Dual-directional Regulation Mechanism Of Oyster Shell Powder On Phosphorus In Sediments

Phosphorus has double-threshold effects on primary production.Based on the utilization of oyster shell powder for the propagation of Manilaclam,it's considered that oyster shell powder has dual-directional regulation effects on phosphorus in sediments.Nevertheless,there's few data about it.To verify the hypothesis,the present work focuses on the forms of phosphorus,migration/diffusion fluxes at the sediment-water interface of phosphorus exposed to different conditions.Considering the regulation effect of oyster shell powder on pH,abuandance organic matters and metal cations contents,the adsorption kinetics and isothermal adsorption characteristics of phosphorus and form variance of phosphorus in sediments at different conditions were studied.The results were showed as following,1)The adsorption kinetics of oyster shell powder on phosphorus has signifianct relation with duration,e.g.,exposed to exogenous phosphate,oyster shell powder has dual-directional regulation effect on the migration/transformation of phosphate Based on the isothermal adsorption characteristics of oyster shell powder on phosphorus,oyster shell powder works as source of phosphorus in water without the action of exogenous phosphate,which is related to the particle size of oyster shell powder.2)Without exogenous phosphate,the sediment works as "phosphorus source" for the water body.The effect of the "source" is related to the pH,the concentration of exogenous Ca2+,Fe3+,glucose and protein.Moreover,Ca2+makes the sediments to work as one "sink" for phosphate.The alteration of phosphorus "source" and "sink"depends on the exogenous Ca2+ concentration.3)If there's exogenous phosphate,pH,exogenous Ca2+,glucose and protein all have dual-regulation effects on the adsorption and desorption of phosphate at the sediment surface.The dualregulation is related to pH,exogenous Ca2+,glucose and protein concentration.Moreover,exogenous Fe3+increases the adsorption behavior of phosphate in sediments.4)pH?glucose and protein have significant promotion effect on the form of phosphorus in sediments.The effect is related to pH?glucose and protein concentration.Exogenous Fe3+ has dual-regulation effect on the form of phosphorus in sediments.The effect is related to exogenous Fe3+ concentration.Moreover,exogenous Ca2+ has promoting effect and dualregulation effect on the form of phosphorus in sediments.These effects are related to the exogenous Ca2+concentration.The research results cann't only be helpful to use marine aquaculture solid wastes such as oyster shells fully,but also be useful to regulate the phosphorus in filter-feeding shellfish farming ecosystems and the ecological restoration of damaged ecosystems.