Portable dehumidifiers as an original matrix for the study of inhalable nanoparticles in school.

Good air quality is documented as a significant factor of social justice. The human health hazards associated with air pollution are not distributed equally across cities; the most vulnerable people are more exposed to ambient air as they commute to work and wait for buses or trains at the stations. Aerosols play important roles in atmosphere quality and the climate; their oxidation at the nanoscale level may possibly increase the reactivity and toxicity of atmospheric particulates. Indoor school environments are characterized by high concentrations of different airborne particulate and gaseous pollutants. The documentation of nanoparticles (NPs), ultra-fine particles (UFPs), and micron-size particle species present in indoor primary schools are an important aspect in the recognition of their influence in respirational difficulties and decreased cognitive progress in children. This work utilizes the study of condensed water, sampled with portable dehumidifiers (PD), to describe NPs and UFPs in the vapor stage of enclosed zones. The acquired extracts were analyzed by advanced electron microscopy techniques. A total of 392 NPs and 251 UFPs were examined in a set of 22 samples acquired in moderately limited or inadequately ventilated indoor areas from several schools. Noting that NPs-related disorders happen at particular places of respirational structure, identification of site-specific NPs accumulation should be anticipated in direction to better verify the corresponding human health outcomes resulting from respirable NPs.

La2O3 Nanoparticles: Study of Uptake and Distribution in Pfaffia glomerata (Spreng.) Pedersen by LA-ICP-MS and µ-XRF.

The production and use of nanoparticles (NPs) in different fields increased in the last years. However, some NPs have toxicological properties, making these materials potential emerging pollutants. Therefore, it is important to investigate the uptake, transformation, translocation, and deposition of NPs in plants. In this work, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and micro X-ray fluorescence (µ-XRF) were used to investigate the uptake and translocation of La2O3 NPs to stem and leaves of Pfaffia glomerata (Spreng.) Pedersen after in vitro cultivation of plants in the presence of 400 mg L-1 of La2O3 NPs. By using LA-ICP-MS and µ-XRF, image of the spatial distribution of La in the leaves was obtained, where higher concentration of La was observed in the main veins. Differences in the signal profile of La in leaves of plants cultivated in the presence of bulk La2O3 (b-La2O3) and La2O3 NPs were observed. Sharp peaks of La indicated that NPs were transported to the stems and leaves of plants treated with La2O3 NPs. Both LA-ICP-MS and µ-XRF techniques have shown to be useful for detecting NPs in plants, but LA-ICP-MS is more sensitive than µ-XRF and allowed better detection and visualization of La distribution in the whole leaf.

An in situ pre-concentration method for fluorine determination based on successive digestions by microwave-induced combustion.

A new strategy based on successive digestions by microwave-induced combustion (MIC) in the same reaction vessel with a single absorbing solution was proposed. As a proof of concept, F was determined by ion-selective electrode (ISE) in seafood digests. Samples were pressed as pellets (up to 0.7 g) and combusted in closed quartz vessels pressurized with oxygen. Sequential digestions were each performed (up to 4 combustion cycles) in the same vessel and using the same absorbing solution. In each cycle, a new filter paper, igniter and sample pellet (0.7 g of sample) were used. Ammonium hydroxide solutions (10-100 mmol L-1) were evaluated for F absorption. Accuracy of the proposed method was evaluated using certified reference material of oyster tissue (NIST 1566a) and also by comparison of results after pyrohydrolysis method. Up to 3 digestion cycles (total mass of 2.1 g) could be used with 50 mmol L-1 NH4OH as absorbing solution. Results were in agreement with those obtained using pyrohydrolysis and also with certified reference value; the coefficient of variation after 3 cycles was below 5%, which was considered as suitable for F determination even at low concentration. The residual carbon in digests was lower than 25 mg L-1, allowing F determination by ISE virtually free of interferences due to dissolved organic matter. The limit of quantification (LOQ) for F was 1.3 µg g-1 (using 2.1 g of seafood), which is almost 4 times lower than the LOQ obtained using the reference method (pyrohydrolysis). Contrary to the reference method, this relatively low LOQ allowed the determination of F in all the seafood samples analysed. Taking into account that only 6 mL of diluted NH4OH solution (50 mmol L-1) were used and the suitable LOQ, the proposed sequential digestion MIC method can be recommended for further F determination in trace levels in seafood, even using a low-cost technique such as ISE, instead of other, more powerful techniques, such as ion chromatography.

Intensification of ultrasonic-assisted crude oil demulsification based on acoustic field distribution data.

Water removal is an essential step during crude oil production due to several problems such as increased transportation costs and high corrosion rate due to dissolved salts. Indirect low frequency ultrasonic energy (US), using baths, has been recently proposed as an effective alternative for crude oil demulsification. However, the reactor position during sonication and its influence on the demulsification efficiency for crude oil has not been evaluated. In this sense, the aim of this study was to develop an automated system based on an open source hardware for mapping the acoustic field distribution in an US bath operating at 35kHz using a hydrophone. Data acquired with this system provided information to evaluate the demulsification efficiency in the different positions of the US bath and correlate it with the acoustic intensity distribution. The automated 3D-mapping system revealed a higher acoustic intensity in the regions immediately above the transducers (ca. 0.6Wcm-2), while the other regions presented a relatively lower intensity (ca. 0.1Wcm-2). Experimental data demonstrated that reactors positioned in the most intense acoustic regions provided a much higher efficiency of demulsification in comparison with the ones positioned in the less intense acoustic field regions. Demulsification efficiency up to 93% was obtained with 15min of sonication (100% amplitude) using few amount of chemical demulsifier. Hence, this work demonstrated that the information acquired with the developed mapping system could be used for inducing a higher efficiency of demulsification only by finding the more suitable position of reactor in the US bath, which certainly will help development of appropriate reactors design when looking for such approach.