A study published in January 2021 by researchers from the National Centre for Earth Science Studies, Thiruvananthapuram; Physical Research Laboratory, SAL Institute of Technology in Ahmedabad and PDEU, Gandhinagar, found that soil samples from a few 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 concerning reuse of municipal treated sewage for irrigation and industrial use. the policy, however, does not lay down standards for heavy metal contamination, quality of waste water before it is disposed of, and frequency of quality monitoring. the state government should keep in mind wider public health implications in the use of waste water.
Soil samples closest to and farthest from the point-of-discharge near Vasna-Narol bridge, Gyaspur and Khada, respectively, were more alkaline. At Saroda, almost 20km downstream, the soil was acidic, the study reported. Now when the researchers tested eight soil samples from various villages, the concentration of metals such as zinc was 421 microgram per gram of soil, while in the case of manganese it was 336. Copper was 201, chromium, nickel was 51, lead 42 and cobalt 9. In all, the study claimed that almost all heavy metals were found in concentrations twice the permissible limit according to WHO and Indian standards.
“A closer analysis of the soil data reveals that all the metals exceed the upper limit of WHO or European Union standards,” states the report. The researchers were Bibhabasu Mohanty, Anirban Das, Reema Mandal and Sukanya Acharyya from PDEU and SAL Institute of Technology, and Upasana Banerji was representing PRL and NCESS, Thiruvanthapuram.
The study further added, “Among the eight soil samples, the sample collected from Gyaspur had the maximum concentration of all analysed metals compared to other sites. Gyaspur is where effluents from the Vasna treatment plant get disposed off, which leads to maximum accumulation of these metals in agricultural fields compared to all other sites.”
The study suggested that there be efficient treatment of wastewater and monitoring of heavy metals in vegetables to understand the risks associated with the use of such water.