Sensorgestützte herbizidfreie Unkrautregulierung: Sensorgestützte herbizidfreie Unkrautregulierung in pfluglos angebauten Futtererbsen und Ackerbohnen

Diese Schriftenreihe informiert, ob mit dem Anbau abfrierender Zwischenfrüchte und anschließender mechanischer Unkrautregulierung der Unkrautbesatz in nachfolgend pfluglosen Anbausystemen von Futtererbsen und Ackerbohnen hinreichend reduziert werden kann, sodass kein Herbizid eingesetzt werden muss.Speziell auf den Standorten in der Erzgebirgsvorlage (Löß und Verwitterungsböden) konnte mit einem Aussaattermin der Zwischenfrucht im Juli eine durchschnittliche Reduktion im Nmin Oberboden (0-30 cm) um 25 kg N/ha erzielt werden. Darüber hinaus konnte gezeigt werden, dass eine Aussaat der Zwischenfrüchte Ende August keinen Effekt erzielt. Die ganzheitliche System-Betrachtung im Verbund, d.h. eine zeitgerechte Etablierung der Zwischenfrüchte und ein Minimum von 3 Striegelgängen, erwiesen sich als erfolgreich. In diesem System konnte ein Striegel erfolgreich sensorgesteuert teilflächenspezifisch eingesetzt werden. Redaktionsschluss: 22.12.202

Impacts of elevated dissolved CO2 on a shallow groundwater system: reactive transport modeling of a controlled-release field test

One of the risks that CO2 geological sequestration imposes on the environment is the impact of potential CO2/brine leakage on shallow groundwater. The reliability of reactive transport models predicting the response of groundwater to CO2 leakage depends on a thorough understanding of the relevant chemical processes and key parameters affecting dissolved CO2 transport and reaction. Such understanding can be provided by targeted field tests integrated with reactive transport modeling. A controlled-release field experiment was conducted in Mississippi to study the CO2-induced geochemical changes in a shallow sandy aquifer at about 50 m depth. The field test involved a dipole system in which the groundwater was pumped from one well, saturated with CO2 at the pressure corresponding to the hydraulic pressure of the aquifer, and then re-injected into the same aquifer using a second well. Groundwater samples were collected for chemical analyses from four monitoring wells before, during and after the dissolved CO2 was injected. In this paper, we present reactive transport models used to interpret the observed changes in metal concentrations in these groundwater samples. A reasonable agreement between simulated and measured concentrations indicates that the chemical response in the aquifer can be interpreted using a conceptual model that encompasses two main features: (a) a fast-reacting but limited pool of reactive minerals that responds quickly to changes in pH and causes a pulse-like concentration change, and (b) a slow-reacting but essentially unlimited mineral pool that yields rising metal concentrations upon decreased groundwater velocities after pumping and injection stopped. During the injection, calcite dissolution and Ca-driven cation exchange reactions contribute to a sharp pulse in concentrations of Ca, Ba, Mg, Mn, K, Li, Na and Sr, whereas desorption reactions control a similar increase in Fe concentrations. After the injection and pumping stops and the groundwater flow rate decreases, the dissolution of relatively slow reacting minerals such as plagioclase drives the rising concentrations of alkali and alkaline earth metals observed at later stages of the test, whereas the dissolution of amorphous iron sulfide causes slowly increasing Fe concentrations

Feature Detection, Characterization and Confirmation Methodology: Final Report

This is the final report of the NUMO-LBNL collaborative project: Feature Detection, Characterization and Confirmation Methodology under NUMO-DOE/LBNL collaboration agreement, the task description of which can be found in the Appendix. We examine site characterization projects from several sites in the world. The list includes Yucca Mountain in the USA, Tono and Horonobe in Japan, AECL in Canada, sites in Sweden, and Olkiluoto in Finland. We identify important geologic features and parameters common to most (or all) sites to provide useful information for future repository siting activity. At first glance, one could question whether there was any commonality among the sites, which are in different rock types at different locations. For example, the planned Yucca Mountain site is a dry repository in unsaturated tuff, whereas the Swedish sites are situated in saturated granite. However, the study concludes that indeed there are a number of important common features and parameters among all the sites--namely, (1) fault properties, (2) fracture-matrix interaction (3) groundwater flux, (4) boundary conditions, and (5) the permeability and porosity of the materials. We list the lessons learned from the Yucca Mountain Project and other site characterization programs. Most programs have by and large been quite successful. Nonetheless, there are definitely 'should-haves' and 'could-haves', or lessons to be learned, in all these programs. Although each site characterization program has some unique aspects, we believe that these crosscutting lessons can be very useful for future site investigations to be conducted in Japan. One of the most common lessons learned is that a repository program should allow for flexibility, in both schedule and approach. We examine field investigation technologies used to collect site characterization data in the field. An extensive list of existing field technologies is presented, with some discussion on usage and limitations. Many of the technologies on the list were in fact used during the characterization of Yucca Mountain and elsewhere by LBNL personnel. The study also includes emerging technologies and identifies the need to develop better estimation of important parameters for repository siting. Notable emerging technologies include 3-D seismic and satellite-based remote sensing and wireless micro electro mechanical systems (MEMS) sensors. They enable cost-effective and ubiquitous monitoring to be applied for site characterization. We list and classify the types of uncertainties involved in site characterization. Uncertainties can exist in all aspects of site characterization: data, interpretation, conceptualization, and modeling. We use the Swedish program to exemplify such uncertainties. We also devote a chapter on geochemical issues regarding the interaction between groundwater and natural and engineered barrier materials. A recommendation has been made to take advantage of the recent advancement in geochemical modeling capabilities in natural systems. Although it is not of immediate relevance at the preliminary investigation stage, it serves as a good reminder that geochemical investigation efforts should not be overlooked at any stage in the repository program. We construct a synthetic preliminary-investigation site based on an extensive data set available from a geoscientific project in Japan, which we use as a 'real' site to evaluate uncertainties resulting from hydrogeological modeling and examine strategies for characterizing a new site. We plan various preliminary-investigation configurations and conduct preliminary numerical investigations at the synthetic site. We construct a model of the 'real' site for each PI configuration, make predictions of particle travel times, and compare against the 'real' data obtained from the 'real' model. We conclude that drilling as many as nine boreholes does not necessarily improve the understanding of the site compared to drilling as few as three boreholes, unless there is an underlying structure that is larger than the spacing of the boreholes. The parameters that affect the outcome of the predictions most are: (1) effective porosity, (2) boundary conditions, and (3) fault properties, all of which are very difficult to estimate in the field and are full of uncertainties. Of the three, we recommend NUMO expend efforts to assess the latter two at preliminary investigation sites. To obtain large-scale averaged permeabilities, we recommend conducting long-time and long-interval pumping tests in boreholes. We also find that the temperature data can reduce some uncertainties regarding the boundary conditions. Finally, we summarize recommendations that NUMO might consider during preliminary site investigations

