تهدف الدراسة الحالية إلى تصنيع دقائق الفضة النانوية (AgNPs) حيوياً باستخدام الأيوض الخارج خلوية للبكتيريا البحرية Kocuria flava (F57)، وأستخدامها لتعزيز فعّالية المضاد الحيوي السيبروفلوكساسين تجاه البكتيريا المرضية ذات المقاومة المتعددة للمضادات الحيوية (MDR). جُمعت عينّات المياه البحرية من المياه البحرية العراقية خلال شهر كانون الثاني/2022. تم تشخيص العزلةF57 من خلال الصفات المجهرية، وبعض الاختبارات الكيموحيوية، والتشخيص الجزيئي بتضخيم الجين 16S rDNA، وظهر من خلال رصف تسلسلات القواعد النايتروجينية للجين 16S rDNA مع تلك العائدة للسلالات المسجّلة في بنك الجينات NCBI، وشجرة النشوء والتطور، وجود تطابق نسبته 99.93% مع السلالة K. flava AUMC B-459. أظهرت نتائج قياس الطيف الكتلي GC/MS لمستخلص العزلة F57 وجود ثلاثين مركباً. أُستخدمت الأيوض الخارج خلوية للعزلة F57 لتصنيع دقائق الفضة النانوية، وتم التأكد من نجاح عملية تصنيع الحيوي عن طريق التحليل الطيفي للضوء المرئي- الأشعة فوق البنفسجية وطيف الأشعة تحت الحمراء وحيود الأشعة السينية والمجهر الإلكتروني الماسح وطاقة تشتت طاقة الأشعة السينية. أظهرت دقائق الفضة النانوية فعّالية تجاه خمس عزلات من البكتيريا المرضية ذات المقاومة المتعددة للمضادات الحيوية وهي كلٌ من:Klebsiella pneumoniae ، Pseudomonas aeruginosa ، Staphylococcus haemolyticus ، وعزلتان من البكتيريا Escherichia coli (1&2)، تم تحديد التركيز المثبّط الأدنى لدقائق الفضة النانوية والمضاد الحيوي Ciprofloxacin ومزيجهما معاً ضد العزلات البكتيرية المرضية أعلاه، وكانت العزلة P. aeruginosa هي الأكثر حساسية لدقائق الفضة النانوية، إذ كان التركيز المثبطّ الأدنى تجاهها 7.81 مايكروغرام/مل، وكانت جميع العزلات البكتيّرية المرضية مقاومة للمضاد الحيوي Ciprofloxacin، وأظهرت نتائج مزج المضاد الحيوي Ciprofloxacin مع دقائق الفضة النانوية وجود تأثير تآزري تجاه العزلات المرضية P. aeruginosa و S. haemolyticus وE. coli (2) ، وأصبحت العزلتين E. coli (1&2) حساسة لهذا المضاد الحيوي بعد عملية المزج. لذا فإن دقائق الفضة النانوية المخلّقة حيوياً بإستخدام الأيوض الخارج خلوية للبكتيريا البحرية K. flava (F57) ذات خصائص مضادة للبكتيريا المرضية، وقد أسهمت في تعزيز فعّالية المضاد الحيوي Ciprofloxacin.

