Does Pollyanna hypothesis hold true in death narratives? A sentiment analysis approach.

Pollyanna hypothesis claims that human beings have a universal tendency to use positive words more frequently and broadly than negative words. The present study aims to test Pollyanna hypothesis in medical death narratives at both lexical and text levels by using sentiment analysis and emotion detection methods, and to qualitatively analyze the contextual use of emotion words to deepen the understanding of doctors' emotions. Sentiment analysis showed a strong token-based linguistic positivity and a weak type-based negativity bias at the lexical level, and a general positivity bias at the text level, despite the gender of the doctors. Emotion detection discovered three prominent emotions of "joy", "sadness", and "anger", and a greater diversity of negative emotions in contrast to positive emotions in medical death narratives. Contextual analysis revealed that emotion words associated with joy were primarily observed in contexts related to doctors' actions and behaviors aiming to benefit others and promote social wellbeing. Emotion words associated with sadness and anger were chiefly employed to describe situations involving patients' death and doctors' attitudes towards death. The results confirm Pollyanna hypothesis at both token-based lexical level and text level and falsify the hypothesis at type-based lexical level. Possible explanations are explored by contextual analysis, and theoretical analysis from the perspectives of cognitive linguistics and social psychology. The findings are expected to enrich the understanding of Pollyanna hypothesis as well as the junior doctors' emotional responses to clinical deaths.

Dissolved organic matter accelerates microbial degradation of 17 alpha-ethinylestradiol in the presence of iron mineral.

Dissolved organic matter (DOM) and iron minerals widely existing in the natural aquatic environment can mediate the migration and transformation of organic pollutants. However, the mechanism of interaction between DOM and iron minerals in the microbial degradation of pollutants deserves further investigation. In this study, the mechanism of 17 alpha-ethinylestradiol (EE2) biodegradation mediated by humic acid (HA) and three kinds of iron minerals (goethite, magnetite, and pyrite) was investigated. The results found that HA and iron minerals significantly accelerated the biodegradation process of EE2, and the highest degradation efficiency of EE2 (48%) was observed in the HA-mediated microbial system with pyrite under aerobic conditions. Furthermore, it had been demonstrated that hydroxyl radicals (HO•) was the main active substance responsible for the microbial degradation of EE2. HO• is primarily generated through the reaction between hydrogen peroxide secreted by microorganisms and Fe(II), with aerobic conditions being more conducive. The presence of iron minerals and HA could change the microbial communities in the EE2 biodegradation system. These findings provide new information for exploring the migration and transformation of pollutants by microorganisms in iron-rich environments.

The disinfectant residues promote the leaching of water contaminants from plastic pipe particles.

Disinfection treatment is an indispensable water purification process, but it can leave trace concentrations of disinfectant in the purified water. Disinfectants oxidation can age plastic pipes and release hazardous microplastics and chemicals into drinking water. Lengths of commercially-available unplasticized polyvinyl chloride and polypropylene random copolymer water pipe were ground into particles and exposed to micro-molar concentrations of ClO2, NaClO, trichloroisocyanuric acid, or O3 for up to 75 days. The disinfectants aged the plastic and changed its surface morphology and functional groups. Meanwhile, disinfectants could significantly promote the release of organic matter from plastic pipes into the water. ClO2 generated the highest concentrations of organic matter in the leachates from both plastics. Plasticizers, antioxidants and low molecular weight organic matter were detected in all of the leachates. Leachate samples inhibited the proliferation of CT26 mouse colon cancer and induced oxidative stress in the cells. Even trace concentrations of residual disinfectant can constitute a drinking water risk.

Effects of water constituents on the stability of gas diffusion electrode during electrochemical hydrogen peroxide production for water and wastewater treatment.

Electrochemically producing hydrogen peroxide (H2O2) from oxygen reduction reaction (ORR) with natural air diffusion electrode (NADE) is an attractive way to supply H2O2 for decentralized water treatment. In this study, the stability of NADE during H2O2 electroproduction in varying water matrices were evaluated, including synthetic electrolyte solutions (0.05 M Na2SO4) with or without calcium ions (Ca2+, 200 mg/L) and/or humic acid (HA, 40 mg/L), as well as a selected municipal wastewater (92.7 mg/L Ca2+, 3.6 mg/L Mg2+, and 23.9 mg/L total organic carbon). The results show that NADEs maintained a good stability during H2O2 electroproduction in Na2SO4 solutions regardless of the presence of HA. However, Ca2+ (and Mg2+) could form significant amounts of mineral precipitates on the surface and in the internal pores of NADEs during H2O2 electroproduction. These mineral precipitates can negatively influence H2O2 production by impeding the oxygen, electron, and proton transfer processes involved in ORR to H2O2. Moreover, the mineral precipitates shifted the NADEs from hydrophobic to hydrophilic, which may promote H2O2 reduction to H2O at the NADEs. Consequently, the apparent current efficiencies of H2O2 production decreased substantially from initially ∼90% to 50%-70% as the NADEs were continuously used for 60 h in the Ca-containing solutions and selected wastewater. These results indicate that water constituents that are commonly present in real water matrices, especially Ca2+, can cause serious deterioration of NADE stability during H2O2 electroproduction. Therefore, proper strategies are needed to mitigate electrode fouling during H2O2 electroproduction with NADEs in practical water and wastewater treatment.

