Dissolved Component Recovery Following Resin Exchange Based DOM Fractionation

Organic and inorganic components in natural waters are intimately interrelated and constitute a dissolved material matrix (DMM). The objective of this study was to systematically investigate the distribution and recovery of both organic and inorganic components in chemically fractionated natural waters. Untreated and previously coagulated natural waters were fractionated into hydrophobic and hydrophilic acid, base, and neutral DMM fractions using a resin exchange based protocol. Mass balances on nonpurgable dissolved organic carbon, aluminum, iron, and manganese were used to evaluate DMM component recovery. Quantitative recovery of dissolved organic matter was achieved, whereas, aluminum, iron, and manganese recoveries were largely incomplete (30-92%). Coagulation increased the recovery of all metals examined. Incomplete metals recovery was attributed to imperfect elution from MSC-1 cation exchange resin and appeared related to the distribution coefficient Kd of each metal with this resin. DMM component distribution among chemical fractions was altered by coagulation, with dissolved organic matter preferentially removed in the hydrophobic acid fraction. Unrecovered metals appeared to consist primarily of colloidal mineral (hydr)oxides solubilized by acidic pH conditions imposed during fractionation.