Dissolved organic matter （DOM） from freshwater, mid-salinity, and seawater endmember samples in the Jiulong River Estuary, China were fractionated using cross-flow ultrafiltration with a 10-kDa membrane. The colloid...Dissolved organic matter （DOM） from freshwater, mid-salinity, and seawater endmember samples in the Jiulong River Estuary, China were fractionated using cross-flow ultrafiltration with a 10-kDa membrane. The colloidal organic matter （COM; 10 kDa-0.22 pm） retentate, low molecular weight （LMW） DOM （〈10 kDa） permeate, and bulk samples were analyzed using absorption spectroscopy and three-dimensional fluorescence excitation-emission-matrix spectroscopy. The UV-visible spectra of COM were very similar to those obtained for permeate and bulk samples, decreasing monotonically with increasing wavelength. Most of the chromophoric DOM （CDOM, expressed as the absorption coefficient a355） occurred in the LMW fraction, while the percentage of CDOM in the colloidal fraction was substantially higher in the freshwater endmembet （13.4% of the total） than in the seawater endmember （6.8%）. The bulk CDOM showed a conservative mixing behavior in the estuary, while there was removal of the COM fraction and a concurrent addition of the permeate fraction in the mid-salinity sample, implying that part of the colloidal CDOM was transformed into LMW CDOM. Two humic-like components （CI： 〈250, 325/402 nm; and C2： 265, 360/458 nm） and one protein-like component （C3：275/334 nm） were identified using parallel factor analysis. The contributions of the C1, C2, and C3 components of the COM fraction to the bulk sample were 2.5%-8.7%, 4.8%-12.6%, and 7.4%-14.7%, respectively, revealing that fluorescent DOM occurred mainly in the LMW fraction in the Jiulong River Estuary. The C1 and C2 components in the retentate and permeate samples showed conservative mixing behavior, but the intensity ratio of C2/C1 was higher in the retentate than in the permeate fractions for all salinity samples, showing that the humic component was more enriched in the COM than the fulvic component. The intensity ratio of C3/（C 1 ＋C2） was much higher in the retentate than in the permeate fraction for mid-salinity and seawater samples, revealing that the protein-like component was relatively more enriched in COM than the humic-like component. The contribution of the protein-like component （C3） to the total fluorescence in the retentate increased from 14% in the freshwater endmember to 72% for the seawater endmember samples, clearly indicating the variation of dominance by the humic-like component compared to the protein-like component during the estuarine mixing process of COM.展开更多
The variation of colloidal phosphorus with salinity in estuary was studied in this paper, which was compared with those of particle and truly dissolved phosphorus with the purpose of finding out the similarities and d...The variation of colloidal phosphorus with salinity in estuary was studied in this paper, which was compared with those of particle and truly dissolved phosphorus with the purpose of finding out the similarities and differences between their behaviors in the estuary. Distribution patterns of phosphorus in particle, colloidal and truly dissolved phase at different salinities and their relationships with suspended particulate matter were also studied to understand the transformation and transporta- tion of colloidal phosphorus in estuarine area. The result showed that the concentrations of total colloidal phosphorus, organic colloidal phosphorus and inorganic colloidall phosphate all descended from river-end to sea-end, illustrating their terrigenous source. Rat.ios of organic to total colloidal phosphorus decreased with salinity＇s increment, indicating that organic phosphorus was influenced by scavenging process of colloid more significantly as compared with inorganic phosphate. Both of the phosphorus variation tendencies and the proportion between organic and inorganic phosphorus in colloidal phase was similar with that in truly dissolved phase while different from that in particle phase.展开更多
Photosynthetic rates (PR ) of four species of marine single- celled algae were determined by means of 14C-tracer method under the experimental modelling conditions. The effects of environmental factors, such as light,...Photosynthetic rates (PR ) of four species of marine single- celled algae were determined by means of 14C-tracer method under the experimental modelling conditions. The effects of environmental factors, such as light, temperature and nutrients, on the biochemical compositions of the algae were studied. The results indicate that the suitable light intensities for the growth of Phaeodactylum tricorntum, Dunaliella spp, Skeletonema costatum and Isochrysis galbana are in the range from 5. 8 X 103 to 15 x 103 lx, showing an increasing trend of photosynthetic rates with the heightened light intensities. The irradiance response of Dunaliella spp. and Isochrysis galbana is significant. The contents of carbohydrate increase, but those of protein decrease, and the contents of lipids change very little. The optimum temperatures for the growth of the four species of algae are 14, 26, 21 and 26t respectively, characterized by the maxima of PR and the contents of carbohydrate, protein and lipid as well as their variations. The apparent activation energies in the photosynthesis process of Phaeodactylum tricornutum, Dunaliella spp., Skeletonema costatum and Isochrysis galbana are 23. 2, 38. 5, 22. 4 and 61. 7 kJ/mol respectively, and the temperature coefficients for the four algae are 1. 74, 1. 74, 1. 38 and 1. 69 respectively. The peaks of PR appeared in some culture media (N/P = 16 ) of Phaeodactylum tricornutum and Skeletonema costatum, and in other media (N/P = 28) of Dunaliella spp. and Isochurysis galbana. The contents and their variations of carbohydrate, protein and lipid of the four species of algae are all maximum when N/P is equal to 16 in culture media.展开更多
