APPLICATION OF LOW-COST OPTICAL PM SENSOR FOR MONITORING OF PARTICULATE MATTER AIR POLLUTION IN THE URBAN ENVIRONMENT: A CASE STUDY IN ESPLANĀDE HOUSING ESTATE, DAUGAVPILS CITY. ENVIRONMENT. TECHNOLOGY. RESOURCES. Proceedings of the International Scientific and Practical Conference, [S. l.], v. 1, p. 223–229, 2021. DOI: 10.17770/etr2021vol1.6595. Disponível em: https://archive-journals.rtu.lv/etr/article/view/4397.. Acesso em: 11 mar. 2026.