Amounts Of ClO Research Articles

Enriched detection nanoparticles for hypochlorite prepared by electrostatic spray, applied to tumor imaging, antibacterial and antiviral

Hypochlorite (ClO-) as a common reactive oxygen species (ROS) plays a vital role in physiological processes. However, an excessive amount of ClO- can lead to cell damage and is closely associated with the occurrence of diseases such as cancer. The high-sensitivity monitoring of intracellular ClO- is of great significance in the field of cancer diagnosis. Therefore, we have employed the electrostatic spray technology to fabricate a multifunctional nanoparticle C@B NPs and for the first time in ion sensors, proposed a method to enhance the sensitivity of sensor by increasing the electrostatic adsorption. C@B NPs can enrich ClO- onto their surface, forming a high-concentration area. It can respond better with C@B NPs, achieving enhanced sensing sensitivity, the lowest limit of detection is 1.81 nM. C@B NPs possess good anti-interference ability and biocompatibility, enabling the distinction and recognition between normal cells and cancer cells, as well as tumor imaging in live mice. Additionally, due to the large amount of quaternary ammonium salt structures in C@B NPs, they also exhibit excellent antibacterial and antiviral properties, inhibition rate bacteria and viruses against 100 %. It is first nanoparticles integrates tumor imaging, antibacterial and antiviral functions, showing potential in tumor visualization and treatment of infections.

Influence of Kappa Number on Enhancing Pulp Brightness through Stage D0 with ClO2 Bleaching Process: Environmental Implications and Considerations

<p>Stage D0 in the pulp bleaching process, utilizing Chlorine Dioxide (ClO2), represents a critical phase aimed at improving pulp brightness while simultaneously addressing environmental concerns. This stage enhancement of pulp brightness can made an environmental impact, as excessive usage can lead to harmful emissions and environmental degradation. The amount of ClO<sub>2</sub> used at stage D0 is influenced by the kappa number, the greater the kappa number, the greater the ClO<sub>2</sub> use will be to produce brightness that corresponds to standar. The calculation of ClO<sub>2</sub> usage at stage D0 is carried out after obtaining data related to ClO<sub>2</sub> and the amount of pulp production from DCS (Distribute Control System). Based on the results of calculations and analysis, it can be concluded that the kappa number influences the total use of ClO<sub>2</sub> in stage D0. The more ClO<sub>2</sub> used in the D0 tower will produce pulp with a higher level of brightness.</p>

A triphenylamine-based carbohydrazide hydrazone fluorescent probe for selective detection of hypochlorite and sensing acidic gases.

Hypochlorous acid and its hypochlorite are important reactive oxygen species in the body, and are involved in various physiological processes related to immunity; their rapid detection is of great significance. Here, we synthesized a fluorescent probe (TPAS) by condensation of 4-(diphenylamino)benzaldehyde, carbohydrazide, and salicylaldehyde, which can be used for the detection of ClO- in water and sensing of acidic gas in its solid state. The probe showed strong selective recognition of ClO- in acetonitrile and good tolerance to interference ions. There were good linear responses between the intensity of absorbance and fluorescence and the amount of ClO-. The TPAS solid and its paper strips can emit red fluorescence when exposed to volatile acidic vapours. After being treated with NH3, the red fluorescence can be restored to yellow. The response process of TPAS to ClO- and acid gases was characterized using nuclear magnetic resonance, electrospray ionisation mass spectrometry, transmission electron microscopy, and density functional theory calculations. Furthermore, it can be utilized in analyzing ClO- in commercially available bleaching products; the detection results were basically compatible with the labelled values. In addition, the probe is biocompatible and can be applied for imaging ClO- in zebrafish.

A novel thienothiophene-based “dual-responsive” probe for rapid, selective and sensitive detection of hypochlorite

BackgroundHypochlorite/hypochlorous acid (ClO−/HOCl) is a biologically crucial reactive oxygen species (ROS), produced in living organisms and has a critical role as an antimicrobial agent in the natural defense system. However, when ClO− is produced excessively, it can lead to the oxidative damage of biomolecules, resulting in organ damage and various diseases. Therefore, it is imperative to have a straightforward, quick and reliable method for over watching the minimum amount of ClO− in different environments. ResultsHerein, a new probe TTM, containing thienothiophene and malononitrile units, was developed for exceptionally selective and sensitive hypochlorite (ClO−) detection. TTM demonstrated a rapid “turn-on” fluorescence response (<30 s), naked-eye detection (colorimetric), voltammetric read-out with anodic scan, low detection limit (LOD = 0.58 μM and 1.43 μM for optical and electrochemical methods, respectively) and applicability in detecting ClO− in real water samples and living cells. Significance and noveltyThis study represents one of the rare examples of a small thienothiophene-based molecule for both optical and electrochemical detections of ClO− in an aqueous medium.