基金The National Natural Science Foundation of China under contract No.41276064the Chinese Scholarship Council Program and the Program for New Century Excellent Talents(NCET)to Weidong Guothe Fundamental Research Funds for the Central Universities under contract No.201112G011
文摘Dissolved organic matter （DOM） from freshwater, mid-salinity, and seawater endmember samples in the Jiulong River Estuary, China were fractionated using cross-flow ultrafiltration with a 10-kDa membrane. The colloidal organic matter （COM; 10 kDa-0.22 pm） retentate, low molecular weight （LMW） DOM （〈10 kDa） permeate, and bulk samples were analyzed using absorption spectroscopy and three-dimensional fluorescence excitation-emission-matrix spectroscopy. The UV-visible spectra of COM were very similar to those obtained for permeate and bulk samples, decreasing monotonically with increasing wavelength. Most of the chromophoric DOM （CDOM, expressed as the absorption coefficient a355） occurred in the LMW fraction, while the percentage of CDOM in the colloidal fraction was substantially higher in the freshwater endmembet （13.4% of the total） than in the seawater endmember （6.8%）. The bulk CDOM showed a conservative mixing behavior in the estuary, while there was removal of the COM fraction and a concurrent addition of the permeate fraction in the mid-salinity sample, implying that part of the colloidal CDOM was transformed into LMW CDOM. Two humic-like components （CI： 〈250, 325/402 nm; and C2： 265, 360/458 nm） and one protein-like component （C3：275/334 nm） were identified using parallel factor analysis. The contributions of the C1, C2, and C3 components of the COM fraction to the bulk sample were 2.5%-8.7%, 4.8%-12.6%, and 7.4%-14.7%, respectively, revealing that fluorescent DOM occurred mainly in the LMW fraction in the Jiulong River Estuary. The C1 and C2 components in the retentate and permeate samples showed conservative mixing behavior, but the intensity ratio of C2/C1 was higher in the retentate than in the permeate fractions for all salinity samples, showing that the humic component was more enriched in the COM than the fulvic component. The intensity ratio of C3/（C 1 ＋C2） was much higher in the retentate than in the permeate fraction for mid-salinity and seawater samples, revealing that the protein-like component was relatively more enriched in COM than the humic-like component. The contribution of the protein-like component （C3） to the total fluorescence in the retentate increased from 14% in the freshwater endmember to 72% for the seawater endmember samples, clearly indicating the variation of dominance by the humic-like component compared to the protein-like component during the estuarine mixing process of COM.
基金The Education Department of China for the plan of chief teachers in universitiesthe National Natural Science Foundation of China for the key plan under contract No. 90411016
文摘The variation of colloidal phosphorus with salinity in estuary was studied in this paper, which was compared with those of particle and truly dissolved phosphorus with the purpose of finding out the similarities and differences between their behaviors in the estuary. Distribution patterns of phosphorus in particle, colloidal and truly dissolved phase at different salinities and their relationships with suspended particulate matter were also studied to understand the transformation and transporta- tion of colloidal phosphorus in estuarine area. The result showed that the concentrations of total colloidal phosphorus, organic colloidal phosphorus and inorganic colloidall phosphate all descended from river-end to sea-end, illustrating their terrigenous source. Rat.ios of organic to total colloidal phosphorus decreased with salinity＇s increment, indicating that organic phosphorus was influenced by scavenging process of colloid more significantly as compared with inorganic phosphate. Both of the phosphorus variation tendencies and the proportion between organic and inorganic phosphorus in colloidal phase was similar with that in truly dissolved phase while different from that in particle phase.
基金the Natural Science Foundation of Fujian Province under contract! No. D92001.
文摘Photosynthetic rates (PR ) of four species of marine single- celled algae were determined by means of 14C-tracer method under the experimental modelling conditions. The effects of environmental factors, such as light, temperature and nutrients, on the biochemical compositions of the algae were studied. The results indicate that the suitable light intensities for the growth of Phaeodactylum tricorntum, Dunaliella spp, Skeletonema costatum and Isochrysis galbana are in the range from 5. 8 X 103 to 15 x 103 lx, showing an increasing trend of photosynthetic rates with the heightened light intensities. The irradiance response of Dunaliella spp. and Isochrysis galbana is significant. The contents of carbohydrate increase, but those of protein decrease, and the contents of lipids change very little. The optimum temperatures for the growth of the four species of algae are 14, 26, 21 and 26t respectively, characterized by the maxima of PR and the contents of carbohydrate, protein and lipid as well as their variations. The apparent activation energies in the photosynthesis process of Phaeodactylum tricornutum, Dunaliella spp., Skeletonema costatum and Isochrysis galbana are 23. 2, 38. 5, 22. 4 and 61. 7 kJ/mol respectively, and the temperature coefficients for the four algae are 1. 74, 1. 74, 1. 38 and 1. 69 respectively. The peaks of PR appeared in some culture media (N/P = 16 ) of Phaeodactylum tricornutum and Skeletonema costatum, and in other media (N/P = 28) of Dunaliella spp. and Isochurysis galbana. The contents and their variations of carbohydrate, protein and lipid of the four species of algae are all maximum when N/P is equal to 16 in culture media.
