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katie
13th February 2004, 17:31
I was reading online...trying to find low light, cold water plants...and found mention that the coiled metal used to weight plants is lead, and that it leaches into the water. Is this harmful to newts?

jesper
13th February 2004, 18:32
Yes its lead alright, same thing that we use in the lab when working with gamma-radiating substances LOL

The questions is in which amounts it will be oxidize and thus dissolve.

Lead, both in itself and its derivates, are very toxic. However, lead easily reacts with oxygen(oxidation of lead, reduction of oxygen(two electron transitions)) into a protective layer of PbO(s) making lead very stable.

Actually, waterpipes of the roman empire were made out of lead. They are so stable that they remain still ~2000 years after their making.

Now listen to this!
Years ago historians thought that one of the factors behind the fall of Rome was that its population was lead-poisoned....
LOL, obviously none of them thought much about the fact that if they were unstable thus giving off lead to the water they certainly would not still be around!http://www.caudata.org/forum/clipart/signs.gif
http://www.caudata.org/forum/clipart/biggrin.gif

jesper
13th February 2004, 18:46
Very good question indeed, here comes a likely reaction for lead in water:

Pb(s) + 2OH(-) -- > PbO(s) + H2O + 2e(-)
Half-cell(ie we need something that can pick up the two electrons(reduction))

The standard electrode potential is 0,58 making it a spontaneous reaction.

(~pH 7 gives [OH(-)] ~0,0000001 M)

jennifer
13th February 2004, 22:54
Jesper, While I am impressed by your erudite answers, you haven't really addressed her question (at least not in the way most of us understand). Would I be interpreting correctly that you are saying: not enough lead comes off the lead weights to pose a hazard? This is what I have heard elsewhere and it's kind of neat if your equations substantiate this. What does 0.0000001M equal in parts per million (the usual way of discussing toxicity of lead)?

katie
13th February 2004, 22:56
<blockquote><hr size=0><!-quote-!><font size=1>Jesper Danielsson (Jesper) wrote on Friday, February 13, 2004 - 18:32 : (#POST19270)</font>

&quot;lead easily reacts with oxygen(oxidation of lead, reduction of oxygen(two electron transitions)) into a protective layer of PbO(s) making lead very stable&quot;<!-/quote-!><hr size=0></blockquote> Jesper, I understand what you said to mean that once the lead comes in contact with the oxygen in my aquarium water, the lead is in a form that is "locked away" from being able to harm my newts?

~Moi

jesper
13th February 2004, 23:52
Oh sorry for being diffuse, I get carried away sometimes...http://www.caudata.org/forum/clipart/blush.gif
Thanks for the compliment Jen, even though I don't understand what erudite means I take it as one. *looking frenetically for my dictionary
http://www.caudata.org/forum/clipart/happy.gif

Anyway, what I was saying is that when lead comes into contact with oxygen or water a protective layer of PbO(this is what makes the lead kind of bluish/grey shimmering) is created shielding the lead, which probably would dissolve to the point of toxicity without this layer. Now as I said before this layer is shielding the lead so effectively from the outside world that the roman lead-pipes have lasted for 2000 years.

The total meaning of this would be no, the lead doesn't contaminate the water.

jesper
14th February 2004, 00:22
Jen btw the mention of the concentration of OH- was only because I thought it good. The autoprotolysis(?) of water will produce 0,1 mol/l of this ion - I did not indicate any toxicity associated with that concentration thus I didn't express it in ppm.

I have the bible of toxicology in front of me here, Casarett and Doull's toxicology:the basic science of poisons. LOL, I was very interested in poisons once LOL. So I got loads of info on lead if you are interested.

Lead is usual in nature though it has no biological role and the toxicity level is thus quite high compared to many other toxins. The organ most sensitive is the liver who becomes intoxicated at about 10g/dl blood in adult human beings. The average intake is ~20g/day in the US.

What I want to say with this is that quite a lot has to be dissolved to intoxicate a living thing since we all live in an environment pretty full of lead. I would say that it is highly unlikely that a newt would be poisoned UNLESS the water is acidic. If the water would become acidic I would wager there would be a risk for intoxication in the longterm. Thinking of how the pet shops usually treat their newts, not very frequent water changes, dirty tanks with low pH (probably) it is not totally unreasonable to assume that lead from the weight would contaminate the water.
But under normal conditions I would say that there are no problems. This is my opinion.

jesper
14th February 2004, 00:23
Yep Katie you got the essential part! Didn't see your post, sorry!

alan
14th February 2004, 07:07
No, it's not harmful to the newts, especially assuming regular water changes. I wouldn't do it in soft, acid water where the lead will dissolve to some extent.
However, it *IS* harmful to the plants, which hate having their stems crushed together like this. So the take home message is:

Take the lead off your plants when you get them home and plant them properly http://www.caudata.org/forum/clipart/happy.gif

jesper
14th February 2004, 14:40
Hehe, go Alan go. A good point indeed.

^imp^
14th February 2004, 16:05
All plant weights in the United States are not lead. They're a zinc alloy.

Why would you want to keep the weights on, anyway? Its usually better to anchor plants with small stones/gravel/whatever.

^iMp^

jesper
14th February 2004, 16:24
Should be easy to make that distinction my mere weight then I suppose...

katie
16th February 2004, 17:22
Sorry, ^iMp^...old habit from when I kept fish years ago that uprooted things. It always seemed that whatever they yanked up would float and jam up my intakes. With the weights attached to the plants, if something got pulled up, it stayed generally where I'd placed it, and I could shove its roots back into the gravel.

I did learn back then that the stores often sold things that were floating plants tied in weighted bundles and "planted". If I "planted" these, the bottoms would just rot below the gravel, and eventually the tops would free themselves and float like they should have been allowed to do in the first place. When they actually thrived floating around with no roots, I learned from my mistakes. Learning in reverse is not a good thing, but this was pre-computer days, the library was far from home, and the salespeople knew about as much as I did.

~KatieGatie