How natural and anthropogenic factors should drive microplastic behavior and fate: The scenario of Brazilian urban freshwater.

Brazil maintains its position at the top of the global ranking of plastic producers, yet recycling efforts have been incipient. Recent data reveals an annual production of approximately 14 million tons of plastic waste, not accounting for the surge in the usage of plastic masks and related materials due to the COVID-19 pandemic. However, what remains largely unreported is that over half of post-consumer plastic packaging in Brazil is managed without any monitoring, and it remains unclear how this will contribute to the occurrence of plastic waste and microplastics in Brazilian freshwaters. This scenario requires the consideration of several other crucial factors. Studies have been carried out mainly in marine and estuarine waters, while data on freshwaters are lacking. Brazil has continental dimensions and the highest water availability on the planet, yet the demand for water is greatest in regions with medium to low supply. Many densely populated Brazilian urban areas face chronic flood problems, possess inadequate levels of wastewater treatment, and display inadequate solid waste management practices. Consequently, urban freshwater with tropical characteristics in Brazil presents an intriguing scenario and is complementary to the most commonly studied marine environments. In this study, we explore the nuances of pollution in Brazilian urban freshwater and discuss how various parameters, such as organic matter, suspended solids, temperature, and pH, among others, influence the behavior of microplastics and their interactions with organic and inorganic contaminants. Furthermore, we address how microplastic conditions, such as biofouling, the type of plastic, or degradation level, may impact their behavior. By analyzing how these conditions change, we propose priority themes for investigating the occurrence of microplastics in Brazilian urban freshwater systems under different degrees of human impact. Ultimately, this study aims to establish a network dedicated to standardized monitoring of microplastic pollution in Brazilian urban freshwaters.

Characterization and photocatalytic performance of cement mortars with incorporation of TiO2 and mineral admixtures.

As the main components of the building envelope, construction materials have a straight relation with air contaminants from anthropogenic origins. Titanium dioxide has been recently applied in construction industry products since its photocatalytic properties can be used for pollutant degradation purposes. This study evaluated the performance of cement-based mortars with the incorporation of TiO2 nanoparticles and mineral admixtures. Six mortar compositions were defined by considering two reference mixes (with and without TiO2 incorporation), two mineral admixtures (bentonite and metakaolin) as partial cement replacement and one waste from ornamental stone processing in two levels of partial substitution of natural sand. Consistency index, density, and entrained air content of mixtures were investigated at fresh state. Compressive strength, water absorption, sorptivity, and micrographs from scanning electron microscopy were used to characterize mortars at hardened state. It was observed that incorporation of TiO2 does not considerably change mortar's properties at fresh and hardened state, despite a denser microstructure and improved interfacial transition zone. In general, the relation between the water-to-cement ratio and porosity on the performances of TiO2-added mortars was shown, which is strongly related to their photocatalytic efficiency. Metakaolin mixtures were more efficient to NO conversion, and high selectivity was observed for the bentonite mortars.

Analytical validation using a gas mixing system for the determination of gaseous formaldehyde.

Formaldehyde levels in the atmosphere are a concern in the indoor and outdoor air and many methods for determining this compound have been developed. The use of 2,4-dinitrophenylhydrazine (DNPH) for reaction with formaldehyde, catalyzed by acid, forming a hydrazone derivative in cartridges is considered the standard method for analyzing formaldehyde compounds in the air. However, formaldehyde is quantified using an analytical curve, created by diluting liquid standards of the formaldehyde-DNPH product. The analysis aims to quantify the gas phase formaldehyde, and it may be subject to experimental biases from the differences in the matrix of the sample (gas) and calibration standard (liquid). The objective of this work was to build an analytical curve in the gaseous phase using a synthetic air/formaldehyde mixing system (SFMS) and sampling with SPE-DNPH-tubes, comparing with the analytical curve in the liquid phase adopted by the Environmental Protection Agency (EPA). Parameters of linearity, sensitivity, limit of detection (LOD), limit of quantification (LOQ), precision and accuracy (recovery) were determined from the analytical curve in the gaseous phase. The best recovery in DNPH-tubes was obtained using the range of 400-1600 mL min-1 of flow rates in the gaseous phase. The sampling and reaction/elution of formaldehyde using DNPH-tubes presented adequate linearity and a similar sensitivity in the liquid analytical curve. Considering the LOD and LOQ in the gaseous phase, the values in nanograms are higher than those in the liquid phase. This study suggests that the quantification of formaldehyde in ambient air may be subject to bias due to differences in derivatization reaction efficiency. However, the results prove the efficiency of formaldehyde recovery from the atmosphere and the validity of the use of this DNPH-tube method.

An integrated assessment of water quality in a land reform settlement in northern Rio de Janeiro state, Brazil.

The Zumbi dos Palmares land reform settlement lacks modern facilities for water and sewage treatment. Local farmers often use shallow wells as alternative source of water supply, because the water table is reasonably high in the region. This work presents a multivariate analysis assessment of physicochemical and bacteriological parameters and pesticide residues in water samples collected from these shallow wells. The physicochemical parameters analyzed were: conductivity, pH, DOC (dissolved organic carbon), nitrate, turbidity, and bacteriological analysis measuring total and fecal coliforms. The results show non-compliance with Brazilian legal standards in most samples where low pH values were found, characterizing the presence of acidic waters. Another example of non-compliance is the presence of total and fecal coliforms in for drinking water in most of the samples and, in some cases, very high values (2,400 CFU). Some wells showed high conductivity values, probably associated with a history of oceanic intrusion. Analyses determining the contamination by pesticides show the presence of ametrine, atrazine, methyl parathion, carbaryl and hexazinone. The concentration for these compounds ranged from 0.14 to 1.17 µg/L. Ordinance No 2914/2011 from the Brazilian Ministry of Health establishes the acceptable limits for atrazine and methyl parathion as 9 µg L-1 and 2 µg L-1. None of these exceeded the allowable Brazilian and European limits. However, for the other two pesticides, the European Legislation (Council Directive) recommends the maximum allowable concentration of 0.1 µg L-1 and, 0.5 µg L-1 for total pesticides. Our samples that were above the quantifiable limit of 50 ng L-1, were also above the European limit values. Our results therefore suggest that water gathered from shallow wells at the Zumbi dos Palmares settlement is not proper for consumption without proper disinfection treatments.

Photochemical nitro-nitrite rearrangement in methyl parathion decay under tropical conditions.

This work presents a study of the abiotic degradation of commercially available methyl parathion in aqueous solution at two different concentrations (88 mg/L and 200 µg/L). The effects of solar irradiation and the presence of humic acids were evaluated and revealed a synergistic response between them. The half-life of methyl parathion ranged from 4.9 to 37 days, and the experimental data also show that photochemical processes were the most relevant in this case. The only byproduct found in samples submitted to shadowed conditions was 4-nitrophenol. On the other hand, 4-nitrophenol, methyl paraoxon and a new degradation product (O,O-dimethyl O-p-hydroxyphenyl phosphorothioate) were detected when the samples were exposed directly to sunlight. This newly identified compound was prepared in the laboratory by thiophosphorylation of hydroquinone, and coelution experiments with authentic samples provided unambiguous confirmation of the presence of O,O-dimethyl O-p-hydroxy phenylphosphorothioate in samples.