Assessment of chromium hyper-accumulative behaviour using biochemical analytical techniques of greenhouse cultivated Sonchus asper on tannery waste dump site soils

Abstract

Keeping the sources of pollution such as chromium (Cr) under a safe limit is a daunting challenge due to the negative impact of heavy metal bioaccumulation in vegetation and the concomitant human health exposure. We took a closer look at Sonchus asper by cultivating in the green house. It resulted in 80% germination when cultivated over nine different soils collected from the tannery dump site. The biochemical analytical techniques such as mass spectrometry indicated significant bioaccumulation of Cr in the plant tissue. As per the ICP-MS analysis, this annual herb resulted in the accumulation of 601 mg kg⁻¹ of total Cr with 212 mg kg⁻¹ in its shoot from soil samples containing up to 41 mg kg⁻¹ of hexavalent Cr. The energy dispersive X-ray (EDX) spectroscopy of S. asper revealed a higher level of S element indicating a sulfate-Cr binding relation. Elevated content of Cr in soil (73,721 ± 65 mg kg⁻¹) caused biochemical changes in the shoot of S. asper as indicated by the disappearance of Fourier transform infrared spectroscopy (FTIR) bands at 935 and 872 cm⁻¹ and further revealing aliphatic –CH₂ appearing as anti-symmetry ν_a(CH₂) and symmetric vibration ν_s(CH₂) at the band of 2920 and 2850 cm⁻¹, respectively.