Dye-Triplet-Sensitized Downshifting Nanoprobes with Ratiometric Dual-NIR-IIb Emission for Accurate In Vivo Detection.

Despite the emerging near-infrared-IIb (NIR-IIb, 1500-1700 nm) bioimaging significantly improving the in vivo penetration depth and resolution, quantitative detection with accuracy remains challenging due to its inhomogeneous fluorescence signal attenuation in biological tissue. Here, ratiometric dual-NIR-IIb in vivo detection with excitation wavelengths of 808 and 980 nm is presented using analyte-responsive dye-triplet-sensitized downshifting nanoprobes (DSNPs). NIR cyanine dye IR-808, a recognizer of biomarker hypochlorite (ClO-), is introduced to trigger a triplet energy transfer process from the dye to Er3+ ions of DSNPs under 808 nm excitation, facilitating the formation of an analyte-responsive 1525 nm NIR-IIb assay channel. Meanwhile, DSNPs also enable emitting intrinsic nonanalyte-dependent downshifting fluorescence at the same NIR-IIb window under 980 nm excitation, serving as a self-calibrated signal to alleviate the interference from the probe amount and depth. Due to the two detected emissions sharing identical light propagation and scattering, the ratiometric NIR-IIb signal is demonstrated to ignore the depth of penetration in biotissue. The arthritis lesions are distinguished from normal tissue using ratiometric probes, and the amount of ClO- can be accurately output by the established detection curves.

Monitoring of Hypochlorite Level in Fruits, Vegetables, and Dairy Products: A BODIPY-Based Fluorescent Probe for the Rapid and Highly Selective Detection of Hypochlorite.

Hypochlorite/hypochlorous acid (ClO-/HOCl), among the diverse reactive oxygen species, plays a vital role in various biological processes. Besides, ClO- is widely known as a sanitizer for fruits, vegetables, and fresh-cut produce, killing bacteria and pathogens. However, excessive level of ClO- can lead to the oxidation of biomolecules such as DNA, RNA, and proteins, threatening vital organs. Therefore, reliable and effective methods are of utmost importance to monitor trace amounts of ClO-. In this work, a novel BODIPY-based fluorescent probe bearing thiophene and a malononitrile moiety (BOD-CN) was designed and constructed to efficiently detect ClO-, which exhibited distinct features such as excellent selectivity, sensitivity (LOD = 83.3 nM), and rapid response (<30 s). Importantly, the probe successfully detected ClO- in various spiked water, milk, vegetable, and fruit samples. In all, BOD-CN offers a clearly promising approach to describe the quality of ClO--added dairy products, water, fresh vegetables, and fruits.

Tetraphenylethylene–thiosemicarbazone based ultrafast, highly sensitive detection of hypochlorite in aqueous environments and dairy products

We have designed and synthesised a novel fluorescent probe with a tetraphenylethylene (TPE) scaffold as an active fluorescent unit and thiosemicarbazide (TSC) group as a recognition unit. The probe, TPE–TSC, exhibited superior selectivity towards hypochlorite (ClO−) with a low limit of detection (2.0 nM). It also demonstrated a turn-off response for a brief period (<30 s) via an oxidation reaction. Furthermore, high-resolution mass spectrometry (HRMS) revealed that TPE–TSC reacted with ClO− by forming a carboxylic acid moiety in nearly 100% aqueous environments. More significantly, the probe detected ClO− in disinfectant, spiked milk samples, and spiked water samples. In all, TPE–TSC proposes an optimistic approach precisely for the determining the quality of milk and water contaminated with ClO− and trace amounts of ClO− in disinfectants.

