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Air quality disturbance zones of the Greater Cochin region (Kerala, India) for the years 2014, 2015, 2016 and 2017 along with air quality assessment and dispersion modelling using in situ measurements and mathematical models, have been investigated in this report. Landsat-8 satellite with OLI and TIRS sensors on board were used for the analysis. The ground based in situ measurements (pollutant parameters) were also obtained from the Kerala state pollution control board. Zonal statistics analysis was performed in various combinations especially air quality disturbance zones with respect to land use/land cover and administrative units for various years. The air quality disturbance zone index (AQDZI) values observed indicated that 38.16% of the study area in 2014 belonged to very good category, 22.94% to good category, 32.37% to moderate category and 6.53% to poor category. In 2015, 56.78% of study area belonged to very good category and 43.221% to good category while in the year 2016 very good category of AQDZI values occupied an area of 45.284% and good category AQDZI values occupied an area of 54.72%. In 2017, 99.834% of the study area belonged to good category and 1.233% to moderate category. Results obtained from zonal statistics revealed that the poor air quality was observed in built up area and good air quality at rubber plantation in all the four selected years. In the case of administrative units, Kochi Corporation experienced poor air quality during all the years studied and Mulanthuruthy grama-panchayath experienced good air quality during most of the years except in 2016.

Extensive use of surfactants in numerous fields resulted in their discharge into various environmental compartments including soil, sediment, and water. Alcohol ethoxysulfates (AES) together with alcohol ethoxylates (AE), alkyl sulfates (AS), and linear alkyl benzene sulfonates (LAS) find wide variety of applications in consumer products including both domestic and industrial applications. Consequently, all these surfactants pose several concerns to both aquatic and human health. In the context of environmental impacts, AES has almost equal importance as that of LAS though the literature on this topic is only emerging. This review provides a detailed overview on the various aspects of the anionic surfactant, AES, such as toxicity of AES, its fate in the ecosystem, technical advancements in the area of identification and quantification, its occurrence and distribution in different environmental compartments spanning across the world, and finally a remark of its potential removal strategy from the environment.

Layer by layer (LbL) assembly can be regarded as an emerging technology for the separation of organic micro-pollutants from water. Direct assembly of polyelectrolytes (PEs) under LbL mode on natural support material is rare. Here we report the integration of LbL to one of the most resourceful support materials that might have an enduring impact on water treatment in color industry. A low-cost adsorbent is developed from chitosan (CHI) and polyacrylic acid (PAA) through LbL deposition on coir fiber (CF) by alternate exposure to their aqueous solutions. Their layer dependent formation is characterized by spectroscopic and microscopic techniques. CHI/PAA multilayer coated coir fiber or simply, layered coir fiber (LCF) showed high loading of cationic and anionic dyes both at acidic and alkaline loading pH. The loading was between 70% and 99% at the acidic pH 3 which is attributed to the binding between LCF and dye molecules by electrostatic and hydrophobic forces. The performance of LCF in presence of NaCl, Na2SO4 and sodium dodecyl sulfate (SDS) in dye solution is discussed. Textile industrial waste water showed significant reduction in dye (81%) content along with COD (84%) and TDS.

Triphenylmethane (TPM) dyes are an important category of dyes with a variety of industrial applications and consequently, these are found in the aquatic environment at relatively higher concentrations. Here, we report the degradation of two important TPM dyes (para rosaniline (PRA) and ethyl violet (EV)) in an aqueous medium by ultrasound which is one among the Advanced Oxidation Processes (AOPs). The main objective of this work is to study the effect of various inorganic ions on the degradation and the product formation of TPM dyes from the sonochemical reactions. Using a typical concentration of 10 ppm dyes and an ultrasonic frequency of 350 kHz and power of 60 W, a complete degradation of EV and PRA was observed with a pseudo first order rate constant of 0.2339 min−1 and 0.1956 min−1, respectively. The product analyses using high-resolution mass spectrometry (LC-Q-TOF-MS) revealed the formation of hydroxylated, de-alkylated, and other collapsed conjugated structure destructed products. The evolution of these products in the presence of various inorganic ions (Cl−, SO42−, NO3−, and CO3−) showed that only carbonate ions had a significant impact on the product evolution. The carbonate ions facilitated the formation of conjugated structure destructed product for both the dyes. This is attributed to the reactivity of carbonate radical, which facilitated the formation of carbon-centered radicals. This carbon-centered radical further undergoes reaction to cause the destruction of conjugated structures. This is confirmed by the identification of the corresponding product peaks in the mass spectra. The scavenging effect of carbonate ions was also reflected in the product study where there is a reduction in the formation of most of the hydroxylated products. One of the major inorganic species in any wastewater is carbonate ions and therefore the present result is very relevant to the understanding of oxidation based treatment protocol.

