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August 25, 2009 - Goanet's 15th Anniversary
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http://mandgoa.blogspot.com/2009/08/what-mining-has-done-to-sirgaos-soil.html
National Environmental Engineering Research Institute based in Nagpur presented
and invstigative report titled "Assessment of the depletion of ground water
sources and land degradation in Sirgaon vilalge, Goa and mitigation measures"
in March 2009 to the Goa bench of Bombai High Court, Panaji in respons to
Sirgaon villagers Public Interest Litigation (PIL). Below are extacts from the
report's page numbers 77-78.
Conclusions
It is evident from the foregoing soil analysis that mining leads not only to
pollution of surface and ground water but also accelerates by surface runoff
which, in turn, results in deposition of mining waste in agricultural fields.
Silt accumulation due to erosion by water on agricultural field result in
significant changes in soil properties, which are linked with changes in crop
growth properties, biomass production and seed yield. In present study, based
on analysis of the different physico-chemical and microbiological properties of
soil samples collected from specific sites of the study area and assessment of
extent of agricultural land affected by open cast mining, following conclusions
are drawn.
ü Erosion of mine overburden and mine land leads to its deposition down the
slope in the command area. The silted soil belongs to the texture class “silty
laom” whereas the control soil belongs to class “silty clay loam”. The low
water retentivity, rapid permeability, low infiltrations (in soils with having
clay pan) moisture stress conditions, etc, leads to decline in water use
efficiency in irrigated areas in case of silty loam soil.
ü The water-logging problem in the silted soil was due to hard clay formed from
deposition of silt which ultimately affects the growth of the plants. This has
direct influence on the growth of the plants and also affects the availability
of plant nutrients.
ü The information collected from farmers revealed that the acidity in the
cultivated areas has been considerably increased (pH lowered) in the areas
where deposition of sediments/ silt from mining took place with reduction in
Paddy yield.
ü The water holding capacity, CEC, organic carbon and nutrients content of the
silted soil were very low as compared to control soil. The microbial
population, which is responsible for carrying out different bio-geo-chemical
cycles and production of plant growth promoting hormones in the soil, which
supports the plant growth, is highly affected in the silted soil as compared to
good cultivated one. It is obvious that low organic matter content resulted in
the reduction in CEC, nutrients and microbial activities of silted soil.
ü As silted soil developed from granite-gneiss parent rock formation of
argillic horizon in the soil there is the soil there is the problem because of
high free Fe2O3 and Mn contend. The overburden material rich in iron content
and also contain lot of gravels and have deficiency of Ca, S and Zn.
ü Thus deposition of silt overburden from the mine waste resulted in changes in
soil properties including soil texture, nutrient content and soil water status.
ü In view of the deterioration of soil quality due to silt deposition, it is
essential that suitable mitigation measures are implemented for restoration of
the degraded land. The mitigation measures are delineated in Chapter 4 of the
report.
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