Indirect photodegradation of pharmaceutical and personal care products in dissolved black carbon solution: The role of microheterogeneous distribution of hydroxyl radical and sorption.

Dissolved black carbon (DBC) with a hyperconjugated structure is ubiquitous in nature, and plays a crucial role in the migration and transformation of environmental contaminants due to its prominent properties of accepting electrons and sorption. However, little is known about the DBC-induced phototransformation of pharmaceutical and personal care products (PPCPs) in natural waters. Herein, the photodegradation kinetics of PPCPs were investigated in DBC solution under simulated solar irradiation and compared with those in Suwannee River natural organic matter (SRNOM) solution.

Microheterogeneous Triplet Oxidation of Hydrophobic Organic Contaminants in Dissolved Black Carbon Solutions under Simulated Solar Irradiation.

Dissolved black carbon (DBC) is proven to accelerate the triplet-mediated photodegradation of hydrophobic organic contaminants (HOCs). However, its photosensitization mechanisms are not clear. In this study, five HOCs including 2,4,6-trimethylphenol, ,-dimethylaniline, 17β-estradiol, 17α-ethinylestradiol, and bisphenol A were selected as model compounds to explore the triplet-mediated phototransformation of HOCs in illuminated DBC solutions.

Role of NOM in the Photolysis of Chlorine and the Formation of Reactive Species in the Solar/Chlorine System.

The solar/chlorine system has been proposed as a novel advanced oxidation process (AOP) for efficient pollutant degradation and water disinfection by producing a series of reactive species including hydroxyl radicals (HO), chlorine radicals (Cl), and so forth. In this study, the role of natural organic matter (NOM) in the photolysis of free available chlorine (FAC) and the formation of HO and Cl in the solar/chlorine system was investigated employing nitrobenzene and benzoic acid as selective chemical probes. The decay rate of FAC was significantly accelerated in the presence of NOM at pH 5.

Triplet Photochemistry of Dissolved Black Carbon and Its Effects on the Photochemical Formation of Reactive Oxygen Species.

Dissolved black carbon (DBC) is an important component of dissolved organic matter pool; however, its photochemical properties are not fully understood. In this study, we determined the excited triplet-state quantum yields of DBC (DBC*) and O quantum yields (Φ) of six diverse DBCs using sorbic alcohol, 2,4,6-trimethylphenol (TMP), and furfuryl alcohol and compared the results with quantum yields of reference natural organic matters (NOMs). The average Φ of six DBCs (4.

Kinetic Consideration of Photochemical Formation and Decay of Superoxide Radical in Dissolved Organic Matter Solutions.

The photochemical formation and decay rates of superoxide radical ions (O) in irradiated dissolved organic matter (DOM) solutions were directly determined by the chemiluminescent method. Under irradiation, uncatalyzed and catalyzed O dismutation account for ∼25% of the total O degradation in air-saturated DOM solutions. Light-induced O loss, which does not produce HO, was observed.

Overview of the Phototransformation of Wastewater Effluents by High-Resolution Mass Spectrometry.

Photochemical transformation driven by sunlight is one of the most important natural processes for organic contaminant attenuation. In the current study, statistical analysis-assisted high-resolution mass spectrometry was employed to investigate the phototransformation of nontarget features in wastewater effluents under various radical quenching/enhancing conditions. A total of 9694 nontarget features were extracted from the effluents, including photoresistant features, photolabile features, and transformation products.

Assessing the contribution of hydroxylation species in the photochemical transformation of primidone (pharmaceutical).

Pharmaceutical and personal care products (PPCPs) are a group of emerging contaminants that have frequently been detected in aqueous environments. Phototransformation driven by solar irradiation is one of the most important natural processes for the elimination of PPCPs. In this study, primidone (PMD) was chosen as a model "photorefractory" compound.

Photochemical formation of carbonate radical and its reaction with dissolved organic matters.

The carbonate radical (CO) is a strong oxidative radical that is generated via the reactions of HCO/CO with hydroxyl radical (HO) or triplet states of dissolved organic matter (DOM) in sunlit surface water. The bimolecular reaction rate constants of CO with various DOM isolates ( [Formula: see text] ) were calculated as 15-239 (mg of C/L) s and were correlate to the bulk DOM properties, such as the content of phenolic moieties, the specific UV absorbance (SUVA), the E2/E3 value, and the fluorescence index (FI). The spectroscopic E2/E3 values was found to strongly correlated (R = 0.

Triplet-State Photochemistry of Dissolved Organic Matter: Triplet-State Energy Distribution and Surface Electric Charge Conditions.

