Phosphorus Adsorption Potential And Release Risk Of Sediments In Ponds And Ditches In A New Urban District Park

Most of the urban landscape waters have the defects of poor liquidity and weak self-purification ability,which makes this type of water body easily polluted by nitrogen and phosphorus and leads to the deterioration of water quality,or even eutrophication.In order to meet the needs of water environment protection of landscape waters in new urban area,in this paper,surface sediments and overlying water samples were collected from 5ponds and 3 ditches of Shufengwan Sports Park in Hefei City.The phosphorus forms of surface sediments in different seasons were analyzed.The phosphorus biological and non-biological adsorption potential and their relative contributions were measured.The effects of exogenous carbon and nitrogen concentration gradient on biological and non-biological adsorption potential were analyzed.The effects of exogenous carbon and nitrogen on the risk of phosphorus release were also evaluated.Finally,their major influencing factors were identified by using Partial Least Square Regression（PLSR）method.The main research results are as follows:（1）In Shufengwan Sports Park,the average of TP content in ponds and ditches were333.09 and 529.10 mg×kg^-1 respectively,and the average of biologically available phosphorus content were 90.61 and 187.72 mg×kg^-1 respectively;the average of TP and TN pollution index in ponds were 0.802 and 1.325 respectively,which belonged to light pollution;while that in ditches were 1.374 and 1.627 respectively,which belonged to moderate pollution.（2）Under ambient background,the average of biological adsorption potential(SPU_biotic)values of sediments in ponds and ditches were 1.333 and 1.354μg×（g×h）^-1 respectively,and the average of non-biological adsorption potential(SPU_kill)values were 7.504 and5.795μg×（g×h）^-1 respectively.Phosphorus adsorption of sediments in ponds and ditches was mainly non-biological adsorption.The effect of exogenous carbon and nitrogen concentration gradient on SPU_biotic was more obvious than on SPU_kill.The difference analysis shows that the difference of SPU_biotic in different seasons was more significant than SPU_kill,but the difference of SPU_kill in different waters was more significant than SPU_biotic.（3）The addition of exogenous carbon concentration gradient led to the increase of SPU_biotic values in ponds 2,5 and ditch 3(especially in pond 5,which increases by about 83%with 100 mg×L^-1 sodium acetate added);the decrease of SPU_biotic values in ponds 1,3,ditch1and some seasons of ditch 2(particularly in pond 3,which decreases by about 58%with400 mg×L^-1 sodium acetate added);SPU_biotic values of the remaining ponds and ditches first increased and then declined with the increase of exogenous carbon concentration.（4）The addition of exogenous nitrogen concentration gradient led to the increase of SPU_biotic values in ponds 1,2,5 and ditch 3(especially in pond 2,which increases by about218%with 250 mg×L^-1 potassium nitrate added);the decrease of SPU_biotic values in ditch 1,2 in winter（particularly in ditch 2,which decreases by about 67%）;SPU_biotic values of the remaining ponds and ditches first increased and then declined with the increase of exogenous nitrogen concentration.（5）Under ambient background,the range of EPC₀ values of sediments in ponds was0.012-0.142 with a mean value of 0.057 mg×L^-1,and the range in ditches was 0.036-0.156with an average value of 0.078 mg×L^-1.The addition of exogenous carbon led to the increase of the EPC₀values in pond 1,3 and ditch 1（in which pond 3 increased by about47%）.However,EPC₀values of the left ponds and ditches decreased（in particular,pond 5decreased by about 51.6%）.In the case of exogenous nitrogen addition,EPC₀values of almost all ponds and ditches showed decline in different degrees（except in the summer of ditch 1,2）,（especially in pond 2,which decreases by about 51.6%）,implying that there were nitrogen restrictions in phosphorus uptake of sediments in ponds and ditches.（6）According to the results of PLSR,nitrogen and phosphorus had different effects on the SPU_biotic and EPC₀values of sediments in ponds and ditches.