Heterotrophic nitrification is considered a potentially important N cycling process, contributing to nitrate production in terrestrial ecosystems. The specific impacts of land-use change on this process, and its underlying microbial communities, are not well characterised. Here we report on a study examining the contribution of heterotrophic nitrification to total nitrification in four land use soils (dairy pasture, sheep pasture, long-term cropland and pine forestry), using 15N isotope labelling ((15NH4)2SO4 and 15N-glycine) incubation, a nitrification inhibitor, and molecular techniques. The results showed that the pine forest soil had the highest contribution (>78%) of heterotrophic nitrification to total nitrification, despite having the lowest overall nitrification. The addition of glycine enhanced the contribution of heterotrophic nitrification in cropland compared to dairy and sheep pastures, with this value in cropland being approximately 1.9-fold higher. The contribution of heterotrophic nitrification to total nitrification was positively correlated with soil fungal abundance and the fungi to bacteria ratio, indicating that fungi might be the main contributor of heterotrophic nitrification in the studied soils. Known heterotrophic nitrifiers, Penicillium was a potential candidate to play a significant role in pine forest soil with a relative gene abundance of 9.7%, whereas Mortierella was potentially prevalent in the dairy pasture (12.7%), sheep pasture (19.4%) and cropland (14.0%) soils, suggesting that the composition of potential heterotrophic nitrifiers varied between pine forest and agricultural (pasture and cropland) soils. The filamentous Ascomycota fungus Sagenomella, not previously known to perform heterotrophic nitrification may be a potential heterotrophic nitrifier in the studied forest soil, which warrants further investigation. This research improves our comprehensive understanding of heterotrophic nitrification in different land use soils, important for understanding the nitrogen cycle in different terrestrial ecosystems.

Urban landscape lakes are increasingly at risk of nitrogen-induced eutrophication. Microbial nitrogen transformation plays a crucial role in reducing nitrogen levels in these lakes. However, the relationships between microbial communities, nitrogen functional genes, and nitrogen dynamics in water and sediment, along with their underlying mechanisms, remain unclear. In this study, we systemically investigated the spatial distributions of physicochemical indicators in the overlying water and sediment in a typical urban landscape lake, Zizhuyuan Park, and the microbial communities and nitrogen cycling genes in the surface sediments of the lake connection (CO), side (SI), and center (CE) were evaluated via macrogenetic sequencing technology to analyze their relationships with environmental factors. The results revealed that the concentrations of TN, NO3-, and NH4+ in the lake water were within the ranges of 1.36 similar to 2.84, 0.98 similar to 1.92, and 0.01 similar to 0.29 mg center dot L-1, respectively. The concentrations of TN, NO3-, and NH4+ in the sediments ranged from 1.17 similar to 3.47 g center dot kg(-1), 0.88 similar to 1.94 mg center dot kg(-1), and 5.61 similar to 10.09 mg center dot kg(-1), respectively. The contents of NH4+ in water, TN and NO3- in sediments were significantly different in spatial distribution (p < 0.05). At the CE site, the Shannon diversity index was the highest and differed significantly from the values at the SI and CO sites (p < 0.01).The sediments of Central Lake contained a total of 36 phyla and 1303 genera of microorganisms. Proteobacteria (62.88-64.83%) and Actinobacteria (24.84-26.62%) accounted for more than 85% of the microorganisms. Nitrospirae, Ignavibacteriae, and Bacteroidetes were significantly different (p < 0.05) at the CE, and Planctomycetes were significantly different (p < 0.05) at the CO. The functional gene nrfA exhibited the highest abundance, followed by napA, nosZ, nirS, hao, ureC, norB, nifH, nirK, hdhA, nifB, and amoA. The abundances of hao and nifH differed significantly at various locations in Central Lake (p < 0.05). The key nitrogen transformation processes in the sediments, ranked by contribution rate, were DNRA, denitrification, nitrification, ammoniation, nitrogen fixation, and anammox. The six nitrogen processes showed significant differences (p < 0.01) in spatial distribution. The pH, TN, NO3-, NH4+, C/N ratio of the sediment, and NH4+ in the lake water impact the microbial community and nitrogen conversion process. The sediment should be cleaned regularly, and the water cycle should be strengthened in urban landscape lakes to regulate microorganisms and genes and ultimately reduce nitrogen and control eutrophic water. This study can provide a reference for improving and managing lake water environments in urban landscapes.

