Hydrogen Sulfide

Dave Marshall, Sat Aug 25 2007, 07:40PM

We've had a series of odd incidents in my home town of Meadville, PA over the last few weeks. On three separate occasions citizens have called 911 reporting an overwhelming smell of rotten eggs. Further investigation by the fire department revealed relatively high concentrations of Hydrogen Sulfide coming from unknown sources, but affecting entire blocks of the city. The eventual conclusion is that regardless of the source, it was propagating through the sewer/storm drain system. The concentrations haven't been high enough to present a really serious health risk, but evacuations of 100 or more houses were done in all cases. The gas dissipated within a few hours of appearing in all three cases.

Now there is all sorts of speculation about a) where the stuff is coming from and b) how its getting into the sewer system.

This is a very small (15,000 people) but highly industrial city, home to some 300 tool and die, forging, and plastic injection companies, along with ChannelLock tools and several other major manufacturers. I can't think of what sort of uses those businesses might have for the substance, but I don't think industry is the source.

The first two incidents were in the same location, about a 4 block area bordering between the commercial and residential districts of the town, and just down hill from Alleghany college. The most recent incident yesterday was in a residential area nearly 5 miles from the first two.

Anyone know what uses it might have for industrial purposes, or what some other sources might be? My current theory is some college student got ahold of the stuff at the chemistry lab and has been dumping it intentionally as a hoax. The college here is the oldest west of the Appalachians, and has well known and very active chemistry program. Would it make sense that they'd have it in the lab?

Dave
Re: Hydrogen Sulfide
Hazmatt_(The Underdog), Sat Aug 25 2007, 08:20PM

Well... H2S is really a gas at STP so it would be difficult to disperse in that form unless you had it in a compressed gas cylinder.

The H2S is likely the result of an industrial waste product reacting with organic material.
Re: Hydrogen Sulfide
Sulaiman, Sun Aug 26 2007, 07:46AM

I guess you'd have to look for the source of the Sulphur
the most likely being sulphuric acid.
Re: Hydrogen Sulfide
Bored Chemist, Sun Aug 26 2007, 08:47AM

It's pretty difficult to reduce sulphate to H2S but there are bacteria that can do it.
Overall, since H2S is a known product of anaerobic fermentation and a known constituent of sewer gas I think it's most likely that this H2S is of natural origin.
I accept that it could be some student messing about or accidentally releasing something like thiourea which hydrolyses to H2S but I think you just have a rather smelly sewer.
Has the weather been unusual?