Presence Of nano-TiO2 Research Articles

Nano-TiO2 aggravates immunotoxic effects of chronic ammonia stress in zebrafish (Danio rerio) intestine

Ammonia and nano-TiO2 are commonly found pollutants in aquatic environments around the world. NH3 has been proved to be absorbed on nano-TiO2 surface, therefore, the biosafety and environmental effects of ammonia and co-occurring nano-TiO2 in aquatic environments has increased considerably in recent years. To explore the potential interactive effects and mechanisms of ammonia and nano-TiO2 on the intestinal immune system, three-month-old female zebrafish were exposed to total ammonia nitrogen (TAN; 0, 3, 30 mg/L) with or without nano-TiO2 (1 mg/L) for 60 d. The results showed that intestinal ammonia levels increased with the increase of TAN exposure concentration in the presence of nano-TiO2. Histopathological analysis demonstrated that both TAN and nano-TiO2 caused cell vacuolation, lymphocyte infiltration and goblet cells hyperplasia in the intestine mucosa. Our study also found that the contents and gene expression levels of lysozyme (lys) and β-defensin (def-β) in the intestine of zebrafish exposed to TAN alone or combined with nano-TiO2 were significantly reduced, suggesting a decline in the intestinal innate immunity of fish. A broad upregulation of TLRs-related genes indicated that TAN and nano-TiO2 could activate TLR4/5-mediated MyD88-dependent pathway, and eventually induce intestinal inflammation. It should be noted that TAN combined with nano-TiO2 had more significant inhibitory effects on the intestinal structure and innate immune responses than TAN alone. Current data suggested that ammonia and nano-TiO2 had a synergistic inhibitory effect on intestinal mucosal immunity, and their associated health risk to aquatic animals and the water ecosystem should not be underestimated.

Nano-TiO2 modifies heavy metal bioaccumulation in Daphnia magna: A model study

Due to special properties, nano-TiO2 will interact with heavy metals and other pollutants in water, thus affecting the environmental behavior and ecotoxicity of these pollutants. However, the exact manner in which nano-TiO2 affects the bioaccumulation mechanisms of heavy metals is still unclear now. In the present study, quantitative structure bioaccumulation relationship (QSBAR) models were established to explore the relationships between physicochemical parameters of heavy metals and their accumulation in Daphnia magna in the absence and presence of nano-TiO2 at low metal exposure concentrations. The results showed that different physicochemical parameters affected the bioaccumulation of metals in Daphnia magna. The metal accumulation could be described by means of a Comprehensive Parameter composed of seven parameters, i.e., atomic number (AN), relative atomic weight (AW), atomic radius (AR), atomic ionization potential (AN/ΔIP), covalent index (X2r), second ionization energy (I2) and electrochemical potential (E0), in the absence of nano-TiO2, whereas the metal accumulation increased with the increase in Van Der Waals radius (rw) of metals in the presence of nano-TiO2. It was demonstrated that the bioaccumulation mechanism of the metals to Daphnia magna changed in the presence of nano-TiO2. Moreover, the bioaccumulation of more than 85% of the metals increased in the presence of nano-TiO2, but it increased differently for different metals. The present study provides an alternative approach to understand the mechanism of heavy metal bioaccumulation at low metal exposure concentrations and the effect of nano-TiO2 on metal bioaccumulation.

Effect of nano TiO2 & ZnO on the hydration properties of Portland cement

When water is added to cement, complex hydration reactions with the evolution of heat occur. The hydration of cement has been studied by using a number of techniques such as calorimetry, X-ray diffraction, setting time, compressive strength, thermal method, and scanning electron microscopy. In the presence of nano TiO2 and ZnO, the hydration properties of cement are changed. Results have shown that nano ZnO has retarding effect, whereas nano TiO2 has an accelerating effect to a greater extent. Attempts have been made to understand the role of nanomaterials during the hydration of cement.

