Mar 03, 2024
Mar 03, 2024
Nitrogen occupies by volume 78% of the earth’s atmosphere, making it a giant pool of this inert gas crucial for any form of life, especially for chlorophyll of the plants to carry on photosynthesis. The atmospheric, however, can not be utilized as such, it has to be fixed by many natural ways so that all living being may use it for their survival and growth. During conversion of nitrogen to a variety of chemical forms, part of it gets converted to nitrates and part to nitrite. As long the natural system works and the nitrogen cycle continues there is no problem. But due to human interference through excessive use of chemical fertilizers and poor waste management in urban clusters lead to excess amounts of nitrates find their way to aquifers in the sub-surface.
High nitrate values in ground water are alarming. There are reports from Kashmir, Punjab, Uttar Pradesh, West Bengal, North Eastern states, Rajasthan, Andhra Pradesh and Karnataka of values of nitrates in water samples from hand pumps and dug wells much higher than the prescribed standards. As per the Bureau of Indian Standards (BIS) the maximum permissible limit of nitrates in drinking water should never exceed 45 mg/litre. There is no relaxation to this limit as nitrate in quantities higher than the standards is known to cause mouth and or colon-rectal cancers, dementia, Alzheimer’s disease and methemoglobinemia (blue baby syndrome).
A cursory look at the following description is enough to indicate the nitrate footprint in the groundwater of our country:
Sopore, popularly known as the apple town of Kashmir valley produces one of the finest apples in, Asia has a high content of nitrates in water from the shallow and deep tube-wells, say Imran A. Dar, M.A. Dar and K. Sankar of Department of Industries and Earth Sciences, Tamil University, Thanjavur, Tamilnadu, in one of their research papers. Their findings state that 85% of samples have a high nitrate content during summer and 67% have a high nitrate during winter months.
The following table elaborates the results: (All values in mg/litre). The highlighted portions reflect analytical results from localities where nitrate content remains high in all the seasons:
Locality Summers Winters
1 Tawheed Bagh 33 51
2 Mumkak 51 52
3 Khwaja Gilgit 53 28
4 Colony Shalimar 78 56
5 Muslimpeer 52 40
6 Ashpeer 50 53
7 Sangrama 81 52
8 Duru 32 29
9 Shiva 51 32
10 Dangerpora 51 30
11 Nowpora 56 52
12 Alsafa Colony 32 50
13 Badam Bagh 56 55
14 New Colony 91 57
15 Shah Abad 54 54
Imran and his colleagues have found that the high values of nitrate are due to rampant use of chemical fertilizers in the apple orchards. High values of nitrate near cluster of hamlets could also be due to poor human waste management.
A report of Water Quality and Assessment Bureau of the Government of India states that a survey conducted in 2008 in Bathinda, Mansa and Patiala areas of Punjab has revealed nitrate values much higher than the prescribed norms of 45mg/lotre. In Bathinda out of 21 samples tested, seven have nitrates higher than 100mg/litre. Similarly samples from Muktsar and Ludhiana too have yielded nitrates more than 50mg/litre.
Punjab is considered to be the granary of India and use of chemical fertilizers is at the peak there. Thus most researchers conclude that the high nitrates in ground water are being derived from the fertilizers. However, there are contradictions to this find and a group of researchers blames poor human and animal waste management responsible for this malaise.
Uttar Pradesh is again an agrarian state with a high population density. Alarming results of high nitrate have come here during the recent researches.
N.J. Raju, U.K. Shukla and Prahlad Rao of Jawaharlal Nehru University claim that 18% samples of groundwater from dugwells and hand pumps in the holy and historical town have more than 45 mg/litre nitrate. Ground water samples have high nitrate content in the northern and eastern parts of their study area, e.g. Kakarmatha (90.4 mg/l); Shivdaspur (63.6 mg/l); Chandpur (62.4 mg/l); Maduadi (76 mg/l); Gurubagh (92 mg/l); Koharpur (55.1mg/l); Cantt Railway Station (66.7mg/l); Kotwa (67.1 mg/l) and Rajghat (92 mg/l). Very high concentrations along a straight line along parts of Varuna River have also been obtained.
Raju et al blame the poor management of domestic sewage, leaking septic tanks and improper management of landfills for high nitrate content in the northern and eastern parts of Varanasi. Along the Varuna they attribute the high values to seepage of irrigation water from the agriculture fields where the chemical fertilizers are used abundantly.
The report about high nitrate values in dug well and handpump water samples from Varansai created quite a furor amongst the researchers in U.P. Thus Nupur Srivastava and her colleagues A.K. Singh, Rohit Kumar, Swati and her guide Dr Munendra Singh of Centre of Advance Studies in Geology, Lucknow University, Lucknow carried out intensive surveys in Lucknow, the capital of Uttar Pradesh.
They divided the entire city in to a grid of two minutes interval along the latitude and longitude between which the city is located. This grid made 100 blocks and a drinking water sample was collected from India Mark II hand pumps installed in each block. The 100 samples thus collected were analyzed in the state of art laboratory of Wadia Institute of Himalayan Geology at Dehradun. The results obtained should cause a ripple amongst the water managers of the city, as high values of nitrate have been given by some of these samples.
Nupur et al found that nitrate concentrations range from 0.07-155.76 mg/l. Three percent of the samples show nitrate values much above the limit of 45mg/l. Three percent of the samples (above more than 20 mg/l) are in the desirable limit, 59% well within prescribed limit and rest 38% below detection limit.
