Heavy metals clog Sabarmati river’s entry and exit

Ahmedabad: A new hydrochemical study published in the April edition of an Elsevier journal, ‘Cleaner Water', suggests that the Sabarmati river's health is increasingly being influenced by the industrial pollution it carries.The study, based on a "multi-index" framework, tracked ten specific sampling sites from the city's northern entry at Motera Stadium to its southern exit near Shastri Bridge. While much of the river's baseline chemistry is governed by natural rock weathering — known as geogenic control — the researchers found that industrial and urban activities have introduced a distinct "anthropogenic fingerprint" through heavy metal discharge. Anthropogenic refers to human activities. The primary tool for the study's assessment was the Heavy Metal Pollution Index (HPI). While the river's city-wide average of 87.15 remains below the critical risk threshold of 100, this figure masks severe localized contamination. At three key locations — Motera , the city's Power Plant area , and Shastri Bridge — the HPI scores soared to 306.15, 169.27, and 251.30, respectively. The study examined 10 strategic sampling sites to determine if the water is fit for human use. The researchers belong to Gujarat University and the Central Salt and Marine Chemicals Research Institute. They are Mukesh Chaudhari, (now, the late) Prof Pranav Shrivastav, G Ali, Dushyantsingh Rajpurohit, Ajay Pandya, Saif Syed, Mital Borkhatariya, Anjali Depani, Smit Patel, Pavan Ramchandanee, Arpan Patel, and Narendra Purohit. The researchers documented a significant shift in the river's chemistry as it traverses the 10-kilometre urban core of Ahmedabad. The Water Quality Index (WQI) classified 40% of the samples as "excellent" and 60% as "good". The most persistent concern identified by the researchers is mercury. While metals such as zinc, lead, and cadmium were detected at levels within the safe regulatory limits, mercury concentrations at the entry and exit points exceeded the Bureau of Indian Standards (BIS) limit of 1.0 microgram per litre (µg/L). BOX THE LIFELINE'S DEBILITATING LOAD Heavy metals in the Sabarmati 1. Calcium and magnesium were traced to natural rock weathering, forming the river's geological baseline 2. A separate "salinity-metal axis" — of cadmium, chromium, cobalt, and mercury — was linked entirely to urban sewage and industrial discharge 3. Contamination levels vary along the river's course 4. At Subhash Bridge, Dandi Bridge, and Ellis Bridge, metal concentrations drop, indicating limited natural dilution and sediment settling 5. This mid-city "recovery" is temporary and incomplete 6. Downstream accumulation at the city's exit shows that Ahmedabad's cumulative industrial load ultimately overwhelms the river's natural self-cleansing capacity Table 2: Concentration of key toxic elements (µg/L) MetalMoteraShastri BridgeBIS LimitPrimary SourceMercury (Hg)4.7123.8431.0Electroplating/chemicalsCadmium (Cd)0.9470.6053.0Textile/batteriesLead (Pb)1.2105.34610.0Urban runoff/industrialZinc (Zn)65.1924.9615,000Industrial effluentsTable 3: Heavy Metal Pollution Index (HPI) by location LocationHPI scoreStatusNear Motera Stadium306.15ContaminatedPower Plant169.27ContaminatedCentral urban core< 100Low riskAround Shastri Bridge251.30Contaminated