Lemna minor: Unlocking the Value of This Duckweed for the Food and Feed Industry.

Duckweed (Lemna minor L.) is a small floating aquatic plant that has an important economic impact in several industrial areas. With its high biomass production, reasonable protein content, and resilience to several climates, it has been attracting increasing interest for potential use in animal and human food systems. Historically consumed in southwest Asia, this duckweed is now gaining attention as a potential novel food in Europe. This manuscript explores the contributions of duckweed to various food and feed industries, including aquaculture and livestock, while also pointing out the incipient research carried out for human consumption. Most importantly, it highlights the potential of Lemna minor as a vegetable for future human consumption whether eaten whole or through extraction of its nutrients.

Ozone membrane contactor for tertiary treatment of urban wastewater: Chemical, microbial and toxicological assessment.

A membrane ozone contactor, operated under continuous mode, was applied to promote the tertiary treatment of urban wastewater (UWW), targeting the removal of contaminants of emerging concern (CECs), bacterial disinfection, and toxicity reduction. This system relies on the homogeneous radial distribution of ozone (O3) in the reaction zone by "titration" through a microfiltration borosilicate tubular membrane, while the UWW swirls around the membrane and drags the O3 microbubbles generated in the membrane shell-side. The membrane is coated with titanium dioxide (TiO2-P25) and radiation can be externally supplied via four UV lamps. The ozonation tests were carried out with secondary-treated UWW collected in different seasons (winter and summer) and spiked with a mix of 19 CECs (10 µg L-1 each). For an O3 dose of 18 g m-3, the best performance was obtained by increasing the O3 concentration (maximum [O3]G,inlet of 200 g Nm-3) and decreasing the gas flow rate (minimum QG of 0.15 Ndm3 min-1), providing the highest ozone transfer yield (88 %) and, thus higher specific ozone dose (g O3 per g dissolved organic carbon). Under these conditions, removals >80 % or concentrations below the limit of quantification were obtained for up to 13 of the 19 CECs and reductions up to 5 log units for total heterotrophs and below the limit of detection for enterobacteria and enterococci. Tests including a UVC dose of 0.10 kJ L-1 enhanced disinfection ability but had no impact on CECs oxidation. After ozonation, the abundance of antibiotic resistant bacteria was reduced but not eliminated, and microbial regrowth after 3-day storage was observed. No toxic effect was detected on zebrafish embryos using a dilution factor of 4 for the ozonized UWW and when granular activated carbon adsorption was subsequently applied the dilution factor decreased to 2.

A Portable Measurement Device Based on Phenanthroline Complex for Iron Determination in Water.

In this work, a newly developed self-contained, portable, and compact iron measurement system (IMS) based on spectroscopy absorption for determination of Fe2+ in water is presented. One of the main goals of the IMS is to operate the device in the field as opposed to instruments commonly used exclusively in the laboratory. In addition, the system has been tuned to quantify iron concentrations in accordance with the values proposed by the regulations for human consumption. The instrument uses the phenanthroline standard method for iron determination in water samples. This device is equipped with an optical sensing system consisting of a light-emitting diode paired with a photodiode to measure absorption radiation through ferroin complex medium. To assess the sensor response, four series of Fe2+ standard samples were prepared with different iron concentrations in various water matrices. Furthermore, a new solid reagent prepared in-house was investigated, which is intended as a "ready-to-use" sample pre-treatment that optimizes work in the field. The IMS showed better analytical performance compared with the state-of-the-art instrument. The sensitivity of the instrument was found to be 2.5 µg Fe2+/L for the measurement range established by the regulations. The linear response of the photodiode was determined for concentrations between 25 and 1000 µg Fe2+/L, making this device suitable for assessing iron in water bodies.

Ambient concentrations and dosimetry of inhaled size-segregated particulate matter during periods of low urban mobility in Bragança, Portugal.

The restrictive measures in place during the COVID-19 pandemic provided a timely scenario to investigate the effects of human activities on air quality, and the extent to which mobility reduction strategies can impact atmospheric pollutant levels. Real-time concentrations of PM1, PM2.5 and PM10 were measured using a mobile platform in a small city of Portugal, during morning and afternoon rush hours, in two distinct phases of the pandemic: emergency phase (cold period, lockdown) and calamity phase (warm period, less restricted). The Multiple-Path Particle Dosimetry Model (MPPD) was used to calculate the PM deposition for adults. Large spatio-temporal variabilities and pronounced changes in mean PM concentrations were observed, with lower concentrations in the calamity phase: PM1 = 2.33 ± 1.61 µg m-3; PM2.5 = 5.15 ± 2.77 µg m-3; PM10 = 23.30 ± 21.53 µg m-3 than in the emergency phase: PM1 = 16.85 ± 31.80 µg m-3; PM2.5 = 30.92 ± 31.93 µg m-3; PM10 = 111.27 ± 104.53 µg m-3. These changes are explained by a combination of meteorological factors and local emissions, mainly residential firewood burning. Regarding regional deposition, PM1 was the main contributor to deposition in the tracheobronchial (5%) and pulmonary (12%) regions, and PM10 in the head region (92%). In general, total deposition doses were higher for males than for females. This work quantitatively demonstrated that even with a 38% reduction in urban mobility during the lockdown, the use of firewood for residential heating is the main contributor to the high concentrations of PM and the respective inhaled dose.

A Portable Device for Methane Measurement Using a Low-Cost Semiconductor Sensor: Development, Calibration and Environmental Applications.

Methane is a major greenhouse gas and a precursor of tropospheric ozone, and most of its sources are linked to anthropogenic activities. The sources of methane are well known and its monitoring generally involves the use of expensive gas analyzers with high operating costs. Many studies have investigated the use of low-cost gas sensors as an alternative for measuring methane concentrations; however, it is still an area that needs further development to ensure reliable measurements. In this work a low-cost platform for measuring methane within a low concentration range was developed and used in two distinct environments to continuously assess and improve its performance. The methane sensor was the Figaro TGS2600, a metal oxide semiconductor (MOS) based on tin dioxide (SnO2). In a first stage, the monitoring platform was applied in a small ruminant barn after undergoing a multi-point calibration. In a second stage, the system was used in a wastewater treatment plant together with a multi-gas analyzer (Gasera One Pulse). The calibration of low-cost sensor was based on the relation of the readings of the two devices. Temperature and relative humidity were also measured to perform corrections to minimize the effects of these variables on the sensor signal and an active ventilation system was used to improve the performance of the sensor. The system proved to be able to measure low methane concentrations following reliable spatial and temporal patterns in both places. A very similar behavior between both measuring systems was also well noticeable at WWTP. In general, the low-cost system presented good performance under several environmental conditions, showing itself to be a good alternative, at least as a screening monitoring system.