Photodegradation of salicylic acid in aquatic environment: effect of different forms of nitrogen

Effects of staged multiple phytohormones application on capillary-driven attached Chlorella sp. biofilm

Comparing with single phytohormone application, applying multiple phytohormones to microalgae-based wastewater treatment systems can offer more extensive growth-promoting and stress-protecting effects for microalgae, yet the advantage of stress-relieving salicylic acid (SA) under combined phytohormones application scenario has not been exploited. Employing the improved capillary-driven attached microalgae culturing device (CD-PBR) previously used for single phytohormone application, this study compared the effects of mixed and single phytohormone(s) addition under as low as 10-7 M dosage. In order to make the best of SA for its stress-relieving property, postponed SA addition combined with applying other phytohormone(s) at the beginning of microalgae cultivation was also investigated. Combination of 10-6 M 6-benzylaminopurine (6-BA) with 10-7 M SA was sufficient for enhancing growth-promoting effects and anti-oxidative responses for attached Chlorella sp., while indole-3-acetic acid (IAA) addition was unnecessary. Combination of 6-BA addition at the beginning while postponed SA addition on Day 4 could further sustain such beneficial effects, while removing up to 99.7% total nitrogen (TN) and 97.9% total phosphorus (TP) from the bulk liquid. These results provided innovative strategies on mixed phytohormones addition for microalgae.

Highly Selective and Rapid "Turn-On" Fluorogenic Chemosensor for Detection of Salicylic Acid in Plants and Food Samples

Salicylic acid (SA) is one of the chemical molecules, involved in plant growth and immunity, thereby contributing to the control of pests and pathogens, and even applied in fruit and vegetable preservation. However, only a few tools have ever been designed or executed to understand the physiological processes induced by SA or its function in plant immunity and residue detection in food. Hence, three Rh6G-based fluorogenic chemosensors were synthesized to detect phytohormone SA based on the "OFF-ON" mechanism. The probes showed high selectivity, ultrafast response time (<60 s), and nanomolar detection limit for SA. Moreover, the probe possessed outstanding profiling that can be successfully used for SA imaging of callus and plants. Furthermore, the fluorescence pattern indicated that SA could occur in the distal transport in plants. These remarkable results contribute to improving our understanding of the multiple physiological and pathological processes involved in SA for plant disease diagnosis and for the development of immune activators. In addition, SA detection in some agricultural products used probes to extend the practical application because its use is prohibited in some countries and is harmful to SA-sensitized persons. Interestingly, the as-obtained test paper displayed that SA could be imaged by ultraviolet (UV) and was directly visible to the naked eye. Given the above outcomes, these probes could be used to monitor SA in vitro and in vivo, including, but not limited to, plant biology, food residue detection, and sewage detection.

Effects of environmental factors on the fleroxacin photodegradation with the identification of reaction pathways

The abuse of fluoroquinolones (FQs) antibiotics leads to bacterial resistance and environmental pollution, so it is of great significance to verify the decomposition mechanism for eliminating antibiotic efficiently and conveniently. The effects of various environmental factors and the fleroxacin (FLE) photodegradation mechanisms were investigated by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS), UV-Vis absorption spectroscopy, fluorescence spectroscopy and quantum chemical calculation. Six possible photodegradation reaction paths on T₁ (excited triplet state) were proposed and simulated. The departure of the piperazine ring and the substitution of F atom at C-6 position by OH group were determined as the main reactions based on the reaction rates and energy barriers of each path. The multi-pathway reactions resulted in the fastest photodegradation rates of FLE at pH 6-7 than other pH conditions. NaN₃ would promote FLE photodegradation by inhibiting the reverse reaction of the separation process of F atom at C-8 and the generation of biphenyl molecules, which was a novel and distinctive phenomenon in this report. ·OH would rapidly combine with the free radicals generated in photolysis processes and made a great contribution to FLE photodegradation. Ca²⁺, Mg²⁺ and Ba²⁺ could stabilize the carboxyl group to impede the photo-competitive process of the decarboxylation reaction, while NO₃^- could generate reactive oxygen species to promote photodegradation.

