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Abstract The occurrence of algae bloom would lead to the release of algae-derived organic matter (AOM) and then alter the abundance and behavior of dissolved organic matter (DOM) in aquatic ecosystems. In this study, the characteristics and photodegradation of AOM, naturally occurring organic matter (NOM) derived from soil and plants and their mixtures were explored to reveal the potential interactions between AOM and NOM in water. Results indicated that the protein-like components from AOM and the humic-like components from SRNOM took place inter-component interactions in the AOM-NOM mixtures. Meanwhile, application of two-dimensional Fourier transform infrared correlation spectroscopic (2D-FTIR-COS) analysis revealed that carboxylic C=O had a high priority to bind with other functional groups (e.g., phenolic-OH, polysaccharides C-O, amideⅡC-N/N-H and celluloses C-H). More crucially, it was found that the AOM-NOM mixtures subjected to a very different photodegradation behavior to their end-members (i.e., AOM and NOM), likely because of the occurrence of AOM-NOM interactions as well as their roles in mediating the yield of reactive oxygen species. For instance, the presence of AOM led to increased photodegradation degrees of the chromophoric fraction in NOM. In contrast, the NOM did not exhibit any photosensitization role in the photodegradation of the proteins from AOM. This study has potential implications for our understanding of the carbon cycling in anthropogenically impacted aquatic systems such as inland rivers and lakes. Graphical abstract Image 1 Highlights • Inter-component interactions were found in the AOM-NOM mixture. • Carboxylic C=O had a high priority to bind with other functional groups. • The presence of AOM led to increased photodegradation degrees of NOM. • The SRNOM did not play any photosensitization role in the photodegradation of AOM. • The interaction of AOM and NOM mediated the production of ROS. [ABSTRACT FROM AUTHOR]

Highlights: [•] Bi2O3/Bi2O2CO3/Sr6Bi2O9 can degrade SMX efficiently using visible light. [•] 36% of TOC reduction was achieved after 120min treatment. [•] The main mineralization products were confirmed. [•] Formation of O2 − was evidenced by using ESR and a chemiluminescent probe. [Copyright &y& Elsevier]

Highlights: [•] A novel nano materials Sr-doped β-Bi2O3 (Sr-Bi2O3) is successfully prepared. [•] The degradation of TC follows the pseudo-first-order kinetics by Sr-Bi2O3. [•] It is an effective and eco-friendly method to eliminate TC by Sr-Bi2O3. [•] A photochemical degradation mechanism of TC is proposed. [•] The intermediates formed by Sr-Bi2O3 photocatalysis have lower toxicity. [ABSTRACT FROM AUTHOR]

Abstract: A quantitative structure–property relationship (QSPR) model which could predict photodegradation half-lives (t 1/2) of chlorinated polycyclic aromatic hydrocarbons (ClPAHs) associated with particulates in the atmosphere was developed by applying quantum chemical parameters computed with quantum chemical PM3 algorithm and using a partial least squares (PLS) algorithm. The cross-validated Q 2 cum value for the optimal QSPR model is 0.960, indicating a good predictive capability for log t 1/2 values of ClPAHs. The QSPR results show that the main factors affecting log t 1/2 values of ClPAHs are the energy of the second highest occupied molecular orbital (E LUMO−1), the energy of the second highest occupied molecular orbital (E HOMO+1), average molecular polarizability (α), the most positive net atomic charges on a hydrogen atom (), E LUMO+E HOMO, E LUMO−E HOMO, and (E LUMO−E HOMO)2. ClPAHs with high E LUMO−1, E HOMO+1, E LUMO−E HOMO, and (E LUMO−E HOMO)2 values tend to photolyze slowly in the atmosphere. In contrast, increasing E LUMO, α, and values leads to the increase of photodegradation rates. [Copyright &y& Elsevier]HOMO, α, and values leads to the increase of photodegradation rates. [Copyright &y& Elsevier]

