Table 2.

Impact and mechanism of water management regime on As-methylation indicating effect of the regime and mechanism of iAs conversion to methylated As and references (Ref.).

Water regime	Effect	Mechanism	Ref.
CF	CF creates anaerobic (anoxic) conditions that cause arsenic-reducing bacteria to thrive	Thriving As-reducing bacteria use AsV as electron acceptor during their metabolic processes which convert AsV to AsIII as follows: AsV + 3e- + 3 H+ → AsIII + H2O Methylation of AsIII to MMA as follows: AsIII + SAM) → MMA + SAH Methylation of MMA to DMA as follows: MMA + SAM → DMA + SAH	[16]
AWD	AWD creates alternate oxic and anoxic conditions	Alternate oxic and anoxic conditions fosters growth of different microbial populations Under oxic conditions, certain bacteria oxidize AsIII to AsV. Under anoxic conditions, other bacteria reduce AsV back to AsIII. Different microbial populations methylate AsV to MMA and DMA.	[13]
ARC	ARC increases oxygen level in root zones	Elevated oxygen levels fosters growth of different microbial populations Different microbial populations transform iAs into oAs species	[101]
SDI	SDI induces variable oxygen availability	Variable oxygen availability influence the activity of different microbial communities. Microorganisms variably impact As transformations.	[101]

Note: CF, continuous flooding irrigation; AWD, alternate wetting and drying; ARC, Aerobic rice cultivation; SDI, Subsurface drip irrigation.