Rachold: Major. Trace and Rare Earth Element Geochemistry
203
Total SPM concentrations were estimated from the weight difference between the original and
the sediment-loaded filters after freeze-drying. Acid digestions of the sediment loaded filters
were performed in PTFE vessels using ultrapure HN03, HCl04, and HF (Heinrichs and
Herrmann, 1990). The residues were redissolved in HN03 and diluted with H20 to a final
volume of 20 to 50 ml depending on the sediment load. AI, Ti, Fe, Mn, Mg, Ca, Na, K, Ba,
and Sr were analyzed by ICP-OES (Perkin Elmer Optima 3000 XL), Bi, Cd, Co, Cs, Cu, Ga,
Hf, Li, Mo, Nb, Ni, Pb, Sb, Sn, Ta, Th, TI, U, Y, W, Y, Zn, Zr, and rare earth elements
(REE) by ICP-MS (Fisons Plasma Quad), and As by GF-AAS (Perkin Elmer SIMAA 6000).
Accuracy of the analytical methods was checked by parallel analysis of an international standard
reference material (MESS-I, BCSS-I, PACS-I, GSD-7, GSD-9, GSD-I0) for every method.
The analytical precision was better than 5 % for major elements and better than 10 % for trace
and rare earth elements.
Earlier studies demonstrated that heavy rare earth elements (HREE) that are commonly carried
by zircon and other heavy minerals can remain in resistant phases during HF-HCI04 dissolution
(c.f. Condie, 1991). Within the present study, international reference material was analyzed for
Zr concentrations in order to quantify the amount of resistant phase present. The observed Zr
concentrations amounted to 70 % of the certified values at minimum, indicating that up to 30 %
of the zircon was not dissolved during HF-HCI04-digestion. However, further investigations
indicated that the amount of resistant phase strongly depended on both digestion time and grainsize of the sample. Zr concentrations in standard reference material which was pulverized to <
35 /lm or treated with HF-HCl04 for up to 48 hours yielded 80-90 % of the certified values.
The SPM analyzed within the present study consists mainly of fine-grained material < 6 /lm
(see below). Therefore, a significant deficit in Zr and REE concentrations resulting from
incomplete dissolution can be ruled out.
Some samples showed extraordinarily high As, Cd, Cu, Sn, Pb, and Zn concentrations
which could not be explained by natural processes or anthropogenic pollution and these high
values were attributed to contamination from the ship. All data where the concentrations of the
aforementioned elements were more than 2-times higher than the normal values were
eliminated.
Six selected SPM samples were analyzed for grain-size distribution by laser-granulometry.
The mineralogical composition of these samples was semi-quantitatively analyzed from smearslides of the total SPM by x-ray diffraction (XRD). In addition, the clay mineral distribution
was studied in the fraction < 6.3 /lm by x-ray diffraction after Atterberg grain-size separation
(Gibbs, 1965).
Results and discussion
Table I presents the average chemical composition of SPM of the Lena, Yana, and Khatanga
and their major tributaries. The labels of the tributaries are indicated in the location map (Figure
2) and in the other figures. The minerals identified in the SPM from XRD are listed in Table 2.
In the following section the composition of the SPM from each river will be discussed
separately.
Lena SPM
The Lena exhibited total SPM concentrations of 6 to 77 mg/!, with an average of 28 mg/1. In
general, Lena SPM was characterized by high amounts of fine-grained material although some
variations within the river could be observed. The grain-size distribution of two stations is
illustrated in the upper left comer of Figure 3. The major fraction of the SPM consisted of
quartz. feldspars (K-feldspars and plagioclase), and muscovite-type illite. Amphibole and illite-
203
Total SPM concentrations were estimated from the weight difference between the original and
the sediment-loaded filters after freeze-drying. Acid digestions of the sediment loaded filters
were performed in PTFE vessels using ultrapure HN03, HCl04, and HF (Heinrichs and
Herrmann, 1990). The residues were redissolved in HN03 and diluted with H20 to a final
volume of 20 to 50 ml depending on the sediment load. AI, Ti, Fe, Mn, Mg, Ca, Na, K, Ba,
and Sr were analyzed by ICP-OES (Perkin Elmer Optima 3000 XL), Bi, Cd, Co, Cs, Cu, Ga,
Hf, Li, Mo, Nb, Ni, Pb, Sb, Sn, Ta, Th, TI, U, Y, W, Y, Zn, Zr, and rare earth elements
(REE) by ICP-MS (Fisons Plasma Quad), and As by GF-AAS (Perkin Elmer SIMAA 6000).
Accuracy of the analytical methods was checked by parallel analysis of an international standard
reference material (MESS-I, BCSS-I, PACS-I, GSD-7, GSD-9, GSD-I0) for every method.
The analytical precision was better than 5 % for major elements and better than 10 % for trace
and rare earth elements.
Earlier studies demonstrated that heavy rare earth elements (HREE) that are commonly carried
by zircon and other heavy minerals can remain in resistant phases during HF-HCI04 dissolution
(c.f. Condie, 1991). Within the present study, international reference material was analyzed for
Zr concentrations in order to quantify the amount of resistant phase present. The observed Zr
concentrations amounted to 70 % of the certified values at minimum, indicating that up to 30 %
of the zircon was not dissolved during HF-HCI04-digestion. However, further investigations
indicated that the amount of resistant phase strongly depended on both digestion time and grainsize of the sample. Zr concentrations in standard reference material which was pulverized to <
35 /lm or treated with HF-HCl04 for up to 48 hours yielded 80-90 % of the certified values.
The SPM analyzed within the present study consists mainly of fine-grained material < 6 /lm
(see below). Therefore, a significant deficit in Zr and REE concentrations resulting from
incomplete dissolution can be ruled out.
Some samples showed extraordinarily high As, Cd, Cu, Sn, Pb, and Zn concentrations
which could not be explained by natural processes or anthropogenic pollution and these high
values were attributed to contamination from the ship. All data where the concentrations of the
aforementioned elements were more than 2-times higher than the normal values were
eliminated.
Six selected SPM samples were analyzed for grain-size distribution by laser-granulometry.
The mineralogical composition of these samples was semi-quantitatively analyzed from smearslides of the total SPM by x-ray diffraction (XRD). In addition, the clay mineral distribution
was studied in the fraction < 6.3 /lm by x-ray diffraction after Atterberg grain-size separation
(Gibbs, 1965).
Results and discussion
Table I presents the average chemical composition of SPM of the Lena, Yana, and Khatanga
and their major tributaries. The labels of the tributaries are indicated in the location map (Figure
2) and in the other figures. The minerals identified in the SPM from XRD are listed in Table 2.
In the following section the composition of the SPM from each river will be discussed
separately.
Lena SPM
The Lena exhibited total SPM concentrations of 6 to 77 mg/!, with an average of 28 mg/1. In
general, Lena SPM was characterized by high amounts of fine-grained material although some
variations within the river could be observed. The grain-size distribution of two stations is
illustrated in the upper left comer of Figure 3. The major fraction of the SPM consisted of
quartz. feldspars (K-feldspars and plagioclase), and muscovite-type illite. Amphibole and illite-