TY - JOUR A1 - Balcke, Gerd U. A1 - Hahn, M. A1 - Oswald, Sascha Eric T1 - Nitrogen as an indicator of mass transfer during in-situ gas sparging JF - Journal of contaminant hydrology N2 - Aiming at the stimulation of intrinsic microbial activity, pulses of pure oxygen or pressurized air were recurrently injected into groundwater polluted with chlorobenzene. To achieve well-controlled conditions and intensive sampling, a large, vertical underground tank was filled with the local unconfined sandy aquifer material. In the course of two individual gas injections, one using pure oxygen and one using pressurized air, the mass transfer of individual gas species between trapped gas phase and groundwater was studied. Field data on the dissolved gas composition in the groundwater were combined with a kinetic model on gas dissolution and transport in porous media. Phase mass transfer of individual gas components caused a temporary enrichment of nitrogen, and to a lower degree of methane, in trapped gas leading to the formation of excess dissolved nitrogen levels downgradient from the dissolving gas phase. By applying a novel gas sampling method for dissolved gases in groundwater it was shown that dissolved nitrogen can be used as a partitioning tracer to indicate complete gas dissolution in porous media. KW - Inter-phase mass transfer KW - Groundwater KW - Remediation KW - Gas sparging KW - Nitrogen KW - Methane KW - Kinetics KW - Bitterfeld Y1 - 2011 U6 - https://doi.org/10.1016/j.jconhyd.2011.05.005 SN - 0169-7722 VL - 126 IS - 1-2 SP - 8 EP - 18 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - López-Tarazón, José Andrés A1 - Lopez, Pilar A1 - Lobera, Gemma A1 - Batalla Villanueva, Ramon J. T1 - Suspended sediment, carbon and nitrogen transport in a regulated Pyrenean river JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Regulation alters the characteristics of riversty transforming parts of them into lakes, affecting their hydrology and also the physical, chemical, and biological characteristics and dynamics. Reservoirs have proven to be very effective retaining particulate materials, thereby avoiding the downstream transport of suspended sediment and the chemical substances associated with it (e.g. Carbon, C or Nitrogen, N). The study of fluvial transport of C and N is of great interest since river load represents a major link to the global C and N cycles. Moreover, reservoirs are the most important sinks for organic carbon among inland waters and have a potential significance as nitrogen sinks. In this respect, this paper investigates the effects of a Pyrenean reservoir on the runoff, suspended sediment, C and N derived from the highly active Esera and Isabena rivets. Key findings indicate that the reservoir causes a considerable impact on the Esera-Isabena river fluxes, reducing them dramatically as almost all the inputs are retained within the reservoir. Despite the very dry study year (2011-2012), it can be calculated that almost 300,000 t of suspended sediment were deposited into the Barasona Reservoir, from which more than 16,000 were C (i.e. 2200 t as organic C) and 222 t were N. These values may not be seen as remarkable in a wider global context but, assuming that around 30 hm(3) of sediment are currently stored in the reservoir, figures would increase up to ca. 2.6 x 10(6) t of C (i.e. 360,000 t of organic C) and 35,000 t of N. Nevertheless, these values are indicative and should be treated with caution as there is incomplete understanding of all the processes which affect C and N. Further investigation to establish a more complete picture of C and N yields and budgets by monitoring the different processes involved is essential. (C) 2015 Elsevier B.V. All rights reserved. KW - Suspended sediment KW - Carbon KW - Nitrogen KW - Temporal dynamics KW - Barasona Reservoir KW - River Esera KW - Ebro basin Y1 - 2016 U6 - https://doi.org/10.1016/j.scitotenv.2015.06.132 SN - 0048-9697 SN - 1879-1026 VL - 540 SP - 133 EP - 143 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Reverey, Florian A1 - Großart, Hans-Peter A1 - Premke, Katrin A1 - Lischeid, Gunnar T1 - Carbon and nutrient cycling in kettle hole sediments depending on hydrological dynamics: a review JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - Kettle holes as a specific group of isolated, small lentic freshwater systems (LFS) often are (i) hot spots of biogeochemical cycling and (ii) exposed to frequent sediment desiccation and rewetting. Their ecological functioning is greatly determined by immanent carbon and nutrient transformations. The objective of this review is to elucidate effects of a changing hydrological regime (i.e., dry-wet cycles) on carbon and nutrient cycling in kettle hole sediments. Generally, dry-wet cycles have the potential to increase C and N losses as well as P availability. However, their duration and frequency are important controlling factors regarding direction and intensity of biogeochemical and microbiological responses. To evaluate drought impacts on sediment carbon and nutrient cycling in detail requires the context of the LFS hydrological history. For example, frequent drought events induce physiological adaptation of exposed microbial communities and thus flatten metabolic responses, whereas rare events provoke unbalanced, strong microbial responses. Different potential of microbial resilience to drought stress can irretrievably change microbial communities and functional guilds, gearing cascades of functional responses. Hence, dry-wet events can shift the biogeochemical cycling of organic matter and nutrients to a new equilibrium, thus affecting the dynamic balance between carbon burial and mineralization in kettle holes. KW - Drought KW - Rewetting KW - Temporary pond KW - Kettle hole KW - Organic matter KW - Nitrogen KW - Phosphorus Y1 - 2016 U6 - https://doi.org/10.1007/s10750-016-2715-9 SN - 0018-8158 SN - 1573-5117 VL - 775 SP - 1 EP - 20 PB - Springer CY - Dordrecht ER -