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Kristopher Mcneill - One of the best experts on this subject based on the ideXlab platform.

  • isotope fractionation associated with the Indirect Photolysis of substituted anilines in aqueous solution
    Environmental Science & Technology, 2015
    Co-Authors: Kristopher Mcneill, Marco Ratti, Silvio Canonica, Jakov Bolotin, Thomas B Hofstetter
    Abstract:

    Organic micropollutants containing aniline substructures are susceptible to different light-induced transformation processes in aquatic environments and water treatment operations. Here, we investigated the magnitude and variability of C and N isotope fractionation during the Indirect phototransformation of four para-substituted anilines in aerated aqueous solutions. The model photosensitizers, namely 9,10-anthraquinone-1,5-disulfonate and methylene blue, were used as surrogates for dissolved organic matter chromophores generating excited triplet states in sunlit surface waters. The transformation of aniline, 4-CH3-, 4-OCH3-, and 4-Cl-aniline by excited triplet states of the photosensitizers was associated with inverse and normal N isotope fractionation, whereas C isotope fractionation was negligible. The apparent 15N kinetic isotope effects (AKIE) were almost identical for both photosensitizers, increased from 0.9958±0.0013 for 4-OCH3-aniline to 1.0035±0.0006 for 4-Cl-aniline, and correlated well with the electron donating properties of the substituent. N isotope fractionation is pH-dependent in that H+ exchange reactions dominate below and N atom oxidation processes above the pKa value of the substituted aniline's conjugate acid. Correlations of C and N isotope fractionation for Indirect phototransformation were different from those determined previously for the direct Photolysis of chloroanilines and offer new opportunities to distinguish between abiotic degradation pathways.

  • Isotope Fractionation Associated with the Indirect Photolysis of Substituted Anilines in Aqueous Solution
    2015
    Co-Authors: Marco Ratti, Kristopher Mcneill, Silvio Canonica, Jakov Bolotin, Thomas B Hofstetter
    Abstract:

    Organic micropollutants containing aniline substructures are susceptible to different light-induced transformation processes in aquatic environments and water treatment operations. Here, we investigated the magnitude and variability of C and N isotope fractionation during the Indirect phototransformation of four para-substituted anilines in aerated aqueous solutions. The model photosensitizers, namely 9,10-anthraquinone-1,5-disulfonate and methylene blue, were used as surrogates for dissolved organic matter chromophores generating excited triplet states in sunlit surface waters. The transformation of aniline, 4-CH3-, 4-OCH3-, and 4-Cl-aniline by excited triplet states of the photosensitizers was associated with inverse and normal N isotope fractionation, whereas C isotope fractionation was negligible. The apparent 15N kinetic isotope effects (AKIE) were almost identical for both photosensitizers, increased from 0.9958 ± 0.0013 for 4-OCH3-aniline to 1.0035 ± 0.0006 for 4-Cl-aniline, and correlated well with the electron donating properties of the substituent. N isotope fractionation is pH-dependent in that H+ exchange reactions dominate below and N atom oxidation processes above the pKa value of the substituted aniline’s conjugate acid. Correlations of C and N isotope fractionation for Indirect phototransformation were different from those determined previously for the direct Photolysis of chloroanilines and offer new opportunities to distinguish between abiotic degradation pathways

  • Enhanced Indirect Photochemical Transformation of Histidine and Histamine through Association with Chromophoric Dissolved Organic Matter
    2015
    Co-Authors: Chiheng Chu, Christina K. Remucal, Rachel A. Lundeen, Michael Sander, Kristopher Mcneill
    Abstract:

