Factors controlling the total alkalinity in the Arabian Sea and Red Sea

Based on data obtained during the Geochemical Ocean Section Study (GEOSECS) 1977, Mer Rouge (MEROU) 1982, and US Joint Global Ocean Flux (JGOFS) 1995 studies we have analyzed the processes controlling the total alkalinity (TA) of the whole water column in the Arabian Sea and the Red Sea. The main processes important for the TA variability in area of study are salinity variations, soft tissue production, calcium carbonate formation and dissolution, and sedimentation. For the subsurface waters different processes dominate in the different basins. Regarding spatial variations in surface TA, maximum values occur in the Red Sea and minimum in the upwelling region along the Omani coast in the Arabian Sea. These variations are mainly associated with physical processes that control salinity. Alkalinity variations were decomposed to contributions arising from salinity variations (\Delta TA^s), organic matter production/remineralisation (\Delta TA^{org}), and production/dissolution of calcium carbonate (\Delta TA^{CaCO_3}). Positive \Delta values resulted for the processes that increase TA whereas negative \Delta values resulted for the processes that decrease TA. In the upper 200 m of the water column, (\Delta TA^s) was found to be 70 \mu mol kg^{-1} and 121 \mu mol kg^{-1} for the Arabian Sea and the Red Sea, respectively. Below the 200 m depth the \Delta TA^s was 45 \mu mol kg^{-1} and 6 \mu mol kg^{-1} for the Arabian Sea and the Red Sea respectively. \Delta TA^{org} was maximum in surface (24 \mu mol kg^{-1}) for both Seas. For depths below 200 m, \Delta TA^{org} was between -10 and 0 \mu mol kg^{-1} in the Arabian Sea, and between 0 and 10 \mu mol kg^{-1} in the Red Sea. Values for \Delta TA^{CaCO_3} were around 0 \mu mol kg^{-1} in the surface in both regions, but \Delta TA^{CaCO_3} increased nearly linearly with depth in the Arabian Sea until it reached and stabilized to values around 150 \mu mol kg^{-1} at about 3000 m. The increase was due to dissolution of calcium carbonate (CaCO_3) as the Arabian Sea was found to be undersaturated with respect to aragonite and calcite around 400 and 3000 m, respectively. Conversely, the level of undersaturation was never reached in the Red Sea. Thus,sedimentation of CaCO_3 out of the water column was possible in the Red Sea. The fact that \Delta TA^{CaCO_3} decreased and stabilized to a value of -40 \mu mol kg^{-1} at about 500 m depth in the Red Sea suggested that CaCO_3 formation and sedimentation removed TA from the water column

Sea surface pCO2 variability and air-sea CO2 exchange in the coastal Sudanese Red Sea

The dynamics of sea surface pCO2 (pCO2w) and air–sea CO2 exchange of the Sudanese coastal Red Sea has for the first time been studied over a full annual cycle (October 2014–October 2015) based on semi-continuous measurements from moored autonomous sensors. pCO2w showed a seasonal amplitude of approximately 70 μatm, overlaid by a high frequency (3-4 days) signal of around 10 μatm. The highest values, of about 440 μatm occurred during summer and fall, while the lowest values of about 370 μatm occurred during winter. The monthly pCO2w change was primarily driven by temperature, i.e., heating and cooling of the water surface. Additionally, Dissolved Inorganic Carbon (DIC) and Total Alkalinity (AT) contributed significantly to the observed change in pCO2w as a consequence of along-coast advection and upwelling of CO2-rich deep water, and likely biological production, and uptake of atmospheric CO2. The area is a net annual source for atmospheric CO2 of 0.180 ± 0.009 mol CO2 m−2 y−1. Based on a compilation of historic and our new data, altogether covering the years 1977 to 2015, long term trends of pCO2w were determined for the seasons winter–spring (1.75 ± 0.72 μatm y−1) and summer -fall (180 ± 0.41 μatm y−1), both weaker than the atmospheric trend (1.96 ± 0.02 μatm y−1). We are suggesting that the study region has transformed from being a source of CO2 to the atmosphere throughout the year to becoming a sink of CO2 during parts of the year. The long term pCO2w trend was to a large degree driven by increasing DIC, but increasing AT and temperature also played a role

