You can look at the ICP Forest protocols

http://icp-forests.net/page/icp-forests-manual

There is one on sampling and analysis of deposition. I hope it can be useful for you

Stefano

Rain Gauge is used .

Some where automatic system is used to get Rainfall.

On spot Measurement of pH

Hi Sara,

Primarily, many municipalities and/or states do not allow the collection of rainwater; one must follow the guides relating to your local mosquito commission and/or the bylaws written regarding the proper collection and storage of water.

Checking the pH levels are as simple as using the proper kit purchased through your local pool supply store/ warehouse; you want one that accomplishes your specific needs since pH kits vary drastically. 

Remember, storing water in metal drums can and will change different water quality levels, which will effect pH quality levels well beyond repair. AVOID SUNLIGHT and/or other types of light at all costs; bacterium, fungi, and any number of unwanted results will mess with your desired protocols. Providing light cannot infuse the water and measured quantities of debris that have the opportunity to enter the system (such as rain barrel storage), properly fitted lids to block light and avoid evaporation by use of a P trap intake.

When water is properly covered, it will not go bad; it may lose chlorine and some other undesirable additives collected via air, through evaporation during the hydrological system functions such as salt or acidity levels, perhaps even some hydrogen molecules/ions.

This experiment should always produce roughly the same results with pH levels between 5 & 9; lest your samples are taken rather close to coal or fossil burning power plants - you may have results closer to between 3 or 4 rather the safer numbers around 7 on the pH scale.

One side note: if you capture rainwater in a rain barrel, you are losing a great opportunity to generate electricity by reducing exit pipes from 2" to 1.5" to 1" before it passes a water generator.

Peace, Albert Amorino

Rain water can be collected in broad mouth beaker by putting a funnel on its mouth. Rest you can design for e.g., if you keep a filter paper Whatman no. 40 inside the funnel, it can stop the impurity to mix with the collected water. you can also collect the daily dust load with same setup. pH should be measured without any delay meaning 10 ml collected water is sufficient for single reading repeat the same for multiple reading to get an average value. This is the most simplest way in my opinion. 

Thanks  dear coleagues.

You help me a lot!

Dear Sara    you may  interested to measure elments concentration in rainwater you should be care of contamination.Simply by puting a funel in to preacid washed glass ware such as beaker or erlen and collect rainwater .You may centrifuge it first and do your experiment.Filter paper may already contaminated with metals and make your analysis more difficult.