Dust emission during operational and closure phase of Zn-Pb “Trzebionka” mine flotation tailings storage site

Mining and processing of zinc and lead ores involves the storage of flotation tailings which to a varying degrees affect the quality of the environment. The impact is due to the tailings being stored in the open open on a above-ground storage site. For quantitative evaluation of pollutants emitted from the area of such a facility, it is necessary to conduct comprehensive monitoring of the scale of pollutant emission and environmental quality monitoring around the storage site. The adverse impact of the tailings storage site on the surrounding environment is associated with several processes both at the operational as well as at the closure phase. The main threat is periodic dusting of the finest fraction of the waste. Periodic discharge of leachate to surface flows and direct infiltration into the substrate also impact the environment. It is important that monitoring is continued at the post-operational phase and that the assayed parameters are consistent with the specificity of the stored tailings. Environmental monitoring at the post-operational and closure phases is important for the surveillance of proper storage site closure and the subsequent reclaim treatment. Measurement of diffuse dust emission into the atmosphere is not mandatory, but it is an essential element of surveillance of the facility's impact on the environment. It is important to monitor the total amount of dust fall and the content of the main heavy metals present in the tailings slime (such as zinc and lead). Dust emission is connected with many anthropogenic and natural factors. This phenomenon may be enhanced in dry weather conditions and violent winds. Long-term monitoring of these pollutants allows a comparison of emissions at different periods of mining and production operations and the associated phases of the storage site operation (storage, closure, reclaim treatment, the period following reclaim). The flotation tailings storage site (pond) of "Trzebionka" SA mine (currently in liquidation), is located on the border of Trzebinia and Chrzanow communes in south-western part of the Malopolska region. The storage site opened in the late 1960s after the opening of the ore enrichment plant. From the beginning, the storage site was located above ground. Currently, it occupies an area of approximately 64 ha, has a height of about 60 m above the ground and the area at the top is about 20 ha. The facility is made mainly of fine-grained dolomitic material, which is waste material from the process of Zn-Pb ore flotation. The storage site was closed down in 2009, currently work is underway aimed at final biological reclamation of the area. Regular monitoring of dust emissions from the area of the storage site has been conducted since the early 1980s. Emission monitoring is conducted indirectly, based on continuous measurement of dust fall at selected points, located around the site. Measurements of dust fall in the area of the sedimentation pond constitute one of the elements of the implemented, comprehensive monitoring study of soil and water environment regarding water and wastewater analysis and dust fall. The study includes quantitative measurements of dust and chemical analysis of the total zinc and lead content in the accumulated sediment. The end result of the study is to estimate the total amount of dust, lead and zinc reported for individual years. The long-term monitoring has allowed to determine the effectiveness of reclaim treatments both during the operational phase and at closure. An analysis of the research results shows that the amount of dust in the region closest to the impact zone of the, tailings accumulated at the storage site was characterized by large changeability from 1982 to 2011 There has been a sharp decrease in the amount of dust fall from the over 150 Mg/km2 year in the early years of operation to about 50 Mg/km2 year in the late years. At the closure phase and at the phase of biological reclaim further reduction of dust emission from the storage site dome has been observed and it amounted to 16 Mg/km2 per year. Such changeability is due to many factors both natural and connected directly with the technology applied at a given time to protect against dusting. The conducted analysis of data indicates the effectiveness of reclaim treatments and satisfactory closure and reclamation of the facility