Differences in the response of Chlorella pyrenoidosa to three antidepressants and their mixtures in different light-dark start cycles.

The use of antidepressants is increasing along with the continuing spike in the prevalence of depression worldwide. As a result, more and more antidepressants are entering the water and probably does harm to the aquatic organisms and even human health. Therefore, three antidepressants, including fluoxetine (FLU), citalopram (CIT), and aspirin (APC), were selected to investigate the toxic risks of antidepressants and their mixtures to a freshwater green alga Chlorella pyrenoidosa (C. pyrenoidosa). Due light is critical for the growth of green algae, six different light-dark cycle experiments were constructed to investigate the differences in toxicity and interaction responses of C. pyrenoidosa to antidepressants and their ternary mixture designed by the uniform design ray method. The toxic effects of individual antidepressants and their mixtures on C. pyrenoidosa were systematically investigated by the time-dependent microplate toxicity analysis (t-MTA) method. Toxicity interactions (synergism or antagonism) within mixtures were analyzed by the concentration addition (CA) and the deviation from the CA model (dCA) models. The results showed that the toxicities of the three antidepressants were different, and the order was FLU > APC > CIT. Light-dark cycles obviously affect the toxicity of three antidepressants and their combined toxicity interaction. Toxicity of the three antidepressants increases with the duration of light but decreases with the duration of darkness. The ternary antidepressant mixture exhibits antagonism, and the longer the initial lighting is, the stronger the antagonism. The antagonism of the ternary mixture is also affected by exposure time and mixture components' pi as well as exposure concentration.

The key constituents underlying the combined toxicity of eight cosmetic contaminants towards Vibrio qinghaiensis.

Cosmetic additives (ADDs) and packaging plasticizers (PLAs) probably present potential risks and dangers to the environment and human body as emerging pollutants. To investigate their potential risks and dangers, five ADDs including methyl paraben (MET), ethyl paraben (ETH), propyl paraben (PRO), butyl-hydroxy anisole (BHA), and salicylic acid (SAL), as well as three PLAs including bisphenol A (BPA), bisphenol S (BPS) and tris(2-butoxyethyl) phosphate (TBEP) were selected as research objects, and ten mixture rays (R1-R10) composed of the eight components were designed by the uniform design ray (UD-Ray) method. The toxicities of the eight cosmetic pollutants and their eight-component mixture system towards Vibrio qinghaiensis sp.-Q67 (Q67) were systematically determined by the time-dependent microplate toxicity analysis (t-MTA) method. The three-dimensional (3D) surface of deviation from the concentration addition model (dCA) was utilized to qualitatively and quantitatively analyse the toxicity interaction of the mixtures and the correlation between toxicity interaction and the components' concentration ratios. Finally, eight individual pollutants and representative rays with significant inhibitory and interactive effects were selected to analyse DNA and soluble proteolysis as well as the microstructure and morphology of Q67 after treatment with single chemicals and their mixtures. The results showed that the eight cosmetic pollutants had conspicuous concentration-dependent toxicity and acute toxicity, and none of them, except BPS, BPA and ETH, had time-dependent toxicity. All rays had time/concentration-dependent toxicity and acute toxicity. At the same time, the toxicity interaction of these mixture rays was predominantly antagonism and the strongest antagonism appeared at high concentrations at 12 h. Nevertheless, the components' concentration ratio (pi) was the decisive factor for the type of mixture interaction. The correlation analysis revealed a significant positive linear correlation between mixture toxicity and pETH and pBPA, which indicated that ETH and BPA were the key components of the toxic effects. However, there was a significant negative linear correlation between the antagonism intensity and pBPA and pTBEP, which demonstrated that BPA and TBEP were the key components of the antagonism intensity. Pollutants and their mixtures can also damage cellular structures, and mixtures can exacerbate the dissolution of DNA and soluble proteins.

Quantitative evaluation and the toxicity mechanism of synergism within three organophosphorus pesticide mixtures to Chlorella pyrenoidosa.

