Determining the size distribution and composition of particles suspended in water can be challenging in heterogeneous multicomponent samples. Light scattering techniques can measure the distribution of particle sizes, but provide no basis for distinguishing different types of particles. Direct imaging techniques can categorize particles by shape, but offer few insights into their composition. Holographic characterization meets this need by directly measuring the size, refractive index, and three-dimensional position of individual particles in a suspension. The ability to measure an individual colloidal particle's refractive index is a unique capability of holographic characterization. Holographic characterization is fast enough, moreover, to build up population distribution data in real time, and to track time variations in the concentrations of different dispersed populations of particles. We demonstrate these capabilities using a model system consisting of polystyrene microbeads co-dispersed with bacteria in an oil-in-water emulsion. We also demonstrate how the holographic fingerprint of different contaminants can contribute to identifying their source.

Electrospun-based activated carbon nanofiber nonwovens (ACNFN) are interesting candidate materials for adsorption processes due to their high surface area and low flow-through resistance. However, the mechanical properties of these materials must be sufficient to withstand the conditions for use and to prevent breakage and fiber shedding. Improvements in the mechanical properties of the ACNFNs should not be accompanied by deterioration of other beneficial properties, however. In this research, improving the mechanical properties of ACNFN based on 14 wt % PAN/DMF was done by tuning the fabrication conditions. Carbonization occured at 600 °C for 2 h followed by steam activation at 750 °C for 1 h. We demonstrated the capability to generate ACNFN with high accessible surface area that reached 520 m 2 /g and acceptable mechanical strength (break strength, 0.9; 75 MPa, Young's modulus) for improved handling and use in different applications.

Introduction COVID-19 is a pandemic that affected humans’ lives and activities through the year 2020 in a way that was not witnessed in recent years. Many governments declared a complete lockdown as a try to stop the transmission of the disease. This lockdown resulted in a good recovery in environmental health, where air pollutants levels dramatically decreased. Theory There are two relations between air pollution and COVID-19, one is before the disease spread, and the other is after. Before the disease spread, many areas had high levels of contaminants in the air due to industrial activities, transportation, and human density. These areas had the highest infection rates and death cases. This could be attributed to two reasons, the aerosol could help to spread the virus at a higher rate, and air pollutants could negatively affect peoples’ lungs, which assisted the virus in attacking the patients brutally. Results After the disease spread, the lockdown that was applied in the major industrial countries led to a decrease in the pollutants levels and an increase in the ozone level in the air. This lockdown improved the air quality worldwide to a level that all political conferences and agreements could not reach. In this review, we are showing the impact of COVID-19 on air pollutants in different countries. Summary This paper provides information about pollutants' influence on human and environmental health that other researchers obtained in different areas of the globe before and after the pandemic. This could give ideas about the impact of humans on the environment and the possible ways of recovering the environment's health.