Linkage between land use patterns and sediment phosphorus sorption behaviors along shoreline of a Chinese large shallow lake (Lake Chaohu)

To test the relationship between phosphorus buffering capacity in sediments of littoral zone and land use, seasonal samples were taken from the soils representing different patterns of land use, together with the littoral zone sediments, along shoreline in Lake Chaohu. There existed significantly positive relationships between equilibrium phosphorus concentration (EPC0) and degree of phosphorus saturation (DPS) defined as ratios of Olsen-P, algae available phosphorus (AAP) and inorganic phosphorus (IP) to maximum sorption capacity (Qmax). So, some easily accessible P parameters especially DPS were indicative of EPC0 in the sediments. Furthermore, the contents of IP, total phosphorus (TP) and organic matter (OM) in the sediments were significantly related to those in the soils. Therefore, the soils could provide the littoral zone with IP either directly or indirectly through TP input; it also provided the Olsen-P through the OM input, as evidenced by the relationship between Olsen-P and OM. It meant that the enhanced OM would enlarge the DPS. On the other hand, the increase in OM paralleled with the increases in Qmax, which lower the DPS simultaneously. Thus, the OM modified sediment phosphorus sorption behaviors in complicated manners. Finally, the soil covered by Fleabane was coupled with the sediment whose EPC0 values were lower and further decreased with strong diffusion from the soils after heavy rains. Hence, shoreline soil may input TP including IP and OM into the lake and alter the DPS together with EPC0 thereby regulating the sediment functions to act as sink or source of phosphorus.