The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Zhengwen Liu - One of the best experts on this subject based on the ideXlab platform.
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sedimented cyanobacterial detritus as a source of nutrient for submerged macrophytes Vallisneria spiralis and elodea nuttallii an isotope labeling experiment using 15n
Limnology and Oceanography, 2010Co-Authors: Leiyan Zhang, Zhengwen Liu, Jack J MiddelburgdAbstract:A tracer experiment using the nitrogen isotope 15N investigated the uptake and incorporation of nitrogen from sedimented cyanobacterial detritus by two species of submerged macrophytes, the native Vallisneria spiralis and the exotic Elodea nuttallii, in Lake Taihu (China). The cyanobacterium Microcystis was labeled with 15Nammonium and dried to produce detritus, which was injected into vegetated sediments and traced to establish the fate of particulate nitrogenous material. Samples of the inoculated sediment and all parts of the plants growing therein were examined for excess 15N after 3, 5, 9, and 22 d. Microcystis-derived nitrogen was assimilated rapidly by the plants, then translocated from the roots to the shoots and stored in different parts of the plants, where it supports growth. The ability to utilize and retain nutrients originating from sedimented cyanobacterial detritus was significantly higher in V. spiralis than in E. nuttallii. Cyanobacterial scums such as the Microcystis blooms of Lake Taihu, which drift and deposit in the sediments of the littoral zones, are an important nutrient source for macrophytes, particularly in downwind areas.
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compensatory growth of a submerged macrophyte Vallisneria spiralis in response to partial leaf removal effects of sediment nutrient levels
Aquatic Ecology, 2010Co-Authors: Zhengwen LiuAbstract:Many plants mitigate damage due to loss of tissues through compensatory growth, yet their compensatory abilities vary depending on physical and environmental conditions. We conducted an outdoor experiment using a 2 × 2 factorial experimental design (leaf damage and nutrient level), in order to evaluate the compensatory growth response of Vallisneria spiralis (a submerged macrophyte widely distributed in China) to partial leaf removal in two nutrient regimes. Our results reveal that under both high- and low-nutrient conditions, V. spiralis exhibited substantial compensatory growth response to partial leaf removal via accelerated growth rates, with significantly greater compensatory abilities observed in the high-nutrient sediments. These observations suggest that V. spiralis has a strong compensatory ability to partial leaf removal, providing arguably one of the major mechanisms for the coexistence of this plant with herbivores, in particular, in eutrophic freshwater ecosystems (e.g. Lake Taihu).
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density dependent effects of snail grazing on the growth of a submerged macrophyte Vallisneria spiralis
Ecological Complexity, 2009Co-Authors: Zhengwen LiuAbstract:Abstract In order to better understand the role of herbivorous snails in freshwater ecosystems, we conducted experiments investigating food preference of the snail Radix swinhoei on leaves of the submerged plant Vallisneria spiralis with and without periphyton coverage. The effects of snail grazing on the growth of V. spiralis were assessed in a no-snail control and at three snail densities (80, 160, 240 individuals m−2). Results showed that the snails chose preferentially leaves covered by periphyton. Grazing activity at low snail density (80 individuals m−2) was found to stimulate V. spiralis growth, but at higher snail density (240 individuals m−2), plant growth was apparently suppressed. An increase observed in nutrient concentrations in water column with increasing snail density may be attributed to nutrient release by snails. This study suggests that the nature of the relationship between herbivorous snails and macrophytes in freshwater ecosystems depends on the abundance of the snails. At low snail density, the relationship may be a mutualistic one, but at high density snail herbivory may impact negatively on macrophyte biomass in lakes.