Toxicity of two drugs towards the marine filter feeder Mytilus spp, using biochemical and shell integrity parameters

The increasing presence of anthropogenic contaminants in the environment may constitute a challenge to non-target biota, considering that most contaminants can exert deleterious effects. Salicylic acid (SA) is a non-steroid anti-inflammatory drug (NSAID) which exerts its activity by inhibiting the enzyme cyclooxygenase (COX). Another class of drugs is that of the diuretics, in which acetazolamide (ACZ) is included. This pharmaceutical acts by inhibiting carbonic anhydrase (CA), a key enzyme in acid-base homeostasis, regulation of pH, being also responsible for the bio-availability of Ca²⁺ for shell biomineralization processes. In this work, we evaluated the chronic (28-day) ecotoxicological effects resulting from the exposures to SA and ACZ (alone, and in combination) on individuals of the marine mussel species Mytillus spp., using enzymatic (catalase (CAT), glutathione S-transferases (GSTs), COX and CA), non-enzymatic (lipid peroxidation, TBARS levels) and morphological and physiological (shell hardness, shell index and feeding behaviour) biomarkers. Exposure to ACZ and SA did not cause significant alterations in CAT and GSTs activities, and in TBARS levels. In terms of CA, this enzyme was inhibited by the highest concentration of ACZ in gills of exposed animals, but no effects occurred in the mantle tissue. The activity of COX was not altered after exposure to the single chemicals. However, animals exposed to the mixture of ACZ and SA evidenced a significant inhibition of COX activity. Morphological and physiological processes (namely, feeding, shell index, and shell hardness) were not affected by the here tested pharmaceutical drugs. Considering the general absence of adverse effects, further studies are needed to fully evaluate the effects of these pharmaceutical drugs on alternative biochemical and physiological pathways.

Photolysis-Induced Neurotoxicity Enhancement of Chlorpyrifos in Aquatic System: A Case Investigation on Caenorhabditis elegans

Contamination of the environment by toxic pesticides has become of great concern in agricultural countries. Chlorpyrifos (CP) is among the pesticides most commonly detected in the environment owing to its wide agricultural applications. The aim of this study was to compare potential changes in the toxicity of CP after irradiation. To this end, photolysis of CP was conducted under simulated sunlight, and neurotoxicity assessment was carried out at CP of 20 and 50 μg L^-1 and its corresponding irradiated mixture solutions which contain a mixture of identified intermediates using the nematode, Caenorhabditis elegans as a model organism. Photodegradation of 20 μg L^-1 CP for 1 h produced no obvious reduction of physiological damage, and more serious effects on animal movement were detected after exposure of the animals to a solution of 50 μg L^-1 for 1 h irradiation compared with unirradiated solution. GABAergic and cholinergic neurons were selectively vulnerable to CP exposure, and maximal neuropathological alterations were observed after 1 h irradiation of the CP solutions in coherence with the behavioral impairment. The generation of photoproducts was considered to be responsible for the enhanced disturbance on those biological processes. This work provided useful information on the toxicological assessments of chemicals that were produced during the environmental transformation of pesticides.

Photodegradation of tefuryltrione in water under UV irradiation: Identification of transformation products and elucidation of photodegradation pathway

Photodegradation is an important abiotic degradation process in the aquatic environment. In this study, the photodegradation of tefuryltrione in aqueous solution was investigated under UV-Visible irradiation. Effects of carbonate (CO₃^2-), bicarbonate (HCO₃^-), nitrate (NO₃^-), hydrogen phosphate (HPO₄^2-), potassium (K⁺), and ammonium (NH₄⁺) on the photodegradation kinetics of tefuryltrione were evaluated. Results showed that tefuryltrione photodegradation was increased by HCO₃^-, CO₃^2-, and NO₃^- in the range of 0.1-10 mmol L^-1; decreased by HPO₄^2-; and insignificantly affected by K⁺ and NH₄⁺. Twelve main transformation products (TPs) were separated and identified on the basis of mass spectrum data assigned by elemental-composition calculations, comparison of structural analogs, and available literature. A tentative photodegradation pathway was further proposed depending on the identified TPs and their kinetic evolutions. Results indicated that TP 1 was generated by the hydroxyl that substituted for chlorine, TP 2 was formed by the cleavage of the ether bond of tefuryltrione, and TPs 3-6 were formed by the breakage of the CC bond of the keto moiety of tefuryltrione. Further, TPs 9-12 were formed by the rearrangement of tefuryltrione-photodegradation products. These findings are highly important for elucidating the environmental fate of tefuryltrione in aquatic ecosystems.

Identification and Characterization of Herbicide Penoxsulam Transformation Products in Aqueous Media by UPLC-QTOF-MS

Photodegradation is an important non-biodegradation process of pesticide degradation in aquatic environments. In this study, the effect of different forms of nitrogen on the photodegradation kinetics of penoxsulam was investigated. The photodegradation of penoxsulam was accelerated by NO^3- and NO^2- but was not affected by NH⁴⁺. Ultra-high-performance liquid chromatography coupled with time-of-flight mass spectrometry was used to separate and identify the transformation products (TPs)converted by photodegradation of penoxsulam in an aqueous solution under UV-Vis (290-800 nm) irradiation. Seven major transformation products were identified based on mass spectral data. The structure was determined by elemental composition calculations, comparison of structural analogs, and existing literature. The main pathways of photodegradation were found to be sulfonamide bond cleavage, rearrangement, triazole ring cleavage, and hydroxylation. These findings are critical to elucidate the environmental fate of penoxsulam in aquatic ecosystems and provide a basis for further environmental risk assessment.

