Effect of rising atmospheric CO2 on sediment and water 15N interactions in experimental riparian wetland

The experiment was conducted to ascertain net production and consumption rates of ¹⁵NH₄ ⁺ and ¹⁵NO₃ ^? for water and sediment in a wetland. This was done using ¹⁵N isotope pool dilution methodology under ambient and elevated atmospheric CO₂ concentrations in experimental riparian wetlands to obtain the gross N transformation rates. The ¹⁵N budget for sediment was also estimated. The results suggested that the differences in high proportion of ¹⁵N concentration in the overlying water body under elevated CO₂ could be attributed to the low production and high consumption rates of ¹⁵NH₄ ⁺ in sediment. The elevated CO₂ effect on production and consumption of NH₄ ⁺ decreased by 144 % (P = 0.014) and increased by 153 % (P = 0.009), respectively. Thereby, ¹⁵NH₄ ⁺ production rates are negatively related with ¹⁵NO₃ ^? consumption rates and this accounted for the decreases in net ¹⁵NO₃ ^? consumption under CO₂ enrichment in the wetland sediment by 11 % (P = 0.528). Therefore, ¹⁵NO₃ ^? production and consumption rates may strongly depend on NH₄ ⁺ production. Inorganic ¹⁵N and total ¹⁵N exported from sediment to overlying water body by the effect of CO₂ were 41 % (P = 0.071) and 18 % (P = 0.000), respectively. Therefore, low net ¹⁵NH₄ ⁺ production and high ¹⁵NH₄ ⁺ consumption rates under elevated CO₂ may partly explain the significant reduction of N from the sediment.     

Complex relationships between salt type and rock properties in a durability experiment of multiple salt–rock treatments

A laboratory salt weathering experiment was performed using five salts to attack eight types of rocks to determine the relative significance of rock durability and salt aggressivity to salt crystallization damage. The influence of individual rock properties on the salt susceptibility of the rocks was also evaluated. To study the relation between pore characteristics, salt uptake, and damage, the pre‐ and post‐experiment pore size distributions of the rocks were also examined. It is observed that both salt type and rock properties influenced the damage pattern. The durability ranking of the rocks became significantly altered with the salt type while the variation in salt efficacy ranking with rock type was less pronounced. Of the five salts used, sodium chloride and aluminium sulfate were invariably ineffective with all rock types while sodium carbonate, sodium sulfate, and magnesium sulfate, were markedly more effective in damaging most types of rock used. Of the rock properties investigated, the microporosity (of pores smaller than 0·05 or 0·1 µm) showed the most significant influence on deterioration of the rocks associated with salt crystallization, whereas microporosity of pores smaller than 5 µm played a more important role in salt uptake. Pore size distribution was thus the key factor controlling salt uptake and damage. Rocks with a large number of pores (<5 µm) and a high proportion of pores (<0·05 or 0·1 µm) were particularly susceptible to salt crystallization damage. However, anomalies arose that could not be explained in terms of rock properties or salt efficacy alone. Overall, the relative influences of salt type/efficacy and rock type/properties on salt damage propensity were not clear enough to draw a reasonable conclusion. Salt crystallization damage appears to be influenced by the individual interactions between salts and rocks, which could explain the anomalous results. Copyright © 2009 John Wiley & Sons, Ltd.     

Mobility encounter: The narratives of Burmese refugees in Norway

The article examines the lived experiences of Burmese refugees in Norway in order to understand how they experience integration into local society and how they manage their transnational lives in new socio-economic, political, and cultural contexts. The examination is performed from the perspective of mobility as the entanglement of movement, representation, and practice. In teasing out the refugees' various experiences, the author emphasizes the diversity of migrant groups in terms of their ethnicity, religion, gender, and age, as well as multiple dimensions of mobilities. The complex politics of mobility – how different mobilities are produced, practised, and regulated in relation to issues such as transnational migration, diasporic cultures, and communication technologies – is seen as underlying the narratives of Burmese refugees in Norway. Their narratives equate mobilities with escape from poverty, highlighting the linkage that mobility has with poverty and development. The discussion reveals the potential for divisiveness within wider society in Norway, and it is argued that a nuanced understanding of how mobilities are differentially accessed within immigrant groups is essential for conceiving a multicultural society in Norway.     

Observed characteristics of flow,water mass,and turbulent mixing in the Preparis Channel

Preparis Channel is the very important exchange path of energy and materials between the northern Bay of Bengal and Andaman Sea(AS). A set of hydrographic measurements, a microstructure profiler, and a deep mooring were used to determine the characteristics of water masses, turbulent mixing, and flows in the Preparis Channel. The unprecedented short-term mooring data reveal that a deep current in the deep narrow passage(below 400 m) of the Preparis Channel flows toward the Bay of Bengal(BoB) wit...     

Tidal influence on suspended sediment distribution and dispersal in the northern Andaman Sea and Gulf of Martaban

Surface and water column profiles of suspended matter collected during April-May 2002, and satellite images were used to study factors influencing suspended sediment concentrations (SSCs) and dispersal in the northern Andaman Sea and Gulf of Martaban, one of the largest highly turbid areas of the world's oceans. Perennial high SSC in the Gulf of Martaban is due to a combination of factors including resuspension of sediments by strong tidal currents, shallow bathymetry and seasonal sediment influx from rivers. From satellite images, it was observed that in the central portion of the Gulf of Martaban, the turbidity front oscillates about 150 km in phase with spring-neap tidal cycles and the area covered by the turbid zone (SSC>15 mg l⁻¹) increases from less than 15 000 km² during neap tide to more than 45 000 km² during spring tide. The sediment discharged by the Ayeyarwady River is transported mainly eastward, along the coast, into the Gulf of Martaban. Occasionally, during the winter monsoon period, sediment plumes are seen heading westward into the Bay of Bengal. Turbidity profiles show that bottom nepheloid layers are actively transporting some of the sediments into the deep Andaman Sea via the Martaban canyon.     

Comparison Between Shear Behaviors of Overconsolidated Nakdong River Sandy Silt and Silty Sand

From this research, overconsolidated undrained and drained behaviors of specimens with high sand content were highly dilatant. According to the comparison results of laboratory tests, the deviator stresses of silty sand were greater than sandy silt due to high sand content under increasing OCRs, and both silty sand and sandy silt were presented strain softening tendency after failure under undrained loading. The pore water pressure increased with increasing fines content under increasing OCRs. Silty sand exhibited more dilatancy and increasing shear strength than sandy silt because pore water pressures of silty sand were lower than sandy silt under higher OCRs. In overconsolidated drained tests, silty sand is higher strength than sandy silt because silty sand has a lower volumetric strain and higher deviator stress than sandy silt under increasing OCRs. As the degree of overconsolidation increased, similar behaviors of silty sand and sandy silt observed that volumetric strain decreased to negative values due to dilatancy effect and low-cohesion under current effective confining pressures.