Abstract: By partial least squares (PLS) regression, quantitative structure–property relationship (QSPR) models were developed for photodegradation rates (k p) and quantum yields (Φ) of polybrominated diphenyl ethers (PBDEs) in methanol/water (8:2), and photodegradation rates in pure methanol by UV light in the sunlight region, respectively. Quantum chemical descriptors computed by PM3 Hamiltonian were used as predictor variables. The cross-validated values for three optimal QSPR models of PBDEs are above 0.90 (remarkably higher 0.50), indicating good predictive abilities for log k p and log Φ values of PBDEs. The QSPR results show that log k p values of PBDEs in methanol/water (8:2) and in pure methanol are governed by different molecular structural descriptors, respectively, which implies that photodegradation rates of PBDEs are affected by the characteristics of solution in which it takes place. [Copyright &y& Elsevier]

Photodegradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) sorbed on surfaces of spruce (Picea abies (L.) Karst.) needles was investigated. The role of sunlight and, in particular, the role of short wavelength UV-B radiation were studied in a sun simulator under controlled environmental conditions. The photodegradation of PCDD/Fs and PAHs follows first-order kinetics. Simulated sunlight containing UV-B induced two phases of photodegradation kinetics for PCDD/Fs, whereas no distinct phases of the kinetics were observed for PAHs. UV-B radiation plays a much more important role on the photodegradation for PCDD/Fs than that for PAHs. Direct photolysis dominates the photodegradation of PCDD/Fs and PAHs. [Copyright &y& Elsevier]

Fourteen sediment samples with different content of Fe2O3 were collected from the lower reaches of the Liao River in China. The photodegradation of lindane on the surfaces of these sediments was investigated to observe the effects of Fe2O3 and other photoinducable substances, such as TiO2 and organic substances, on photodegradation of lindane. A partial least-squares (PLS) analysis model was developed to find out the statistical relationship between the photodegradation and the contents of these photoinducable substances. It was concluded from the PLS analysis that inorganic carbon and organic carbon have negative effects, whereas Fe2O3 and TiO2 accelerate the photodegradation of lindane in the sediment samples when 365 nm UV light was used as light source. In all cases of the experiments, the photodegradation of lindane in the sediment samples were fitted for pseudo-first-order kinetics. [Copyright &y& Elsevier]

Abstract: Nanoporous zirconia electrospun fiber mats (NZEFM) have been prepared by an electrospinning process using nonionic F108 as a pore-forming agent. This nonaqueous synthesis route has been employed to fabricate a stable “building block” porous structure inside the nano-scale fibers. The mats composed of individual fibers proved to be robust after calcination at up to 450°C or stirring in water. The photocatalytic activity of NZEFM is apparently higher than that of commercial zirconia powder for the degradation of methyl orange in aqueous solution. Moreover, amorphous NZEFM mixed with the tetragonal phase obtained at 450°C proved to be more efficient than the monoclinic phase NZEFM obtained at 900°C. Various dyes could be degraded by NZEFM under UV light irradiation. The highly photocatalytic activity of NZEFM could be attributed to its high specific surface area and nanoporous “building block” structure made up of stacked zirconia nanoparticles. [Copyright &y& Elsevier]

Dissolved organic matter (DOM) is the most important light absorber that may induce indirect photolytic transformation of organic pollutants in natural waters. In this study, effects of DOM derived from freshwater and seawater on the photodegradation of three antiviral drugs acyclovir, lamivudine and zidovudine were investigated. Results show that the photodegradation of acyclovir is promoted mainly by excited triplet states DOM (3DOM*), and the photodegradation of lamivudine is accelerated by 3DOM*, •OH and 1O 2 together; however, the photodegradation of zidovudine is inhibited by DOM mainly via light screening. Compared with DOM from freshwater, promotion effect of DOM extracted from seawater (SDOM) on the photodegradation of acyclovir and lamivudine is weaker, which is attributed to lower productivity of reactive intermediates. On the other hand, inhibitory effect of SDOM on the photodegradation of zidovudine is also weaker, which is due to weaker light screening caused by lower light absorption. Photodegradation half-lives of the three antiviral drugs are predicted to be all more than 20 days in freshwater and seawater bodies of the Yellow River estuarine region. These findings are significant for understanding the phototransformation processes of antiviral drugs and other organic pollutants in estuarine and coastal regions. Image 1 • Seawater DOM has low rate of light absorption compared with freshwater DOM. • Triplet-excited DOM is largely responsible for photodegradation of acyclovir. • Seawater DOM shows weak inhibitory effect on photodegradation of zidovudine. • Photodegradation half-lives of antiviral drugs are more than 20 days. [ABSTRACT FROM AUTHOR]