Indoor dust is an important matrix that exposes humans to a broad spectrum of chemicals. The information on the occurrence of contaminants of emerging concern (CECs), their metabolites, and re-emerging contaminants in indoor dust is rather limited. As the indoor environment is exposed to various chemicals from personal care products, furniture, building materials, machineries and cooking/cleaning products, there is a high chance of the presence of hazardous contaminants in indoor dust. In the present study, dust samples were collected from four different micro indoor environments (photocopying centres, residential houses, classrooms, and ATM cabins) located in an urban environment located in India's southwestern part. The collected samples were subjected to ATR – FTIR and LC-Q-ToF-MS analyses. The ATR – FTIR analysis indicated the presence of aldehydes, anhydrides, carboxylic acids, esters, sulphonic acids, and asbestos – a re-emerging contaminant. A total of 19 compounds were identified from the LC-Q-ToF-MS analysis. These compounds belonged to various classes such as plasticisers, plasticiser metabolites, photoinitiators, personal care products, pharmaceutical intermediates, surfactants, and pesticides. To the best of our knowledge, this is the first report regarding the presence of CECs in indoor environments in Kerala and also the suspected occurrence of pesticides (metaldehyde and ethofumesate) in classroom dust in India. Another important highlight of this work is the demonstration of ATR-FTIR as a complementary technique for LC-Q-ToF-MS in the analysis of indoor pollution while dealing with totally unknown pollutants. These results further highlight the occurrence of probable chemically modified metabolites in the tropical climatic conditions in a microenvironment.

The mechanistic aspects of hydroxyl ( OH) and sulfate radical (SO4 −) induced oxidation of diphenylmethanol (DPM) in aqueous medium has been explored using a combined experimental and theoretical approach. OH initiates the generation of hydroxycyclohexadienyl-type radicals (i) upon reaction with DPM (λmax = 330 nm; k2 = (1.44 ± 0.08) × 1010dm3 mol−1 s−1). Time-dependent density functional theory (TDDFT) calculations revealed an ortho-hydroxylated adduct structure to radical i, which shows comparable absorbance characteristics (λmax = 322 nm). High resolution mass spectrometric (HRMS) studies reveal the existence of mono- and di-hydroxylated compounds of DPM and benzophenone as the main degradation products. Hydroxylated products werederived from the radical i by either a radical-radical disproportion or a bimolecular transformation felicitated by molecular oxygen. Benzophenone (III) is likely originated from the radical cation (iii), generated as a result of one electron oxidation of DPM by OH/SO4 −, by deprotonation followed by electron and proton release.

A detailed investigation on the photocatalytic degradation and mineralization of lignocaine, a local anesthetic, under UV irradiation has been carried out in this study. The dose of TiO2 was optimized initially and was found as 250 mg L−1 for the degradation of 2 mg L−1 concentration of lignocaine. The scavenging experiment using isopropanol and methanol revealed that the degradation is mainly controlled by hydroxyl radical. A fast disappearance of the parent compound (within 1 h) and nearly 75% of mineralization (after 6hr) were observed using this method. The relatively low mineralization efficiency is due to the evolution of various transformation products during the degradation as identified by high-resolution mass spectrometry (LC-Q-TOF-MS). Ten well-separated product peaks were observed in the total ion chromatogram (TIC) for 30 min irradiated sample of lignocaine. Based on the formation of these products, a degradation mechanism is proposed involving mainly hydroxylation, N-de-ethylation, and hydrogen abstraction. As part of mineralization study, the evolution of various inorganic ions was analyzed and the ammonium ion is found as the major inorganic species. A detailed mechanism is proposed for the inorganic ion release as well.

