Browsing by Subject "Carbon"

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  • Luoto, Tomi P.; Rantala, Marttiina V.; Kivila, E. Henriikka; Nevalainen, Liisa; Ojala, Antti E. K. (2019)
    Lakes are a dominant feature of the Arctic landscape and a focal point of regional and global biogeochemical cycling. We collected a sediment core from a High Arctic Lake in southwestern Svalbard for multiproxy paleolimnological analysis. The aim was to find linkages between the terrestrial and aquatic environments in the context of climate change to understand centennial-long Arctic biogeochemical cycling and environmental dynamics. Two significant thresholds in elemental cycling were found based on sediment physical and biogeochemical proxies that were associated with the end of the cold Little Ice Age and the recent warming. We found major shifts in diatom, chironomid and cladoceran communities and their functionality that coincided with increased summer temperatures since the 1950s. We also discovered paleoecological evidence that point toward expanded bird (Little Auk) colonies in the catchment alongside climate warming. Apparently, climate-driven increase in glacier melt water delivery as well as a prolonged snow- and ice-free period have increased the transport of mineral matter from the catchment, causing significant water turbidity and disappearance of several planktonic diatoms and clear-water chironomids. We also found sedimentary accumulation of microplastic particles following the increase in Little Auk populations suggesting that seabirds potentially act as biovectors for plastic contamination. Our study demonstrates the diverse nature of climate-driven changes in the Arctic lacustrine environment with increased inorganic input from the more exposed catchment, larger nutrient delivery from the increased bird colonies at the surrounding mountain summits and subsequent alterations in aquatic communities.
  • Mishra, Anup (Helsingin yliopisto, 2018)
    Tiivistelmä * * Abstract Biochar is a porous carbonaceous solid material produced by pyrolysis, the thermochemical conversion of biomass in anoxic conditions. Various studies suggest that biochar amendment has a postitive effect on soil pH, soil respiration, carbon/ nitrogen ratio, nitrogen mineralization, ammonifcation and nitrification. These measurements have been studied in agricultural systems but are poorly understood in boreal forests. The study was done to investigate the effects of different wood biochar application rates: 0 t ha-1, 5 t ha-1, 10 t ha-1 on soil pH, respiration and nitrogen mineralization. Replicated studies were conducted at field sites located in Juupajoki (61⁰ 48´ N, 24⁰ 18´ E), southern Finland in young pine forest stands. The measurements were taken one year after the addition of biochar. The soil respiration ( CO2 effluxes ) were measured in June and july with different biochar ( pyrolysis temperatures 500⁰ C and 650⁰ C) while N mineralization was measured in November with biochar produced at 650 C. Biochar amendment increased soil pH in plots having biochar 10 t ha-1. Nitrogen mineralization rate in the organic layer increased with the increasing amount of biochar addition but the increase was not statistically significant. The pyrolysis temperature had no significant impact on soil CO2 effluxes. The biochar also did not have any significant impact on soil CO2 effluxes. However, in June, the plots treated with 10 t ha-1 biochar produced at 650⁰ C had significantly higher CO2 effluxes than control plots. The soil respiration data showed that biochar did not have any negative effect on native soil C stocks. We conclude that biochar exhibits important charactertics that will help carbon sequestration and N cycling in boreal forests.
  • Kuittinen, Matti; Hautamaki, Ranja; Tuhkanen, Eeva-Maria; Riikonen, Anu; Ariluoma, Mari (2021)
    Purpose Currently, no clear guidance exists for ISO and EN standards of calculating, verifying, and reporting the climate impacts of plants, mulches, and soils used in landscape design and construction. In order to optimise the potential of ecosystem services in the mitigation of greenhouse gas emissions in the built environment, we unequivocally propose their inclusion when assessing sustainability. Methods We analysed the life cycle phases of plants, soils, and mulches from the viewpoint of compiling standard-based Environmental Product Declarations. In comparison to other construction products, the differences of both mass and carbon flows were identified in these products. Results Living and organic products of green infrastructure require an LCA approach of their own. Most importantly, if conventional life cycle guidance for Environmental Product Declarations were to be followed, over time, the asymmetric mass and carbon flows would lead to skewed conclusions. Moreover, the ability of plants to reproduce raises additional questions for allocating environmental impacts. Conclusions We present a set of recommendations that are required for compiling Environmental Product Declarations for the studied products of green infrastructure. In order to enable the quantification of the climate change mitigation potential of these products, it is essential that work for further development of LCA guidance be mandated.