Abstract Degradation of perfluorooctanoic acid (PFOA) is important because of its global distribution, persistence and toxicity to organisms. In this work, the Pb BiFeO 3 photocatalyst was prepared by the hydrothermal method. The effect of doping amount of reduced graphene oxide (rGO) on the decomposition of PFOA was investigated under 254 nm UV light. The results indicated that 100 mg L−1 Pb BiFeO 3 with 0.5 wt% rGO exhibited the highest degradation efficiency for 50 mg L−1 PFOA at pH = 2.0 from aqueous solution. The removal rate of PFOA reached 69.6% after 8 h UV irradiation under the optimal conditions (PFOA concentration of 50 mg L−1, Pb BiFeO 3 /0.5% rGO concentration of 100 mg L−1, and pH of 2.0). The total organic carbon removal rate and defluorination rate were 28.0% and 37.6%, respectively. During the degradation process, four major intermediates with shorter chain length than PFOA (∼C4 C7) were identified. The mechanism responsible for PFOA decomposition was supposed that OH attacked PFOA to form perfluoroalkyl alcohol and then was transferred to perfluoroalkyl fluoride which can easily undergo hydrolysis to form shorter-chain perfluorocarboxylic acids than PFOA. This indicated that the photocatalytic degradation of PFOA was an oxidation process through stepwise losing of CF 2 group. Graphical abstract Image 1 Highlights • Photocatalytic degradation of PFOA by Pb BiFeO 3 /rGO catalyst is investigated. • The optimal conditions for PFOA photocatalytic degradation are determined. • The TOC removal rate of PFOA in the optimal conditions is 28.0%. • C 4 C 7 shorter-chain perfluorocarboxylic acids and F−1 are major intermediates. • OH attacked PFOA and the degradation proceed by stepwise losing a CF 2 group. [ABSTRACT FROM AUTHOR]

• Differences and similarities between ice and aqueous photochemistry were revealed. • Photodegradation kinetics are clearly influenced by the matrix phases, ice and water. • Different photodegradable potential orders between in the two phases were discovered. • Unidentical effects of key constituents in the two phases account for the differences. • Ice photolysis shows fewer products / simpler pathways compared to water photolysis. The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry. Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs, 2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL), which are newly recognized contaminants in the wider environment including colder regions. Interestingly, their photodegradation kinetics were clearly influenced by whether they reside in ice or water. Under the same simulated solar irradiation (λ > 290 nm), OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing. Furthermore, the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in 'seawater' ice (k = (11.4 ± 1.0) × 10−2 min−1) followed by 'pure-water' ice ((8.7 ± 0.4) × 10−2 min−1) and 'freshwater' ice ((8.0 ± 0.7) × 10−2 min−1). The presence of dissolved constituents (specifically Cl−, NO 3 −, Fe(III) and humic acid) influences the phototransformation kinetics, either enhancing or suppressing phototransformation, but this is based on the quantity of the constituent present in the matrixes, the specific OHFL isomer and the matrix type (e.g., ice or aqueous solution). Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry. Ice phototransformation exhibited fewer by-products and 'simpler' pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice. These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice. [Display omitted] [ABSTRACT FROM AUTHOR]

LaFeO 3 /Bi 3 NbO 7 p-n heterojunction photocatalysts were prepared successfully through an in-situ growth method. The phase structure, optical property, morphology and microstructures of the obtained samples were studied by X-Ray diffractometer (XRD), Ultraviolet–visible absorption spectrum (UV–vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM). The visible light responsive photocatalytic activity of as-obtained samples were investigated by the photo-reduction of Cr (Ⅵ). The effects of preparation conditions (proportion of BNO/LFO and temperature) on the activity were studied. Results showed that the as-obtained BNO-LFO-200-5 composite behaved the best photocatalytic activity (with rate constant of 0.0212 min−1) among all the obtained samples. The rate constant was about 42.4-times and 17.7-times as that of pristine BNO (0.0005 min−1) and LFO (0.0012 min−1), respectively. The enhanced photocatalytic property of the as-prepare LaFeO 3 /Bi 3 NbO 7 composites can be ascribed to the formation of p-n junction between BNO and LFO, which significantly increased the separation efficiency of photo-excited electron-holes. • A novel LaFeO 3 –Bi 3 NbO 7 p-n heterojunction photocatalyst was prepared for the first time. • The composites exhibited significantly enhanced activity for Cr (Ⅵ) photocatalytic reduction. • The heterojunctions promote the photo-generated carriers transmission and separation. [ABSTRACT FROM AUTHOR]