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effects of leaf damage and sediment type on compensatory growth of submerged macrophyte Vallisneria spiralis
Journal of Applied Ecology, 2008Co-Authors: Zhengwen LiuAbstract:Through a 2 x 2 factorial outdoor experiment, the effects of leaf damage and sediment type on the compensatory growth of submerged macrophyte Vallisneria spiralis were examined. The results showed that leaf damage and sediment type had significant effects on the cumulative biomass, biomass allocation, and ramet number of V. spiralis. Compared with undamaged plant, the strongly damaged one had a decrease of cumulative biomass and ramet number and an increase of biomass allocation, but no evident difference was observed between weakly damaged and undamaged plants. The cumulative biomass of undamaged and strongly damaged plants was lower in infertile sediments (bank sediment) than in fertile sediments (lake sediment), but that of weakly damaged plant was almost the same in the two sediments. The biomass allocation and ramet number of V. spiralis were higher in bank sediment than in lake sediment. Leaf damage and sediment type also affected the relative growth rate (RGR) of V. spiralis. Leaf damage resulted in an increase of RGR, but the difference of RGR between weak damage and strong damage was not evident. The RGR of undamaged and strongly damaged plants was significantly higher in lake sediment than in bank sediment, but that of weakly damaged plant was almost the same in the two sediments. The mechanisms of the compensatory growth of V. spiralis were discussed.
P Chandra - One of the best experts on this subject based on the ideXlab platform.
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lead mediated synthesis of metal binding peptides phytochelatins in aquatic plant Vallisneria spiralis l
2000Co-Authors: Meetu Gupta, U N Rai, R. D. Tripathi, P ChandraAbstract:Pollution of the biosphere with toxic metals has increased dramatically since the beginning of industrial revolution. The sources of lead (Pb) contamination include metal smelting, Pb based paints, lead arsenate, pesticide and phosphate fertilizers (Singh et al., 1997). Another major source is Pb alkyl derivatives in gasoline which are cracked to release Pb in automobile exhaust in the form of lead aerosols. Recently Pb was found to be a major contaminant of ponds (Chandra et al., 1993) and lakes (Tripathi et al., 1997). Plants have been used to decontaminate Pb from contaminated environment (Gupta & Chandra, 1994; Gupta et al., 1995; Rai et al., 1995a; Boyajian & Carreira, 1997).
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bioaccumulation and toxicity of mercury in rooted submerged macrophyte Vallisneria spiralis
Environmental Pollution, 1998Co-Authors: Meetu Gupta, P ChandraAbstract:Abstract Laboratory experiments were carried out to determine mercury (Hg) accumulating potential and toxicity in the submerged aquatic macrophyte Vallisneria spiralis . Young plants were subjected to different concentrations (0.5, 1.0, 5.0, 10, 20 μM) of Hg for 24, 48, 96 and 168 h. Plants showed a Hg accumulation of 0.25 μmol/g dry weight in leaf and 1.12 μmol/g dry weight in roots, respectively, at 20 μM Hg after 168 h. The chlorophyll, protein and nitrogen, phophorus, potassium contents decreased significantly with increasing Hg concentrations and treatment durations. In vivo nitrate reductase activity also decreased from the lowest concentration of Hg to the highest. Cysteine content of leaf and root material increased at low Hg concentration and then significantly declined at higher doses of Hg. The results suggested a strong uptake potential for Hg by the roots which can act to monitor metal contamination in the environment, although the negative physiological implications cannot be ruled out, which are relevant for transfer of metal via food chain at different trophic levels.
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role of glutathione and phytochelatin in hydrilla verticillata i f royle and valusneria spiraus l under mercury stress
Chemosphere, 1998Co-Authors: Meetu Gupta, U N Rai, R. D. Tripathi, P ChandraAbstract:Abstract Both free (Hydrilla verticillata) and rooted (Vallisneria spiralis) submerged plants showed high potential to accumulate mercury, maximum being in roots of V. spiralis. During mercury stress these plants synthesized different species of phytochelatins (PCs), which bind with the accumulated mercury and showed high levels of cysteine and non-protein thiols. The induction of phytochelatins was accompanied by a decline in cellular levels of glutathione in both the plants, although the decline was only observed at high concentration and long duration of Hg in V. spiralis. Buthionine sulfoximine inhibited accumulation of non-protein thiols and glutathione, indicating the involvement of glutathione in phytochelatin synthesis. However, cycloheximide had no effect on early PC synthesis. Results showed that phytochelatins are synthesized in these plants and play a role in mercury detoxification.
