Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C60 fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C60. Irradiating aqueous ¹³C-labeled C60 with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C60 to soil microcosms had little effect on net soil respiration, excess ¹³C in the respired CO2 demonstrates that photo-irradiating C60 enhanced its degradation in soil, with ∼0.78% of 60 day photo-irradiated C60 mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how abiotic and biotic transformation processes can couple to influence degradation of CNMs in the natural environment.

Ciprofloxacin (CIP) is a broad-spectrum antibiotic found within μg/L concentration range in the aquatic environment. It is a known contributor of umuC induction in hospital wastewater samples. CIP can undergo photolysis to result in many transformation products (TPs) of mostly unknown toxicity. The aims of this study were to determine the genotoxicity of the UV mixtures and to understand the possible genotoxic role of the stable TPs. As such, CIP and its UV-irradiated mixtures were investigated in a battery of genotoxicity and cytotoxicity in vitro assays. The combination index (CI) analysis of residual CIP in the irradiated mixtures was performed for the umu assay. Further, Quantitative Structure–Activity Relationships (QSARs) predicted selected genotoxicity endpoints of the identified TPs. CIP achieved primary elimination after 128 min of irradiation but was not completely mineralized. Nine photo-TPs were identified. The irradiated mixtures were neither mutagenic in the Ames test nor genotoxic in the in vitro micronucleus (MN) test. Like CIP, the irradiated mixtures were umuC inducing. The CI analysis revealed that the irradiated mixtures and the corresponding CIP concentration in the mixtures shared similar umuC potentials. QSAR predictions suggested that the TPs may be capable of inducing chromosome aberration, MN in vivo, bacterial mutation and mammalian mutation. However, the experimental testing for a few genotoxic endpoints did not show significant genotoxic activity for the TPs present as a component of the whole mixture analysis and therefore, further genotoxic endpoints may need to be investigated to fully confirm this.

An experimental and in silico quantitative structure-activity relationship (QSAR) approach was applied to assess the environmental fate and effects of the antipsychotic drug Thioridazine (THI). The sunlight-driven attenuation of THI was simulated using a Xenon arc lamp. The photodegradation reached the complete primary elimination, whereas 97% of primary elimination and 11% of mineralization was achieved after 256 min of irradiation for the initial concentrations of 500 μg L−1 and 50 mg L−1, respectively. A non-target approach for the identification and monitoring of transformation products (TPs) was adopted. The structure of the TPs was further elucidated using liquid chromatography–high resolution mass spectrometry (LC–HRMS). The proposed photodegradation pathway included sulfoxidation, hydroxylation, dehydroxylation, and S- and N-dealkylation, taking into account direct and indirect photolysis through a self-sensitizing process in the higher concentration studied. The biodegradability of THI and photolytic samples of THI was tested according to OECD 301D and 301F, showing that THI and the mixture of TPs were not readily biodegradable. Furthermore, THI was shown to be highly toxic to environmental bacteria using a modified luminescent bacteria test with Vibrio fischeri. This bacteriotoxic activity of THI was significantly reduced by phototransformation and individual concentration-response analysis confirmed a lowered bacterial toxicity for the sulfoxidation products Thioridazine-2-sulfoxide and Thioridazine-5-sulfoxide. Additionally, the applied QSAR models predicted statistical and rule-based positive alerts of mutagenic activities for carbazole derivative TPs (TP 355 and TP 339) formed through sulfoxide elimination, which would require further confirmatory in vitro validation tests.

