Abstract:

The extensive use of nickel oxide nano-particles (NiO NPs) led to their widespread presence in the environment and potential ecological risks. These particles can enter constructed wetlands (CWs) through sewage, thereby posing stress on ecological factors and affecting CW performance. This study investigated the effects of 10 and 30 mg∙L⁻¹ NiO NPs on operational characteristics and microbial communities in vertical-flow CWs. Results indicated that NiO NPs promoted the removal of organic matter, nitrogen, and phosphorus to a certain extent, with increases of the removal rates for COD, NH₄⁺-N, TN, and TP reaching 5.24%-20.8%, 53.0%-66.4%, 7.72%-34.7%, and 56.0%-68.9%, respectively. However, at a concentration of 30 mg∙L⁻¹ NiO NPs, denitrification was significantly suppressed and NO₃⁻-N removal was 44.7%-64.4% lower than conditions without NiO NPs. The relative activities of key enzymes, including dehydrogenase (DHA), ammonia monooxygenase (AMO), urease (URE), and phosphatase (PST) were also affected NiO NPs. In particular, DHA and AMO were increased by 2.58%-51.5% and 46.7%-76.4%, respectively, whereas URE activity increased sharply by 225%-460%. Additionally, NiO NPs had the potential to enhance phosphatase (PST) activity, except during the early period of exposure to 10 mg∙L⁻¹ NiO NPs. Relative activity of PST increased by 11.1%-93.1% compared to that before dosing, consistent with the boost of TP removal. Furthermore, NiO NPs caused changes in the microbial community structure in the CWs. NiO NPs treatment reduced the abundance of Chloroflexi, Acidobacteria, Gemmatimonadetes, Nitrospirae, and other phyla, as the NiO NPs concentration changed. The relative abundance of Proteobacteria, a key denitrification phylum, decreased by 7.98% under 30 mg∙L⁻¹ NiO NPs stress. With respect to functional bacteria, stimulation on Nitrosomonas (ammonia-oxidizing bacteria) under NiO NPs exposure might promote NH₄⁺-N removal. Nevertheless, NiO NPs caused drop of Nitrospira (nitrite-oxidizing bacteria) by 84.0%-91.7%. Meanwhile, NiO NPs inhibited denitrifying bacteria, including Dechloromonas, Hydrogenophaga, and Zoogloea, whereas, phosphate accumulating organisms such as Gemmobacter and Acinetobacter were stimulated. These changes resulted in reduced NO₃⁻-N reduction and increased TP removal. Results of this study contribute to a better understanding of the micro-ecological responses to NiO NPs stress in CW systems, providing a theoretical basis for the feasibility and stability of treating wastewater in CWs that contains NiO NPs.

Key words: constructed wetlands, operating performance, NiO NPs, nutrients removal, substrate enzyme activity, microbial community structure

摘要：

纳米氧化镍（NiO NPs）的广泛应用导致环境暴露且存在生态风险，其随污水进入人工湿地（CWs）可能对生态因子产生胁迫，从而影响湿地运行性能。考察了垂直流人工湿地在10 mg∙L⁻¹和30 mg∙L⁻¹ NiO NPs暴露下的运行特性和微生物群落响应。结果显示，NiO NPs暴露一定程度上促进了有机物、氮和磷的去除，其中COD、NH₄⁺-N、TN、TP去除率较加药前分别提高5.24%－20.8%、53.0%－66.4%、7.72%－34.7%和56.0%－68.9%。而30 mg∙L⁻¹ NiO NPs暴露显著抑制了反硝化过程，NO₃⁻-N去除率较加药前低44.7%－64.4%。对于关键酶活性，NiO NPs令脱氢酶（DHA）和氨单加氧酶（AMO）相对活性分别降低2.58%－51.5%和46.7%－76.4%，而脲酶（URE）活性则显著提升225%－460%。此外，NiO NPs有促进磷酸酶（PST）活性的潜力，除10 mg∙L⁻¹ NiO NPs暴露前期外，PST相对活性较加药前提高11.1%－93.1%，与TP去除率提升一致。对微生物群落结构而言，NiO NPs降低了绿弯菌门（Chloroflexi）、酸杆菌门（Acidobacteria）、芽单胞菌门（Gemmatimonadetes）、硝化螺旋菌门（Nitrospirae）等微生物门丰度，且具有浓度效应。30 mg∙L⁻¹ NiO NPs令关键反硝化门变形菌门（Proteobacteria）丰度降低7.98%。从功能菌属分析，NiO NPs对亚硝化单胞菌（Nitrosomonas）的刺激可促进NH₄⁺-N去除，而硝化螺旋菌（Nitrospira）则较加药前减少84.0%－91.7%。另外，NiO NPs对脱氯单胞菌属（Dechloromonas）、噬氢菌属（Hydrogenophaga）、动胶菌属（Zoogloea）等反硝化属产生抑制，而刺激了芽殖杆菌属（Gemmobacter）、不动杆菌属（Acinetobacter）等聚磷微生物，进而导致NO₃⁻-N和TP去除率分别降低与升高。该试验的研究结果有助于丰富湿地微生态系统应对NiO NPs胁迫的主要机制，为人工湿地处理含NiO NPs废水的可行性与稳定性提供理论依据。

关键词: 人工湿地, 运行性能, 纳米氧化镍, 营养物去除, 基质酶活性, 微生物群落结构