Ratiometric fluorescence sensing of UiO-66-NH2 toward hypochlorite with novel dual emission in vitro and in vivo

Developing fluorescent probes to detect reactive oxygen species (ROS) is imperative to understanding the vital roles of ROS in various signaling and pathological processes. In this work, UiO-66-NH2 could be readily utilized as self-calibrating nanoprobe for selective detection and bioimaging of hypochlorite. Under the excitation of 400 nm, UiO-66-NH2 featured an emission at 432 nm and a new emission at 533 nm appeared after the addition of ClO-. Besides, the emission intensity of 533 nm increased with the incremental amount of ClO-. By using the ratio I533 nm/I432 nm as detection signal, UiO-66-NH2 could discriminate ClO- with high performance. The linear working range towards ClO- is 0.1–150 μM and the detection limit is 63.8 nM. In contrast to most other ratiometric sensors fabricated by physical entrapment methods, UiO-66-NH2 has the obvious advantage of effectively avoiding the worry of leakage of fluorophores from the nanomaterial matrix of sensors leading to erroneous measurements. Other amino-group functionalized MOF-based sensors such as MIL-53-NH2(Al) and MIL-101-NH2(Fe) exhibited similar fluorescence response toward ClO- as UiO-66-NH2. This work raises the possibility to develop highly specific and efficient probe for ClO- detection in vivo or in living cells and presents a new insight into ratiometric sensors.

Fluorescence probe for hypochlorous acid in water and its applications for highly lysosome-targetable live cell imaging

Hypochloric acid (HOCl) plays important roles in cell signaling and homeostasis, such as anti-inflammation and immune regulation, pathogen response and so on. Accordingly, direct detection of HOCl at the organelle level is important for investigation of the complex contributions of HOCl to human health. In the present study, a water soluble lysosome-targeting fluorescent probe Lyso-1 bearing a hydrazone moiety as a HOCl-responsive site and a morpholine unit as a lysosomal-targeting group has been synthesized and evaluated for its ability to image lysosomal HOCl. The probe Lyso-1, based on a novel HOCl-promoted hydrazone oxidation strategy, showed a highly selective fluorescent off/on response to HOCl with the various reactive oxygen species in water. With increasing amount of ClO− from 0.5 to 2.5 μM, a linear correlation between the fluorescence intensity (570 nm) of Lyso-1 and [ClO−] was found, and the regression equation was y = 96.65 + 110.2068[ClO−] with a linear coefficient R of 0.9920. The detection limit is determined to be 60 nM. Lyso-1 demonstrated a perfect lysosomal targetable ability, and was successfully applied to image of exogenous, endogenous produced lysosomal HOCl in live L929 cells. The success of subcellular imaging indicated that the lysosome-targetable probe Lyso-1 could be used in further applications for the investigation of biological functions and pathological roles of HClO at organelle levels.

Perchlorate Production by Photodecomposition of Aqueous Chlorine Solutions

Aqueous chlorine solutions (defined as chlorine solutions (Cl(2,T)) containing solely or a combination of molecular chlorine (Cl(2)), hypochlorous acid (HOCl), and hypochlorite (OCl(-))) are known to produce toxic inorganic disinfection byproduct (e.g., chlorate and chlorite) through photoactivated transformations. Recent reports of perchlorate (ClO(4)(-)) production-a well-known thyroid hormone disruptor- from stored bleach solutions indicates the presence of unexplored transformation pathway(s). The evaluation of this potential ClO(4)(-) source is important given the widespread use of aqueous chlorine as a disinfectant. In this study, we perform detailed rate analysis of ClO(4)(-) generation from aqueous chlorine under varying environmental conditions including ultraviolet (UV) light sources, intensity, solution pH, and Cl(2,T) concentrations. Our results show that ClO(4)(-) is produced upon UV exposure of aqueous chlorine solutions with yields ranging from 0.09 × 10(-3) to 9.2 × 10(-3)% for all experimental conditions. The amount of ClO(4)(-) produced depends on the starting concentrations of Cl(2,T) and ClO(3)(-), UV source wavelength, and solution pH, but it is independent of light intensity. We hypothesize a mechanistic pathway derived from known reactions of Cl(2,T) photodecomposition that involves the reaction of Cl radicals with ClO(3)(-) to produce ClO(4)(-) with calculated rate coefficient (k(ClO4-)) of (4-40) × 10(5) M(-1) s(-1) and (3-250) × 10(5) M(-1) s(-1) for UV-B/C and UV-A, respectively. The measured ClO(4)(-) concentrations for both UV-B and UV-C experiments agreed well with our model (R(2) = 0.88-0.99), except under UV-A light exposure (R(2) = 0.52-0.93), suggesting the possible involvement of additional pathways at higher wavelengths. Based on our results, phototransformation of aqueous chlorine solutions at concentrations relevant to drinking water treatment would result in ClO(4)(-) concentrations (~0.1 μg L(-1)) much below the proposed drinking water limits. The importance of the hypothesized mechanism is discussed in relation to natural ClO(4)(-) formation by atmospheric transformations.

