Dissolved organic matter (DOM) plays an important role in the biogeochemical cycle in natural waters. The determination and characterization of the excited triplet state of DOM (3DOM*) have... Show moreDissolved organic matter (DOM) plays an important role in the biogeochemical cycle in natural waters. The determination and characterization of the excited triplet state of DOM (3DOM*) have attracted much attention recently. However, the underlying differences of determined 3DOM* through different pathways are not yet fully understood. In this study, the differences and underlying mechanisms of the determined 3DOM* using 2,4-hexadien-1-ol (HDO) through an energy transfer pathway and 2,4,6-trimethylphenol (TMP) through an electron transfer pathway, were investigated. The results showed that the determined quantum yields of 3DOM* (Φ3DOM*) for four commercial and four isolated local DOMs are different using HDO ((0.04 ± 0.00) × 10−2 to (2.9 ± 0.17) × 10−2)) and TMP ((0.08 ± 0.01) × 10−2 to (1.2 ± 0.17) × 10−2), respectively. For 17 DOM-analogs, significant differences were also observed with the quantum yields of their 3DOM* determined using HDO (ΦHDO) and the triplet-state quantum yield coefficients determined using TMP (fTMP). It indicates the different reactivity of TMP and HDO with the excited triplet of the chromophores with different structures within the isolated DOM. Based on the experimental and predicted values of fTMP and ΦHDO for different DOM-analogs, the impact of substituents on differences in 3DOM* values were further revealed. These results demonstrated that the levels of 3DOM* depended on the chemical functionalities present in the DOM-analogs. Show less
The spread of antibiotic resistant bacteria (ARB) in the environment poses a potential threat to human health, and the reactivation of inactivated ARB accelerated the spread of ARB. However, little... Show moreThe spread of antibiotic resistant bacteria (ARB) in the environment poses a potential threat to human health, and the reactivation of inactivated ARB accelerated the spread of ARB. However, little is known about the reactivation of sunlight-inactivated ARB in natural waters. In this study, the reactivation of sunlight-inactivated ARB in dark conditions was investigated with tetracycline-resistant E. coli (Tc-AR E. coli) as a representative. Results showed that sunlight-inactivated Tc-AR E. coli underwent dark repair to regain tetracycline resistance with dark repair ratios increasing from (0.124 ± 0.012)‱ within 24 h dark treatment to (0.891 ± 0.033)‱ within 48 h. The presence of Suwannee River fulvic acid (SRFA) promoted the reactivation of sunlight-inactivated Tc-AR E. coli and tetracycline inhibited their reactivation. The reactivation of sunlight-inactivated Tc-AR E. coli is mainly attributed to the repair of the tetracycline-specific efflux pump in the cell membrane. Tc-AR E. coli in a viable but non-culturable (VBNC) state was observed and dominated the reactivation as the inactivated ARB remain present in the dark for more than 20 h. These results explained the reason for distribution difference of Tc-ARB at different depths in natural waters, which are of great significance for understanding the environmental behavior of ARB. Show less
The presence of antibiotic resistance genes (ARGs) in the environment poses a threat to human health and therefore their environmental behavior needs to be studied urgently. A systematic study was... Show moreThe presence of antibiotic resistance genes (ARGs) in the environment poses a threat to human health and therefore their environmental behavior needs to be studied urgently. A systematic study was conducted on the photodegradation pathways of the cell-free tetracycline resistance gene (Tc-ARG) under simulated sunlight irradiation. The results showed that Tc-ARG can undergo direct photodegradation, which significantly reduces its horizontal transfer efficiency. Suwannee River fulvic acid (SRFA) promoted the photodegradation of Tc-ARG and further inhibited its horizontal transfer by generating reactive intermediates. The photodegradation of Tc-ARG was attributed to degradation of the four bases (G, C, A, T) and the deoxyribose group. Quantum chemical calculations showed that the four bases could be oxidized by the hydroxyl radical (HO) through addition and H-abstraction reactions. The main oxidative product 8-oxo-dG was detected. This product was generated through the addition reaction of G-C with HO, subsequent to dissolved oxygen initiated H-abstraction and H2O catalyzed H-transfer reactions. The predicted maximum photodegradation rates of Tc-ARG in the Yellow River estuary were 0.524, 0.937, and 0.336 h−1 in fresh water, estuary water, and seawater, respectively. This study furthermore revealed the microscopic photodegradation pathways and obtained essential degradation parameters of Tc-ARG in sunlit surface water. Show less
Nanoplastics (NPs) have become a new type of pollutant of high concern that is ubiquitous in aqueous environments. However, the transport and transformation of NPs in natural waters are not yet... Show moreNanoplastics (NPs) have become a new type of pollutant of high concern that is ubiquitous in aqueous environments. However, the transport and transformation of NPs in natural waters are not yet fully understood. In this study, the aggregation and photooxidation of NPs were assessed with nanosized polystyrene (PS) as an example, and the effects of dissolved organic matter (DOM) were investigated with Suwannee River fulvic acid (SRFA) as representative DOM. The results showed that simulated sunlight irradiation exhibited negligible effects on the aggregation of PS, while SRFA enhanced its heteroaggregation through hydrophobic interactions. In SRFA solutions, photooxidation of PS with a particle size of 200 nm was observed, which led to an increase in the O/C ratio on its surface at a rate of (2.20 +/- 0.40) x 10(-2) h(-1). This indicates the promotional effect of SRFA on the oxidation of nanosized PS, which is attributed to the generation of the excited triplet state ((3)SRFA*), hydroxyl radicals ((OH)-O-center dot), and singlet oxygen (O-1(2)). Among these reactive species, O-1(2) played a crucial role in the oxidation of PS. The findings in this study are helpful for an in-depth understanding of the environmental behavior of NPs in natural waters. Show less
