Lake Powell: Water Quality Samples at a Specific Depth

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Detailed Description

Collection of water quality samples from specific depths for inorganic elements in Lake Powell, AZ-UT.


Image Dimensions: 1920 x 1080

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Location Taken: US


Bob Hart: 
Now this is a Sea Bird Electronics, it measures multiply water quality parameters. So per-churno we will lower that through the water column at a constant rate and it will collect data as it falls through the water, and so it'll store all the information in the Sea Bird, and then we'll download it to the laptop which is on the boat. Then using that information we decide where we are going to collect water quality samples. 
Ron Antweiler: 
The idea is to collect a sample at a certain specific depth, a water quality sample. And so we lower it two that depth, whether its 2 meters or whatever. The bottle has got this cork in it and the cork is attached by the fishing line to this fishing pole that you see here. So when we get to the depth that we want to be at, we give a yank on the fishing pole and that pulls the cork out and the bottle starts to fill. The fishing pole here is just used to reel in the cork. Now we wait until the air bubbles appear here on the surface, because that tells us that the water bottle is filling and when we see that the air bubbles have stopped coming up it means that the bottle is full. So then we draw it out and we have our sample which was collected at that specific depth of the lake, so then we can do our water quality measurements for the water at that depth. 
Well the first thing that's going to happen here is pH and conductivity; it needs to be done as soon as the sample it collected or as soon as is feasible after collecting the sample.  pH and water temperature both change with time, so therefore they need to be made as soon as possible.  
Chris Smith: 
So why do you filter the water? 
Dave Roth:
We filter the water to remove the particulates, if we didn't do that the particulates would dominate the chemistry of the water and we wouldn't really know what's dissolved in the water. 
Ron Antweiler: 
The metal samples need to be preserved with nitric acid, and so all of the samples will get four doses or about 2ml. The two metal samples are now preserved and ready for analysis, and the second is mercury, now mercury is a concentrated solution of nitric acid and potassium dichromate, and mercury being volatile you need to fix it. Once a mercury sample has been dosed in this way it is stable for a long time, meaning months.
The samples are filtered. After they're filtered we're sampling, this particular sampling is for all the inorganic elements that you can think of. We actually analyze for pretty close to sixty different elements and not all of them are above detection and not all of them are of importance for human health, but there are a number of them. Luckily the values need to be pretty low on Lake Powell.