Assessment of the validity of the quenching method for evaluating the role of reactive species in pollutant abatement during the persulfate-based process.

Reactive species such as sulfate radicals (SO4•-), hydroxyl radicals (•OH), and/or singlet oxygen (1O2) have often been proposed as the main reactive species for pollutant abatement during the persulfate-based process, and their relative importance is conventionally assessed by the quenching method based on an implicit fundamental assumption that the added high-concentration quenchers (e.g., tert-butanol and methanol) only scavenge their target reactive species, but do not considerably affect the other reaction mechanism of the system. To examine the validity of this assumption, this study evaluated the effects of several commonly used quenchers (tert-butanol, methanol, ethanol, isopropanol, furfuryl alcohol, and L-histidine) on the mechanism of a cobalt mediated peroxymonosulfate (Co(II)/PMS) process. The results demonstrate that besides quenching target reactive species, the added high-concentration quenchers can cause many confounding effects on the Co(II)/PMS process, e.g., accelerating PMS decomposition, interfering reactive species production, and quenching of non-target reactive species. Because of these confounding effects, the quenching method can actually lead to serious misinterpretation of the role of reactive species in pollutant abatement during the persulfate-based process. The findings of this study highlight that the underlying assumption of the quenching method is usually invalid for the persulfate-based process. Therefore, it should be cautious to apply the quenching method to investigate the mechanism of the persulfate-based process, and some debatable conclusions of prior studies obtained with the quenching method may require further verification.

Evaluation of the concentration and contribution of superoxide radical for micropollutant abatement during ozonation.

Due to the fast reaction of superoxide radical (O2•-) with ozone (O3), it has been suggested that O2•- is present at very low concentrations during ozonation. Therefore, while O2•- has been considered a critical chain carrier for promoting O3 decomposition to hydroxyl radicals (•OH), the direct reactions of O2•- with micropollutants have been assumed to be insignificant during ozonation. In this study, we monitored the exposures of O3, •OH, and O2•- by following the depletion of O3, p-chlorobenzoic acid (pCBA, as •OH probe), and tetrachloromethane (CCl4, as O2•- probe) during ozonation of various water matrices (surface water, groundwater, and secondary wastewater effluent). For a given water matrix, the ratio between •OH and O3 exposures (Rct), O2•- and O3 exposures (RSO), as well as O2•- and •OH exposures (RSH) remained almost constant over the entire reaction time. This suggests that during ozonation, the ratios between the transient concentrations of •OH and O3, O2•- and O3, and O2•- and •OH were also constant and equaled to the Rct, RSO, and RSH, respectively. Based on the O3, •OH, and O2•- exposures observed during ozonation, a chemical kinetic model was proposed to simulate the abatement of ten ozone-resistant micropollutants in the three water matrices by ozonation. The results indicate that due to the higher concentrations of O2•- than •OH (RSH = ~5-8), the reactions with O2•- played a non-negligible or even dominant role in the abatement of some micropollutants that have similar or higher O2•- reactivity than •OH reactivity (e.g., tetrachloroethylene, chloroform, and PFOA). Compared with the previous model that neglected the contribution of O2•- to micropollutant abatement, the proposed model more accurately simulated the abatement efficiencies of the test micropollutants during ozonation. These results indicate that the proposed model can provide a useful tool for the generalized prediction of micropollutant abatement by ozonation.

Kinetics and mechanism of thiamethoxam abatement by ozonation and ozone-based advanced oxidation processes.

In this study, the abatement of neonicotinoid insecticide, thiamethoxam, by single ozonation, ozone/ultraviolet (O3/UV) and electro-peroxone (EP) process was evaluated. The second-order rate constants for the reaction of thiamethoxam with O3 and hydroxyl radical (OH) at pH 7 were determined to be 15.4 M-1 s-1 and 3.9 × 109 M-1 s-1, respectively. The degradation pathways of thiamethoxam were proposed based on quantum chemical calculations and transformation products were identified using chromatographic and mass-spectrometric techniques. The acute and chronic toxicity of thiamethoxam and its major TPs to various aquatic organisms were assessed. With typical ozone doses applied in water treatment (≤5 mg/L), thiamethoxam was abated by only ∼16-32 % in two real water matrices (groundwater and surface water) during single ozonation, but by ∼100 % and >70 % during the O3/UV and EP treatment, respectively. The energy demand to abate 90 % thiamethoxam in the two water matrices was generally comparable for single ozonation and the EP process (∼0.14 ±â€¯0.03 kW h/m3), but higher for the O3/UV process (0.21-0.22 kW h/m3). These results suggest that single ozonation is unable to sufficiently abate thiamethoxam under typical conditions of water treatment. Therefore, ozone-based advanced oxidation processes are needed to enhance thiamethoxam abatement.

