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lilly1326001
07-29-2015, 04:06 AM
How would one go about poisoning a large body of water (like a large lake) or rendering it completely un-drinkable somehow?

blacbird
07-29-2015, 04:20 AM
A crapload of chemical poison, or a bit of nasty radioactive stuff, like Poloniuim-210.

caw

lilly1326001
07-29-2015, 04:25 AM
Any way it could be purposefully poisoned with materials found in the 1700s?

ShaunHorton
07-29-2015, 04:29 AM
Dead bodies.

Roxxsmom
07-29-2015, 04:43 AM
They poison lakes to get rid of invasive fish species sometimes. I believe this renders the lake un-drinkable for a while, though the particular toxin used in these cases is not supposed to be dangerous to mammals. A recent article mentioned 16,000 gallons of the poison in question for a particular lake.

http://www.sfgate.com/bayarea/article/Lake-poisoning-seems-to-have-worked-to-kill-2520269.php

How subtle do you want this poison to be? If you want to make it something that will actually kill any human who drinks the water, rather than sickening them over time, it might need to be something very, very concentrated.

Polonium 210 is a really nasty radioisotope that kills in miniscule doses, but I don't know how practical it would be to get enough to dump in a reservoir or lake.

Some pesticides and industrial chemicals are very toxic to humans if ingested, but I'm not sure about the LD-50s or how much would need to be dumped into a lake to reach that concentration. And they'd generally have an offensive smell or taste.

Ah, just read the 1700 thing. If the goal is to simply make the water source non potable for a while, then yeah, large numbers of dead bodies (animal or human) would do it. Of course, one would need to have access to those too. For a small pond or well, one dead, bloated cow (or even a dog) might do it. For a larger lake, though? You'd need a large herd of dead cows.

Salt could also be used to render a lake or well not drinkable, of course. But for a large body of water, you'd need a lot of it. Poisons like arsenic (http://www.dartmouth.edu/~toxmetal/arsenic/history.html) were available back then. Might have to do some hunting around for various dangerous doses/concentrations of these compounds in water, and the number of gallons of water in a lake of the size you want to poison to get your answer.

Arsenic might be appealing for people who want to be subtle, because repeated lower doses over time can be lethal, and the symptoms mimic food poisoning or other gastrointestinal issues that were undoubtedly common in the pre-industrial world.

ShaunHorton
07-29-2015, 04:46 AM
So we have the time period of the 1700's. What is the end goal? Are we talking about poisoning and killing people who drink from the water source? Or do you just want people dissuaded from drinking from it?

Robert Dawson
07-29-2015, 05:06 AM
It depends what you mean by "large". For most regions, a large lake would be at least 1kmx1kmx10m - in some parts of the world it would be hundreds or thousands of times larger. Let's go with that smaller figure, which is 10 million cubic meters, or 10^10 liters.

Now, a person isn't going to consume more than a few liters of water per day. So you'd need to put about a billion doses into the lake. For hydrogen cyanide. the fatal dose is (Wikipedia) as low as 1.5mg/kg body weight, say 1/10 gram. So to make the lake water toxic, you'd need about 150 tonnes of hydrocyanic acid.

The LD50 for polonium is about 1 μg. So you'd need about a kilogram, which according to Wikipedia is about 10 years' production for the entire world. Might be hard to get your hands on...

For arsenic you'd need about a kilotonne. As for salt, you'd need significantly more than the (very roughly) part per thousand in Gatorade even to make it taste bad. So at least ten thousand tonnes. That's a lot of salt.

So I'd say that poisoning an entire large lake is pretty nearly impossible. Probably easier to hunt the victims down and inject them individually. Sorry to bear bad tidings...

lilly1326001
07-29-2015, 06:12 AM
Thank you all! Very helpful answers. Looks like I can finish my WIP off tonight :)

blacbird
07-29-2015, 06:19 AM
The LD50 for polonium is about 1 μg. So you'd need about a kilogram, which according to Wikipedia is about 10 years' production for the entire world. Might be hard to get your hands on...

Not to mention really really reallllllly bad to get your hands on.

But the answers in this thread also explain why there are virtually no historical examples of a big body of water being poisoned.

caw

Taejang
07-29-2015, 05:18 PM
The only large-scale poisoning that gets mentioned historically involved one of two things: dead bodies, or fecal matter. A large enough supply of either one, or both together, would do. It would just take a lot of it, and in the 1700s, it would take a very ingenious individual to get live animals/people to die in the lake/poop in the lake for a substantial amount of time, or else an army to move the material. Hence, historical records only speak of armies doing this, not individuals.

One idea would be to contaminate the lake's supply. If a river or stream flows into the lake, for example, you could park a large herd of cattle upstream and start slaughtering them. With sufficient current (perhaps spring runoff), the bodies will flow down-river, and those that get stuck will still contribute somewhat to the pollution of the lake. It would take a lot of cattle, however. More reasonably, get two armies to clash upstream and have the victors toss all the resulting dead bodies (or at least, those of their opponents) into the stream.

A man-made land slide caused by explosives could contaminate the water with sediment, making it undrinkable without being filtered for a few weeks. You would need a lot of explosives, however, and at least one person familiar enough with mining or some such who could direct where explosives are placed. Dynamite makes that much more feasible (if still very, very difficult), but dynamite wasn't developed until the mid 1800s.

Other than that, you'd probably need magic, science fiction, or a natural disaster to poison a lake in the 1700s.