Subsoiling is a common practice for improving soil structure and has recently been recognised for its potential to reduce nitrous oxide (N2O) emissions. However, its impact on nitrate (NO3--N) leaching must also be considered if it is to be used as a mitigation strategy. This study investigated N2O emissions, NO3--N leaching and grass yield in an Italian ryegrass pasture soil with a compacted subsoil layer using a lysimeter study. Additionally, a separate field study examined mineral nitrogen (N) concentration and the abundance of nitrifying and denitrifying genes. Both studies have four treatments, with non-subsoiling (NS), subsoiling (SS), non-subsoiling and urine (NSU), subsoiling and urine (SSU), and the urine treatments were applied at a rate of 700 kg N ha(-1). The results showed that 6 months after subsoiling, soil macroporosity in all treatments remained elevated at a depth of 0-20 cm (p < 0.01) compared with all non-subsoiling treatments. This created more aerobic conditions, which suppressed N2O emissions from denitrification by 20.3% (p < 0.05) during 190 days after urine application (NSU vs. SSU). Additionally, subsoiling had no significant effect on NO3--N leaching in the presence of winter-active Italian ryegrass. Molecular analysis of N-cycling microbial communities revealed that subsoiling had no effect on the abundance of amoA gene-carrying microorganisms involved in nitrification but reduced the abundance of nirS denitrifier genes, indicating that subsoiling primarily affected the denitrification process. These findings suggest that subsoiling can effectively reduce N2O emissions without increasing NO3--N leaching when combined with winter-active ryegrass.

Iron (Fe) (hydr)oxides are effective antimony (Sb) adsorbents with limited individual Sb(III) oxidation capacity in natural waters. The coexistence of Mn(II) and Fe (hydr)oxides may significantly promote the oxidation of Sb(III). However, the mechanism of Sb(III) oxidation and adsorption in the presence of Mn(II) and Fe (hydr)oxides remains unclear. Therefore, in the present study, the effect of dissolved Mn(II) on the oxidation and adsorption of Sb(III) in the ferrihydrite/hematite-Mn(II) system under aerobic conditions and the mechanism were comprehensively investigated. The results of kinetic experiments showed that Sb(III) was efficiently removed in the presence of ferrihydrite/hematite and Mn(II). Further characterization confirmed the formation of Mn(III/IV) oxides on the surface of ferrihydrite and hematite, which were the main oxidants for Sb(III) oxidation. However, removal mechanisms were different between the ferrihydrite-Mn(II) system and the hematite-Mn(II) system. The adsorption of Sb was the main cause of Sb(III) removal in the ferrihydrite-Mn(II) system. For the hematite-Mn(II) system, Sb(III) oxidation played a more important role in Sb(III) removal; however, Sb adsorption was inhibited as a result of Mn oxide formation on the hematite surface and the limited adsorption capacity of hematite. Therefore, the present study revealed that Mn(II) and ferrihydrite/hematite were both critical to Sb(III) oxidation and adsorption under aerobic conditions, which may be helpful for a better understanding of Sb migration and transformation in natural waters.