  • Väliranta, Minna; Sannel, A. Britta K.; Juselius, Teemu (2021)
  • Ding, Yiyang; Leppälammi-Kujansuu, Jaana; Helmisaari, Heljä-Sisko (2019)
    Abstract 1. Fine root turnover plays a critical role in carbon and nutrient cycling in forest ecosystems. In this study, we focused on the most abundant deciduous species in Nordic countries, silver birch (Betula pendula Roth) and its fine root dynamics, including the amount of litter produced by fine roots as well as by aboveground vegetation. 2. The minirhizotron method was used to quantify fine root longevity of silver birch and understory fine roots and rhizomes in northern Finland. Fine root biomass per basal area and ectomycorrhizal short root numbers per mg were also quantified. The fine root litter production was estimated by fine root biomass and longevity, and then compared with the aboveground litter collected with litter traps. 3. Birch fine root biomass was 1.4-fold higher than that of understory fine roots and rhizomes (234 ± 22, 171 ± 19 g m−2 respectively). Fine root longevity of birch (372 days) was significantly (P < 0.05) shorter than that of understory vegetation (643 days). The birch fine root longevity was positively related to root diameter and soil depth. Hazard analysis showed that thicker roots, long roots, roots produced late in the growing season, and roots growing deeper in the soil had relatively lower mortality hazard compared to the reference data. The total annual soil C input, including both birch and understory, was 283 g C m−2 yr−1. The proportion of understory annual C input was 35% of the total. Total annual belowground C input was 1.4-fold greater than that of aboveground. 4. Our study indicated that the total annual belowground litter production was greater than that of the aboveground litter in a boreal deciduous forest stand. Therefore, more emphasis should be put to quantify the C cycling of both above- and belowground parts of different tree species as well as understory in boreal forests.
  • Coad, J.P.; Rubel, M.; Likonen, J.; Bekris, N.; Brezinsek, S.; Matthews, G.F.; Mayer, M.; Widdowson, A.M.; JET Contributors; Ahlgren, Tommy (2019)
    The first divertor was installed in the JET machine between 1992 and 1994 and was operated with carbon tiles and then beryllium tiles in 1994-5. Post-mortem studies after these first experiments demonstrated that most of the impurities deposited in the divertor originate in the main chamber, and that asymmetric deposition patterns generally favouring the inner divertor region result from drift in the scrape-off layer. A new monolithic divertor structure was installed in 1996 which produced heavy deposition at shadowed areas in the inner divertor corner, which is where the majority of the tritium was trapped by co-deposition during the deuterium-tritium experiment in 1997. Different divertor geometries have been tested since such as the Gas-Box and High-Delta divertors; a principle objective has been to predict plasma behaviour, transport and tritium retention in ITER. Transport modelling experiments were carried out at the end of four campaigns by puffing C-13-labelled methane, and a range of diagnostics such as quartz-microbalance and rotating collectors have been installed to add time resolution to the post-mortem analyses. The study of material migration after D-D and D-T campaigns clearly revealed important consequences of fuel retention in the presence of carbon walls. They gave a strong impulse to make a fundamental change of wall materials. In 2010 the carbon divertor and wall tiles were removed and replaced with tiles with Be or W surfaces for the ITER-Like Wall Project.