Quantifying the effect of nano-TiO2 on the toxicity of lead on C. dubia using a two-compartment modeling approach

Nanoparticles (NPs) can significantly influence toxicity imposed by toxic metals. However, this impact has not been quantified. In this research, we investigated the effect of nano-TiO2 on lead (Pb) accumulation and the resultant toxicity using water flea Ceriodaphnia dubia (C. dubia) as the testing organism. We used a two-compartment modeling approach, which included a two-compartment accumulation model and a toxicodynamic model, on the basis of Pb body tissue accumulation, to quantify the impact of nano-TiO2 on Pb toxicity. The effect of algae on the combined toxicity of Pb and nano-TiO2 was also quantified. The two-compartment accumulation model could well quantify Pb accumulation kinetics in two-compartments of C. dubia, the gut and the rest of the body tissue in the presence of nano-TiO2. Modeling results suggested that the gut quickly accumulates Pb through active uptake from the mouth, but the rest of the body tissue slowly accumulates Pb from the gut. The predicted Pb distribution within C. dubia was verified by depuration modeling results from an independent depuration test. The survivorship of C. dubia as a function of Pb accumulated in the body tissue and exposure time can be well described using a toxicodynamic model. The effects of algae on Pb accumulation in different compartments of C. dubia and the toxicity in the presence of nano-TiO2 were also well described using the two-compartment modeling approach. Therefore, the novel two-compartment modeling approach provides a useful tool for assessing the effect of NPs on aquatic ecosystems where toxic metals are present.

Evaluation of TiO2/ LTA Zeolite Incorporated Composite for Mutual Removal of Organic and Inorganic Pollutants: Simulation Study for Prediction of Removal Beyond Equilibrium

In this paper, incorporation of titanium nanoparticles into LTA zeolite (Linde Type A Zeolite) was synthesized by in-situ incorporation of titanium precursors within hydrothermal synthesis of LTA zeolite from local kaolin. More than one evidence for the presence of nano TiO2 including XRD, IR, DR, and SEM techniques. Mutual removal /photodecomposition of heavy metal/organic dye including methylene blue combined with as set of Co2+, Cu2+, Ni2+and Pb2+ ions was the main aim of this study. A four dimensional simulation program were written to predict for the first time both dye and ions with the fourth dimension of time. This program for the first time , is capable of prediction of the removal beyond the equilibrium state. The program was verified and percentage of error did not exceeds 3% with high accuracy. This study will open a new sight the use the modified zeolite as an effective photocatalyst in addition to its high performance of removal of heavy metals. New definitions of some new terminologies was impeded in the literature for the first time such as; Amount selectivity, Partial capacity, Time selectivity, Normalized selectivity, Remained capacity and Loop selectivity

NanoTiO2 materials mitigate mercury uptake and effects on green alga Chlamydomonas reinhardtii in mixture exposure

The present study examined the effect of titanium dioxide nanoparticles (nanoTiO2) and mercury (Hg) compounds on the green alga, Chlamydomonas reinhardtii. Mixtures containing nanoTiO2 of different primary sizes (5 nm, 15 nm and 20 nm), inorganic Hg (IHg) or monomethyl Hg (CH3Hg+, MeHg) were studied and compared with individual treatments. Oxidative stress and membrane damage were examined. Stability of nanoTiO2 materials in terms of hydrodynamic size and surface charge as well as Hg adsorption on different nanoTiO2 materials were characterized. The uptake of Hg compounds in the absence and presence of nanoTiO2 was also quantified. Results show that increasing concentrations of nanoTiO2 with different primary size diminished oxidative stress and membrane damage induced by high concentrations of IHg or MeHg, due to the adsorption of Hg on the nanoTiO2 aggregates and consequent decrease of cellular Hg concentrations. The observed alleviation effect of nanoTiO2 materials on Hg biouptake and toxicity was more pronounced for the materials with smaller primary size. IHg adsorbed onto the nanoTiO2 materials to a higher extent than MeHg. The present study highlights that the effects of contaminants are modulated by the co-existing engineered nanomaterials; therefore, it is essential to get a better understanding of their combined effect in the environment.

Effect of Sonication and Nano TiO2 on Thermophysiological Comfort Properties of Woven Fabrics.

The main aim of the present study was to investigate the effects of ultrasonic irradiation on thermophysiological comfort properties of TiO2-coated fabrics. The results were evaluated on the basis of heat and mass transfer as well as air permeability performances. Alambeta, a permetester, an air permeability tester, and a moisture management tester were used for thermal evaluation and air and moisture transportation, respectively. Hundred percent pure cotton and polyester woven fabrics were used for this study. Moreover, the study explains the effect of sonication on surface roughness of textile woven fabrics. TiO2 nanoparticles were deposited onto selected fabrics by sonication. Surface topography, changes regarding surface roughness, and the presence of nano TiO2 were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffractometry (XRD), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Furthermore, standard test methods were carried out to evaluate physical and overall thermophysiological comfort properties, i.e., thermal conductivity, thermal absorptivity, relative water vapor permeability, absolute evaporative resistance, air permeability, and overall moisture management capacity of TiO2-treated and untreated samples.

