Laboratório de Biogeoquímica Ambiental/Núcleo de Estudos, Diagnósticos e Intervenções Ambientais, Departamento de Química, Universidade Federal de São Carlos, São Carlos (SP), Brazil.
Water Res. 2012 Dec 1;46(19):6463-75. doi: 10.1016/j.watres.2012.09.018. Epub 2012 Sep 16.
The main objective of this study was to perform laboratory experiments on calcium nitrate addition to sediments of a tropical eutrophic urban reservoir (Ibirité reservoir, SE Brazil) to immobilize the reactive soluble phosphorus (RSP) and to evaluate possible geochemical changes and toxic effects caused by this treatment. Reductions of 75 and 89% in the concentration of RSP were observed in the water column and interstitial water, respectively, after 145 days of nitrate addition. The nitrate application increased the rate of autotrophic denitrification, causing a consumption of 98% of the added nitrate and oxidation of 99% of the acid volatile sulfide. As a consequence, there were increases in the sulfate and iron (II) concentrations in the sediment interstitial water and water column, as well as changes in the copper speciation in the sediments. Toxicity tests initially indicated that the high concentrations of nitrate and nitrite in the sediment interstitial water (up to 2300 mg L(-1) and 260 mg L(-1), respectively) were the major cause of mortality of Ceriodaphnia silvestrii and Chironomus xanthus. However, at the end of the experiment, the sediment toxicity was completely removed and a reduction in the 48 h-EC50 of the water was also observed. Based on these results we can say that calcium nitrate treatment proved to be a valuable tool in remediation of eutrophic aquatic ecosystems leading to conditions that can support a great diversity of organisms after a restoration period.
本研究的主要目的是在巴西东南部热带富营养城市水库（伊比里特水库）的沉积物中进行添加硝酸钙的实验室实验，以固定活性可溶磷（RSP），并评估这种处理可能引起的地球化学变化和毒性效应。在添加硝酸盐 145 天后，水柱状和间隙水中的 RSP 浓度分别减少了 75%和 89%。硝酸盐的应用增加了自养反硝化的速率，导致添加的硝酸盐的 98%被消耗，99%的酸挥发性硫化物被氧化。因此，沉积物间隙水和水柱状中的硫酸盐和铁（II）浓度增加，沉积物中的铜形态也发生了变化。毒性测试最初表明，沉积物间隙水中高浓度的硝酸盐和亚硝酸盐（分别高达 2300mg/L 和 260mg/L）是导致刺尾虫和摇蚊死亡的主要原因。然而，在实验结束时，沉积物的毒性完全消除，水的 48 小时-EC50 也降低了。基于这些结果，我们可以说，硝酸钙处理被证明是修复富营养水生生态系统的一种有价值的工具，可在恢复期间为支持更多种类的生物提供条件。
