ИСТИНА

We developed a long (700-year) dataset for the concentrations of microelements in tree rings of larch from Taymir peninsula, the northernmost region (ca.74°N) in the world where trees grow. Each analyzed sample usually consisted of 10 consecutive tree rings but occasionally 5 tree rings, so that over 70 samples were analyzed using solution ICP-MS to span 700 years in one sequence. Wood samples (ca. 100 mg) were digested with concentrated HNO3 for measurement of Li, B, Na, Mg, Al, Si, P, Cl, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, I, Ba, La, Ce, Nd, W, Au, Pb, Bi, Th, and U. This is the longest tree-ring microelement record ever reported, containing 40 microelements measured simultaneously. For robustness, 14 microelements with extremely low concentrations at the part per trillion level were eliminated from consideration. The cluster analysis binned the 26 remaining elements into four distinct clusters: (1) Zr, Cd, Cr, Fe, Sn, Pb; (2) Li, Ag, I, Cr, B, Na, Al, Ni, Cu, Zn; (3) Si, Cl, Bi, P; and (4) Mn, Rb, Mg, K, Ca, Sr, Ba. The 20th century stands out in the 700-year record for many microelements, perhaps because of the transfer of atmospheric pollution from Europe to the Arctic Russia and the change in temperature/precipitation regime for this region. Our conclusions are tempered by current limitations in understanding of supply, uptake, and immobilization processes for microelements in tree rings.