‘High levels of fluoride and nitrate in Delhi groundwater’
Times of India - Nov. 20, 2020
NEW DELHI: Researchers from the University of Mami and Jamia Millia Islamia have found presence of high levels of fluoride and nitrate in Delhi’s groundwater. While fluoride levels are limited to north and northwest Delhi, where brick kilns are high in number and fluoride salts are used regularly, nitrate levels are present throughout the city due to surface runoff. A study conducted by the researchers revealed that except for the Yamuna floodplain and Najafgarh Lake, there was a decrease in groundwater levels across the city due to high built-up area in locations like Connaught Place and the presence of naturally present clayey soil that doesn’t support recharge.
Groundwater data from 1996 to 2018 collected by Central Groundwater Board (CGWB) from 258 stations in Delhi was used for the study. CGWB measures the groundwater levels four times a year to monitor seasonal variations. Atiqur Rahman of Jamia’s geography department said fluoride contamination was mostly concentrated in northwest district, with exceeding levels observed for seven out of 10 years. “Fluoride contamination occurred due to high levels of salinity and brick kilns. However, nitrates in the groundwater were more widespread. Out of 824 observations for nitrate contamination, 251 were above the limit. Northwest, New Delhi and South districts had nitrates above the limit of 50 mg/L as a result of runoffs from landfills and seepage into groundwater,” he added.
The main source of nitrates and fluorides in groundwater was directly related to the high levels of consumption of fertilisers, pesticides, herbicides, weedicides, etc. Fluoride is known to harm the skeletal structure and nervous system and cause other health ailments. Similarly, nitrates can cause cardiovascular and lung diseases. University of Miami’s Shouraseni Sen Roy said that lower infiltration rate of groundwater was associated with clayey soils in northern and northwestern parts of Delhi Metropolitan Region. “The limited areas of recharge, represented by the negative trends, were mostly concentrated in the east along Yamuna floodplain and in the southwest near Najafgarh Lake due to shallow bedrock and porous soils,” the report stated.
The results of the study highlighted the critical need for planned management of resources by ensuring adequate recharge of the water table to combat the steep decline in groundwater and potential severe impacts from climate change. The findings would help achieve the 6th Sustainable Development Goal of United Nations by 2030 as well as the goals identified in Delhi Master Plan 2041, said the researchers.
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