Organophosphorus pesticide (OPP) pollutants in the environment pose toxicity risks to living organisms, and the possible toxicity mechanism needs to be further clarified. Therefore, the individual and combined toxicity of three OPPs namely acephate (ACE), trichlorfon (TRI) and glyphosate (GIY) towards a freshwater green alga Chlorella pyrenoidosa (C. pyrenoidosa) was investigated by the time-dependent microplate toxicity analysis method. Here, a ternary mixture system of the three OPPs including five rays with different concentration ratios was designed by the uniform design ray method. The standard additive reference model, concentration addition (CA), was used to analyse toxicity interaction within ternary mixtures and the toxicity interaction intensity was characterized using a deviation from CA model (dCA). Besides, the effects of the three OPPs and their mixtures on the chlorophyll (CHL) content, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content of C. pyrenoidosa were also investigated to explore the possible mechanisms. The results show that toxicity of the three pesticides and their ternary mixture rays is time-dependent and the combined toxicity correlates well with the components, ACE and GLY. It is likely that there is a significant time-dependent synergism in ternary mixtures induced by ACE and GLY. The synergism intensity of the ternary mixtures is not more than 30% at the whole experimental concentration level. The CHL reduction rate and MDA content of C. pyrenoidosa increase, while the SOD activity of C. pyrenoidosa decreases with the lengthening of exposure time under the action of the three pesticides and their ternary mixtures. So, the possible mechanism of the three pesticides and their mixtures may be by affecting the photosynthesis, and then causing oxidative damage to C. pyrenoidosa cells. The results can provide reference for the combined toxicity assessment of OPPs to living organisms.

Online High Temporal Resolution Measurement of Atmospheric Sulfate and Sulfur Trioxide with a Light Emitting Diode and Liquid Core Waveguide-Based Sensor.

High temporal resolution components analysis is still a great challenge for the frontier of atmospheric aerosol research. Here, an online high time resolution method for monitoring soluble sulfate and sulfur trioxide in atmospheric aerosols was developed by integrating a membrane-based parallel plate denuder, a particle collector, and a liquid waveguide capillary cell into a flow injection analysis system. The BaCl2 solution (containing HCl, glycerin, and ethanol) was enabled to quantitatively transform sulfate into a well-distributed BaSO4 solution for turbidimetric detection. The time resolution for monitoring the soluble sulfate and sulfur trioxide was 15 h-1. The limits of detection were 86 and 7.3 µg L-1 ( S/ N = 3) with a 20 and 200 µL SO42- solution injection, respectively. Both the interday and intraday precision values (relative standard deviation) were less than 6.0%. The analytical results of the certificated reference materials (GBW(E)08026 and GNM-M07117-2013) were identical to the certified values (no significant difference at a 95% confidence level). The validity and practicability of the developed device were also evaluated during a firecracker day and a routine day, obviously revealing the continuous variance in atmospheric sulfate and sulfur trioxide in both interday and intraday studies.

High Time-Resolution Optical Sensor for Monitoring Atmospheric Nitrogen Dioxide.

High time-resolution monitoring of nitrogen dioxide (NO2) is of great importance for studying the formation mechanism of aerosols and improving air quality. Based on the Griess-Saltzman (GS) reaction, a portable NO2 optical sensor was developed by employing a porous polypropylene membrane tube (PPMT) integrated gas permeation collector and detector. The PPMT was filled with GS reagents and covered with a coaxial jacket tube for gas collection. Its two ends were respectively fixed with a yellowish-green light-emitting diode and a photodiode for optic signal reception. NO2 was automatically introduced through the collector by two air pumps cooperating with a homemade gas injector. Under the optimized conditions, the device presented good performance for monitoring NO2, such as a limit of detection of 5.1 ppbv (parts per billion by volume), an intraday precision of 4.1% (RSD, relative standard deviation, n = 11, c = 100 ppbv), an interday precision of 5.7% (RSD, n = 2-3 per day for 5 days, c = 100 ppbv), an analysis time of 4.0 min, and a linearity range extended to 700 ppbv. The developed device was successfully applied to analyzing outdoor air with a comparable precision to that of the standard method of China. The high time-resolution characteristic that includes sampling 15 times per hour and a good stability for 10 days of urban air analysis had also been evaluated.

