A study published in January 2021 by researchers from the National Center for Earth Science Studies, Thiruvananthapuram; SAL Institute of Technology and PDEU at Physical Research Laboratory, Ahmedabad, Gandhinagarfound that soil samples from some villages had high levels of metal contaminants, which exceeded WHO and Indian standards.
In 2018, the state government brought out a waste water policy for municipal corporations across the state regarding the reuse of municipal treated sewage for irrigation and industrial use. However, the policy does not set standards for heavy metal contamination, quality before disposal of waste water and frequency of quality monitoring. The state government should take into account the wider public health implications in the use of waste water.
Soil samples near and farthest from the Vasna-Narol bridge, Gyaspur and Khada, respectively, were more alkaline. The study noted that in Saroda, about 20 km downstream, the soil was acidic. Now when the researchers tested eight soil samples from different villages, the concentration of metals such as zinc was 421 micrograms per gram of soil, compared to 336 in the case of manganese. Copper 201, Chromium, Nickel 51, Lead 42 and Cobalt 9. Overall, the study claimed that almost all heavy metals were found in concentrations twice the permissible limits as per WHO and Indian standards.
“A close analysis of soil data shows that all metals exceed the upper limit of WHO or EU standards,” the report said. The researchers were Bibhabasu Mohanty, Anirban Das, Reema Mandal and Sukanya Acharya from PDEU and SAL Institute of Technology, and Upasana Banerjee representing PRL and NCESS, Thiruvananthapuram.
The study further stated, “Out of the eight soil samples, the sample collected from Gyaspur had the highest concentration of all the analyzed metals as compared to other sites. Gyaspur is the site where the wastewater from Vasna treatment plant is treated. The settlement is carried out, leading to the maximum accumulation of these metals in agricultural areas compared to all other sites.
The study suggested that there should be efficient treatment of wastewater in vegetables and monitoring of heavy metals in order to understand the risks associated with such water use.
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