Marine Water Sampling

[Randunu Dimeshan]

Hello divers. We run a diving center in south coast, Sri Lanka. We've been doing ocean conservation programs for quite some time. Recently we were approached by a company to sponsor us for seawater sampling equipment. raw data like PH, Salinity, Dissolved Oxygen, Temperature and turbidity . Would like to know of your ideas about any suitable portable equipment so we can provide them a report. Thank you.

email me at randunu1483@gmail.com if you have further suggestions. Thank you.

 

[Seaweed Doc]

I've used equipment by Yellow Springs Instruments (YSI) and Lachat Instruments in the USA. I'm not sure what they've got available now. Of the two companies, I prefer YSI. I don't know what's available to you.

Two thoughts:

1. Turbidity readings are notoriously problematic. Perhaps less so if you are taking one-time measurements. They're more unreliable if you leave the equipment recording for any period of time.

2. On oxygen, use the optical sensors, not the old-fashioned KCl-filled, membrane-covered sensors. They are much easier to work with.

3. There's some highly specific requirements these days if you want to use your pH data for ocean acidification studies. The topic is so political, that only the most expensive sensors are deemed to be "good enough." On the other hand, you can get reasonably reliable data from less expensive equipment.

 

[Randunu Dimeshan]

So what do you think, should we stick to temperature probes,Salinity, and DO? maybe ask for a decent PH tester. what else can we measure without having much problems? We just want to help out as we can

one supplier reached out and offered this one
Multiparameter Water Quality Meter - HI98194 - Hanna Instruments

is it reliable?

 

[sea_ledford]

That looks to be a very inexpensive model. Can't say if that is good or bad, just inexpensive. I have used sondes ranging in price from about $6k to $20K for work. Something that doesn't really matter what the initial cost is the replacement probes (pH has to be replaced annually) and calibration solutions.

We were looking at conductivity (salinity), temperature, depth, dissolved oxygen, ph, and turbidity. We had to have 2 solutions for both pH and conductivity (high and low for each), DO can be done with distilled water, but the turbidity was a killer. pH and conductivity solutions were ordered in 5 gallon amounts, cost was about $80 each (we could pick up locally) and had to be replaced every year, regardless of how much was used. Turbidity came in 1 quart size and was $250 for one that was good for 2 WEEKS, or $340/quart that was good for 6 months.

Unless you can pick up locally, shipping your calibration solutions will be more expensive than your sonde. Mixing dry solutions would be much more affordable, but more difficult and depending on the use of the data, potentially problematic to the point of making the data useless.

You can get an idea of prices (at least in the US) here:
Reagents, Membranes and Calibration Solutions for Water Analysis

-Chris

 

[Randunu Dimeshan]

That looks to be a very inexpensive model. Can't say if that is good or bad, just inexpensive. I have used sondes ranging in price from about $6k to $20K for work. Something that doesn't really matter what the initial cost is the replacement probes (pH has to be replaced annually) and calibration solutions.

We were looking at conductivity (salinity), temperature, depth, dissolved oxygen, ph, and turbidity. We had to have 2 solutions for both pH and conductivity (high and low for each), DO can be done with distilled water, but the turbidity was a killer. pH and conductivity solutions were ordered in 5 gallon amounts, cost was about $80 each (we could pick up locally) and had to be replaced every year, regardless of how much was used. Turbidity came in 1 quart size and was $250 for one that was good for 2 WEEKS, or $340/quart that was good for 6 months.

Unless you can pick up locally, shipping your calibration solutions will be more expensive than your sonde. Mixing dry solutions would be much more affordable, but more difficult and depending on the use of the data, potentially problematic to the point of making the data useless.

You can get an idea of prices (at least in the US) here:
Reagents, Membranes and Calibration Solutions for Water Analysis

-Chris

Thanks Chris. Really helpful, I was actually searching for local suppliers when it comes to buying the calib solutions. So far nothing except one place that referred me to the unit I showed. kindly expensive however. have a little margin on top of the median US prices . Buying them from overseas will be a nightmare tbh.