Choice of sampling location

During the field campaigns performed to setup the stations, the sampling feasibility was tested at each gauge station, especially:

• to ensure access to the sampling place;

• to have a clean place to perform the filtrations;

• to train someone responsible.

Equipment made available to the observer

Each operator received the equipment needed to sample during a whole year and a document with instructions for sampling and filtration, in Spanish or Portuguese language. The equipment consists of:

• a manual vacuum pump;

• a water proof thermometer – conductivity meter;

• a 1-litre sampling bottle made of HDPE;

• 12 filtration kits with : 1 disposable sterilized filtration set with 0.2 µm cellulose acetate filter;

• one 125 ml bottle made of HDPE for the major elements;

• one 60 ml bottle made of brown glass for the COD;

• one 125 ml bottle made of HDPE for the trace elements;

• aluminum film to package the DOC bottles;

• adhesive tape to protect the labels and seal the bottles;

• a cooler to keep the samples and the equipment;

• 100 l trash bags to unfold on the worktop in order to insure the cleanliness.

• the printed sampling protocol.

Sampling

The sampling equipment must have been prepared at GET-Toulouse according to the following procedure:

• sampling bottles for the major elements: HNO3 2N bath during 48h, milli-Q water bath during 48 h, dry in a laminar flow hood;

• flacons pour COD: 2h au four à 530°C;

• trace elements bottles: aqua regia on each face and the bottom during 2 h, HNO3 2N N bath during 48h, milli-Q water bath during 48 h, dry in a laminar flow hood;

• Inside the trace element bottles, 200 µL of supra pure HNO3 are added and in the DOC bottles, 150 µL of supra pure H3PO4 are added.

The set filtration filters are first weighted and the weight is reported on a label sticked on the protection bag which is then hermetically closed. All the bottles are labeled with the station name and their future use and placed in plastic bags closed by a zipper.

The filtered sample, as the filters, are kept by the operators in insulating compartments in order to prevent them from temperature variation, dust and light. They are regularly sent to Brasília, either through field campaigns opportunity or by mail.

Special filtrations for the POC are operated since april 2006 in 6 Brazil located stations: Óbidos , Itaituba, Borba, Manacapuru, Caracarai and Serrinha. To do that, special equipment (filtration sets with GFF filters first pyrolyzed at 480° C) is provided to the operators in order to perform a specific filtration of 300 ml for the DOC.