where M is mass of arsenic that entered the system as inflow (mg) during time t (duration of the experiment over which the mass balance is applicable), M is mass of arsenic that exited the system as outflow (mg) during time t, M is mass of arsenic retained in sediment (mg) after time t, M is mass of arsenic retained in T. latifolia (mg) after time t, and M is mass of arsenic unaccountable (i.e. a loss or gain from mass balance calculation) (mg). The M term was calculated from arsenic concentrations from sediment samples according to Eq. (6)