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景观水体尤其是城市景观水体大多为静态、流动性较差的封闭式缓流水体,具有水域面积小、水环境容量小、自净能力差、易受污染等特点,往往面临风险较高的水质恶化等问题[1-3]。底泥氮磷营养盐的释放是造成水体内源污染的重要因素,控制景观水体及沉积物内部污染物负荷已成为景观水体治理的关键。
原位处理技术和异位处理技术在景观水体底泥处理中运用广泛。物理方法比如底泥疏浚是最直接、有效的异位内源污染治理技术,可快速将受污染的沉积物从水体中清除,增加水体容量、改善水质情况;但其后续底泥处理量大、运输困难,工艺流程复杂且资源化利用有限,在时间空间上具有很大限制,成本高且不易操控[4],还存在破坏水底生态系统平衡,易造成二次污染等风险。投加化学试剂 (如铁铝盐、过氧化钙、锁磷剂等) 是常见的原位化学方法,能紧急修复污染水质,但是有增加水体毒性的可能性[5-7]。底泥覆盖是常见的原位物理处理技术,国外已有将覆盖技术成功应用于治理受污水体的案例[8-10],我国学者也开展相关研究。在近年研究中,天然矿物由于具有价格低廉、来源较广等优点,被广泛应用于实际污染底泥的治理中[11],如方解石、沸石、石灰石、白云石、伊利石、麦饭石等。这些材料应用于覆盖底泥中,对抑制氮、磷释放效果明显,清洁土壤比如红壤也由于良好的絮凝吸附性能、分布较广等优点被逐渐用于水体治理中[12]。学者普遍认为,底泥中存在着大量的可生物利用的营养物质, 这些营养物质可被生物通过生命代谢活动进行吸附、降解、转化,从而促进其生长[13-14] ,污染底泥资源化在水生态处理中有良好的运用前景。沉水植物可利用底泥中的N、P营养盐,还可通过影响微生物的代谢来影响营养物质的循环,在稳定生态系统和净化水体方面有特殊作用。
针对水体污染程度、地理位置等情况,选用处理效果好且经济效益高的底泥改造材料很有必要。紫色母岩是一种自然沉积岩,在西南地区广泛分布,矿物成分较砾石复杂,过去的研究大多集中在紫色母岩风化物理颗粒变化和破碎成土[15-16]、土壤营养肥力[17]等反面。近年来,对紫色母岩的研究逐渐深入到了其吸附性能方面。黄雪娇等[18]发现使用重庆地区常见的蓬莱镇组、沙溪庙组、飞仙关组和遂宁组紫色母岩作基质均能有效降低水体氮磷及有机物含量,其中蓬莱镇组效果最佳。石灰石(主要成分CaCO3)是人工湿地的常用的天然矿物基质,对水体污染物有很好的去除作用[19]。白云石(主要成分CaMg(CO3)2)与石灰石结构相似,被应用于水体治理中,是低成本的除磷材料[20]。
微生物是水生态环境中重要的组成部分,在氮、磷营养盐消减过程中发挥着重要作用[21-22],水环境也会影响微生物群落结构或丰度,了解微生物在水体氮磷变化中的分布特征、生态功能和作用等对水环境修复有重要意义。过去许多研究多集中在改造材料提高底泥吸附性能或者对沉水植物的生理生态影响上[23-25],而结合水环境物化性质变化与微生物群落结构变化的研究较少。为此,本研究选取蓬莱镇紫色母岩、石灰石、白云石作为底泥改造材料,通过阶段性的水质监测分析不同改造材料对水体氮磷去除效果及差异,结合水体元素质量浓度变化和微生物群落结构变化探讨差异的原因,以期评估出低耗高效的底泥改造材料,并在一定程度上丰富底泥改造的应用基础理论,同时为同类型污染水体底泥改造材料的选择提供参考。
底泥-苦草系统对景观水体氮磷的去除效果及其中微生物群落的结构变化
Nitrogen and phosphorus removal effect of sediment-Vallisneria natans system on landscape water and changes of microbial community structure
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摘要: 底泥-沉水植物-微生物系统在景观水体氮磷消减过程中有关键作用。为缓解底泥氮磷释放压力并探究底泥改造材料的选择与氮磷去除效果之间的联系,选用石灰石、白云石和蓬莱镇组紫色母岩作为改造材料,构建水-底泥-苦草系统,结合水体元素质量浓度和微生物群落结构进行分析。结果表明,底泥改造联合苦草 (sediment modification combined with Vallisneria natans,SMVS) 对上覆水体氮、磷的去除效果相较于未改造处理显著提高 (P<0.05) ,蓬莱镇紫色母岩组处理效果最好,对总磷、总氮的去除率分别达到87.06%、80.96%。上覆水悬浮态颗粒物中微生物群落结构发生改变,在门分类水平上, Actinobacteriota、Bacteroidota丰度在不同改造处理中存在显著差异 (P<0.05) ;在属分类水平上,norank_f_norank_o_Chloroplast、Mycobacterium为优势菌属,Mycobacterium在不同改造处理中存在显著差异 (P<0.05) 。冗余分析结果表明Ca、Mg是驱动上覆水氮磷营养盐降低的主要元素。蓬莱镇组紫色母岩作为底泥改造材料对氮、磷的去除效果优于石灰石和白云石,这与向上覆水中释放微量元素含量不同,进而改变了微生物群落结构有关。本研究结果可为景观水体污染底泥的治理提供参考。Abstract: The sediment-Submerged macrophytes-Microbial system plays a key role in the reduction of nitrogen and phosphorus in the nitrogen and phosphorus reduction process of in landscape water. In order to alleviate the nitrogen and phosphorus release pressure of sediment and explore the relationship between the selection of sediment transformation materials and the effect of nitrogen and phosphorus removal, limestone, dolomite and purple parent rock of Penglaizhen Formation were selected as the transformation materials to construct a water-sediment- Vallisneria