9
votes
What is the meaning of the units Mg C?
Mg C is a tonne of Carbon.
An Mg - a megagramme - is a tonne. It's a silly way of writing a tonne for a general readership, but it's the strict SI equivalent of a tonne. So an "Mg C" is a tonne of ...
- 4,090
8
votes
Accepted
Is it true that "All life on earth gets its energy from the sun"? How much biomass is not derived from photosynthesis?
As you say, the existence of organism that live out of chemical compounds expelled by hydrothermal vents (Chemoautotrophs), immediately render the sentence "All life on earth gets its energy from the ...
- 17.6k
7
votes
How would a world entirely covered in oceans get the nutrients to support life?
If the planet is geologically/volcanically active hydrothermal vents are a way by which nutrients, in the way of minerals and chemicals, can enter the ocean.
Certain types of bacteria can consume the ...
- 24.1k
7
votes
The free oxygen (O$_2$) in the atmosphere is largely a result of what process?
You are correct in thinking that oxygen comes from photosynthesis. In fact it is so much associated with photosynthesis, as opposed to any inorganic process, that the presence of oxygen in the ...
- 14.2k
6
votes
where are the thickest limestone layers on earth ? (CaCO3)
Reading your comments I see that you're asking:
so could we find for example 1km high limestone layers on earth ?
The answer is definitely yes. Here's an example of a stratrigraphic geological ...
- 23k
6
votes
Accepted
Are there sufficient quantities of limestone to dump in the ocean to reverse acidification?
Getting figures on the amount of limestone available is difficult.
Apparently "limestone makes up at least 10% of the total volume of all sedimentary rocks".
One way to answer your question is by ...
- 24.1k
6
votes
How would a world entirely covered in oceans get the nutrients to support life?
On an ocean planet, nutrients can come either from space or from the bottom of the ocean, where they can leak from the crust trough different processes, perhaps with the help of submarine volcanoes or ...
- 17.6k
5
votes
Before the Great Oxygenation Event, where was the oxygen?
the great oxygenation event was caused by the evolution of photosynthesis, photosynthesis turns CO2 and water in to sugar and oxygen. so the oxygen came from CO2 and water.
keep in mind CO2 levels ...
- 6,803
5
votes
Nitrogen cycle semantics; nitrification/nitrogen fixation
I went to do a bit of research on this, and think that you can get a satisfactory answer just from the relevant wikipedia articles. Here are some select quotes:
Nitrogen fixation is a process by ...
- 3,366
5
votes
Accepted
Why don't all living beings die at night due to lack of oxygen?
The rates at which plants consume CO$_2$ and animals consume O$_2$ is minuscule compared to the vast amounts of CO$_2$ and O$_2$ in the atmosphere. The amount of change overnight is not even ...
- 1,207
5
votes
How is the equilibrium of 21% oxygen in Earth's atmosphere established?
Atmospheric oxygen is not in an equilibrium of 21%, it just changes very slowly. For instance, oxygen has decreased by 0.7% over the past 800 thousand years, likely due to increased erosion (which ...
- 13.4k
5
votes
Do trees capture more CO2 during a fast growth stage?
Right, there are a lot of misconceptions about this. They are mostly to do with the difference between the magnitude of carbon storage and the rate of carbon uptake, and also the difference between ...
- 494
4
votes
What is the age of the earliest traces of life on Earth?
The oldest (fairly) definitive fossils date from about 3.48 billion years ago (Ga) and consist of sedimentary structures associated with microbial mats living in coastal environments.[1]
Beyond this ...
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4
votes
Before the Great Oxygenation Event, where was the oxygen?
I'd like to add to the other answers.
Yes, it is correct that photosynthesis by cyanobacteria caused the rise of atmospheric oxygen. Some important points to talk about:
Estimated fossil fuels are ...
- 23k
4
votes
Accepted
Abiogenesis: Formation of Lipids from Montmorillonite
Good question! One that's stuck with me since reading about clay's purported role in providing scaffolding to early organic molecules in a Scientific American article from the late '80s. Many years ...