Sea surface pCO2 variability and air-sea CO2 exchange in the coastal Sudanese Red Sea

The dynamics of sea surface pCO2 () and air–sea CO2 exchange of the Sudanese coastal Red Sea has for the first time been studied over a full annual cycle (October 2014–October​ 2015) based on semi-continuous measurements from moored autonomous sensors. showed a seasonal amplitude of approximately 70 atm, overlaid by a high frequency (3-4 days) signal of around 10 atm. The highest values, of about 440 atm occurred during summer and fall, while the lowest values of about 370 atm occurred during winter. The monthly change was primarily driven by temperature, i.e., heating and cooling of the water surface. Additionally, Dissolved Inorganic Carbon (DIC) and Total Alkalinity (AT) contributed significantly to the observed change in as a consequence of along-coast advection and upwelling of CO2-rich deep water, and likely biological production, and uptake of atmospheric CO2. The area is a net annual source for atmospheric CO2 of 0.180 0.009 mol CO2 m−2 y−1. Based on a compilation of historic and our new data, altogether covering the years 1977 to 2015, long term trends of were determined for the seasons winter–spring (1.75 0.72 atm y−1) and summer -fall (180 0.41 atm y−1), both weaker than the atmospheric trend (1.96 0.02 atm y−1). We are suggesting that the study region has transformed from being a source of CO2 to the atmosphere throughout the year to becoming a sink of CO2 during parts of the year. The long term trend was to a large degree driven by increasing DIC, but increasing AT and temperature also played a role

Sea surface pCO2 variability and air-sea CO2 exchange in the coastal Sudanese Red Sea

The dynamics of sea surface pCO2 () and air-sea CO2 exchange of the Sudanese coastal Red Sea has for the first time been studied over a full annual cycle (October 2014 - October 2015) based on semi-continuous measurements from moored autonomous sensors. showed a seasonal amplitude of approximately 70 atm, overlaid by a high frequency (3-4 days) signal of around 10 atm. The highest values, of about 440 atm occurred during summer and fall, while the lowest values of about 370 atm occurred during winter. The monthly change was primarily driven by temperature, i.e., heating and cooling of the water surface. Additionally, Dissolved Inorganic Carbon (DIC) and Total Alkalinity (AT) contributed significantly to the observed change in as a consequence of along-coast advection and upwelling of CO2-rich deep water, and likely biological production, and uptake of atmospheric CO2. The area is a net annual source for atmospheric CO2 of 0.180 0.009 mol CO2 m−2 y−1. Based on a compilation of historic and our new data, altogether covering the years 1977 to 2015, long term trends of were determined for the seasons winter-spring (1.75 0.72 atm y−1) and summer -fall (180 0.41 atm y−1), both weaker than the atmospheric trend (1.96 0.02 atm y−1). We are suggesting that the study region has transformed from being a source of CO2 to the atmosphere throughout the year to becoming a sink of CO2 during parts of the year. The long term trend was to a large degree driven by increasing DIC, but increasing AT and temperature also played a role

Swelling Poly(ionic liquid)s: Synthesis and Application as Quasi-Homogeneous Catalysts in the Reaction of Ethylene Carbonate with Aniline

Homogeneous catalysts generally show higher catalytic activities, while heterogeneous catalysts are more easily separated from products. To combine the advantages of heterogeneous and homogeneous catalysts has been of great interest for many years. Here, we report a kind of facilely prepared cross-linked poly­(ionic liquid)­s (PILs) with swelling property to increase catalytic activities of heterogeneous catalysts. The swelling ability of PILs was greatly affected by cross-linking density and chain length of substituents on imidazolium, and the unique swelling property prompted the nonporous PILs to contact with substrates sufficiently, enhancing their catalytic activities similar to homogeneous ionic liquid monomers