为了探讨利用国产透气膜回收沼液氨氮的可行性及实际效果,以国产管式透气膜为关键组成部件构建沼液氨氮回收工艺模拟实验装置,开展沼液氨氮回收动态实验研究.结果表明:随着透气膜分离氨氮回收实验装置的运行,沼液氨氮浓度总体下降明显,提取液氨氮浓度呈先线性增加而后稳定在一定水平的变化规律;运行396 h后沼液氨氮去除率可达91.2％;根据氨氮回收速率的变化,装置运行过程可分为氨氮回收(0～252 h)和损失(252～420 h)两个阶段;氨氮回收阶段,提取液氨氮浓度小于10000 mg·L-1,单位体积氨氮平均回收速率为1190 mg·L-1·d-1,氨氮损失阶段,提取液氨氮浓度平稳保持在11200～12180 mg·L-1,单位体积氨氮平均回收速率仅为35 mg·L-1·d-1.若要令该工艺更为高效运行,可考虑增强沼液反应槽密封性,以降低沼液中气态NH3的挥发损失,另外可将提取液pH是否超过7确定为是否应更换新提取液的指示参数.利用国产透气膜构建的沼液氨氮回收工艺过程可有效回收沼液氨氮,回收率接近80％.

[目的]针对目前氮肥优化管理的评价方法难以兼顾产量、经济效益、氮肥效率及环境等多目标评价现状,运用层次分析法和熵权法确定指标的权重,并采用综合评价法对玉米氮肥优化管理进行评价.[方法]2018—2019年在东北雨养区开展玉米田间定位试验,试验设5个施氮水平:0?(N0)、75?(N75)、150?(N150)、225(N225)、300?(N300)?kg/hm2.在收获期取样,测定玉米产量、氮肥效率、0—100?cm土壤氮素含量.分析氮肥施用量与玉米产量、边际效益、氮素回收率、氮肥农学效率、氮肥偏生产力、氮素生理利用率、氮素表观平衡和土壤无机氮累积量的关系.以高产高效、农田环境友好为总目标层,将其划分为产量、经济效益、氮肥效益和环境4个准则层,准则层又继续划分为8个要素层,依据试验数据确定每个准则层和要素层的权重系数,将不同氮素处理获得的各要素数据归一化后,计算各处理的综合评价分数.[结果]依据试验数据,产量、经济效益、氮肥效益和环境4个准则层的权重系数分别为0.39、0.29、0.10和0.22.8个要素层及其权重系数依次为产量0.39,边际效益0.29,氮素回收率0.025,氮肥农学效率0.025,氮肥偏生产力0.025,氮素生理利用率0.025,氮素表观平衡0.07,土壤无机氮积累量0.15.依据此权重系数计算施氮量处理的综合得分,2018、2019年N225水平分别为0.81、0.92,N150水平分别为0.67、0.78,N75均为0.67,N300水平分别为0.55、0.53,N0均为0.15.选取综合得分高于0.8的施氮量作为推荐量,得出2018年适宜氮肥施用量为N225 kg/hm2,2019年为N186～225?kg/hm2.[结论]通过分层评估,充分考虑每个目标层的权重,以此对施氮量进行综合评价,得出的适宜施肥量既可满足玉米对氮素的需求,保证玉米获得高产优质,提高氮素利用率,又可降低氮素淋失对环境污染的风险.

研究不同土地利用方式下氮循环相关微生物在不同土壤剖面的分布，可为认识和理解土壤氮转化过程提供科学依据。土壤氨氧化微生物和反硝化微生物在调节氮肥利用率、硝态氮淋溶和氧化亚氮（N 2 O）排放等方面有着重要作用。以北京郊区农田和林地两种土地利用方式为研究对象，分析土壤氨氧化潜势和亚硝酸盐氧化潜势在0—100 cm土壤剖面上的季节分布（春季和秋季）,并通过实时荧光定量PCR方法表征土壤氨氧化和反硝化微生物的时空分布特征。结果表明，农田土壤氨氧化潜势、亚硝酸盐氧化潜势、氨氧化微生物和反硝化微生物丰度均显著高于林地土壤，且随土壤深度增加而显著降低。除氨氧化古菌amoA基因丰度在不同季节间无显著差异外，春季土壤氨氧化细菌（amoA基因）、反硝化微生物nirS、nirK和典型nosZ I基因的丰度均显著高于秋季。土壤有机质、总氮、NH + 4 -N、NO - 3 -N含量与氨氧化微生物和反硝化微生物的功能基因丰度显著相关。综上，不同土地利用方式下土壤氮循环相关微生物的丰度与土壤氮素的可利用性和转化过程紧密相关，研究结果对土壤氮素利用和养分管理提供了重要的参考依据。

