Analysis of wind-driven resuspension of metal mine sludge in a tailings pond

Abstract

Shallow water covers, typically less than 2 m deep, are commonly used to store tailings and minimize environmental degradation. Studies have, however, shown that wind induced waves can erode and resuspend tailings in areas where the water cover is much shallower than 1 m, possibly leading to oxidation of sulphide minerals, acid generation, and release of heavy metals. The present work investigated erosion and resuspension of co-disposed, cohesive mill tailings and lime neutralization sludge in a tailings pond located at the Heath Steele mine site, near Miramichi, New Brunswick, Canada. From measured wind data and published equations, suspended sediment concentrations were modeled for various water cover depths and compared to measured total suspended solids (TSS) values and the federal effluent discharge guideline of 25 mg L–1. The computed suspended sediment concentrations agreed with those measured at the effluent discharge point. The results show that winds blowing in the direction of the major axis of the pond contributed most to resuspension and elevated TSS. Key words: cohesive mine tailings and sludge, critical shear stress, wind-induced resuspension, effluent water quality.

Fish environmental DNA is more concentrated in aquatic sediments than surface water

“…However, since resuspension occurs when shear stress on the sediment bed exceeds a critical threshold value (Vanoni, 2006), studies monitoring for very recent occupancy should avoid sampling shallow lakes or ponds experiencing high bed shear stress conditions. For example, increased resuspension of sediment particles has been observed during or immediately after high wind events (Evans, 1994), in areas with significant wave action (Mian and Yanful, 2004), and in areas with substantial bed loads (the surficial sediments that are transported along the bed; Debnath et al, 2007). Similarly, results from a natural stream experiment with tracer bacteria seeded in sediments (Jamieson et al, 2005) suggest that water sampling in rivers during unusually high flow events would increase the chance of collecting old eDNA resuspended from sediment beds that are stable at lower flow.…”

Sediment resuspension in a shallow lake

“…Waves and currents may induce shear stresses in different directions, in which case the shear stresses have to be added in vector form [Horikawa, 1978;Nielsen, 1992;Raudkivi, 1998]. The magnitude of the bottom shear stress due to currents, t curr , may be approximated as a fraction (about 10%, [Reid, 1957]) of the surface, wind-induced shear stress [Mian and Yanful, 2004]. The wind-induced shear stress at the surface of the lake, t 0 , is in turn usually estimated using a quadratic drag law.…”

“…[16] The maximum shear stress exerted on the bottom sediments due to wind-induced waves, t wave , can be calculated as [Raudkivi, 1998;Mian and Yanful, 2004] …”

“…[35] Figure 13 compares entrainment rates predicted by using the Mian and Yanful [2004] and the extended García and Parker formulations, obtained with simulated ( Figures 13a and 13c) and measured (Figures 13b and 13d) wave characteristics for the whole observation period. Figure 13 indicates satisfactory agreement between predictions with both formulas, particularly at higher entrainment levels.…”

Water Management Strategies Against Toxic Microcystis Blooms In The Dutch Delta

“…Sediment focusing is often induced by shear stress at the sediment-water interface. Shear stress at the sedimentwater interface of stagnant lakes, like Lake Volkerak, is largely caused by wind-driven water motion (Mian and Yanful 2004). We therefore assume that horizontal transport of the benthic Microcystis population from shallow to intermediate and deeper parts of the lake can be described as…”