Jahn, R.

Meijer, E.L.

Tanneberg, H.

English

NARCIS 

Sorption (kinetic and capacity) and desorption of trace elements in volcanic soils of Italy and the Azores

Name not available

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VOLCANIC SOILS: Properties, Processes and Land Use - International Workshop 
Sorption (kinetic and capacity) and desorption of trace elements in volcanic 
soils of Italy and the Azores 
Hartmut Tanneberg, Reinhold Jahn, Edward L. Meijer & Markos Kleber 
Inst, of Soil Science & Plant Nutrition, Univ. of Halle, Germany; Phone; -H-345-55 22530, 
Fax: ++345-55 27116, email: jahn@iandw.uni-halle.de 
Introduction. Andosols have a high binding capacity for heavy metals which may be 
naturally accumulated or anthropogenically derived. These metals are bound in mineral 
structures, on mineral surfaces, and complexed by organic matter. Some trace elements may 
be so strongly bound that they become unavailable to plants. But in this respect, information 
is very scarce, but extremely important for improved environmental protection (COST Report 
2000). Beside the formation of organic complexes, "many trace metals form surface 
complexes with aluminol and silanol groups as evidenced by extensive studies on silica and 
Al-oxides; however, few studies have been performed on allophane and imogolite" (Clark & 
Mc Bride 1984). The dominance of variable charge sites in Andosols has driven us to study 
the pH-depended sorption and desorption of trace elements. 
Materials. Horizons of COST- profiles of Italy and the Azores have been selected in order of 
distinct differences of contents in organic matter and short range ordered minerals (see Tab. 
1). For comparison an Ap-horizon without short range ordered minerals of a Chernozem 
(Germany) is also included in the study. 
Tab. 1 : Selected data of the investigated soil samples (COST-data) 
Soil 
Nl Italy 
Nl Italy 
N3 Italy 
N3 Italy 
N3 Italy 
N6 Azores 
N6 Azores 
Depth 
cm 
0-16 
54-95 
0-22 
48-70 
98-125 
0-20 
40-60 
N6 Azores 100-120 
Chernozem 0-24 
Hor. 
Ap 
Bw2 
Al 
AB 
Bw2 
Ah 
2AB 
2Bw3 
Ap 
Clay 
% 
10 
9 
16 
14 
12 
39 
32 
29 
21 
Sût 
% 
63 
62 
58 
66 
56 
61 
68 
71 
68 
Sand 
% 
27 
29 
26 
20 
32 
0 
0 
0 
11 
pH 
KCl 
4,7 
5,2 
4,9 
5,4 
5,5 
4,6 
5,4 
5,7 
7,5 
Corg 
% 
2,7 
0,7 
6,7 
2,1 
0,6 
19,1 
11,0 
4,5 
2,0 
CEC 
cmoVkg 
27,3 
21,8 
33,5 
20,9 
13,5 
73,7 
67,0 
59,4 
21,5 
Fed 
; % 
0,5 
0,6 
1,0 
U 
0,8 
0,0 
0,0 
0,0 
0,6 
Al« 
% 
0,3 
0,3 
2,9 
4,1 
3,1 
6,0 
9,3 
10,8 
0,0 
Fe0 
% 
0,2 
0,2 
0,6 
0,6 
0,4 
2,9 
4a 
3,3 
0,1 
Sio 
% 
0,1 
0,1 
1,1 
1,9 
1,9 
0,9 
2,1 
3,6 
0,0 
Methods. Batch experiments (according to OECD-Guideline 106) have been carried out to 
establish sorption- and desorption-isothermes of the trace elements Cu, Cd, Pb, Cr and Ni at 
pH-levels relevant to Andosols (pH 4 to 7). (1) Time-Dependence of trace element sorption: 
Field-moist samples equivalent to 2 g dry (105°C) soil were shaken (2 days; room 
temperature and ambient pH) in 50 mL of [5 mmol TE(N03 ) + 10 mmol Ca(N03)2] L"1 
solution. After 10, 20, 40, 80, 160, 320 minutes and 10, 22, 48 hours shaking, the samples 
were centrifuged and 0.5 mL of the supernatant removed to measure the trace elements. 
(2) pH-Dependence of trace element sorption-isotherms: Field-moist samples equivalent to 2 
g dry (105°C) soil were prepared in three treatments (i) equilibrated to pH 4 (with HN03 and 
NaOH), (ii) ambient pH, (iii) equilibrated to pH 7 (with HNO3 and NaOH). Each treatment 
was shaken (2 days) in 10 mL of [1, 5, 10, 100, 300, 1000, 2000 mg elements-L"1 TE(N03) + 
58 
VOLCANIC SOILS: Properties, Processes and Land Use - International Workshop 
10 mmol Ca(N03)2] L"1 solution (room temperature). For the pH 4-treatment, additionally the 
solution was adjusted to pH 4. Elements were measured after centrifiiging and filtering. 
(3) pH-Dependence of trace element desorption-isotherms: Loaded samples from (2) were 
shaken 10 consecutive time in 20 mL 10 mmol Ca(N03>2] L"1 for 2 days each . elements were 
measured after centrifiiging and filtering. 
The elements have been measured by means of AAS and ICP 
Results. From the sorption kinetics it can be concluded that in all samples the sorption of 
trace elements is governed by ion association, ion exchange and rapid sorption (Sparks, 2000) 
within a few hours. AB. samples have a very high sorption capacity. Without any exception no 
clear maximum of sorption was reached up to a maximum concentration of 2000 mg L"1 in the 
solution. The pH-depence of sorption is most prominent for Cd and Ni. It is to notice that 
especially the allophane rich subsoils from N6 Azores and N3 Italy have around pH 4 
sorption isothermes for Cd and Ni at distinct lower levels than at soil pH or around pH 7. The 
sorption of Cr and Pb are only less affected by pH changes. 
Literature Cited. 
Clark & Mc Bride 1984: Chemisorprtion of Cu(H) and Co(II) on allophane and imogolite. 
Clays Clay Miner. 32: 300-310 
OECD 1981: OECD-Guideline for testing of chemicals 106: Adsorptbn/Desorption: 1-23. 
Sparks D. 2000: New frontiers in elucidating the kinetics and mechanisms of metal and 
oxyanion sorption at the soil mineral/water interface. J. Plant Nutr. Soil Sei. 163: 
563-570. 
59 


Sorption (kinetic and capacity) and desorption of trace elements in volcanic soils of Italy and the Azores

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