In this study, the aqueous extract of (Typha domingensis Pers.) pollen grain (qurraid) to know its ability to manufacture silver nanoparticles. Qurraid is a semi-solid yellow food substance, sold in Basra markets and eaten by the local population. It is made from the pollen of the T. domingensis Pers. plant after being pressed and treated with water vapor. The Gas chromatography–mass spectrometry (GC-MS) reaction was done to identify the active compounds of qurraid aqueous extract. The ability of the aqueous extract of qurraid to manufacture silver nanoparticles was tested, and the construction of silver nanoparticles was inferred by the reaction mixture's color, which ranged from yellow to dark brown. The synthesized silver nanoparticles (AgNPs) were described by UV-Vis, FTIR, XRD, SEM, and EDX. Then its anti-bacterial activity was estimated by the agar well diffusion method. The findings of the GC-MS analysis of the qurraid aqueous extract showed the major components with their ratio were: 5-Hydroxymethylfurfural with RT% 13.6196, 3-Deoxy-d-mannoic lactone 6.4285,. alpha.-L-lyxo-Hexopyranoside, methyl 3-amino-2,3,6-trideoxy- 4.264, 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- 3.2078, and 1,3-Methylene-d-arabitol 3.1257. The construction of silver nanoparticles was described by spectroscopic methods, where the highest peak was recorded at 400nm by UV-Vis spectrum, which indicates the silver spectrum. The mineral nature of AgNPs was confirmed by XRD analysis, in which the highest peaks were, 111, 300, and 330 were recorded. In addition, the qrdAgNPs nanoparticles were spherical with sizes ranging from 20-70nm. The results of the EDX confirmed that the chemical composition of AgNPs was silver. The ability of the AgNPs was tested against four bacterial species, three of which were Gram-negative Escherichia coli A1, Escherichia coli A2, Alcaligenes faecalis AL1, and the fourth was Gram-positive bacteria Bacillus zanthoxyli B1 , which were identified by traditional and molecular methods using 16SrRNA gene sequencing, antibacterial activity results of AgNPs showed that it increases with increasing of AgNPs concentration, and the most sensitive species to silver particles was Alcaligenes faecalis AL1bacteria.

Nanoparticle applications are growing due to the unique properties that nanoparticles possess, which have gained the attention of researchers, and one of these applications is the use of inhibiting antibiotic-resistant bacteria. The current work aims to biosynthesize silver nanoparticles from the fruits of the okra plant Abelmoschus esculentus (L.) Moench and test their antibacterial activity alone or in combination with some antibiotics. The creation of silver nanoparticles was confirmed by altering the color of the mixture from light green to dark brown, in addition to employing spectroscopic methods to prove and explain the production of these particles, such as UV-vis, FTIR, XRD, and EDX. Scanning electron microscopy (SEM) was used to determine the shape and sizes of the particles created in the current study. The synthesized silver nanoparticles were tested alone or in combination with some antibiotics for their ability to inhibit four species of antibiotic-resistant MDR bacteria, three of which were Gram-negative and the fourth was Gram-positive bacteria. The results demonstrated that these bacteria were inhibited when using nanoparticles at all concentrations alone or in combination with antibiotics. AgNPs were found to be more effective against Gram-positive bacteria than Gram-negative bacteria. Therefore, Staphylococcus auricularis (8F) was the most sensitive bacteria at all concentrations, while Escherichia coli (3R) was the most resistant. The results of the combination of AgNPs with some antibiotics revealed that the best synergy was recorded when AgNPs mixed with Amoxicillin clavulanate against all species of Gram-negative bacteria, followed by ciprofloxacin, Ampicillin, and Fosfomycin.

PurposeBacteria are known to have a high ability to manufacture many compounds with biological functions in a short time compared with eukaryotic cells due to the fact that bacterial cells possess efficient metabolic mechanisms for the manufacture of these compounds (intracellular or extracellular). Herein, the goal of this study is to use pathogenic Enterococcus aerogenes bacteria strains, namely, S1, S2, and S3, isolated from the mouths of individuals with dental decay to produce silver nanoparticles in an environmentally friendly and cost-effective manner.MethodsThese nanoparticles have been tested for antibacterial activity against Streptococcus mitis, an MDR bacterium, either alone or in combination with antibiotics. These bacteria were identified using morphological characteristics and biochemical tests, in addition to molecular methods such as PCR and DNA sequences. Besides, their identification was done on the basis of their alignment with the reference strains in the NCBI blast to calculate the degree of similarity among these strains (S1, S2, and S3).ResultsThe results of the current study showed a clear synergistic effect in the inhibition of Streptococcus mitis bacteria when mixing silver nanoparticles with some antibiotics, and it was found that there is a synergistic effect when mixing those AgNPs with erythromycin, followed by streptomycin and tetracycline. In contrast, the effect was antagonistic in the case of streptomycin and tetracycline antibiotics.ConclusionEnterobacter aerogenes AgNPs demonstrated excellent antibacterial efficacy on Streptococcus mitis isolates. Therefore, AgNPs in the dental care area have a wide range of applications.Lay SummaryThe current study attempted to show how AgNPs have a broad range of uses in the dental care field. Therefore, the study employed AgNPs that were created by Enterobacter aerogenes bacterial strains (S1, S2, and S3) for dental caries patients. AgNPs from Enterobacter aerogenes exhibited strong antibacterial activity against Streptococcus mitis isolates.