Frustum shaped clay ceramic water filters are being manufactured by the potters of the Thar Desert in India for household use. The clay composite consists of a homogeneous mixture of equal volume of clay and sawdust. A low-cost manual press, to form the clay composite into frustum shape, is developed by the present authors. This article elaborates critical investigation of the specific traditional clay-firing technique used, to achieve the required functionality and material property of the filters. Household based manufacturing of these filters is found to be markedly different from factory based production by firing process. The functional features of the clay ceramic filter, such as microbial filtration rate, flow rate, and compressive strength, are evaluated and presented. An E. coli bacteria removal efficiency of more than 99% is achieved using these clay ceramic water filters. Optimal filtration rates are achieved between ambient temperatures ranging from 30oC - 40oC.

The sonochemical transformation of para-aminosalicylic acid (PAS), a widely used antibiotic and an identified Emerging Pollutant (EP) under the class of Pharmaceuticals and Personal Care Products (PPCPs), have been investigated in aqueous medium. Ultrasound having frequency of 350 kHz and power of 80 W was utilized for the degradation of PAS. A complete degradation (100%) of PAS after 60 min and about 83% of COD removal after 120 min of sonication, were obtained. Fourteen intermediate products were identified using LC–Q-TOF–MS. On a comparison with UV/H2O2 method, it is understood that four products out of fourteen were nitro derivatives which are formed only in the sonolysis, and the rest are from hydroxyl radicals. The involvement of nitrite which is formed from the sonolysis of solution containing PAS, in the formation of the other four nitro products has been established from the control studies. Nitrite ion partially scavenge hydroxyl radical in the course of the reaction to form nitrite radical which is the reactive species for the production of nitro compounds. It is, therefore, proposed that in addition to hydroxyl radical, contribution of in-situ generated nitrite also plays an important role in the sonochemical transformation of PAS.

The present study describes the monitoring of some of the major classes of surfactants in water. The separation, identification, and the quantitative estimation of the compounds were achieved using LC-Q-ToF-MS. The analyses revealed the presence of variety of surfactants including linear alkylbenzene sulfonate (LAS), alcohol ethoxysulfates (AES), and alcohol ethoxylates (AE). Further, emphasis was given to AES as they are one of the most produced and consumed surfactants in the world. And as far as India is concerned, the present study is one of the most significant attempt regarding the identification and quantification of AES. The data obtained during the analysis revealed that the average concentration of AES C12Ex varied from 0.7 to 13.6 μg L−1 while that of C14Ex ranged between 1.3 and 10.4 μg L−1. The risk assessment revealed that higher chain AES are capable of posing medium level risk to the aquatic compartment. In addition, the study also included the physicochemical analysis of water from the selected area. Water was found to be acidic in nature and the salinity, TDS, and EC values were found to be high during the pre-monsoon season. The order of the levels of anionic constituents was of Cl−>SO4 2−SO4 2−>F−>NO3 2− ≅ PO4 2− while that of cations were Na+ > Mg2+ > K+ > Ca2+. Results of correlation analysis showed that statistically negative correlation exists between AES homologs and pH while slight positive correlations were found between AES and other parameters including TDS and EC. The suitability of this water for domestic and agricultural purposes has been examined on the ground of basic quality indices such as the water quality index (WQI) and sodium adsorption ratio (SAR). The WQI measurements also revealed that the water quality of the region falls under the “very poor” category especially during the pre-monsoon season. The study could explore the cumulative share of these canals in the quality impairment of the receiving Vembanad Lake.

Microfiltration (MF) membranes with chitosan/polystyrenesulfonate (CHI/PSS) functional layer coated surface can act as a barrier against emerging contaminants (ECs) in water under low pressure. One (one bilayer) or two functional layers are enough for the removal of lidocaine (LD, 100%) and ibuprofen (IBU, >75%). The effect of various ions, surfactant and humic acid is studied along with the influence of feed pH. Phosphate interferes negatively with the removal efficiency of membrane for IBU and sulfamethoxazole (SMZ). The reusability of the membranes are illustrated by the desorption studies of LD. The extended life of membrane and hence the antifouling nature of the selected ECs indicate its potential in small scale filtration units. Effect of ionic strength in feed and in deposition medium on the rejection percentage is presented. This study shows that various mechanisms depending on the properties of ECs are responsible for the rejection of ECs.

