[1] This work presents a stream tube-based analytical approach to evaluate reduction in groundwater contaminant flux resulting from partial mass reduction in a nonaqueous phase liquid (NAPL) source zone. The reduction in contaminant flux, R j , discharged from the source zone is a remediation performance metric that has a direct effect on the fundamental drivers of remediation: protection of human health and the environment. Closed form expressions are provided for analyzing remediation performance under conditions of joint spatial variability of both groundwater flow and NAPL content. The performance measures derived here are expressed in terms of measurable parameters. Spatial variability is described within a Lagrangian framework where aquifer hydrodynamic heterogeneities are characterized using nonreactive travel time distributions, while NAPL spatial distribution heterogeneity can be similarly described using reactive travel time distributions. The combined statistics of these distributions are used to evaluate the relationship between reduction in contaminant mass, R m , and R j . A portion of the contaminant mass in the source zone is assumed to be removed via in situ flushing remediation, with the initial and final conditions defined as steady state natural gradient groundwater flow through the contaminant source zone. The combined effects of aquifer and NAPL heterogeneities are shown to be captured in a single parameter, reactive travel time variability, which was determined to be the most important factor controlling the relationship between R m and R j . It is shown that as heterogeneity in aquifer properties and NAPL spatial distribution increases, less mass reduction is required to achieve a given flux reduction, although the overall source longevity increases. When rate-limited dissolution is important, the efficiency of remediation, in terms of both mass and flux reduction, is reduced. However, at many field sites the combined effects of field-scale heterogeneities and site aging will result in favorable relationships between mass reduction and flux reduction.

Tree growth in boreal forests is limited by nitrogen (N) availability. Most boreal forest trees form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve the uptake of inorganic N and also have the capacity to decompose soil organic matter (SOM) and to mobilize organic N ('ECM decomposition'). To study the effects of 'ECM decomposition' on ecosystem carbon (C) and N balances, we performed a sensitivity analysis on a model of C and N flows between plants, SOM, saprotrophs, ECM fungi, and inorganic N stores. The analysis indicates that C and N balances were sensitive to model parameters regulating ECM biomass and decomposition. Under low N availability, the optimal C allocation to ECM fungi, above which the symbiosis switches from mutualism to parasitism, increases with increasing relative involvement of ECM fungi in SOM decomposition. Under low N conditions, increased ECM organic N mining promotes tree growth but decreases soil C storage, leading to a negative correlation between C stores above- and below-ground. The interplay between plant production and soil C storage is sensitive to the partitioning of decomposition between ECM fungi and saprotrophs. Better understanding of interactions between functional guilds of soil fungi may significantly improve predictions of ecosystem responses to environmental change.

Abstract. Few hydrological studies have been conducted in Greenland, other than on glacial hydrology associated with the ice sheet. Understanding permafrost hydrology and hydroclimatic change and variability, however, provides key information for understanding climate change effects and feedbacks in the Arctic landscape. This paper presents a new, extensive, and detailed hydrological and meteorological open access data set, with high temporal resolution from a 1.56 km 2 permafrost catchment, with a lake underlain by a through-talik close to the ice sheet in the Kangerlussuaq region, western Greenland. The paper describes the hydrological site investigations and utilized equipment, as well as the data collection and processing. The investigations were performed between 2010 and 2013. The high spatial resolution, within the investigated area, of the data set makes it highly suitable for various detailed hydrological and ecological studies on catchment scale. The data set is available for all users via the PANGAEA database, http://doi.pangaea.de/10.1594/PANGAEA.836178.

Abstract. The effect of solute injection mode is examined in the stochastic-advective' framework. For three-dimensional heterogeneous aquifers, uniform resident injection of solute results in nonlinear propagation of mass arrival time mean and variance with distance. Injection in flux results in a linear propagation of mean mass arrival time and mass arrival time variance that is both lower and appears to reach a linear regime more rapidly than uniform resident injection. Implementation of instantaneous injections for both modes as boundary conditions for mathematical and numerical models is discussed.

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