The goal of this research is to use dental caries patients’ oral cavity-isolated Enterobacter aerogenes bacterial strains (S1, S2 and S3) to create silver nanoparticles (AgNPs) in an environmentally friendly and cost-effective manner. In addition, the study explores the combination of antibiotics with Streptococcus mitis MDR, which was isolated from patients with dental caries to determine their antibacterial efficiency. Clinical bacterial strains identified from dental caries patients' mouths were all resistant to standard antibiotics. Antibiotics and AgNPs have a synergistic impact, which suggests that antibiotics will make up a larger portion of the diet. It was shown that erythromycin E had the greatest synergistic impact with AgNPs (0.1 mg/ml), but Streptomycin and Tetracycline had only 6 mm inhibitory zones when paired with AgNPs (0.1 mg/ml) in comparison. Antagonizing effects are meant by this. It was revealed that antibiotics such as penicillin P and cephalexin CN had distinct effects on patients. When used in combination with antibiotics, Enterobacter aerogenes AgNPs demonstrated excellent antibacterial efficacy on Streptococcus mitis isolates. As a result, AgNPs in the dental care area have a wide range of applications.

The synthesis of nanoparticles by green method using plant extracts and its application in the biomedical consider a prosperous field of research. Therefore, in this paper, Rheum plant was used as a reducing agent in synthesis silver nanoparticles and testing its effectiveness as anti-fungal. Silver Nanoparticles have been characterized using different techniques such as UV-visible spectroscopy, X-ray diffraction, Fourier transforms infrared spectroscopy and transmission electron microscope. Where the result of the examination UV-Vis showed absorption peaks of silver nanoparticles which formatted at wavelength (425) and XRD test confirmed the presence of silver nanoparticles clearly through compare peaks resulted with JCPDS card. It revealed the spectra of FTIR the existence of amine and aliphatic esters, that are involved in reducing and stabilizing AgNPs. Examination of TEM revealed that the silver nanoparticles were spherical shape and with an average size of 5-45 nm. Finally, the synthesized silver nanoparticles showed a good antifungal activity against some Candida sp. by observe inhibition zones that obtained.

