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You searched for +publisher:"Universiteit Utrecht" +contributor:("Slomp, C.P."). Showing records 1 – 3 of 3 total matches.

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1. Zuijdgeest, A.L. Carbon cycling and its effect on oxygen concentrations and pH in a seasonally anoxic coastal marine system.

Degree: 2012, Universiteit Utrecht

Coastal systems are increasingly experiencing low-oxygen conditions, due to enhanced primary production from terrestrial nutrient input and increasing thermal stratification as a result of global warming. The second effect of increased atmospheric CO2 is an enhanced uptake by surface oceans, thereby lowering the pH. Organic carbon cycling is one of the key processes that links oxygen and pH in coastal systems, as oxygen is produced and protons are consumed by photosynthesis, while oxic remineralization in deeper water has the reverse effect. The question arises how extended periods of water-column hypoxia affect the pH of the system. Lake Grevelingen, in the southwestern part of the Netherlands, was used as a case study, as this lake has seasonal periods of hypoxia that vary in extent between consecutive years. On monthly cruises in 2012 water-column data were collected using CTD measurements and DOC and nutrient analyses on samples from discrete water depths. Suspended matter was filtered from water samples and analyzed for organic carbon and total nitrogen content. Field data were combined with a newly constructed 1D-reactive transport model of the carbon cycling, which used data from Rijkswaterstaat as forcing and calibration data. pH and oxygen concentration were calculated in the model as dependent variables. Measurements of pH in Lake Grevelingen show a decline over the past 30 years with ~0.005 unit per year, which coincided with ~0.07 μg L-1 yr-1 increase in chlorophyll a. The modeled gross primary production was within the range reported in the literature, but well below the preliminary estimate for 2012. Deep-water pH in the model is only dependent on oxic mineralization, which has led to lower values than those observed in the water column. In years of more extensive hypoxia, the drop in pH was larger than during the years of shorter hypoxic periods. Anaerobic processes may enhance the buffer factor of the system, thereby mitigating the respiratory decline in pH. An assessment of the buffer factor of Lake Grevelingen showed that the system is more vulnerable to changes in pH due to uptake of atmospheric CO2 than the Eastern China Sea and the Gulf of Mexico. Advisors/Committee Members: Slomp, C.P., Hagens, Mathilde.

Subjects/Keywords: Geowetenschappen; ocean acidification; hypoxia; biogeochemistry; modeling; Lake Grevelingen; oxygen; pH

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zuijdgeest, A. L. (2012). Carbon cycling and its effect on oxygen concentrations and pH in a seasonally anoxic coastal marine system. (Masters Thesis). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/252897

Chicago Manual of Style (16th Edition):

Zuijdgeest, A L. “Carbon cycling and its effect on oxygen concentrations and pH in a seasonally anoxic coastal marine system.” 2012. Masters Thesis, Universiteit Utrecht. Accessed December 02, 2020. http://dspace.library.uu.nl:8080/handle/1874/252897.

MLA Handbook (7th Edition):

Zuijdgeest, A L. “Carbon cycling and its effect on oxygen concentrations and pH in a seasonally anoxic coastal marine system.” 2012. Web. 02 Dec 2020.

Vancouver:

Zuijdgeest AL. Carbon cycling and its effect on oxygen concentrations and pH in a seasonally anoxic coastal marine system. [Internet] [Masters thesis]. Universiteit Utrecht; 2012. [cited 2020 Dec 02]. Available from: http://dspace.library.uu.nl:8080/handle/1874/252897.

Council of Science Editors:

Zuijdgeest AL. Carbon cycling and its effect on oxygen concentrations and pH in a seasonally anoxic coastal marine system. [Masters Thesis]. Universiteit Utrecht; 2012. Available from: http://dspace.library.uu.nl:8080/handle/1874/252897


Universiteit Utrecht

2. Zadelhoff, E. van. Phosphorus burial and associated sediment geochemistry in the Gulf of Finland: the role of inter-decadal redox variability.

