Linking fluorescent dissolved organic matters to microbial carbon metabolism in the overlying water during submerged macrophyte Potamogeton crispus L decomposition in the presence/absence of Vallisneria natans.

Multi-species submerged plants grow with succession patterns in the same habit and play an important role in the aquatic ecosystems. The decomposition of submerged plants in aquatic environments was a disturbance that affected the water quality and microbial community structures. However, the responses of the microbial community function in surface water to the disturbance remain poorly understood. In this study, the effects of submerged macrophyte Potamogeton crispus L decomposition on the water quality and microbial carbon metabolism functions (MCMF) in the overlying water were investigated in the presence/absence of Vallisneria natans. The result showed that the decomposition rapidly released a large amount of organic matter and nutrients into the overlying water. The presence of Vallisneria natans promoted the removal of dissolved organic carbon and fluorescent component C3, resulting in lower values of the percentage content of C3 (C3%). Under various decomposition processes, the MCMF changed over time and significantly negatively correlated with C3%. The functional diversity of MCMF significantly correlated with the fluorescence organic matters, such as the richness and Simpson index correlated with the amount of C1, C1+C2+C3, and C3%. But UV-visible absorption indexes and nutrients in the overlying water had no relationship with the MCMF, except for the total nitrogen correlated with the richness. These results suggested that under various decomposition conditions, the fluorescent dissolved organic matter could be used as an indicator for quick prediction of MCMF in surface water.

Antioxidant Effects of Rhodoxanthin from Potamogeton crispus L. on H2 O2 -Induced RAW264.7 Macrophages Cells.

Potamogeton crispus L. (P. crispus) is the type of a widely distributed perennial herbs, which is rich in rhodoxanthin. In this research work, five antioxidant indexes in vitro were selected to study the antioxidant activity of rhodoxanthin from P. crispus (RPC). A model of hydrogen peroxide (H2 O2 ) -induced oxidative damage in RAW264.7 cells was established to analyze the antioxidant effect and potential mechanism of RPC. The levels of ROS, MDA and the activities of oxidation related enzymes by H2 O2 were determined by enzyme linked immunosorbent assay (ELISA). The mRNA expression of Nrf-2, HO-1, SOD1 and SOD2 was measured by qRT-PCR assay. According to the results, RPC had free radical scavenging ability for 2, 2-diphenyl-1-trinitrohydrazine (DPPH), 2,2'-azinobis(3-ethylbenzo-thiazoline-6-sulfonic acid radical ion) (ABTS), hydroxyl radical and superoxide anion. RPC significantly decreased the level of MDA and ROS and LDH activity, while increased GSH level and activities of SOD, GSH-Px and CAT. It was showed that RPC could increase the mRNA expression of Nrf-2, HO-1, SOD1 and SOD2 in RAW264.7 cells in a dose-dependently manner. In summary, RPC treatment could effectively attenuate the H2 O2 -induced cell damage rate, and the mechanism is related to the reduction of H2 O2 induced oxidative stress and the activation of Nrf-2 pathway.

Eutrophication triggers the shift of nutrient absorption pathway of submerged macrophytes: Implications for the phytoremediation of eutrophic waters.

Ecologically restoring eutrophic water bodies by using submerged macrophytes is an economical, effective and sustainable technology worldwide. However, current understanding on the nutrient absorption pathway of submerged macrophytes in freshwater ecosystems, especially under different trophic states, is still limited. In this study, two strategically designed systems were established to form isolated units for preventing nutrient exchange amongst Potamogeton crispus, water column and sediments. Results showed that, in oligotrophic state, P. crispus mainly relied on their roots to absorb nutrients from sediments for maintaining stable growth, with the maximum average height, fresh weight and relative growth rate of 12.85 cm, 4.86 g ind-1 and 0.062, respectively. However, the eutrophic conditions (TN of 4 mg L-1 and TP of 0.3 mg L-1) triggered the shift of the nutrient absorption pathway from the roots to the shoots to some extent, that is, the shoots of P. crispus gradually became a remarkable pathway to directly absorb nutrients from the water column. Approximately 49.85% and 18.35% of total nitrogen (TN) and total phosphorus (TP) from overlying water were allocated to the shoots of P. crispus, but had no effects on the growth, photosynthesis and ecological stoichiometric differences (p > 0.05). Sediments acting as a nitrogen (N) source supported nearly 11.56% of TN for shoot uptake and simultaneously received around 13.33% of TP subsidy from the overlying water. The no longer sole dependence of submerged macrophytes on their root system to absorb N and phosphorus nutrients indicated that the ability of shoots to absorb nutrients increased with the gradual increase in nutrients in water column. These findings imply that the large specific surface area of shoots is beneficial for restoring eutrophic waters.

