The release behavior of inorganic nitrogen and phosphorus in sediment during disturbance

Sediments and surface water were sampled in a tide flat in the Huiquan Bay, Qingdao, China in January 2004 to simulate the exchange of NH4-N/NO3-N/ PO 43- between sediments and surface water. A working system was designed with which samples were shaken at 60, 120 and 150 revolutions per minute (r/min). Experiment results show that NH4-N concentration in water at shaking rate of 60r/min decreased gradually, while at 120r/min increased gradually. In resuspension, fine-grained sediments contributed most NH4-N to the seawater, followed by medium-grained and coarse-grained sediments. The NO3-N concentration in water had a negative relation with the shaking rate; the medium-grained sediments contributed more NO3-N to seawater than the coarse-and fine-grained sediments. The PO 43- concentration is positively related with the shaking rate, the fine-grained sediments were the main N and P contributor to the seawater, followed by medium-and coarse-grained sediments.

黏土矿物对风化壳淋积型稀土矿浸矿剂中NH^(+)_(4)的吸附和脱附特性研究

为了消除风化壳淋积型稀土矿中残留浸矿剂所导致的环境污染问题,本文研究了风化壳淋积型稀土矿中主要黏土矿物蒙脱土、高岭土和伊利石对稀土浸矿剂中NH^(+)_(4)的吸附和脱附行为和机理,并采用纳氏比色-分光光度法对NH^(+)_(4)进行测定。结果表明,蒙脱土、高岭土和伊利石对NH^(+)_(4)的吸附为单分子层吸附,符合Langmuir模型,且NH^(+)_(4)的最大吸附量分别为5.99 mg/g、0.12 mg/g、1.10 mg/g,风化壳淋积型稀土矿中NH^(+)_(4)的释放源主要来自于蒙脱土和伊利石。解吸附实验结果表明金属离子和去离子水对NH^(+)_(4)的解吸附能力遵循Fe ^(3+)≈Al ^(3+)≥Mg ^(2+)>Ca ^(2+)>K^(+)>Na^(+)>H_(2)O。镁盐解吸附实验结果表明其对黏土矿物上NH^(+)_(4)的解吸附速度快,解吸附率高,同等条件下其对风化壳淋积型稀土矿中残留NH^(+)_(4)的洗脱率大于95%。

贵州草海湿地农田沟渠沉积物氮磷的吸附动力学及影响因素

以草海-湿地农田沟渠系统为研究对象,运用模拟实验的方法,针对沟渠系统对氮磷的截留效用、沟渠沉积物对氮磷的吸附动力学及其影响因素进行了研究。结果表明,湿地农田沟渠系统对TP和TN的截留率分别为66.7%～79.7%和66.0%～76.4%,对NH4+-N的截留率最高,为82.8%～89.3%。沟渠沉积物与太湖、滇池沉积物相比较而言,沉积物对PO4-3-P和NH4+-N吸附平衡时间较长。盐度、[SO42-]和[NO3-]对PO43--P和NH4+-N的吸附都具有一定的抑制作用;而[Ca2+]对两者的影响具有明显的差别:Ca2+对PO43--P的吸附在低浓度下抑制,在高浓度下有促进作用;对NH4+-N的吸附具有明显的抑制作用,且当[Ca2+]浓度为5mg·L-1时吸附量最小。