Abdul Wahab Khan
Panaji: A water quality analysis conducted across Gaondongrim and Cotigao panchayats has revealed high levels of heavy metal contamination in groundwater sources, with iron and manganese concentrations exceeding Bureau of Indian Standards (BIS) limits at several locations, raising potential health concerns for residents.
The Central Ground Water Board study analysed 23 water samples during the pre-monsoon season and a similar number post-monsoon. While most trace elements were found within permissible limits, iron, manganese and copper emerged as major contaminants. Iron levels peaked at 3,565 parts per billion in samples from Nanem, far above the BIS limit of 300 ppb. Manganese recorded an even higher concentration of 4,675.9 ppb at the same location, against a permissible limit of 100 ppb.
Copper contamination was also detected, with a sample from Badsarem showing 189.14 ppb, nearly four times the prescribed limit of 50 ppb.
The report warned that such elevated levels of iron and manganese require immediate monitoring and surveillance to prevent potential health impacts, including gastrointestinal and neurological disorders.
Scientists attributed the contamination primarily to natural geological processes rather than industrial activity. The presence of iron- and manganese-rich oxide minerals in lateritic formations and mafic minerals
in underlying schist and phyllites leads to leaching during intense weathering. This process results in the accumulation of iron and manganese in laterite profiles, which subsequently seep into groundwater.
During pre-monsoon sampling in May, nine out of 23 samples showed excessive iron content, with Nanem and Pansulemol recording the highest levels at 1.32 milligrams per litre. Manganese levels exceeded permissible limits at seven locations, with Nanem again recording the highest concentration at 4.68 milligrams per litre.
Post-monsoon analysis conducted in November indicated improvement in overall water quality, likely due to dilution from rainfall. Most samples fell within acceptable limits for trace elements such as chromium, nickel, zinc, arsenic, selenium, molybdenum, cadmium, barium, lead and uranium. However, manganese remained above permissible levels at Indravada, registering 0.108 milligrams per litre.
The study also found that spring water quality was consistently better than that of shallow dug wells and deeper borewells. The report stressed the need for appropriate water treatment measures to ensure safe drinking water in affected areas.