  • Heikkinen, Joonas J.; Kaarela, Tiina; Ludwig, Anastasia; Sukhanova, Tatiana; Khakipoor, Shokoufeh; Kim, Sung Il; Han, Jeon Geon; Huttunen, Henri J.; Rivera, Claudio; Lauri, Sari E.; Taira, Tomi; Jokinen, Ville; Franssila, Sami (2018)
    Carbon-based materials have attracted much attention in biological applications like interfacing electrodes with neurons and cell growth platforms due to their natural biocompatibility and tailorable material properties. Here we have fabricated sputtered carbon thin film electrodes for bioelectrical measurements. Reactive ion etching (RIE) recipes were optimized with Taguchi method to etch the close field unbalanced magnetron sputtered carbon thin film (nanocarbon, nC) consisting of nanoscale crystalline sp(2)-domains in amorphous sp(3)-bonded backbone. Plasma etching processes used gas mixtures of Ar/O-2/SF6/CHF3 for RIE and O-2/SF6 for ICP-RIE. The highest achieved etch rate for nanocarbon was >> 389 nm/min and best chromium etch mask selectivity was 135:1. Biocompatibility of the material was tested with rat neuronal cultures. Next, we fabricated multielectrode arrays (MEA) with carbon recording electrodes and metal wiring. Organotypic brain slices grown on the MEAs were viable and showed characteristic spontaneous electrical network activity. The results demonstrate that interactions with nanocarbon substrate support neuronal survival and maturation of functional neuronal networks. Thus the material can have wide applications in biomedical research.
  • Meluzova, D. S.; Babenko, P. Yu.; Shergin, A. P.; Nordlund, K.; Zinoviev, A. N. (2019)
    Particle reflection coefficients for scattering of hydrogen and deuterium atoms from amorphous beryllium, carbon and tungsten were obtained, which are of interest for thermonuclear reactor physics. For the case of deuterium scattering from tungsten the data were also calculated for polycrystalline and crystalline target. The calculations were carried out by two methods: by modeling the trajectories of the incident particles and by using the binary collision approximation. Interaction potentials between hydrogen and helium atoms and the selected materials were calculated in the scope of the density function theory using program DMol for choosing wave functions. The dependence of the reflection coefficient RN on the potential well depth was found. The results demonstrate a good agreement with the available experimental values.
  • Matkala, Laura; Kulmala, Liisa; Kolari, Pasi; Aurela, Mika; Bäck, Jaana (2021)
    We studied the occurrence of extreme weather events and their effects on the carbon dioxide and water exchange of two subarctic forest stands. One study site was a Scots pine site in eastern Finnish Lapland (VarriO), and the other was a Norway spruce site in western Finnish Lapland (Kenttarova). We compared short-term meteorological data with long-term data and found that the pine forest had experienced extremely warm, wet and dry years as well as cold spells during the growing season in the studied period of 2012-2018. The spruce forest was studied during the period 2003-2013, during which time it experienced extremely warm and wet summers, and dry periods, although the dry times were not statistically defined as such. The spruce forest was less resilient to warm and dry periods, as its total ecosystem respiration and respiration potential decreased during warm and dry summers, while the same effect was not seen in the pine forest. The decreased respiration values may have occurred due to slowed decomposition of organic matter. The pine forest experienced two cold spells during the studied period. One of these cold periods was more of a continuation of the previous cold spring and late start of the growing season in 2017, while the other one occurred after a warm period in 2014. The ecosystem respiration rates and gross primary production in 2017 remained low for the whole July-August time period likely due to cold-inhibited growth of ground vegetation, while in 2014 no such effect could be seen. We saw no effect of extreme weather events in the water exchange related measurements in either of the forests. Overall, both forests, especially the trees, were resilient to the weather extremes and experienced no long-term damage.
