Analysis of toxic aluminium species in natural waters

Aluminium is known to be toxic to a wide range of aquatic organisms under certain conditions. Monomeric hydroxy ions have been found to be primarily responsible for aluminium aquatic toxicity. A survey of aluminium toxicity and a brief discussion of speciation schemes are presented. The fast reaction of Al3+ with pyrocatechol violet (PCV) followed by spectrophotometric analysis is a frequently used method for aluminium speciation. By using a flow system, one obtains fairly exact and reproducible control of the reaction time, and as a result it provides a direct method of analysis for "free" aluminium (including inorganic monomeric aluminium). The PCV-method has been adapted for the determination of aluminium in carbonate-rich natural waters using an improved buffering system. Thus it is possible to monitor aluminium concentrations in lake water as well as in pore water of the sediments of eutrophicated hardwater lakes that has been treated with aluminium salts as a restoration measure.