Wednesday, 13 March 2013

Uranium contamination of ground water in southwest Punjab

In recent years, concerns are being raised about the possible carcinogenicity and neurological disorders due to the ingested uraniumthrough drinking water in southwest Punjab. The X-ray fluorescence research group at Panjab University has carried investigations to identify the potential source of ground water contamination.

 The earlier contemplated sources in the form of fly ash

from thermal power plants in Bathinda and the industrial drain Budha Nullah draining
into Sutlej in Ludhiana have been ruled out on the basis of systematic investigations.
Other sources like existence of Tethys sea at nascent stage of earth, weathering of
exposed granite rocks at Tosham hills, pesticides and depleted uranium used in wars
have also been discarded.  Agrochemical processes are favoured candidates for uranium
contamination of ground water. Southwest Punjab consists of Sutlej-Ghaggar plain,
where the soil had largely developed by the material lid by rivers (alluvium) upto a
depth of thousands feet. As expected, the region is deprived of uranium deposits. The
uranium content in the soils is ~ 3 microgram/gram. Extensive irrigation of rich
agricultural area and drinking water supply schemes in the region are mainly based on
the available network of canals. Most of the region is water-logged and the soil is
calcareous. Solid pieces of calcium carbonate (kankars) are frequently observed in
Bluana village, where maximum uranium concentrations of few hundred microgram/litre,
and total dissolved salts (TDS) of gram/litre have been observed. Irrigation water
percolating through soil dissolves carbon dioxide gas produced at high pressures from
the plant root respiration and the microbial oxidation of the agriuculrtural matter.
The resulting carbonic acid reacts with the insoluble calcium carbonate to produce
soluble bicarbonate, which is an efficient agent for leaching uranium from soil.
Percolating bicarbonate solution adds uranium to the ground water. Phosphate
fertilizers (uranium content more than50 microgram/gram) used in the cotton
cultivation belt further add to the contamination. The concentration of chemicals
produced due to decay of agricultural matter in calcareous soil and use of phosphate
fertilizers, and dissolved salts in irrigation water are continuously increasing to
threatening levels in the ground water due to the minimal use of the ground water.
Similar high concentrations of bicarbonates do exist in ground water at many places,
but the ground water lever is low and there is continuous excessive use of ground
water. These features prolong the period before the ground water quality deteriorates.
Dr. Jurgens and collaborators from U.S. Geological Survey have reported strong
correlations between uranium and bicarbonate in the ground water in Central Valley,
California, where ate least 23 public-supply wells have to be retrieved from service
within the last 20 yeasrs due to increased concentration of uranium. More details are
available at website of Physics Department, Panjab University
( Facts regarding the wateerlogging problem,
health hazards like autism and sub normal physical growth of special children, and
growing incidences of cancer are also discussed.

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