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Impact of parent rock and topography aspect on the distribution of soil trace metals in natural ecosystems
Rezapour, S.; Golmohammad, H. & Ramezanpour, H.
Abstract
The concentration and dynamic of soil trace
metals in natural ecosystems, in particularly, is dependent
on the lithology of parent rock as well as topography and
geopedological processes. To ascertain more knowledge
for this dependency, soils on three parent rocks involving
peridotite, pegmatite, and dolerite in two contrasting
topography aspects were investigated. The total values of
Fe, Mn, Zn, Cu, and Ni were determined and compared for
different soil pedons. The concentration of Fe, Mn, and Ni
were highest in soils developed from peridotite (127,
1.8 g kg-1, and 218 mg kg-1, respectively), intermediate
in soils derived from dolerite (81, 1.3 g kg-1, and
166 mg kg-1, respectively), and least in soil developed
from pegmatite (50, 0.23 g kg-1, and 20 mg kg-1,
respectively). The values of Zn and Cu, originated from
different parent rocks, were in order of dolerite
(78 mg kg-1) > peridotite (77 mg kg-1) > pegmatite (28
mg kg-1) and pegmatite (121 mg kg-1) > peridotite
(111 mg kg-1) > dolerite (28 mg kg-1), respectively. For
most of the studied pedons, profile metals distribution
differed among the soils: The values of Fe, Cu, and Ni were
enriched in the cambic horizons mainly as result of release,
mobilization, and redistribution of the studied metals during
geopedological processes, whereas those of Zn and Mn
were concentrated in the surface horizons. Probably due to
greater weathering rate of trace metal-bearing rocks on
north-facing slope, the content of the trace metals along
with the geoaccumulation index (Igeo) and the degree of
soil contamination (Cd) were higher than on south-facing
slope. Based on assessment of soil pollution indices, the
soils were categorized as unpolluted [Igeo ≤ 0 (class 0)],
unpolluted to moderately polluted levels [0 < Igeo < 1
(class 1)], and very low [Cd < 1.5 (class 0)] to low degree
of contamination [1.5 < Cd < 2 (class 1)].
Keywords
Trace metal; Parent rock; Slope aspect; Pedon; Geopedological processes
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