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bioccumulation and toxicity of cu and cd in Vallisneria spiralis l
Environmental Monitoring and Assessment, 1994Co-Authors: Sarita Sinha, Manisha Gupta, P ChandraAbstract:Accumulation of Cu and Cd by Vallisneria spiralis was studied under laboratory conditions. Plants showed ability to reduce 5 µg ml−1 Cu background concentration to below 0.05 µg ml−1 (m.p.l., WHO 1985) within 48 h. The Cd concentration of 1.0 µg ml−1 was reduced to below m.p.l. (0.005 µg ml−1) in 168 h. Cysteine synthesis was more under Cd stress condition. Both the metals were toxic to the plants at higher concentrations; more in the case of Cd.
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lead accumulation and toxicity in Vallisneria spiralis l and hydrilla verticillata l f royle
Journal of Environmental Science and Health Part A-toxic\ hazardous Substances & Environmental Engineering, 1994Co-Authors: Meetu Gupta, P ChandraAbstract:Abstract Lead uptake potential of two aquatic macrophytes Vallisneria spiral is and Hvdrilla verticillata were determined in solution cultures under the laboratory conditions. Both the plants showed substantial accumulation of Pb, though it was more in H. verticillata. Accumulation was more in the roots of V. spiralis. Metal toxicity was largely insignificant at lower ambient concentrations. At higher Pb level (100 μM), inhibition in chlorophyll and protein content, in vivo nitrate reductase activity was recorded. Feasibilty of using both plants individually and in combination, for reducing Pb level in the water bodies has been suggested.
Marco Bartoli - One of the best experts on this subject based on the ideXlab platform.
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benthic nitrogen metabolism in a macrophyte meadow Vallisneria spiralis l under increasing sedimentary organic matter loads
Biogeochemistry, 2015Co-Authors: Elisa Soana, Mariachiara Naldi, Stefano Bonaglia, Erica Racchetti, Giuseppe Castaldelli, Volker Bruchert, Pierluigi Viaroli, Marco BartoliAbstract:Organic enrichment may deeply affect benthic nitrogen (N) cycling in macrophyte meadows, either promoting N loss or its recycling. This depends upon the plasticity of plants and of the associated microbial communities, as those surrounding the rhizosphere. Rates of denitrification, dissolved inorganic N fluxes and N uptake were measured in sediments vegetated by the submerged macrophyte Vallisneria spiralis L. under increasing organic matter loads. The aim was to investigate how the combined N assimilation and denitrification, which subtract N via temporary retention and permanent removal, respectively, do vary along the gradient. Results showed that V. spiralis meadows act as regulators of benthic N cycling even in organic enriched sediments, with negative feedbacks for eutrophication. A moderate organic load stimulates N uptake and denitrification coupled to nitrification in the rhizosphere. This is due to a combination of weakened competition between macrophytes and N cycling bacteria and enhanced radial oxygen loss by roots. An elevated organic enrichment affects N uptake due to hostile conditions in pore water and plant stress and impairs N mineralisation and its removal via denitrification coupled to nitrification. However, the loss of plant performance is almost completely compensated by increased denitrification of water column nitrate, resulting in a shift between the relative relevance of temporary and permanent N removal processes.
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Seasonal regulation of nitrification in a rooted macrophyte (Vallisneria spiralis L.) meadow under eutrophic conditions
Aquatic Ecology, 2014Co-Authors: Elisa Soana, Marco BartoliAbstract:Variable oxygen release from the root of macrophytes growing in ammonium-rich organic substrates can stimulate the process of nitrification. To verify this hypothesis, we performed seasonal measurements of potential nitrification activity in sediments with and without the perennial submersed plant Vallisneria spiralis L. (Hydrocharitaceae). Pore water and sediment features were simultaneously considered in order to provide insights into the regulation of the process. Results demonstrated a significant effect of season and plant presence on potential nitrification activity, with higher rates in winter and lower rates in summer. Vegetated sediment displayed lower pore water ammonium, but always higher potential nitrification activity compared to the unvegetated substrate, regardless the season. Nitrification activity was strongly correlated with pore water redox status, which were affected by both season and plant presence. Along its annual cycle V. spiralis promoted more oxidized conditions in the rhizosphere likely due to elevated radial oxygen loss and the consequent maintenance of a larger nitrifying community. These outcomes confirm the results of a limited number of studies that demonstrated how sediment biogeochemistry may be controlled by plant-released oxygen also in organic-rich systems.
