Proposal of biostimulation for hexachlorocyclohexane (HCH)-decontamination and characterization of culturable bacterial community from high-dose point HCH-contaminated soils

To locate a high-dose point hexachlorocyclohexane (HCH)-contaminated site, to identify HCH-degrading bacteria in it and assay HCH-decontamination by biostimulation. Methods and Results:  Bacteria were isolated by serial dilution method from HCH-contaminated soil samples collected from areas near an HCH-manufacturing unit and its dumpsite in North India. After confirming the presence of indigenous HCH-degraders (seven of 24 strains), an ex situ biostimulation experiment was conducted. For this, residue levels in soil were diluted by mixing with pristine garden soil and aeration, moisture and nutrients were provided intermittently. This soil was monitored for reduction in Σ-HCH (sum of α-, β-, γ- and δ-HCH) levels and stimulation of HCH-degraders. Experiments were conducted twice, in March-April (c. 75 μg Σ-HCH g−1 soil) and October-November 2006 (c. 280 μg Σ-HCH g−1 soil) at 26-30°C. Σ-HCH levels were reduced to