (BrO and Cl) and OH(aq) concentrations in cloud droplets and aerosols. To reduce uncertainties in MBL sulfur chemistry, we should prioritize observations of reactive halogens and OH(aq).

Polar Nighttime Chemistry Produces Intense Reactive Bromine Events

AbstractBy examining the origin of airmasses that arrive at Utqiaġvik (formerly Barrow), Alaska, soon after polar sunrise (late January/early February), we identified periods when air arriving at Utqiaġvik had previously resided primarily at higher latitudes in near total darkness. Upon illumination, these airmasses produced high concentrations of reactive bromine, which was detected by differential optical absorption spectroscopy as bromine monoxide (BrO). These observations are consistent with nighttime production of a photolabile reactive bromine precursor (e.g., Br2 or BrCl). A large polar night source of photolabile reactive bromine precursors would contribute seed reactive bromine to daytime reactive bromine events and could export reactive halogens to lower latitudes and the free troposphere.

Halogenation Chemistry of Hydraulic Fracturing Additives under Highly Saline Simulated Subsurface Conditions.

Unconventional natural gas extraction via hydraulic fracturing coupled with horizontal drilling (HDHF) has generated disruptive growth in the domestic energy sector. Field analyses of residual HDHF fluids have detected halogenated species, potentially the product of unexplored reactions between authigenic halides and HDHF additives. Utilizing a custom high-pressure reactor system, we simultaneously screened 12 frequently disclosed, functionally diverse HDHF additives to uncover transformation chemistry. One emergent pathway, the halogenation of cinnamaldehyde in the presence of ammonium persulfate, demonstrated the potential for oxidative breakers to react with halides to yield reactive halogen species. Halogenated product formation, product distribution, and kinetics were evaluated with respect to shale well subsurface condition, linking transformation risk to measurable well-dependent characteristics (e.g., halide compositions, well temperatures, and pH). In a representative flowback brine, the brominated product dominated on a molar percent basis (6 ± 2%, as normalized by initial cinnamaldehyde loading) over chlorinated (1.4 ± 0.4%) and iodinated forms (2.5 ± 0.9%), reflecting relative halide abundance and propensity for oxidation. This work demonstrates that relevant subsurface reactions between natural brines and hydraulic fracturing additives can result in the unintended formation of halogenated products.

Flight Deployment of a High‐Resolution Time‐of‐Flight Chemical Ionization Mass Spectrometer: Observations of Reactive Halogen and Nitrogen Oxide Species

AbstractWe describe the University of Washington airborne high‐resolution time‐of‐flight chemical ionization mass spectrometer (HRToF‐CIMS) and evaluate its performance aboard the NCAR‐NSF C‐130 aircraft during the recent Wintertime INvestigation of Transport, Emissions and Reactivity (WINTER) experiment in February–March of 2015. New features include (i) a computer‐controlled dynamic pinhole that maintains constant mass flow‐rate into the instrument independent of altitude changes to minimize variations in instrument response times; (ii) continuous addition of low flow‐rate humidified ultrahigh purity nitrogen to minimize the difference in water vapor pressure, hence instrument sensitivity, between ambient and background determinations; (iii) deployment of a calibration source continuously generating isotopically labeled dinitrogen pentoxide (15N2O5) for in‐flight delivery; and (iv) frequent instrument background determinations to account for memory effects resulting from the interaction between sticky compounds and instrument surface following encounters with concentrated air parcels. The resulting improvements to precision and accuracy, along with the simultaneous acquisition of these species and the full set of their isotopologues, allow for more reliable identification, source attribution, and budget accounting, for example, by speciating the individual constituents of nocturnal reactive nitrogen oxides (NOz = ClNO2 + 2 × N2O5 + HNO3 + etc.). We report on an expanded set of species quantified using iodide‐adduct ionization such as sulfur dioxide (SO2), hydrogen chloride (HCl), and other inorganic reactive halogen species including hypochlorous acid, nitryl chloride, chlorine, nitryl bromide, bromine, and bromine chloride (HOCl, ClNO2, Cl2, BrNO2, Br2, and BrCl, respectively).