Submarine Tailings Disposal (STD)—A Review

Abstract

Abstract:The mining industry is a fundamental industry involved in the development of modern society, but is also the world's largest waste producer. This role will be enhanced in the future, because ore grades are generally decreasing, thus leading to increases in the waste/metal production ratio. Mine wastes deposited on-land in so-called tailings dams, impoundments or waste-dumps have several associated environmental issues that need to be addressed (e.g., acid mine drainage formation due to sulphide oxidation, geotechnical stability, among others), and social concerns due to land use during mining. The mining industry recognizes these concerns and is searching for waste management alternatives for the future. One option used in the past was the marine shore or shallow submarine deposition of this waste material in some parts of the world. After the occurrence of some severe environmental pollution, today the deposition in the deep sea (under constant reducing conditions) is seen as a new, more secure option, due to the general thought that sulphide minerals are geochemically stable under the reduced conditions prevailing in the deep marine environment. This review highlights the mineralogical and geochemical issues (e.g., solubility of sulphides in seawater; reductive dissolution of oxide minerals under reducing conditions), which have to be considered when evaluating whether submarine tailings disposal is a suitable alternative for mine waste.

Evolution of Acid Mine Drainage Formation in Sulphidic Mine Tailings

“…Depending on the geochemical conditions of this final disposal site, the mineral assemblage in the tailings can undergo geochemical oxidative processes, which can lead to the release of metals, toxic compounds, and acid. The geochemical and mineralogical effects of disposal of mine tailings in reducing environments is reviewed in another paper of this special issue concerning submarine tailings disposal (STD) [3]. The present review focuses on the processes resulting from the exposition of sulphidic mine tailings to oxidation in on-land tailings impoundments.…”

“…If the pH is less than about 2, ferric hydrolysis products like Fe(OH) 3 are not stable and Fe (1), (2) and (4) The process of pyrite oxidation relates to all sulphide minerals once exposed to oxidizing conditions (e.g., chalcopyrite, bornite, molybdenite, arsenopyrite, enargite, galena, and sphalerite among others). In this process different amounts of protons are released [4] and the metals and other harmful elements or compounds are released to the environment.…”

“…The public becomes concerned and the mining operations have to compete with alternative land uses like agriculture, fisheries, or tourism. As a result, the mining industry is re-evaluating the option of submarine tailings disposal (STD), a heavily disputed practice used in some locations over the last few decades primarily resulting in negative impacts on the environment (reviewed in an other paper of this special issue on submarine tailings disposal (STD) [3]). …”

Scientific Considerations for the Assessment and Management of Mine Tailings Disposal in the Deep Sea

“…A rise in world population together with increased rates of economic growth in low and middle income countries over the last century has dramatically increased the demand for metals and minerals (Dold, 2014). In addition, over the span of the twentieth century, the demand for metals and minerals in high income countries has grown exponentially.…”

Mine Waste Characterization, Management and Remediation

“…Due to increasing amounts of mine wastes generated annually, and environmental and social issues surrounding disposal on land, mining companies are seeking alternative methods of disposal. Dold [13] reviews the mineralogical and geochemical issues arising from submarine tailings disposal. Diaby and Dold [14] continue the marine disposal theme by describing the results of the implementation of artificial wetland remediation cells on oxidizing marine shore tailings deposits.…”