Excited triplet states of chromophoric dissolved organic matter (CDOM*) are highly reactive species in sunlit surface waters and play a critical role in reactive oxygen species (ROS) formation and pollutant attenuation. In the present study, a series of chemical probes, including sorbic acid, sorbic alcohol, sorbic amine, trimethylphenol, and furfuryl alcohol, were employed to quantitatively determine CDOM* and O in various organic matters. Using a high concentration of sorbic alcohol as high-energy triplet states quencher, CDOM* can be first distinguished as high-energy triplet states (>250 kJ mol) and low-energy triplet states (<250 kJ mol).

Kinetics studies and mechanistic considerations on the reactions of superoxide radical ions with dissolved organic matter.

Superoxide ion (O) is one of the short lived reactive oxygen species (ROS) formed in aquatic environments. The reactions of O with the model dissolved organic matter (DOM) were studied using a chemiluminescent analysis method under relevant environmental conditions. The reaction of O with DOM produced reduced DOM (DOM) by fast one-electron-transfer in the initial stage.

Mechanistic consideration of the photochemical transformation of domoic acid (algal toxin) in DOM-Rich brackish water.

Domoic acid (DA) is a neurotoxin generated by several diatom species in harmful algae blooms (HABs). We report the photo-induced transformation products (TPs) and degradation mechanisms of DA in dissolved organic matter (DOM)-rich freshwater and brackish water. High-resolution quadrupole time-of-flight mass spectrometry (QTOF-MS) and the multivariate statistical strategy orthogonal partial least-squares discriminant analysis (OPLS-DA) identified 36 and 23 potential TPs in DOM-rich freshwater and brackish water, respectively.

Development of Novel Chemical Probes for Examining Triplet Natural Organic Matter under Solar Illumination.

Excited triplet states of chromophoric dissolved organic matter (CDOM*) are critical transient species in environmental photochemistry. In the present study, sorbic amine (2,4-hexadien-1-amine) and sorbic alcohol were employed as new probe molecules for triplet measurements and compared to the results measured from sorbic acid under identical conditions. Unlike sorbic acid, sorbic amine and sorbic alcohol were not directly photolyzed under solar irradiation.

Insights into the photo-induced formation of reactive intermediates from effluent organic matter: The role of chemical constituents.

In the present study, the formation of triplet states of organic matters (OM) from effluent organic matter (EfOM) under simulated solar irradiation was investigated. EfOM was separated into hydrophobic (HPO), transphilic (TPI), and hydrophilic (HPI) components. The quantum yield coefficients (ƒ) of OM were measured for each component and compared to those of reference natural organic matter (NOM).

Effects of C on the Photochemical Formation of Reactive Oxygen Species from Natural Organic Matter.

Buckminsterfullerenes (C) are widely used nanomaterials that are present in surface water. The combination of C and humic acid (HA) generates reactive oxygen species (ROS) under solar irradiation, but this process is not well understood. Thus, the present study focused on the photochemical formation of singlet oxygen (O), hydroxyl radical (HO)-like species, superoxide radicals (O), hydrogen peroxide (HO), and triplet excited states (C*/HA*) in solutions containing both C and HA.

The interaction of telomeric DNA and C-myc22 G-quadruplex with 11 natural alkaloids.

Telomeric DNA and C-myc22 are DNA G-quadruplex (G4)-forming sequences associated with tumorigenesis. Ligands that can facilitate the formation and increase the stabilization of G4 can halt tumor cell proliferation and have been regarded as potential anti-cancer drugs. In the present study, we have investigated the interaction of 11 natural alkaloids with G4 formed by telomeric DNA and C-myc22 sequences.

The interaction of telomere DNA G-quadruplex with three bis-benzyltetrahydroisoquinoline alkaloids.

Telomeres are important multifunctional nucleoprotein structures located at the ends of eukaryotic chromosomes. Telomerase regulates telomere elongation, and its activity is associated with tumorigenesis. Because the activity of telomerase can be inhibited by G-quadruplex (G4) formation (a four-stranded DNA with stacks of G-quartets formed by four guanines in a planar structure), the role of G4 in cancer therapy has attracted many research interests.

Research progress of RNA quadruplex.

RNA/DNA sequences rich in guanine (G) can form a 4-strand structure, G-quadruplex, which has been extensively researched and observed in mammalian, fungi, and plants, with in vivo existence in eukaryotic cells. Compared with DNA quadruplex, the potential existence of RNA quadruplex appears to be generally rare; however, it is believed by some researchers to be more inevitable in vivo and speculated to play an important role where it exists. Recently, researches concerning the function of G-quadruplexes in RNAs commence, making much progress.

Research Progress of RNA Quadruplex.

RNA/DNA sequences rich in guanine (G) can form a 4-strand structure, G-quadruplex, which has been extensively researched and observed in mammalian, fungi, and plants, with in vivo existence in eukaryotic cells. Compared with DNA quadruplex, the potential existence of RNA quadruplex appears to be generally rare; however, it is believed by some researchers to be more inevitable in vivo and speculated to play an important role where it exists. Recently, researches concerning the function of G-quadruplexes in RNAs commence, making much progress.