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Summary: Lake and adjoining river ecosystems are ecologically and economically valuable and are heavily threatened by anthropogenic activities. Determining the inherent capacity of ecosystems for polycyclic aromatic hydrocarbon (PAH) biodegradation can help quantify environmental impacts on the functioning of ecosystems, especially on that of the microbial community. Here, PAH biodegradation potential was compared between sediments collected from a lake bay (LS) and an adjoining river (RS) ecosystem. Microbial community composition, function, and their co‐occurrence patterns were also explored. In the RS, the biodegradation rates (KD) of pyrene or PAH were almost two orders of magnitude higher than those in the LS. Sediment functional community structure and network interactions were dramatically different between the LS and RS. Although PAH degradation genes (p450aro, quinoline, and qorl) were detected in the LS, the community activity of these genes needed to be biostimulated for accelerated bioremediation. In contrast, functional communities in the RS were capable of spontaneous natural attenuation of PAH. The degradation of PAH in the RS also required coordinated response of the complex functional community. Taken together, elucidating functions and network interactions in sediment microbial communities and their responses to environmental changes are very important for the bioremediation of anthropogenic toxic contaminants. [ABSTRACT FROM AUTHOR]

As a recently discovered process of nitrogen cycling, anaerobic ammonium oxidation coupled to ferric iron reduction (Feammox) has attracted more attentions. This study investigated the spatial variation of Feammox in the sediment of different zones of a shallow freshwater lake and the effect of organic matter derived from algae and macrophyte on Feammox process. The potential Feammox rates showed significant differences among sediments from algae-dominated area (ADA), transitional area in the center of the lake (TDA), and macrophyte-dominated area (MDA), and in a descending order, ADA, MDA, and TDA. The potential Feammox rate ranged from 0.14 to 0.34 mg N kg−1day−1 in the freshwater lake sediment. The potential Feammox rates of the sediment with algae or macrophyte amendment were 12.29% and 15.31% higher than the control test without algae and macrophyte amendment. The addition of algae or macrophyte to the sediment from TDA could improve the amount of HCl-extractable total Fe, Fe(III) reduction rate, and the abundance of FeRB. These results demonstrated that organic matter is one of the key regulators of Feammox process. [ABSTRACT FROM AUTHOR]

Drinking water treatment residue (DWTR) seems to be very promising for controlling lake sediment pollution. Logically, acquisition of the potential toxicity of DWTR will be beneficial for its applications. In this study, the toxicity of DWTR and sediments amended with DWTR to Aliivibrio fischeri was evaluated based on the Microtox ® solid and leachate phase assays, in combination with flow cytometry analyses and the kinetic luminescent bacteria test. The results showed that both solid particles and aqueous/organic extracts of DWTR exhibited no toxicity to the bacterial luminescence and growth. The solid particles of DWTR even promoted bacterial luminescence, possibly because DWTR particles could act as a microbial carrier and provide nutrients for bacteria growth. Bacterial toxicity (either luminescence or growth) was observed from the solid phase and aqueous/organic extracts of sediments with or without DWTR addition. Further analysis showed that the solid phase toxicity was determined to be related mainly to the fixation of bacteria to fine particles and/or organic matter, and all of the observed inhibition resulting from aqueous/organic extracts was identified as non-significant. Moreover, DWTR addition not only had no adverse effect on the aqueous/organic extract toxicity of the sediment but also reduced the solid phase toxicity of the sediment. Overall, in practical application, the solid particles, the water-soluble substances transferred to surface water or the organic substances in DWTR had no toxicity or any delayed effect on bacteria in lakes, and DWTR can therefore be considered as a non-hazardous material. [ABSTRACT FROM AUTHOR]

Thein situimmobilization technique is a typical method of geoengineering in lakes for eutrophication control. The method reduces internal phosphorus loading from sediments by dosing chemicals, which means that selecting appropriate chemicals are essential. Therefore, the authors present a comprehensive review of the current available knowledge of chemicals used for thein situtechnique. Chemicals are classified into nine categories, and the control effectiveness and stability of the chemicals as well as the physicochemical and ecological responses to the control are reviewed. The authors also address challenges of chemicals in practical application and offers recommendations for future research. [ABSTRACT FROM PUBLISHER]

