Why is the Ocean Waters Salty? Is it getting Saltier?

 

Over the last few days in late August 2023, I have been receiving at least over a dozen alarming videos and claims from WhatsApp groups of Japanese seafoods being contaminated by radioactivity following the earthquake and tsunamis resulting in radioactive wastes being discharged from the Fukushima Dai-ichi nuclear power plant in Japan.

On March 11, 2011, a 9.0 magnitude earthquake struck 128 km off the Northeast Coast of Japan triggered a series of tsunamis that struck nearby shorelines with only a few minutes’ warning. The disaster left dozens of villages along nearly 322 km of coast heavily damaged or completely destroyed.

The waves, some of which measured more than 12 metres, also struck the Fukushima Dai-ichi nuclear power plant 241 km north of Tokyo, disabling the plant’s emergency systems and causing emergency crews to use seawater to cool the damaged reactors.

Since everybody is alarmed by the waste water from the Fukushima laced with radioactivity being discharged into the sea around Japan. They now claim the presence of radioactivity in seafood from Japan. 

Let me explain.

The waste water Japan is discharging into the Pacific Ocean contains mainly tritium. 

Natural tritium is produced as a result of the interaction of cosmic radiation with gases in the upper atmosphere. There is about 7.3 kg. of it present in the atmosphere, about 150 to 200 g per year.

The radioactivity in the Fukushima water is almost entirely tritium, a type of hydrogen. For scale, the Pacific Ocean contains 8,400 grams of pure tritium, while Japan will release 0.06 grams of tritium every year out of a total of 3 gm

Scientists in South Korea have used computer simulation to map out how the Fukushima tritium would move with the ocean currents. What they have shown was tritium levels around Korean waters would increase by less than six parts per million.

Nuclear reactors in other countries too realises tritium every year, probably double the amounts Japan will now be releasing, yet together with those already present in the atmosphere, they show no biological or health hazards on life on Earth. 

Not just that alone. Japan intends to take 40 years to slowly release it to add just 0.06 g of tritium into the Pacific Ocean. This is less than 0.001 % being added each year. 

A 2021 study postulated that eating fish for a lifetime caught a few km from the Fukushima wastewater outlet increases the tritium radiation by 0.02 micro-sieverts. This is less than a banana, which contains the equivalent of 0.1 micro-sieverts.

The same study also demonstrated a lifetime exposure to all other isotopes is 5 micro-sieverts, and this is equivalent to a dental x-ray exposure. It is also claimed that a fish can be in the same water for 50 years, but the amount of radiation gathered up is the same as one dental x-rays contact.

A fish caught 20 km from the wastewater discharge diminishes to no radioactivity.  In comparison, the natural background radiation is 1500 to 3500 micro-sieverts per year.

According to one source, the maximum marine dose near the outlet is 7 micro-grays per year. This is more than 10,000 times smaller than the zero-effect benchmark of around 90,000 micro-grays per year.

Collectively, tritium and carbon-14, subscribe to less than 0.08 % of the ocean radioactivity.  The Pacific Ocean itself already naturally stores 18 -20 million gm of carbon-14. The Fukushima waste discharge shall add just one extra gram of carbon-14 into it.

Let me put this in a simpler non-technical way for us to understand.

It has been estimated that there are about 1.335 billion cubic kilometres of oceans on earth. This is 1.335 x 10 ²¹ litres of water (1 cubic km = 10 12 litres) 

The data I got from various sources puts the estimate at 1,362,145,400 cubic kilometres.

There is already 26.8 ± 14 kg of tritium present in the oceans of which 3.8 kg are of natural origin. Let’s put 21 kg (21 000 000 mg) in the ocean waters as a modest figure. This works out to be 1.6 x 10 ¹⁴ (0.0 000 000 000 000 16) mg per litre of naturally occurring trillium in the ocean water.

But there was only a total of 3 gm of tritium in the Fukushima reactor. Dissolve 3 gm (3,000 mg) of tritium inside 1.335 x 10²¹ litres of ocean waters. This works out there would only be 2.2 x 10 ¹⁸ mg or 0.000 000 000 000 000 0022 mg of tritium per litre of ocean waters throughout the oceans discharged from the damaged Fukushima nuclear reactor.

