Verónica Nogueira

Impact of organic and inorganic nanomaterials in the soil microbial community structure

In this study the effect of organic and inorganic nanomaterials (NMs) on the structural diversity of the soil microbial community was investigated by Denaturing Gradient Gel Electrophoresis, after amplification with universal primers for the bacterial region V6-V8 of 16S rDNA. The polymers of carboxylmethyl-cellulose (CMC), of hydrophobically modified CMC (HM-CMC), and hydrophobically modified polyethylglycol (HM-PEG); the vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide (SDS/DDAB) and of monoolein/sodium oleate (Mo/NaO); titanium oxide (TiO(2)), titanium silicon oxide (TiSiO(4)), CdSe/ZnS quantum dots, gold nanorods, and Fe/Co magnetic fluid were the NMs tested. Soil samples were incubated, for a period of 30 days, after being spiked with NM suspensions previously characterized by Dynamic Light Scattering (DLS) or by an ultrahigh-resolution scanning electron microscope (SEM). The analysis of similarities (ANOSIM) of DGGE profiles showed that gold nanorods, TiO(2), CMC, HM-CMC, HM-PEG, and SDS/DDAB have significantly affected the structural diversity of the soil bacterial community.

Biological treatment with fungi of olive mill wastewater pre-treated by photocatalytic oxidation with nanomaterials

Olive mill wastewater (OMW) still is a major environmental problem due to its high chemical oxygen demand (COD) and total phenolic content (TPC), contributing for the high toxicity and recalcitrant nature. Several attempts have been made for developing more efficient treatment processes, but no chemical or biological approaches were found to be totally effective, especially in terms of toxicity reduction. In this context, the main purpose of this study was to investigate the treatability of OMW by the combination of photocatalytic oxidation, using two nanomaterials as catalysts (TiO2 and Fe2O3), with biological degradation by fungi (Pleurotus sajor caju and Phanerochaete chrysosporium). Photocatalytic oxidation was carried out using different systems, nano-TiO2/UV, nano-Fe2O3/UV, nano-TiO2/H2O2/UV and nano-Fe2O3/H2O2/UV. The effectiveness of the treatment was assessed through color (465nm), aromatics (270nm), COD and TPC reductions, as well as by the decrease in toxicity using the bacterium Vibrio fischeri. The chemical treatment with the system nano-TiO2/H2O2/UV promoted 43%, 14%, 38% and 31% reductions in color, aromatics content, COD and TPC, respectively. However no toxicity reduction was observed. The combination with a biological treatment increased the reduction of COD and TPC as well as a reduction in toxicity. The treatment with P. chrysosporium promoted the highest reduction in toxicity, but P. sajor caju was responsible for the best reduction in COD and TPC. However, the biological treatment was more effective when no hydrogen peroxide was used in the pre-treatment.

Toxicity of solid residues resulting from wastewater treatment with nanomaterials.

Nanomaterials (NMs) are widely recommended for wastewater treatments due to their unique properties. Several studies report the different advantages of nanotechnology in the remediation of wastewaters, but limited research has been directed toward the fate and potential impacts of the solid residues (SRs) produced after the application of such technologies. The present work aimed at investigating the ecotoxicity of SRs resulting from the treatment of three effluents (OOMW, kraft pulp mill, and mining drainage) with two NMs (TiO2 and Fe2O3). The invertebrate Chironomus riparius was selected as test organism and exposed to the residues. The effect on percentage of survival and growth was assessed. Results showed that the SRs from the treatments nano-TiO2(1.0gL(-1))/H2O2(0.5M) and nano-Fe2O3(1.0gL(-1))/H2O2(1.0M) from OOMW and nano-Fe2O3(0.75gL(-1))/H2O2(0.01M) from kraft pulp mill effluent exhibited lethal toxicity to C. riparius. Only the exposure to SRs resulting from the treatment with nano-Fe2O3(0.75gL(-1))/H2O2(0.01M) applied to the kraft pulp mill effluent significantly affected the growth rate based on the head capsule width. In terms of growth rate, based on the body length, it decreased significantly after exposure to the SRs from the treatments nano-TiO2 (1.0gL(-1)) and nano-Fe2O3(0.75gL(-1))/H2O2(0.01M) of kraft paper mill effluent and nano-Fe2O3(1.0gL(-1))/H2O2(1.0M) of OOMW. According to our study the SRs can promote negative effects on C. riparius. However, the effects are dependent on the type of effluent treated as well as on the organic and inorganic compounds attached to the NMs.