Characterizing the Existence of Fluorescence Quenching Agents Using EEM Fluorescence and UV Spectra: Taking the Interaction of Humic Acid and Fe(â ¢) as an Example.

The fluorescence quenching agents was characterized with three-dimensional fluorescence and ultraviolet (UV) spectra. When there was Fe (Ⅲ) in the sample, the humic fluorescence would be quenched and their UV spectra were not affected. The variation of fluorescence intensity (I) at Ex/Em=300/510 nm and UV absorbance(A) at UV300 were investigated in the article. The smaller the ratio of fluorescence intensity versus UV absorbance (I/A) is, the higher the fluorescence quencher Fe(Ⅲ) concentration is. According to Stern-Volmer equation I/I0=1-fc×Kc×[c] /(1+Kc×[c] ) and fitted function I/A=f×[k/(cFe3++c)+b] , the fitted fluorescent quenching constant Kc was ranged between 1.08 to 1.15, the ratio of bounded fluorophores versus total fluorophores, i.e. fc, was ranged between 1.10 to 1.14. The ratio of fluorescence intensity and absorbance of humic acid was fitted with Fe(Ⅲ) concentration and the constants were acquired as following: f=0.83～1.19, k=587.19～612.19, c=0.87～0.92, b=-87.09～-46.36. The correlation curve values were 0.99. The Stern-Volmer formula was used to describe the quenching effect of humic acid fluorescence by Fe (Ⅲ). However, due to the fact that the fluorescence intensity I0 without quencher was difficult to acquire during the analysis of practical samples, the fitted function between the ratio of I/A and Fe(Ⅲ) was used to reflect the quenching effect of Fe(Ⅲ) on the fluorescence of humic acid, which was based on the correlations between the fluorescence intensity I0 and ultraviolet absorbance A. The fitted formula was used to predict the iron ions concentration of the resin separated and concentrated samples from wastewater treatment plant and receiving waters. The predicted values were in good accordance with those determined with inductively coupled plasma atomic emission spectroscopy(ICP-AES) method when the iron ion concentration was above 0.4 mg·L-1, which could be used to ascertain the existence of fluorescence quenching agent and their corresponding concentration.

Polyhedral Oligomeric Silsesquioxane Polymer-Caged Silver Nanoparticle as a Smart Colorimetric Probe for the Detection of Hydrogen Sulfide.

The rapid and accurate detection of hydrogen sulfide is of great concern due to its unique role on environmental pollution and signal transmission in physiological systems. Herein, we report a smart colorimetric probe for the selective detection of H2S. The probe is prepared via a surfactant-free route with cross-linked polyhedral oligomeric silsesquioxane (POSS) polymer cage as capping ligand and reducing agent under microwave irradiation, called poly-POSS-formaldehyde polymer (PPF) cage-AgNPs or PPF-AgNPs for short. The caged silver nanoparticles are well-dispersed with narrow size distribution within 6.0-8.4 nm. Chloride ions and aldehyde groups in PPF make the nucleation and growth of Ag nanoparticles accomplished within a very short time of 1 min. The positively charged PPF-AgNPs exhibit excellent selectivity to H2S against other anionic species and thiols due to the specific Ag-H2S interaction, where the favorable protection effect of PPF polymer cage from the nanoparticle aggregation is demonstrated. The colorimetric probe presents a quick response to H2S (<3 min) and favorable sensitivity within a linear range of 0.7-10 µM along with a detection limit of 0.2 µM. The probe is well demonstrated by analysis of H2S in various water and biological samples.