Emissions of porewater compounds and gases from the subaquatic sediment disposal site “rodewischhafen”, hamburg harbour

In the year 1993 a confined and unused harbour basin was used to store 290,000 m3 of fine-grained dredged material from Hamburg harbour. About 70% of the deposit surface was water covered. The edge areas were above the water table and covered with reed. Emissions of dissolved compounds into the groundwater, as well as surface gas emissions were measured from 1994 to 1996. As indicators for water fluxes from the deposit we used NH4+ and HCO3− because of their high concentrations in mud porewater in comparison to groundwater. The average concentrations of NH4+ and HCO3− in the porewater increased during 2 years from 85 to 250 mg NH4+ 1−1 and from 2.0 to 3.1 g HCO3− 1−1, while the groundwater samples showed constant values of 8 mg NH4+ 1−1 and 0.7 g HCO3− 1−1. Furthermore, the average gas emissions over the water surface were 3.2 g CH4 m−2 d−1 and 0.8 g CO2 m−2 d−1. In contrast, no methane and 3.0 g CO2 m−2 d−1 were emitted from land areas. The results indicated, that there were no significant emissions of mud porewater compounds into the groundwater but high CH4-emissions over the water covered surface of the mud deposit.</jats:p

Relevance of soil physical properties for the microbial oxidation of methane in landfill covers

The microbial oxidation of methane in landfill cover soils offers great potential to reduce methane emissions from landfills. High methane degradation rates can only be accomplished if the supply of atmospheric oxygen to the methanotrophic community is adequate. Thus, if environmental variables such as pH or nutrient status are not limiting, system performance is suggested to be governed by the share of pores available for gas transport. Diffusion tests as well as column studies were conducted to investigate the effect of air-filled porosity and degree of compaction on diffusivity and methane oxidation efficiency. Results show that the effective diffusion coefficient governing oxygen migration through soil is exponentially related to air-filled porosity space and can be significantly decreased by compaction. Discontinuity and tortuosity of the pore system strongly impeded diffusive migration at air-filled porosities below 10%. In the column study, soil gas composition and methane oxidation rates correlated with both the degree of compaction and the magnitude of advective bottom flux. Low aeration and hence low methane oxidation rates prevailed at high compaction rates and/or high bottom fluxes whereas high rates could be maintained at lower fluxes and/or low compaction rates. At a low degree of compaction (75% of the Proctor density), fluxes of 3.5 g CH(4) m(-2) h(-1) could be fully oxidized at all times by a sandy loam, the capacity limit of which was not reached during the experiment. Our studies suggest that soils intended for use as methane-oxidizing biocovers are to maintain an air-filled porosity of at least 14 vol.%. At low and medium degree of compaction, this is provided by sands, loamy sands, sandy loams and some of the coarsely textured loams. (C) 2010 Elsevier Ltd. All rights reserved

Assessment of the methane oxidation capacity of compacted soils intended for use as landfill cover materials

The microbial oxidation of methane in engineered cover soils is considered a potent option for the mitigation of emissions from old landfills or sites containing wastes of low methane generation rates. A laboratory column study was conducted in order to derive design criteria that enable construction of an effective methane oxidising cover from the range of soils that are available to the landfill operator. Therefore, the methane oxidation capacity of different soils was assessed under simulated landfill conditions. Five sandy potential landfill top cover materials with varying contents of silt and clay were investigated with respect to methane oxidation and corresponding soil gas composition over a period of four months. The soils were compacted to 95% of their specific proctor density, resulting in bulk densities of 1.4-1.7 g cm(-3), reflecting considerably unfavourable conditions for methane oxidation due to reduced air-filled porosity. The soil water content was adjusted to field capacity, resulting in water contents ranging from 16.2 to 48.5 vol.%. The investigated inlet fluxes ranged from 25 to about 100 g CH(4) m(-2) d(-1), covering the methane load proposed to allow for complete oxidation in landfill covers under Western European climate conditions and hence being suggested as a criterion for release from aftercare. The vertical distribution of gas concentrations, methane flux balances as well as stable carbon isotope studies allowed for clear process identifications. Higher inlet fluxes led to a reduction of the aerated zone, an increase in the absolute methane oxidation rate and a decline of the relative proportion of oxidized methane. For each material, a specific maximum oxidation rate was determined, which varied between 20 and 95 g CH(4) m(-2) d(-1) and which was positively correlated to the air-filled porosity of the soil. Methane oxidation efficiencies and gas profile data imply a strong link between oxidation capacity and diffusive ingress of atmospheric air. For one material with elevated levels of fine particles and high organic matter content, methane production impeded the quantification of methane oxidation potentials. Regarding the design of landfill cover layers it was concluded that the magnitude of the expected methane load, the texture and expected compaction of the cover material are key variables that need to be known. Based on these, a column study can serve as an appropriate testing system to determine the methane oxidation capacity of a soil intended as landfill cover material. (C) 2010 Elsevier Ltd. All rights reserved

