The aim of this study was to investigate the importance of winter season for the production of carbon dioxide (CO2) and methane (CH4) in humic and clear-water boreal aquatic systems. The study was conducted in 16 experimental ponds in northern Sweden during the winter of 2013. Half of the ponds had a higher concentration of dissolved organic carbon (DOC). CO2, CH4, DOC and dissolved inorganic carbon (DIC) were measured repeatedly under the ice from January to April. The results show that CO2 was accumulated continually during winter. No difference in winter accumulation were found between humic and clear ponds. CH4 was rarely accumulated in neither humic nor clear ponds, and was not an important part of the gas flux at spring ice melt. At ice melt, the flux from humic ponds accounted for 1.6 g C m-2 and 1.7 g C m-2 from clear ponds, which was equivalent for 15.6% respective 100% of the annual gas emissions. On a whole-year basis humic ponds acted as a source of 10.3 g C m-2, while clear ponds acted as a sink of 14.7 g C m-2. 76 mg m-2 d-1 DOC was consumed in humic and 59 mg m-2 d-1 DOC in clear ponds while the DIC accumulation was 125 mg m-2 d-1 in humic and 118 mg m-2 d-1 in clear ponds. This study stresses the importance of ice-covered boreal aquatic systems as a significant parts of the global carbon cycling.

Per- and polyfluoroalkylated substances (PFASs) are a large group of organic chemicals that have gained an increased attention during recent years. Many of the compounds have shown to be persistent, toxic and bioaccumulating and they are found in water, soils, sediments, biota, animals and humans across the globe. The effects of PFASs to humans and animals are still being debated. It is suspected that the compounds can be carcinogenic, disrupt different hormone systems and have other severe effects. The main transport pathways of PFASs to soil are applied PFAS based firefighting foam, soil improvers and waste from industries producing PFASs or PFAS based products. Once the PFASs find their way to the soil the risk for leaching to drinking water supplies and aquatic ecosystems becomes some of the issues of great concern. In order to be able to evaluate the potential leakage of PFASs from different contaminated soils it is important to know how the PFASs interact with the soil matrix and what parameters that affects these interactions. The objective of this study was to investigate the influence of organic carbon (OC), Ca2+ ions and active carbon (AC) on the n of PFCAs and PFSAs to soil. The PFCAs examined were PFHxA, PFOA, PFNA, PFDA, PFUnDA, PFOcDA, PFHxDA and PFOcDA and the PFSAs examined were PFBS, PFHxS, PFOS and PFDS. Batch experiments were performed on soils with varying concentrations of TOC, Ca2+ and AC. The samples were spiked with PFAS native standard solution containing the 12 target PFASs. All studied parameters showed a positive influence on the sorption of PFASs to soil. The AC was found to have the highest influence on the sorption. The OC was however found to be the most important soil parameter influencing the sorption of PFASs to soil. In order to investigate the influence of aging on the sorption of PFASs, batch experiments were also conducted on soils from four different PFAS contaminated sites. The results showed that the aging positively influenced the strength of the interactions between PFASs and soil. The organic carbon normalized distribution coefficients (Koc) showed a positive correlation with the carbon chain length of the PFAS molecules and also with the substitution of a carboxylic group with a sulfonic group. The log Koc values calculated in this study decreased in the following order PFDS (log Koc3.8 0.3) > PFOS > (log Koc2.8 0.3) > PFUnDA (log Koc 3.2 0.2) > PFDA (log Koc2.7 0.1) > PFNA (log Koc2.0 0.1) > PFHxS (log Koc1.9 0.1) > PFOA (log Koc1.8 0.3) > PFHxA (log Koc1.6 0.3) > PFBS (log Koc 1.5 0.2). The log Koc values found in this study were within the range of previously reported log Kocvalues.