• Resuspension-induced material redistribution varied sediment P immobilization. • Surface sediment P immobilization was lower than that in bottom sediment. • Redistribution of potential target P was typically regulated by < 8 μm sediment. • Redistribution of material was typically regulated by > 63 μm particles. Lake geoengineering with phosphorus (P)-inactivating materials to reduce sediment P loading is often used for eutrophication control. The redistribution of materials in sediment, especially those induced by resuspension, is reportedly a common phenomenon during practical applications, which may interfere with the pollution control. Notably, a recent study by the authors initially found that the heterogeneous properties of materials and sediments varied the P immobilization in different sized sediments which exhibited diverse movement characteristics. Therefore, this study hypothesizes a particle size-related vertical redistribution of materials in the sediment profile induced by resuspension, which shapes sediment P immobilization at different depths. Based on two differently sized materials, lanthanum (La)-modified bentonite clay (Phoslock) and drinking water treatment residue (DWTR), this study found a weakened reduction of mobile P and bioavailable P pool by both DWTR and Phoslock in surface sediment after resuspension. As the depth decreased from >12 to surface 0–1 cm, the remaining mobile P increased from 7.11%–10.8% to 11.0%–17.8% of the total P in the sediment with Phoslock and from 1.66%–4.73% to 9.70%–20.7% of the total P in the sediment with DWTR; meanwhile, bioavailable P pool reduction proportions decreased from 48.6%–72.3% to 3.23%–45.1% for Phoslock and from 51.5%–71.4% to 4.94%–25.2% for DWTR. Further analysis verified the hypothesis of this study; importantly, the redistributions of the potential target P (including mobile and bioavailable P) for immobilization were regulated by relatively small sediments (e.g., <8 μm fraction), which tended to become enriched in surface sediment after resuspension, while relatively large materials (e.g., >63 μm fraction) regulated their redistributions and were more likely to be buried at the bottom of the sediments. Accordingly, to design appropriate strategies for lake geoengineering, relatively small materials (e.g., <8 μm) targeting to immobilize both mobile and bioavailable P are typically recommended to be developed for restoration of lakes with frequent sediment resuspension. [Display omitted] [ABSTRACT FROM AUTHOR]

The decay of algal biomass and aquatic plants in freshwater lakes leads to the overproduction of autochthonous organic matter (OM) and the exhaustion of dissolved oxygen, impacting the microbial community and subsequent biodegradation of emerging contaminants in sediment. This study explored how the microbial processing of aquatic plant- and algal-derived OM (POM and AOM) mediates 17α-ethinylestradiol (EE2) biodegradation in the anoxic sediments of Lake Taihu in China. In four months of microcosm incubations, the increased concentrations of protein-like substances in AOM and POM exhibited temporary activation on microbial metabolic enzyme activity (fluorescein diacetate hydrolase and dehydrogenase) and significantly promoted the carbon mineralization with iron reduction (P < 0.001). These in turn increased the EE2 biodegradation efficiency to 77–90 ng g−1 in the anoxic sediment. However, a higher EE2 biodegradation of 109 ng g−1 was achieved with the humic acid augmentation containing more quinone-like compounds, showing a weaker substrate-priming effect but accelerated redox cycling of iron and organic substrates in the later period of incubation. The microbial analysis further revealed that the quinone-like compounds in OM were more closely associated with microbial electron transfer and strengthened their interspecies syntrophic cooperation favorable to contaminant biodegradation, even though the connective members exposed to protein-like components upregulated more functional genes related to organic carbon and xenobiotics metabolism and biodegradation. Our findings will help predict the fate of estrogens in various sedimentary environments under increasing eutrophication and further climate change scenarios. [Display omitted] • Autochthonous OM enhanced microbial activity and C mineralization in anoxic sediment. • Priming effect on C mineralization and Fe(III) reduction accelerated EE2 degradation. • Different evolution and assembly of microbes exposed to protein- and quinone-like OM. • Quinone-like OM facilitated interspecies cooperation of electron transfer of microbes. • Hypoxia-induced inhibition exceeded promotion of autochthonous OM on EE2 degradation. [ABSTRACT FROM AUTHOR]

