Phosphorus sorption by freeze-thaw treated wetland soils derived from a winter-cold zone (Sanjiang Plain, Northeast China).

摘要

Little attention has been given to the influence of freezing on P cycling in wetlands. The purpose of this study was to explore the effects of freeze-thaw treatments on the P sorption properties of wetland soils, and to determine possible further impact on P retention in wetland soils. In laboratory incubations, six surface soils with varying amounts of P added (0-320 mg P L-1), was continuously frozen at -15 degrees C for 13 h, and then thawed at +5, +15 and +25 degrees C for 10 h, finally refrozen and thawed again for 6 cycles. The freezing effects were quantified by comparisons with control samples. The results demonstrated that freeze-thaw of wetland soils can significantly increase sorption of P at a certain temperature range (5-15 degrees C), consequently, the wetland soils will have much more buffering capacity after freeze-thaw cycles. The P sorption maximum for the six soils were 1770-2577, 1847-2533, and 2093-2810 mg kg-1 for +5 degrees C to +15 degrees C and +25 degrees C, respectively. In addition, P sorption maximum of the controls were 1550-2427, 1736-2463, and 1724-2757 mg kg-1, respectively. The effects of freeze-thaw cycles on P appear to be more pronounced in soils containing a lot of organic matter or clay..