- 2,783
4
votes
Accepted
How quickly can coral fossilize?
First thing is that the sea-level wasn't necessarily that high when the reef was growing, Hondurus is on the edge of the Caymen Trough Fault Zone and experiences quite high rates of uplift, (...
- 4,260
4
votes
How far into the past would you have to go before you couldn't breathe the atmosphere?
850 million years ago and earlier oxygen levels were below 6%, which is the minimum for human survival. But at oxygen levels below 14% we start to be significantly impaired, and we have evolved with ...
- 1,935
4
votes
How do I convert an element measurement to oxides?
If you are talking about Table 2 of Chapter 8 in Principles of Igneous and Metamorphic Petrology (Winter, 2013), p. 146 in the second edition, then you are misreading the column headers. 59.3 is in '...
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3
votes
Accepted
Will photosynthesis based carbon sequestration always be more efficient than other chemical means - in terms of rate?
Rate.. no.
Brute Force
We can treat this as an industrial chemistry question. The brute-force method for carbon sequesteration is simply:
Extract CO2 from the air (using the acid/base chemistry, ...
- 1,082
3
votes
What is the meaning of the units Mg C?
When discussing about the carbon cycle in scientific papers, the gram is usually the reference unit used. Depending on what the particular topic is, and especially its scale, an appropriate prefix ...
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3
votes
Can you measure BOD/COD real time using any sensor?
There are multiple companies that provide COD sensors...
Real Tech Inc, LAR,
Detectronic, Endress-Hauser, and YSI...
but they all use spectrophotometry methods.
3
votes
Accepted
Can you measure BOD/COD real time using any sensor?
Realtech.com has a runtime monitoring senser solution for BOD/COD Sensor.
My understanding is that COD is straight-ward to measure in real-time but BOD monitoring cannot be done in real-time. The ...
- 5,949
3
votes
Accepted
Mixing equation for confluence of two rivers
You have to use mass weighted averaging to calculate the final concentrations of elements. The equation for your situation would be:
$\sf\bar{q}\ =\ \dfrac{m_1.q_1\ +\ m_2.q_2}{m_1\ +\ m_2}\ =\ \...
- 24.1k
3
votes
Are there sufficient quantities of limestone to dump in the ocean to reverse acidification?
Yes, there is much more than enough limestone, by several orders of magnitude, to neutralize the acidity that we are creating - so much so that I am not even going to bother with the back of an ...
- 14.2k
3
votes
Recreating the rock cycle
Here's an idea:
You can use dark chocolate and white chocolate. Use a grater to create "sediments": layers of alternating grated dark and white chocolate.
Now heat them up just before melting so you ...
- 23k
3
votes
How much net carbon can coral sequester?
Corals usually grow 1cm every year, some as slow as 2mm, some faster.
Coral sand density is about 1.5g /cm2, it's not the best estimate of coral weight. So, a coral organism of 10cm^2 produces 150 ...
- 1,339
3
votes
Accepted
Where does molecular hydrogen in the atmosphere come from?
I've found two sources for molecular hydrogen.
The photolysis of formaldehyde (See chemical formula 10 and see Novelli et al. 1999)
Anthropogenic sources.
While it isn't a source I think I should ...
- 8,684
3
votes
How far into the past would you have to go before you couldn't breathe the atmosphere?
Roughly 3,000,000,000 years ago Earth was a water world. This means terrestrial flora and fauna was 0%. Not much fun breathing in the atmosphere with limited photosynthesis from plants. And a nitrogen ...
- 81
2
votes
Why does Earth have abundant oxygen in the atmosphere?
My answer goes a little beyond the evidence -- there isn't much evidence.
The question
There's a lot of free oxygen now. This oxygen did not suddenly come from underground or from space. So it used ...
- 281
2
votes
What are the natural causes for methane formation?
The 'natural causes' of global methane emissions are, as you indicate, mostly of biological origin. To some extent it depends upon what you regard as 'natural'. There are many and differing estimates ...
- 14.2k
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