This study investigated the change in denitrification rate in muddy tidal flats sediment by chemical and biological remediation. Column experiments were conducted to determine the dependence of denitrification rate on...This study investigated the change in denitrification rate in muddy tidal flats sediment by chemical and biological remediation. Column experiments were conducted to determine the dependence of denitrification rate on the redox potential. Filtered seawater was fed continuously to the pipe filled with sediment from the muddy tidal flats. An increase in the redox potential from -198 mV to 21 mV with bioturbation led to increases in the denitrification rate from 24.2 mg/m2/day to 29.8 mg/m2/day. The increase in denitrification was explained by the acceleration of mass transfer in the sediment. Redox-potential increased from -400 mV to -200 mV by the addition of 10 g calcium nitrate, acid volatile sulfide was below the detection limit to 20 cm depth, and denitrification rate was increased from 21.3 mg/m2/day to 36.4 mg/m2/day. It is considered that the increased nitrogen concentration led to an increase in microbial activity.展开更多
Cocopeat, a by-product of the coconut (<em>Cocos nucifera </em>L.), is an important soilless media that contains high potassium (K), sodium (Na), and electrical conductivity (EC) depending on its source. M...Cocopeat, a by-product of the coconut (<em>Cocos nucifera </em>L.), is an important soilless media that contains high potassium (K), sodium (Na), and electrical conductivity (EC) depending on its source. Methods for extracting these elements and thus lowering EC are yet to be standardized. This study was therefore carried out to investigate two extraction methods of these elements in cocopeat. A greenhouse pot experiment was carried out at the Climate and Water Smart Agriculture Centre of Egerton University, Kenya. It was laid out in a 5 × 4 factorial completely randomized design. Five soaking durations (12, 24, 36, 48, and 72 hours) and four calcium nitrate (Ca(NO<sub>3</sub>)<sub>2</sub>) levels (0, 60, 100, and 150 g) were used. The experiment was done in two folds: the leachate and treated cocopeat examination for their chemical properties. The General Linear Model procedures were used for Analysis of Variance at (P ≤ 0.05). The results showed that the addition of Ca(NO<sub>3</sub>)<sub>2</sub> 100 g extracted significantly more K and Na in the leachate than Ca(NO<sub>3</sub>)<sub>2</sub> 0.0 g and 60 g. The EC levels in the leachate increased with the application levels of Ca(NO<sub>3</sub>)<sub>2</sub> while the pH levels were reducing. In the treated cocopeat, Ca(NO<sub>3</sub>)<sub>2</sub> 100 g and soaking duration 36 hours significantly reduced K and Na and sufficiently supplemented Ca and N. Irrespective of Ca(NO<sub>3</sub>)<sub>2</sub> and soaking durations, after the cocopeat is washed, the EC and pH values fall within their suitable ranges. There was a strong negative correlation between Ca and Na, Ca and K, and between Na and EC. Also, strong positive correlation between Ca and N and Ca and EC. Effective supplementation of Ca and N, and optimal reduction of K and Na by 78.44% and 92%, respectively can be achieved with 100 g of Ca(NO<sub>3</sub>)<sub>2</sub> 1.5 kg<sup>-1</sup> of cocopeat in 15 liters of water with a soaking duration of 36 hours.展开更多
Nitrate-induced Ca^(2+) signaling is crucial for the primary nitrate response in plants.However,the molecular mechanism underlying the generation of the nitrate-specific calcium signature remains unknown.We report her...Nitrate-induced Ca^(2+) signaling is crucial for the primary nitrate response in plants.However,the molecular mechanism underlying the generation of the nitrate-specific calcium signature remains unknown.We report here that a cyclic nucleotide-gated channel(CNGC)protein,CNGC15,and the nitrate transceptor(NRT1.1)constitute a molecular switch that controls calcium influx depending on nitrate levels.The expression of CNGC15 is induced by nitrate,and its protein is localized at the plasma membrane after establishment of young seedlings.We found that disruption of CNGC15 results in the loss of the nitrate-induced Ca^(2+) signature(primary nitrate response)and retards root growth,reminiscent of the phenotype observed in the nrt1.1 mutant.We further showed that CNGC15 is an active Ca^(2+)-permeable channel that physically interacts with the NRT1.1 protein in the plasma membrane.Importantly,we discovered that CNGC15-NRT1.1 interaction silences the channel activity of the heterocomplex,which dissociates upon a rise in nitrate levels,leading to reactivation of the CNGC15 channel.The dynamic interactions between CNGC15 and NRT1.1 therefore control the channel activity and Ca^(2+) influx in a nitrate-dependent manner.Our study reveals a new nutrient-sensing mechanism that utilizes a nutrient transceptor-channel complex assembly to couple nutrient status to a specific Ca^(2+) signature.展开更多
Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under ano...Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under anoxic conditions： nothing added （control）, Al2（SO4）3 added, FeCl3 added, CaCl2 added, and NaNO3 added. To identify changes in the P binding sites in the sediment caused by the treatments, different P binding forms were extracted from the sediment before and after the treatments. We found that the mean P release rates for anoxic treatments with Al2（SO4）3, FeCl3, CaCl2 and NaNO3 were -0.6, 0.03, 0.6 and 2.6 mg/（m^2·d）, respectively, while the P release rate with no additives was 7.3 mg/（m^2·d）. In suboxic conditions, the concentration of total phosphorus （TP ge 657 mg/kg） in sediment was much lower than that of untreated sediment （TPaverage 688 mg/kg） and treatments with salts （TP（Al2（SO4）3） 793 mg/kg, TP（FeCl3） 781 mg/kg, TP（NaNO3） 802 mg/kg, TP（CaCl2） 747 mg/kg）. We also found that adding CaCl2 prevented P release because of apatite formation and because PCa （Ca bound P） increased at the sediment surface. Addition of Fe^3＋ and NO3^- to the sediment increased the amounts of PFe. Mn （Redox-sensitive P, mostly Fe and Mn compounds）, since iron oxide has the ability to combine P. Addition of Al2（SO4）3 increased the fraction of PAl, Fe （P bound to metal oxides （Al, Fe）） and decreased the P and Fe in the water above the anoxic sediment, showing the greater ability orAl in binding P. The results showed that Al2（SO4）3, FeCl3, CaCl2 and NaNO3 all had an effect in controlling phosphorus release. The effect was related to the forms of phosphorus existing in the sediment before treatment and the forms resulting after adding the four reagents. The combination of Al^3＋ or Fe^3＋ with NO3^- promises to be a reasonable chemical treatment for increasing the P retention capacity of sediments in eutrophic lakes. If chemical treatment is combined with bioremediation, the aim of environmental repair may be achieved.展开更多
Bioactive calcium silicates prepared by sol–gel routes mainly use calcium nitrate as the calcium precursor. However, the toxic nitrate ions are usually removed by calcination（i.e. 550 8C or over）, which poses great...Bioactive calcium silicates prepared by sol–gel routes mainly use calcium nitrate as the calcium precursor. However, the toxic nitrate ions are usually removed by calcination（i.e. 550 8C or over）, which poses great challenge for the in situ preparation of inorganic/polymer composites, as polymer moieties could not survive such temperatures. In this study, we prepared 70Si30Ca（70 mol% Si O_2 and 30 mol%Ca O） bioactive glass at low temperatures where polymer could survive（i.e. 200 8C and 350 8C）, and proposed to remove the residual nitrate ions through soaking. Deionized water and simulated body fluid（SBF） were employed as the soaking medium. The results showed that the residual nitrate ions could be removed as quickly as 0.5 h while maintain the bioactivity of the samples. This technique may open the possibility of preparing sol–gel derived bioactive glass/polymer hybrids in situ with reduced potential toxicity.展开更多
New steroid dimer,ethylene bridged bis-carbamate(3) was synthesized from cholic acid in few steps. Complexes of 3 with lanthanum(Ⅲ) and calcium(Ⅱ) nitrates were prepared in reaction of 3 and appropriate metal salts....New steroid dimer,ethylene bridged bis-carbamate(3) was synthesized from cholic acid in few steps. Complexes of 3 with lanthanum(Ⅲ) and calcium(Ⅱ) nitrates were prepared in reaction of 3 and appropriate metal salts. They were characterized by spectral data(Infrared(IR) ,ultraviolet-visible(UV/Vis) ,nuclear magnetic resonance(NMR) spectroscopy and fast-atom bombardment(FAB) ,electrospray(ESI) and matrix-assisted laser desorption/ionization mass spectrometry(MALDI-MS)) and elemental analysis. The similarity in complexing behavior of steroidal dimer toward calcium and lanthanum ions was observed.展开更多
文摘This study investigated the change in denitrification rate in muddy tidal flats sediment by chemical and biological remediation. Column experiments were conducted to determine the dependence of denitrification rate on the redox potential. Filtered seawater was fed continuously to the pipe filled with sediment from the muddy tidal flats. An increase in the redox potential from -198 mV to 21 mV with bioturbation led to increases in the denitrification rate from 24.2 mg/m2/day to 29.8 mg/m2/day. The increase in denitrification was explained by the acceleration of mass transfer in the sediment. Redox-potential increased from -400 mV to -200 mV by the addition of 10 g calcium nitrate, acid volatile sulfide was below the detection limit to 20 cm depth, and denitrification rate was increased from 21.3 mg/m2/day to 36.4 mg/m2/day. It is considered that the increased nitrogen concentration led to an increase in microbial activity.
