To Örebro University

Metals are essential nutrients for plant health, but not all metals are necessary and can sometimes be harmful towards plants depending on factors such as species, elemental composition in the soil and concentration of a metal. Iron (Fe), which is one of the most abundant metals in the earth’s crust is also one the most important nutrients for plant growth, as it is responsible for metabolism. Lead (Pb) has been widely outspoken to be a harmful pollutant to plants and has been shown in studies to have an impact on a plant’s physiology and morphology. The aim of this study is to analyze whether Pb and Fe influence the metal content of Garden cress (Lepidium sativum). A solution of Pb with the following concentrations; 2.4 g/L, 1.2 g/L, 0.48 g/L, 0.24 g/L, 0.12 g/L, 0.048 g/L and 0.024 g/L were used. Another solution of Fe with the following concentrations; 0.56 g/L, 0.28 g/L, 0.11 g/L, 0.056 g/L, 0.028 g/L, 0.011 g/L and 0.0056 g/L were also used. Then a combined solution of both Pb- and Fe solution were mixed with a volume ratio of 1:1 corresponding to the following concentrations of lead and iron, respectively; 0.024/0.0056 g/L, 0.048/0.0112 g/L, 0.12/0.028 g/L, 0.24/0.056 g/L, 0.48/0.112 g/L, 1.2/0.28 g/L were used. A total of 29 different metal contents were analyzed, which include; Aluminum (Al), silver (Ag), Barium (Ba), Beryllium (Be), Bismuth (Bi), Cadmium (Cd), Cobalt (Co), Copper (Cu), Fe, gallium (Ga), potassium (K), lithium (Li), magnesium (Mg), manganese (Mn), Molybdenum (Mo), sodium (Na), nickel (Ni), Pb, rubidium (Rb), selenium (Se), strontium (Sr), tellurium (Te), thallium (Tl), uranium (U), vanadium (V), zinc (Zn). Before initial analysis, microwave plasma atomic emission spectrometry (MP-AES) was applied with a test sample to evaluate if the acidified digestion method used with nitric acid and hydrogen peroxide was successful enough to be used for the original experiment. It was successful, so the cress samples underwent the same digestion method and were analyzed with inductive coupled plasma mass spectrometry (ICP-MS). The results showed that Pb overall decreased most metal contents, while Fe seemed to generally maintain a constant metal content of most metals. Fe fed cress seemed to grow the healthiest in appearance compared to Pb fed cress which grew the worst. Mixed solution Pb and Fe cress fed grew worse than Fe fed cress, but better than Pb fed cress. The growth quality was the worst with Pb fed and the best for controlled water fed cress. For mixed Pb and Fe solution fed cress the plants seemed to share similar qualities of both Pb- and Fe solution fed cress, with better growth capabilities than Pb fed cress, but worse than Fe fed cress. The high dilution factor during the sample preparation led to the fact that some trace and ultra-trace elements could not be determined, since their contents were below LOD or LOQ. Adapting the sample preparation procedure to these low concentrations would be a further improvement.