Accumulation and effects of copper on aquatic macrophytes Potamogeton pectinatus L.: Potential application to environmental monitoring and phytoremediation.

This study investigated the ability of Potamogeton pectinatus L. to accumulate copper and its effects on plants. In accumulation tests, macrophytes were exposed (96 h) to different copper concentrations (0-1000 µM) and the metal was measured in media and plant tissues (roots, stems and leaves) to determine the bioconcentration factor (BCF). Plants accumulated high concentrations of copper in a dose-dependent manner and roots was the main organ for copper accumulation. However, the more copper increased in water, the more BCF values decreased. It may be due to either saturation of copper uptake or down-regulation of metal uptake by plants. In the physiological and morphological analyses, plants were kept (96 h) in Hoagland nutrient solution without copper, in full Hoagland solution (0.5 µM Cu) and in Hoagland medium with copper from 1 to 100 µM. The absence and the presence of copper above to 1 µM inhibited photosynthesis. Chlorophylls and carotenoid levels also decreased with the excess of copper, a fact that may have affected the photosystem II-dependent of chlorophyll and caused photosynthesis suppression. Only macrophytes at 10 µM Cu showed decrease in length and number of leaves on the 10th day of the test, when they died. Chlorosis and necrosis were observed in control groups and groups with extra copper, but not in Hoalgand group. Overall, the macrophyte P. pectinatus can be considered a suitable plant for monitoring environments contaminated by copper, based on results of copper accumulation in the plant, decrease in pigment concentration and presence of chlorosis and necrosis. However, values of BCF based on fresh water tissues was not proper to indicate the use of P. pectinatus for cleaning environments contaminated by copper.

Influence of Different Electron Acceptors on the Anaerobic Degradation of Curly-Leaf Pondweed.

Curly-leaf pondweed (Potamogeton crispus) was utilized as the representative to investigate the biodecomposition process of aquatic plants under different reducible conditions. Results showed that the methane production was inhibited when different electron acceptors (Fe(III), and ) were available. The methane production was decreased by 57% when Fe(III) and or were both available compared to the control. The degradation efficiency of hemicellulose and lignin with Fe(III) and were increased significantly. This provided a theoretical basis for slowing down the emissions of methane.

Single and combined phytoextraction of lead and cadmium on submerged plants Potamogeton pusillus L.: removal, bioaccumulation pattern, and phytotoxicity.

Under the present investigation, the submerged plant Potamogeton pusillus has been tested for the removal of lead (Pb) and cadmium (Cd). P. pusillus removal efficiency and accumulation capacity were examined in separated Pb and Cd solutions, at 0.5, 1.0, and 2 mg L-1, and in solutions where both metals were present at the same concentration (0.5, 1.0, and 2 mg L-1), under laboratory conditions for 3, 7, and 10 days. Also, we examined the removal efficiency and accumulation capacity when a set of plants were exposed to 0.5 mg L-1 of Pb (or Cd) and increasing concentrations (0.5, 1, and 2 mg L-1) of Cd (or Pb) for 10 days. The effect of Cd and Pb was assessed by measuring changes in the chlorophylls, carotenoids, and malondialdehyde contents. Results showed that P. pusillus could accumulate Cd and Pb from individual solutions. Roots and leaves accumulated the highest amount of Cd and Pb followed by the stems. Some phytotoxic effects were observed, especially at individual Cd exposures, but these effects were not observed in the two-metal system. The removal and accumulation of Pb by P. pusillus were significantly enhanced in the presence of Cd under certain conditions, presenting a good alternative for the removal of these metals from polluted aquifers. To the extent of our knowledge, this is the first report on both enhanced phytoextraction of Pb in the presence of Cd and bioaccumulation of these heavy metals by P. pusillus.

Phosphate-solubilizing bacteria improve the antioxidant enzyme activity of Potamogeton crispus L. and enhance the remediation effect on Cd-contaminated sediment.