    Photochemical transformations greatly affect the stability and fate of amino acids (AAs) in sunlit aquatic ecosystems. Whereas the direct phototransformation of dissolved AAs is well investigated, their Indirect Photolysis in the presence of chromophoric dissolved organic matter (CDOM) is poorly understood. In aquatic systems, CDOM may act both as sorbent for AAs and as photosensitizer, creating microenvironments with high concentrations of photochemically produced reactive intermediates, such as singlet oxygen (1O2). This study provides a systematic investigation of the Indirect photochemical transformation of histidine (His) and histamine by 1O2 in solutions containing CDOM as a function of solution pH. Both His and histamine showed pH-dependent enhanced phototransformation in the CDOM systems as compared to systems in which model, low-molecular-weight 1O2 sensitizers were used. Enhanced reactivity resulted from sorption of His and histamine to CDOM and thus exposure to elevated 1O2 concentrations in the CDOM microenvironment. The extent of reactivity enhancement depended on solution pH via its effects on the protonation state of His, histamine, and CDOM. Sorption-enhanced reactivity was independently supported by depressed rate enhancements in the presence of a cosorbate that competitively displaced His and histamine from CDOM. Incorporating sorption and photochemical transformation processes into a reaction rate prediction model improved the description of the abiotic photochemical transformation rates of His in the presence of CDOM

  • Indirect Photolysis of perfluorochemicals hydroxyl radical initiated oxidation of n ethyl perfluorooctane sulfonamido acetate n etfosaa and other perfluoroalkanesulfonamides
    Environmental Science & Technology, 2009
    Co-Authors: Megan H Plumlee, Kristopher Mcneill, Martin Reinhard
    Abstract:

    Selected perfluorinated surfactants were irradiated in aqueous hydrogen peroxide solutions using artificial sunlight to study transformation under aquatic environmental conditions. Indirect Photolysis mediated by hydroxyl radical was observed for N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA), N-ethyl perfluorooctane sulfonamide (N-EtFOSA), and perfluorooctane sulfonamide acetate (FOSAA). An upper limitforthe bimolecular reaction rate constant for reaction of *OH and N-EtFOSAA was determined to be (1.7 +/- 0.7) x 10(9) M(-1)s(-1). A proposed reaction pathwayfor degradation of the parent perfluorochemical, N-EtFOSE, to the other perfluoroalkanesulfonamides and perfluorooctanoate (PFOA) was developed and includes oxidation and N-dealkylation steps. As they did not undergo additional degradation, perfluorooctane sulfonamide (FOSA) and PFOA were the final degradation products of hydroxyl radical-initiated oxidation. UV-visible absorption spectra for the perfluorochemicals, showing absorbance in the UV region below the range of natural sunlight are also reported. In sunlit environments, Indirect Photolysis of perfluorochemicals is likely to be important in the determination of their environmental fate given the slow rates expected for biotransformation and weak sorption. Photolytic conversion of perfluorochemicals into refractory perfluorinated acids, mainly PFOA, could mean that a significant fraction of these compounds will accumulate in the world's oceans.

  • Indirect Photolysis of perfluorochemicals hydroxyl radical initiated oxidation of n ethyl perfluorooctane sulfonamido acetate n etfosaa and other perfluoroalkanesulfonamides
    Environmental Science & Technology, 2009
    Co-Authors: Megan H Plumlee, Kristopher Mcneill, Martin Reinhard
    Abstract:

    Selected perfluorinated surfactants were irradiated in aqueous hydrogen peroxide solutions using artificial sunlight to study transformation under aquatic environmental conditions. Indirect Photolysis mediated by hydroxyl radical was observed for N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA), N-ethyl perfluorooctane sulfonamide (N-EtFOSA), and perfluorooctane sulfonamide acetate (FOSAA). An upper limit for the bimolecular reaction rate constant for reaction of •OH and N-EtFOSAA was determined to be (1.7 ± 0.7) × 109 M−1s−1. A proposed reaction pathway for degradation of the parent perfluorochemical, N-EtFOSE, to the other perfluoroalkanesulfonamides and perfluorooctanoate (PFOA) was developed and includes oxidation and N-dealkylation steps. As they did not undergo additional degradation, perfluorooctane sulfonamide (FOSA) and PFOA were the final degradation products of hydroxyl radical-initiated oxidation. UV−visible absorption spectra for t...

Peizhe Sun - One of the best experts on this subject based on the ideXlab platform.