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seasonal variation of radial oxygen loss in Vallisneria spiralis l an adaptive response to sediment redox
Aquatic Botany, 2013Co-Authors: Elisa Soana, Marco BartoliAbstract:In temperate shallow aquatic bodies large seasonal variations in water temperature result in a wide range of benthic respiration rates which are coupled to changes of pore water redox. To cope with such sediment modifications, we hypothesize that rooted macrophytes vary the oxygen amount released by roots. To this purpose, we reinterpreted published data on seasonal oxygen and inorganic carbon fluxes measured in vegetated (Vallisneria spiralis L.) sediments by combining them with the outcomes from laboratory incubations of apical tips and intact plants. Results suggest that V. spiralis transfers progressively higher amounts of oxygen to roots in the shift winter–summer. Maximum radial oxygen loss occurs in early autumn and probably overlaps with the lowest sediment redox. At the end of the summer, the exhaustion of energy yielding electron acceptor pools is in fact coupled to input of labile organic matter from senescent meadows, further exacerbating the demand of oxidized compounds to support degradation processes. The oxygen released by roots measured in hydroponic conditions corresponds to ∼7% of the plant gross production in the light; a small amount of oxygen is leaked also in darkness. We speculate that the oxygen injected in the pore water by a V. spiralis meadow can significantly affect the sediment biogeochemistry of eutrophic sites, representing up to ∼20% of the daily benthic oxygen consumption.
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effects of increasing organic matter loads on pore water features of vegetated Vallisneria spiralis l and plant free sediments
Ecological Engineering, 2012Co-Authors: Elisa Soana, Mariachiara Naldi, Marco BartoliAbstract:Abstract The effects of organic enrichment on pore water chemistry of bare and Vallisneria spiralis L. colonized sediments were investigated. Substrates of three organic levels were created by adding different amounts of powdered fish feed (0, 5 and 10 g/l of sediment, respectively) to homogenized sediment and incubated with and without plants. Redox potential (Eh), reduced compounds (CH4, Fe2+, Mn2+) and nutrients (PO43−, NH4+) were analyzed at time zero and after 6, 10, 13 and 17 days. In control microcosms V. spiralis sediments displayed significantly higher Eh and lower CH4, Fe2+, Mn2+, PO43− and NH4+ concentrations than bare ones. In organic enriched microcosms methanogenesis became the main degradation pathway when other electron acceptor pools were depleted. However, lower levels of interstitial Fe2+, Mn2+ and PO43− were found in vegetated sediments compared to bare ones and this difference was maintained during the whole experimental time. Root oxygen release in the rizosphere seemed to be the main responsible of this outcome, as also suggested by the nitrification potential assay, indicating the maintenance of oxic microniches. V. spiralis can act as an engineer species in urban, organic impacted sediments due to its high tolerance against reduced conditions, which makes this macrophyte an interesting option in aquatic ecosystems restoration programs.
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seasonal fluxes of o2 dic and ch4 in sediments with Vallisneria spiralis indications for radial oxygen loss
Aquatic Botany, 2011Co-Authors: Cristina Ribaudo, Marco Bartoli, Erica Racchetti, Daniele Longhi, Pierluigi ViaroliAbstract:Abstract Seasonal fluxes of dissolved oxygen, inorganic carbon and methane were measured in microcosms containing vegetated ( Vallisneria spiralis L.) and unvegetated sediments under controlled laboratory conditions. We tested if measured fluxes were affected by a moderate (6% as loss on ignition, LOI) and an elevated (10%) organic matter content (OM) in sediments. Microcosms were set up with plants and sediments collected from two riverine sites, upstream (moderate OM load) and downstream (elevated OM load) of a wastewater treatment plant. Light and dark fluxes were measured and V. spiralis net primary production and respiration rates were calculated. Unvegetated sediments were always net heterotrophic and behaved as methane sources to the water column, with significantly higher CH 4 release during summer from sediment with elevated OM load. Vegetated sediments were always net autotrophic with attenuated or negative CH 4 fluxes, suggesting the occurrence of processes within the rhizosphere that inhibit methane production or favor its oxidation. Vegetated sediments had an unbalanced O 2 to DIC stoichiometry, with average photosynthetic quotients varying between 0.30 and 0.68, significantly below one. The missing oxygen amount varied seasonally, with a minimum in the summer coinciding with the highest water temperature, but was not dependent upon the two OM levels. Overall these results suggest that V. spiralis is likely to transport a significant proportion of photosynthetically produced oxygen to the rhizosphere.