Phosphorus-solubilizing bacteria (PSB) assisted phytoremediation of cadmium (Cd) pollution is an effective method, but the mechanism of PSB-enhanced in-situ remediation of Cd contaminated sediment by submerged plants is still rare. In this study, PSB (Leclercia adecarboxylata L1-5) was inoculated in the rhizosphere of Potamogeton crispus L. (P. crispus) to explore the effect of PSB on phytoremediation. The results showed that the inoculation of PSB effectively improved the Cd extraction by P. crispus under different Cd pollution and the Cd content in the aboveground and underground parts of P. crispus all increased. The µ-XRF images showed that most of the Cd was enriched in the roots of P. crispus. PSB especially showed positive effects on root development and chlorophyll synthesis. The root length of P. crispus increased by 51.7 %, 80.5 % and 74.2 % under different Cd pollution, and the Ca/Cb increased by 38.9 %, 15.2 % and 8.6 %, respectively. Furthermore, PSB enhanced the tolerance of P. crispus to Cd. The contents of soluble protein, MDA and H2O2 in 5 mg·kg-1 and 7 mg·kg-1 Cd content groups were decreased and the activities of antioxidant enzymes were increased after adding PSB. The results showed that the application of PSB was beneficial to the in-situ remediation of submerged plants.

Effects of ROS and caspase-3-like protein on the growth and aerenchyma formation of Potamogeton perfoliatus stem.

Aerenchyma formation plays an important role in the survival of Potamogeton perfoliatus in submerged environment. To understand the regulatory role of reactive oxygen species (ROS) and caspase 3-like protein signaling molecules in aerenchyma formation, we investigated the effects of exogenous NADPH oxidase inhibitor (diphenyleneiodonium chloride, DPI), catalase inhibitor (3-amino-1,2,4-triazole, AT), and caspase-3-like protein inhibitor (AC-DEVD-CHO, DEVD) on morphological and physiological characteristics and aerenchyma formation in P. perfoliatus. The results showed that after DPI treatment, caspase-3-like protein activity decreased, ROS-related enzyme activities increased, and H2O2 content decreased, thereby inhibiting aerenchyma formation. When the concentration of DPI was approximately 1 µmol/L, the inhibitory effect was the most obvious. On the contrary, after the AT treatment, caspase-3-like protein activity increased, ROS-related enzyme activities decreased, and the H2O2 content increased, ultimately promoting aerenchyma formation, and the promotion was the most obvious under treatment with approximately 500 µmol/L AT. After DEVD treatment, the inhibition of vegetative growth caused by DPI or AT treatment was alleviated, significantly reducing caspase-3-like activity and inhibiting aerenchyma development. The results of this study show that ROS has a positive regulatory effect on aerenchyma formation, and caspase-3-like protein is activated to promote ROS-mediated aerenchyma formation. This experiment provides a new theoretical basis for further exploration of the signal transduction effects of ROS and caspase-3-like protein in plant cells and their roles in plant development.

Comparative studies of thermotolerance: different modes of heat acclimation between tolerant and intolerant aquatic plants of the genus Potamogeton.

BACKGROUND AND AIMS: Molecular-based studies of thermotolerance have rarely been performed on wild plants, although this trait is critical for summer survival. Here, we focused on thermotolerance and expression of heat shock transcription factor A2 (HSFA2) and its putative target gene (chloroplast-localized small heat shock protein, CP-sHSP) in two allied aquatic species of the genus Potamogeton (pondweeds) that differ in survival on land. METHODS: The degree of thermotolerance was examined using a chlorophyll bioassay to assess heat injury in plants cultivated under non- and heat-acclimation conditions. Potamogeton HSFA2 and CP-sHSP genes were identified and their heat-induction was quantified by real-time PCR. KEY RESULTS: The inhibition of chlorophyll accumulation after heat stress showed that Potamogeton malaianus had a higher basal thermotolerance and developed acquired thermotolerance, whereas Potamogeton perfoliatus was heat sensitive and unable to acquire thermotolerance. We found two duplicated HSFA2 and CP-sHSP genes in each species. These genes were induced by heat shock in P. malaianus, while one HSFA2a gene was not induced in P. perfoliatus. In non-heat-acclimated plants, transcript levels of HSFA2 and CP-sHSP were transiently elevated after heat shock. In heat-acclimated plants, transcripts were continuously induced during sublethal heat shock in P. malaianus, but not in P. perfoliatus. Instead, the minimum threshold temperature for heat induction of the CP-sHSP genes was elevated in P. perfoliatus. CONCLUSIONS: Our comparative study of thermotolerance showed that heat acclimation leads to species-specific changes in heat response. The development of acquired thermotolerance is beneficial for survival at extreme temperatures. However, the loss of acquired thermotolerance and plasticity in the minimum threshold temperature of heat response may be favourable for plants growing in moderate habitats with limited daily and seasonal temperature fluctuations.

