Reef Chemistry Question of the Day #247 Organic vs Inorganic Carbon

[SaltEverywhere]

I'm counting carbon atoms (weight or number), not moles of something they may be a part of.

let's have some math fun...


There are a lot of carbon atoms in each big whale (assume 300,000 pounds, guess 10% carbon (might be a low estimate due to blubber having a lot of carbon ), so maybe a million moles, or 7 x 10^29 carbon atoms, and quite a few whales (roughly one million, but most aren't that big). So 10^6 x 7 x 10^29 = 7 x 10^35 carbon atoms in whales.

There are also a lot of bicarbonate ions in seawater, with just one carbon atom each. A liter of seawater might contain 2 millimoles of bicarbonate, or 10^21 bicarbonate ions. Total volume of the ocean is about 1.3 billion cubic kilometers. There are 10^12 liters in a cubic kilometer, so that's 1.3 x 10^21 liters. Thus the carbon due to bicarbonate ion is about 1.3 x 10^42.

So there's very roughly 1.3 x 10^42/7 x 10^35 = ~2 million times as much carbon in bicarbonate as in whales.

Almost.


Avogadro's number is 6.022 * 10^23, so these should be "6 x 10^29" and "1.2 x 10^21" respectively. That means that the 1.3 should be multiplied by the 1.2 to become 1.6, and then the division at the end returns 1.6 x 10^42/6 x 10^35 = 2.6 million, which would round to 3 million instead of just 2 million.

Standing Ovations for both of you.

 

[SaltEverywhere]

Sorry to beat a dead whale, but it’s hard to let a good math exercise go. I just cant stop thinking about how big whales are and how small bicarbonate is. So just out of curiosity if we WERE to consider their relative weight, here’s what I came up with. Using 2 mmol/ liter bicarb x your estimate of the 10^12 liters of water in the ocean and multiplying by a molecular weight of 61g/mol (2x10^-3 mol/liter)(10^12 liters)(61x10^-3kg/mol)= 1.2x 10^8 kg of bicarb in the ocean, which is roughly 20,000,000 bags of Arm and Hammer baking soda from costco.
Now, it is surprisingly difficult to find accurate whale counts online. My best efforts reveal a million Minke whales at 4x10^3 kg each, 15k blue whales at 136x10^3 kg each, 200k humpbacks at 30x10^3 kg, and then I lost interest. With just these whales, that’s 1.2 x 10^10 kg of whale, 100 times heavier than the bicarb. If my math holds, I believe that this would conclusively prove that whales are very heavy.

 

[JimWelsh]

 

[Randy Holmes-Farley]

Using 2 mmol/ liter bicarb x your estimate of the 10^12 liters of water in the ocean and multiplying by .

The 10^12 is liters in a cubic kilometer of seawater, but there are more than a billion of those cubic kilometers in the ocean. So there are 1.3 x 10^21 liters in the ocean.

 

[Randy Holmes-Farley]

Very nice.

 

[SaltEverywhere]

The 10^12 is liters in a cubic kilometer of seawater, but there are more than a billion of those cubic kilometers in the ocean. So there are 1.3 x 10^21 liters in the ocean.

Ya, I woke up thinking about that. 20 million bags of bicarb seemed kind of low for an ocean. Sorry to all for that math error. Adding nine more zeros changes everything. I am withdrawing my claim that whales are large.

 

[SaltEverywhere]

 

[Randy Holmes-Farley]

lol

 

[AzReefn]

LOL
This thread is awesome! Too funny

 

[AzReefn]

Three statisticians go out hunting together. After a while they spot a solitary rabbit. The first statistician takes aim and overshoots. The second aims and undershoots. The third shouts out "We got him!" [emoji849]

 

[Randy Holmes-Farley]

And the answer is...


In the ocean, is there typically more inorganic carbon or organic carbon?

A. There is more inorganic carbon

Total inorganic carbon in seawater is about 2.05 millimole/kg, or about 25 ppm carbon. In order of decreasing concentration, it is present as bicarbonate, carbonate, unhydrated CO2, and hydrated CO2, which is carbonic acid, H2CO3.

Dissolved organic carbon varies substantially, but is usually between about 20 and 200 uM, or about 0.24 and 2.4 ppm C.

Particulate organic carbon averages out to a lower level than dissolved organic carbon, at 1-17 uM in surface seawater, or about 0.01 to 0.2 ppm C.

Happy Reefing!