Växters upptag av spårämnen från rödfyr : ett odlingsförsök vid tre rödfyrshögar i Västra Götalands län

Abstract: Burnt alun shale and lime is the residual product that was formed when alun shale was used as fuel to convert limestone to quick lime. The material contains arsenic, vanadium, molybdenum, cadmium, nickel, lead, and uranium among other elements. The aim of this paper is to examine the uptake of trace elements in vegetables grown on burnt alun shale and lime to determine whether or not the surrounding environment and humans are exposed to these elements by eating plant products. A cultivation trial was carried out where onion, carrot, and lettuce were grown on three mounds of burnt alun shale and lime in the Falköping area in Sweden. The treatments were burnt alun shale and lime mixed with peat, only burnt alun shale and lime, and a reference soil. The reference plots were natural soil mixed with peat adjacent to the mounds. After harvest the vegetables were dried and weighed in order to determine the growth. Growth medium samples were analyzed for the plant available fraction of arsenic, vanadium, molybdenum, cadmium, nickel, and lead. Plant samples were analyzed for the total content of the above-mentioned trace elements. Particle size distribution, organic matter content and pH was also determined for the growth medium samples. The growth of the vegetables was, as expected, higher with the treatment with burnt alun shale and lime mixed with peat compared to the treatment with only burnt alun shale and lime. The treatment with only burnt alun shale and lime gives higher concentrations of trace elements in the vegetables, than the treatment with burnt alun shale and lime mixed with peat. There is a positive correlation between the concentration of NH4NO3- extractable arsenic, vanadium, molybdenum, and cadmium in the growth medium and the concentration in the vegetables. The correlation between the concentration of NH4NO3- extractable nickel and lead in the growth medium and the concentration in the vegetables is on the other hand slightly negative. Lettuce is the vegetable that generally contained the highest concentrations of trace elements compared to onion and carrot. No conclusions could be drawn on whether the pH had any effect on the contents of trace elements in the growth medium or the uptake in the vegetables. Nor has the particle size distribution or the organic matter content had any visible effect on the content of trace elements in the growth medium or in the vegetables. The quantity of molybdenum in carrot on one square meter cultivation area at the trial site Rörsberga exceeds the limit value for human daily intake. This is the only exceeded value for carrot and for onion no value on quantity exceeded the limit values. For lettuce on one square meter cultivation area at Rörsberga, the limit value is exceeded for the quantity of arsenic, vanadium, molybdenum, and cadmium. At the trial site Tomten the quantity of vanadium exceeds the limit value and on the reference plot at Uddagården the quantity of vanadium and cadmium exceeds the recommended limit value. These quantities do not imply any acute health risk for humans since quite large amounts of vegetables are needed in order to reach the limit values.