Environmental impact of ferrochrome slag in road construction

Vargon Alloys in Western Sweden is one of the largest producers of ferrochr ome slag in Europe. Ferrochrome slag is a by-product from the production of ferrochrome, an essential component in stainless steel. Extensive tests ha ve been carried out on the physical properties of the ferrochrome slag from Vargon Alloys and it was found to be highly suitable as road construction material. The composition and leaching tests of the ferrochrome slag show t hat the chromium content is high, 1-3%, although leaching under normal cond itions is very low. With the exception of potassium (K), which had a potent ial leaching capacity (availability test) of around 16%, the leaching of ch romium, nickel, zinc and other elements was just a few per cent. However, a ll these tests were conducted in the laboratory. What happens out in the fi eld, under the influence of acid rain and biological activity, and how does this compare with the laboratory results? To answer this question an inves tigation was carried out to study the environmental impact of ferrochrome s lag in roads that were built in 1994. The investigation includes soil sampl ing (total content and leachable amounts of metals) and groundwater analysi s (filtered and non-filtered samples). In addition, a new method involving the bio-uptake of chromium and other metals by the roots of the dandelion ( Taraxacum officinale) was tested. The results show that there was a low mig ration of particles from the slag to the underlying soil and that the leach ing into the groundwater was also low for all the elements analysed. Howeve r, there seemed to be a significant uptake of Cr by plants growing with the ir roots in the slag. An investigation of plant uptake was an important com plement to laboratory leaching tests on alternative materials. (C) 2001 Els evier Science Ltd. All rights reserved.