景观水体上覆水硝态氮浓度对沉积物中磷释放的影响

Effects of nitrate nitrogen concentration in overlying water on phosphorus release from sediments in landscape water

通过为期60 d的静态模拟试验,探究再生水回用于景观水体时硝态氮浓度对沉积物中磷释放的影响。结果表明:上覆水较高的硝态氮浓度可提高水体氧化还原电位(ORP),降低沉积物脱氢酶活性(DHA)并抑制Fe2+的生成,从而抑制缺氧条件下铁吸附态磷(BD-P)还原造成的内源磷释放。硝态氮作为电子受体,可降低间隙水中总磷(TP)和磷酸盐浓度以及沉积物中易释放态磷(弱吸附态磷(NH4Cl-P)和有机磷(NaOH-nrP))的含量,从而根本上降低内源磷释放潜力和速率。当上覆水中硝态氮质量浓度为7.50 mg/L时,沉积物中磷释放可以得到有效控制,相较不添加硝态氮的对照组,上覆水中TP和磷酸盐质量浓度平均降幅分别达79.2%、83.9%。因此,当再生水回用于景观水体时,硝态氮浓度无需过度控制,不仅可大幅降低制水成本,而且上覆水中较高的硝态氮对沉积物中磷释放具有较好的控制效果。

In order to explore the effect of nitrate nitrogen concentration on phosphorus release from sediments when reclaimed water was reused in landscape water,a 60-day static simulation experiment was carried out.The results showed that higher nitrate nitrogen concentration in overlying water could increase the oxidation reduction potential(ORP),decrease the dehydrogenase activity(DHA)and inhibite the formation of Fe 2+,thus inhibiting the release of internal phosphorus caused by the reduction of iron adsorbed phosphorus(BD-P)under anoxic condition.Meanwhile,nitrate nitrogen could be used as electron acceptor to reduce TP and phosphate concentration in interstitial water and the contents of easily released phosphorus(weakly adsorbed phosphorus(NH 4Cl-P)and organic phosphorus(NaOH-nrP))in sediments,reducing the release potential and rate of internal phosphorus fundamentally.In addition,when the mass concentration of nitrate nitrogen in overlying water was 7.50 mg/L,the release of phosphorus from sediments could be effectively controlled,and the average removal rates of TP and phosphate in the overlying water were 79.2% and 83.9% respectively,compared with those in control group.Therefore,when the reclaimed water was reused in the landscape water,the higher nitrate nitrogen concentration does not need to be excessively controlled,which can not only greatly reduce the cost of water treatment,but also control the phosphorus release from sediments.