BCR-580 - Total and methylmercury in estuarine sediment

Total and methylmercury in estuarine sediment

This certificate is valid until 4/2006; this validity may be extended as further evidence of stability becomes available.

The minimum sample intake is 250 mg.

Sediment samples were collected in 1994 in the Ravenna Lagoon at two locations, namely close to a petrochemical plant water discharge (high Hg Ievels) and downstream  (low contamination  levels). Two  batches each of ca.  250 kg were collected  from a boat, using a grab collecting  the 30/40 cm top sediment layer. The wet materials  were sieved to pass apertures of 2 mm and air-dried at 25°C in a drying chamber.  The moisture content was monitared during the drying process (measuring the dry mass content  as described  in section10);  when  a constant  maisture  content  was reached (3.5%), the materials were manually crushed and  sieved  again at 2 mm (the  fraction higher  than 2 mm  was discarded).  The resulting materials were stored  in polyethylene bags and transported at the Joint Research Centre of Ispra Italy). 


For the purpose of the interlaboratory study, it was decided to mix the two batches   to obtain a composite material with a Hg content lower than the candidate  CRM (with  high Hg Ievels) but still representative of a contaminated area: the composite sedimenl  material was prepared by mixing two parts or contaminated sediment with one part of low-level scdiment. The material was passed through a tungsten carbide-bladed hammermill and sieved to pass apertures  of 90 µm. The  < 90 µm fraction  was collected in a PVC mixing drum (filled with dry argon) and homogenized for 14 days at  about 48 rpm.  The bottling procedure was performed manually: a first series of 20 bottles was filled and immediately closed with screw caps and plastic inserts. Series  of 20 bottles were hence successively filled, alternating with re-mixing of the powder  for 2 minutes. All bottles  were stored at ambient temperaturein the dark. Araund 100  bottles  were prepared, each ontaining ca. 50 g (sample S 19). Thecandidate CRM raw  sediment containing high  Hg levels)  was considered to be representative of a material with a methyl mercury content corresponding to high anthropogenic  contamination  levels.  The homogenization and bottling procedures were identifical to  those used for  the sample S19 described above. Around 1100 bottles were prepared, each containing ca. 40 g (CRM  580).

consists of a sediment sample in a glass bottle containing about 40 g of powder