## Text

Physicist, Startup Founder, Blogger, Dad

## Wednesday, July 28, 2010

### BP oil spill Fermi estimates

This isn't meant to minimize the environmental horror of the BP oil spill, but I can't resist some rough estimates. (I did this quickly, so please correct my errors.)

100 days x 50k barrels/day x 150 liters/barrel = 750 million liters

Call it a billion liters of oil: 10^9 liters

Gulf of Mexico: over 2M cubic kilometers of water, or 2 x 10^18 liters

Suppose the spill is concentrated in 1 percent of the Gulf's area (a region 10% by 10% of the Gulf's linear dimensions - about 50 miles by 100 miles). This would presumably only be the case for a limited amount of time, and concentrations would fall off as the oil disperses further. Of course, if the oil is concentrated on a 2-dimensional surface slick, that would be quite bad for anything in the slick.

Then, assuming uniform dispersal within this sub-region, the oil concentration is about 1 part in ten million, or .1 ppm.

Googling around (e.g., ppm oil toxic), I couldn't find evidence of toxicity at any concentrations lower than 1 ppm.

So, aside from shocks to otherwise already endangered species, it seems the long-run effects of the spill won't be that bad. Don't yell at me -- I'm an environmentalist! But numbers don't lie...

Luis Enrique said...

some other potentially good news, that I'm not qualified to evaluate, here:

http://www.rationaloptimist.com/blog/oil-runs-out

David said...

Eric Weinstein's brother is a biologist. He would probably be happy to engage your estimation of the outcomes.

Jonny Good15 said...

The volatiles in the oil will evaporate, the parts that can be decomposed by bacteria and other organisms will also decrease the magnitude greatly. This will happen very quickly. What is left, may be even more miniscule than your estimate. Santa Barbara has plenty of small tar balls wash up on the beach, but the effects don't seem to be bad. The immediate effects are of course bad, but in the long term, we may actually forget this happened.

Moeder said...

But Steve, what about the Corexit?

steve hsu said...

Even if the Corexit (or oil itself) kills everything in the 1% sub-volume of water of my calculation, that leaves 99% of the life in the Gulf intact. In other words, it's hard to see a long term impact of this disaster.

You have to have a kind of "green nightmare" hypothesis to get to a long term effect: see, this Corexit stuff will never be broken down, it will linger in the Gulf and (even at parts per BILLION concentration) cause dangerous mutations or birth defects in the wildlife, and then ...

Eric Foss said...

Bioconcentration is one wild card here. I have no idea how much petroleum-based hydrocarbons or dispersants get bioconcentrated. If the bioconcentration is significant - and I imagine that whatever bioconcentration of oil occurs is much worse with heavy use of dispersants - then any calculations of environmental impact based on the assumption that oil and dispersants are distributed based on volume_released divided by volume_of_the_gulf go out the window.

Dave Bacon said...

Effects on larvae? http://dx.doi.org/10.1016/0141-1136(85)90102-3 "The results showed that oxygen consumption of the larvae at the time of final yolk absorption (5–7 days post hatching at 5°C) is strongly suppressed by oil exposure at concentrations down to 50 ppb. No effect on the oxygen uptake, however, was found during the egg stage."

Interestingly according to this Science article http://www.sciencemag.org/cgi/content/full/302/5653/2082 the oil from the Valdez the "decay rate" of the oil slowed down with time and substantial oil stuck around in cobbles of stream banks where it continued to kill salmon embryos.

Anton said...

Unless oil tends to clump together forming blobs. Hydrocarbons have hard time mixing with water and tend to minimize the interface area. It's energy consuming process.

old_fart said...

This calculation was in the back of my mind...this weekend realized that the computation was volume ratios. Since the molecular weight of oil is much greater than water the ppm should be scaled by the ratio of molecular weights. Crude is a mix of molecular weights but for a Fermi calculation ten times the MW of water is reasonable - so scale down by 10 to 1 part in .01 ppm, or 10 parts per billion.

Vijay_pawar said...

Why are you such a pussy? "I'm writing something that may upset an uber-sensitive irrational enviro-nazi with an emotional investment in doomsday scenarios! Don't yell at me!"

Would one of your MMA heroes do that? "I want the belt. Look, even the odds makers think I have a significant probability of beating the champ. Don't yell at me!"