Surface energy exchange in pristine and managed boreal peatlands

Surface-atmosphere energy exchange is strongly ecosystem-specific. At the same time, as the energy balance constitutes responses of an ecosystem to environmental stressors including precipitation, humidity and solar radiation, it results in feedbacks of potential importance for the regional climate. Northern peatlands represent a diverse class of ecosystems that cover nearly 6 x 10(6) km(2) in the Boreal region, which makes the inter-comparison of their energy balances an important objective. With this in mind we studied energy exchange across a broad spectrum of peatlands from pristine fens and bogs to forested and agriculturally managed peatlands, which represent a large fraction of the landscape in Finland and Sweden. The effects of management activities on the energy balance were extensively examined from the micrometeorological point of view, using eddy covariance data from eight sites in these two countries (56 degrees 12'-62 degrees 11' N, 13 degrees 03'-30 degrees 05' E). It appears that the surface energy balance varies widely amongst the different peatland types. Generally, energy exchange features including the Bowen ratio, surface conductance, coupling to the atmosphere, responses to water table fluctuations and vapour pressure deficit could be associated directly with the peatland type. The relative constancy of the Bowen ratio in natural open mires contrasted with its variation in tree-covered and agricultural peatlands. We conclude that the impacts of management and the consequences of land-use change in peatlands for the local and regional climate might be substantial.Peer reviewe

Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes

The Nordic Centre of Excellence CRAICC (Cryosphere–Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011–2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change–cryosphere interactions that affect Arctic amplification.</p

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

When terrigenous dissolved organic carbon (tDOC) rich in chromophoric dissolved organic matter (tCDOM) enters the ocean, solar radiation mineralizes it partially into dissolved inorganic carbon (DIC). This study addresses the amount and the rates of DIC photoproduction from tDOC and the area of ocean required to photomineralize tDOC. We collected water samples from 10 major rivers, mixed them with artificial seawater, and irradiated them with simulated solar radiation to measure DIC photoproduction and the photobleaching of tCDOM. The linear relationship between DIC photoproduction and tCDOM photobleaching was used to estimate the amount of photoproduced DIC from the tCDOM fluxes of the study rivers. Solar radiation was estimated to mineralize 12.5 +/- 3.7 Tg C yr(-1) (10 rivers)(-1) or 18 +/- 8% of tDOC flux. The irradiation experiments also approximated typical apparent spectral quantum yields for DIC photoproduction (phi(lambda)) over the entire lifetime of the tCDOM. Based on phi(lambda)s and the local solar irradiances in river plumes, the annual areal DIC photoproduction rates from tDOC were calculated to range from 52 +/- 4 (Lena River) to 157 +/- 2 mmol C m(-2) yr(-1) (Mississippi River). When the amount of photoproduced DIC was divided by the areal rate, 9.6 +/- 2.5 x 10(6) km(2) of ocean was required for the photomineralization of tDOC from the study rivers. Extrapolation to the global tDOC flux yields 45 (31-58) Tg of photoproduced DIC per year in the river plumes that cover 34 (25-43) x 10(6) km(2) of the ocean.Peer reviewe

ASPA:a static analyser to support learning and continuous feedback on programming courses:an empirical validation

Abstract For decades there have been arguments how to teach programming in the basic courses. Supportive intervention methods to improve students’ learning and methods to improve assessment process have been widely studied. There are various successful methods to each topic separately, but only a few of them fit for both. In this work, we aimed at validating ASPA a static analyser tool that supports learning and continuous feedback on programming courses. For this purpose, we designed and conduct an empirical study among 236 students enrolled in the basic programming course, that voluntary adopted the tools during the project development activities. We first profiled the students, then, evaluated the attitude toward using ASPA, the perceived ease of use, and the perceived usefulness. Results showed that ASPA is a good helper for the entire course and especially the student’s programming assignments, and it also helps to improve the students’ grades

Occurrence and water partitioning of PFOA and PFOS in biogas plant end products and uptake by radish

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