Direct and indirect photolysis of the antibiotic enoxacin: kinetics of oxidation by reactive photo-induced species and simulations

The purpose of this study was to investigate the aqueous phase photochemical behavior of enoxacin (ENO), an antibiotic selected as a model pollutant of emerging concern. The second-order reaction rate constants of ENO with hydroxyl radicals (HO^●) and singlet oxygen (¹O₂) were determined at pH 3, 7, and 9. Also, the rate constants of the electron transfer reaction between ENO and triplet states of chromophoric dissolved organic matter (³CDOM*) are reported for the first time, based on anthraquinone-2-sulfonate (AQ2S) as CDOM proxy. The sunlight-driven direct and indirect ENO degradation in the presence of dissolved organic matter (DOM) is also discussed. The results show that direct photolysis, which occurs more rapidly at higher pH, along with the reactions with HO^● and ³AQ2S*, is the key pathway involved in ENO degradation. The ENO zwitterions, prevailing at pH 7, show k_ENO, HO^●, k_ENO,1O2, and k_ENO,3AQ2S* of (14.0 ± 0.8) × 10¹⁰, (3.9 ± 0.2) × 10⁶, and (61.5 ± 0.7) × 10⁸ L mol^-1 s^-1, respectively, whose differences at pH 3, 7, and 9 are due to ENO pH-dependent speciation and reactivity. These k values, along with the experimental ENO photolysis quantum yield, were used in mathematical simulations for predicting ENO persistence in sunlit natural waters. According to the simulations, dissolved organic matter and water depth are expected to have the highest impacts on ENO half-life, varying from a few hours to days in summertime, depending on the concentrations of relevant waterborne species (organic matter, NO₃^-, NO₂^-, HCO₃^-).

Determination of pharmaceuticals in groundwater collected in five cemeteries' areas (Portugal)

There are growing public attention and concern about the possibility of ecosystem and human health effects from pharmaceuticals in environment. Several types of environmental samples were target of studies by the scientific community, namely drinking water, groundwater, surface water (river, ocean), treated water (influent and effluent), soils, and sediments near to Wastewater Treatment Plants or near to others potential sources of contaminations. Normally, studies in the cemeteries areas are for historical and architectural research and questions of the potential risk for adverse impact of cemeteries in environment have never received enough attention. However, this risk may exist when cemeteries are placed in areas that are vulnerable to contamination. The objective of the present work was the determination of pharmaceuticals (nonsteroidal anti-inflammatory/analgesics, antibiotics and psychiatric drugs) in groundwater samples collected inside of the cemeteries areas. Acetaminophen, salicylic acid, ibuprofen, ketoprofen, nimesulide, carbamazepine, fluoxetine, and sertraline were the pharmaceuticals achieved in the analysed samples. None of the studied antibiotics were detected. The highest concentration was obtained for salicylic acid (in the range of 33.7 to 71.0ng/L) and carbamazepine (between 20.0 and 22.3ng/L), respectively. By the cluster analysis similarity between carbamazepine and fluoxetine was achieved.

Investigation of pharmaceuticals, personal care products and endocrine disrupting chemicals in a tropical urban catchment and the influence of environmental factors

Previous studies showed the presence of multiple emerging organic contaminants (EOCs) in urban surface waters of Singapore even though there are no obvious direct wastewater discharges. In this study, we investigated the occurrence and distribution of 17 pharmaceuticals and personal care products (PPCPs) and endocrine disruptive compounds (EDCs) in a tropical urban catchment of Singapore. Monthly samples were collected from a reservoir and its 5 upstream tributaries during a 16-month period. Analysis of samples showed all sites had measurable PPCP and EDC concentrations, with caffeine (33.9-2980 ng/L), salicylic acid (5-838 ng/L), acetaminophen (<4-485.5 ng/L), BPA (<2-919.5 ng/L) and DEET (13-270 ng/L) being the most abundant. Marked differences in concentrations of target analytes between the reservoir and upstream tributaries were observed, and were tentatively attributed to the spatial differences in source inputs, water dilution capacity as well as natural attenuation of EOCs. Significant correlations between EOCs and conductivity, dissolved oxygen, chlorophyll a, turbidity, nutrients and cumulative precipitation were observed. These factors appeared to affect the distribution and attenuation of EOCs, depending on their physicochemical properties. Rainfall also influenced the temporal distribution of caffeine, BPA, triclosan, fipronil and DEET in the reservoir. Ecological risk assessment showed that caffeine, acetaminophen, estrone, BPA, triclosan and fipronil may warrant further survey. In particular, BPA levels exceeded the literature-based Predicted No-Effect Concentration (PNEC) value, highlighting the need for source control and/or water remediation in this urban catchment.