Antibiotics resistant bacteria have become a global problem as a result of the unprogrammed use of antibiotics, resulting in bacterial strains resistant to many antibiotics, or to all available antibiotics. Plants are a good source of primary and secondary metabolites that have a major role in reducing silver nitrate to silver nanoparticles (AgNPs). The production of these nanoparticles were carried out by using aqueous extract of Carthamus oxycantha M.Bieb. This can be verified by color change of the reaction solution from yellow to dark brown because of the excitation of the surface plasmon resonance. AgNPs were characterized by UV-Vis spectroscopy, where they recorded the peak at 420 nm. Fourier Transformation-infrared (FTIR) was conducted to identify the effective plant group that contributes to the formation of AgNPs and it was found that proteins and phenols have the major role in the formation of those nanoparticles. Shapes and sizes of the synthesized AgNPs were characterized by Scanning Electron Microscope (SEM) with a range of 50-80nm in size and spherical in shapes. Antibacterial activity of AgNPs were tested against Multi-Drug Resistant bacteria (MDR), Extremely antibiotics Resistant (XDR), and Pan drug-resistant (PAN) bacteria, was done in concentrations ranging from 1000-63 µg/ml. The results showed that there were significant variations between the concentrations, the tested bacteria also showed significant differences in its sensitivity to AgNPs. The results recorded a proportional relation between the type of bacterial resistance to antibiotics and it's resistant to AgNPs, therefore the most resistant bacteria to AgNPs in this study Enterobacter cloacae EN2 was resistant to all antibiotics (PAN), while Escherichia coli E11 recorded was the most sensitive bacteria to AgNPs and its resistant only to 3 antibiotics. unprogrammed use of antibiotics, resulting in bacterial strains resistant to manyantibiotics, or to all available antibiotics. Plants are a good source of primary andsecondary metabolites that have a major role in reducing silver nitrate to silvernanoparticles (AgNPs). The production of these nanoparticles were carried out by usingaqueous extract of Carthamus oxycantha M.Bieb. This can be verified by color changedof the reaction solution from yellow to dark brown because of the excitation of thesurface plasmon resonance. AgNPs were characterized by UV-Vis spectroscopy, whererecorded peak at 425 nm. Fourier Transformation-infrared (FTIR) was conducted toidentify the effective plant group that contributes to the formation of AgNPS and it wasfound that proteins and phenols have the major role in the formation of thosenanoparticles. Shapes and sizes of synthesized AgNPs were characterized by ScanningElectron Microscope (SEM) with a range of 50-80nm in size and spherical in shapes.Antibacterial activity of AgNPs were tested against Multi-Drug Resistant bacteria(MDR), Extremely antibiotics Resistant (XDR), and Pandrug-resistant (PAN) bacteria,was done in concentrations ranging from 1000-63 µg/ml. The result showed that theconcentrations from 1000-125 µg/ml inhibited all tested bacterial strains except the S1strain

In the current study, water was used as a solvent to extract biomolecules of the shoot of Sedilitizia rosmarinus plant to reduce silver nitrate to silver nanoparticles (AgNPs). The extract was filtered and left for 24 hours, two distinguished layers were formed, a green top layer called supernatant (sup) and a white precipitate layer named sediment (sed) layer, both layers were used separately in the biogenic synthesis of AgNPs. GCMS analysis was performed to find out the content of biomolecule compounds present in both layers (sup and sed). To characterize of AgNPs, various spectroscopic methods have been used: Ultraviolet-Visible spectroscopy (UVvis), Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), scanning electron microscope (SEM). Uv-vis results of AgNPs (supAgNPs and sedAgNPs) showed peaks at 420 and 425 nm respectively. FTIR results proved that the biomolecules present in both layers contributed to the reduction and capping of silver nitrate to AgNPs. XRD study demonstrated the crystalline nature of AgNPs manufactured in the current study with a face center cubic (FCC) structure. Spherical AgNPs shape with size ranging from 45-99, and 5896 nm for supAgNPs and sedAgNPs respectively done by SEM microscope. Antibacterial activity of AgNPs shows a significant inhibition against multidrugresistant bacteria (MDR) and concentrations. Staphylococcus aureus was recorded as the most susceptible bacteria with an inhibition zone diameter of 22 mm with a mean rank (3.45), followed by E.coli, Staphylococcus hominus, and Proteous mirabilis with mean rank 2.96, 2.21, and 1.39 respectively.

Aims: The main aims of thisstudyis to isolate pathogenic bacteria from packed milk in Basrah city, and to detect the presence of formalin in milk samples.Methodology:A total of 9types of packed milk were collected from the market in different period. The samples were transported to the laboratory in cooling conditions. They were stored in a refrigerator and analyzed within 24 hours. One ml from each sample was diluted in 9ml sterile distilled water, the diluted sample was a streak inoculated on chromogenic media. Three ml of milk sample was taken in a test tube and diluted with equal size of water. 5ml of sulfuric acid (90%) were added to the diluted milk slowly to the side of test tube which must handle with slant position in order to form separation layer. In case of formaldehyde presence a violet layer will form. This method detect of 1 part of formaldehyde in 200000 parts of milkResult: The result showed only Staphylococcus saprophyticus and Staphylococcus aureus have been isolated from milk samples (23.4 %) and (10.6 %) respectively. The result showed that high temperature not very effective since two pathogenic bacterial species have been isolated and formalin have been detected in milk samples. The result showed no effect of addition of formalin in some sample and did not inhibit the growth of bacteria.Conclusions: This study concludes that most of the packed milk under study contaminated with some pathogenic bacterial species, most of milk samples contained formalin.