An investigation of shale pore structure and compositional/geochemical heterogeneities has been undertaken to elucidate the controls upon gas capacities of potential shale gas reservoirs in northeastern British Columbia, western Canada. Methane sorption isotherms, pore structure and surface area data indicate a complex interrelationship of total organic carbon (TOC) content, mineral matter and thermal maturity affect gas sorption characteristics of Devonian-€”Mississippian (D-€”M) and Jurassic strata. Methane and carbon dioxide sorption capacities of D-€”M shales increase with TOC content, due to the microporous nature of the organic matter. Clay mineral phases arealso capable of sorbing gas to their internal structure; hence D-€”M shales which are both TOC- and clay-rich have the largest micropore volumes and sorption capacities on a dry basis. Jurassic shales, which are invariably less thermally mature than D-€”M shales, do not have micropore volumes which correlate with TOC. The covariance of methane sorption capacity with TOC, independent of micropore volume, indicates a solute gas contribution (within matrix bituminite) to the total gas capacity. On a wt% TOC basis, D-M shales sorb more gas than Jurassic shales: a result of thermal-maturation induced, structural transformation of the D-€”M organic fraction. Organic-rich D-€”M strata are considered to be excellent candidates for gas shales in Western Canada. These strata have TOC contents ranging between 1-5.7 wt%, thermal maturities into the dry-gas region, and thicknesses in places of over 1000 m. Total gas capacity estimates range between 60 and 600 bcf/section where a substantial percentage of the gas capacity is free gas, due to high reservoir temperatures and pressures. Inorganic material influences modal pore size, total porosity and sorption characteristics of D-M shales. Carbonate-rich samples often have lower organic carbon contents (oxic deposition) and porosity, hence potentially lower sorbed and free-gas capacities. Highly mature Devonian shales are both silica and TOC-rich (up to 85% quartz and 5 wt% TOC) and as such, deemed excellent potential shale gas reservoirs because they are both brittle (fracable), and gas-charged. However, quartz-rich Devonian shales display tight-rock characteristics, with poorly developed fabric, small median pore diameters and low permeabilities. Hence potential `frac-zones' will require an increased density of hydraulic fracture networks for optimum gas production.

This thesis assesses the possible photochemical transformations of nitrogen fixed in organic compounds. The aim of this study was to monitor the kinetics and seasonal trends in photochemical degradation of dissolved organic matter and nitrogen in the first order stream.

In the past years considerable attention has been given to soil organic carbon (SOC) stored in permafrost-affected soils in periglacial terrain. Studies have shown that these soils store around half the global SOC pool, making them a key component of the global carbon cycle. Much of the SOC presently stored in these soils has accumulated since the Pleistocene and is protected from decomposition and erosion by low temperatures close to or below the freezing point. This makes it vulnerable to remobilization under a warming climate. This thesis provides new data on SOC storage in three study areas in Siberian periglacial terrain. A high-resolution land cover classification (LCC) for each study area is used to perform detailed vertical and spatial partitioning of SOC. The results show that the vast majority (>86%) of the ecosystem carbon is stored in the top meter of soil. Low relative storage of carbon in plant phytomass indicates limited uptake potential by vegetation and emphasises the vulnerability of the SOC pool to geomorphic changes. Peat formation as well as cryoturbation are identified as the two main pedogenic processes leading to accumulation of SOC. Presence or absence of ice-rich Yedoma deposits determine soil formation and SOC storage at landscape scale. At local scale, periglacial landforms dominate SOC allocation in the tundra, while forest ecosystem dynamics and catenary position control SOC storage in the taiga. A large diversity of soil types is found in these environments and soil properties within pedons can be highly variable with depth. High-resolution satellite imagery allows upscaling of the SOC storage at unprecedented detail, but replication of soil pedons is a limiting factor for mapping of SOC in remote periglacial regions. Future research must look beyond traditional LCC approaches and investigate additional data-sources such as digital elevation models. The concept of state factors of soil formation is advocated as a framework to investigate present day and future SOC allocation in periglacial terrain.