Sunlight-initiated photodegradation has a great impact on the composition and properties of natural dissolved organic matter (DOM) in aquatic environments, which potentially changes the behavior and roles of DOM in water treatment facilities. Here, we explored the effect of sunlight irradiation on membrane fouling behavior of two natural DOM (i.e., Aldrich humic acid (AHA) and Suwannee River DOM (SRNOM)), particularly in the presence of calcium ion (Ca(II)). Results showed that a long-term exposure (3 months) to sunlight during the summer led to decreases in the chromophores and molecular size of both DOM. The characterization by UV–vis spectral parameter D Slope 350–400 (the slope of the log-transformed absorbance spectra in the range of 350–400 nm) indicated that sunlight-exposed DOM had a weaker Ca(II)-binding ability than unirradiated DOM, which could be attributable to the photochemically induced loss of carboxyl and phenolic groups. Additionally, AHA was found to be more susceptible to sunlight irradiation and Ca(II) addition than SRNOM, likely due to its higher aromaticity. Crucially, dead-end ultrafiltration tests showed that sunlight exposure of both AHA and SRNOM can reduce their fouling potential in the absence of Ca(II) and the presence of low Ca(II) (0.4 mM). In contrast, the addition of higher Ca(II) concentrations (2 and 3.6 mM) led to an increase in their fouling propensities. Overall, sunlight exposure can greatly alter the fouling behavior of natural DOM. This study provides a nexus between the naturally occurring transformation of DOM and its behavior (i.e., membrane fouling) in water treatment facilities. [ABSTRACT FROM AUTHOR]

[Display omitted] • The photodegradation of PRO can be enhanced in river water under natural sunlight. • 3DOM* is the main reactive species responsible for the photodegradation of PRO. • DOM with higher steady-state concentration of 3DOM* has higher reactivity. • The main degradation pathways of PRO are hydroxylation and dehydration. • The degradation product of PRO is more toxic to aquatic organisms than PRO itself. The widespread use of propranolol (PRO) has led to its detection in all types of natural water bodies, and it is hazardous to both aquatic organisms and humans. In this study, the photochemical transformation of PRO in the natural environment was investigated using both simulated and outdoor light experiments. The photodegradation of PRO was found to be faster in Pearl river water and the dissolved organic matter (DOM) solutions than that in pure water under sunlight irradiation. Quenching experiments show that the excited triplet states DOM (3DOM*) played a major role while ·OH and 1O 2 played minor roles in PRO degradation. The secondary reaction rate constants of 3DOM* with PRO were determined to be (4.32 ∼ 6.38) × 108 M−1 s−1. DOM with high steady-state concentrations of the generated reactive species has higher photochemical reactivity for PRO photodegradation. Total of seven products were identified in in pure water, Pearl River water and three DOM solutions. The degradation of PRO can be mainly through hydroxyl addition, dehydration, naphthalene removal and isopropyl removal reactions. The reaction sites predicted by frontier electronic density calculations can further infer degradation pathways. The ecotoxicity of degradation products was found to be decreased relative to PRO through Ecological Structure Activity Relationship (ECOSAR) program. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel p-n/Z-scheme dual heterojunction photocatalyst was prepared. • The dual heterojunction promoted photogenerated electron directional transfer. • Redox ability was enhanced due to the formation of built-in electric field. • O 2 •− and •OH played dominant roles in TBBPA degradation. Tetrabromobisphenol A (TBBPA), as a typical brominated flame retardant, has been confirmed to pose potential threats for human health and developed into a global pollutant. Graphitic carbon nitride (g-C 3 N 4) is the most used catalyst for refractory organic pollutants removal, but the weak conductivity and quick recombination of photogenerated carries restrict its practical application. To improve the photocatalytic activity of pristine g-C 3 N 4 , a p-n/Z-scheme dual heterojunction photocatalyst (BFC) was designed and prepared by introducing black phosphorus nanosheets and FeSe 2 into porous g-C 3 N 4 (CN). Compared to traditional heterojunction catalysts, BFC not only can promote photogenerated carriers directed migration and effective separation, but also can retain higher redox potential for simultaneous generating O 2 − and OH, which are due to the synergistic effects of built-in electric field formation in p-n heterojunction and bandgap structure optimization by Z-scheme heterojunction. Above advantages promote BFC to achieve 100% TBBPA degradation efficiency in 40 min and 22.6% debromination efficiency in 60 min under visible light irradiation. The superfast reaction rate constant (0.143 min−1) is almost 10 times higher than that of pristine CN. This study proposes a facile design strategy to construct heterojunction photocatalysts and provides an alternative method to rapidly remove TBBPA in water. [ABSTRACT FROM AUTHOR]

