Study of nitrate contamination in groundwater of Gurgaon district
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Date
2006
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CCSHAU
Abstract
Groundwater samples were collected from different tubewells located in tow
villages and field experiments were conducted at a farmer field in village
Jhanjrola-khera, district Gurgaon to investigate the occurrence of nitrate in the
groundwater.. The surface soil of the study area was loamy, while subsurface soil
(8.10 to 10.80 m) belongs to sandy loam. All the samples collected during different
time periods showed nitrate concentration of about more than twice the maximum
acceptable nitrate concentration for drinking water standards (45 mg L-1) as per the
guidelines specified by WHO. Comparison of nitrate concentration in groundwater
samples collected during pre and post monsoon periods indicated a slight decrease in
nitrate concentration of groundwater during the post monsoon period.
The EC of groundwater samples from village Mubarikpur varied from 1.25 to
2.35 dS m-1 while the EC of different groundwater samples of village Jhanjrola-khera
was more than 5.91 dS m-1. The average nitrate concentration in the samples
collected from village Mubarikpur (61.50 mg L-1) was lower than that of
Jhanjrola-khera (83.89 mg L-1).
Soil samples were collected from a exploratory bore hole and certain pumping
tests were conducted. All the samples were within the low limit for available nitrogen
(< 250 kg ha-1) and organic carbon (< 0.4 %), but high in terms of total nitrogen (>
0.06 %). Pumping tests were conducted for both the installed gravel-packed and an
existing cavity type tubewells with respect to nitrate concentration in the pumped
groundwater. The nitrate concentration did not change considerably with the discharge
and time during the pumping tests. Nitrate concentrations in the pumped water varied
from 1.54 to 1.59 me L-1 for both the tubewells. The shallow groundwater in the
upper aquifer showed less amount of nitrate i.e. 1.44 me L-1 as well as lower
groundwater EC of 3.47 dS m-1 against EC 7.41 dS m-1 for the pumped groundwater
(bottom aquifer). Average transmissivity and hydraulic conductivity of the aquifer was
found to be 239.71 m2 d-1 and 57.07 m d-1, respectively. Average values of storage
coefficient, hydraulic resistance and leakage factor was found to be 2.05 x 10-3, 20.47
days and 70.0 m, respectively. Lower nitrate concentration in relatively shallow
groundwater as compared to relatively deep groundwater, higher total nitrogen
throughout the subsurface profile to a depth of 15 m and wide variation in nitrate
content among tubewell water of contiguous villages indicated geological
characteristics rather than agricultural practices as the main cause of the occurrence of
high nitrate in the groundwater of Gurgaon district.