Abstract: Drinking water treatment residuals (WTRs), non-hazardous by-products generated during potable water production, can effectively reduce the lake internal phosphorus (P) loading and improve water quality in lakes. It stands to reason that special attention regarding the beneficial reuse of WTRs should be given not only to the effectiveness of P pollution control, but also to the effects on the migration and transformation of other nutrients (e.g., nitrogen (N)). In this work, based on laboratory enrichment tests, the effects of WTRs addition on nitrification in lake sediment were investigated using batch tests, fluorescence in situ hybridization, quantitative polymerase chain reaction and phylogenetic analysis techniques. The results indicated that WTRs addition had minor effects on the morphologies of AOB and NOB; however, the addition slightly enhanced the sediment nitrification potential from 12.8 to 13.2 μg-N g−1-dry sample h−1 and also increased the ammonia oxidation bacteria (AOB) and nitrite oxidizing bacteria (NOB) abundances, particularly the AOB abundances (P < 0.05), which increased from 1.11 × 108 to 1.31 × 108 copies g−1-dry sample. Moreover, WTRs addition was beneficial to the enrichment of Nitrosomonas and Nitrosospira multiformis and promoted the emergence of a new Nitrospira cluster, causing the increase in AOB and NOB diversities. Further analysis showed that the variations of nitrification in lake sediment after WTRs addition were primarily due to the decrease of bioavailable P, the introduction of new nitrifiers and the increase of favorable carriers for microorganism attachment in sediments. Overall, these results suggested that WTRs reuse for the control of lake internal P loading would also lead to conditions that are beneficial to nitrification. [Copyright &y& Elsevier]

Drinking water treatment residuals (WTRs), nonhazardous by-products generated in a drinking water treatment plant, can be reused to immobilize phosphorus (P) to control the internal P loading from lake sediments for eutrophication control. Reasonably, before practical application, it is essential to determine the P immobilization capability of WTRs in lake sediments under various conditions. In this work, laboratory scale experiments were conducted to investigate the effects of light, microbial activity, and sediment resuspension on the P immobilization capability of WTRs. The results suggested that absence of light, low microbial activity, and sediment resuspension can increase the internal P loading from lake sediments. WTRs can, however, reduce the internal P loading significantly. Further analysis demonstrated that WTRs can stabilize P, decreasing the P bioavailability in the sediments under varied conditions. WTRs also presented little undesirable effects on the dissolved oxygen levels and pH of overlying water. Therefore, light, microbial activity, and sediment resuspension have little effect on the P immobilization capability of WTRs in lake sediments. [ABSTRACT FROM AUTHOR]

Highlights: [•] WTRs had low metals leaching risk in lake water. [•] The P adsorption capacity of the raw and settled WTRs had little difference. [•] The raw and settled WTRs had the same ability to immobilize P in lake sediments. [ABSTRACT FROM AUTHOR]

The classical lake internal phosphorus (P) pollution control using P-inactivating materials is typically carried out by reducing the release of soluble P from sediments to overlying water; however, particulate P loading through sediment resuspension could also cause internal P pollution for algae breeding. Therefore, based on lanthanum modified bentonite clay (Phoslock®) and drinking water treatment residues (DWTR), the effect of P inactivating materials on sediment resuspension and settlement were comprehensively investigated to assess the variations in particulate P pollution from sediment. Results showed that both materials could effectively control soluble P pollution from sediment, while both had limited effect on the supplement of particulate P to overlying water. The reason may be that hydrodynamic disturbance was the key factor regulating sediment resuspension and settlement. The disturbance induced the resuspension of different sized sediments, especially <8 μm fractions, while increasing disturbing intensities promoted resuspension of relatively larger sized sediments (e.g., <63 μm). Further analysis suggested that after resuspension and settlement, the efficiencies of reducing bioavailable P by Phoslock® in relatively large sized sediment fraction (e.g., <63 μm) were substantially less than those in relatively small sized sediment (<8 μm). Although the reducing efficacies of DWTR had limited changes in different sized sediments, the remaining bioavailable P were clearly higher in smaller sized sediments with DWTR. The different performances on bioavailable P reduction mainly resulted from the distributions of materials and original P in different sized sediments. These findings indicated the potential supplement of particulate P for algal growth during resuspension and settlement of sediments amended by P inactivating materials. Overall, understanding the sediment P bioavailability and hydraulic properties at different sizes and the lake hydrodynamic conditions is essential to develop appropriate methods to control lake internal P pollution. • Phoslock® and water treatment residue had limited effect on particulate-P loading. • Phoslock® is more feasible to reduce bioavalible P in <8 μm fraction of sediment. • The residue to reduce bioavalible P in different sized sediments was similar. • Sediment particulate-P required more attention for lake eutrophication control. [ABSTRACT FROM AUTHOR]

Highlights: [•] WTRs promoted the aggregation of anammox bacteria in lake sediments. [•] WTRs strengthened the activity of anammox bacteria in lake sediments. [•] WTRs increased the abundance of anammox bacteria in lake sediments. [•] WTRs caused anammox bacteria to be more closely related to Candidatus Brocadia. [ABSTRACT FROM AUTHOR]