Antihypertensive propranolol (PRO) is frequently detected in surface waters and has adverse effects on aquatic organisms. In this study, its photochemical fate in surface water with the aspect of kinetics, products and toxicity were investigated employing steady-state photochemistry experiments and ecotoxicity tests. The results showed that photodegradation of PRO was enhanced in river water than that in phosphate buffer where dissolved organic matter (DOM), NO 3 −, and HCO 3 − played important roles. DOM accelerated the photodegradation mainly through generation of excited triplet-state DOM while NO 3 − played dual roles in the photodegradation. The reaction between excited triplet-state PRO and HCO 3 − can generate carbonate radical (CO 3 ·-) to promote the photodegradation. The second-order reaction rate constant between PRO and CO 3 ·- was determined to be (3.4 ± 0.8) × 108 M−1 s−1. Eight photodegradation products were identified in the studied river water sample. Finally, the toxicity evaluated by Vibrio fischeri increased after photodegradation and three photodegradation products were responsible for the increasing toxicity, which was concluded from the significant correlation between toxicity parameters and quantity of the photodegradation products. [Display omitted] • Photodegradation rate of PRO is faster in river water relative to pure water. • Both river water DOM and NO 3 − show enhancement effects on PRO photodegradation. • CO 3.•- is responsible for promoting the photodegradation of PRO in HCO 3 − solution. • Eight photodegradation products are identified in the river water. • The photodegradation of PRO enhances their toxicity against vibrio fischeri. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe2+/Fe3+ cycle system of FeO x -BC at dual-defective carbon nitride is constructed. • Dual-defects can narrow band structure and inhibit charge carrier recombination. • KCN plays a vital role in Fe2+/Fe3+ cycle system in the FeO x -BC/KCN. • FeO x -BC/KCN presents an excellent photocatalytic degradation of OFLO. To improve charge carrier transfer in graphite carbon nitride (CN)-based composites, a cycle system at KCl-assisted carbon nitride (KCN) interfaces via growth of FeO x nanowalls inside biochar (FeO x -BC/KCN) was constructed, which achieved an excellent performance for ofloxacin (OFLO) degradation (100%, 30 min) and more than 30% of defluorination rate under visible-light irradiation. The KCN presented dual-defective structures, nitrogen vacancy and cyano group, which could narrow its band gap and modulate the electron structure. XPS and Mössbauer spectra proved that an electron channel between KCN and FeO x -BC was formed, where highly conductive BC accelerated the photogenerated electron transfer from KCN to FeO x nanowalls and these electrons participated in a Fe2+/Fe3+ reversible cycle system to realize effective utilization. Moreover, the degradation mechanisms and pathways of OFLO over the FeO x -BC/KCN were investigated. This study provides an alternative strategy to improve charge carrier transfer in CN-based photocatalysts through construction of a facile cycle system. [ABSTRACT FROM AUTHOR]

