Srinagar, Aug 5: Water chestnuts harvested from Kashmir’s lakes are accumulating heavy metals from polluted waters, a study has discovered.
Dal Lake comes across as the most concerning, recording the highest overall contamination burden among the Valley’s four major freshwater bodies. The significant research has been published in the journal Scientific Reports, part of the Nature portfolio.
The researchers analysed water, lake sediments, and water chestnut (Trapanatans) plants from Dal Lake, Hokersar Wetland, Manasbal Lake, and Wular Lake. They examined eight heavy metals, cadmium (Cd), and chromium. The study found a clear pollution gradient, with urban-located Dal Lake showing the greatest overall heavy metal accumulation. This, interestingly was followed by Hokersar Wetland, also in a semi-urban location.
Not just the waters, the study found heavy metals had entered the edible water chestnut fruits. This indicates that pollution in Kashmir’s freshwater ecosystems has already begun moving into the foods consumed by people. Water chestnut acts as an efficient absorber of heavy metals from its surroundings, the study states. The contamination remains trapped in the plant’s roots majorly, followed by the shoots and finally the edible fruits.
Roots have the highest levels of heavy metals, and this strong root retention limits the movement of contaminants through the plant. However, it does not completely prevent them from reaching the edible portion. “The presence of heavy metals in edible tissues indicates a potential pathway for contaminants to enter the food chain,” the study notes.
However, it is worth noting that not all metals pose the same risk. Iron and zinc made up the largest share of the total metal load in all plant tissues, as both are naturally abundant in the environment. These are also essential nutrients required for plant growth. The greater public health concern is the presence of much smaller amounts of toxic metals: cadmium and chromium.
These were consistently detected in edible fruits. Unlike iron and zinc, these metals serve no biological function in humans. These can pose health risks due to their accumulation in human tissues over time and prolonged exposure. The researchers have emphasised the need for continued monitoring of heavy metal levels in water bodies.
While the study measured contamination in the environment and the plant, it did not delve into the levels of these elements required to pose an anatomical risk in humans. Significantly, the study describes Dal Lake under the highest pollution pressure among the four water bodies studied. Resultantly, water chestnuts from Dal Lake accumulated the greatest overall heavy metal load in roots, shoots and fruits.
Another major scientific finding from the study is regarding the water chestnut plants. These have been found to readily concentrate metals from water, thus having the potential to serve as an effective biological indicator of pollution. Ironically, the same ability that allows water chestnut to absorb pollutants, thus a possible phytoremediation specie. These plants allow the natural removal of contaminants from water bodies.
Researchers are of the opinion that the plant could tbe useful both for monitoring pollution and helping in its bioremediation. However, as an edible plant, its metal levels need to be monitored by food safety authorities. The researchers are of the opinion that in view of the elevated cadmium levels in chestnuts from Dal Lake, their consumption must be limited.
This, until pollution control and remediation measures are implemented. The study makes it amply clear that wastewater treatment in Kashmir is almost inexistent. Untreated sewage and agricultural runoff enters lakes and pollutes not just the waters but its flora and fauna as well. The findings also raise questions about lotus stem (nadru) harvested from Kashmir’s lakes.
Nadru forms an more popular part of Kashmir’s menu.
A separate study published last year had found that lotus plants grown in Dal Lake also accumulate heavy metals.
Most metals were retained in underground tissues. However, these findings point to the need of monitoring heavy metal levels in plants and plant products harvested from water-bodies of Kashmir, where effluents and wastes enter water without any treatment.