Transcriptome Reveals the Rice Response to Elevated Free Air CO2 Concentration and TiO2 Nanoparticles.

Increasing CO2 levels are speculated to change the effects of engineered nanomaterials in soil and on plant growth. How plants will respond to a combination of elevated CO2 and nanomaterials stress has rarely been investigated, and the underlying mechanism remains largely unknown. Here, we conducted a field experiment to investigate the rice (Oryza sativa L. cv. IIyou) response to TiO2 nanoparticles (nano-TiO2, 0 and 200 mg kg-1) using a free-air CO2 enrichment system with different CO2 levels (ambient ∼370 μmol mol-1 and elevated ∼570 μmol mol-1). The results showed that elevated CO2 or nano-TiO2 alone did not significantly affect rice chlorophyll content and antioxidant enzyme activities. However, in the presence of nano-TiO2, elevated CO2 significantly enhanced the rice height, shoot biomass, and panicle biomass (by 9.4%, 12.8%, and 15.8%, respectively). Furthermore, the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that genes involved in photosynthesis were up-regulated while most genes associated with secondary metabolite biosynthesis were down-regulated in combination-treated rice. This indicated that elevated CO2 and nano-TiO2 might stimulate rice growth by adjusting resource allocation between photosynthesis and metabolism. This study provides novel insights into rice responses to increasing contamination under climate change.

Corrosion protection performance of nano-TiO2-containing phosphate coatings obtained by anodic electrochemical treatment

Abstract The efficacy of nano-TiO2-containing zinc phosphate coatings on low-carbon steel is investigated. Zinc phosphate coatings are electrodeposited on low-carbon steel (AISI 1015) keeping current density, deposition time and wt % nano-TiO2 at their respective levels. Corrosion protection performance of these coatings was assessed using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl electrolyte. The morphology, the composition and the growth process of the zinc phosphate coating is investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD) and electrochemical measurements. The XRD study reveals that the obtained phosphate layer contains traces of hopeite and phosphophylite. The formed zinc phosphate coating offers high corrosion protection in 3.5% NaCl solution, which is well supported by EIS studies. The presence of nano-TiO2 in the phosphate bath anticipated to offer a better surface coverage and reduction in porosity and forms more homogeneous coating, which is in agreement with the SEM studies. The optimization of the electrodeposition phosphating process for achieving better responses in terms of corrosion rate and coating resistance is addressed in this paper.

Influence of electrodeposition potential, TiO2 nanoparticles and chromium (III) inhibitor addition on the corrosion protection performance of organosilane coating on aluminium

ABSTRACTIn this work, the anticorrosion properties of phenyl trimethoxysilane (PTMS) films coated on aluminium 5000 series alloys were studied. PTMS films were deposited at various cathodic potentials. The optimum electrodeposition potential was found to be −0.8 V vs. SCE. The coatings were also modified by different amounts of nano-TiO2. In order to introduce corrosion inhibition and a self-repair property of the PTMS film, the addition of chromium (III) corrosion inhibitor in the presence of nano-TiO2 was studied. The anticorrosion performance of coatings was investigated in a 3.5 wt.% NaCl solution. At optimum deposition potential, the ‘critical’ nano-TiO2 and Cr(III) contents were both observed, under which the obtained PTMS coatings show the highest anticorrosion performance. The surface morphologies of PTMS coatings were examined by scanning electron microscopy. The results showed that the coatings deposited at −0.8 V vs. SCE, from 20 ppm of nano-TiO2 and 0.003 M Cr(III) inhibitor present uniform and compact morphologies.

Two-generational effects and recovery of arsenic and arsenate on Daphnia magna in the presence of nano-TiO2

The toxicity of arsenic (As) can be influenced by many environmental factors. Among them, nanomaterials can adsorb arsenic and alter its bioavailability in organisms. However, the studies on long-term effects of arsenic in the presence of nanoparticles are limited. Thus, the 21-d effect of titanium dioxide nanoparticles (nano-TiO2) on chronic toxicity of arsenic (arsenate and arsenite) was investigated in two generations of Daphnia magna. The exposed concentration of nano-TiO2 was 1 mg/L and the concentration of As(Ⅲ) or As(Ⅴ) was 0.2 mg/L which was lower than the 48 h-NOEC (no observed effect concentration). The survival, body length, average number of offspring and time of first brood were determined. Our results indicated that the exposure to nano-TiO2 and As during the parental generation can affect the health of offspring. Nano-TiO2 was found to significantly alleviate the mortality and reproduction inhibition of As on D. magna, and the alleviation of As(Ⅴ) was more prominent than that of As(Ⅲ). It is likely that nano-TiO2 alters the metabolism and adsorption condition of arsenic in the gastrointestinal tract of D. magna. Overall, these results indicate that the increase of arsenic adsorption onto nano-TiO2 in the gut of D. magna could alleviate the toxicity of arsenic. Nonetheless, further research should be conducted to study the influence of arsenic on the multi-generations of aquatic organisms, especially when it is coexisted with other substances.