Energy minimization is of great importance in wireless sensor networks in extending the battery lifetime. One of the key activities of nodes in a WSN is communication and the routing of their data to a centralized base-station or sink. Routing using the shortest path to the sink is not the best solution since it will cause nodes along this path to fail prematurely. We propose a cross-layer energy efficient routing protocol Optrix that utilizes a convex formulation to maximize the lifetime of the network as a whole. We further propose, Optrix-BW, a novel convex formulation with bandwidth constraint that allows the channel conditions to be accounted for in routing. By considering this key channel parameter we demonstrate that Optrix-BW is capable of congestion control. Optrix is implemented in TinyOS, and we demonstrate that a relatively large topology of 40 nodes can converge to within 91 % of the optimal routing solution. We describe the pitfalls and issues related with utilizing a continuous form technique such as convex optimization with discrete packet based communication systems as found in WSNs. We propose a routing controller mechanism that allows for this transformation. We compare Optrix against the Collection Tree Protocol (CTP) and we found that Optrix performs better in terms of convergence to an optimal routing solution, for load balancing and network lifetime maximization than CTP.

Estrogenic compounds may enter the environment when biosolids are applied to land. In the present study, soil samples were collected over 4 mo from a field trial following addition of biosolids. The recombinant yeast estrogen screen bioassay identified estrogenic activity in the soil at all sampling times to concentrations up to 2.3 µg 17β-estradiol equivalency/kg. The present results indicate the potential for estrogenic compounds to persist in soil following biosolids application.

The fate of simazine and diuron during natural treatment processes occurring in aquifers during managed aquifer recharge (MAR) was evaluated by batch tests in conditions relevant to MAR using urban storm water. The tests were performed with aquifer sediment and wetland treated storm water under aerobic and anoxic geochemical conditions, with and without a carbon source amendment to assess the degradation of these herbicides. The aerobic conditions were suited for the relatively rapid degradation of the positive control 17β‐estradiol with a half‐life of 3.8–4.5 days and a much slower decay of simazine (30–32 days) and diuron (35–41 days). The study also showed that significant attenuation of simazine can be achieved through biodegradation under nitrate reducing conditions in aquifer sediments, with a similar half‐life (26–30 days) to the aerobic condition. The biodegradation half‐life of diuron under nitrate reducing conditions was long (91 days), but carbon supplement (20 mg C/L) halved it to 41 days. Significant attenuation of simazine and diuron in aquifers may be achievable, if sufficient residence time (e.g. at least a year) is allowed in the subsurface in aquifer storage, transport and recovery schemes.

A batch test approach was used to assess the in situ attenuation by natural reservoir systems of selected disinfection by‐products (DBPs). The aim was to determine which natural attenuation processes (volatilisation, photolysis and biodegradation) dominated for selected trihalomethanes (THMs) and N‐nitrosodimethylamine (NDMA), common DBPs present in reclaimed water which could be used to potentially augment drinking water supplies. Attenuation rates for THMs were found to be all very similar, with half‐lives ranging from 1.5–1.6 days for open batch tests. The dominant attenuation mechanisms for THMs were volatilisation with hydrolysis and biodegradation of potentially minor importance. NDMA had a half‐life of 3.5–4.3 days for vials exposed to light. The most important attenuation mechanism for NDMA was photolysis with volatilisation and biodegradation of minor importance. The results indicate that the selected DBPs could be effectively attenuated by a natural reservoir system such as a surface water reservoir.

