Assessment of radon and potentially toxic metals in agricultural soils of Punjab, India

Radon, a radioactive gas is a primary source of radioactive pollution and directly influence the humans exposed to it. Radon (Rn-222)/thoron (Rn-220) exhalation and soil gas radon concentrations were estimated in agricultural soil samples from different locations of Amritsar district of Punjab, India, by using active techniques i.e. Smart RnDuo monitor and RAD7. Rn-222 mass and Rn-220 surface exhalation rate of 22 locations varied from 21.41 to 43.81 mBq kg(-1) h(-1) and 64.73 to 717.03 mBq m(-2) s(-1) with average values of 32.58 +/- 1.11 mBq kg(-1) h(-1) and 195.10 +/- 53.02 mBq m(-2) s(-1), respectively. Mean soil radon concentration of 12 agricultural soils samples varied from 0.1 +/- 0.04 to 9.7 +/- 0.40 kBq m(-3). Potentially toxic metals such as Zn, Cu, Pb, Cr, and Cd were also estimated in agricultural soil samples and soils were found to be drastically suffering from Zn and Cu pollution followed by some Pb contamination. On the basis of average values (in mg kg(-1)), potentially toxic metal contents in soil samples can be arranged in decreasing order as: Zn (78.93) > Cu (42.32) > Cr (36.92) > Pb (7.49) >> Cd. The results indicated the probability of occurrence of potentially toxic metal accumulation in edible parts of crops grown in the study area. Although no direct significant correlation has been observed between soil gas radon and mass/surface exhalation rate in soil samples under investigation but a positive correlation was observed among some toxic metals such as Zn:Cu, Zn:Cr, Cu:Cr, Cu: Pb and Pb:Cr. pH and conductivity were negatively correlated whereas, SOM and mass exhalation showed positive correlation. The investigation demonstrated the dominance of potentially toxic metal contamination by Cu, Zn and Pb over Rn-222 emanation rate in agricultural soil towards health risks posed to residents of Amritsar.