Using Chlorine Dioxide to Remove the Fouling of Ultrafiltration Membrane and Control Disinfection By-Products

Ultrafiltration (UF) can remove natural organic matter (NOM) effectively. Moreover, chlorine dioxide (ClO 2 ) has been an alternative disinfectant as it forms fewer disinfection by-products with NOM than chlorination does. Therefore, combining ClO 2 with UF may improve conventional purification processes. In this study, feed water containing humic acid with 4.07 mg/L total organic carbon (TOC) was dosed directly with various amounts of ClO 2 (0, 2, 5, 10, and 15 mg/L) before being filtered through a 5-kDa UF membrane. With a low dose (2 mg/L ClO 2 ), UF removed humic acid effectively, as TOC was not detected in the permeate, and the permeate flux increased to about 80% of the initial permeate flux by cross flow. Moreover, the concentrations of ClO 2 ― , ClO 3 ― , and trihalomethanes in the permeate were below the United States Environmental Protection Agency guidelines.

Evidence for heterogeneous chlorine activation in the tropical UTLS

Abstract. Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brazil, February 2005) and SCOUT-O3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10–20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt – significantly exceeding those expected from gas phase chemistry – were observed in air masses of a more tropospheric character. Most of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. However, to reproduce the ClO observations in these simulations, O3 mixing ratios higher than observed had to be assumed, and at least for one of these flights, a significant denoxification is in contrast to the observed NO levels, suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.

The influence of disinfection on aquatic biodegradable organic carbon formation

The aim of this paper was to assess the extent of biodegradable dissolved organic carbon formation upon disinfection of water with chlorine dioxide. Wide diversity of natural waters has been subjected to reactions with various amounts of ClO 2. For comparison examined waters have also been treated with ozone and chlorine. The application of chlorine dioxide and ozone significantly changed the molecular weight distribution of aquatic organic matter. As a result significant amounts of biodegradable carboxylic acids and aldehydes were generated. The formic, acetic, oxalic and ketomalonic acids as well as formaldehyde, acetaldehyde, glyoxal, methylglyoxal were identified. The productivity of aldehydes calculated for all examined waters and disinfectants amounted 12.7–47.7 μg mg −1 DOC in the case of ozonation, 1.3–8.1 μg mg −1 DOC after chlorination and 1.7–9.4 μg mg −1 DOC for ClO 2 treatment. The highest total concentration of carboxylic acids was determined after the ozonation processes. In this case the organic acids' formation potential was in the range 10.8–62.8 μg mg −1 DOC. Relatively high formation potential (5.3–17.9 μg mg −1 DOC) was determined after the oxidation with ClO 2 as well. In the case of chlorination, the productivity of organic acids was low and did not exceed 3.4 μg mg −1 DOC. The relatively high correlation between BDOC formation and carboxylic acids' formation potential was observed. Thus, carboxylic acids' formation potential may be used as a measure of water potential to form BDOC.

