School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, No.13 Yanta Road, Beilin District, Xi'an, 710055, Shaanxi, China.
College of Chemistry &Materials Science, Northwest University, Xi'an, 710069, China.
Environ Sci Pollut Res Int. 2020 Mar;27(7):7504-7514. doi: 10.1007/s11356-019-07382-2. Epub 2019 Dec 28.
Sediment is an endogenous pollution source, which often leads water systems to eutrophication due to the release of nutrients, especially phosphorus (P). Calcium nitrate (CN) was dosed to the water systems under different modes to control P release from the sediments in this study. A 63-day static laboratory test was conducted to explore the effects of intermittent dosing and one-time dosing modes of CN on P locking in the sediment and the concentrations of nitrogen (N) and P in waters. Results showed that 89% total phosphorus (TP) in the overlying water and 91% TP in the interstitial water of sediment were reduced in the intermittent dosing reactor, which were 4% and 13% higher than those in the one-time dosing reactor, respectively. Thus, the concentration of TP in the overlying water of the dosing reactors was both below 0.1 mg/L during the whole experiment. Meanwhile, the mean values of oxidation-reduction potential (ORP) in the sediment increased to - 110.7 ± 42.02 mV when CN was added intermittently, which were significantly higher than those of the one-time dosing reactor (- 158.3 ± 44.61 mV) and control reactor (- 320.7 ± 0.05 mV). Compared with one-time dosing mode, the intermittent dosing not only reduced the maximum concentrations of NO-N from 9.21 to 1.79 mg/L and NO-N from 92.42 to 27.58 mg/L but also shorten their retention time in the overlying water, which might depress the toxic threats to aquatic animals in water environments. Therefore, the intermittent dosing of CN could not only improve the P locking effect but also minimize the risks to aquatic animals in water environments under the premise of reasonable dosage selected. In a word, this research provided an effective operation mode for locking P with CN in the heavily polluted water bodies, which is also advantageous to avoid toxic threats to aquatic animals in water environment.
沉积物是一种内源性污染源，由于释放养分，特别是磷（P），常常导致水系富营养化。本研究采用硝酸钙（CN）以不同方式投加到水系统中，以控制沉积物中磷的释放。进行了为期 63 天的静态实验室测试，以探讨 CN 的间歇投加和一次性投加方式对沉积物中磷固定和水体中氮（N）和磷（P）浓度的影响。结果表明，间歇投加反应器中上层水总磷（TP）的 89%和沉积物间隙水中 TP 的 91%得到了去除，分别比一次性投加反应器高 4%和 13%。因此，整个实验过程中，投加反应器上层水中 TP 的浓度均低于 0.1mg/L。同时，当 CN 间歇投加时，沉积物中的氧化还原电位（ORP）均值增加到-110.7±42.02 mV，明显高于一次性投加反应器（-158.3±44.61 mV）和对照组（-320.7±0.05 mV）。与一次性投加方式相比，间歇投加不仅将 NO-N 的最大浓度从 9.21mg/L 降低到 1.79mg/L，将 NO-N 的最大浓度从 92.42mg/L 降低到 27.58mg/L，而且缩短了它们在上层水中的停留时间，从而可能降低对水生动物的毒性威胁。因此，在合理投加剂量的前提下，CN 的间歇投加不仅可以提高磷的固定效果，而且可以最大限度地降低水生动物在水环境中的风险。总之，本研究为在污染严重的水体中用 CN 固定磷提供了一种有效的运行方式，也有利于避免对水生动物的毒性威胁。
