The importance of integrating morphological attributes of microplastics: a theoretical discussion to assess environmental impacts

Most scientific studies on microplastic (MP) pollution report their results as number of particles (e.g., particles/m2, particles/m3, particles/kg dw). An important limitation of this expression is to consider all MP particles as environmentally equivalent, regardless of their size, volume, mass, or specific surface area. Using a theoretical approach, we advocate that including such morphological attributes reveals significant differences in results of supposedly equivalent samples that consider only the number of particles. Our goal is to present how particle size and shape produce different results for hypothetical samples with the same number of particles. Therefore, from these examples we expect to stimulate the debate and contribute to improve accuracy and comparability of studies on MP pollution.

Oysters and mussels as equivalent sentinels of microplastics and natural particles in coastal environments

Filter-feeder organisms such as oyster and mussels are exposed to particles like microplastics (MPs). Although widely used to monitor MPs contamination, little is known about their performance as sentinels, which are biological monitors accumulating contaminants without significant adverse effects. This study comparatively evaluated the quantitative and qualitative accumulation of MPs by oysters (Crassostrea brasiliana) and mussels (Perna perna) along a gradient of contamination in a highly urbanized estuarine system of Brazil. In the most contaminated site, both species presented the worst status of nutrition and health, and also one of the highest MPs levels reported for molluscs to date (up to 44.1 particles·g^-1). Despite some inter-specific differences, oysters and mussels were suitable and showed an equivalent performance as sentinels, reflecting the gradient condition demonstrated for other contaminants in the region. The similarity in MPs accumulation was also observed for qualitative aspects (polymer composition, sizes, shapes and colors). Particles were mostly <1000 μm, fibrous, colorless and composed by cellulose and polymethyl methacrylate (PMMA). Thus, despite small variations, the usage of C. brasiliana and P. perna is recommended and provides reliable information for environmental levels of microplastics.

Spatio-temporal changes in water quality in the Guarapiranga reservoir (São Paulo, Brazil): insights from a long-term monitoring data series

The provision of drinking water in metropolises is a challenge that requires programs for continuous monitoring of water quality and processes that impact the land cover of the watershed. In this work, we investigated through multivariate statistical analysis the temporal and spatial trends of several variables, not yet explored in a data series that includes 42 years (1978-2020) of monitoring in the hydrographic basin of the Guarapiranga reservoir, in the São Paulo Metropolitan Region-SPMR (Brazil). This reservoir is the source of drinking water for 3.8 million people and plays a strategic role in the social, environmental, and economic structure at SPMR. Our results point to the continuous degradation of water quality in the reservoir, although with different causes and spatio-temporal aspects. Between the 1970s and 1980s, variables associated with erosion/silting played a more critical role. From the 1990s, the introduction of N and P intensified, and the concentration of thermotolerant coliforms increased. The loss of quality is mainly associated with the progressive advance of urban settlements without planning combined with the inefficient initiatives to control domestic sewage pollution. If there is no rapid and comprehensive intervention, there is a risk that the Guarapiranga reservoir may become unsuitable for drinking water supply and other types of use in the future. This scenario will represent a critical obstacle to regional development and the quality of life of the population.

Microplastics in sediments from Amazon rivers, Brazil

We assessed the concentrations of microplastics in sediment samples collected in seven sites from Solimões, Negro and Amazon rivers, upstream and downstream the metropolitan region of Manaus. Concentrations ranged from 417 to 8178 particles/kg of dried sediment (microplastics: 0.063-5 mm), and from 0 to 5725 particles/kg of dried sediment (microplastics: 0.063-1 mm). The highest microplastics concentrations were observed in samples from shallow water (water depth of 5-7 m) sites with lower water velocity of the Negro river surrounding Manaus, and the lowest concentration in farthest sample collected in deeper zone (water depth of 34 m) of the Amazon river around 110 km downstream Manaus. The variation of microplastics concentrations within the studied area can be related to hydraulic characteristics defining the erosive-depositional behavior of the sampling sites and their proximity to Manaus. Our results represent the first report to show the ubiquitous presence and widespread distribution of microplastics in sediments from the lower Solimões, lower Negro and upper Amazon rivers.