Implications of sulfidized Fe 0 (nFe/FeS) for the abatement of pollutants of various categories are widely established. In this study, degradation of one of the major organic pollutants, benzoic acid (BA), has been performed using persulfate activated with nFe/FeS. Complete degradation of BA and its transformed product, hydroxybenzoic acid, was observed within 6 min. When the degradation was performed at alkaline pH, the degradation decreased to 8% in the case of Fe 0 , but nFe/FeS still showed 100% degradation after 60 min. Iron dissolution and persulfate decomposition in the presence of scavengers showed that both sulfate and hydroxyl radicals were involved in the Fe 0 -persulfate system and that the hydroxyl radicals were the major species in the nFe/FeS-persulfate system. The major degradation pathway of benzoic acid was hydroxylation followed by complete mineralization, as supported by the practical removal of total organic carbons (more than 75% within 15 min). The observed results are promising in using persulfate activated by nFe/FeS for the remediation of various micro-pollutants from a multitude of water sources.

A low saline backwater canal, mainly utilized for domestic and agricultural purposes, has been analyzed for the possible presence of organic micropollutants (OMP) and their potential removal was explored by multilayered microfiltration membranes. The qualitative as well as quantitative analysis were carried out for a span of one year using the technique of liquid chromatography connected with high resolution mass spectrometry (LC-Q-TOF-MS). The identification of the formally unknown compounds was initially done using non-target analysis based on the mass accuracy, isotopic pattern and MS/MS spectral interpretation. Results of the non target screening revealed the presence of 11 OMPs. Five of these OMPs were confirmed using standards; these include chlorophene (CHP), oxybenzone (OXY), N, N-diethyl-meta-toluamide (DEET), N, N-diethyl-benzamide (DEB) and dibutyl phthalate (DBP). Among the confirmed OMPs, the highest concentration was observed for DBP (244.61 ng l−1). The most frequently observed OMP in the study area was DBP while the least was DEB which is an insect repellent as well as a degradation product of DEET. The ecological risk associated with the target compounds has also been analyzed by calculating the risk quotient (RQ) and the results revealed that at the detected levels, these compounds are capable of causing low to medium risk. Low pressure (

Mechanistic aspects of diphenhydramine (DPH) oxidation induced by hydroxyl (•OH) and sulfate (SO4•−) radicals have been explored in detail by pulse radiolysis technique and high resolution mass spectrometry (HRMS). The transient absorption spectrum along with HRMS analysis undoubtedly established the non-position selective hydroxylation of DPH by •OH (a; k2 = (1.08 ± 0.06) × 1010 dm3 mol−1 s−1; λmax: 335 nm) led to various transformation products (i - vii) including isomeric mono (Ia-d), di (IIa-c) and tri (VIIa-e) hydroxylated analogues. On the other hand, SO4•− (specific one electron oxidant) ultimately generates another hydroxylated adduct radical ‘c’ λmax: 330 nm, k2=(5.70 ± 0.03) × 109dm3 mol−1 s−1) which is formed as a result of preferential hydroxylation of initially formed radical cation ‘b’ at ipso position. The mechanism leading to the formation of various transformation products induced by •OH and SO4•− are thoroughly discussed. The mechanistic findings obtained from our studies (especially in the case of less investigated oxidant like SO4•−) are capable to enrich the fundamental understanding on environmentally relevant reactions initiated by •OH and SO4•−.

Ultrasound is known to degrade organic compounds by pyrolysis and by the reaction of free radicals. In this work, sonolytic degradation of an identified water pollutant, coomassie brilliant blue (CBB), has been carried out in pure water as well as in river water. In the case of pure water, 90 % degradation was obtained after 30 min of sonication (350 kHz frequency, 60 W power), whereas in river water, the same efficiency was achieved only after 90 min. The degradation was also performed in the presence of varying concentration of (10–100 mg L−1) inorganic ions such as chloride, sulfate, nitrate, bicarbonate, and carbonate ions which were detected in the river water sample. Higher concentration of chloride enhanced the degradation due to the salting out mechanism. The enhancement of degradation in the presence of nitrate is mainly due to the change in the surface potential at the interface of the cavitating bubble. Bicarbonate ion and carbonate ion enhanced the degradation due to the involvement of carbonate radicals. A possible degradation mechanism is proposed based on the product profile determined by LC-Q-ToF-MS. The low efficiency of degradation in river water compared to that in pure water is likely due to the increased rate of bubble dissolution or escape of bubbles (degassing effect), and the scavenging of •OH by the organic content (high chemical oxygen demand (COD)).