Metastable and stable pitting events on Al induced by chlorate and perchlorate anions—Polarization, XPS and SEM studies

The metastable and stable pitting events of Al were studied in 0.075 M deaerated acidic NaClO 3 and NaClO 4 solutions (pH 3) using potentiodynamic anodic polarization and potentiostatic measurements, complemented with SEM and XPS examinations of the electrode surface. Metastable pits (appeared here as oscillations in current in the nA range) form at potentials close to the pitting potential ( E pit). SEM examinations of the electrode surface showed that the current oscillations resulted in observable pits on sample surface. The repassivated metastable pitting sites are prone to become preferential sites for following metastable pits to nucleate, resulting in accumulated corrosion damages on the surface. Results showed that Cl − ions produced in solution via the reduction of ClO 3 − and ClO 4 − anions at sufficiently negative cathodic potentials as well as their decomposition at high anodic potentials. Chloride production induced via the reduction of perchlorates is much slower than induced by chlorates. XPS examinations of the electrode surface showed that the amount of ClO 4 − and Cl − anions detected on the electrode surface increases with both cathodic and anodic polarizations (even above E pit). Experimental results revealed that addition of Cl − ions to the ClO 4 − solution accelerates pitting corrosion, indicating that these anions cooperate together in passivity breakdown and initiation of pitting. The role of ClO 3 − and ClO 4 − ions, despite their large size, in pitting process is also discussed here. A point defect model (PDM) is employed to explain passivity breakdown induced by pitting corrosion as a result of the aggressive attack of Cl − ions.

Chlorine dioxide reaction with selected amino acids in water

Chlorine dioxide is a hypochlorite alternative disinfectant agent. In this context, we have determined the products formed in the reaction of ClO 2 with selected amino acids as model compounds that can be present in natural waters. The reaction of tryptophane, histidine and tyrosine (10 ppm each) with ClO 2 were studied at molar ratios ranging from 0.25 to 4 in the presence or absence of oxygen. It was found that in the absence of oxygen adding substoichiometric amounts of ClO 2 creates products that are structurally similar to the starting amino acids. Through a series of cascade reactions the initial product distribution gradually evolves toward simple, small carbon chain products that are far from the starting amino acid. The reaction product distribution revealed that chlorine dioxide can attack the electron-rich aromatic moieties as well as the nitrogen atom lone electron pair. Our study is relevant to gain knowledge on the reaction mechanism of ClO 2 with ubiquitous amino acids present in natural waters.

Perchlorate production by ozone oxidation of chloride in aqueous and dry systems

Overwhelming evidence now exists that perchlorate is produced through natural processes and can be ubiquitously found at environmentally relevant concentrations in arid and semi-arid locations. A number of potential production mechanisms have been hypothesized and ClO 4 − production by ozone oxidation of surface bound Cl − was demonstrated. However, no information concerning the impact of concentration, final reaction products distribution, impact of reaction phase, or oxidation of important oxychlorine intermediates has been reported. Using IC-MS–MS analysis and replicate oxidation experiments, we show that exposing aqueous solutions or Cl − coated sand or glass surfaces to O 3 (0.96%) generated ClO 4 − with molar yields of 0.007 and 0.01% for aqueous Cl − solutions and 0.025 and 0.42% for Cl − coated sand and glass, respectively. Aqueous solutions of Cl − produced less ClO 4 − than Cl − coated sand or glass as well as a higher ratio of ClO 3 − to ClO 4 −. Reduction of the initial Cl − mass resulted in substantially higher molar yields of ClO 4 − and ClO 3 −. In addition, alkaline absorbers that captured gaseous products contained substantial quantities of Cl −, ClO 3 −, and ClO 4 −. Solutions of possible oxychlorine intermediates (OCl − and ClO 3 −) exposed to O 3 produced only scant amounts of ClO 4 − while a ClO 2 − solution exposed to O 3 produced substantial molar yields of ClO 4 − (4% molar yield). Scanning electron microscopy coupled with energy energy-dispersive X-ray analysis demonstrated a significant loss of Cl − and an increase in oxygen on the Cl − coated silica sand exposed to O 3. While the experimental conditions are not reflective of natural conditions this work clearly demonstrates the relative potential of Cl − precursors in perchlorate production and the likely importance of dry aerosol oxidation over solution phase reactions. It also suggests that ClO 2 − may be a key intermediate while ClO 3 − and OCl − are unlikely to play a significant role.