文摘Cocopeat, a by-product of the coconut (<em>Cocos nucifera </em>L.), is an important soilless media that contains high potassium (K), sodium (Na), and electrical conductivity (EC) depending on its source. Methods for extracting these elements and thus lowering EC are yet to be standardized. This study was therefore carried out to investigate two extraction methods of these elements in cocopeat. A greenhouse pot experiment was carried out at the Climate and Water Smart Agriculture Centre of Egerton University, Kenya. It was laid out in a 5 × 4 factorial completely randomized design. Five soaking durations (12, 24, 36, 48, and 72 hours) and four calcium nitrate (Ca(NO<sub>3</sub>)<sub>2</sub>) levels (0, 60, 100, and 150 g) were used. The experiment was done in two folds: the leachate and treated cocopeat examination for their chemical properties. The General Linear Model procedures were used for Analysis of Variance at (P ≤ 0.05). The results showed that the addition of Ca(NO<sub>3</sub>)<sub>2</sub> 100 g extracted significantly more K and Na in the leachate than Ca(NO<sub>3</sub>)<sub>2</sub> 0.0 g and 60 g. The EC levels in the leachate increased with the application levels of Ca(NO<sub>3</sub>)<sub>2</sub> while the pH levels were reducing. In the treated cocopeat, Ca(NO<sub>3</sub>)<sub>2</sub> 100 g and soaking duration 36 hours significantly reduced K and Na and sufficiently supplemented Ca and N. Irrespective of Ca(NO<sub>3</sub>)<sub>2</sub> and soaking durations, after the cocopeat is washed, the EC and pH values fall within their suitable ranges. There was a strong negative correlation between Ca and Na, Ca and K, and between Na and EC. Also, strong positive correlation between Ca and N and Ca and EC. Effective supplementation of Ca and N, and optimal reduction of K and Na by 78.44% and 92%, respectively can be achieved with 100 g of Ca(NO<sub>3</sub>)<sub>2</sub> 1.5 kg<sup>-1</sup> of cocopeat in 15 liters of water with a soaking duration of 36 hours.
基金supported by grants from the Key Program of the National Natural Science Foundation of China(31930010 to L.L.)the General Program of National Natural Science Foundation of China(no.31872170 to L.L.and no.31900234 to C.H.)+2 种基金the National Key Research and Development Program of China(YFD0300102-3 to L.L.)the Capacity Building for Sci-Tech Innovation-Fundamental Scientific Research Funds(19530050165 to L.L.).supported,in part,by a grant from the National Science Foundation(MCB-1714795 to S.L.).
文摘Nitrate-induced Ca^(2+) signaling is crucial for the primary nitrate response in plants.However,the molecular mechanism underlying the generation of the nitrate-specific calcium signature remains unknown.We report here that a cyclic nucleotide-gated channel(CNGC)protein,CNGC15,and the nitrate transceptor(NRT1.1)constitute a molecular switch that controls calcium influx depending on nitrate levels.The expression of CNGC15 is induced by nitrate,and its protein is localized at the plasma membrane after establishment of young seedlings.We found that disruption of CNGC15 results in the loss of the nitrate-induced Ca^(2+) signature(primary nitrate response)and retards root growth,reminiscent of the phenotype observed in the nrt1.1 mutant.We further showed that CNGC15 is an active Ca^(2+)-permeable channel that physically interacts with the NRT1.1 protein in the plasma membrane.Importantly,we discovered that CNGC15-NRT1.1 interaction silences the channel activity of the heterocomplex,which dissociates upon a rise in nitrate levels,leading to reactivation of the CNGC15 channel.The dynamic interactions between CNGC15 and NRT1.1 therefore control the channel activity and Ca^(2+) influx in a nitrate-dependent manner.Our study reveals a new nutrient-sensing mechanism that utilizes a nutrient transceptor-channel complex assembly to couple nutrient status to a specific Ca^(2+) signature.
