Determination of the background ranges of trace metals in the brown alga Sargassum pallidum from the Northwestern Sea of Japan

The background concentrations of Fe, Mn, Zn, Cu, Pb, Cd, and Ni were calculated in samples of the brown algae Sargassum pallidum from the northwest of the Sea of Japan for the 1995?C2008 period. We found 60?C672 ??g/g of dry mass for Fe, 12?C455 for Mn, 6.2?C23.8 for Zn 0.9?C3.9 for Cu, 0?C5.5 for Pb, 0.5?C1.7 for Cd, and 0.4?C3.8 for Ni. The median plus double median of the absolute deviations from the median (Me + 2MAD) was used as the upper threshold of background metal concentrations. The lower threshold for the background data, which coincides with the physiologically necessary quantity of an element, was the median of 15% of the minimum values of the sample minus the double median of the absolute deviations of the median (Me₁₅ ?? 2MAD₁₅). The Me₁₅ ± 2MAD₁₅ range was regarded as the natural background data.