New Perspective into the Impact of Drying Pretreatment on Phosphorus Performance in Sediments

Purpose of Review

Different drying methods can cause errors in determining the content and evaluating the biological effectiveness of various forms of phosphorus (P) in sediment. The drying pretreatment effectively promotes the conversion of amorphous iron and aluminium oxides to their crystalline form, which ultimately impacts the adsorption capabilities of sediment. However, limited research has been conducted in this field previously. Sediments from the Weiyuan River, Baoenqiao Reservoir, and Honghu Lake in China were pretreated using freeze-drying, air-drying, and oven-drying methods. The effects of pretreatment methods on P were evaluated through P fractionation and isothermal adsorption experiments. The study also investigated the proportion and amount of amorphous iron and aluminium (Fe_ox and Al_ox) transformed into crystalline forms.

Recent Findings

The results revealed that drying pretreatment markedly increased the potentially bioavailable P(BAP) (6.73%). This increase can be attributed to the rise in loosely-bound P (48.30%) and P bound to metal oxides (9.51%), which are predominant contributors to BAP. Furthermore, sediment adsorption performance significantly decreases after drying pretreatment. This is due to the reduced content of Fe_ox (64.02%) and Al_ox (36.61%), which exhibit higher P adsorption capacity. Additionally, drying led to a significant reduction in SP_max (25.09%) and PSI (28.20%), along with an increase in EPC₀ (24.96%) and DPS (6.83%).

Summary

Different drying treatments affected the P forms and sorption properties of the sediment to varying degrees, with the overall effect being oven-drying > air-drying > freeze-drying > fresh samples. Consequently, when fresh sediment is not available for laboratory analysis, freeze-drying may be a more realistic method for characterizing P properties.

Graphical Abstract