Constructed wetlands for antibiotics and heavy metals removal have become important reservoirs of antibiotic resistance genes (ARGs) and heavy metal resistance genes (MRGs), especially in the substrates. Here, substrate-free hydroponic microcosms of Myriophyllum aquaticum were established; tetracyclines (TCs) and Cu(II) were added to evaluate the behaviours of ARGs and MRGs in the microcosms. Several ARGs, MRGs, and mobile genetic elements (MGE) were detected in the biofilms attached to the plants, ranging from 0.5 to 2.3 × 108 copies/g dry weight. ARGs and MRGs exhibited higher relative abundances in the effluent suspended solids (SS); however, their absolute amounts were much lower than those in conventionally constructed wetlands. Microcosms with TCs and Cu(II) exhibited a higher level of resistant genes than those with compound added singularly owing to co-selection pressure. The existence of TCs and copper significantly changed the microbial communities in the microcosms. The exogenous input of TC/Cu(II) and microbial community structure were the factors driving the occurrence of ARGs, whereas MRGs were more correlated with the copper addition. Thus, reducing the exogenous inputs of antibiotics /heavy metals and SS of the effluent is suggested for the mitigation of resistant genes in phytoremediation technologies working in the absence of conventional substrates.

In this work, Illumina MiSeq sequencing of cDNA from metatranscriptomics RNA reverse transcription were employed in combination with phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) to estimate the dynamic variations of bacterial community structures and metabolic functions in a bioreactor and traditional composting process. Results showed that the change of bacterial α-diversity in the first three stages exhibit opposite trends in the two composting systems. The four most abundant phyla were the same in both systems (Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria), but the most abundant genera were different. The five most abundant genus-level groups in the bioreactor were Psychrobacter, Galbibacter, Pseudomonas, Staphylococcus and Flavobacterium. Within the same phase, the functional bacteria were dramatically different in the two composting processes. In the bioreactor system both bacterial community structure and metabolism function were greatly affected by available phosphorus.

The objective of this study was to evaluate the influence of inlet and outlet location and matrix particle size on the hydraulic efficiency of horizontal subsurface constructed wetlands. A quasi-two-dimensional model was set up to evaluate its hydraulic efficiency by salt tracer test, and the change of flow state in the system was observed by dye tracer test. Three inlet and outlet settings: top inlet-bottom outlet, middle inlet-middle outlet and bottom inlet-top outlet; three particle size distributions are 3 mm, 5 mm and 3/5 mm (one half part 3 mm, the other 5 mm). According to the tracer test, the position of inlet and outlet and the size distribution of matrix have an effect on the hydraulic characteristics of constructed wetlands. Larger substrate size with bottom inlet-top outlet configuration could improve hydraulic behaviour, improve water treatment efficiency.

在去除沼液悬浮物(SS)的同时,最大程度地保留其氮素养分是提高沼液资源化利用价值的关键.通过静态吸附-解吸试验筛选出弱吸附氨氮的过滤介质,然后利用滤料填充柱动态过滤试验分析筛选滤料填充柱对沼液SS和氨氮浓度的影响.结果 表明,在海砂(SSD)、沸石(ZLT)、石英砂(QSD)和氧化铝废渣(GRM)4种供试滤料中,QSD对溶液氨氮的吸附能力最低,脱附率接近SSD,且远小于ZLT和GRM.按2.4 L·h-1流量进水,沼液经QSD滤料填充柱动态过滤处理后,SS去除率最高可达86.1％,0.5～1 mm粒径QSD填充柱对SS去除率普遍高于3～5 mm粒径QSD填充柱,两种粒径QSD填充柱对沼液氨氮的去除效果无明显区别;运行24 h时滤料填充柱自进水端开始出现堵塞现象,32 h后3～5 mm粒径QSD填充柱堵塞严重;若要达到沼液SS相同去除效果,0.5～1 mm粒径QSD填充柱较3～5 mm粒径QSD填充柱具有运行时间更持久和滤料层填充高度更小的优势;0.5～1 mm粒径QSD填充柱对SS去除率超过80％,且未显著吸附截留沼液氨氮,适合作为沼液SS过滤预处理单元且有利于后续氮回收.