The consumption of fuel by vehicles emits nitrogen oxides (NOx) and non-methane hydrocarbons (NMHCs) into the atmosphere, which are important ozone precursors. Ozone is formed as a secondary pollutant via photochemical processes and is not emitted directly into the atmosphere. In this paper, the ozone increase resulting from the use of biodiesel and diesel fuels was investigated, and the different ozone formation trends were experimentally evaluated. Known amounts of exhaust gas from a power generator operated using biodiesel and diesel fuels were added to ambient air. The quality of the ambient air, such as the initial NMHC and NOx concentrations, and the irradiation intensity have an effect on the ozone levels. When 30 cm3 of biodiesel fuel exhaust gas (BFEG) or diesel fuel exhausted gas (DFEG) was added to 18 dm3 of ambient air, the highest ratios of ozone increase from BFEG compared with DFEG in Japan and Vietnam were 31.2 and 42.8%, respectively, and the maximum ozone increases resulting from DFEG and BFEG compared with the ambient air in Japan were 17.4 and 26.4 ppb, respectively. The ozone increase resulting from the use of BFEG was large and significant compared to that from DFEG under all experimental conditions. The ozone concentration increased as the amount of added exhaust gas increased. The ozone increase from the Jatropha-BFEG was slightly higher than that from waste cooking oil-BFEG.

The presence of pharmaceuticals in the environment has triggered concern among the general population and received considerable attention from the scientific community in recent years. However, only a few publications have focused on anticancer drugs, a class of pharmaceuticals that can exhibit cytotoxic, genotoxic, mutagenic, carcinogenic and teratogenic effects. The present study investigated the photodegradation, biodegradation, bacterial toxicity, mutagenicity and genotoxicity of cyclophosphamide (CP) and 5-fluorouracil (5-FU). The photodegradation experiments were performed at a neutral to slight pH range (7–7.8) using two different lamps (medium-pressure mercury lamp and a xenon lamp). The primary elimination of the parent compounds was monitored by means of liquid chromatography tandem mass spectrometry (LC-IT-MS/MS). NPOC (non-purgeable organic carbon) analyses were carried out in order to assess mineralization rates. The Closed Bottle Test (CBT) was used to assess ready biodegradability. A new method using Vibrio fischeri was adopted to evaluate toxicity. CP was not degraded by any lamp, whereas 5-FU was completely eliminated by irradiation with the mercury lamp but only partially by the Xe lamp. No mineralization was observed for the experiments performed with the Xe lamp, and a NPOC removal of only 18% was registered for 5-FU after 256 min using the UV lamp. Not one of the parent compounds was readily biodegradable in the CBT. Photo transformation products (PTPs) resulting from photolysis were neither better biodegradable nor less toxic than the parent compound 5-FU. In contrast, the results of the tests carried out with the UV lamp indicated that more biodegradable and non-toxic PTPs of 5-FU were generated. Three PTPs were formed during the photodegradation experiments and were identified. The results of the in silico QSAR predictions showed positive mutagenic and genotoxic alerts for 5-FU, whereas only one of the formed PTPs presented positive alerts for the genotoxicity endpoint.

The behavior of photoactive TiO2 nanoparticles in an aquatic environment under UV irradiation was investigated. When there was no UV light irradiation, the attachment of humic acid (HA) onto the TiO2 nanoparticles improved their stability due to an increase in the electrostatic and steric repulsions between the particles. However, our study demonstrated that UV light clearly influenced the aggregation of TiO2 nanoparticles. Half an hour of UV irradiation caused the particles to aggregate from 331.0 nm to 1505.0 nm at a pH of 3.0. Similarly, the particles aggregated from 533.2 nm to 1037.0 nm at a pH of 6.5 and from 319.0 nm to 930.0 nm at a pH of 9.0. The aggregation continued with increased irradiation time, except for the condition at pH 3.0, which demonstrated disaggregation. Furthermore, we determined that the photocatalytic degradation of the HA dominated the behavior of TiO2 in our study. From the results of HA removal and 3DEEM fluorescence spectra data for the solution, a change in the HA was in accordance with the size change of the TiO2. The results illustrated that the UV irradiation affected the behavior of light-active nanomaterial (such as TiO2) in an aquatic system, thus influencing their bioavailability and reactivity.