Effect of metal oxide nanoparticles on the evolution of valuable gaseous products during pyrolysis of Turkish low-rank coal

In this study, TiO2 and ZnO nanoparticles were synthesized via solvothermal method and used as a catalyst for low-rank coal (LRC) pyrolysis to improve the gaseous product quality and yield. Effects of nanocatalysts on the yields of pyrolysis products distribution were discussed in details. Different reaction temperatures (400–700 °C) and catalyst to LRC ratios (1, 5, and 15% w/w) were examined. The optimum catalyst to LRC ratio was found as %1 by weight, while optimum pyrolysis temperature was determined as 700 °C. The gaseous products (hydrogen, methane, carbon dioxide, carbon monoxide and C2–C4 hydrocarbons) were characterized by micro gas chromatography (μGC) to understand the catalytic ability of TiO2 and ZnO nanoparticles while the pyrolytic oil (tar) was characterized by gas chromatography–mass spectroscopy (GC–MS) as well as Fourier-transform infrared spectroscopy (FT-IR). Through the thermogravimetric analysis method (TGA) weight loss was obtained in the samples.H-ZSM-5 as well-known pyrolysis catalysts was also used for the comparison purposes. The results showed that gaseous product yields were increased drastically in the presence of nano TiO2 and nano ZnO.

Influence of titanium dioxide nanoparticles on the toxicity of arsenate in Nannochloropsis maritima

Interest is growing in the role that nanoparticles play in modifying the biological effects of contaminants. This study aimed to determine whether nano-TiO2 exhibited pronounced influence on arsenate (As(V)) toxicity levels to the marine microalgae Nannochloropsis maritima. We compared individual and combined toxicity levels of As(V) and nano-TiO2 by assessing the inhibition percentages of algal growth. Compared to groups treated with As(V) alone, an EC50 of 53.0 mg/L decreased by 28.8% after the addition of nanoparticles. This enhanced toxicity was attributed to the inhibition of As methylation and the promotion of lipid peroxidation in the presence of nano-TiO2. Additionally, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) also showed that algal cells exhibited different degrees of shrinkage, that cell wall were destroyed in the process, and that the photosynthetic apparatus was virtually indiscernible after the addition of nano-TiO2. In addition, for low As(V) concentration exposure groups, nano-TiO2 could alleviate As(V) toxicity to some extent by reducing As sorption onto algal cells and subcellular distribution in organelles, but this alleviation effect could not protect against the combined toxicity (both As(V) and nano-TiO2) effect on N. maritima, which was verified by the higher inhibition percentage of the algal growth rate in the combined exposure group treatment compared to the As(V) exposure treatment alone. Our results suggest that more attention must be paid to the potential impact of nanoparticles on the bioavailability and biotransformation of contaminants in phytoplankton.

Environmentally benign chemical recycling of polycarbonate wastes: comparison of micro- and nano-TiO2 solid support efficiencies

Abstract Polycarbonate (PC) wastes, including optical discs (CDs) and digital optical discs (DVDs), were chemically recycled into valuable materials such as 4,4′-(propane-2,2-diyl)diphenol (BPA) and etherified derivatives of BPA using sodium hydroxide (NaOH) as the alkali metal catalyst and nanostructured titanium dioxide (nano-TiO2) and microstructured titanium dioxide (micro-TiO2) as the solid supports in the binary green system consisting of water and 2,2′-oxydi(ethan-1-ol) (DEG) under conventional heating method, and data were compared. In this study, the effects of various parameters, such as solvent composition, concentration of NaOH, and solid support, were studied on the reaction progress. In these reactions, the importance of water as the green solvent was investigated in achieving pure BPA as the valuable material. When used with 20% aqueous DEG (pbw), a pure BPA can be obtained at 70% yield in the presence of nano-TiO2 and micro-TiO2 as the solid supports. According to the results, the use of nano-TiO2 in comparison with micro-TiO2 accelerates the chemical recycling of PC wastes. The nano-TiO2 catalyst recovery shows that the recovered solid support is applicable for four cycles. The obtained products were characterized using spectroscopic methods, namely, 1H NMR, 13C NMR, and Fourier transform infrared spectroscopy as well as gas chromatography-mass spectrometry.

