Chemical fractionation of heavy metals in wastewater-irrigated soils

Department of Environmental Science, The University of Burdwan, Golapbag, Burdwan-713 104, West Bengal, India E-mail : banenvs@gmail.com Manuscript received online 30 May 2017, accepted 30 June 2017 The present study was carried out to assess the distribution pattern of heavy metals and their chemical fractionations in wastewater-irrigated agricultural soils. Surface soil samples were collected from different locations from the wastewater-irrigated agricultural fields and analyzed for pH, organic matter, cation exchange capacity along with some heavy metals. The experiment showed that the mean Pb (85.998±4.537 mg/ kg), Cd (8.98±1.619 mg/kg), Fe (195±33.8 mg/kg), Cu (59.142±9.109 mg/kg), Mn (145.5 ±7.728 mg/kg) and Cr (39.88±5.676 mg/kg) exhibited the high concentrations in the studied soils. The speciation study revealed that the overall percentage of metal content in different fractions was in the sequence of Residual > Fe-Mn Oxides > Exchangeable > Organic > Carbonate. The investigation showed pronounced spatial distribution and significant accumulation of heavy metals in the agricultural soils. The trend of metal accumulation in wastewater-irrigated soil was in the order : Fe > Mn > Pb > Cu > Cr > Cd. The study revealed that a significant portion of metals from wastewater sources mainly occur in the labile fraction in the studied soils and may be taken up by organisms as the environmental parameters change. Eco-toxicological assessment of the studied soil using the mobility factor indices indicated high degree of metal mobility and therefore, poses a serious threat to ecosystem health