文摘Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under anoxic conditions： nothing added （control）, Al2（SO4）3 added, FeCl3 added, CaCl2 added, and NaNO3 added. To identify changes in the P binding sites in the sediment caused by the treatments, different P binding forms were extracted from the sediment before and after the treatments. We found that the mean P release rates for anoxic treatments with Al2（SO4）3, FeCl3, CaCl2 and NaNO3 were -0.6, 0.03, 0.6 and 2.6 mg/（m^2·d）, respectively, while the P release rate with no additives was 7.3 mg/（m^2·d）. In suboxic conditions, the concentration of total phosphorus （TP ge 657 mg/kg） in sediment was much lower than that of untreated sediment （TPaverage 688 mg/kg） and treatments with salts （TP（Al2（SO4）3） 793 mg/kg, TP（FeCl3） 781 mg/kg, TP（NaNO3） 802 mg/kg, TP（CaCl2） 747 mg/kg）. We also found that adding CaCl2 prevented P release because of apatite formation and because PCa （Ca bound P） increased at the sediment surface. Addition of Fe^3＋ and NO3^- to the sediment increased the amounts of PFe. Mn （Redox-sensitive P, mostly Fe and Mn compounds）, since iron oxide has the ability to combine P. Addition of Al2（SO4）3 increased the fraction of PAl, Fe （P bound to metal oxides （Al, Fe）） and decreased the P and Fe in the water above the anoxic sediment, showing the greater ability orAl in binding P. The results showed that Al2（SO4）3, FeCl3, CaCl2 and NaNO3 all had an effect in controlling phosphorus release. The effect was related to the forms of phosphorus existing in the sediment before treatment and the forms resulting after adding the four reagents. The combination of Al^3＋ or Fe^3＋ with NO3^- promises to be a reasonable chemical treatment for increasing the P retention capacity of sediments in eutrophic lakes. If chemical treatment is combined with bioremediation, the aim of environmental repair may be achieved.
基金supported by NSFC (Nos. 81470101, 51173193)Royal Society/Natural Science Foundation of China international exchange (No. 51411130151)
文摘Bioactive calcium silicates prepared by sol–gel routes mainly use calcium nitrate as the calcium precursor. However, the toxic nitrate ions are usually removed by calcination（i.e. 550 8C or over）, which poses great challenge for the in situ preparation of inorganic/polymer composites, as polymer moieties could not survive such temperatures. In this study, we prepared 70Si30Ca（70 mol% Si O_2 and 30 mol%Ca O） bioactive glass at low temperatures where polymer could survive（i.e. 200 8C and 350 8C）, and proposed to remove the residual nitrate ions through soaking. Deionized water and simulated body fluid（SBF） were employed as the soaking medium. The results showed that the residual nitrate ions could be removed as quickly as 0.5 h while maintain the bioactivity of the samples. This technique may open the possibility of preparing sol–gel derived bioactive glass/polymer hybrids in situ with reduced potential toxicity.
基金Project supported by the Polish Ministry of Science and Higher Education (NN204 166 836)
文摘New steroid dimer,ethylene bridged bis-carbamate(3) was synthesized from cholic acid in few steps. Complexes of 3 with lanthanum(Ⅲ) and calcium(Ⅱ) nitrates were prepared in reaction of 3 and appropriate metal salts. They were characterized by spectral data(Infrared(IR) ,ultraviolet-visible(UV/Vis) ,nuclear magnetic resonance(NMR) spectroscopy and fast-atom bombardment(FAB) ,electrospray(ESI) and matrix-assisted laser desorption/ionization mass spectrometry(MALDI-MS)) and elemental analysis. The similarity in complexing behavior of steroidal dimer toward calcium and lanthanum ions was observed.