  • photo ammonification of low molecular weight dissolved organic nitrogen by direct and Indirect Photolysis
    Science of The Total Environment, 2021
    Co-Authors: Yutong Zhang, Ruochun Zhang, Khan M G Mostofa, Wen Liu, Peizhe Sun
    Abstract:

    The photo-ammonification process plays a crucial role in the transformation of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN). However, previous studies have primarily focused on DON biotransformation than on abiotic processes. This study investigated the photo-ammonification process of nine model low molecular weight (LMW) DON molecules (e.g., amino acids, nucleotides, and urea) under the influence of different light sources. The results showed that photo-ammonification of model DON was mainly induced by UV light, while negligible contribution by visible light was found. Depending on their molecular structures, amino acids yielded different ammonia amounts, whereas negligible photo-ammonification was observed for nucleotides and urea. As for the reactive species, OH promoted ammonia yields of all the model amino acids; 3CDOM⁎ contributed to the photo-ammonification of six amino acids; 1O2 only had a positive impact on ammonification of tryptophan, histidine, and tyrosine; and CO3- accelerated ammonia generation from histidine and methionine. In natural water samples, tryptophan, tyrosine, histidine, and methionine generated significant ammonia. OH and 1O2 were speculated as the contributing reactive species based on kinetic studies as well as significant fluorescent humic-like and tyrosine-like substances degradation in irradiated samples compared to the raw samples characterized by the EEM-PARAFAC analysis. The negative linear correlations between photo-ammonification rates and the ELUMO-EHOMO of the amino acids emphasized the importance of the role of the molecular structure. Overall, these results revealed the LMW DON photo-ammonification mechanism in sunlit surface waters and highlighted its significance in the nitrogen biogeochemical cycle as well as water quality management.

  • Kinetics and modeling of sulfonamide antibiotic degradation in wastewater and human urine by UV/H2O2 and UV/PDS.
    Water research, 2016
    Co-Authors: Ruochun Zhang, Yongkui Yang, Ching-hua Huang, Lin Zhao, Peizhe Sun
    Abstract:

    Sulfonamide antibiotics have been frequently detected in the aquatic environment and are of emerging concern due to their adverse bio-effect and potential of inducing antibiotic resistance. This study investigated the degradation kinetics of sulfonamide antibiotics in synthetic wastewater and hydrolyzed human urine by low pressure (LP) UV, UV/H2O2 and UV/peroxydisulfate (PDS). Direct Photolysis rates of sulfonamide antibiotics varied and depended on the structures. Sulfonamides with a five-membered heterocyclic group underwent faster direct Photolysis. For Indirect Photolysis processes, second-order rate constants of sulfonamide antibiotics with hydroxyl radical, sulfate radical and carbonate radical were determined, which were (6.21–9.26) × 109, (0.77–16.1) × 1010 and (1.25–8.71) × 108 M−1 s−1, respectively. A dynamic model was applied and successfully predicted the degradation kinetics of sulfonamides in different water matrices. In synthetic wastewater, carbonate radical contributed to approximately 10% of the overall removal, whereas in synthetic hydrolyzed urine, carbonate radical was the dominant reactive species to degrade sulfonamides. Sulfonamide antibiotics were eliminated more efficiently in synthetic hydrolyzed urine than in synthetic wastewater and UV/PDS was more efficient than UV/H2O2 to degrade most sulfonamides. Energy evaluation showed that UV/PDS costs less energy than LPUV and UV/H2O2 under the experimental conditions applied in this study, particularly for sulfonamides whose Indirect Photolysis overweighed direct Photolysis. By varying UV dose and oxidant dose, the UV/H2O2 process can be optimized to achieve higher efficiency than the UV/PDS process in synthetic wastewater.

  • degradation of pharmaceuticals and metabolite in synthetic human urine by uv uv h2o2 and uv pds
    Environmental Science & Technology, 2015
    Co-Authors: Ruochun Zhang, Lin Zhao, Peizhe Sun, Treavor H Boyer, Ching-hua Huang
    Abstract:

    To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09–8.53) × 109 M–1·s–1 with hydroxyl radical, and (2.35–16.1) × 109 M–1·s–1 with sulfate radical. In fresh urine matrix, the pharmaceuticals’ Indirect Photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the Indirect Photolysis was strongly affected by inorganic urine constituents. Chl...

