Cation-induced coagulation of aquatic plant-derived dissolved organic matter: Investigation by EEM-PARAFAC and FT-IR spectroscopy

Authors: LIU, SHASHA - Chinese Research Academy Of Environmental Sciences; ZHU, YUANRONG - Chinese Research Academy Of Environmental Sciences; LIU, LEIZHEN - Beijing Normal University; He, Zhongqi; GEISY, JOHN - University Of Saskatchewan; BAI, YINGCHEN - Chinese Research Academy Of Environmental Sciences; SUN, FUHONG - Chinese Research Academy Of Environmental Sciences; WU, FENGCHANG - Chinese Research Academy Of Environmental Sciences

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2017
Publication Date: 1/8/2018
Citation: Liu, S., Zhu, Y., Liu, L., He, Z., Geisy, J.P., Bai, Y., Sun, F., Wu, F. 2018. Cation-induced coagulation of aquatic plant-derived dissolved organic matter: investigation by EEM-PARAFAC and FT-IR spectroscopy. Environmental Pollution. 234:726-734.

Interpretive Summary: Composition and characteristics of dissolved organic matter (DOM) are key factors in determination of its interactions with metal cations, including sorption and coagulation. Studies on cation-induced coagulation of plant-derived DOM and their difference from other types of organic matters were of great need to fill this gap in DOM research, which would further enhance our understanding of the environmental behavior of DOM in aquatic systems. Thus, in this study, the cation-induced coagulation of plant-derived DOM was characterized by using EEM-PARAFAC and FT-IR spectroscopy. These results indicated that plant-derived DOM might have a long-lasting effect on water quality and organisms due to its poor coagulation with metal cations in lake ecosystems. Data yielded in this study would be helpful in assessing removal of DOM during coagulation-flocculation with metal ions (Ca, Al, and Fe), and in exploring molecular and structural characteristics of the aquatic plant-derived DOM during and post cation-induced coagulation.

Technical Abstract: Interaction and coagulation of plant-derived dissolved organic matter (DOM) by metal cations are important biogeochemical processes of organic matter in lake systems. Thus, coagulation and fractionation of plant-derived DOM by di- and tri-valent Ca, Al, and Fe ions were investigated. Metal ion-induced removal of DOM was determined by analyzing dissolved organic carbon in supernatant solutions after addition of these metal cations. Both dissolved and the coagulated organic fractions after metal additions were characterized by use of fluorescence excitation emission matrix-parallel factor (EEM-PARAFAC) analysis and Fourier transform infrared (FT-IR) spectroscopy. Addition of Ca, Fe, and Al resulted in a net removal of plant-derived DOM. Efficiencies of removal of DOM by trivalent Fe and Al were much greater than that by divalent Ca. However, efficiencies of removal for plant-derived DOM by the three metals were much less than that of humic materials. The molecular and structural features of plant-derived DOM fractions impacted by metal cations additions were characterized by the changes in fluorescent components and infrared absorption peaks. Results showed that Ca preferentially removed higher molecular weight, aromatic, carboxylic-like and amides organic matters by coagulation, while Fe and Al removed aromatic, carboxylic-like and phenolic materials. These observations indicate that plant-derived DOM might have a long-lasting effect on water quality and organisms due to its poor coagulation with metal cations in lake ecosystems. Results of this study have implications for treatment of sewage with various sources of organic matters.