3.1 Morphological features of tailing profiles
Mining activities drastically altered soil morphological features
(Figures S1 and S2). In tailing derived from sandstone materials, tin
mining activities altered the soil morphological features from sandy
clay loam texture, dark brown topsoil and yellowish brown subsoil in
native soil (TBB4 profile) to sandy texture with stratification of light
grey and yellowish grey (TBB1) or of yellowish grey and reddish grey
(TBB2) colour throughout profiles (Figure S1). Further, a spoil profile
with a mixture of native topsoil and sandy tailing showed a mixture of
brown and greyish colours in the topsoil (TBB3 profile), which was
underlain by greyish sand and whitish kaolin colours. The presence of
yellowish and reddish colours in sandy tailing profiles indicated the
initiation of soil formation in post-tin mining areas.
For post-tin mining soils developed from granite parent materials,
morphological properties drastically altered from deep solum
(> 140 cm), dark greyish brown topsoil and yellowish brown
subsoil with sandy clay loam texture (TBB5; Figure S2) in the native
soil to loamy sand and grey colour in post-tin mining. These native soil
properties disappeared after mining was related to sluice and washing
during the separation of heavy tin ore from light sand fractions. The
profile of a sandy tailing (TBB6), which has been reclaimed for 26 years
using Acasia mangeum started a weak soil development as indicated
by yellowish colour (iron mobilization and precipitation), the formation
of fine soil granular structure, and the growth of many fine roots
downward to 60 cm deep (Figure S2). Unfortunately, the formation of fine
soil granular structure was not shown by TBB7 profile, a counterpart of
TBB6 and just 6 m away. The absence of fine soil granular structure in
the TBB7 profile was due to re-mined activities by local traditional
miners and abandoned as bare land by 2008 (8 years old of post tin
mining), leading to reset back the new start of soil development. The
interlayer variations with different colours within a profile indicated
the initial accumulation of iron with yellowish grey colour (probably
goethite) and it’s leaching down the profile.