The main objective of WP2 is the analysis of the effects of land use and different agricultural practices on the quantity and quality of DOM delivered to stream ecosystems.
WP 2.1. Laboratory experiments with Micro-Lysimeters:
Microlysimeters will be used to analyze the interaction between soil, landuse type, and agricultural practices on the DOM quantity and quality of the soil water. During the last two years, BAW has assembled a lab facility consisting of 16 microlysimeters with flexible dimensions (diameter and height each between 10-40 cm). Each of the cylinders may be controlled for intensity of percolating water. Sensors are used to measure soil water content and soil matric potential in various depths. Each microlysimeter is placed on a balance to facilitate calculation of total inflow and outflow volumes. The amount of leachate is recorded and the quality of the leachate is measured. All data obtained are stored and quality assured using on purpose developed software.
We will use the microlysimeter facility to investigate the effect of different landuse types (grassland, arable land) and types of agricultural management (mineral fertilizers, organic fertilizers) currently applied in Lower Austria. We will use a set of different soil types of the HOAL catchment. This will enable us to link microlysimeter experiments to measurements of DOM within HOAL. Using conservative tracers such as Br– will allow us to distinguish between preferential and matric flow paths. At WCL, we will additionally analyze surface runoff water from different treatments as well as extracts from different DOM sources, such as plant material, manure, or benthic algae, to identify DOM spectra of the unprocessed sources.
WP 2.2 Spatio-temporal water analyses in the HOAL (Hydrological Open Air Lab):
The HOAL Petzenkirchen is situated in the immediate vicinity of BAW. It consists of a catchment area of 66 ha connected to a 600-m-long headwater stream within an agriculturally used environment. The stream has a 50 m wide forested riparian buffer zone and is fed by a variety of drainage outlets, natural springs and tributaries which are continuously monitored for water quantity and water quality as well as a large number of climatic data and supplemental information (for details, see http://hoal.hydrology.at). The HOAL Petzenkirchen has been identified as priority area for the current FTI strategy for water which has been developed by the Federal Government of Lower Austria.
During year 1 of the project, water samples will be taken directly at the effluents of the different water sources and along the 400 m study reach in monthly intervals at low water level and during storms in order to investigate the DOM quality of the different water sources. The significance of the different effluents for the DOM concentration at different hydrological situations (baseflow vs. stormflow), and changes in DOM composition in the stream due to microbial DOM processing will be investigated. This is possible because the facilities of the HOAL catchment allow for high frequency water sampling at the various locations of HOAL.