Use plastic tubes. The water samples must not have any contact with metals. Collect at least 10 ml of water.
Obtain the coordinates of the site of collection with a GPS, which can be done using a cell phone with GPS. If you have difficulty accessing the cell phone GPS you can open Google Maps/Google Earth and with the GPS on, as soon as the blue dot is on the right place, take a screenshot.
In case it is not possible to register the coordinates with a GPS, take notes from the location, such as “right margin of Rio Doce, under the bridge XX” and consider taking pictures of the site. It is very important to take pictures from the sample collection and send them to us.