Zinc and iron speciation in polluted river courses

There is an a extensive interest for continuous monitoring of environmental poisons like heavy metals in natural water like river courses, seawater, and industrial process solutions and wastewater. This interest is reflected in public demands for environmental surveillance, and a more restricted framework concerning pollution. However, the challenge is to build low cost automatically apparatus sensitive enough to be useful for measurement of heavy metals in the field. Methods used today, including Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma - Mass Spectroscopy (ICP-MS), are not suitable for this purpose due to practically and economically reasons. This contribution presents a new low cost apparatus constructed to continuously monitor heavy metals in natural water, waste water or industrial process solutions. The apparatus uses anodic stripping voltammetry together with new sensor technology, using alloy electrodes. This apparatus combine high speed and sensitivity together with the possibility to monitor heavy metals continuously online in the field. Measurements were carried out at Leirelva, witch is an important river in Trondheim. The lower part of Leirelva river course is significantly influenced of human activity, and periodically is polluted with heavy metals. In this presentation the labile iron and zinc has been studied. Measurements were automatically carried out every thirty minutes for a period of three months. River water samples collected manually were analyzed with ICP-MS additionally. Samples collected for ICP-MS were filtered at 0.45 μm and added nitric acid to 0.6 M. The amount of iron and zinc found by ICP-MS represents the total amount of the metals, while the voltammetric measurements reflects the labile amount of iron and zinc. Preliminary results show a tendency that labile amount is about 1/3 of the total amount of zinc and iron. More results will be presented, and real time measurements over Internet will be demonstrated. The high stability, easiness of operation and maintenance makes this apparatus a very promising system for environmental surveillance.