Degree: 2014, Universiteit Utrecht

Due to the anthropogenic loading of nutrients since the beginning of the 1900’s, eutrophication related hypoxia has become a problem in the Baltic Sea. Efforts have been made to significantly reduce the anthropogenic loading but internal feedback mechanisms in the phosphorus cycle prevent a recovery to pre-industrial conditions. In recent years, several studies have been made into phosphorus cycling in the deep basins of the Baltic Sea to understand and tackle the details of this feedback mechanism. In particular, phosphorus burial in deep basin sediments has recently been better characterized. However, phosphorus burial in sediments close to the halocline has been less intensively studied. This study investigates phosphorus burial in the Gulf of Finland, a shallow and highly eutrophied subbasin of the Baltic Sea. A large area of the sediments of the Gulf of Finland underlie halocline waters, making them susceptible to variable redox conditions. We focus on the impact of inter-decadal redox changes on sedimentary chemistry during the late 20th century, which strongly influence phosphorus burial. Bulk sediment analysis, pore water and phosphorus speciation was done on three cores taken along a transect near the halocline, where oxic to seasonally hypoxic conditions prevail. Sediment age dating (210Pb) was done to couple sedimentary signals to bottom water oxygen data over the past 50 years. Furthermore, bottom water oxygen data from the Gulf of Finland were compared to the evolution of bottom water oxygen concentrations in the deep Baltic Proper. By doing so we link the dynamics of the shallow Gulf of Finland to the better studied deep basins of the Baltic Sea. Although Fe-oxide bound P in the surface sediments is high, confirming large seasonal PO42- release into the water column due to reductive dissolution of Fe-oxides, we also found high background Fe-P concentrations at these sites, which we interpret as vivianite. We found the rate of vivianite formation to be coupled to Corg¬ concentrations, and therefore peaks in Fe-P occurred during periods of increased hypoxia. Similar background Fe-P concentrations have so far only been found at permanently anoxic sites. Our findings show that, not only in the deep basins but also in shallow areas close to the halocline, Fe-P can be an important long-term burial phase for phosphorus. Hence this is significant information for Baltic Sea nutrient budget calculations and models. Advisors/Committee Members: Jilbert, T.S., Slomp, C.P..

Subjects/Keywords: Hypoxia; eutrophication; phosphorus; Baltic Sea

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zadelhoff, E. v. (2014). Phosphorus burial and associated sediment geochemistry in the Gulf of Finland: the role of inter-decadal redox variability. (Masters Thesis). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/301304

Chicago Manual of Style (16th Edition):

Zadelhoff, E van. “Phosphorus burial and associated sediment geochemistry in the Gulf of Finland: the role of inter-decadal redox variability.” 2014. Masters Thesis, Universiteit Utrecht. Accessed December 02, 2020. http://dspace.library.uu.nl:8080/handle/1874/301304.

MLA Handbook (7th Edition):

Zadelhoff, E van. “Phosphorus burial and associated sediment geochemistry in the Gulf of Finland: the role of inter-decadal redox variability.” 2014. Web. 02 Dec 2020.

Vancouver:

Zadelhoff Ev. Phosphorus burial and associated sediment geochemistry in the Gulf of Finland: the role of inter-decadal redox variability. [Internet] [Masters thesis]. Universiteit Utrecht; 2014. [cited 2020 Dec 02]. Available from: http://dspace.library.uu.nl:8080/handle/1874/301304.