Effect of titanium dioxide nanoparticles on the accumulation and distribution of arsenate in Daphnia magna in the presence of an algal food.

The impact of titanium dioxide nanoparticles (nano-TiO2) on the bioavailability of metals in aquatic filter-feeding organisms has rarely been investigated, especially in the presence of algae as a food source. In this study, we quantified the accumulation and subcellular distribution of arsenate (AsV) in Daphnia magna in the presence of nano-TiO2 and a green alga (Scenedesmus obliquus) food source. Results showed that S. obliquus significantly increased the accumulation of total arsenic (As) and titanium (Ti) in D. magna. The presence of this food source increased As in metal-sensitive fractions (MSF) and as biologically detoxified metals (BDM), while it decreased Ti levels in MSF but increased levels as BDM. The difference in the subcellular distribution of As and Ti demonstrates the dissociation of As from nano-TiO2 during digestion at subcellular partitioning irrespective of food availability. In turn, the presence of algae was shown to increase metal-based toxicity in D. magna due to the transfer of As from BMD to MSF. Furthermore, S. obliquus significantly increased the concentration of As and Ti in soluble fractions, indicating that As and nano-TiO2 ingested by D. magna could be transferred more readily to their predators in the presence of S. obliquus. Our study shows the potential of algae to increase the toxicity and biomagnification of AsV. Furthermore, it highlights food as an important factor in the toxicity assessment of nanomaterials and co-existing pollutants.

Titanium dioxide nanoparticles enhance inorganic arsenic bioavailability and methylation in two freshwater algae species

The effect of titanium dioxide nanoparticles (nano-TiO2) on the bioaccumulation and biotransformation of arsenic (As) remains largely unknown. In this study, we exposed two freshwater algae (Microcystis aeruginosa and Scenedesmus obliquus) to inorganic As (arsenite and arsenate) with the aim of increasing our understanding on As bioaccumulation and methylation in the presence of nano-TiO2. Direct evidence from transmission electron microscope (TEM) images show that nano-TiO2 (anatase) entered exposed algae. Thus, nano-TiO2 as carriers boosted As accumulation and methylation in these two algae species, which varied between inorganic As speciation and algae species. Specifically, nano-TiO2 could markedly enhance arsenate (As(V)) accumulation in M. aeruginosa and arsenite (As(III)) accumulation in S. obliquus. Similarly, we found evidence of higher As methylation activity in the M. aeruginosa of As(III) 2 mg L−1 nano-TiO2 treatment. Although this was also true for the S. obliquus (As(V)) treatment, this species exhibited higher As methylation compared to M. aeruginosa, being more sensitive to As associated with nano-TiO2 compared to M. aeruginosa. Due to changes in pH levels inside these exposed algae, As dissociation from nano-TiO2 inside algal cells enhanced As methylation. Accordingly, the potential influence of nanoparticles on the bioaccumulation and biotransformation of their co-contaminants deserves more attention.

Complex role of titanium dioxide nanoparticles in the trophic transfer of arsenic from Nannochloropsis maritima to Artemia salina nauplii

Increasing concern has been focused on the potential risks associated with the trophic transfer to aquatic organisms of ambient contaminants in the presence of titanium dioxide nanoparticles (nano-TiO2). This study investigated the influence of nano-TiO2 on the trophic transfer of arsenic (As) from the microalgae Nannochloropsis maritima to the brine shrimp Artemia salina nauplii. We found that nano-TiO2 could significantly facilitate As sorption on N. maritima within an exposure period of 24 h, and this sorption subsequently led to higher As trophic transfer from the algae to A. salina according to trophic transfer factors (TTFAs+nano-TiO2 > TTFAs). However, after 48 h of depuration, the retention of As in A. salina fed As-nano-TiO2-contaminated algae was even lower than that in A. salina fed As-contaminated algae at the same exposure concentrations. This result indicates that the increased food chain transfer of As in the presence of nano-TiO2 can be explained by adsorption of As onto nano-TiO2 in contaminated food (algae), but the bioavailability of As in A. salina is reduced after the introduction of nanoparticles. Although the stress enzyme activities of superoxide dismutase (SOD) and acetylcholinesterase (AChE) in A. salina at a lower As concentration treatment in the presence of nano-TiO2 were not significantly changed, they increased with higher exposure concentrations of As with or without nano-TiO2. Our study highlighted the complex role of nanomaterials in the transfer of ambient contaminants via trophic chains and the potential of nano-TiO2 to reduce the bioavailability of As via trophic transfer to saltwater zooplankton.