  • Degradation of Pharmaceuticals and Metabolite in Synthetic Human Urine by UV, UV/H2O2, and UV/PDS
    2015
    Co-Authors: Ruochun Zhang, Lin Zhao, Peizhe Sun, Treavor H. Boyer, Ching-hua Huang
    Abstract:

    To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09–8.53) × 109 M–1·s–1 with hydroxyl radical, and (2.35–16.1) × 109 M–1·s–1 with sulfate radical. In fresh urine matrix, the pharmaceuticals’ Indirect Photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the Indirect Photolysis was strongly affected by inorganic urine constituents. Chloride had no apparent impact on UV/H2O2, but significantly raised the hydroxyl radical concentration in UV/PDS. Carbonate species reacted with hydroxyl or sulfate radical to generate carbonate radical, which degraded SMX and TMP, primarily due to the presence of aromatic amino group(s) (k = 2.68 × 108 and 3.45 × 107 M–1·s–1) but reacted slowly with acetyl-SMX. Ammonia reacted with hydroxyl or sulfate radical to generate reactive nitrogen species that could react appreciably only with SMX. Kinetic simulation of radical concentrations, along with products analysis, helped elucidate the major reactive species in the pharmaceuticals’ degradation. Overall, the AOPs’ performance was higher in the hydrolyzed urine than fresh urine matrix with UV/PDS better than UV/H2O2, and varied significantly depending on pharmaceutical’s structure

Yu-ping Chin - One of the best experts on this subject based on the ideXlab platform.

  • Photolysis- and Dissolved Organic Matter-Induced Toxicity of Triclocarban to Daphnia magna
    2017
    Co-Authors: Katie A. Albanese, Roman P. Lanno, Christopher M. Hadad, Yu-ping Chin
    Abstract:

    Triclocarban (TCC) is a common antimicrobial compound used in soaps and other household products and is found globally in many surface waters. This study investigated the acute toxicity of TCC and its photolyzed products to Daphnia magna using 50% 96-h lethal concentration (LC50) tests. The effects of dissolved organic matter (DOM) on the toxicity of TCC photoproducts to D. magna were also studied. Direct Photolysis of TCC formed photoproducts that were significantly less toxic (LC50 value of 2.67 ± 0.6 μM) than the parent TCC compound (LC50 value of 0.087 ± 0.3 μM). In contrast, the Indirect Photolysis of TCC in the presence of DOM produced photoproducts that were significantly more toxic (LC50 value of 0.032 ± 0.015 μM). Chlorinated anilines and isocyanates, identified by mass spectrometry, were formed in the presence of DOM as Indirect Photolysis products of TCC and were shown to be partially responsible for the observed toxicity

  • Direct and Indirect Photolysis of triclocarban in the presence of dissolved organic matter
    Elementa: Science of the Anthropocene, 2015
    Co-Authors: Tamara D. Trouts, Yu-ping Chin
    Abstract:

    Photolysis is an important attenuation pathway for the removal of wastewater effluent organic micropollutants from surface waters. In this work, direct and Indirect processes leading to the degradation of the disinfectant, triclocarban were studied. Photo-irradiation experiments were conducted in water collected from Old Woman Creek (OWC) a tributary of Lake Erie near Huron, OH, USA and in solutions of fulvic acids isolated from the Suwannee River, Georgia, USA (SRFA), Old Woman Creek (OWCFA) and Pony Lake, Antarctica (PLFA). Photodegradation of triclocarban proceeded faster in the presence of all three fulvic acids relative to deionized water. PLFA, an autochthonous dissolved organic matter (DOM) was found to be more reactive than the other fulvic acids, while the mostly allochthonous SRFA exhibited the lowest reactivity toward triclocarban. The later observation can be in part explained by anti-oxidant moieties present in SRFA. Photosensitized triclocarban degradation in whole water DOM from OWC was entirely attributable to the fulvic acid fraction and suggests that this component is the most photo-reactive fraction of the DOM. Anoxic and methanol-quenched experiments revealed unexpected results whereby the former suggests oxidation through reaction with triplet DOM, while the later is indicative of reaction with photo-generated hydroxyl radicals. It is possible that methanol can quench excited DOM species, which would shut down the triplet oxidation pathway. Finally, we observed no enhancement of triclocarban-photosensitized degradation through the addition of iron.