No analytical instrument available to us can detect this infinitesimal teeny-tiny amount to such an infintestimal level as 0.000 000 000 000 000 0022 mg per litre of tritium or any substance at all.

Maybe those who keep shouting about radioactive food toxicity from Japan can. But I can’t even with the best and the most sensitive instrument we use in analytical chemistry.

Japan shall use the Advanced Liquid Processing System (ALPS) to remove radioactive isotopes such as cesium-137, strontium-90, and iodine-129 but ALPS cannot isolate tritium. So this rare radioactive water isotope will be released.

The liquid waste currently stored by Japan is mainly ordinary water with 3 g of tritium in it. It is being stored in tanks that can fill 500 Olympic size swimming pools, and Japan intends to take 40 years to release them bit-by-bit into the Pacific Ocean.

Even that, the natural tritium present in the ocean pales compared to other radioactive substances such as 91 % are from potassium-40, 8.6 % are from rubidium-40, and 0.3 % from uranium which were already present in the ocean since Earth was formed 4.5 billion years ago.

Please read my explanation on the Fukushima Disaster: Radioactivity found in the Pacific Ocean?

I have posted it 7 years ago on Friday, November 25, 2016 showing there was hardly any health risk here: 

Scientific Logic: November 2016

In my opinion there is hardly any health risk consuming any fish or any seafood caught anywhere around Japan or elsewhere as there is hardly any trace of radioactivity in them due to the huge diluation by ocean waters mixed into the wastewater  

The recent videos and warnings sent to me by others lead me to write this article on something similar, namely, if the salt content in the oceans is getting more and more concentrated below this line.

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When I was in school, I read a story about why the sea became salty, not realizing there were many similar stories from Iceland, Norway, Denmark and Germany and even from the Philippines. Here are some of them you may read for yourself.

https://sites.pitt.edu/~dash/type0565.html

But today let us give a more scientific explanation whether or not our oceans are getting saltier?

Let’s have a brief look.

We have a lot of salty water on our planet. Oceans envelop about 70 percent of the Earth's surface and about 97 percent of all water on and in the Earth is saline.  By some estimates, if the salt in the ocean could be isolated and spread evenly over the Earth’s land surface it would form a layer more than 166 metres (500 feet) thick, about the height of a 40-story office building. But where did all this salt come from? Salt in the ocean comes from rocks on land, and from sea storms to the land and back into the oceans through rivers.

Rains on the land contain some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid. The rain physically erodes the rock, and the acids chemically break down the rocks and carry salts and minerals along in a dissolved state as ions.

The ions in the overflow are carried to the streams and rivers and then to the ocean. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Other dissolved minerals are not used up and are left for long periods of time where their concentrations increase over time.

Sodium and chloride combined as salt are the two most common ions in seawater. They constitute over 90% of all dissolved ions in seawater. The concentration of salt in seawater (its salinity) is about 35 parts per thousand.  

About 3.5% of the weight of seawater comes from the dissolved salts. In a cubic mile of seawater, the weight of the salt (as sodium chloride) would be about 120 million tons. A cubic mile of seawater can also contain up to 11.3 kg (25 pounds) of gold and up to 20.4 kg (45 pounds) of silver.

1 cubic mile (4.16818 cubic km) of sea water contains 1,101,117,147,000 gallons  (4168181823818 litres) of water. This is 10 ^12 litres of water per cubic km of water. (The density of seawater on the surface ranges from about 1020 to 1029 kg/m³, depending on the temperature and salinity. At a temperature of 25 °C, the salinity of 35 g/kg and 1 atmospheric pressure, the density of seawater is 1023.6 kg/m³).

Scientific theories behind the origins of sea salt started with Sir Edmond Halley (the discoverer of Halley’s Comet) in 1715, who suggested that salt and other minerals were carried into the sea by rivers, having been leached out of the ground by rainfall runoff. Upon reaching the ocean, these salts would be retained and concentrated as the process of evaporation (hydrologic cycle) removed the water.

Halley noted that of the small number of lakes in the world without ocean outlets such as the Dead Sea and the Caspian Sea have the highest salt content. Halley termed this process "continental weathering".

