Adsorption and recovery of dissolved organic phosphorus and nitrogen by mixed-bed ion-exchange resin

A laboratory study was conducted to investigate the efficacy of using various mixed-bed anion-cation exchange resins in absorbing dissolved organic and inorganic N (DON and DIN) and P (DOP and DIP). Leachate from foliage of aspen (Populus grandidentata) was passed through columns containing three brands of mixed-bed resin contained in nylon bags, with and without pretreatment of the resins by rinsing with KCl. After leaching, the resins were extracted with either 2 M KCl or 2 M HCl, and recoveries of DIN, DON, DIP, and DOP were calculated. The results showed that all brands of resin adsorbed more DIP (91-98.5%) than DOP (55-70%) and more NO^sub 3^ (87-100%) than NH^sub 4^ (0-14%) and DON (18-49%). In general, pretreating the resin significantly decreased absorption. The recovery of DIP and DOP was influenced by the pretreatment and the extracting solution whereas the recovery of DIN and DON was problematic because of the release of amine groups. Overall, the use of mixed-bed resin seems adequate for P studies but not for N studies on a short-time scale. Longer exposure periods are needed for studies of N so that the signal/noise (blank) ratio is higher than in this study.