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Browsing by Author "Grönroos, Jonas"

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  • Grönroos, Jonas (2022)
    Exchanges between DOM and POM play an important role in the carbon cycling of freshwater ecosystems. Flocculation is a process where aggregates of DOM are formed and moved from a liquid phase to a solid phase. For colloids to form flocs, the negative surface charge of the present organic colloids needs to be destabilized. This process is generally dependent on salinity, but other compounds affecting the ionic strength of the solution can influence these processes. Gypsum is applied to Finnish fields to reduce the amount of nutrient leaching from agricultural soils. Gypsum treatment effectively reduces the runoff of both particulate and dissolved phosphorus from agricultural fields. Gypsum treatments are performed in areas where the soil contains over 30% clay minerals, making gypsum usage highly relevant in the Archipelago Sea area. This thesis aimed to find out how gypsum additions influence flocculation processes and DOM characteristics of terrestrial organic matter in boreal rivers. The study focused on the implications of gypsum use in waterways from areas with agricultural activities. Three core experiments were conducted to investigate the effects of several variables on flocculation dynamics. This study provides some preliminary insights into the influence of gypsum on biogeochemical processes in rivers. Gypsum additions were found to influence the flocculation processes of terrestrial organic matter in boreal aquatic environments. The most notable effect of gypsum additions was the enhanced floc formation, creating an increased flux of organic material onto the sediment surface. This has potential implications for microbial and benthic food webs, meaning that gypsum use is something that may need to be considered when assessing the impact of agriculture on the biogeochemical processes of waterways. Gypsum additions were also found the influence the characteristics of the remaining DOM pool. With the current knowledge, the positive aspects of gypsum use heavily outweigh the negative ones.