| Summary: | Phosphogypsum (PG), an acidic byproduct of phosphoric acid production during phosphate fertilizer manufacturing, is commonly stacked on the facilities and capped with soil at decommissioning. The research evaluated soil capping depth (0, 8, 15, 30, 46, 91 cm) effects on response of five seeded grasses, water movement across the soil / PG interface, leaching, radon gas, gamma radiation and hydrogen fluoride emissions. Vegetation response was not affected by cap depth and plant rooting into PG had no detected adverse effects. Soil water fluctuated more at shallow (0, 8, 15) than thick (30, 46, 91) caps, and water quality on caps < 30 cm was not affected by cap depth. Increased cap depth was associated with decreased gamma radiation, while radon gas and hydrogen fluoride emissions had variable responses. Implementation of these findings into a reclamation program in Alberta will be useful for designing a suitable and cost effective cover system. === Land Reclamation and Remediation
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