Degradation of benzenesulfonic acid (BSA), the simplest aromatic sulfonic acid with extreme industrial importantance, by sonochemically generated hydroxyl radical ( OH) have been thoroughly investigated. A reasonable reduction (∼50%) in the total organic carbon (TOC) was achieved only after prolonged irradiation (∼275 min, 350 kHz) of ultrasound, although a short irradiation of less than an hour is enough to degrade significant amount of BSA. The degradation efficiency of ultrasound has been reduced in lower and extremely higher frequencies, and upon increasing the pH. An irregular, but continuous, release of sulfate ions was also observed. Further, the release of protons upon the oxidation of BSA consistently reduces the experimental pH to nearly 2. High resolution mass spectrometric (HRMS) analyses reveals the formation of a number of aromatic intermediates, including three mono (Ia-c) and two di (IIa&b) hydroxylated BSA derivatives as the key products in the initial stages of the reaction. Pulse radiolysis studies revealed the generation of hydroxycyclohexadienyl–type radicals, characterized by absorption bands at 320 nm (k2 = (7.16 ± 0.04) × 109 M−1 s−1) and 380 nm, as the immediate intermediates of the reaction. The mechanism(s) leading to the degradation of BSA under sonolytic irradiation conditions along with the effect of various factors, such as the ultrasound frequency and reaction pH, have been explained in detail. The valuable mechanistic aspects obtained from our pulse radiolysis and HRMS studies are essential for the proper implementation of sonochemical techniques into real water purification process and, thus, receives extreme environmental relevance.

The presence of emerging contaminants (ECs) in different aquatic systems may contribute to hazardous effects on aquatic organisms and subsequently on human health. In the present work, liquid chromatography coupled to a quadrupole time of flight mass spectrometer (LC-Q-ToF-MS) was used to identify and quantify a series of ECs in Periyar River in Aluva region, Kerala, India. The water samples were pre concentrated using solid-phase extraction (SPE) prior to analysis. The compounds were probed in both positive and negative ionization mode using electro spray ionization (ESI). Method validations were performed for linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, and precision (intraday and inter day). The ECs were quantified using standard calibration curve. The identified nine ECs include pharmaceuticals, personal care products, steroids, surfactants, and phthalate. A relatively high concentration was observed in the case of 2-dodecyl benzene sulfonic acid (1012 ng/l) and low concentration was observed for lignocaine (4.3 ng/l; since this is below LOQ, the value is only approximate). In addition, we have identified another 28 organic compounds using the technique of non-target analysis out of which seven compounds fall in the category of surfactants. Being the first report on ECs in Periyar River, the data is very important as this river is one of the biggest and important rivers of Kerala having several purification units for drinking water in the province.

Pollution and fate of pollutants in polar region are important topics of investigation in the last several decades. We have analysed sediment samples from Kongsfjorden and Krossfjorden, two sites from Arctic region, and detected a number of emerging contaminants (ECs) using high-resolution mass spectrometry connected to UPLC (LC-Q-ToF-MS). Out of the seven sampling sites selected, bisphenol S (BPS), an identified pollutant and plasticiser, was detected and quantified in three sediment samples from Kongsfjorden (≈ 0.2 ppm). Four major surfactants (decylbenzenesulphonic acid, undecylbenzenesulphonic acid, 2-dodecylbenzenesulphonic acid and tridecylbenzenesulphonic acid) were also identified. A possible metabolite of BPS (sulphur trioxide derivative of BPS) was identified in one of the samples. It is proposed that the presence of ECs is the result of human activities in the region for a long time. To the best our knowledge, this is the first report on the identification of BPS and surfactants in the Arctic region.

The heterogeneous catalytic degradation of a model azo dye, acid red 1 (AR1), initiated by zero valent iron nanoparticles (ZVINP), and its synergic effect with ultrasound (US) have been investigated in the present study. The treatment of AR1 using ZVINP at pH 3 showed maximum efficiency in terms of colour removal (53.0%) and mineralization (48.5% TOC reduction) after 25 min of reaction. However, the coupling of this system with US showed an enhanced efficiency against the decolourization and mineralization of AR1. More than 95% colour removal was achieved within 5 min in the case of US/ZVINP system. Around 55% TOC reduction suggests the conversion of the parent molecules in to aromatic transformed products, and it is further supported by LC-Q-TOF analysis. The remarkably higher efficiency in the coupled system is attributed to the synergic effect of ZVINPs and ultrasound. The highest degradation rates observed at highly acidic (pH 3) and alkaline pH (pH 9) suggests that different mechanisms are operating at both pH. The products identified gave some insight into the mechanism. The ZVINPs prepared in the present study was easily recoverable (and reusable) and hence may be considered as an effective replacement for the conventional Fenton's reagent.