An investigation of shale pore structure and compositional/geochemical heterogeneities has been undertaken to elucidate the controls upon gas capacities of potential shale gas reservoirs in northeastern British Columbia, western Canada. Methane sorption isotherms, pore structure and surface area data indicate a complex interrelationship of total organic carbon (TOC) content, mineral matter and thermal maturity affect gas sorption characteristics of Devonian- Mississippian (D- M) and Jurassic strata. Methane and carbon dioxide sorption capacities of D- M shales increase with TOC content, due to the microporous nature of the organic matter. Clay mineral phases arealso capable of sorbing gas to their internal structure; hence D- M shales which are both TOC- and clay-rich have the largest micropore volumes and sorption capacities on a dry basis. Jurassic shales, which are invariably less thermally mature than D- M shales, do not have micropore volumes which correlate with TOC. The covariance of methane sorption capacity with TOC, independent of micropore volume, indicates a solute gas contribution (within matrix bituminite) to the total gas capacity. On a wt% TOC basis, D-M shales sorb more gas than Jurassic shales: a result of thermal-maturation induced, structural transformation of the D- M organic fraction. Organic-rich D- M strata are considered to be excellent candidates for gas shales in Western Canada. These strata have TOC contents ranging between 1-5.7 wt%, thermal maturities into the dry-gas region, and thicknesses in places of over 1000 m. Total gas capacity estimates range between 60 and 600 bcf/section where a substantial percentage of the gas capacity is free gas, due to high reservoir temperatures and pressures. Inorganic material influences modal pore size, total porosity and sorption characteristics of D-M shales. Carbonate-rich samples often have lower organic carbon contents (oxic deposition) and porosity, hence potentially lower sorbed and free-gas capacities. Highly mature Devonian shales are both silica and TOC-rich (up to 85% quartz and 5 wt% TOC) and as such, deemed excellent potential shale gas reservoirs because they are both brittle (fracable), and gas-charged. However, quartz-rich Devonian shales display tight-rock characteristics, with poorly developed fabric, small median pore diameters and low permeabilities. Hence potential `frac-zones' will require an increased density of hydraulic fracture networks for optimum gas production. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Dissolved Organic Carbon accounts for many different functions in the boreal forest ecosystem. It is the main vehicle for organic carbon transport from the litterfall to the forest soil profile and together with water drainage it can be transported to streams. In boreal forests, the DOC transport have gain attention because of recently documented rise in concentration. Several models have been proposed, first to gain understanding in the main cauces of this increase in concentration, and then to simulate the transport of DOC in the landscape. An exploratory work was made to identify the extent of physical control and hydrological pathways for DOC discharge and the long-term biological control over DOC production, transport in the soil profile and discharge in 2 different situations. A 22-year dataset from the Krycklan Catchment site was used. Meteorological data was used as driving variables to calibrate DOC concentration and runoff in a small catchment (Site C7). The CoupModel was set up to represent the described vegetation and documented soil characterization and then calibrated to fit the measured variables. A stepwise calibration process was preferred to promote the understanding of the different components of the landscape in the organic carbon cycle. Results point to soil heat and water transfer processes as the most relevant group to explain both water runnof and DOC discharge, with increasing relevance in the deeper layers, explaining up to 97% of short-term variability in DOC discharge for the 27-35 cm layer. Soil organic carbon pools showed to have relevance in organic carbon stock balance along the soil profile. Conclusions state that, In concordance with other authors, there is a hydrological primary control over DOC discharge, but that soil organics and especially vegetation perform a relevant role in long-term balance of the organic carbon cycle. Further studies with this model could include time-series of atmospheric deposition of Sulphur and nitrogen and running the model in cascade.

Allochthonous organic carbon is increasing and leading to browning of freshwaters in the northern hemisphere. It is already known that an increase in allochthonous dissolved organic carbon (DOC) affects benthic primary production and respiration negatively via light limitation, however, little is known about the impact on benthic bacteria. This report aims at examining how DOC and other environmental variables affect the production and growth of benthic bacteria. This was done by analyzing data from 18 lakes in northern Sweden with different DOC concentrations. This analysis was divided into two datasets: one including data at the whole lake scale and the other including data over depth within the lakes. The result showed that DOC, average depth, and the light extinction coefficient all had a negative impact on bacterial production on a whole lake scale. The light extinction coefficient was also affecting the whole lake bacterial growth efficiency (BGE) negatively. Over depth within the lakes a higher light input increased the bacterial production. In the same dataset, light was also affecting the BGE positively, while temperature had a negative effect. The results can thus be linked to the increase in allochthonous carbon and brownification. Because allochthonous DOC have a negative effect on benthic primary production, there will be less autochthonous DOC available for benthic bacteria. Allochthonous DOC is considered less degradable than autochthonous DOC. The increase in allochthonous DOC therefore has a negative impact on benthic bacterial production, likely connected to a decrease in production of autochthonous DOC by benthic algae.

To date only a limited number of studies have been done at the field level to observe the effects of agricultural management practices on carbon sequestration, water quality, and bioenergy crop yield in Mississippi. Therefore, the goals of this study were to monitor soil organic carbon (SOC) levels at the field scale and perform a comprehensive analysis of the potential environmental impacts at the watershed scale using the Soil and Water Assessment Tool (SWAT) in two watersheds located in Mississippi. It was found that SOC levels generally are affected by depth, land use, and time. The SWAT models showed good performance overall and predicted that perennial grass production in the Town Creek watershed would render the most feedstock with the least environmental impact. The results of this study were consistent with the available literature, but a longer study period is recommended.

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