The combination of chemical fertilizer and biochar is regarded as a useful soil supplement for improving the properties of soil and crop yields, and this study describes how the biochar of maize straw can be used to improve the quality of the degraded black soil. This has been achieved by examining the effects of combining different amounts of biochar with chemical fertilizer on the porosities and aggregate formation of soil and exploring how these changes positively impact on crop yields. A field trial design combining different amounts of maize straw biochar [0 (NPK), 15.75 (BC1), 31.5 (BC2), and 47.25 t ha−1 (BC3)] with a chemical fertilizer (NPK) has been used to investigate changes in the formation of soil aggregate, clay content, soil organic carbon (SOC), and crop yields in Chinese black soil over a three year period from 2013 to 2015. The results of this study show that the addition of fertilizer and biochar in 2013 to black soil results in an increased soybean and maize yields from 2013 to 2015 for all the treatments, with BC1/BC2 affording improved crop yields in 2015, while BC3 gave a lower soybean yield in 2015. Total porosities and pore volumes were increased for BC1 and BC2 treatments but relatively decreased for BC3, which could be attributed to increased soil capillary caused by the presence of higher numbers of fine soil particles. The addition of biochar had a positive influence on the numbers and mean weight diameters (MWD) of soil macroaggregates (>0.25 mm) that were present, with the ratio of SOC to TN in soil macroaggregates found to be greater than in the microaggregates. The most significant amount of carbon present in macroaggregates (>2 mm and 0.25–2 mm) was observed when BC2 was applied as a soil additive. Increasing the levels of maze straw biochar to 47.25 t ha−1 led to an increase in the total organic carbon of soil, however, the overall amount of macroaggregates and MWD were decreased, which is possibly due to localized changes in microbial habitat. The supplementation of biochar increased in the amount of aromatic C present (most significant effect observed for BC2), with the ratio of aliphatic C to aromatic C found to be enhanced due to a relative reduction in the aliphatic C content with >2 mm particle fraction. These changes in organic carbon content and soil stability were analyzed using univariate quadratic equations to explain the relationship between the type of functional groups (polysaccharide C, aliphatic C, aromatic C, aliphatic C/aromatic C) present in the soil aggregates and their MWDs, which were found to vary significantly. Overall, the results of this study indicate that the use of controlled amounts of maize-straw biochar in black soil is beneficial for improving crop yields and levels of soil aggregation, however, the use of excessive amounts of biochar results in unfavorable aggregate formation which negatively impacts the yields of crop growth. The data produced suggest that aromatic C content can be used as a single independent variable to characterize the stability of soil aggregate when biochar/fertilizer mixtures are used as soil additives to boost growth yields. Analysis of soil and crop performance in black soil revealed that the application of maize-straw biochar at a rate of 15.75 and 31.5 t ha−1 had positive effects on crop yields, soil aggregation and accumulation of aromatic C in the aggregate fractions when a soybean-maize rotation system was followed over three years.