Photocatalytic Treatment of Olive Oil Mill Wastewater Using TiO2 and Fe2O3 Nanomaterials

The olive oil industry produces a highly complex wastewater, known as olive oil mill wastewater (OOMW), which represents a relevant environmental problem for the Mediterranean region. Several physicochemical, biological and combined treatments have been tested to deal with this industrial externality but none was totally effective in reducing its toxicity for species inhabiting the receiving freshwater systems. Within this framework, nanotechnology appears as a promising research area, offering new approaches for the treatment of wastewaters based on the enhanced physical and chemical properties of nanomaterials (NMs). In this context, this work aimed to investigate the treatability of OOMW through several treatments involving advanced oxidation processes plus the use of two nanomaterials as catalysts (UV/H2O2, UV/TiO2, UV/Fe2O3, UV/TiO2/H2O2 and UV/Fe2O3/H2O2). The concentrations of the catalyst and of the oxidant agent were also investigated. The results obtained showed that photodegradation treatments combining TiO2 or Fe2O3 NMs with H2O2 were the most efficient. Regarding the OOMW toxicity to Vibrio fischeri, it was significantly reduced with the following treatments: UV/TiO2/H2O2 and UV/Fe2O3/H2O2. However, the highest reduction recorded for this parameter was obtained in the treatment with UV/H2O2. The use of NMs combined with H2O2 showed a great potential for removing phenols from OOMW, which have been pointed out as the major toxic compounds of this wastewater.

Treatment of real industrial wastewaters through nano-TiO2 and nano-Fe2O3 photocatalysis: case study of mining and kraft pulp mill effluents

ABSTRACT High quantities of industrial wastewaters containing a wide range of organic and inorganic pollutants are being directly discharged into the environment, sometimes without proper treatment. Nanotechnology has a tremendous potential improving the existing treatments or even develop new treatment solutions. In this study, nano-TiO2 or nano-Fe2O3 was used for the photocatalytic treatment of kraft pulp mill effluent and mining effluent. The experiments with the organic effluent lead to reduction percentages of 93.3%, 68.4% and 89.8%, for colour, aromatic compounds and chemical oxygen demand, respectively, when treated with nano-TiO2/H2O2/UV and nano-Fe2O3/H2O2/UV, at pH 3.0. Significant removal of metals from the mining effluent was recorded but only for Zn, Al and Cd, the highest removal attained with 1.0 g L−1 of nano-TiO2/UV and nano-Fe2O3/UV. Regarding the toxicity of the organic effluent to Vibrio fischeri, it was reduced with the treatments combining the oxidant and the catalyst. However, for the inorganic effluent, the best reduction was achieved using 1.0 g L−1 of catalyst. In fact, the increase in dose of the catalyst, especially for nano-TiO2, enhanced toxicity reduction. Our results have shown that the use of these NMs seemed to be more effective in the organic effluent than in metal-rich effluent.

TiO2 nanoparticles for the remediation of eutrophic shallow freshwater systems: Efficiency and impacts on aquatic biota under a microcosm experiment.

The application of nanomaterials (NMs) in the remediation of eutrophic waters, particularly in the control of internal loading of nutrients, has been started, but limited investigations evaluated the effectiveness of these new treatment approaches and of their potential impacts on species from shallow freshwater lakes. The present work investigated, under a microcosm experiment, the application of a TiO2 nanomaterial both for reducing nutrient (mainly phosphorus and nitrogen forms) desorption and release from sediments (preventive treatment-PT) and for eliminating algal blooms (remediation treatment-RT). Furthermore, we also intended to assess the potential impacts of nano-TiO2 application on key freshwater species. The results showed the effectiveness of nano-TiO2 in controlling the release of phosphates from surface sediment and the subsequent reduction of total phosphorus in the water column. A reduction in total nitrogen was also observed. Such changes in nutrient dynamics contributed to a progressive inhibition of development of algae after the application of the NM in PT microcosms. Concerning the ability of nano-TiO2 to interact with algal cells, this interaction has likely occurred, mainly in RT, enhancing the formation of aggregates and their rapid settlement, thus reducing the algal bloom. Both treatments caused deleterious effects on freshwater species. In PT, Daphnia magna and Lemna minor showed a significant inhibition of several endpoints. Conversely, no inhibitory effect on the growth of Chironomus riparius was recorded. In opposite, C. riparius was the most affected species in RT microcosms. Such difference was probably caused by the formation of larger TiO2-algae aggregates in RT, under a high algal density, that rapidly settled in the sediment, becoming less available for pelagic species. In summary, despite the effectiveness of both treatments in controlling internal nutrient loading and in the mitigating algal bloom episodes, their negative effects on biota have to be seriously taken into account.