Nano-TiO2 Imparts Amidoximated Wool Fibers with Good Antibacterial Activity and Adsorption Capacity for Uranium(VI) Recovery

Marine bacteria play a key role in marine ecosystems and are one of the main causes of biofouling. Biofouling of adsorbents that are used for uranium recovery usually results in a decrease in uranium recovery. A novel adsorbent with antibacterial activity for uranium recovery in bacterial environments was prepared in our study to address this concern. Amidoxime-functionalized wool fibers with nano-TiO2 particles (Wool-AO@TiO2) was synthesized by radiation-induced graft polymerization combined with in situ coprecipitation of nano-TiO2 particles onto the wool fibers. The presence of nano-TiO2 on the adsorbent was verified by scanning electron microscopy with energy-dispersive X-ray spectroscopy. The maximum uranium adsorption capacity of Wool-AO@TiO2, acquired from the Langmuir isotherm, was 113.12 mg/g. The introduced nano-TiO2 imparted excellent antibacterial activity to Wool-AO@TiO2. The inhibition of Staphylococcus aureus and Escherichia coli by Wool-AO@TiO2 was 95.2% and 90%, respectively. The adsorpti...

Methods of determining titanium dioxide nanoparticles enhance inorganic arsenic bioavailability and methylation in two freshwater algae species

We developed the effect of titanium dioxide nanoparticles (nano-TiO2) on the bioaccumulation and biotransformation of arsenic (As), which remain largely unknown. We thus exposed two freshwater algae (Microcystis aeruginosa and Scenedesmus obliquus) to inorganic As with the aim of increasing our understanding on As bioaccumulation and methylation in the presence of nano-TiO2. Direct evidence of TEM and EDX image showed that nano-TiO2 (anatase) entered the exposed algae. Thus, nano-TiO2 as carriers boosted arsenic accumulation and methylation in these two algae species, which varied with both inorganic As speciation and algae species. Specifically, nano-TiO2 could enhance markedly arsenate accumulation in M. aerugginosa and arsenite accumulation in S. obliquus. Similarly, we found higher content of As methylation in M. aeruginosa of arsenite with 2 mg L-1 of nano-TiO2 treatment and in S. obliquus of arsenate treatment. Additionally, S. obliquus exhibited higher As methylation compared to M. aeruginosa, being more sensitive to As associated with nano-TiO2 than M. aeruginosa. Due to changes in pH levels inside these exposed algae, the As dissociation from nano-TiO2 inside algal cell enhanced As methylation. Accordingly, the potential influence of nanoparticles on the bioaccumulation and biotransformation of their co-contaminants deserves more attention.•Nano-TiO2 entry is assumed to promote As accumulation into exposed algae.•Nano-TiO2 had different carrying capacities for different forms of As and algae.•As dissociation from nano-TiO2 is assumed to enhance As methylation in algae.

Molecular transformation of natural and anthropogenic dissolved organic matter under photo-irradiation in the presence of nano TiO2

Photochemical transformation of dissolved organic matter (DOM) plays a very important role in the cycling of organic carbon in aquatic systems. Increasing release of photoactive nanoparticles such as titanium dioxide nanoparticles (nano TiO2) into surface water may impact this process. The present study employed Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to examine the molecular transformation of natural DOM (peat DOM, DOMp) and anthropogenic DOM (sludge-derived DOM, DOMs) under photo-irradiation as affected by nano TiO2. Differences in molecular components between DOMp and DOMs were observed. DOMs contained more heteroatom formulas (76%) with low aromaticity and low carbon oxidation state than did DOMp (22%). The presence of nano TiO2 resulted in significant decreases in both DOM content and molecular diversity under photo-irradiation. Consistent alterations were observed between DOMp and DOMs such that high molecular weight compounds, high aromaticity and/or heteroatom S-containing compounds were more easily photodegraded in the presence of nano TiO2; whereas the average carbon oxidation state decreased in DOMp but increased in DOMs, likely due to the significant differences in O abundance, especially in the contents of carboxyl moieties, between DOMp and DOMs. The findings of the present study suggest that the release of nano TiO2 into aquatic environment will accelerate the consumption of dissolved organic carbon and the attenuation of molecular diversity for both DOM in waters.