By Daniel Puchert Partially state-owned telecommunications company Telkom announced in its financial results for the year ending 31 March 2025 that its ADSL subscribers had more than halved to under 30,000. According to the company’s operational data, ADSL lines decreased from 64,959 in March 2024 to 29,770. This 54.2% decline highlights that the legacy broadband technology is slowly approaching the end of the road. Telkom’s ADSL business peaked at the end of March 2016 with 1.01 million subscribers — two years after fibre upstart Vumatel broke ground in Parkhurst . What followed was a sharp decline in Telkom ADSL subscribers. Customers connected to its copper networks decreased by more than 500,000 over the next four years. This was partly driven by Telkom itself, which began actively switching off its copper network in some neighbourhoods. If it did not have fibre in the area, it would offer a “fixed line lookalike” wireless service that ran over its cellular ...
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Sediment plumes from deep-sea mining become turbulent cloud
Deep sea. (Image by Dimitris Siskopoulos, Flickr).
Midwater sediment plumes that are discharged through pipes used by mining machinery that descend 1,000 meters or more into the ocean’s aphotic zone become a highly turbulent cloud of suspended particles that mix rapidly with the surrounding ocean water, when initially pumped out.
New research by oceanographers at MIT, the Scripps Institution of Oceanography, and other institutions made this discovery after carrying out the first-ever experiment to study the sediment plume that mining vessels would potentially release back into the ocean.
Based on their observations, they developed a model that makes realistic predictions of how a sediment plume generated by mining operations would be transported through the ocean.
THE RESEARCHERS DEVELOPED A FORMULA THAT CAN BE USED TO CALCULATE WHAT VOLUME OF OCEAN WATER WOULD BE IMPACTED OVER THE COURSE OF A 20-YEAR NODULE MINING OPERATION
In a paper published in the journal Nature Communications: Earth and Environment, the scientists explain that the model predicts the size, concentration, and evolution of sediment plumes under various marine and mining conditions. These predictions, they say, can now be used by biologists and environmental regulators to gauge whether and to what extent such plumes would impact surrounding sea life.
“The science of the plume dynamics for this scenario is well-founded, and our goal was to clearly establish the dynamic regime for such plumes to properly inform discussions,” said Thomas Peacock, professor of mechanical engineering at MIT and co-author of the study.
How the model was tested
To pin down plume dynamics, the team set sail 50 kilometres off the coast of Southern California aboard the Sally Ride. They brought with them equipment designed to discharge sediment 60 meters below the ocean’s surface.
“Using foundational scientific principles from fluid dynamics, we designed the system so that it fully reproduced a commercial-scale plume, without having to go down to 1,000 meters or sail out several days to the middle of the CCFZ,” Peacock said.
Over one week the team ran six plume experiments, using novel sensors systems such as a Phased Array Doppler Sonar (PADS) and epsilometer developed by Scripps scientists to monitor where the plumes travelled and how they evolved in shape and concentration. The collected data soon revealed the turbulent cloud.
“There was speculation this sediment would form large aggregates in the plume that would settle relatively quickly to the deep ocean,” Peacock said. “But we found the discharge is so turbulent that it breaks the sediment up into its finest constituent pieces, and thereafter it becomes dilute so quickly that the sediment then doesn’t have a chance to stick together.”
Reality matched lab tests
Previous to their field trip, the scientists developed a model to predict the dynamics of a plume that would be discharged into the ocean. When they fed the experiment’s initial conditions into the model, it produced the same behaviour that the team observed at sea, proving the model could accurately predict plume dynamics within the vicinity of the discharge.
The group then used these results to provide the correct input for simulations of ocean dynamics to see how far currents would carry the initially released plume.
“In a commercial operation, the ship is always discharging new sediment. But at the same time, the background turbulence of the ocean is always mixing things. So you reach a balance. There’s a natural dilution process that occurs in the ocean that sets the scale of these plumes,” Peacock said. “What is key to determining the extent of the plumes is the strength of the ocean turbulence, the amount of sediment that gets discharged, and the environmental threshold level at which there is impact.”
Based on their findings, the researchers have developed formulae to calculate the scale of a plume depending on a given environmental threshold.
For instance, if regulators determine that a certain concentration of sediments could be detrimental to surrounding sea life, the formula can be used to calculate how far a plume above that concentration would extend, and what volume of ocean water would be impacted over the course of a 20-year nodule mining operation.
The bill is the latest in a string of U.S. legislation attempting to cobble together a national strategy to produce more lithium, rare earths and other strategic minerals.
There are a lot of people, but the oceans are very big. Rosley Majid/EyeEm via Getty Images If everyone on Earth sat in the ocean at once, how much would sea level rise? March 29, 2021 2.07pm SAST Author Tony E. Wong Assistant Professor of Mathematical Sciences, Rochester Institute of Technology Disclosure statement Tony E. Wong does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment. Partners Rochester Institute of Technology provides funding as a member of The Conversation US. The Conversation is funded by the National Research Foundation, eight universities, including the Cape Peninsula University of Technology, Rhodes University, Stellenbosch University and the Universities of Cape Town, Johannesburg, Kwa-Zulu Natal, Pretoria, and South Africa. It is hosted by the Universities of the Witwatersrand and Wester...
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