COMPARISON OF SEDIMENT PORE-WATER SAMPLING FOR SPECIFIC PARAMETERS USING 2 TECHNIQUES

The suitability of the two more extensively used sampling techniques, namely in-situ dialysis and centrifugation followed by filtration were compared. Field measurements derived from Lake Simbirizzi, Sardegna, Italy were used for the comparison. Two groups of substances were sele cted; the first one consists of the relatively inert in the aquatic en vironment chlorides and bromides, while the second one consists of sub stances involved in diagenetic processes (ammonium-nitrogen and solubl e reactive phosphorus). The field measurements show that for the appli ed sampling techniques the measurements are comparable for the first g roup of substances, while measurements derived by centrifugation follo wed by filtration give considerably different concentrations using ins itu dialysis for the second group of substances. Since the second grou p is related to sediment-water interactions (adsorption-desorption and chemical processes), it seems that forced separation by centrifugatio n influences considerably the derived measurements. As a result in-sit u dialysis is expected to give more accurate measurements of porewater concentrations for nutrients and other reactive substances.