Laboratory biodegradation batch studies were performed to investigate the degradation behavior of six selected UV filters, namely benzophenone-3 (BP-3), 3-(4-methylbenzylidene) camphor (4-MBC), Octyl 4-methoxycinnamate (OMC), Octocrylene (OC), 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro benzotriazole (UV-326), and 2-(2'-hydroxy-5'-octylphenyl)-benzotriazole (UV-329) in an aquifer microcosm (groundwater and aquifer sediment mixture) under aerobic and anaerobic (nitrate, sulfate, and Fe(III) reducing) conditions within 77d. The results from the biodegradation experiments showed that the six UV filters were degraded well in the aquifer materials under different redox conditions. Rapid biodegradation was observed for BP-3 and OMC in the aquifer materials, with their half-lives of 1.5-8.8d and 1.3-5.2d, respectively. In most cases, aerobic conditions were more favorable for the degradation of the UV filters in aquifer materials. Relatively slow degradation of 4-MBC, UV-326, and UV-329 under anaerobic conditions was noted with their half-lives ranging between 47d and 126d, indicating potential persistence in anaerobic aquifers. The results showed that redox conditions could have significant effects on biodegradation of the UV filters in aquifers.

The anti-microbial agent triclosan (TCS), and its derivative methyl-triclosan (Me-TCS), are discharged with treated effluents from wastewater treatment plants to receiving environments. We investigated the bioconcentration of TCS and Me-TCS in mussels (Mytilus galloprovincialis) exposed to TCS (100 ng L(-1)) for 30 days in seawater aquaria (19±2°C) with fresh phytoplankton as a food source. Bioconcentration increased with time reaching a steady-state around 24-30 days. The bioconcentration factor (log BCF) for TCS were 2.81 L kg(-1) (dry weight) and 4.13 L kg(-1), when lipid normalised concentrations were used. Mussels were also deployed in cages at four marine locations receiving effluents from WWTPs. The mean (±SD) TCS and Me-TCS concentrations for mussels from these sites were 9.87 (±1.34) and 6.99 (±2.44) μg kg(-1). The study showed that mussels can be a useful tool for monitoring pollution of TCS and Me-TCS in marine and estuarine environments.

Environmental context Benzotriazoles are chemicals widely used to inhibit corrosion in various industrial processes and in household products. They persist in aquatic environments, even under UV irradiation, and thus there is a need to improve their photolytic degradation to minimise the environmental exposure risks. We investigated the effects of four iron–carboxylate complexes on the UV photodegradation of three benzotriazoles in aqueous solutions and show that they significantly increase the degradation rates of benzotriazoles. Abstract The effects of FeIII–carboxylate complexes on the photodegradation of three benzotriazoles (BTs), i.e. benzotriazole (BT), 5-methylbenzotriazole (5-TTri) and 5-chlorobenzotriazole (CBT) in aqueous solutions were investigated under exposure to UV irradiation at 254nm in the presence of FeIII and four carboxylate ions (oxalate, tartrate, succinate and citrate). The results showed that the presence of FeIII–carboxylate complexes significantly enhanced the photodegradation rates of all three selected BTs. The photodegradation of BT, 5-TTri and CBT followed first-order reaction kinetics with half-lives ranging from 0.57 to 3.98h for BT, 6.08 to 8.25h for 5-TTri and 2.63 to 5.50h for CBT in the four systems of the FeIII–carboxylate complexes. In comparison, the half-lives ranged between 3.40 and 4.81h for BT, 6.42 and 11.55h for 5-TTri and 4.13 and 6.79h for CBT in pure aqueous solution and in the presence of FeIII or carboxylate. The degradation rates of these BTs were dependent on the pH values, type of carboxylate and FeIII/carboxylate ratios. Both BT and CBT showed the highest photodegradation rates with the shortest respective half-lives of 0.57 and 2.63h at the initial FeIII/oxalate ratio of 10/200µmolL–1 in aqueous solutions at pH 3, whereas 5-TTri had the highest photodegradation rate with the shortest half life of 6.08h at the initial FeIII/succinate ratio of 10/10µmolL–1.