Oxidative stress and genotoxicity of an organic and an inorganic nanomaterial to Eisenia andrei: SDS/DDAB nano-vesicles and titanium silicon oxide

In the past few years the number of studies on the toxic effects of nanomaterials (NMs) in the environment increased significantly. Nonetheless, the data is still scarce, since there is a large number of NMs and new ones are being developed each day. Soils are extremely important for life, and are easily exposed to the released NMs, thus enhanced efforts are needed to study the impacts on soil biota. The objective of the present work was to determine if different concentrations of two NMs, one inorganic (TiSiO4) and other organic (nano-vesicles of sodium sodecyl sulfate/ didodecyl dimethylammonium bromide - SDS/DDAB), are genotoxic to soil invertebrates. Additionally, it was intended to understand whether, in the event of occurring, genotoxicity was caused by the incapability of the cells to deal with the oxidative stress caused by these NMs. With that purpose, Eisenia andrei were exposed for 30 days to the artificial OECD soil contaminated with different concentrations of the NMs being tested. After the exposure, coelomocytes were extracted from earthworms and DNA damage was measured by the comet assay. The activity of antioxidant enzymes (e.g. glutathione peroxidase, glutathione reductase and glutathione-S-Transferase) and lipid peroxidation were also assessed. The results showed that both NMs were genotoxic, particularly TiSiO4 for which significant DNA damages were recorded for concentrations above 444mg of TiSiO4-NM/kg of soildw. Since no statistically significant differences were found in the tested antioxidant enzymes and in lipid peroxidation, the mechanism of genotoxicity of these NMs seemed to be unrelated with oxidative stress.

The last frontier : Coupling technological developments with scientific challenges to improve hazard assessment of deep-sea mining

The growing economic interest in the exploitation of mineral resources on deep-ocean beds, including those in the vicinity of sensitive-rich habitats such as hydrothermal vents, raise a mounting concern about the damage that such actions might originate to these poorly-know ecosystems, which represent millions of years of evolution and adaptations to extreme environmental conditions. It has been suggested that mining may cause a major impact on vent ecosystems and other deep-sea areas. Yet, the scale and the nature of such impacts are unknown at present. Hence, building upon currently available scientific information it is crucial to develop new cost-effective technologies embedded into rigorous operating frameworks. The forward-thinking provided here will assist in the development of new technologies and tools to address the major challenges associated with deep sea-mining; technologies for in situ and ex situ observation and data acquisition, biogeochemical processes, hazard assessment of deep-sea mining to marine organisms and development of modeling tools in support of risk assessment scenarios. These technological developments are vital to validate a responsible and sustainable exploitation of the deep-sea mineral resources, based on the precautionary principle.

Treatment of a textile effluent by adsorption with cork granules and titanium dioxide nanomaterial

ABSTRACT This study aimed to explore the efficiency of two adsorbents, cork granules with different granulometry and titanium dioxide nanomaterial, in the removal of chemical oxygen demand (COD), colour and toxicity from a textile effluent. The adsorption assays with cork were unsatisfactory in the removal of chemical parameters however they eliminated the acute toxicity of the raw effluent to Daphnia magna. The assay with TiO2 NM did not prove to be efficient in the removal of colour and COD even after 240 min of contact; nevertheless it also reduced the raw effluent toxicity. The best approach for complete remediation of the textile effluent has not yet been found however promising findings were achieved, which may be an asset in future adsorption assays.

Influence of the stabilizers on the toxicity of metallic nanomaterials in aquatic organisms and human cell lines

In this study, following a systematic approach, we used aquatic species (bacteria Vibrio fischeri and microalgae Raphidocelis subcapitata) and different human cell lines (Caco-2, HepG2, SV-80 and HaCaT) representing different tissues and exposure pathways, to investigate how two organic stabilizers (PVA and DMSO) used for NMs dispersion influence their physicochemical properties, the persistence of metals in suspension and the toxicity/ecotoxicity of two metallic NMs (nano-Ag and nano-Cu). Although the stabilizers are expected to contribute to improve the dispersion and stability of NMs, the results obtained clearly showed that no similar changes in toxicity and morphological properties of the nano-Ag can be expected after its stabilization with PVA. Thus, regarding human cell lines, the reduction in the average size of the PVA-nano-Ag was followed by a reduction or maintenance of its toxicity, but the opposite was observed for the aquatic species tested since an increase in the average size enhanced its toxicity. As far as nano-Cu is considered DMSO contributed for a better dispersion of this nanomaterial, however this was not translated in a similar toxicity/ecotoxicity modification. In summary, even for nano-Cu, for which few or no data exists regarding its toxicity after stabilization with organic compounds, it was confirmed with consistent data, that the toxicity of metallic NMs is a complex combination of average size, chemical composition, solubilization or persistence in suspension of the metallic forms, interaction with test medium components and sensitivity of test species and cell lines. The combination of all of these factors makes the toxicity of metallic NMs unpredictable and points for the need of an extensive evaluation of each new formulation.