The highest salinity was observed in the soil samples near Vasana-Narol bridge near the discharge point and near Gaspur-Khada. Also at Saroda, about 20 km downstream the soil was acidic, the study said. Now when the researchers tested eight clay samples from different villages, the concentration of metals like zinc was 421 micrograms per gram of clay, whereas in the case of manganese it was 336. In addition there were copper 201, chromium, nickel 51, lead 42 and cobalt 9. The study claims that almost all heavy metals are found in concentrations twice the permissible limits according to WHO and Indian standards.
A closer analysis of the clay data shows that all metals exceed the upper limits of WHO or European Union standards, the report said. Among the researchers were Bibhabasu Mohanty, Anirban Das, Rima Mandal and Sukanya Acharya from PDEU and SAL Institute of Technology and Upasana Banerjee was representing PRL and NCESS, Thiruvananthapuram.
The study further added that the sample collected from Gyaspur in eight clay samples had maximum concentration of all the analyzed metals as compared to other sites. Gyaspur is where the water from the Vasana treatment plant is discharged. Which makes maximum accumulation of these metals in agricultural fields as compared to all other sites.
Studies have suggested that efficient treatment of wastewater and inspection of heavy metals in vegetables should be done to understand the risks associated with such water use.