Inorganic Characteristics of Surface Sediment from Lake Baikal: Natural Elemental Composition, Redox Condition, and Pb Contamination

Abstract

Fourteen short sediment cores (ca. 30 cm in length) from Lake Baikal were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) for Al, Ca, Co, Cr, Cu, Fe, Mg, Mn, Ni, Zn, As, Ti, V, P, S, Sr, Ba, Pb, Sc, and Y. The concentrations were comparable to those in remote unpolluted lakes in Europe and Canada. Most elements were classified into two major groups on the basis of their vertical distribution characters (Mn·Fe-oxide-philic, Fe, Mn, As, P, and Ba; terrigenous, Al, Ca, Mg, Ti, Co, Cr, Ni, Zn, V, Sr, and Sc), whereas S, Pb, Y, and Cu showed their own unique profiles. Concentrations of Cu correlated well with those of biogenic SiO2 (r= 0.856), indicating the participation of diatoms in the deposition of Cu. Mn-, Fe-, and S-rich layers occurred in the same order (Mn above Fe above S) in all cores, indicating the oxidized condition of surface sediment. The oxidized layers were thin in the central basin and thick at Academician Ridge; the thickness correlated negatively with grain density (r = −0.922) and positively with the content of biogenic SiO2 in the sediment. At Academician Ridge, abundant fossil diatoms may have increased the porosity of the sediment, accelerating the penetration of oxygen into the sediment. Depth profiles of Pb/Al showed distinct enrichment (pollution) of Pb in the surface sediment. The pollution began in the 1900s and became significant after ca. 1950. The pollution level (3.2–17.3, av. 13.5μg/cm2) was considerably lower than those in remote unpolluted lakes in Europe and Canada. It was higher in the southern basin and lower in the northern basin and at Academician Ridge. The total inventory of excess Pb in the lake was calculated at 4240 t.