This study investigates different UV doses (mJ/cm2) and the effect of dark incubation on the survival of the algae Tetraselmis suecica, to simulate ballast water treatment and subsequent transport.Samples were UV irradiated and analyzed by flow cytometry and standard culturing methods. Doses of ≥400mJ/cm2 rendered inactivation after 1day as measured by all analytical methods, and are recommended for ballast water treatment if immediate impairment is required. Irradiation with lower UV doses (100–200mJ/cm2) gave considerable differences of inactivation between experiments and analytical methods. Nevertheless, inactivation increased with increasing doses and incubation time. We argue that UV doses ≥100mJ/cm2 and ≤200mJ/cm2 can be sufficient if the water is treated at intake and left in dark ballast tanks. The variable results demonstrate the challenge of giving unambiguous recommendations on duration of dark incubation needed for inactivation when algae are treated with low UV doses.

In the current study, we report the utilization of the biogenic potential of Benincasa hispida (ash gourd) peel extract for the synthesis of Ag embedded AgCl nanoparticles nanoparticles (Ag/AgCl NPs) without the use of any external organic solvents. The appearance of dark brown color from the pale yellow color confirmed the formation of Ag/AgCl nanoparticles which was further validated by absorbance peak using UV–visible spectroscopy. The phytochemicals (flavones) present in the B. hispida peel extract acts as a reducing/stabilizing agents. The morphology and size of the synthesized NPs were characterized by transmission electron microscope (TEM), selected area electron microscope (SAED) and high resolution transmission electron microscope (HR-TEM). FT-IR spectra of the B. hispida peel extract and after the development of nanoparticles are determined to identify the functional groups responsible for the conversion of metal ions to metal nanoparticles. The synthesized nanoparticles showed an excellent photocatalytic property in the degradation of toxic dye like malachite green oxalate under sunlight irradiation. For the first time, malachite green oxalate dye was degraded by Ag/AgCl nanoparticles under sunlight irradiation.

In this study, a novel water-insoluble zinc–Schiff base complex, Zn(II)-N-salicylaldehyde-2-hydroxyanil (abbreviated as Zn-salen), was synthesized and used as a heterogeneous photocatalyst for the activation of molecular oxygen to degrade organic pollutants in aqueous solution under visible light irradiation (λ ≥ 420 nm). The catalyst was characterized by FT-IR, UV–vis spectroscopy, NMR, and MS analysis. Zn-salen displays a selective adsorption and degradation of electropositive organics, such as rhodamine B (RhB), methylene blue (MB), and o-phenylenediamine (OPD). After using cetyl trimethyl ammonium bromide (CTAB) to change sulforhodamine B (SRB) into RhB-like electropositive molecule, the degradation of SRB increased up to 96 % after 4 h of irradiation, indicating that the selectivity arises from the charge interaction between the catalyst and substrates. Zeta potential of Zn-salen also reveals that the catalyst surface is negatively charged in neutral solution, suggesting that the catalyst is selective towards positively charged substrates due to an electrostatic force of attraction. The photocatalyst was active within a wide pH range (pH 3–11) and chemically stable and can be reused over 10 times. In addition, ¹O₂ and O₂·⁻ were involved in photocatalytic degradation but O₂·⁻ appears to be the primary reactive oxygen species.

The elimination of herbicides in aquatic environment is influenced by various biotic or abiotic factors. Thus, efficient, more applicable, and flexible methods are in demand. Photodegradation has been applied to remove three main types of herbicides, phenylurea, triazine, and chloroacetanilide, from water, based on a series of TiO₂–reduced graphene oxide nanocomposites. Experimental results showed that the three types of herbicides could be mostly removed under simulated sunlight irradiation for 5 h with the as-prepared photocatalyst. Compared with pure TiO₂ or P25, the photodegradation efficiency has been markedly increased. Thus, the present work could promote a new strategy dealing with the pollution of herbicides in aquatic ecosystems.