Removal of fluoride from water by five submerged plants.

Studies were conducted on the bioconcentration of fluoride (F(-)) in five submerged plants species. Ceratophyllum demersum, Hydrilla verticillata, Potamogeton malaianus, Myriophyllum verticillatum and Elodea nuttallii were all able to remove F(-) from water to some degree of efficiencies. At 5-20 mg F(-)/L culture solution, C. demersum had the best F(-)-removal performance, E. nuttallii had the poorest F(-)-removal performance among these plants. The relative growth rate (RGR) of the five species varied in different concentrations of F(-), of which C. demersum had the highest RGR. Its RGR decreased by 26.3 %, 63.2 % and 73.7 % from controls at 5, 10 and 20 mg F/L, respectively.

Photosynthetic performance of the aquatic macrophyte Althenia orientalis to solar radiation along its vertical stems.

We have studied the plasticity of the photosynthetic apparatus in the endangered aquatic macrophyte Althenia orientalis to the gradient of light availability within its meadow canopy. We determined diurnal change in situ irradiance, light quality, in vivo chlorophyll a fluorescence, ex situ oxygen evolution rates, respiration rate and pigment concentration. The levels of photosynthetic photon flux density (PFD) and ultraviolet radiation (UVR) and the red/far-red ratio decreased with depth within the canopies of A. orientalis. Apical leaves had a greater decrease of the maximal quantum yield (F(v)/F(m)) in the morning and a faster recovery rate in the afternoon than those in the basal ones. The relative electron transport rate (ETRr) was not saturated at any time of the day, even in the apical leaves that received the highest light. The maximum light-saturated rate of gross photosynthesis (GP(max)) took place in apical leaves around noon. The chlorophyll a/b ratio values were higher, and the chlorophyll/carotenoid ratio values lower, in apical leaves than basal ones. The highest concentrations in total carotenoids were reached in the apical leaves around noon. A. orientalis has a high capacity to acclimatize to the changes in the light environment, both in quality and quantity, presenting sun and shade leaves in the same stem through the vertical gradient in the canopy.

Metabolic and biochemical responses of Potamogeton anguillanus Koidz. (Potamogetonaceae) to low oxygen conditions.

Oxygen availability in water is considered one of the most important factors for growth and productivity in aquatic submerged macrophytes. In the present study, the growth, stress responses, and metabolic changes in Potamogeton anguillanus Koidz. (Potamogetonaceae) were assessed after a 21-day exposure to low (hypoxia; dissolved oxygen, DO < 1 mg/L) or null (anoxia) oxygen concentrations in water. High growth rates and an increased indole acetic acid (IAA) content in P. anguillanus were observed under the hypoxic conditions (4-fold to control) compared to the anoxic conditions. In addition, the activation of glycolysis and fermentation processes was further recorded, given the increase in alcohol dehydrogenase activity and pyruvate concentration on the studied plants that were exposed to low oxygen concentrations. Moreover, the positive correlations of antioxidative enzyme activities, catalase (CAT) and guaiacol peroxidase (POD) with hydrogen peroxide (H2O2) confirmed the species ability to scavenge excess H2O2 under low oxygen stress. The capillary electrophoresis-mass spectrometry (CE-MS) analysis of the metabolome identified metabolite accumulations (e.g., glutamate, glutamine, aspartate, asparagine, valine, malate, lactate, citrate, isocitrate, proline and γ-amino butyric acid) in response to the anoxia.

Rare-earth element yttrium enhances the tolerance of curly-leaf pondweed (Potamogeton crispus) to acute nickel toxicity.

