Temporal analysis of indoor bioaerosols by epifluorescence microscopy: the implications of biochar during monitoring

Abstract

"The air pollution represents a threat to society. Bad air quality can lead to consequences to ecosystems and human health. Since humans spent more than 90% of the time at indoor spaces it is necessary to warrant good indoor air quality. Bioaerosols, a predominant indoor pollutant, are biological particulate matter like fungi, bacteria, and viruses. These agents cause several diseases like influenza, allergies, and aspergillosis. Its proper control and inactivation are mandatory to ensure better human health. Residual biomasses (RB) are sources of air pollution when these are improperly managed. Thermochemical transformations are a reliable alternative to obtain value-added products from RB like biochar; a solid rich in carbon structures and great potential to apply in different fields like the control of outdoor and indoor air quality. Also, there is a possibility to improve this material via functionalization as this is a cost-effective option to generate a material useful as a tool to improve air quality. The aim of the present work is to study new alternatives to obtain functional biochar to be used to remove bioaerosols. To archive this, the biochar was functionalized with inorganic acids and the surface characteristics were explored. The acid treatment made the surface more negative, increasing the acid groups. The concentration of acids was found to be determinant in the final characteristics of the treated biochar. With this, it was determined that functionalized biochar has the potential for its use in the monitoring of bioaerosols and filtration of air polluted with this type of contaminant. This biochar was later used in bioaerosols monitoring in a pediatric care center for three months, using liquid impingement as a sampling method and epifluorescence microscopy as an analytical method to count bioparticles. The results show that bioaerosols concentration follows seasonal patterns with coincidences with epidemical data reported by health authorities. Temperature, relative humidity, and human density had an important role in indoor bioaerosol dynamics. The biochar was found to be a good media to retain spores, mold, and bacteria, improving the number of bioparticles retained in comparison with traditional buffer. The viruses were inactivated when entering in contact with biochar."