  • the role of dissolved organic matter in arctic surface waters in the Photolysis of hexachlorobenzene and lindane
    Journal of Geophysical Research, 2012
    Co-Authors: Amanda M. Grannas, Yu-ping Chin, Penney L Miller, Rose M Cory, Diane M Mcknight
    Abstract:

    [1] Terrestrially derived dissolved organic matter (DOM) can impact the fate of persistent organic pollutants (POPs) that are transported to the Arctic via global distillation. Interactions between DOM and POPs through hydrophobic binding processes may influence their photofate in arctic surface waters. We examined the DOM-mediated photodegradation of γ-hexachlorocyclohexane (lindane) and hexachlorobenzene (HCB) in arctic surface waters. These two halogenated organic compounds are commonly detected in the Arctic. We examined how different sources of DOM affect the Indirect Photolysis of these compounds. We conducted our study using DOM from arctic streams and lakes near the Toolik Lake Long-term Ecological Research Site. HCB or lindane was irradiated in the presence and absence of DOM from these sources, both at the surface of an arctic lake and at 10 cm depth, to investigate the Indirect phototransformation of these two compounds and the depth dependence of the observed chemistry. In both artificial and natural sunlight, two of four DOM sources studied stimulated the photodegradation of HCB but not of lindane, suggesting that the Indirect phototransformation is a selective process depending on the interactions between DOM and POPs. Through solubility studies, we found that HCB readily partitions to isolated Toolik Lake DOM, while lindane shows no affinity for DOM, findings that corroborate results previously reported in the literature. We demonstrate for the first time DOM's role as a sensitizer for photodegradation of some POPs under field conditions, thus confirming that this process may be an important control on the fate of POPs exhibiting a strong affinity for DOM.

  • direct and Indirect Photolysis of polycyclic aromatic hydrocarbons in nitrate rich surface waters
    Environmental Toxicology and Chemistry, 2007
    Co-Authors: Laura E Jacobs, Linda K Weavers, Yu-ping Chin
    Abstract:

    The Photolysis of three polycyclic aromatic hydrocarbons (PAHs)-pyrene, phenanthrene, and naphthalene-were studied in waters taken from creosote-contaminated sites in Gary (IN, USA) and Wilmington (NC, USA). Direct Photolysis of all PAHs was observed under simulated solar radiation, with pyrene degrading at a faster rate than either phenanthrene or naphthalene. Phenanthrene degradation, when compared to its direct Photolysis rate, increased in Gary water but decreased in Wilmington water. Analysis of the waters for dissolved organic carbon (DOC) and nitrate revealed higher levels of DOC in the Wilmington sample (9.29 mg/L) compared with the Gary sample (6.73 mg/L), as well as significantly less nitrate (0.046 mM vs 0.205 mM for the Gary sample). The slightly lower rate of phenanthrene degradation observed for the Wilmington sample, corrected for light attenuation effects, is statistically the same as that in the direct Photolysis experiments. Therefore, we attribute the lower rate of degradation in the presence of Wilmington water to light screening by DOC, but we believe the faster reaction rate observed for the Gary water results from hydroxyl radical (OH*) chemistry generated by nitrate Photolysis. Indeed, degradation of the target compound increased when nitrate (at 0.2 and 0.4 mM) was added to the Wilmington sample, further corroborating this conclusion. Overall photoreaction rates decreased for the lower-molecular-weight PAHs, because the fastest naphthalene photolytic rate was roughly two orders of magnitude slower than that of pyrene.

  • Indirect Photolysis promoted by natural and engineered wetland water constituents processes leading to alachlor degradation
    Environmental Science & Technology, 2005
    Co-Authors: Penney L Miller, Yu-ping Chin
    Abstract:

    Wetland surface waters that received drainage from agricultural fields were probed for constituents that would promote the photodegradation of agriculture herbicides. Alachlor proved to be a good chemical probe for examining Indirect Photolysis due to its lack of reactivity by either direct Photolysis or dark reaction pathways and its ubiquity as an agricultural herbicide. Water samples were taken from natural (Old Woman Creek) and engineered wetlands in Ohio that receive copious amounts of agricultural runoff. Possible photosensitizers including dissolved organic matter (DOM), iron, and nitrate were measured in the samples. In alkaline waters (pH >7.8), the photochemical degradation of alachlor became important only in the presence of high nitrate levels (≈1 mM). In pH-adjusted (∼4) samples, the observed degradation rate coefficient increased 3−18 times of that measured at the natural pH. Methanol quenching experiments and kinetics modeling suggest that hydroxyl radical is the principal reactant. The pro...