Halley's theory seemed plausible. Sodium may have been leached out of the ocean floor when the oceans were first formed. The presence of the other dominant ion of salt, namely chloride, was from "outgassing" of hydrochloric acid as chloride together with other gases from Earth's interior via volcanoes and hydrothermal vents. The sodium and chloride ions subsequently became the most abundant constituents of sea salt.

Ocean salinity has been stable for millions of years, most likely as a consequence of a chemical / tectonic system which recycles the salt. We shall discuss this later.

Since the ocean's creation, sodium content has stabilized. It is no longer leached out of the ocean floor, but instead is captured in sedimentary layers covering the bed of the ocean. One theory is that plate tectonics result in salt being forced under the continental land masses, where it is again slowly leached to the surface.

The water on Earth exists in cycles. Called the hydrologic cycle, it involves the continuous circulation of water in the Earth-Atmosphere system. At its core, the water cycle is the motion of the water from the ground to the atmosphere and back again. Of the many processes involved in the hydrologic cycle, the most important are evaporation and transpiration.

About 1.25045 x 10 ¹⁴ cubic meters or 30,000 cubic miles of water evaporate from the ocean each year. This falls as rain or snow to be returned to the oceans in cycles.

However, these cycles of evaporation and rain are not balanced. Over the oceans only water evaporates and falls as rain which is almost pure water. The rain pours over the land. It then dribbles through the soil to pick up soluble chemicals, running them into rivers into the ocean.

River water actually contains about 1/ 100 of 1 percent salt but not salty enough to taste. But does it have an implication to make the ocean saltier, or does it?

We would think then the ocean is constantly gaining traces of salt and other chemicals dissolved from the land but loses none that it evaporates. If this is true then the oceans should be growing saltier and saltier very slowly, and over the millions of years of rainfalls, the salt should mess up greatly.

River water also carries its salt into some inland lakes. This water is not discharged into the ocean. In these lakes the dissolved material accumulates as it does in the oceans.

If the lake is located in a hot region of the land, its average rate of evaporation is greater than that of the oceans. Hence, the dissolved material accumulates more rapidly and can become far saltier than the ocean. For instance, the Dead Sea bordering Israel and Jordan has 25 percent dissolved matter. It is so salty that nothing can thrive in it. It is so dense that we can float on the water.  

The salinity in other parts of the world varies with temperature, evaporation, and precipitation. Salinity is generally low at the equator and at the poles, and high at mid-latitudes. The average salinity is about 35 parts per thousand.

If the oceans continue to gather salts and other dissolved minerals like the Dead Sea, would the oceans be dead too eventually? Theoretically it would if not for other events which tend to reduce the salt content.

Storms at sea for instance blow sprays far inland, and dissolved salts are carried with the sprays far into the interior to deposit and to distribute dissolved salts over the land.

What is more important is, certain combinations of dissolved substances, when present in sufficient concentration, combine to form insoluble compounds that sink to the bottom of the ocean.

 Other chemical compounds, though not insoluble in themselves, can combine with other materials on the ocean floor. Other substances washed into the ocean are absorbed into the cells of ocean organisms.

The outcome is that the ocean is far less rich in dissolved matter or even saltier than it ought to be if we compute all other materials that must have been brought into it by the rivers over the past few billion years.

 

 Contrastingly, the ocean floor is quite rich in substances that must have come from land. Large quantities of metals and pollutants lie in lumps distributed over the ocean floor.

Furthermore, in the course of time shallow arms of the ocean may be cut off by emerging bits of land. These bits of the once ocean gradually evaporate, leaving behind large quantities of the dissolved material in the ocean which has then returned to land.

Salt mines are an example. We can obtain vast quantities of salt and lesser quantities of other substances, are the leftover remnants of such dried-up bits of the ocean. 

But then if 8 billion people living on this world consume 6 g of salt each day, then 4.8 x 10 ¹⁰ gm (48,000 metric tons) of salt will return into the ocean everyday through the urine of 8 billion people even if dried up lands reclaimed the salt from the ocean. It looks like salts in the oceans into land and back to the ocean again are like cycles of rains and evaporation. 

Well, then, what would the overall results be? Is the ocean getting a tiny bit saltier over a long time, or is it getting less salty? Does it sometimes swerve in one direction, sometimes in the other, keeping a balance on an average? I don’t think geologists or other scientists really know.