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Environmental contextPerchlorate from rocket fuel plants or firework manufacturing units can seriously contaminate drinking water. We developed a separation skin on a microfiltration membrane and on sand that can remove perchlorate from water in the presence of competing ions. This method is suitable for a domestic water purification unit selective for perchlorate removal. AbstractThis study reports an interactive separation of perchlorate (ClO4−) by polyethyleneimine (PEI) and poly (styrene sulfonate) (PSS) deposited on a microfiltration membrane and on sand surfaces. The variation of the interaction with respect to deposition and feed variables was assessed. The 9 bilayered ((PEI/PSS) 0.15M NaCl, pH 6)) membranes showed a ClO4− rejection of ~80%. An increase in the feed concentration to 25mgL−1 reduced the rejection to 58%. With a feed pH from 4 to 10, the rejection varied between almost 100% and 16%. The presence of ions reduced the rejection percentage of ClO4− with the interference by the ions in the order of SO42−>HCO3−>NO3−>Cl−. The interference is attributed to the characteristics of the competing ions and the nature of the multilayers. A positive impact of post-treatment (98%) and capping layers on rejection percentage (80% to nearly complete) for synthetic and ClO4− contaminated field water samples is clearly established. The presence of competing ions is also accounted for by a capped membrane system. The selectivity of the competing ions increases with capping layers of 1M NaCl in the order of HCO3−>NO3−>SO42−. In the field water samples up to a SO42− concentration of 3.0mgL−1, the capping layers with 0.4M NaCl result in a near complete rejection of ClO4−, whereas further enhancement requires a capping layer of 1M NaCl. A sand filtration system was developed by incorporating the pre-optimised polyelectrolyte multilayer on sand. Deposition of a single bilayered PEI/PSS multilayer on sand effectively (nearly completely) removes ClO4−.

Environmental contextRanitidine, a widely prescribed antiulcer drug commonly found in surface waters, has been identified as an emerging contaminant due to its toxicity and the enhanced toxicity displayed by its transformation products. Mechanisms for the formation of ranitidine transformation products and their degradation pathways induced by UV oxidation processes are presented. This work provides insight into treatment processes to remove these toxic chemicals from environmental water bodies. AbstractThe transformation products (TPs) of pharmaceuticals formed during advanced oxidation processes (AOPs) are of great significance, but there are still gaps in our knowledge regarding the persistence of such compounds in the water matrices, their impact on human health and the applicability of such techniques during water treatment processes. Ranitidine (RAN), a highly prescribed gastrointestinal drug, has been widely detected in various surface waters and experiments, along with its TPs, which show enhanced toxicity. The present study analyses the TPs formed from the degradation of RAN in aqueous solution induced by three AOPs; namely UV-photolysis, UV/peroxodisulfate (PDS) and sonolysis. The degradations followed pseudo first-order kinetics, with removal efficiencies of 99.8, 100 and 98.8% after 60min under UV photolysis, UV/PDS, and sonolysis, respectively, with a corresponding decrease in chemical oxygen demand (COD) of 25, 100 and 75%. Structures of the main TPs were elucidated by using LC-Q-ToF-MS in positive mode, and possible degradation pathways are proposed which mainly involved C-N and C-H bond cleavage, hydroxylation and reduction of nitro groups. Possible mechanisms for the formation of the identified TPs (elucidated by using electrospray ionisation–collisionally induced dissociation) support their structural assignments. Seven out of the 11 TPs presented here (namely TP-1, TP-4, TP-5, TP-6, TP-7, TP-9 and TP-10) were not reported in previous studies of RAN using any other AOPs, while four (m/z 331, 270, 288 and 286) were found to retain the NO2 group, which might contribute to the formation of halonitromethanes (HNMs) during chlorination of drinking water. Interestingly, we identified an additional sonolysis product, TP-3, whose formation can only be rationalised by invoking ozone.