Combined antibiotic and heavy metal pollution has generated considerable concern. Constructed wetlands (CWs) have been shown to efficiently remove pollutants; however, the microbial community responses to combined pollutants remain enigmatic. In this study, seven microcosm CWs were planted with Myriophyllum aquaticum, spiked with tetracyclines (TCs) (300-30,000 mu g/L), alone or with Cu(II), to investigate the response of plant-associated microbial communities. TCs and the Cu/TC ratio greatly affected the performance of CWs. Tetracyclines led to higher microbial diversity, evenness and richness, while UniFrac distances and principal coordinate (PCO) and redundancy analyses revealed that the co-presence of TCs and Cu(II) led to variations in bacterial communities. Proteobacteria, Cyanobacteria and Bacteroidetes were the dominant microbial phyla and Cloacibacterium, Hydrogenophaga, Rheinheimera and Denitratisoma accounted for 6.2-21.0% of all genera. Therefore, the co-occurrence of heavy metals should be considered when judging the removal potential of TCs in phytoremediation.

Antibiotic and heavy metal pollution of aquatic environments are issues of serious concern, and the macrophyte Myriophyllum aquaticum may provide a viable solution for the removal of these contaminants. However, the toxic effects of coexisting tetracyclines (TCs) and Cu(II) on this plant species are currently unclear. In the present study, we constructed wetland microcosms planted with M. aquaticum and spiked these with three TCs (tetracycline, oxytetracycline, and chlortetracycline) and Cu(II) at concentrations ranging from 100 to 10,000 μg/L to investigate how Cu(II) influences the growth and tolerance responses of plants to TCs. After 12 weeks, we found that TCs had accumulated in the plants, and that plant growth and characteristics were significantly affected by the levels of both TCs and Cu(II). While low Cu(II) levels had a synergistic effect on the accumulation of TCs, high levels were observed to reduce accumulation. However, low levels of TCs and Cu(II) had a hormesis effect on plant growth, with plant biomass and leaf chlorophyll content decreasing and the malondialdehyde content and activities of antioxidant enzymes gradually increasing with an increase in TC dosage. The coexistence of low levels of Cu(II) was, however, found to alleviate these adverse effects. Principal component analysis revealed a close relationship among plant biomass, chlorophyll content, malondialdehyde content, and antioxidant enzyme activities. Considering that the Cu/TC ratio was shown to markedly affect M. aquaticum growth, the respective proportions of these pollutants should be taken into consideration in the future design of constructed wetlands.

Water pollution caused by antibiotics and heavy metals has attracted considerable concern, and efficient approaches are urgently needed for their removal. The objective of this study was to investigate the potential of Myriophyllum aquaticum for long-term phytoremediation of wastewater containing tetracycline (TC) antibiotics and copper. Seven hydroponic microcosms were constructed, spiked with tetracycline, oxytetracycline (OTC) and chlortetracycline (CTC) (300–30,000 μg/L), alone or simultaneously with Cu (II), and operated for 12 weeks. The TC removal efficiencies using the hydroponic microcosms here were commensurate or higher than those in previous studies. However, the Cu/TC ratio greatly affected the removal, accumulation of TCs by M. aquaticum, and plant growth. Low levels of Cu (II) (<1000 μg/L) promoted TC removal, but excessive Cu (II) (>10,000 μg/L) impeded it. Mass balance analysis showed that most TCs (45%–64% on average) accumulated in the roots of M. aquaticum. Plant biomass was correlated with the removal of COD, TN, TP, and NH4+-N (p ≤ 0.05) but not with removal of the TCs. Proteobacteria, Bacteroidetes, and Fusobacteria were dominant in the microbial communities, but they showed little correlation with the TC removal. M. aquaticum can be employed as an effective means of TC removal from water. The co-existence of heavy metals should be considered when evaluating the removal potential of TCs in phytoremediation.