Comparison of pharmaceutical abatement in various water matrices by conventional ozonation, peroxone (O3/H2O2), and an electro-peroxone process.

Pharmaceutical abatement in a groundwater (GW), surface water (SW), and secondary effluent (SE) by conventional ozonation, the conventional peroxone (O3/H2O2), and the electro-peroxone (E-peroxone) processes was compared in batch tests. SE had significantly more fast-reacting dissolved organic matter (DOM) moieties than GW and SW. Therefore, O3 decomposed much faster in SE than in GW and SW. At specific ozone doses of 0.5-1.5 mg O3/mg dissolved organic carbon (DOC), the application of O3/H2O2 and E-peroxone process (by adding external H2O2 stocks or in-situ generating H2O2 from cathodic O2 reduction during ozonation) similarly enhanced the OH yield from O3 decomposition by ∼5-12% and 5-7% in GW and SW, respectively, compared to conventional ozonation. In contrast, due to the slower reaction kinetics of O3 with H2O2 than O3 with fast-reacting DOM moieties, the addition or electro-generation of H2O2 hardly increased the OH yield (<4% increases) in SE. Corresponding to the changes in the OH yields, the abatement efficiencies of ozone-resistant pharmaceuticals (ibuprofen and clofibric acid) increased evidently in GW (up to ∼14-18% at a specific ozone dose of 1.5 mg O3/mg DOC), moderately in SW (up to 6-10% at 0.5 mg O3/mg DOC), and negligibly in SE during the O3/H2O2 and E-peroxone treatment compared to conventional ozonation. These results indicate that similar to the conventional O3/H2O2 process, the E-peroxone process can more pronouncedly enhance O3 transformation to OH, and thus increase the abatement efficiency of ozone-resistant pharmaceuticals in water matrices exerting relatively high ozone stability (e.g., groundwater and surface water with low DOM contents). Therefore, by installing electrodes in existing ozone reactors, the E-peroxone process may provide a convenient way to enhance pharmaceutical abatement in drinking water applications, where groundwater and surface water with low DOM contents are used as the source waters.

Adsorption of heavy metal from aqueous solution by dehydrated root powder of long-root Eichhornia crassipes.

The root powder of long-root Eichhornia crassipes, as a new kind of biodegradable adsorbent, has been tested for aqueous adsorption of Pb, Zn, Cu, and Cd. From FT-IR, we found that the absorption peaks of phosphorous compounds, carbonyl, and nitrogenous compounds displayed obvious changes before and after adsorption which illustrated that plant characteristics may play a role in binding with metals. Surface properties and morphology of the root powders have been characterized by means of SEM and BET. Energy spectrum analysis showed that the metals were adsorbed on root powders after adsorption. Then, optimum quantity of powder, pH values, and metal ion concentrations in single-system and multi-system were detected to discuss the characteristics and mechanisms of metal adsorption. Freundlich model and the second-order kinetics equation could well describe the adsorption of heavy metals in single-metal system. The adsorption of Pb, Zn, and Cd in the multi-metal system decreased with the concentration increased. At last, competitive adsorption of every two metals on root powder proved that Cu and Pb had suppressed the adsorption performance of Cd and Zn.

Mechanisms of enhanced total organic carbon elimination from oxalic acid solutions by electro-peroxone process.

Electro-peroxone (E-peroxone) is a novel electrocatalytic ozonation process that combines ozonation and electrolysis process to enhance pollutant degradation during water and wastewater treatment. This enhancement has been mainly attributed to several mechanisms that increase O3 transformation to ·OH in the E-peroxone system, e.g., electro-generation of H2O2 from O2 at a carbon-based cathode and its subsequent peroxone reaction with O3 to ·OH, electro-reduction of O3 to ·OH at the cathode, and O3 decomposition to ·OH at high local pH near the cathode. To get more insight how these mechanisms contribute respectively to the enhancement, this study investigated total organic carbon (TOC) elimination from oxalic acid (OA) solutions by the E-peroxone process. Results show that the E-peroxone process significantly increased TOC elimination rate by 10.2-12.5 times compared with the linear addition of the individual rates of corresponding ozonation and electrolysis process. Kinetic analyses reveal that the electrochemically-driven peroxone reaction is the most important mechanism for the enhanced TOC elimination rate, while the other mechanisms contribute minor to the enhancement by a factor of 1.6-2.5. The results indicate that proper selection of electrodes that can effectively produce H2O2 at the cathode is critical to maximize TOC elimination in the E-peroxone process.