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In this paper, Atterberg limits and hydraulic conductivity tests are performed in sand samples mixed with different amounts of silt, zeolite and bentonite. The testing liquids consist of kerosene, two paraffin oils with different viscosities, distilled water and 1, 10 and 1,000 mol/m 3 calcium chloride solutions. Experimental results show that soils completely lost their plasticity when are in contact with light nonaqueous phase liquids, and that the liquid limit depends on the dynamic viscosity of the fluid surrounding the particles. Also, tested soils show different hydraulic conductivity with water before and after Ca 2? ions are introduced in the permeating fluid, in agreement with the change in the formation Gibbs free energy and diffuse double layer theory. Finally, the influence of viscosity ratio, specific surface of particles, soil fabric and PFI on hydraulic conductivity is discussed and related to the effective particle diameter and soil void ratio.

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Soil layers in landfill liners are usually considered non-reactive, and the biological activity in the barrier is neglected for the calculation of the liner life span. The purpose of this research is to highlight the relative importance of hydraulic conductivity, chemical retardation and biological clogging on the transport of heavy metals through landfill liners. Mass transport was computed considering semi-empirical equations to determine contaminant leakage through geomembranes' imperfections, and Darcy´s law and advection-diffusion equation were used to evaluate the transport through soil liners. Hydraulic conductivity values were modified considering its reduction due to biological effects, and different retardation factors were considered to evaluate heavy metal adsorption on soil particles. The effect of compacted soil barrier thickness in specific discharge and breakthrough time was evaluated. Obtained results showed that the use of a geomembrane results in higher breakthrough time for composite liners when the prevailing transport mechanism is advection. Results also indicated the importance of considering bioclogging on the coupled hydraulic and chemical flow that determine the breakthrough time.

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We aimed to implement a pilot intervention based on offering online COVID-19 self-test kits addressed to healthcare and education professionals in Spain during the peak of the 6th wave caused by Omicron variant. Kits were ordered online and sent by mail, participants answered an online acceptability/usability survey and uploaded the picture of results. 492 participants ordered a test, 304 uploaded the picture (61.8%). Eighteen positive cases were detected (5.9%). 92.2% were satisfied/very satisfied with the intervention; and 92.5% found performing the test easy/very easy. We demonstrated that implementing online COVID-19 self-testing in schools and healthcare settings in Spain is feasible

Methane has 21 times more greenhouse gas potential than carbon dioxide. Because of that, it is of great importance to adequately manage biogas emissions from landfills. In addition, it is environmentally convenient to use this product as an alternative energy source, since it prevents methane emissions while preventing fossil fuel consumption, minimizing carbon dioxide emissions. Performed analysis indicated that biogas capturing and energy generation implies 3 times less equivalent carbon dioxide emissions; however, a change in the Argentinean electrical market fees are required to guarantee the financial feasibility of the project.

We aimed to assess the association of household and classroom determinants with students’ school absence due to respiratory tract infections (RTI) among 253 students (4-11 years) of 20 classrooms. We collected 71 absences; RTI incidence was very high during the study period, 17.5-33.1 cases per 100 population. Having someone else at home with respiratory symptoms was the most significant epidemiological factor (OR=9.12, CI 95%=2.54-33.39), suggesting that households are crucial for the transmission of RTI to the children. A positive but not statistically significant association was observed between higher median levels of CO2 and respiratory-related absences (OR=1.2, CI 95%=0.98-1.46).