Due to the eruption of a submarine volcano in the Ogasawara Islands in August 2021, the erupted pumice stones have become a serious problem.Drifting pumice stones drift around Okinawa Prefecture and are flooding around the coast.
The laboratory of Associate Professor Yuya Kubo of the Department of Bio-Environmental Chemistry, Fukuoka Institute of Technology has devised a new treatment method in which this pebble is naturally submerged in the sea and dumped into the ocean without imposing a burden on the environment.Pumice stones have a gas path generated when magma aggregates inside and a shrinkage nest created by volume shrinkage, and because they contain fine gas, their apparent density is lighter than that of seawater and they float on the sea surface.Kubo Laboratory, who thought that "floating" pumice stones was a problem, made it possible to submerge them in the sea by removing gas from the pumice stones and returning them to their original state, which is heavier than seawater.
In this method, the container containing the pumice stone is decompressed to a state close to vacuum to remove gas from the pumice stone and create an inundation path.After that, when seawater is put into the container and returned to atmospheric pressure, the pumice stones rapidly invade and become heavy, so that they can be subsided in the sea.
In the experiment, when pumice stones were crushed to a diameter of about 2 mm, 70 to 80% could be subsided by decompression treatment.Although there are individual differences in how gas enters the inside of pumice, it is demonstrated that 40 to 99% of pumice can be submerged depending on the size of the diameter.
In the land treatment of pumice stones currently under consideration, there remains a concern that soil may be damaged even if it is landfilled, and that the material may be corroded even if it is used for cement or sand.The cost of collection and transportation will be enormous.On the other hand, the method devised by Kubo Laboratory to submerge pumice stones on the deep sea floor can significantly reduce costs and labor, and there is no impact on the environment due to underwater dumping.
A patent has already been filed for the present invention, and it has been proposed as a highly feasible solution to a social problem.