Pharmaceutical market, environmental public policies and water quality: the case of the São Paulo Metropolitan Region, Brazil

Water pollution has been an increasing concern for the authorities responsible for planning and executing public policies. In this qualitative research, we have discussed the most sold pharmaceuticals in the São Paulo Metropolitan Region, Brazil, and compared public policies focused on pharmaceuticals and environmental issues among countries/regions. For that, data provided by Close-Up International related to the sales of medicines in the São Paulo Metropolitan Region between April/2016 and April/2017 were collected and processed to identify and quantify the pharmaceutical products. The 300 most sold medicines in the São Paulo Metropolitan Region fall in 26 therapeutic classes, which include 159 drugs. The most sold pharmaceutical products group is nonsteroidal anti-inflammatory drugs (NSAIDs) representing approximately 44.3% of the total. The ten most sold pharmaceuticals sum up 1200 tons. Dipyrone is the first place in mass representing around 488 tons, followed by metformin with around 310 tons commercialized. Public policies focused on pharmaceuticals in the environment still need adjustments to improve reinforcement, even in developed countries. There is no international standard on how to conduct the issue, each country adopting the public policy that best matches to the local. Brazil, despite having some legislation that approaches the theme, still lacks effective public policies and stakeholder awareness. In this aspect, the need for improvement of the reverse logistics system, consumer orientation to the adequate disposal of unused/expired medicines, and the adoption of the unit-dose system as a therapeutic strategy is evident.

A comparison study of cleanup techniques for oil spill treatment using magnetic nanomaterials

Magnetic nanoparticles have been successfully used to recovery oil from oil spilled on water. Two different methods, floating and vortex, were employed to promote the interaction of four oil samples with different API (e.g., 10, 20, 28 and 45) spilled on seawater and deionized water with three magnetic materials, namely: magnetite nanoparticles (N); magnetic nanocomposites of yeast biomass provided by ethanol industry (Y); and magnetic nanocomposites of cork powder (C). The magnetic nanomaterials exposed to oil on water were taking out by a neodymium magnet, and the oil recoveries were determined by gravimetric analysis before and after lyophilization. The lyophilization was determinant to guarantee the accuracy of the experiments, and without this step, the masses of oil recovered would be overestimated due to the drag of water during the oil and magnetic material removal process. Three main factors, API, contact method and magnetic material, and two interactions (i.e., API × contact method, and contact method × magnetic material) presented a statistically significant effect on oil recovery. It was observed that oil recovery increases as API decreases, and it was possible to establish a model to predict the amount of recovered oil according to this effect. Higher oil recoveries were also obtained by magnetic nanocomposites of yeast biomass (Y), regardless of the contact method and type of water, recoveries of 23% and 100% for 45 and 10 API, respectively, employing around 20 mg of Y on 300 mg of spilled oil. These percentages correspond to 0.29 ± 0.01 kg/kg and 15.98 kg/kg of recovering oil by the magnetic procedure. The increase of mass of magnetic material improved the recovery of oils with higher APIs. The reusability of the spent materials presents potential for its application in oil spill cleaning technologies.

Effect of root age on the allocation of metals, amino acids and sugars in different cell fractions of the perennial grass Paspalum notatum (bahiagrass)

This work aimed to compare the allocation of Al, Fe, Cu, Ni, amino acids and sugars in different fractions of root cells of Paspalum notatum with 21 and 120 days old grown in quartz sand. In general younger roots showed a higher content of Al, Fe, Cu Ni, amino acids and sugars, compared to older roots. This can be due to a higher metabolic activity of younger roots and/or to structural changes that can occur with cell ageing. Al and Fe were mainly allocated to fractions with pectin, hemicellulose and cellulose, both in younger and older roots. However, older roots also showed a significant fraction of Al allocated to the intracellular fraction. It seems that older roots were less able to prevent the entry of Al in the cytoplasm. The proportion of Cu was higher in intracellular components, both in younger and older roots, as expected from an essential nutrient. Ni content was very low in older roots and in younger roots it was mainly allocated to the intracellular fraction and to the cell wall polysaccharides fraction. The amino acids were mainly allocated to the cytoplasm and polysaccharide fraction. Although younger roots showed a higher total amount of amino acids compared to older roots, the amino acids profile and allocation, mainly in the cytoplasm polysaccharides, was quite similar. Arabinose, a major component of structural glycoproteins of the primary cell wall matrix, was only detected in younger roots. Thus, it seems that root cells of P. notatum suffered changes in the composition of the cell wall components with ageing. To further understand the structural changes of root cells with ageing and its effect on metal allocation, it is important to quantify several components of the cell wall matrix, namely pectins and glycoproteins.