Guanglong Liu - One of the best experts on this subject based on the ideXlab platform.

  • photo induced phosphate released from organic phosphorus degradation in deionized and natural water
    Photochemical and Photobiological Sciences, 2017
    Co-Authors: Yiyong Zhou, Guanglong Liu, Qian Tang, Xiuyun Cao, Jianwei Zhao, Duanwei Zhu
    Abstract:

    The photodegradation of organic phosphorus is one of the most important processes of the phosphorus cycle by which phosphate is regenerated in the water environment. In this study, the influence of direct Photolysis or Indirect Photolysis of organic phosphorus using natural photosensitizers on the released phosphate was examined in deionized and natural water under ultraviolet (UV) irradiation using diazinon as the organic phosphorus model. Phosphate was released when diazinon was exposed to UV light, and the solution pH also exhibited distinct influences on the phosphate that was released from diazinon photodegradation. When the natural photosensitizers were added, the amount of phosphate released increased significantly because of the diazinon Indirect photodegradation by reactive species, such as the hydroxyl radical generated by NO3− and Fe3+. However, humic acid and HCO3− inhibited the phosphate released by a radical scavenging effect. When natural water was spiked with diazinon, the phosphate that was released in natural water was higher than that of the control or deionized water, and the phosphate that was released was inhibited when isopropanol was added to the reaction. In addition, the formation of hydroxyl radicals (˙OH) in the natural water systems was identified from the photoluminescence spectra using coumarin as the trapping molecule, and the steady-state concentration of ˙OH in natural water was 3.07 ± 0.57 × 10−16 M under UV irradiation. All of these results indicated that direct and Indirect Photolysis degradation of organic phosphorus significantly impacts the release of phosphate in surface waters.

Ruochun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • photo ammonification of low molecular weight dissolved organic nitrogen by direct and Indirect Photolysis
    Science of The Total Environment, 2021
    Co-Authors: Yutong Zhang, Ruochun Zhang, Khan M G Mostofa, Wen Liu, Peizhe Sun
    Abstract:

    The photo-ammonification process plays a crucial role in the transformation of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN). However, previous studies have primarily focused on DON biotransformation than on abiotic processes. This study investigated the photo-ammonification process of nine model low molecular weight (LMW) DON molecules (e.g., amino acids, nucleotides, and urea) under the influence of different light sources. The results showed that photo-ammonification of model DON was mainly induced by UV light, while negligible contribution by visible light was found. Depending on their molecular structures, amino acids yielded different ammonia amounts, whereas negligible photo-ammonification was observed for nucleotides and urea. As for the reactive species, OH promoted ammonia yields of all the model amino acids; 3CDOM⁎ contributed to the photo-ammonification of six amino acids; 1O2 only had a positive impact on ammonification of tryptophan, histidine, and tyrosine; and CO3- accelerated ammonia generation from histidine and methionine. In natural water samples, tryptophan, tyrosine, histidine, and methionine generated significant ammonia. OH and 1O2 were speculated as the contributing reactive species based on kinetic studies as well as significant fluorescent humic-like and tyrosine-like substances degradation in irradiated samples compared to the raw samples characterized by the EEM-PARAFAC analysis. The negative linear correlations between photo-ammonification rates and the ELUMO-EHOMO of the amino acids emphasized the importance of the role of the molecular structure. Overall, these results revealed the LMW DON photo-ammonification mechanism in sunlit surface waters and highlighted its significance in the nitrogen biogeochemical cycle as well as water quality management.