This study compared the degradation of indigenous bisphenol A (BPA) and triclosan (TCS) in a biosolids-amended soil, to the degradation of spiked labelled surrogates of the same compounds (BPA-d16 and TCS-(13)C12). The aim was to determine if spiking experiments accurately predict the degradation of compounds in biosolids-amended soils using two different types of biosolids, a centrifuge dried biosolids (CDB) and a lagoon dried biosolids (LDB). The rate of degradation of the compounds was examined and the results indicated that there were considerable differences between the indigenous and spiked compounds. These differences were more marked for BPA, for which the indigenous compound was detectable throughout the study, whereas the spiked compound decreased to below the detection limit prior to the study completion. The rate of degradation for the indigenous BPA was approximately 5-times slower than that of the spiked BPA-d16. The indigenous and spiked TCS were both detectable throughout the study, however, the shape of the degradation curves varied considerably, particularly in the CDB treatment. These findings show that spiking experiments may not be suitable to predict the degradation and persistence of organic compounds following land application of biosolids.

We investigated the biodegradation of three selected benzotriazoles (BTs), namely benzotriazole (BT), 5-methyl-benzotriazole (5-TTri) and 5-chloro-benzotriazole (CBT), in aquifer materials. Biodegradation experiments were conducted in microcosms with fresh groundwater and aquifer sediment materials under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three BTs were degraded by microorganisms in aquifer materials under aerobic and anaerobic conditions. Under aerobic conditions, BT and 5-TTri were found to be degraded fastest with their half-lives of 43 days and 31 days, respectively, among the redox conditions used. Under anaerobic conditions, CBT was found to be degraded better with its half-life of 21 days under nitrate reducing conditions than under aerobic conditions with its half-life of 47 days. The two BT derivatives 5-TTri and CBT could be biotransformed into BT via demethylation and dechlorination reactions, respectively.

Environmental context Antarctica has several scientific research stations located along its coast, where they discharge often untreated sewage containing organic micropollutants. Although degradation of these pollutants by microorganisms is limited by the cold conditions, other pathways such as photodegradation may be significant. Our results indicate that, during the summer, photolysis is a potentially significant degradation pathway for organic micropollutants in Antarctic surface waters, although the rate of loss would depend on ice cover and water depth. Abstract Knowledge of the environmental fate of organic micropollutants in Antarctica is limited, especially with respect to photolysis. The Antarctic is characterised by extreme light conditions of either continuous sunshine or darkness depending on the season. The photolytic degradation of benzophenone-3 (BP-3), bisphenol A (BPA), 17α-ethinylestradiol (EE2), methyl paraben (mParaben), 4-t-octylphenol (4-t-OP) and triclosan in MilliQ and seawater was investigated over a range of irradiance levels and temperatures. Photodegradation was compound specific. Up to 20% of BPA, BP-3 and EE2 was degraded over a 7-h irradiance period. Triclosan and 4-t-OP degraded to below the limit of detection in all experiments whereas mParaben was not degraded. The degradation of triclosan increased with irradiance in both MilliQ (P=2.2×10–16) and seawater (P=2.2×10–16). The degradation of 4-t-OP increased with irradiance in MilliQ (P=8.5×10–9) and seawater (P=1.1×10–5), and with temperature in MilliQ (P=8.5×10–9) and seawater (P=1.0×10–5). Similar relationships could not be established for BPA, BP-3, EE2 and mParaben due to the limited extent of degradation observed. The photolysis of triclosan was enhanced 4-fold in seawater compared to MilliQ water. Results from this study indicate that micropollutants may persist for extended periods of time in Antarctic coastal waters, particularly with ice cover, above and beyond that exhibited in temperate seawater.