Abstract: The reuse of drinking water treatment residuals (WTRs) to immobilize phosphorus (P) in sediments is a novel application for lake restoration. The recycling of WTRs is beneficial from both environmental and economic standpoints. This work assessed the stability of P in sediments found in Lake Taihu and Lake Baiyangdian before and after being amended with WTRs. The results indicated that WTRs had similar effects on the stability of P in each of the lake's sediments. WTRs can significantly reduce the P desorption potential of the sediments at pH values less than 11. WTRs can also inhibit the competitive adsorption of SiO4 2− with P. Compared with the raw sediments, the organic matter in the sediments, ion strength and anaerobic conditions presented minor undesirable effects on the stability of P in the WTRs-amended sediments. Moreover, WTRs can increase the P adsorption rate and capacity of the sediments. Overall, these results demonstrated that WTRs can make P more stable in lake sediments under various conditions. [Copyright &y& Elsevier]

Highlights: [•] Water treatment residuals (WTRs) reduced internal P loading from lake sediments. [•] The retained-P by WTRs was stable in lake sediments. [•] WTRs presented minimum changes to the surroundings. [Copyright &y& Elsevier]

Abstract: The use of drinking water treatment residuals (WTRs) to immobilize P in sediments is a novel approach for lake restoration. However, the lability of P in WTRs-amended sediments may vary with many factors, e.g., hydrogen sulfide content. Earlier works in our laboratory have demonstrated that WTRs are effective sorbents for hydrogen sulfide in water. Thus, we hypothesized that the lability of P in WTRs-amended sediments would not be increased by hydrogen sulfide. The results of this work suggested that this hypothesis was tenable. Compared to the raw sediments, the amended sediments had significantly lower P desorption potential in the presence of hydrogen sulfide at different times, pH and concentrations. Moreover, the amended sediments were also better able to adsorb hydrogen sulfide. In the amended sediments, the P, which was easily desorbed due to the effect of hydrogen sulfide, was transformed into the Fe/Al bound P. [Copyright &y& Elsevier]

Abstract: This work investigated the potential for reusing water treatment residuals (WTRs) to immobilize phosphorus (P) in the sediments of Lake Taihu and Lake Baiyangdian. The results indicated that WTRs made inorganic P more stable in the sediments, although the sediments from each lake had dissimilar properties. Conversely, WTRs had no effect on the activity of organic P. However, after the sediment was mixed with WTRs, the inorganic P was immobilized in 10days. Microbiological analyses further revealed that WTRs could alter the structures of the microbial community within the sediments but exert no adverse effect on the bacterial diversity. Moreover, WTRs were found to be beneficial to microorganism growth. Because of the effects exerted by WTRs, the total abundance of bacteria in the sediments increased from 5.10×1012 to (0.66–4.81)×1014 copies g−1 for Lake Baiyangdian sediments and from 1.16×1013 to (1.08–7.14)×1014 for Lake Taihu sediments. Therefore, WTRs can be safely used to immobilize P in sediments for the purpose of lake restoration. [Copyright &y& Elsevier]

Nitrate and sulfate, as electron acceptors (EAs), influence microbial communities and the subsequent biodegradation of emerging contaminants, such as 17α-ethynylestradiol (EE2) in anaerobic sediments. Results of this study showed that nitrate amendment significantly raised nitrate reduction intensity within a short period (<5 days) and greatly influenced microbial community succession compared with sulfate amendment. Nitrate reduction induced deterministic selections that narrowed the niche widths of the microbial community, creating direct correlations between functional members, including denitrifiers and potential estrogen degraders like Pseudomonas. The facilitative coordination of microbes and increased denitrification resulted in greater EE2 biodegradation under nitrate-reducing (0.19 ± 0.02 μg g−1) and combined nitrate- and sulfate-reducing conditions (0.23 ± 0.01 μg g−1) after 120 days. Moreover, natural organic matter enhanced interspecies syntrophic cooperation (the number of direct connectors increased from 9 to 25 in the microbial network) in the microbial community and further improved EE2 biodegradation efficiency to 0.26 ± 0.03 μg g−1. Conversely, sulfate reduction required longer adaptation (>20 days) with a higher contribution of stochastic processes in community assembly, yielding fewer connections with estrogen degraders and weaker EE2 biodegradation (0.15 ± 0.03 μg g−1). These mechanistic understandings can guide EA selection in the bioremediation of emerging contaminants. [Display omitted] • Impacts of nitrate and sulfate as EAs on anaerobic degradation of EE2 were compared. • EE2 degradation follows the order of nitrate and sulfate > nitrate > sulfate reducing. • Direct collaborations of denitrifiers and estrogen degraders promote EE2 degradation. • Sulfate reduction needs longer adaptation and has fewer linkages with EE2 degradation. • Natural organic matter enhances syntrophic cooperation and improves EE2 degradation. [ABSTRACT FROM AUTHOR]