Global risk of pharmaceutical contamination from highly populated developing countries

Global pharmaceutical industry has relocated from the west to Asian countries to ensure competitive advantage. This industrial relocation has posed serious threats to the environment. The present study was carried out to assess the possible pharmaceutical contamination in the environment of emerging pharmaceutical manufacturing countries (Bangladesh, China, India and Pakistan). Although these countries have made tremendous progress in the pharmaceutical sector but most of their industrial units discharge wastewater into domestic sewage network without any treatment. The application of untreated wastewater (industrial and domestic) and biosolids (sewage sludge and manure) in agriculture causes the contamination of surface water, soil, groundwater, and the entire food web with pharmaceutical compounds (PCs), their metabolites and transformed products (TPs), and multidrug resistant microbes. This pharmaceutical contamination in Asian countries poses global risks via product export and international traveling. Several prospective research hypotheses including the development of new analytical methods to monitor these PCs/TPs and their metabolites, highly resistant microbial strains, and mixture toxicity as a consequence of pharmaceutical contamination in these emerging pharmaceutical exporters have also been proposed based on the available literature.

Influence of pH, inorganic anions, and dissolved organic matter on the photolysis of antimicrobial triclocarban in aqueous systems under simulated sunlight irradiation

The photolysis of the antimicrobial triclocarban (TCC) in aqueous systems under simulated sunlight irradiation was studied. The effects of several abiotic parameters, including solution pH, initial TCC concentration, presence of natural organic matter, and most common inorganic anions in surface waters, were investigated. The results show that the photolysis of TCC followed pseudo-first-order kinetics. The TCC photolysis rate constant increased with increasing solution pH and decreasing the initial TCC concentration. Compared with the TCC photolysis in pure water, the presence of aqueous bicarbonate, nitrate, humic acids, and its sodium salt decreased the TCC photolysis rate, but fulvic acid increased the TCC photolysis rate. The electron spin resonance and reactive oxygen species scavenging experiments indicated that TCC may undergo two different types of phototransformation reactions: direct photolysis and energy transfer to generate (1)O2. The main degradation products were tentatively identified by gas chromatography interfaced with mass spectrometry (GC-MS), and a possible degradation pathway was also proposed.

A critical assessment of the photodegradation of pharmaceuticals in aquatic environments: defining our current understanding and identifying knowledge gaps

This work presents a critical assessment of the state and quality of knowledge around the aquatic photochemistry of human- and veterinary-use pharmaceuticals from laboratory experiments and field observations. A standardized scoring rubric was used to assess relevant studies within four categories: experimental design, laboratory-based direct and indirect photolysis, and field/solar photolysis. Specific metrics for each category are defined to evaluate various aspects of experimental design (e.g., higher scores are given for more appropriate characterization of light source wavelength distribution). This weight of evidence-style approach allowed for identification of knowledge strengths and gaps covering three areas: first, the general extent of photochemical data for specific pharmaceuticals and classes; second, the overall quality of existing data (i.e., strong versus weak); and finally, trends in the photochemistry research around these specific compounds, e.g. the observation of specific and consistent oversights in experimental design. In general, those drugs that were most studied also had relatively good quality data. The four pharmaceuticals studied experimentally at least ten times in the literature had average total scores (lab and field combined) of ≥29, considered decent quality; carbamazepine (13 studies; average score of 31), diclofenac (12 studies; average score of 31), sulfamethoxazole (11 studies; average score of 34), and propranolol (11 studies; average score of 29). Major oversights and errors in data reporting and/or experimental design included: lack of measurement and reporting of incident light source intensity, lack of appropriate controls, use of organic co-solvents in irradiation solutions, and failure to consider solution pH. Consequently, a number of these experimental parameters were likely a cause of inconsistent measurements of direct photolysis rate constants and quantum yields, two photochemical properties that were highly variable in the literature. Overall, the assessment rubric provides an objective and scientifically-defensible set of metrics for assessing the quality of a study. A major recommendation is the development of a method guideline, based on this rubric, for conducting and reporting on photochemical studies that would produce consistent and reliable data for quantitative comparison across studies. Furthermore, an emphasis should be placed on conducting more dual-fate studies involving controlled photolysis experiments in natural sunlight, and whole system fate studies in either natural or artificial systems. This would provide accurate data describing the actual contribution of photolysis to the overall fate of pharmaceuticals in the environment.