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. ETR [Internet]. 2021 Jun. 16 [cited 2026 Mar. 11];1:223-9. Available from: https://archive-journals.rtu.lv/etr/article/view/4397