# Phosphogypsum Recycling: A Review of Environmental Issues, Current Trends, and Prospects
Storage of phosphogypsum in waste heaps poses an environmental hazard, even if the facility is operated correctly. The problem of the utilization and storage of phosphogypsum is relevant for many countries around the world. There are known cases of soil, natural water pollution, and contamination of plant products due to interaction with phosphogypsum in different countries, such as Brazil, China, Greece, Jordan, Kazakhstan, Poland, Russia, Spain, Turkey, and United States of America [12; 13; 14]. When large areas are allocated for phosphogypsum storage sites, the natural landscape is transformed, the functioning of deaphotopes is disturbed, and the aesthetic appearance of the surrounding landscape is affected. This results in phosphogypsum storages being complex sources of pollution and environment deformation; they disturb the terrain, interrupt or change the natural flow of intrasoil migration of substance, pollute the landscape with technogenic substances, change the nature of surface air flows, and affect the humidity index of the site. The dump is a source of hydrodynamic impact on the environment, causes changes in groundwater levels, and leads to negative effects in the residential area. In addition, dry phosphogypsum dumps have a potential risk of erosion because of the content of more than 70% of particles with a diameter of less than 0.14 mm in the dump surface layer [11; 15]. In the study done by [PERSON] et al. (2020), hydrogen fluoride (HF) concentrations in an urban area (Huelva, southwest Spain) were associated with a nearby large phosphogypsum deposit. The geochemical anomaly of HF was discovered with average concentrations of up to 19.1 \(\upmu\)g/m\({}^{3}\) and concentrations of up to 1.6 \(\upmu\)g/m\({}^{3}\) were found in the nearest urban area. Concentrations were associated directly with the emission of HF from the phosphogypsum accumulation site [16]. The existing modern technologies of fertilizer production do not pay enough attention to the purification of raw materials from impurity elements. Therefore, the solid waste contains fluorine, rare-earth metals, arsenic, strontium, heavy metals (cadmium, lead, vanadium, and others), and radioactive elements. Thus, uranium in the structural lattice and isomorphously replaces calcium in phosphorites, which are sedimentary rocks. Hence, the content of uranium in phosphorites depends on the geochemical conditions of their origin [17]. During dry storage (without pre-neutralization), an average of 0.1% fluorine is released into the gas phase in terms of dry matter contained in phosphogypsum. Dust rising above the dumps contains an average of up to 10 g of fluorine per 1 ton of phosphogypsum (dust distribution radius is up to 1.5 km) [17]. Fluoride compounds are highly toxic to the flora. The harmless concentration of fluorine is 0.00017-0.00023 mg/m\({}^{3}\), according to the study by [PERSON] (2014), which is much lower than the maximum permissible concentration (MPC) and amounts to 0.005 mg/m\({}^{3}\)[18]. Leaves of fruit trees get brown and fall off; fruits develop poorly under conditions of fluorine content in the atmosphere of 0.003-0.01%. A weakening of the growth of pine plantations up to 50 km away from the source of fluoride gases has been observed [19]. The impact of waste dumps on water pollution is caused by the leaching of phosphogypsum components during storage in open areas. The formation of runoff at the dry phosphogypsum dumps is associated with precipitation and with the loss of water under hydraulic forces [20]. Wastewater generated on the slopes of the dumps during precipitation contains up to 3.4 g/L P\({}_{2}\)O\({}_{5}\); this is hundreds of times higher than the natural content of phosphorus anion in the surface waters of humid zones. Approximately 10% of fluorine is washed out by precipitation [17].