Statistically the figures are not so alarming, but unfortunately the three percent samples exceeding the desirable limit of 45mg/l are from the localities Hussainabad (155.76mg/l), Alambagh (107.56mg/l) and Bijnaur (150.16mg/l). These localities are densely populated with a major chunk of population from below poverty line. These people have no option but to drink water from the hand pumps installed by the government.
Nupur et al state that drinking water samples violating WHO standards are from shallow aquifers at around 30 m depth. Nitrate is being leached due to leakage from sewerage system at weak zone of shallow aquifer. These migrate to depths of aquifer as water table is lowered due to overexploitation particularly in overcrowded residential areas.
West Bengal already reeling under the impact of arsenic laced groundwater is now facing the specter of nitrate concentrations in shallow aquifers like many other states. As per a report by the Central Ground Water Board Bankura and Bardhman are perhaps the worst affected districts! Water samples from Bankura district, Villages Basudevpur, Bheduasol, Khirpai, Khatra, Raipur and Gholkunda have shown nitrate content 81, 58, 81, 49, 81 and 58 mg/l respectively. Similarly the samples from Dakshinkhanda and Raniganj in Bardhman district have indicated nitrate content of 46 mg/l. As per the standards since there is no relaxation in nitrate content beyond 45 mg/l, the values of Bardhman district too are beyond safe limit.
A.K. Singh et al from North Eastern Regional Institute of Land and Water Management conducted systematic surveys for water pollution in all the eight states of the region. They report Nitrate content just above the prescribed limit from Assam (0.02-49.0 mg/l) and Arunachal Pradesh (0.00-45.3 mg/l-monsoon period). Nitrate content in the drinking water of remaining six states is within the limits. Higher nitrate content could be due to leaching of chemical fertilizers and or poor human waste management.
A.B. Gupta, a Professor in M.N.I.T., Jaipur, Rajasthan in a paper states ‘A survey conducted by Public Health Engineering Department Rajasthan in 2001-2 reported that 20659 villages/habitations had nitrates in drinking water more than 45 mg/l and 7675 villages/habitations had nitrate more than 100 mg/l. The districts of Jaipur, Nagaur, Barmer, Udiapur, Churu, Alwar and Tonk were the worst affected.’ The problem is common for the rural and urban areas both. The reason of enrichment of nitrates in groundwater is again man made. That is excessive use of chemical fertilizers and poor management of human and animal waste.
Interestingly Gupta observes that the groundwater table in Jaipur has depleted at an alarming rate in the past few years, as a result there has been a higher concentration of nitrates in groundwater, Gupta reports 8 to 16 times higher values of nitrates from drinking water from Jalupura, Sikar House and Banipark localities of Jaipur. These localities, like Lucknow are again densely populated and a large chunk of population is exposed to nitrate toxicity.
Scourge of nitrate pollution of groundwater is not limited to northern or eastern states alone. Nalgonda district of Andhra Pradesh is reported to have a range of nitrate in ground water from below detection limit to a whopping 879.65 mg/l. K. Brindha and co-workers from Geology Department, Anna University, Chennai report 13.78% of samples from Nalgonda district to have nitrate values much above the permissible values. They blame the nitrogen rich industrial waste, chemical fertilizers and worst of all dumping of human and animal excreta in disused well as the culprits.
The Hindu and Times of India had reported in 2009 occurrence of nitrate in quantities above permissible limits from Bangalore and Kolar districts respectively. The IT boom has made Bangalore a crowded city. Demand for water has acceded, consequently there is a tremendous pressure on the groundwater resources. Quoting a study conducted by Department of Environmental Science, Bangalore University and BARC, Mumbai, The Hindu reports occurrence of nitrate values from 10 to 400 mg/l from the central core of the city. The Hindu further says that 88% of surface water and 43% of groundwater in Vrishbhavathi and Arkavathi basins, Hebbal, Koramangala and Challaghatta villages exceed the permissible limit of 45 mg/l of nitrate. In case of Bangalore too the report blames leaking sewers, poor human and agri-waste management and disposal of nitrogen rich industrial effluents into water bodies.
The Times of India had reported high nitrate values from Gulbarga, Bijapur, Raichur and Tumkur districts. These districts have sanitation coverage below 20% the report states. Presence of higher quantities of nitrates in groundwater bears a testimony to poor sanitation the report says.
Nitrates beyond permissible limit of 45 mg/l can cause blue baby syndrome in the infants and children and cancers of the intestinal tract and rectum in the adults. On one hand we need nitrates to improve our crop productivity, but on the other hand if care is not taken they can ruin our own lives.
From the foregoing it is clear that nitrates in unnatural quantities have sneaked in to ground water reservoirs of a huge tract of the country. It is very difficult to cure the groundwater reservoirs as unlike the surface reservoirs, water there is stored as a film between the pore spaces of the sediments. In majority of the cases the problem is due to leaching of human waste. It means we are not giving due importance to Public Health Engineering and taking short cuts for disposal of human excreta. This is a serious situation. Since large chunks of population are involved the respective state governments will have to come forward and take preventive measures to control the further spread of the problem. Sadly nitrates have polluted the shallow aquifers of a major part of country. The shallow aquifers are the main water suppliers for dug wells and handpumps. Most of the consumers of water from these two sources are the poor masses. Unfortunately the areas where they live usually have poor sanitation facilities.
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More by : V. K. Joshi (Bijji)