Acebutolol (ACE) has been widely used for the treatment of cardiovascular disorders, and its photochemical fate in natural waters is a matter of concern due to its ubiquitous occurrence and its toxicity to aquatic organisms. In this study, the photodegradation of ACE in river water and synthetic waters were investigated under simulated sunlight irradiation. The results demonstrated that ACE photodegradation rate in river water was 3.2 times higher than that in pure water. Then the influences of HCO 3 −, NO 3 − and DOM on ACE photolysis were investigated under their concentrations similar with the ones in river water. ACE photodegradation was significantly enhanced in the presence of HCO 3 − alone, and the scavenging experiments and the electron paramagnetic resonance experiments together proved that HCO 3 − could be oxidized by triplet-excited state of ACE to generate CO 3 •-, which subsequently played a key role in ACE degradation. The presence of both NO 3 − and DOM also increased the ACE photodegradation rates, and •OH and 3DOM* were found to be involved in the degradation. In addition, when DOM was added to a solution with HCO 3 −, the enhancement effect of HCO 3 − on ACE photodegradation was weakened due to the scavenging of CO 3 •- by DOM combined with the light screening effect of DOM. [Display omitted] • Both direct and indirect photodegradation of ACE can occur in river water. • The presence of HCO 3 − alone greatly enhances the photodegradation of ACE. • HCO 3 − can be photosensitized by triplet excited state of ACE to generate CO 3.•-. • The presence of NO 3 − and DOM both can promote the photodegradation of ACE. • Addition of DOM inhibits the photosensitized degradation of ACE by HCO 3 −. [ABSTRACT FROM AUTHOR]

The widespread use of antibiotics in drug therapy and agriculture has seriously polluted the aquatic environment. Bismuth tungstate (Bi 2 WO 6) is a new and efficient visible-light catalyst that is simple to prepare, non-toxic, stable, and corrosion resistant. Nonetheless, its efficiency has remained limited, and erbium (Er) mixing has been tested to address this. Here, a new Er3+-mixed Bi 2 WO 6 photocatalyst was successfully prepared through the one-step hydrothermal method; pigments were characterized via XRD, SEM, BET, XPS, Uv-vis, PL and EIS. The results showed that the 16% Er3+-Bi 2 WO 6 photocatalyst is a 250 nm flower-like nanosheet with a specific surface area of 67.1 m2/g and bandgap (Eg) of 2.35 eV, which provides the basis for superior performance. When the concentration of the catalyst was 0.4 g/L, 94.58% of the tetracycline (TC) solution (initial concentration of 10 mg/L) degraded within 60 min under visible light irradiation (λ ≥ 420 nm). ESR and LC-MS were used to identify the free radicals and intermediates for the degradation of TC pollutants; a photocatalytic degradation system and pathway were proposed. This solar-driven system will ultimately reduce resource consumption, providing a sustainable and energy-saving environmental decontamination strategy. [Display omitted] • A novel Er3+-Bi 2 WO 6 photocatalyst for layered nanosheets successfully prepared. • 16% Er3+-Bi 2 WO 6 substantially improved the tetracycline-degrading activity (94.58%). • Photocatalytic degradation mechanism and pathway of TC revealed. • A novel, sustainable and energy-saving strategy for the removal of environmental pollutants (Tetracycline hydrochloride). [ABSTRACT FROM AUTHOR]

Propranolol (PRO) is frequently detected in estuarine and coastal waters, which has adverse effects on estuarine and coastal ecosystems. In this study, the effects of halide ions and DOM from estuarine and coastal waters on the photochemical transformation of PRO were investigated. The results demonstrated that the presence of Br- alone exhibited slight effect on photochemical transformation of PRO, while photodegradation rates of PRO increased with the addition of 0.1–0.54 M Cl-. The quenching experiments and the laser flash photolysis experiments together demonstrated the generation of Cl 2 •— in the photolytic systems. Cl 2 •— is possibly produced through the charge separation of exciplex of 3PRO* and Cl- rather than via direct oxidation of Cl-. Additional experiments indicated that addition of seawater DOM inhibited the halide ions-sensitized photodegradation rates of PRO, which may be due to the quenching of Cl 2 •— by phenolic substances in DOM molecules. Compared with pure water, three new photochemical intermediates were identified in the presence of DOM or Cl-. The direct photolysis of PRO mainly reacted by hydroxyl additions, hydroxyl elimination and de-propylation, whereas electron transfer coupled with H-abstraction by Cl 2 •— and 3DOM* was proposed as the primary role for PRO degradation in the presence of Cl- or DOM. [Display omitted] • Cl- significantly promotes PRO photodegradation under simulated sunlight. • The presence of Br- alone has negligible effects on the photodegradation of PRO. • Cl 2 •— contributes to the enhancement of PRO degradation in Cl- solutions. • Addition of DOM inhibits the photosensitized degradation of PRO by halide ions. • Electron transfer and H-abstraction products are identified in Cl-/DOM solutions. [ABSTRACT FROM AUTHOR]

