samples from the bottom of the pond
samples from the bottom of the pond
We would like to be able to obtain water samples from different depths of a small lake. There is a small bridge that the students can stand on and lower a specimen jar down from, but how can we be certain that the sample is from the bottom, eg how can we stop it filling up before it gets to the bottom? We are thinking of some sort of contraption where we can lift the lid off once it has been lowered to the appropriate depth and reseal it before we lift it out of the water. Has anyone made or bought one of these before? Any advice appreciated.
Re: samples from the bottom of the pond
I used to do surveys of the lake sediment for Prof of chemistry at Newcastle uni.
I had a length of PVC downpipe - large diameter. I had a rubber bung that fitted on the top. And marked on the outside fo the PVC the different depths in black marker.
You could glue or otherwise attach strong string to the bung.
That way if you lower it vertically then no water enters the pipe. Then when you are at the appropriate depth pull the bung off and the pipe will fill up.
Then if you carefully replace the bung and lift the pipe vertically it shoudl contain the water that has entered it.
tricky part will be replacing the bung without students getting wet and without losing your sample.
I used to wade into the water in big waders up to my armpit- wonder if a teacher could be in a row boat and reattach the bung at water level.. practice on dry land before hitting the water though..
OR - what if you used a pipe as above, but had a plastic hose going through the bung and down to the bottom of the pipe, then when you get to the depth you want use a suction pump to pump out some of the water.
my samples were sediment - so that was easier than liquid, though an awful lot more smelly - peeeeeeeeeeeeeeuuuuuuuuuuuuuuuuuuwww
I had a length of PVC downpipe - large diameter. I had a rubber bung that fitted on the top. And marked on the outside fo the PVC the different depths in black marker.
You could glue or otherwise attach strong string to the bung.
That way if you lower it vertically then no water enters the pipe. Then when you are at the appropriate depth pull the bung off and the pipe will fill up.
Then if you carefully replace the bung and lift the pipe vertically it shoudl contain the water that has entered it.
tricky part will be replacing the bung without students getting wet and without losing your sample.
I used to wade into the water in big waders up to my armpit- wonder if a teacher could be in a row boat and reattach the bung at water level.. practice on dry land before hitting the water though..
OR - what if you used a pipe as above, but had a plastic hose going through the bung and down to the bottom of the pipe, then when you get to the depth you want use a suction pump to pump out some of the water.
my samples were sediment - so that was easier than liquid, though an awful lot more smelly - peeeeeeeeeeeeeeuuuuuuuuuuuuuuuuuuwww
Re: samples from the bottom of the pond
ah ha! that sounds like a good plan. As we have a bridge going over the lake, hopefully the students wont get wet.
thank you very much
thank you very much
Re: samples from the bottom of the pond
There are bottom, middle, top samplers available for sampling bulk storage tanks (think petrochemicals, previous life!). They are basically a stainless steel cylinder with a pull valve and shut off when full. Google "bottom tank sampler". You could try borrowing one or make your own...