Rock fracture aperture and gas conductivity measurements in situ

Recent interest in locating a nuclear waste repository in unsaturated fractured rock has lead to rock characterization studies. Essential to a study of this type is the measurement of natural rock fracture apertures and gas conductivities. Six pneumatic connections located in unsaturated crystalline rock were tested using gas flow tests conducted in parallel boreholes. It was believed, but not possible to verify accurately enough given the limited orientation data, that the pneumatic connections represented individual fractures. For the purpose of analysis, it was assumed that the pneumatic connections tested were "equivalent" to isolated individual fractures intersecting both test boreholes. Analytical equations were developed to treat fractures inclined to the borehole axis. These equations were used to calculate equivalent pneumatic apertures and equivalent gas conductivities from the test data. Equivalent pneumatic apertures calculated ranged from 9 to 200 microns and equivalent gas conductivities ranged from 3.78E-3 to 1.92 m/s.hydrology collectio

Sensitivity of Pressure Measurements for Detecting Leakage of Carbon Dioxide From Geological Storage Sites

A common method used to detect leakage from a natural gas storage reservoir includes measuring fluid pressures and watching for pressure increases in the formation above the reservoir. Here we investigate the sensitivity of these pressure measurements for detecting leakage from underground geological formations used for CO2 storage. Calculations are made regarding the rate and extent of pressure buildup associated with different rates of leakage. The number of observation wells needed to detect specified leakage rates are estimated for a range of hydrogeological parameters. In addition, the magnitude of pressure buildup caused by leakage is compared to common forms of "noise" in the pressure data, namely, pressure fluctuations associated with earth tides, barometric pressure variations, precipitation, and instrument resolution and drift. Based on a comparison between the magnitude of the pressure response and the "noise" in the pressure signal, an assessment of the utility of pressure measurements for monitoring leakage from geological storage projects is provided

Real-time quadrupole mass spectrometer analysis of gas in borehole fluid samples acquired using the U-Tube sampling methodology

Sampling of fluids in deep boreholes is challenging because of the necessity to minimize external contamination and maintain sample integrity during recovery. The U-tube sampling methodology was developed to collect large volume, multiphase samples at in situ pressures. As a permanent or semi-permanent installation, the U-tube can be used for rapidly acquiring multiple samples or it may be installed for long-term monitoring applications. The U-tube was first deployed in Liberty County, TX to monitor crosswell CO2 injection as part of the Frio CO2 sequestration experiment. Analysis of gases (dissolved or separate phase) was performed in the field using a quadrupole mass spectrometer, which served as the basis for determining the arrival of the CO2 plume. The presence of oxygen and argon in elevated concentrations, along with reduced methane concentration, indicate sample alteration caused by the introduction of surface fluids during borehole completion. Despite producing the well to eliminate non-native fluids, measurements demonstrate that contamination persists until the immiscible CO2 injection swept formation fluid into the observation wellbore

Evaluating the effectiveness of liquid diversion around an underground opening when evaporation is non-negligible

Interpreting observations of seepage into underground openings is often complicated by evaporative potentials created by the necessity to ventilate the openings. Evaporation removes liquid from the seepage face. By doing so, it reduces both the likelihood of seepage onset and the seepage flux, and thus can enhance the perceived effectiveness of the capillary barrier. We modeled liquid-release tests at the proposed high-level waste repository in Yucca Mountain, using an enhanced version of the EOS9 module of iTOUGH2, which incorporates evaporation as Fickian diffusion. The evaporation boundary layer thickness (BLT) over which diffusion occurs was estimated using free-water evaporation experiments conducted at Yucca Mountain under known relative humidity, temperature, and ventilation conditions. The BLT, which represents the thickness of the laminar flow regime, is inversely related to the ambient airflow velocity. At Yucca Mountain, the estimated values of BLT were 5–7 mm for open underground tunnels and 20 mm for closed niches. Compared to previous models that neglected the effect of evaporation, this new approach shows significant improvement in capturing seepage fluctuations into the open tunnels. This study provides more confidence in the use of the calibrated seepage model for simulations of seepage under different ventilation conditions