• HCO 3 − significantly promotes SOT photodegradation under simulated sunlight. • Addition of HCO 3 − has negligible effects on the degradation of CAR and ARO. • Seawater DOM enhances HCO 3 −-induced photodegradation of SOT. • Freshwater DOM decreases HCO 3 −-induced photodegradation rate of SOT. • CO 3 •− contributes to the enhancement of SOT degradation in HCO 3 − solutions. The impact of HCO 3 − on the photodegradation of β-blockers was investigated under simulated sunlight irradiation. The results show that in the presence of HCO 3 −, the photodegradation rates increase significantly for sotalol (SOT), whereas no effects on the degradation of carvedilol and arotinolol are observed. Using quenching experiments, electron paramagnetic resonance spectra and degradation product determination, we demonstrate that carbonate radical (CO 3 •−) is formed by direct oxidation of HCO 3 − by triplet-excited SOT (3SOT*) and plays a significant role in SOT photodegradation. Competition kinetics experiments show that the three β-blockers all have high second-order rate constants (107–108 M−1 s−1) for the reaction with CO 3 •−. However, only 3SOT* has a higher reduction potential that can oxidize HCO 3 − to produce CO 3 •−. Thus, enhanced SOT removal rates in the presence of HCO 3 − were observed. In addition, the results show that seawater DOM could increase HCO 3 −-induced photodegradation of SOT, whereas SRNOM mainly behaves as a CO 3 •− quencher and decreases the removal rate of SOT. The results underscore the role of HCO 3 − in limiting the persistence of organic pollutants like SOT in sunlit natural waters, and especially in marine and coastal waters. [Display omitted] [ABSTRACT FROM AUTHOR]

Nebivolol (NEB) is widely used for the treatment of hypertension and chronic heart failure and has become an ubiquitous emerging organic pollutant. It has been shown to undergo direct photolysis, but the role of DOM in its degradation kinetics and mechanism is not well understood. In this study, we studied the photochemical behavior of NEB in the presence of seawater DOM (SW-DOM) and freshwater DOM (SRNOM) under simulated sunlight irradiation. SW-DOM had a promotion effect on NEB photodegradation, whereas SRNOM retarded its photolytic transformation. After eliminating the influence of light screening, we found that the indirect photodegradation rate of NEB in the presence of SRNOM was lower than that in the presence of SW-DOM. Results show that the indirect photodegradation pathway occurred by reaction with triplet-excited DOM (3DOM*). The second-order rate constants for 3SW-DOM* and 3SRNOM* reaction with NEB are 3.7 × 109 M−1 s−1 and 3.7 × 108 M−1 s−1, respectively. The electron donating capacity of SRNOM is higher than that of SW-DOM, indicating that SRNOM may contain more activated phenolic moieties. SRNOM may thus have higher antioxidant activity, leading a higher inhibitory effect on NEB photodegradation. A total of six degradation products were identified in the absence and presence of DOM by HPLC-ESI-MS/MS. The substitution of F by OH-groups and further oxidation a OH-group in the lateral chain to a ketone, and cleavage of N–C bond by the attack of 3DOM* are here proposed as the main degradation pathways. Image 1 • Seawater DOM promotes NEB photodegradation under simulated sunlight irradiation. • Freshwater DOM retards the photodegradation of NEB. • 3DOM* contributes to the indirect photodegradation of NEB. • Photoreactivity of seawater 3DOM* to NEB is higher than that of freshwater 3DOM*. • Three new photoproducts are identified in DOM solutions compared to pure water. [ABSTRACT FROM AUTHOR]