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Aluminium contamination of acid soil solution isolated by means of porcelain suction cups: a reply to a paper by Hughes & Reynolds (1990) and an interpretation of aluminium release
Author(s) -
RAULUNDRASMUSSEN K.
Publication year - 1991
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1991.tb00408.x
Subject(s) - aluminium , dissolution , contamination , chemistry , suction , metallurgy , ion exchange resin , mineralogy , materials science , inorganic chemistry , mechanical engineering , ecology , engineering , biology
SUMMARY Possible aluminium contamination of acid soil solutions isolated by use of porous porcelain suction cups (‘P.80 type’) was reported by Raulund‐Rasmussen (1989). The aluminium release was explained by a proton‐induced dissolution of cup material. Hughes & Reynolds (1990) suggested that the aluminium release and proton consumption could be explained by an ion‐exchange reaction. In an attempt to understand the mechanism and thereby also the usefulness of suction cups, laboratory experiments were carried out to define mineralogical and chemical composition, stability under acid conditions, cation exchange capacity, and reactivity under conditions relevant to the field. The cups consisted of mullite and corundum (65% Al 2 O 3 ) as shown by X‐ray diffraction analysis. The cation exchange capacity of the cups was too low (0.65 μmol c per cup) to explain the observed contamination of isolated soil solution. Ground cup material dissolved slowly in acid. Investigations on whole cups showed that aluminium release to acid test solutions depended on the time of exposure. It is concluded that porcelain suction cups may lead to contamination of isolated soil solution depending on: (i) the intake rate, (ii) the rinsing procedure before sampling, and (iii) the composition of the soil solution (pH and aluminium ion activity being important parameters).