Nickel is a ubiquitous heavy-metal pollutant in lakes and severely affects aquatic organisms. Aquatic plants are often initially linked to having heavy metal contents and further are proposed as phytoremediation agent to remove heavy metal from water. Although the toxic effects of nickel on aquatic plants are thoroughly explored, the effective investigation to increase Ni tolerance is still in its infancy. The role of rare-earth elements (REEs) in plant resisting heavy-metal pollution has recently received considerable interest. To explore the physiological effects of REEs on Potamogeton crispus under Ni stress, we explored whether or not the additive exposure to low-dose yttrium (Y; 2.5 µM) promotes the polyamine metabolism, antioxidation, and photosynthesis performance of P. crispus under Ni stress values of 0, 50, 100, 150, and 200 µM. Results showed that Y exposure did not influence Ni bioaccumulation in P. crispus. Furthermore, Y exposure alleviated the adverse effects of Ni stress to convergent degrees because Y positively converts putrescine into spermidine and spermine, inhibits oxidative stress, increases the total chlorophyll content, and maximum/potential quantum efficiency of photosystem II. We concluded that low-dose Y can positively regulate polyamine transformation, inhibit oxidative stress, stimulate photosynthesis, and finally promote the resist ability of P. crispus to nickel stress. Thus, REEs have potential to be applied in regulating submerged plant tolerance to aquatic heavy-metal pollution.

Nitrogen release and its influence on anammox bacteria during the decay of Potamogeton crispus with different values of initial debris biomass.

Aquatic macrophytes play a significant role in the nutrient cycle of freshwater ecosystems. However, nutrients from plant debris release into both sediments and overlying water if not timely harvested. To date, minimal information is available regarding nutrient release and its subsequent influences on bacterial communities with decaying debris. In this study, Potamogeton crispus was used as a model plant. Debris biomass levels of 0 g (control, J-CK), 10 g dry weight (DW) (100 g DW/m2, J-10 g), 40 g DW (400 g DW/m2, J-40 g) and 80 g DW (800 g DW/m2, J-80 g) were used to simulate the different biomass densities of P. crispus in field. The physicochemical parameters of overlying water and sediment samples were analysed. The community composition of anammox bacteria in the sediment was also analysed using 16S rRNA genes as markers. The results showed that dissolved oxygen and pH dramatically decreased, whereas total nitrogen (TN) and NH4+-N concentrations increased in the overlying water in the initial stage of P. crispus decomposition. However, NO3--N concentration changes in the overlying water were more complicated. The concentrations of organic matter, TN and NH4+-N in the sediment all increased, but the rate of increase varied among the groups with different initial biomass levels, indicating that these physicochemical properties in sediment are significantly affected by debris biomass level and decay time. In addition, the order of anammox bacteria abundance was J-40 g > J-CK > J-80 g > J-10 g. Moreover, the community structure of anammox bacteria were simpler compared to that of J-CK as debris biomass level increased. The results demonstrate that P. crispus debris decomposition could affect the ecological distribution of anammox bacteria. Such influence clearly varies with varying amounts of P. crispus biomass debris. This information could be useful for the management of aquatic macrophytes in freshwater ecosystems.

Bioaccumulation of heavy metals by the aquatic plants Potamogeton pectinatus L. and Potamogeton malaianus Miq. and their potential use for contamination indicators and in wastewater treatment.

The concentrations of heavy metals in the leaves of two aquatic plants Potamogeton pectinatus L. and Potamogeton malaianus Miq., and the corresponding water and sediment samples from the Donghe River in Jishou City of Hunan Province, China were studied to investigate metal contamination from the intensive industrial activities in the surrounding area. Results showed that the concentrations of heavy metals in the sediments, especially Cd, Mn and Pb, were much higher than the eco-toxic threshold values developed by the U. S. Environmental Protection Agency. Between the two plant species, P. pectinatus showed the higher capacity in metal accumulation. The highest concentrations of Cd, Pb, Cu, Zn and Mn were found in the leaves of P. pectinatus, reaching 596, 318, 62.4, 6590 and 16,000 mg kg(-1) (DW), respectively. Significantly positive relationships were observed among the concentrations of Zn, Cu and Mn in the leaves of both aquatic plants and those in water, indicating the potential use of the two plants for pollution monitoring of these metals. In addition, a laboratory experiment was conducted to investigate the ability of P. pectinatus and P. malaianus to remove heavy metals from contaminated river water. The average removal efficiencies by P. pectinatus and P. malaianus for Cd, Pb, Mn, Zn and Cu from the spiked Donghe River water were 92%, 79%, 86%, 67% and 70%, respectively. The results indicated that P. pectinatus and P. malaianus had high capabilities to remove heavy metals directly from the contaminated water. The potential use of these plants in wastewater treatment is worth further exploration.