The development of affordable and efficient technologies for the removal of pharmaceuticals and personal care products (PPCPs) from water has recently been the subject of extensive attention. In... Show moreThe development of affordable and efficient technologies for the removal of pharmaceuticals and personal care products (PPCPs) from water has recently been the subject of extensive attention. In this study, a black phosphorus/graphitic carbon nitride (BP-g-C3N4) heterostructure is fabricated as an extremely active metal-free photocatalyst via a newly-developed exfoliation strategy. The BP-g-C3N4 shows an 11 times better decomposition rate of a representative PPCPs-type pollutant, indomethacin (IDM), compared to the widely used P25 TiO2 under real-sunlight illumination. Also, its visible-light activity is even better than that of the best photocatalysts previously developed, but only consumes 1/10-1/4 of the catalyst. The results show that BP performs a cocatalyst-like behavior to catalyze the generation of reactive oxygen species, thus speeding up the decomposition of IDM. In addition, the BP-g-C3N4 photocatalyst also exhibits excellent IDM removal efficiency in authentic water matrices (tap water, surface water, and secondarily treated sewage effluent). Large-scale application demonstration under natural sunlight further reveals the practicality of BP-g-C3N4 for real-world water treatment operations. Our work will open up new possibilities in the development of purely metal-free photocatalysts for "green" environmental remediation applications. (C) 2021 Elsevier B.V. All rights reserved. Show less
DOM* can not only be regarded as a "controller" of other reactive intermediates, but also effectively promote the photodegradation of bezafibrate, which is classified as a persistent organic... Show moreDOM* can not only be regarded as a "controller" of other reactive intermediates, but also effectively promote the photodegradation of bezafibrate, which is classified as a persistent organic contaminant. This study gives deep insights into effects of UV/chlorine on the photophysical and photochemical properties of DOM, and is helpful for understanding the dynamic roles of DOM in the photodegradation of micropollutants. Show less
The transmission of antibiotic resistance in surface water has attracted much attention due to its increasing threat to human health. The role of sunlight irradiation and the effect of dissolved... Show moreThe transmission of antibiotic resistance in surface water has attracted much attention due to its increasing threat to human health. The role of sunlight irradiation and the effect of dissolved organic matter (DOM) on the transmission of antibiotic resistance are still unclear. In this study, photo-inactivation of antibiotic resistant bacteria (ARB) was investigated using antibiotic resistant E. coli (AR E. coli) that contained the tetracycline resistance gene (Tc-ARG) as a representative. The results showed that AR E. coli underwent significant photo-inactivation due to the membrane damage induced by direct irradiation and by the generated reactive oxygen species. Simulated sunlight irradiation specifically suppressed the expression of tetracycline resistance, which is attributed to the destruction of tetracycline-specific efflux pump. Tetracycline inhibited the photo-inactivation of AR E. coli due to its selective pressure on tetracycline resistant E. coli and competitive light absorption effect. Suwannee River fulvic acid (SRFA), a representative DOM, promoted the inactivation of AR E. coli and further inhibited the expression of tetracycline resistance gene due to the generation of its excited triplet state, singlet oxygen, and hydroxyl radical. The extracellular Tc-ARG also underwent fast photodegradation under light irradiation and in the presence of SRFA, which leads to the decrease of its transformation efficiency. This study provided insight into the sunlight-induced inactivation of ARB, which is of significance for understanding the transmission of tetracycline resistance in surface water. Show less
Mental illness is highly prevalent and runs in families. Mental disorders are considered to enhance the risk for the development of psychopathology in the offspring. This heightened risk is related... Show moreMental illness is highly prevalent and runs in families. Mental disorders are considered to enhance the risk for the development of psychopathology in the offspring. This heightened risk is related to the separate and joint effects of inherited genetic vulnerabilities for psychopathology and environmental influences. The early years of life are suggested to be a key developmental phase in the intergenerational psychopathology transmission. Available evidence supports the idea that early exposure to parental psychopathology, during the pregnancy and first postpartum year, may be related to child psychological functioning beyond the postpartum period, up to adulthood years. This not only highlights the importance of intervening early to break the chain of intergenerational transmission of psychopathology but also raises the question of whether early interventions targeting parental mental disorders in this period may alleviate these prolonged adverse effects in the infant offspring. The current article focuses on the specific risk of psychopathology conveyed from mentally ill parents to the offspring during the pregnancy and first postpartum year. We first present a summary of the available evidence on the associations of parental perinatal mental illness with infant psychological outcomes at the behavioral, biological, and neurophysiological levels. Next, we address the effects of early interventions and discuss whether these may mitigate the early intergenerational transmission of risk for psychopathology. The summarized evidence supports the idea that psychopathology-related changes in parents’ behavior and physiology in the perinatal period are related to behavioral, biological, and neurophysiological correlates of infant psychological functioning in this period. These alterations may constitute risk for later development of child and/or adult forms of psychopathology and thus for intergenerational transmission. Targeting psychopathology or mother-infant interactions in isolation in the postnatal period may not be sufficient to improve outcomes, whereas interventions targeting both maternal psychopathology and mother-infant interactions seem promising in alleviating the risk of early transmission. Show less