Temporal variability of soil gas composition in landfill covers

In order to assess the temporal variability of the conditions for the microbial oxidation of methane in landfill cover soils and their driving variables, gas composition at non-emissive and strongly emissive locations (hotspots) was monitored on a seasonal, daily and hourly time scale on an old, unlined landfill in northern Germany. Our study showed that the impact of the various environmental factors varied with the mode of gas transport and with the time scale considered. At non-emissive sites, governed by diffusive gas transport, soil gas composition was subject to a pronounced seasonal variation. A high extent of aeration, low methane concentrations and a high ratio of CO(2) to CH(4) were found across the entire depth of the soil cover during the warm and dry period, whereas in the cool and moist period aeration was less and landfill gas migrated further upward. Statistically, variation in soil gas composition was best explained by the variation in soil temperature. At locations dominated by advective gas transport and showing considerable emissions of methane, this pattern was far less pronounced with only little increase in the extent of aeration during drier periods. Here, the change of barometric pressure was found to impact soil gas composition. On a daily scale under constant conditions of temperature, gas transport at both types of locations was strongly impacted by the change in soil moisture. On an hourly scale, under constant conditions of temperature and moisture, gas migration was impacted most by the change in barometric pressure. It was shown that at diffusion-dominated sites complete methane oxidation was achieved even under adverse wintry conditions, whereas at hotspots, even under favorable dry and warm conditions, aerobic biological activity can be limited to the upper crust of the soil. (C) 2010 Elsevier Ltd. All rights reserved

Fungus culturing, nutrient mining and geophagy: A geochemical investigation of Macrotermes and Trinervitermes mounds in southern Africa

Termite mounds are commonly enriched in clay and nutrients relative to surrounding topsoils. We hypothesized that: (1) nutrient enrichment of mounds differs between fungus-culturing (FC) and non-FC termites; (2) FC termites preferentially acquire materials rich in scarce nutrients which promote growth of their fungus cultures; and (3) micro-nutrient enrichment in mounds of FC termites is beneficial for wildlife. In a preliminary investigation of these hypotheses, we sampled mounds (and adjacent topsoil) of Macrotermes (FC) and Trinervitermes (non-FC) termites in Namibia and South Africa, respectively. Analyses included: 27 elements by ICPMS after a nitric acid-hydrogen peroxide digest, organic carbon, a seven fraction particle size analysis, and pH and EC (1:5 soil:water extracts). Macrotermes mounds showed significant (1.6-3.7-fold) enrichment of 23 of the 27 elements analysed relative to topsoil. By contrast, Trinervitermes mounds showed no enrichment. Clay enrichment of Macrotermes mounds (4.7-6.5-fold) was strongly correlated with element enrichment (r 2 range: 0.76-0.77), suggesting that amendment of soil texture is a main factor in enrichment. Marked enrichment of only certain nutrients in mounds - namely Mn, Co, Cu and Se - was evident at certain nutrient-poor sites, suggesting that specific materials such as Mn oxides (which adsorb Co, Cu and Se) may be gathered by termites in disproportionate amounts relative to their abundance in soils. These nutrients are likely to enhance the productivity of the fungus culture and hence the termite colony. Parts of certain mounds were enriched in Se (1.3-3.6 mg Se kg-1) to a degree likely to attract geophagy. It is suggested that in some landscapes Macrotermes mounds provide a critical supply of micro-nutrients to wildlife. © 2009 The Zoological Society of London.Articl

Untersuchung des Sickerwasser- und Stoffeintrags aus Hafenschlick-Spuelfeldern in den oberen Grundwasserleiter der Hamburger Elbmarsch

SIGLEAvailable from TIB Hannover: RO3338(17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

20 years of long-term water balance measurements of a landfill cover system with components constructed from pre-treated dredged material

The cover system of the mono-landfill Hamburg-Francop for disposal of dredgedmaterial comprises a mineral liner of pre-treated fine-grained dredged material (‘METHAmaterial’) and an overlying drainage layer of pre-treated sandy dredged material (‘METHAsand’). Water balance and effectiveness of the cover with respect to minimising infiltration into the waste body have been investigated in a test field of 50 m length and 10 m width (lysimeter) from 1996 to 2015. Continous measurements of water flow (average annual discharge from the mineral liner of 14.9 mm with a dreasing tendency) and hydro-chemical measurements indicate that the mineral liner is performing well since more than 20 years after construction. Reasons are the low saturated hydraulic conductivity of about 1 * 10-9 m/s and the large thickness of the liner of 1.5 m; the high load of 2.5 m thick covering layers; the 1.0 m thick lateral drainage layerconstructed from relatively slowly-draining METHA-sand; the sufficient amount of plant available water in the recultivation layer; and, finally, to a certain extent the root barrier on top of the drainage layer, composed of compacted loam. The measurements are continued by Hamburg Port Authority as part of the long-term monitoring of the Francop site

Eigenschaften und Funktionen von Auenboeden an der Elbe Festschrift fuer Guenter Miehlich

Available from TIB Hannover: RO 3338(44) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman