So far, I thought there won't be any studies on the overall scenario of waste disposals. After searching in depth, I have found studies on illegal waste dumping sites in Polish forests. Hope these will be helpful.
Jakiel et al. (2018) assessed the spatiotemporal distribution of wastes in the Ojcow National Park, Poland. Number of dumping sites and volume of different types of wastes were determined through field observation. They categorized the dumping sites into very small, small, medium and large sized. It is a very comprehensive study.
Another study by Zablocki et al. (2011) identified forests and natural depressions as the most common places for illegal waste dumping. Quantitative measurements of waste volumes can be found in this paper. Kolanowski and wisiniewki (2012) found total volume of 50 m3 garbage in the forest area of Ostrów Mazowiecka community.
Jakiel M., Bernatek-Jakiel, A., Gajda, A., Filiks, M. & Pufelska, M.(2018): Spatial and temporal distribution of illegal dumping sites in the nature protected area: the Ojców National Park, Poland, Journal of Environmental Planning and Management, DOI: 10.1080/09640568.2017.1412941
Kolanowski, B. & Wisiniewski, J. (2012). Assessment of the size and position of wild dumps in the White Forest in the municipality of Ostrow Mazowiecka classified as a
Natura 2000 [in Polish]. Infrastruktura i Ekologia Terenów Wiejskich, 2 (I), 99. Accessed from: https://agro.icm.edu.pl/agro/element/bwmeta1.element.agro-47c8e24c-3441-477d-9abc-261699a5b8b2
Zablocki, Z., Podlasinska, J. & Kruczek, I.(2011) Characteristics of illegal waste dumping sites located within area of Kobylanka community [in Polish]. Folia Pomeranae Universitatis Technologiae Stetinensis, Agricultura, Alimentaria, Piscaria et Zootechnica. Vol.283 No.17 pp.41-50 https://www.cabdirect.org/globalhealth/abstract/20123068877
Antczak, E., 2020. Regional Patterns in Dumping Sitesin Poland - Analysis in Context of the New "Sustainable" Waste Policy. Polish Journal of Environmental Studies, 29(2), pp.1037-1049. DOI: 10.15244/pjoes/108484