The role of phytoplankton in the removal of arsenic by sedimentation from surface waters

Abstract

The role of phytoplankton in the removal of arsenic (As) by particle adsorption and sedimentation was investigated in Moira Lake, Canada . Sampling water and suspended particles over one year illustrated significant variation in As partitioning between particulate and aqueous phases, but failed to establish a correlation between the partition coefficient, Kd, and indicators of phytoplankton biomass . A highly significant inverse logarithmic relationship was noted between Kd and the concentration of suspended particles (log Kd =5 .1-1 .4 log SS ; p = 0.0001) in an apparent demonstration of the particle concentration effect (O' Connor & Connolly, 1980) . Particle deposition, measured by means of sediment traps, appeared to include a substantial component of resuspended surficial sediment making sediment trap results unreliable for quantifying the removal of substances from the water column . The As concentration of particles from deep traps deployed during late summer and early fall exceeded the As concentrations of suspended particles and surficial sediment, and may indicate that a highly contaminated nepheloid layer acts as a temporary sink for As .