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Phosphorus (P) losses from agricultural fields through leaching are the main contributors to eutrophication of lakes and rivers in North America. Adoption of P-retaining strategies is essential to improve the environmental quality of water bodies. The main objective of this study is to evaluate lime as a soil amendment in reducing phosphorus concentration in the leachate from three common soil textures with neutral to alkaline pH. Phosphorus leaching from undisturbed soil columns (10 cm in diameter and 20 cm deep) as well as small repacked columns was investigated and compared in this study. Lime (high calcium hydrated lime) at the rate of 1% by air-dried soil mass was applied to the topsoil of the columns. Both sets of experiments followed a full factorial design with two factors of soil texture at three levels (sandy loam, loam, and clay loam) and treatment at two levels (control and limed) with three replicates. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was performed on the control and limed soil samples to confirm the formation of calcium phosphate compounds. For both intact and repacked columns, dissolved reactive phosphorus (DRP) concentrations in the leachates from limed sandy loam and limed loam soil columns was significantly reduced, while DRP in the limed clay loam column leachates was not changed. Elemental mapping demonstrated that in limed sandy loam and loam soils, the calcium loadings on the soil surface were always linked with phosphorus. The formation of calcium phosphate compounds and the increased phosphate adsorption on the soil surface through Ca bridging could be the two main phosphorus-lime retention mechanisms. Total dissolved phosphorus (TDP) in the leachates of limed loam and limed clay loam indoor intact and repacked columns was reduced, while there was no change in that of the sandy loam soil. In finer textured soils, lime can increase TDP retention through the immobilization of organic phosphates. The impact of lime application on DRP and TDP varied with the soil texture. The lime-induced reduction in the DRP and TDP was variable between the intact and repacked columns demonstrating the importance of soil structure on phosphorus and lime interactions in the soil. Overall, lime application at the studied rate can be considered a promising soil amendment in mitigating phosphorus loss from non-calcareous neutral to alkaline soils.

Oil sands tailings have a limited ability to dewater and can also release toxic water, so finding a cost-effective tailings reclamation strategy has been challenging. End pit lakes (EPLs) are being examined as one potential approach to reduce fluid fine tailings (FFT) inventories for the oil sands industry. This study investigated the effect of adding lime (650 to 4000 ppm) on FFT dewatering and improving cap water quality under the simulated EPL scenario. The results illustrated that a high lime dose of 3500 ppm achieved the highest FFT water recovery, decreased the cap water alkalinity at the end of the experiment (after 90 d), and increased the possibility of cation exchange (at day 0). In contrast, the degradation of petroleum hydrocarbons was slightly enhanced at low lime dose of 650 ppm in comparison to high doses. In addition, the 650 ppm dose resulted in minimal change in the microbial cell counts at day 90, compared with high lime doses that resulted in a large reduction in the cell counts. Comparisons of toxicity of the FFT pore water after lime addition exhibited higher toxic effects for lime dosages >1600 ppm. Nevertheless, at all lime doses, low cap water toxicity (i.e.