城市新城区公园沟塘沉积物磷释放风险及影响因素分析

Release Risk of Phosphorus by Sediments and Its Influencing Factors in Ponds and Ditches of a New Urban District Park

以合肥蜀峰湾体育公园5个水塘和3条沟渠为对象,采集表层沉积物及上覆水样,测算不同季节表层沉积物磷平衡浓度(EPC0),并解析其对外源碳或氮添加的响应,据此评估沉积物磷释放风险水平,识别主要环境影响因素.结果表明,该城市公园沟塘沉积物磷素污染处于轻-中度污染水平,总磷(TP)含量为209.28~713.51 mg·kg^(-1),生物有效磷含量占TP的质量分数为18.51%~36.21%;环境背景情形下水塘沉积物EPC0变化范围为0.012~0.142 mg·L^(-1)(均值0.057 mg·L^(-1)),沟渠EPC0变化范围为0.036~0.156 mg·L^(-1)(均值0.078 mg·L^(-1));外源碳的添加导致水塘1、3和沟渠1的EPC0值升高(其中水塘3上升约47.5%),提高了沉积物磷释放风险,其余沟塘沉积物EPC0值则出现下降(特别是水塘5下降约58.6%),意味着磷释放风险水平下降;而在外源氮添加情形下,所有沟塘沉积物EPC0值都出现了不同程度的下降(沟渠1、2的夏季情形除外),特别是水塘2表现尤为显著(下降约51.6%),表明沟塘沉积物磷吸收存在氮限制性;根据偏最小二乘回归分析(PLSR)结果,氮、磷对水塘和沟渠沉积物的EPC0值影响存在差异.

This study examined five ponds and three ditches in the Shufengwan Sports Park in a new urban district of Hefei City,from which surface-layer sediments and overlying water samples were collected during autumn,winter,and summer. The equilibrium phosphate concentrations( EPC0) of the sediments and its response to exogenous carbon or nitrogen were then measured. The resulting EPC0 values were used to assess the risk of phosphorus release by the sediments. Finally,major factors influencing phosphorous release were identified using the Partial Least Squares Regression( PLSR) method. The sediments in the urban park exhibited a light-tomoderate level of phosphorous pollution,with the total phosphorus content( TP) ranging from 209. 28 to 713. 51 mg·kg^(-1) and biologically available phosphorus accounting for 18. 51%-36. 21% of the total phosphorus content. Under ambient background,the EPC0 values in pond sediments were 0. 012-0. 142 mg·L^(-1),with a mean value of 0. 057 mg·L^(-1),while in ditches the values ranged from 0. 036 to 0. 156 mg·L^(-1) with an average value of 0. 078 mg·L^(-1). The addition of exogenous carbon increased the EPC0 values( by approximately 47. 5% in pond 3),and thus increased the risk of phosphorus release from sediments,in pond 1,3,and ditch 1.However,EPC0 values of the other ponds and ditches decreased( in particular,by approximately 58. 6% in pond 5),indicating that the risk of phosphorus release decreased. After the addition of exogenous nitrogen,the EPC0 values of almost all ponds and ditches declined to varying degrees( except in ditches 1 and 2 during the summer). In particular,in the EPC0 value of pond 2 declined by approximately 51. 6%. The declining values imply that nitrogen was a limiting factor in phosphorus uptake by sediments in ponds and ditches. According to the results of PLSR,nitrogen and phosphorus had different effects on the EPC0 values of sediments in ponds and ditches.