Intensified livestock system produced large amount of bio-waste, and improper disposal of livestock manure has led to severe environmental consequences. However, knowledge about the time-dependent changes of manure-derived nitrate and soil bacterial diversity along the soil profiles is limited. Vertical variation of soil bacterial diversity and composition in a manure-amended maize field and adjacent non-manured woodland was investigated using high-throughput sequencing technique in spring and autumn along a 1-m profile depth. The soil is classified as aquic inceptisol with a bulk density of 1.31 g cm−3, and a sandy loam texture. The results showed that significant higher amount of nitrate (up to 172.13 mg kg−1) was detected along the soil profile loaded with cattle manure compared with the adjacent non-manured woodland. Soil δ15N-NO3− composition from maize field fall between + 5 and 25‰, while those from woodland fall between − 5 and 15‰. No significant difference in bacterial richness between the two land uses was found, while clear separation of bacterial structure was detected even to the deep soil layers. Canonical correspondence analysis showed that soil organic matter, C/N ratio, nitrate content, pH, and moisture were the major factors influencing the variance of bacterial community composition. Bacterial networks in the maize field harbor more modules than those in the adjacent woodland. Negative standardized effect size measure of mean nearest taxon distance in the soils tended to be more phylogenetically clustered than expected by chance, and was more likely to be clustered along the depth. These findings suggested that soil bacterial β diversity was strongly affected by multi-nutrient properties in terms of high livestock manure load, and had important implications for assessing the environmental impacts on belowground biodiversity in sandy loam soils.

Pollution with antibiotics and heavy metals necessitates efficient approaches for their removal. This study was conducted to investigate the role of Cu in the tetracycline (TC) removal potential of the floating plant Myriophyllum aquaticum and determine the underlying mechanisms. Myriophyllum aquaticum exhibited high TC removal potential from water (60% at 50 mg.L-1 TC and 10 g.L-1 M. aquaticum). Adsorption was the main mechanism of TC removal within 2 h, accounting for over 75% and 90% of total TC removal with and without Cu (II), respectively. Fourier-transform infrared spectroscopy and functional group identification showed that -OH, -COOH, and -NH2 were involved in TC adsorption through ion exchange. Cu(II) may act as a bridge during TC adsorption with M. aquaticum, but competitive adsorption of Cu(II) and TC on M. aquaticum occurs in case of excessive Cu(II). Myriophyllum aquaticum can serve as an important bioresource for effectively removing TC and Cu(II) from aquatic environments.

As a floating plant, Myriophyllum aquaticum provides a large surface area under water, and thus has high potential for the removal of pollutants through adsorption. The aim of this study was to evaluate the potential adsorption of tetracycline (TC) by M. aquaticum, and examine the underlying mechanisms. M. aquaticum exhibited a high potential for TC removal from water. Adsorption was the main mechanism for rapid TC removal by live M. aquaticum plants, due to its large contact area and ion exchange, accounting for about 99% and 54% of the total amount of TC removed within 2 h and 5 d, respectively. Further, the roots of M. aquaticum exhibited a higher adsorption capacity than the stems or leaves, as the roots had the largest specific surface area. Fourier transform infrared spectroscopy analysis and identification of functional groups showed that -OH, -COOH, and -NH2 groups are involved in the adsorption process. The use of M. aquaticum may be a promising approach for TC removal from aquatic environments, especially in terms of shortening reaction times. (C) 2019 Elsevier Ltd. All rights reserved.

In order to evaluate the effects of hydraulic shearing action on activated sludge floc aggregation, floc aggregation, breakage and re-growth performances under different shear strengths were systematically examined. Performances were evaluated by measuring the floc size variations using a laser particle size analyser on-line monitoring technique. The flocs after breakage were characterised by investigating the composition of extracellular polymer substances (EPS), floc size, substances released due to surface erosion and chemical structures using Fourier transform infrared spectroscopy (FTIR) to clarify the breakage model and re-growth mechanism. The results showed that activated sludge flocs broken at a hydraulic shear strength GT value (the product of the velocity gradient and time) of 56,280 exhibited enhanced re-growth performance compared with the control. The substances released from sludge increased with shear strength, indicating that the floc breakage mode gradually transitioned from fragmentation to surface erosion. FTIR revealed that, after breakage, the spectrum of loosely bound EPS in sludge tended to be similar to that of tightly bound EPS. The results suggest that the breakage of activated sludge flocs under moderate hydraulic shear strength can fragment flocs into smaller particles without surface erosion and promote the exposure of inner tightly bound EPS, thereby improving re-growth performance.