Production and stability of chlorine dioxide in organic acid solutions as affected by pH, type of acid, and concentration of sodium chlorite, and its effectiveness in inactivating Bacillus cereus spores

We studied the production and stability of chlorine dioxide (ClO 2) in organic acid solutions and its effectiveness in killing Bacillus cereus spores. Sodium chlorite (5000, 10,000, or 50,000 μg/ml) was added to 5% acetic, citric, or lactic acid solution, adjusted to pH 3.0, 4.0, 5.0, or 6.0, and held at 21 °C for up to 14 days. The amount of ClO 2 produced was higher as the concentration of sodium chlorite was increased and as the pH of the acid solutions was decreased. However, the stability in production of ClO 2 was enhanced by increasing the pH of the organic acid solutions. To evaluate the lethal activity of ClO 2 produced in various acid solutions as affected by acidulant and pH, suspensions of B. cereus spores were treated at 21 °C for 1, 3, 5, or 10 min in hydrochloric acid or organic acid solutions (pH 3.0, 4.0, 5.0, or 6.0) containing ClO 2 at concentrations of 100, 50, or 25 μg/ml. Populations of viable spores treated with ClO 2 at concentrations of 100 or 50 μg/ml in organic acid solutions decreased more rapidly than populations treated with the same concentrations of ClO 2 in HCl. Rates of inactivation tended to increase with higher pH of ClO 2 solutions. Results show that ClO 2 formed in organic acid solutions has higher stability and is more lethal to B. cereus spores than ClO 2 formed at the same concentration in HCl solution. This finding emphasizes the benefits of using organic acid solutions to prepare ClO 2 intended for use as an antimicrobial.

Reaction of chlorine dioxide with emergent water pollutants: Product study of the reaction of three β-lactam antibiotics with ClO 2

This work deals with the chlorine dioxide (ClO 2) reactivity with three representative β-lactam antibiotics (penicillin, amoxicillin and cefadroxil) that can be present in natural aquatic resources. Due to the wide use of ClO 2 as disinfection agent our work is of interest to determine the fate of these antibiotics during the water treatment process. Our study shows that antibiotics react stoichiometrically with ClO 2 because increasing amounts of ClO 2 lead to increasing antibiotic disappearance. Concerning the influence of antibiotic structure, penicillin reacts sluggishly with ClO 2, whereas amoxicillin and cefadroxil are highly reactive at either neutral or basic pH. For both reactive antibiotics, hydroquinone together with a wide range of 4-substituted phenols were detected as products. Pretreatment with ClO 2 before chlorination of aqueous solutions of antibiotics reduces the trihalomethane formation as compared with analogous chlorination without ClO 2 pretreatment.

Observation of unusual chlorine activation by ground-based infrared and microwave spectroscopy in the late Arctic winter 2000/01

Abstract. During the Arctic winter of 2000/01, ground-based FTIR and millimetre-wave measurements revealed significant amounts of ClO over Kiruna after the final warming in February 2001. In fact, column amounts of ClO were still increased in March 2001 when temperatures were about 20K above the PSC (Polar Stratospheric Clouds) threshold. At these temperatures, chlorine activation due to heterogeneous processes on PSCs is not possible even in the presence of strong lee wave effects. In order to discuss possible reasons of this feature, time series of other chemical species will be presented and discussed, too. Measurements of HF and COF2 indicated that vortex air was still observed in mid-March 2001. Since the time series of HNO3 column amounts do not give any evidence of a denitrification later than 11 February, chlorine activation persisting for several weeks after the presence of PSCs due to denitrification is rather unlikely. The photolysis of ClONO2-rich air which had been formed at the end of February and beginning of March 2001 as well as chlorine activation due to the presence of an unusual aerosol layer are discussed as possible causes of the increased ClO column amounts after the final warming.

High ClO and ozone depletion observed in the plume of Sakurajima volcano, Japan

Enhanced BrO and ClO in the boundary layer associated with ozone destruction have been observed over salt lakes, as well as in the polar boundary layer. Volcanic plumes are a major natural source of atmospheric trace gases, influencing the tropospheric and stratospheric trace gas budgets. Though a variety of volcanic gases have been investigated and BrO was found, there is still little information on other halogen oxides (e.g. ClO) in volcanic plumes and the effects on atmospheric ozone. The current belief that volcanic plumes contain ClO has not been quantified to date. Here we report the successful remote measurement of significant amounts of ClO (as well as BrO and SO2) in a volcanic plume from the Sakurajima volcano in Japan, using ground‐based multi‐axis differential optical absorption spectroscopy during May 2004. Additionally halogen‐catalyzed local surface ozone depletion was observed in the vicinity of the volcano.