Removal of cadmium by Myriophyllum heterophyllum Michx. and Potamogeton crispus L. and its effect on pigments and total phenolic compounds.

In this study, cadmium biosorption by Myriophyllum heterophyllum Michx. and Potamogeton crispus L. was investigated. Although both species were found to be capable of removing cadmium from water, the performance of P. crispus was the most significant. These species were treated with 0, 4, 8, 16, 32, and 64 mg L(-1) cadmium solutions for 24, 48, 72, and 96 h, respectively. Cadmium uptake of both species was lowest at 4 mg L(-1 )and highest at 64 mg L(-1). Photosynthetic pigments and total phenolic compounds in both species were determined after exposure to various concentrations of cadmium for various times. Depending on the cadmium accumulation in both species, it was shown to decrease the level of chlorophyll a, chlorophyll b, and carotenoids (24 and 96 h). The anthocyanin concentration in P. crispus increased at all cadmium concentrations studied (0, 4, 8, 16, 32, and 64 mg L(-1)), whereas in Myriophyllum heterophyllum it increased at the lower cadmium concentrations (0, 4, and 8 mg L(-1)) but decreased at higher cadmium concentrations (16, 32, and 64 mg L(-1)), for all exposure periods. The total phenolic compound level in both species increased with cadmium concentration during the 24 and 96 h exposure periods.

Toxicity of linear alkylbenzene sulfonate to aquatic plant Potamogeton perfoliatus L.

Aquatic plants play an important role in maintaining the health of water environment in nature. Studies have shown that linear alkylbenzene sulfonate (LAS), a type of omnipresent pollutant, can cause toxic damage to aquatic plants. In the present research, we studied the physiological and growth response of submerged plant Potamogeton perfoliatus L. to different concentrations of LAS (0.1, 1.0, 10.0, 20.0, and 50.0 mg l-1). The results showed that LAS is toxic to P. perfoliatus, and the toxicity is dose-dependent. Only slightly reversible oxidative damages were observed in the physiological parameters of P. perfoliatus when P. perfoliatus was exposed to lower LAS doses (< 10 mg l-1): soluble sugar, soluble protein, H2O2, and malondialdehyde (MDA) content in P. perfoliatus increased significantly at 0.1 mg l-1 and then returned to normal levels at 1.0 mg l-1. Antioxidant enzymes were activated before the LAS concentration reached 10 mg l-1, and the activities of superoxide dismutase (SOD), catalase (CAT), and photosynthesis pigment content declined significantly when the concentration of LAS exceeded 10 mg l-1. In addition, at higher concentrations (20-50 mg l-1) of LAS, dry weight and fresh weight of P. perfoliatus showed significant declines. The results indicate that LAS above 10 mg l-1 can cause serious physiological and growth damage to P. perfoliatus.

Spatial (bio)accumulation of pharmaceuticals, illicit drugs, plasticisers, perfluorinated compounds and metabolites in river sediment, aquatic plants and benthic organisms.

