Alexander Eder

Identification of phosphorus emission hotspots in agricultural catchments

An enhanced transport-based management approach is presented, which is able to support cost-effective water quality management with respect to diffuse phosphorus pollution. Suspended solids and particulate phosphorus emissions and their transport were modeled in two hilly agricultural watersheds (Wulka River in Austria and Zala River in Hungary) with an improved version of the catchment-scale PhosFate model. Source and transmission areas were ranked by an optimization method in order to provide a priority list of the areas of economically efficient (optimal) management alternatives. The model was calibrated and validated at different gauges and for various years. The spatial distribution of the emissions shows that approximately one third of the catchment area is responsible for the majority of the emissions. However, only a few percent of the source areas can transport fluxes to the catchment outlet. These effective source areas, together with the main transmission areas are potential candidates for improved management practices. In accordance with the critical area concept, it was shown that intervention with better management practices on a properly selected small proportion of the total area (1–3%) is sufficient to reach a remarkable improvement in water quality. If soil nutrient management is also considered in addition to water quality, intervention on 4–12% of the catchment areas can fulfill both aspects.

The seasonal dynamics of the stream sources and input flow paths of water and nitrogen of an Austrian headwater agricultural catchment.

Our study examines the source aquifers and stream inputs of the seasonal water and nitrogen dynamics of a headwater agricultural catchment to determine the dominant driving forces for the seasonal dynamics in the surface water nitrogen loads and concentrations. We found that the alternating aquifer contributions throughout the year of the deep and shallow aquifers were the main cause for the seasonality of the nitrate concentration. The deep aquifer water typically contributed 75% of the total outlet discharge in the summer and 50% in the winter when the shallow aquifer recharges due to low crop evapotranspiration. The shallow aquifer supplied the vast majority of the nitrogen load to the stream due to the significantly higher total nitrogen concentration (11 mg-N/l) compared to the deep aquifer (0.50 mg-N/l). The main stream input pathway for the shallow aquifer nitrogen load was from the perennial tile drainages providing 60% of the total load to the stream outlet, while only providing 26% of the total flow volume. The diffuse groundwater input to the stream was the largest input to the stream (39%), but only supplied 27% to the total nitrogen load as the diffuse water was mostly composed of deep aquifer water.

Indirect nitrogen losses of managed soils contributing to greenhouse emissions of agricultural areas in Austria: results from lysimeter studies

A considerable share of greenhouse gas emissions, especially N2O, is caused by agriculture, part of which can be attributed to indirect soil emissions via leaching and runoff. Countries have to report their annual emissions, which are usually calculated by using the default value of 0.3 for FracLEACH, a factor that represents the fraction of nitrogen losses compared to total nitrogen inputs and sources. In our study we used 22 lysimeters, covering a wide range of soils, climatic conditions and management practices in Austria, to evaluate nitrogen losses through leaching and to calculate FracLEACH. The terms of the nitrogen mass balance of the lysimeters were directly measured for several years. Both grassland and arable land plots gave significantly smaller values of FracLEACH than the default value. For grassland, FracLEACH values of only 0.02 were found which varied very little over the entire observation period. For arable sites, FracLEACH values were higher (around 0.25) and showed significant variability between years due to variations in crop rotation, fertilization rates, and yields.

A simple and flexible field-tested device for housing water monitoring sensors at point discharges.

The Water Monitoring Enclosure (WME) provides a simple and flexible housing for many types of sensors for continuous measurements of water parameters (physical, chemical, or biological) and provides the opportunity of representative sampling for external analyses. The WME ensures a minimum internal water level and this ensures that the internal monitoring equipment remains submerged even when there is no flow into the enclosure. The limited diameter of the inflow pipe and water volume in the WME buffers the flow velocity from dramatic changes. The device ensures that the sediment entering the enclosure from the inflow will be conveyed through the enclosure with minimal sediment accumulation. The device is powered purely from natural hydraulic forces, so it requires no power source, and requires little additional maintenance beyond periodic cleaning. If desired, the WME can also measure discharge entering the device through additional modifications. Water samples were taken throughout the year to validate the effectiveness of the WME. The comparisons of the influent water to the water in the WME for all parameters were below the laboratory analysis standard error or below the limit of quantification, indicating that the water in the WME is representative of the influent water.

HYDROBOD: obtaining a GIS-based hydrological soil database and a runoff coefficient calculator for Lower Austria

In the State of Lower Austria, rainfall-runoff models it is an acknowledged method used when estimating flood peak discharges for small catchments where there are no direct gauging observations. An important input parameter for these models is the volumetric runoff coefficient, which was estimated by rather simple methods until now (for instance the CN-method of the U.S.G.S), which did not provide very reliable results. The project HYDROBOD intends to provide a solid and homogeneous database of some basic soil hydraulic parameters over the whole state area (over 19.000 km2) and contains a hydrological model for estimation of these runoff coefficients which takes into account some relevant input variables. In a first step (HYDROBOD I), hydraulic soil parameters are calculated by regionalization methods and assembled for the whole area of Lower Austria, using a GIS-database (ESRI ArcGIS 10.2; at a 50 x 50 m grid). They include soil layer depth, storage capacity, saturated vertical conductivity, plus a classification of the soil reaction types referring to storm events. These data are now available for three soil layers, from top soil down to 1 m below surface. In a second step (HYDROBOD II), a vertical onedimensional event model was set up which allows to calculate storm event runoff coefficients on a cell-by-cell basis for any given area in Lower Austria. This model uses the hydraulic soil parameters obtained from HYDROBOD I, plus an estimation of unsaturated vertical pore flux and a soil water storage model with several modules. This model needs the following input parameters: a shape-file with the catchment area, and pairs of rainfall data (duration + rainfall depth). Results of a calculation process are: runoff coefficients (as an average over the catchment area) for each pair of rainfall data, and for different initial wetness scenarios (from “dry” to “saturated”). Validation of the model is promising.

Nitrogen-Induced Formation of Nano-Structured Precipitations in the Ti-W-C-N System

A general trend in the field of hardmetals is to achieve a refinement of the microstructures, usually by using sub-micron powders as raw materials. In this study, an alternative route to produce fine structures within the fcc hard phase (W,Ti)(C,N) is investigated: nitrogen indiffusion into (W,Ti)C leads to precipitation of tungsten-rich phases. The mechanism of precipitation (lamella- and labyrinth-like structures with a size of 100-400nm) is thought do be discontinuous segregation on the one hand and spinodal decomposition on the other hand. Hot-pressed (W,Ti)(C,N) samples of different compositions were annealed at different temperatures and C activities in high-pressure N2 atmosphere. The composition and resulting structures of the precipitates were correlated with composition of the (W,Ti)(C,N) phase as well as with annealing conditions. An outlook of a possible application of the observed phenomena to powder particles is given to achieve micron-sized particles of this hard phase with nanometer-sized structures as a raw material for fine-grained hardmetals.