Meetu Gupta - One of the best experts on this subject based on the ideXlab platform.
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lead mediated synthesis of metal binding peptides phytochelatins in aquatic plant Vallisneria spiralis l
2000Co-Authors: Meetu Gupta, U N Rai, R. D. Tripathi, P ChandraAbstract:Pollution of the biosphere with toxic metals has increased dramatically since the beginning of industrial revolution. The sources of lead (Pb) contamination include metal smelting, Pb based paints, lead arsenate, pesticide and phosphate fertilizers (Singh et al., 1997). Another major source is Pb alkyl derivatives in gasoline which are cracked to release Pb in automobile exhaust in the form of lead aerosols. Recently Pb was found to be a major contaminant of ponds (Chandra et al., 1993) and lakes (Tripathi et al., 1997). Plants have been used to decontaminate Pb from contaminated environment (Gupta & Chandra, 1994; Gupta et al., 1995; Rai et al., 1995a; Boyajian & Carreira, 1997).
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bioaccumulation and toxicity of mercury in rooted submerged macrophyte Vallisneria spiralis
Environmental Pollution, 1998Co-Authors: Meetu Gupta, P ChandraAbstract:Abstract Laboratory experiments were carried out to determine mercury (Hg) accumulating potential and toxicity in the submerged aquatic macrophyte Vallisneria spiralis . Young plants were subjected to different concentrations (0.5, 1.0, 5.0, 10, 20 μM) of Hg for 24, 48, 96 and 168 h. Plants showed a Hg accumulation of 0.25 μmol/g dry weight in leaf and 1.12 μmol/g dry weight in roots, respectively, at 20 μM Hg after 168 h. The chlorophyll, protein and nitrogen, phophorus, potassium contents decreased significantly with increasing Hg concentrations and treatment durations. In vivo nitrate reductase activity also decreased from the lowest concentration of Hg to the highest. Cysteine content of leaf and root material increased at low Hg concentration and then significantly declined at higher doses of Hg. The results suggested a strong uptake potential for Hg by the roots which can act to monitor metal contamination in the environment, although the negative physiological implications cannot be ruled out, which are relevant for transfer of metal via food chain at different trophic levels.
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role of glutathione and phytochelatin in hydrilla verticillata i f royle and valusneria spiraus l under mercury stress
Chemosphere, 1998Co-Authors: Meetu Gupta, U N Rai, R. D. Tripathi, P ChandraAbstract:Abstract Both free (Hydrilla verticillata) and rooted (Vallisneria spiralis) submerged plants showed high potential to accumulate mercury, maximum being in roots of V. spiralis. During mercury stress these plants synthesized different species of phytochelatins (PCs), which bind with the accumulated mercury and showed high levels of cysteine and non-protein thiols. The induction of phytochelatins was accompanied by a decline in cellular levels of glutathione in both the plants, although the decline was only observed at high concentration and long duration of Hg in V. spiralis. Buthionine sulfoximine inhibited accumulation of non-protein thiols and glutathione, indicating the involvement of glutathione in phytochelatin synthesis. However, cycloheximide had no effect on early PC synthesis. Results showed that phytochelatins are synthesized in these plants and play a role in mercury detoxification.
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lead accumulation and toxicity in Vallisneria spiralis l and hydrilla verticillata l f royle
Journal of Environmental Science and Health Part A-toxic\ hazardous Substances & Environmental Engineering, 1994Co-Authors: Meetu Gupta, P ChandraAbstract:Abstract Lead uptake potential of two aquatic macrophytes Vallisneria spiral is and Hvdrilla verticillata were determined in solution cultures under the laboratory conditions. Both the plants showed substantial accumulation of Pb, though it was more in H. verticillata. Accumulation was more in the roots of V. spiralis. Metal toxicity was largely insignificant at lower ambient concentrations. At higher Pb level (100 μM), inhibition in chlorophyll and protein content, in vivo nitrate reductase activity was recorded. Feasibilty of using both plants individually and in combination, for reducing Pb level in the water bodies has been suggested.