Organic contaminants such as pharmaceuticals, personal care products (PPCPs) and other emerging contaminants (ECs) are known to persist in the aquatic environment and many are indicated as endocrine, epigenetic, or other toxicants. Typically, the study of PPCPs/ECs in the aquatic environment is limited to their occurrence dissolved in river water. In this study, accumulation and spatial distribution of thirteen PPCPs/ECs were assessed in aquatic sediment (n = 23), periphyton (biofilm, n = 8), plants Callitriche sp. (n = 8) and Potamogeton sp. (n = 7) as well as amphipod crustaceans (Gammarus pulex, n = 10) and aquatic snails (Bithynia tentaculata, n = 9). All samples (n = 65) were collected from the Hogsmill, Blackwater and Bourne Rivers in southern England. Targeted PPCPs/ECs included pharmaceuticals, plasticisers, perfluorinated compounds, illicit drugs and metabolites. Extraction from solid matrices occurred using ultrasonic-assisted extraction followed by an in-house validated method for solid-phase extraction and subsequent liquid-chromatography tandem mass-spectrometry. Field-derived bioconcentration-factors and biota-sediment accumulation-factors were determined for all studied biota. Residues of studied contaminants were found in all sediment and biota. Concentrations of contaminants were generally higher in biota than sediment. Evidence suggests that the studied aquatic plants may effectively degrade bisphenol-A into its main transformation product hydroxyacetophenone, potentially mediated by cytochrome p450 and internalisation of contaminants into the cellular vacuole. A positive association between both hydrophobicity and PFC chain length and contaminant accumulation was observed in this work. Only PFCs, plasticisers and HAP were classified as either 'bioaccumulative' or 'very bioaccumulative' using BCF criteria established by guidelines of four governments. Contaminants appeared to be differentially bioaccumulative in biota, indicating there may be a need for a species-specific BCF/BSAF classification system. These data form a detailed accounting of PPCP/EC fate and distribution in the aquatic environment highlighting accumulation at lower trophic levels, a potential source for higher organisms.

[Comparison of Nitrogen and Phosphorus Uptake and Water Purification Ability of Five Submerged Macrophytes].

Uptake of nitrogen (N) and phosphorus (P) and their purification capacity for five native submerged macrophytes were investigated in laboratory simulated hydrostatic conditions,including Hydrilla verticillata,Vallisneria natans,Ceratophyllum demersum,Myriophyllum spicatum,Potamogeton maackianus.The results indicated that the moisture contents of different submerged macrophytes were almost the same before and after the test,with the range of 89.8%-92.0%.The net accumulated biomass changed from 1.52 g·m-2 to 12.92 g·m-2 among different submerged macrophytes,and the highest net accumulated biomass of Hydrilla verticillata was 8.5 times higher than the lowest plant of Potamogeton maackianus.The N and P contents of five submerged macrophytes ranged from 26.54 to 34.44g·kg-1 and from 2.54 to 4.01g·kg-1,respectively,and the N and P contents of Ceratophyllum demersum were relatively high.Total N and P removal efficiency of different submerged macrophyte treatments had ranges of 63.8%-83.1% and 49.2%-70.8%,significantly higher than those of the CK treatment (39.9% and 36.9%),respectively,and the removal efficiency decreased in the order of Hydrilla verticillata >Ceratophyllum demersum >Vallisneria natans >Myriophyllum spicatum >Potamogeton maackianus.Total N and P removal efficiencies of different submerged macrophyte treatments were significantly correlated with net accumulated biomass,with correlation coefficients of 0.994(P<0.01) and 0.996(P<0.01).The contribution of direct N and P uptake to different submerged macrophytes had the ranges of 1.5%-13.3% and 2.2%-13.2%,and the synergism contribution (deducting self-purification capacity of water) of different submerged macrophytes ranged 22.5%-29.9% and 10.1%-20.6%,indicating that the synergistic effect of submerged macrophytes purification was much more significant than the direct uptake effect in the process of water purification.

Effect of Potamogeton crispus L. on bioavailability and biodegradation activity of pyrene in aged and unaged sediments.

In order to clarify the effect of Potamogeton crispus L. (P. crispus) on bioavailability and biodegradation activity of pyrene in aged and unaged sediments, model calculation based on experimental results was carried out. During a 36-day experiment, the dissipation ratio of pyrene was increased by planting but decreased by aging. P. crispus improved the dissipation more significantly in aged sediments (45.9%) than in unaged sediments (17.6%). Results derived from a two-compartment desorption model showed that the decrease of rapidly desorbing fraction of pyrene was in the order of aged sediments without plant (A)>unaged sediments without plant (U)>unaged sediments with plant (UP)>aged sediments with plant (AP). Moreover, the results of biodegradation kinetic model showed that the first-order biodegradation coefficient was in the order of AP>UP>U and A, which was consistent with that of sediment redox potential. These modeling results indicated that planting could enhance the bioavailability (73.9%) and biodegradation activity (277%) of pyrene more significantly in aged sediments as compared to unaged sediments (13.1% and 150%, respectively), which should be the key reasons leading to more significant dissipation increment of pyrene in aged sediments by P. crispus.