Council of Science Editors:

Zadelhoff Ev. Phosphorus burial and associated sediment geochemistry in the Gulf of Finland: the role of inter-decadal redox variability. [Masters Thesis]. Universiteit Utrecht; 2014. Available from: http://dspace.library.uu.nl:8080/handle/1874/301304


Universiteit Utrecht

3. Hagens, Mathilde. Impact of biogeochemical processes on pH dynamics in marine systems.

Degree: 2015, Universiteit Utrecht

Uptake of anthropogenic carbon dioxide (CO2) from the atmosphere has resulted in a range of changes in ocean chemistry, including the lowering of pH, collectively referred to as ocean acidification. Rates of coastal-zone acidification exceed those of the open ocean since coastal-ocean pH is influenced by many other processes than absorption of CO­2 alone. These processes do not only play a role in long-term acidification but also impact pH on seasonal timescales. Examples are enhanced atmospheric sulphur and nitrogen deposition, as well as eutrophication, the latter which can additionally result in the development of low-oxygen waters. The degree to which these processes induce a change in pH depends both on their rates and the extent to which the water can buffer acid production or consumption. This acid-base buffering capacity has been shown to decrease substantially in hypoxic waters, suggesting that low-oxygen conditions exacerbate ocean acidification. In this dissertation the key factors controlling the seasonal pH variability and longer-term pH changes in both the coastal and open ocean were examined, showing that buffering mechanisms play a crucial role in the impact of any biogeochemical or physical process on pH. Monthly or seasonal water-column chemistry and process-rate measurements in a transiently hypoxic coastal marine basin indicate that, despite generally higher process rates in the surface water of the basin, the amplitude of pH variability as mainly governed by the balance between primary production and respiration is greater in the seasonally-hypoxic bottom water, due to a considerable reduction of its acid-base buffering capacity in summer. A proton budget, based on these measurements and set up for each season, shows that the net change in pH is much smaller than the flux of protons induced by each of the individual processes. The interplay between absorption of atmospheric CO2 and atmospheric sulphur and nitrogen deposition in the coastal ocean was found to depend on the water-column concentration of CO2 relative to the atmosphere. If the atmospheric concentration surpasses that of the surface water, then this part of the coastal ocean is most sensitive to CO2-induced acidification, but least affected by additional acidification resulting from atmospheric acid deposition. Although coastal seas will become up to a factor 4 more sensitive to atmospheric deposition-induced acidification between the present-day and 2100, the annual change in proton concentration will only increase by 28% at most. Finally, a set of general expressions describing the sensitivity of pH to a change in ocean chemistry was derived. These expressions, which can include as many acid-base systems as relevant and are thus generally applicable, were tested on several long-term open ocean data sets. For each of these sites, pH can be properly predicted if seasonal cycles of temperature, salinity, total alkalinity (TA) and the total concentrations of acid-base species are known. By the end of the 21st century a change in… Advisors/Committee Members: Middelburg, J.J., Slomp, C.P..

Subjects/Keywords: ocean acidification; buffering capacity; pH; carbon dioxide; biogeochemical processes; hypoxia

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hagens, M. (2015). Impact of biogeochemical processes on pH dynamics in marine systems. (Doctoral Dissertation). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/313165

Chicago Manual of Style (16th Edition):

Hagens, Mathilde. “Impact of biogeochemical processes on pH dynamics in marine systems.” 2015. Doctoral Dissertation, Universiteit Utrecht. Accessed December 02, 2020. http://dspace.library.uu.nl:8080/handle/1874/313165.

MLA Handbook (7th Edition):

Hagens, Mathilde. “Impact of biogeochemical processes on pH dynamics in marine systems.” 2015. Web. 02 Dec 2020.

Vancouver:

Hagens M. Impact of biogeochemical processes on pH dynamics in marine systems. [Internet] [Doctoral dissertation]. Universiteit Utrecht; 2015. [cited 2020 Dec 02]. Available from: http://dspace.library.uu.nl:8080/handle/1874/313165.

Council of Science Editors:

Hagens M. Impact of biogeochemical processes on pH dynamics in marine systems. [Doctoral Dissertation]. Universiteit Utrecht; 2015. Available from: http://dspace.library.uu.nl:8080/handle/1874/313165

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