  • Kinetics and modeling of sulfonamide antibiotic degradation in wastewater and human urine by UV/H2O2 and UV/PDS.
    Water research, 2016
    Co-Authors: Ruochun Zhang, Yongkui Yang, Ching-hua Huang, Lin Zhao, Peizhe Sun
    Abstract:

    Sulfonamide antibiotics have been frequently detected in the aquatic environment and are of emerging concern due to their adverse bio-effect and potential of inducing antibiotic resistance. This study investigated the degradation kinetics of sulfonamide antibiotics in synthetic wastewater and hydrolyzed human urine by low pressure (LP) UV, UV/H2O2 and UV/peroxydisulfate (PDS). Direct Photolysis rates of sulfonamide antibiotics varied and depended on the structures. Sulfonamides with a five-membered heterocyclic group underwent faster direct Photolysis. For Indirect Photolysis processes, second-order rate constants of sulfonamide antibiotics with hydroxyl radical, sulfate radical and carbonate radical were determined, which were (6.21–9.26) × 109, (0.77–16.1) × 1010 and (1.25–8.71) × 108 M−1 s−1, respectively. A dynamic model was applied and successfully predicted the degradation kinetics of sulfonamides in different water matrices. In synthetic wastewater, carbonate radical contributed to approximately 10% of the overall removal, whereas in synthetic hydrolyzed urine, carbonate radical was the dominant reactive species to degrade sulfonamides. Sulfonamide antibiotics were eliminated more efficiently in synthetic hydrolyzed urine than in synthetic wastewater and UV/PDS was more efficient than UV/H2O2 to degrade most sulfonamides. Energy evaluation showed that UV/PDS costs less energy than LPUV and UV/H2O2 under the experimental conditions applied in this study, particularly for sulfonamides whose Indirect Photolysis overweighed direct Photolysis. By varying UV dose and oxidant dose, the UV/H2O2 process can be optimized to achieve higher efficiency than the UV/PDS process in synthetic wastewater.

  • degradation of pharmaceuticals and metabolite in synthetic human urine by uv uv h2o2 and uv pds
    Environmental Science & Technology, 2015
    Co-Authors: Ruochun Zhang, Lin Zhao, Peizhe Sun, Treavor H Boyer, Ching-hua Huang
    Abstract:

    To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09–8.53) × 109 M–1·s–1 with hydroxyl radical, and (2.35–16.1) × 109 M–1·s–1 with sulfate radical. In fresh urine matrix, the pharmaceuticals’ Indirect Photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the Indirect Photolysis was strongly affected by inorganic urine constituents. Chl...

  • Degradation of Pharmaceuticals and Metabolite in Synthetic Human Urine by UV, UV/H2O2, and UV/PDS
    2015
    Co-Authors: Ruochun Zhang, Lin Zhao, Peizhe Sun, Treavor H. Boyer, Ching-hua Huang
    Abstract:

    To minimize environmental pharmaceutical micropollutants, treatment of human urine could be an efficient approach due to the high pharmaceutical concentration and toxic potential excreted in urine. This study investigated the degradation kinetics and mechanisms of sulfamethoxazole (SMX), trimethoprim (TMP) and N4-acetyl-sulfamethoxazole (acetyl-SMX) in synthetic fresh and hydrolyzed human urines by low-pressure UV, and UV combined with H2O2 and peroxydisulfate (PDS). The objective was to compare the two advanced oxidation processes (AOPs) and assess the impact of urine matrices. All three compounds reacted quickly in the AOPs, exhibiting rate constants of (6.09–8.53) × 109 M–1·s–1 with hydroxyl radical, and (2.35–16.1) × 109 M–1·s–1 with sulfate radical. In fresh urine matrix, the pharmaceuticals’ Indirect Photolysis was significantly suppressed by the scavenging effect of urine citrate and urea. In hydrolyzed urine matrix, the Indirect Photolysis was strongly affected by inorganic urine constituents. Chloride had no apparent impact on UV/H2O2, but significantly raised the hydroxyl radical concentration in UV/PDS. Carbonate species reacted with hydroxyl or sulfate radical to generate carbonate radical, which degraded SMX and TMP, primarily due to the presence of aromatic amino group(s) (k = 2.68 × 108 and 3.45 × 107 M–1·s–1) but reacted slowly with acetyl-SMX. Ammonia reacted with hydroxyl or sulfate radical to generate reactive nitrogen species that could react appreciably only with SMX. Kinetic simulation of radical concentrations, along with products analysis, helped elucidate the major reactive species in the pharmaceuticals’ degradation. Overall, the AOPs’ performance was higher in the hydrolyzed urine than fresh urine matrix with UV/PDS better than UV/H2O2, and varied significantly depending on pharmaceutical’s structure