• Resuspension causes horizontal variations in P immobilization in lake sediments. • The resuspension effect is due to varying movements of different-sized particles. • Horizontal distribution of total P is regulated by 16–32 μm-sediment migration. • Migration of <8 and >63 μm materials regulates P immobilization in sediment planes. The importance of controlling internal phosphorus (P) pollution in lakes has been recognized by scientists, and the application of P-inactivating materials to immobilize sediment P is often considered. However, sediment resuspension, a typical physical process occurring in lakes, has been demonstrated to increase the uncertainty of immobilization. In this study, we explored the characteristics of P immobilization in the horizontal direction under the effects of resuspension using annular flume tests based on drinking water treatment residuals (DWTR). The results showed that resuspension caused the mobile P and bioavailable P to be heterogeneously distributed in sediment planes after DWTR addition, resulting in varying P immobilization efficiencies at different depths. In particular, the coefficient of variation was 14.2–24.5% for mobile P horizontally distributed in the planes, resulting in a range of mobile P decreasing efficiencies at 24.0–47.8%. Further analysis indicated that variations in horizontal distribution were typically due to the varied migration of particles of different sizes. Specifically, P immobilization in sediment planes at different depths was regulated by promoting the migration of <8 μm DWTR after relatively low-intensity disturbance (in surface 0–1 cm sediment). After relatively high-intensity disturbance (in the whole 0–3 cm sediment), immobilization in the horizontal direction was regulated by coupling the migration of >63 μm DWTR (to the bottom) with the mixing of <8 μm DWTR in the sediment plane at different depths. The varying horizontal distributions of total P, resulting from the migration of 16–32 μm sediment, could enhance the heterogeneities of the P immobilization. Thus, the particle size of materials and lake background conditions, for example, the hydrodynamic characteristics and P distributions in differently sized sediments, should be used as key bases to select or develop P-inactivating materials to design proper remediation strategies for controlling internal P pollution in lakes. [Display omitted] [ABSTRACT FROM AUTHOR]

Climate change and increasing eutrophication are expected to increase the release of autochthonous organic matter (OM) to sediments, where most contaminants are transformed or mineralized in freshwater lakes. This study sought to evaluate how cyanobacteria- and macrophyte-derived OM (COM and MOM) affected the microbial attenuation of 17α-ethinylestradiol (EE2) in the sediment from eutrophic Lake Taihu in China. In two months of water-sediment microcosm experiments, the input of COM and MOM both promoted EE2 degradation more strongly than humic acids, and the degradation efficiency was significantly and positively correlated with the cometabolism of increasing organic carbon in sediments (P < 0.001). The enhanced degradation was explained by responses of indigenous bacterial community to OM amendment as a priming effect. The immediate breakdown of biodegradable components such as proteinaceous substances in COM and MOM remarkably augmented the metabolic activity of bacteria in terms of the stimulated activity of extracellular enzymes including fluorescein diacetate and dehydrogenase, as well as the elevated production of proteins and polysaccharides in extracellular polymeric substances. In the meantime, the bacterial community composition was reshaped toward a more eutrophic state, leading to the clear upregulation of metabolic function genes of organic carbon and xenobiotics. Correlation-based network analysis further determined the strong facilitative coordination between the community members and the compositional variability of OM in the cometabolism. These results suggest that cyanobacterial blooms-dominated zones are potential hotspot areas for steroid estrogen attenuation, a finding of significance for the control and management of complex pollution in freshwater lakes. Image 1 • Input of autochthonous OM enhanced microbial degradation of EE2 in lake sediments. • EE2 degradation was positively related to cometabolism of degradable OM components. • Autochthonous OM increased bacterial metabolic enzyme activity and EPS secretion. • Facilitative interactions among microbes were promoted by proteinaceous substances. • Autochthonous OM upregulated xenobiotic metabolic function genes of bacterial group. [ABSTRACT FROM AUTHOR]