  • Titus, Brian K.; Brown, Kevin; Helmisaari, Heljä-Sisko; Vanguelova, Elena; Stupak, Inge; Evans, Alexander; Clarke, Nicholas; Guidi, Claudia; Bruckman, Viktor J.; Varnagiryte-Kabasinskiene, Iveta; Armolaitis, Kęstutis; de Vries, Wim; Hirai, Keizo; Kaarakka, Lilli; Hogg, Karen; Reece, Pam (2021)
    Forest biomass harvesting guidelines help ensure the ecological sustainability of forest residue harvesting for bioenergy and bioproducts, and hence contribute to social license for a growing bioeconomy. Guidelines, typically voluntary, provide a means to achieve outcomes often required by legislation, and must address needs related to local or regional context, jurisdictional compatibility with regulations, issues of temporal and spatial scale, and incorporation of appropriate scientific information. Given this complexity, comprehensive reviews of existing guidelines can aid in development of new guidelines or revision of existing ones. We reviewed 32 guidelines covering 43 jurisdictions in the USA, Canada, Europe and East Asia to expand upon information evaluated and recommendations provided in previous guideline reviews, and compiled a searchable spreadsheet of direct quotations from documents as a foundation for our review. Guidelines were considered in the context of sustainable forest management (SFM), focusing on guideline scope and objectives, environmental sustainability concerns (soils, site productivity, biodiversity, water and carbon) and social concerns (visual aesthetics, recreation, and preservation of cultural, historical and archaeological sites). We discuss the role of guidelines within the context of other governance mechanisms such as SFM policies, trade regulations and non-state market-driven (NSMD) standards, including certification systems. The review provides a comprehensive resource for those developing guidelines, or defining sustainability standards for market access or compliance with public regulations, and/or concerned about the sustainability of forest biomass harvesting. We recommend that those developing or updating guidelines consider (i) the importance of well-defined and understood terminology, consistent where possible with guidelines in other jurisdictions or regions; (ii) guidance based on locally relevant research, and periodically updated to incorporate current knowledge and operational experience; (iii) use of indicators of sensitive soils, sites, and stands which are relevant to ecological processes and can be applied operationally; and (iv) incorporation of climate impacts, long-term soil carbon storage, and general carbon balance considerations when defining sustainable forest biomass availability. Successful implementation of guidelines depends both on the relevance of the information and on the process used to develop and communicate it; hence, appropriate stakeholders should be involved early in guideline development.
  • Korrensalo, Aino; Mehtätalo, Lauri; Alekseychik, Pavel; Uljas, Salli; Mammarella, Ivan; Vesala, Timo; Tuittila, Eeva-Stiina (2020)
    We quantified the role of spatially varying vegetation composition in seasonal and interannual changes in a boreal bog’s CO2 uptake. We divided the spatially heterogeneous site into six microform classes based on plant species composition and measured their net ecosystem exchange (NEE) using chamber method over the growing seasons in 2012–2014. A nonlinear mixed-effects model was applied to assess how the contributions of microforms with different vegetation change temporally, and to upscale NEE to the ecosystem level to be compared with eddy covariance (EC) measurements. Both ecosystem respiration (R) and gross photosynthesis (PG) were the largest in high hummocks, 894–964 (R) and 969–1132 (PG) g CO2 m−2 growing season−1, and decreased toward the wetter microforms. NEE had a different spatial pattern than R and PG; the highest cumulative seasonal CO2 sink was found in lawns in all years (165–353 g CO2 m−2). Microforms with similar wetness but distinct vegetation had different NEE, highlighting the importance of vegetation composition in regulating CO2 sink. Chamber-based ecosystem-level NEE was smaller and varied less interannually than the EC-derived estimate, indicating a need for further research on the error sources of both methods. Lawns contributed more to ecosystem-level NEE (55–78%) than their areal cover within the site (21.5%). In spring and autumn, lawns had the highest NEE, whereas in midsummer differences among microforms were small. The contributions of all microforms to the ecosystem-level NEE varied seasonally and interannually, suggesting that spatially heterogeneous vegetation composition could make bog CO2 uptake temporally more stable.