natans system, which was analyzed by combining the mass concentration of water elements and microbial community structure. The results showed that the removal effect of sediment modification combined with Vallisneria natans (SMVS) was significantly higher than that of the overlying water body (P<0.05), and the treatment effect of Penglaizhen Formation was the best with the removal rates of TP and TN at 87.06% and 80.96%, respectively. The microbial community structure in the overlying aqueous suspended particulate matter had changed, and the abundance of Actinobacteriota and Bacteroidota was significantly different in different modification treatments at the taxonomic level (P<0.05). At the genus taxonomic level, there were significant differences between norank_f_norank_o_Chloroplast and Mycobacterium in different modification treatments (P<0.05). The results of redundancy analysis showed that Ca and Mg were the main elements driving the reduction of N and P of overlying. The removal effect of purple parent rock in Penglaizhen Formation as a sediment modification material was better than that of limestone and dolomite, which was related to the release of trace elements in upward overlying water and the change of microbial community structure. The research results can provide reference for the treatment of sediment polluted by landscape water.
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表 1 改造材料基本性状
Table 1. Basic properties of sediment and modified materials
材料 TN/(g·kg−1) TP/(g·kg−1) 有机质/(g·kg−1) SiO2 /(g·kg−1) Al2O3 /(g·kg−1) Fe2O3 /(g·kg−1) CaO /(g·kg−1) MgO /(g·kg−1) pH 石灰石 0.12 2.55 0.57 40.2 9.7 2.1 524.2 9.6 8.3 白云石 0.10 2.07 0.85 6.4 2.7 1.9 575.5 470.3 8.6 蓬莱镇组母岩 0.58 9.43 11.36 653.6 138.1 20.1 27.3 5.8 8.0 表 2 上覆水体元素含量
Table 2. Elemental content of overlying water bodies
处理 As/
(µg·L−1)Cd/
(µg·L−1)Co/
(µg·L−1)Cu/
(µg·L−1)Fe/
(µg·L−1)Hg/
(µg·L−1)Mn/
(µg·L−1)Ni/
(µg·L−1)Mo/
(µg·L−1)B/
(µg·L−1)K/
(mg·L−1)Ca/
(mg·L−1)Mg/
(mg·L−1)T1 15.53±
10.25a13.06±
10.57a8.33±
3.03a5.40±
2.79a2.40±
1.90a15.50±
8.41a3.17±
1.08a18.50±
1.27ab13.37±
2.33a89.40±
17.29a4.11±
0.13a22.95±
0.02b10.13±
0.06bT2 12.47±
6.52a15.34±
13.33a0.63±
0.63b4.23±
1.19a2.50±
0.50a— 3.50±
1.71a13.63±
3.75ab11.63±
2.24a92.97±
4.66a4.24±
0.06a23.57±
0.27ab10.89±
0.26aT3 14.03±
5.05a7.62±
7.62a5.50±
0.55ab5.93±
3.02a— — 4.00±
1.97a10.13±
4.66b8.33±
2.20a89.43±
15.73a4.13±
0.10a23.55±
0.06ab11.19±
0.09aT4 15.87±
6.29a— 6.47±
2.47ab3.80±
3.31a1.70±
0.80a— 3.30±
1.15a23.17±
1.24a7.53±
3.82a80.83±
5.07a4.37±
0.05a24.28±
0.45a10.90±
0.07a注:同行不同小写字母表示处理间差异显著 (P<0.05) 。 表 3 细菌群落多样性指数 (OTU水平)
Table 3. Diversity index of bacterial communities(OTU level)
群落编号 Chao1 Shannon Simpson T1 460 3.83 0.085 6 T2 838 5.14 0.013 4 T3 898 5.01 0.017 8 T4 935 5.17 0.014 5 -
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