Study On Soil Phosphorus Reservoir And Adsorption Characteristics In Wetland Of The Fenhe Park In Linfen

Sediments and wetland soil samples were collected from the Fenhe Park in Linfen city.The distribution of soil phosphorus in the Park with different sampling areas and vegetation types were analyzed.Combined with water quality,the phosphorus release risk index（ERI）was used to evaluate the potential water eutrophication risk level induced by soil phosphorus release.The correlation between the forms of phosphorus and ERI were monitored.Sampling analysis is as follows:（1）The content of total inorganic phosphorus（TP）in the sediment,near water area and buffer area of the Park ranged from 96.73-397.03 mg/kg,accounting for 31.27-39.85%of the TP.The total inorganic phosphorus（IP）content in buffer zone and sediment was significantly higher than that in near water zone.The proportion of each inorganic phosphorus component in IP was potential phosphorus source（64.18%-88.48%）>slow effective phosphorus source（20.47%-28.99%）>effective phosphorus source（2.33%-7.00%）.The content of IP ranged from 249.24 mg/kg to 352.11 mg/kg in different vegetation types,and the difference was not significant.The content of IP and TP content was no significant change between 0-20 cm and 20-40 cm soil layers.The content of Ca₈-P in0-20 cm soil layer was significantly higher than that in 20-40 cm soil layer.There was no significant difference in other forms of inorganic phosphorus between 0-20 cm and 20-40 cm soil layers.The correlation analysis showed that Ca₂-P,Ca₈-P,Al-P and Fe-P were positively correlated with available P,which affected the availability of soil phosphorus.（2）The content of total organic phosphorus（OP）in the sediment,near water area and buffer area of the Park ranged from 14.19 mg/kg to 98.22 mg/kg,accounting for5.74-8.22%of the TP.The OP content in near water zone and sediment was significantly higher than that in buffer zone.The content of OP ranged from 34.26 mg/kg to 108.01 mg/kg in different vegetation types,indicating that Phragmites australis was significantly higher than other vegetation types.The proportion of each organic phosphorus component in OP was Na OH-P_o>Na HCO₃-P_o>HCl-P_o>H₂O-P_o.Each organic phosphorus component was no significant difference between 0-20 cm and 20-40 cm soil layer.The content of residual P（R-P）in sediment,near water area and buffer area of the Park is 132.98 mg/kg to 896.45mg/kg,accounting for 55.16%-61.72%of total phosphorus,which is significantly higher than IP,and than OP.R-P content was significantly higher than that of 0-20 cm soil layer in Trifolium Linn and Punica granatum L.,indicating that R-P accumulated in the lower layer of soil.（3）The Langmuir model can be used to fit the adsorption isotherms of sediments,soils near water and buffer zones in the Park,and the fitting coefficients are 0.9969-0.9980.According to the assessment of phosphorus release risk in various areas of the Park,the risk of phosphorus release in the sediment and buffer zone was found to be low,and the soil in the near water area was moderate release risk.The ratio of critical equilibrium phosphorus concentration（EPC₀）in sediment and near water area to phosphorus content in overlying water body was calculated respectively.It was found that the"source"of phosphorus changed from near water area with upstream to sediment with downstream.The release level was changed from moderate release risk to low release risk,which indicated that the risk of phosphorus release decreased with soil particles gradually deposited.With the settlement of soil particles,phosphorus was released to the overlying water,which affected the phosphorus content of overlying water.Correlation analysis showed that there was a significant positive correlation between ERI and Ca₂-P,Al-P,Fe-P,Na HCO₃-P_oand Na OH-P_o,indicating that available phosphorus source,slow available phosphorus source,soil potential active organic phosphorus and soil Fe/Al bound organic phosphorus were easily to enter water body with soil erosion.