With variation of drainage basin environments, desorption of soluble matter has become one of the significant erosion processes in rivers. It has a considerable impact on flow and sediment transport, as well as proces...With variation of drainage basin environments, desorption of soluble matter has become one of the significant erosion processes in rivers. It has a considerable impact on flow and sediment transport, as well as processes of river bed deformation and landform evolution throughout a watershed. In this study, considering influences on sediment movement, especially on cohesive sediment transport, Ca^2＋ and H^＋ were chosen as characteristic ions of soluble matter, and the total desorption quantity of Ca^2＋ and pH value when the desorption equilibrium is reached were employed as two indexes representing the desorption of soluble matter. By means of an indoor experiment, desorption of soluble matter as influenced by cations in static water was investigated. The results show that the total desorption quantity of soluble matter increases with the initial cation concentration until a maximum desorption quantity value is obtained and maintained. The total desorption quantity of soluble matter depends on properties of the specific cations in static water, and the stronger the affinity is between the cation and sediment surface, the higher the total desorption quantity will be. Finally, a strong approximate linear relationship between desorption quantities for different kinds of soluble matters was obtained, which means that variation of pH values can accurately reflect the desorption results of soluble matter.展开更多
Atmospheric fine particulate matters (PM2.5) were collected with an Envirotech Instrument (Model APM 550) at the roof of Khundkur Mukarram Hussain Science Building, University of Dhaka, Bangladesh between January and ...Atmospheric fine particulate matters (PM2.5) were collected with an Envirotech Instrument (Model APM 550) at the roof of Khundkur Mukarram Hussain Science Building, University of Dhaka, Bangladesh between January and February, 2013. PM2.5 samples were collected on Quartz fiber filters during day and night time. Water soluble ions (sulfate, nitrate, phosphate, chloride, bromide, sodium, potassium and calcium) were analyzed with Ion Chromatography (Model 881, Metrohm Ltd., Switzerland) and Flame photometer (Model PFP7, Jenway, UK). Average PM2.5 mass was 136.1 μg·mDž during day time and 246.8 μg·mDž during night time with a total average of 191.4 μg·mDž. Nighttime PM2.5 concentration was about double compared than that of daytime presumable due to the low ambient temperatures with high emissions from heavy duty vehicles. The 24-hour average PM2.5 mass (average of day and night) was about eight times higher than WHO (25.0 μg·mDž) and about three times higher than DoE, Bangladesh (65.0 μg·mDž) limit values. The total average concentrations of sulfate, nitrate, phosphate, bromide, chloride, sodium, potassium and calcium were 5.30, 7.75, 0.62, 0.16, 1.19, 1.30, 8.11, and 3.09 μg·mDž, respectively. The concentrations of the water soluble ions were much higher during nighttime than daytime except nitrate, bromide and potassium. Excellent correlations were observed between sulfate and nitrate, sodium and chloride, bromide and phosphate indicating joint sources of origin. Potassium, sulfate, nitrate and calcium are the most dominant species in PM2.5. Water soluble ionic components in Dhaka contributed about 15% mass of the PM2.5. Ratio analysis showed that sodium and chloride were from mainly sea salt. Potassium has varieties of sources other than biomass burning. Sulfate and nitrate are mainly from fossil fuel origin. This is the first study of the day and night variation of the water soluble ionic species at the fine particulate matters (PM2.5) in Bangladesh.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51209014)the Fundamental Research Funds for the Changjiang River Scientific Research Institute(Grant No.CKSF2013012/TB)
文摘With variation of drainage basin environments, desorption of soluble matter has become one of the significant erosion processes in rivers. It has a considerable impact on flow and sediment transport, as well as processes of river bed deformation and landform evolution throughout a watershed. In this study, considering influences on sediment movement, especially on cohesive sediment transport, Ca^2＋ and H^＋ were chosen as characteristic ions of soluble matter, and the total desorption quantity of Ca^2＋ and pH value when the desorption equilibrium is reached were employed as two indexes representing the desorption of soluble matter. By means of an indoor experiment, desorption of soluble matter as influenced by cations in static water was investigated. The results show that the total desorption quantity of soluble matter increases with the initial cation concentration until a maximum desorption quantity value is obtained and maintained. The total desorption quantity of soluble matter depends on properties of the specific cations in static water, and the stronger the affinity is between the cation and sediment surface, the higher the total desorption quantity will be. Finally, a strong approximate linear relationship between desorption quantities for different kinds of soluble matters was obtained, which means that variation of pH values can accurately reflect the desorption results of soluble matter.
文摘Atmospheric fine particulate matters (PM2.5) were collected with an Envirotech Instrument (Model APM 550) at the roof of Khundkur Mukarram Hussain Science Building, University of Dhaka, Bangladesh between January and February, 2013. PM2.5 samples were collected on Quartz fiber filters during day and night time. Water soluble ions (sulfate, nitrate, phosphate, chloride, bromide, sodium, potassium and calcium) were analyzed with Ion Chromatography (Model 881, Metrohm Ltd., Switzerland) and Flame photometer (Model PFP7, Jenway, UK). Average PM2.5 mass was 136.1 μg·mDž during day time and 246.8 μg·mDž during night time with a total average of 191.4 μg·mDž. Nighttime PM2.5 concentration was about double compared than that of daytime presumable due to the low ambient temperatures with high emissions from heavy duty vehicles. The 24-hour average PM2.5 mass (average of day and night) was about eight times higher than WHO (25.0 μg·mDž) and about three times higher than DoE, Bangladesh (65.0 μg·mDž) limit values. The total average concentrations of sulfate, nitrate, phosphate, bromide, chloride, sodium, potassium and calcium were 5.30, 7.75, 0.62, 0.16, 1.19, 1.30, 8.11, and 3.09 μg·mDž, respectively. The concentrations of the water soluble ions were much higher during nighttime than daytime except nitrate, bromide and potassium. Excellent correlations were observed between sulfate and nitrate, sodium and chloride, bromide and phosphate indicating joint sources of origin. Potassium, sulfate, nitrate and calcium are the most dominant species in PM2.5. Water soluble ionic components in Dhaka contributed about 15% mass of the PM2.5. Ratio analysis showed that sodium and chloride were from mainly sea salt. Potassium has varieties of sources other than biomass burning. Sulfate and nitrate are mainly from fossil fuel origin. This is the first study of the day and night variation of the water soluble ionic species at the fine particulate matters (PM2.5) in Bangladesh.
