Natural Organic Matter-Metal Ion/Oxide-Phosphorus Complexes in Environment: A Review

Natural organic matter (NOM)-metal ion/oxide (Metal)-phosphorus (P) complexes as major P species widely exist in the aquatic and terrestrial environment. The behaviors of these complexes play an important role in the migration and transformation of P in the environment. The research progress of structure characteristics, determination methods, molecular weight identification, bioavailability and the influencing factors for the stability of NOM-Metal-P complexes at home and abroad are reviewed.The expectation to research on NOM-Metal-P complexes in the future are described. Previous studies indicate that NOM-Metal-P complexes account for more than 50%, whereas in some cases, more than 80% of P in natural water or soil solution. The metal ion/oxide could act as metal bridge which binds P to the surface of NOM. Currently, the high molecular mass fractions of NOM-Metal-P complexes were usually separated from free orthophosphate by 500 or 1 000 Da filters through ultrafiltration. In addition, it is found that NOM-Metal-P complexes can increase P migration in soil and it is also found that the bioavailability of P fertilizer containing NOM-Metal-P complexes is higher than those only containing single phosphate. Meanwhile, researchers also determined that the stability of NOM-Metal-P complexes were affected by ultraviolet light, pH and coexisting ions in both water and soils.