Background

Achieving nitrogen (N) and phosphorus (P) control in sediment remediation projects by adding natural materials is receiving increasing attention. In this study, different natural materials, including iron-rich clay minerals, calcite, kaoline, sugarcane bagasse and Phragmites detritus, were applied to test their effects on N and P in a mesocosm experiment.

Results

Iron-rich clay minerals and Phragmites detritus had obvious advantages for P control; they resulted in almost undetectable levels of soluble reactive phosphorus (SRP) in the water column throughout the experiment. This finding can be explained by their strong P adsorption ability. The high level of available organic carbon in the sediment and water column after sugarcane bagasse addition provided enough electron donors for denitrification and dissimilatory nitrate reduction to ammonium (DNRA), which caused nitrate (NO₃⁻-N) deficiency and ammonium (NH₄⁺-N) accumulation in the water column. Additionally, this resulted in anaerobic conditions, further fuelling the release of P from iron-bound P induced by anoxia. Thus, the amount of sugarcane bagasse applied should be considered carefully in order to balance denitrification and DNRA as well as P releases. Calcite and Phragmites detritus are recommended as remediation materials for N removal based on their significant promotion of denitrification and limitation of DNRA, which resulted in low NO₃⁻-N and NH₄⁺-N levels. These results can be explained by the shifts in the functional microbial community composition and abundance after the addition of natural materials.

Conclusions

Iron-rich clay minerals and Phragmites detritus are promising sediment remediation materials for P immobilization due to their strong P adsorption ability. Taken together, the selection of sediment remediation materials should consider the N and P coupling relationship, to prevent NO₃⁻-N removal from causing P leaching or NH₄⁺-N accumulation.

中文翻译：

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天然物质作为沉积物修复对中观磷和氮控制的影响

背景

通过添加天然材料来实现泥沙治理项目中的氮（N）和磷（P）控制越来越受到关注。在这项研究中，采用了多种天然材料，包括富铁粘土矿物，方解石，高岭土，甘蔗渣和芦苇碎屑，在中观试验中测试了它们对氮和磷的影响。

结果

富铁粘土矿物和芦苇碎屑在控制磷方面具有明显的优势。在整个实验过程中，它们导致水柱中的可溶性活性磷（SRP）含量几乎检测不到。这一发现可以用它们强大的P吸附能力来解释。添加甘蔗渣后，沉积物和水柱中高水平的可用有机碳为反硝化和硝酸盐异化还原为铵盐（DNRA）提供了足够的电子供体，这导致硝酸盐（NO ₃ ^-- N）缺乏和铵盐（NH ₄ ⁺-N）积聚在水柱中。另外，这导致了厌氧条件，进一步加剧了磷从缺氧诱导的铁结合磷中释放出来。因此，应仔细考虑所施用甘蔗渣的量，以平衡反硝化作用，DNRA以及磷的释放。由于方解石和芦苇碎屑的显着促进反硝化作用和限制DNRA的作用，因此建议将其作为脱氮的补救材料，从而降低NO ₃ ^-- N和NH ₄ ⁺ -N的含量。这些结果可以通过添加天然物质后功能性微生物群落组成和丰度的变化来解释。

结论

富含铁的粘土矿物和芦苇碎屑因其强大的P吸附能力而成为有望实现P固定化的沉积物修复材料。综合考虑，沉积物修复材料的选择应考虑N和P的耦合关系，以防止NO ₃ ^-- N的去除引起P淋溶或NH ₄ ⁺ -N的积累。