Exploring a multifunctional geoengineering material for eutrophication remediation: Simultaneously control internal nutrient load and tackle hypoxia.

• A MultiFunctional Geoengineering material (MFG) was developed to tackle eutrophication. • Capping treatment by MFG turns sediment from a nutrient (P and N) source to a sink. • O 2 nanobubbles delivered from MFG reverses hypoxia and reduces nutrient loads. • MFG functions as physical capping, nutrient absorber, and delivers O 2. • Contribution of each function on control of internal nutrient loads was quantified. An effective approach for control of internal nutrient loading and sediment hypoxia remains a longstanding challenge to the restoration of aquatic ecosystems. In order to simultaneously tackle these issues, a MultiFunction Geoengineering material (MFG) was developed for sediment remediation through the synergistic functions of physical capping, nutrient adsorption and delivery of O 2 nanobubbles. The MFG, derived from natural zeolite, exhibited superior (1.5–4 times higher) adsorption capabilities for both phosphate (PO 4 3−-P) and ammonium (NH 4 +-N), than pristine zeolite. The O 2 adsorption capacity was also enhanced from 46, observed in the natural zeolite, to 121 mg O 2 /g for the MFG. An in-situ sediment capping experiment in a eutrophic lake demonstrated that the application of MFG dramatically reversed sediment hypoxia (ORP −200 mV) to an aerobic status (ORP 175 mV) and, furthermore, stimulated sediment microbial activity, particularly nitrifying bacteria. The MFG treatment resulted the sediment changing from a nutrient source to a sink through decreasing the cumulative PO 4 3−-P and NH 4 +-N fluxes from the sediment by 124.6% and 131.1%, respectively. Moreover, the comprehensive functionalities of the material have been, for the first time, quantified, from which data O 2 nanobubble delivery was determined to be the largest contributor, reducing the fluxes of PO 4 3−-P and NH 4 +-N by 57.3% and 56.1% of, respectively. Our findings highlight the viability of such multifunctional material for the remediation of internal nutrient loads in lacustrine environments, towards sustainable eutrophication control. [ABSTRACT FROM AUTHOR]