Lei Zeng - One of the best experts on this subject based on the ideXlab platform.
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enhanced degradation of pyrene and phenanthrene in sediments through synergistic interactions between microbial fuel cells and submerged macrophyte Vallisneria spiralis
Journal of Soils and Sediments, 2019Co-Authors: Enrong Xiao, Lei ZengAbstract:Submerged macrophyte Vallisneria spiralis and sediment microbial fuel cell (SMFC) systems are cost-effective methods for the remediation of polycyclic aromatic hydrocarbon (PAH)–polluted sediments. This study evaluates whether the combination of these two ecological approaches could further improve the removal efficiency of PAHs from sediments and investigates the possible mechanisms of removal. Sediments, macrophytes, electrodes, and plexiglass columns were used to construct an experimental microcosm. A 65-day comparative study was performed with six treatments as follows: SMFC without PAH (SMFC); PAH only (PAH); SMFC with PAH (SMFC-PAH); V. spiralis without PAH (macrophyte); V. spiralis with PAH (macrophyte-PAH); V. spiralis with SMFC and PAH (M-SMFC-PAH). Pyrene and phenanthrene were added to raw sediments to obtain initial PAH concentrations of 10 mg kg−1 dry sediment. The monitored parameters were sediment oxidation–reduction potential (ORP); low molecular weight organic acids (LMWOAs) and Fe (II) concentrations in pore water; electron acceptor (sulfate and Fe (III)), humic acid (HA), and PAH concentrations in sediments; and plant morphology and root physiology. High-throughput 16S rRNA gene sequencing was also performed to assist mechanistic understanding. The M-SMFC-PAH treatment obtained the highest sediment ORP and PAH removal efficiency. The average ORP level in M-SMFC-PAH was increased by 57.2, 59.1, and 168.4 mV, compared with the SMFC-PAH, macrophyte-PAH, and PAH-only treatments, respectively, with a mean value of 121.7 mV observed during the whole experimental period. The pyrene (phenanthrene) dissipation ratios at the end of the experimental period were 29.1% (35.4%), 45.5% (56.3%), 59.8% (67.3%), and 79.4% (88.2%) for PAH only, SMFC-PAH, macrophyte-PAH, and M-SMFC-PAH treatments, respectively. The highest correlation was observed between PAH concentration and sediment ORP value, in the coupled M-SMFC-PAH system. Results suggest that the interactions between the anode and rhizosphere of V. spiralis were synergistic during PAH removal. The coexistence of anodic and rhizospheric oxygen loss in sediments had a synergistic effect on PAH degradation. Plant presence facilitated the electrogenic degradation of PAHs. The inhibited growth of V. spiralis due to PAH toxicity was reduced by electrogenesis, thus facilitating the removal of vegetable PAHs from sediments. Coordinated growth of anaerobic and aerobic PAH degrading bacteria on the anode was a key factor in the optimal removal of PAHs in coupled systems.
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synergistic removal effect of p in sediment of all fractions by combining the modified bentonite granules and submerged macrophyte
Science of The Total Environment, 2018Co-Authors: Chuan Wang, Z Q Liu, Yi Zhang, Biyun Liu, Qiaohong Zhou, Lei ZengAbstract:Abstract The removal efficiency of sediment phosphorus (P) with the in-situ synergistic effect of modified bentonite granules (MBG) and Vallisneria spiralis (V. spiralis) in West Lake, Hangzhou, China was investigated for the first time in the study. CMBG-Na10-450 (nitrification (10% Na2CO3)-calcination (450 °C) combined modification) was prepared and characterized, and the removal effects of sediment P of all fractions with CMBG-Na10-450 and V. spiralis in combination and separately were evaluated in batch experiments. Results showed that CMBG-Na10-450 could promote the growth of V. spiralis, and the residual P of the sediment not adsorbed on CMBG-Na10-450 was changed through root oxygenation and nutrition allocation, and then enhanced the extra P adsorption on CMBG-Na10-450. The combination of MBG and V. spiralis exhibited a synergistic removal effect higher than the summation of MBG and V. spiralis applied separately. The results of microcosm experiments showed that the combination of CMBG-Na10-450 and V. spiralis enhanced the function of P metabolism by increasing the special genus that belongs to the family Erysipelotrichaceae.
