Olaf Büttner

Variations of DOM Quality in Inflows of a Drinking Water Reservoir: Linking of van Krevelen Diagrams with EEMF Spectra by Rank Correlation

Elevated concentrations of dissolved organic matter (DOM) such as humic substances in raw water pose significant challenges during the processing of the commercial drinking water supplies. This is a relevant issue in Saxony, Central East Germany, and many other regions worldwide, where drinking water is produced from raw waters with noticeable presence of chromophoric DOM (CDOM), which is assumed to originate from forested watersheds in spring regions of the catchment area. For improved comprehension of DOM molecular composition, the seasonal and spatial variations of humic-like fluorescence and elemental formulas in the catchment area of the Muldenberg reservoir were recorded by excitation emission matrix fluorescence (EEMF) and ultrahigh-resolution mass spectrometry (FT-ICR-MS). The Spearman rank correlation was applied to link the EEMF intensities with exact molecular formulas and their corresponding relative mass peak abundances. Thereby, humic-like fluorescence could be allocated to the pool of oxygen-rich and relatively unsaturated components with stoichiometries similar to those of tannic acids, which are suspected to have a comparatively high disinfection byproduct formation potential associated with the chlorination of raw water. Analogous relationships were established for UV absorption at 254 nm (UV(254)) and dissolved organic carbon (DOC) and compared to the EEMF correlation.

Geostatistical Analysis of Surface Sediments in an Acidic Mining Lake

An exact morphometric description of Mining Lake 111, Brandenburg, Germany, was obtained after a new survey in 1996 by the staff of the water research department. Volume and surface area of ML111 were calculated based on values of this survey. An actual bathymetric map was created from the datapool which was the basis for the selection of sampling sites where we obtained sediment cores to describe the geochemistry of the lake sediments. Principal Component Analysis (PCA) was carried out to examine patterns and similarities between concentrations of different heavy metals. The patterns are different for the three basins within the lake. The spatial distributions of 12 elements in the sediment surface were estimated with a geostatistical procedure (Ordinary Kriging) as well as with a conventional interpolation method. The structure found with PCA was confirmed by the plots from spatial interpolation. Due to the complexity of the lake morphometry and bathymetry 66 sediment cores taken at 47 sampling sites were not sufficient to reduce the spatial variance distributions to acceptable values.

Reservoirs as sentinels of catchments: the Rappbode Reservoir Observatory (Harz Mountains, Germany)

Reservoirs can be viewed as sentinels of their catchments and a detailed monitoring of reservoir systems informs about biogeochemical and hydrological processes at the catchment scale. We developed a comprehensive online monitoring system at Rappbode reservoir, the largest drinking water reservoir in Germany, and its inflows. The Rappbode Reservoir Observatory comprises of a set of online-sensors for the measurement of physical, chemical, and biological variables and is complemented by a biweekly limnological sampling schedule. Measurement stations are deployed at the four major inflows into the system, at the outlets of all pre-reservoirs, as well as in the main reservoir. The newly installed monitoring system serves both scientific monitoring and process studies, as well as reservoir management. Particular emphasis is paid to the monitoring of short-term dynamics and many variables are measured at high temporal resolution. As an example, we quantitatively documented a flood event which mobilised high loads of dissolved organic carbon and changed the characteristics of the receiving reservoir from eutrophic to dystrophic within a few days. This event could have been completely missed by conventional biweekly sampling programs, but is relevant for biogeochemical fluxes at the catchment scale. We also show that the high frequency data provide a deeper insight into ecosystem dynamics and lake metabolism. The Rappbode Reservoir Observatory; moreover, offers a unique study site to apply, validate, and develop state of the art lake models to improve their predictive capabilities.

Spatial variability of metal pollution in groyne fields of the Middle Elbe--implications for sediment monitoring.

High spatial heterogeneity of physical and chemical sediment properties was observed in both horizontal and vertical directions of deposits in a groyne field of the Middle Elbe. The respective sediment cores were less polluted on the top compared to consolidated deeper layers, indicating a decreasing trend of contamination in the river basin. In contrast to water quality monitoring, the impact of the large Elbe flood in 2002 was still visible in the deeper layers (5-30 cm) of the groyne field sediments six years after the event. Due to the fact that the environmental risk increases with erosion potential of discharge and contamination level of sediments, monitoring for environmental risk must capture not only surface sediments but also deeper layers up to an anticipated erosion depth.

A method for automated, daily, temperature-based vertical streambed water-fluxes

Heat is increasingly used as a natural tracer to quantify water fluxes at the groundwater-surface waterinterface. We present a systematic approach to monitor and evaluate stream and streambed temperatures to derive daily-updated temperature-based water exchange fluxes between the stream and the streambed. Specifically designed multi-level temperature sensors coupled with a data logger and GSM modem are used to monitor temperature in the stream and streambed and transfer this data daily to a database. A suite of MATLAB scripts with structured query language (SQL) commands is applied to extract the data for processing using an inverse numerical model to estimate water flow based on the measured temperatures. Compared to common analytical approaches, which typically require sinusoidal diurnal temperature pattern, our numerical model can utilize temperature records without daily variations. Temperature-based calculations to quantify vertical water fluxes at the stream-groundwater interface can provide a supplement to, or even a replacement of, calculations based on vertical hydraulic gradients and Darcy’ law.

Phosphorus input by nordic geese to the eutrophic Lake Arendsee, Germany

Phosphorus import by nordic geese (Anser fabalis and Anser albifrons) was investigated in Lake Arendsee, located in the Saxony-Anhalt region, Altmark, Germany during the period 1996 to 1997. Phosphorus contained in geese excrement on the ice was measured in the winters 1996 and 1997. In February 1996 (after 9 days of frozen lake surface) two excrement fields amounted to 80 ha and 30 ha in area and in January 1997, 10 days after ice closure, the excrement field was 106 ha large. The weight of excrement was estimated to be 148 to 266 g m -2 fresh weight (mean 201 g m -2 ) in 1996 and 83 g m -2 to 408 g m -2 (mean of 243 g m -2 ) in 1997. The average of phosphorus content was 8.5 mg g -1 dry weight in 1997 and 9.2 mg g -1 in 1996. Based on these values the phosphorus input attributed to nordic geese was calculated. Our results demonstrated a phosphorus import in 1996 after 9 days of frozen lake surface of 251 kg and in 1997 after 10 days of freezing of 173 kg. During 100 days of wintering, the nordic geese on Lake Arendsee produced a phosphorus load of 2.8 t in 1996 and 1.7 t in 1997. Compared with the annual phosphorus import from different sources, the contribution by nordic geese was 88 % in 1996 and 92 % in 1997. Its yearly phosphorus load during the winter months appears as a significant eutrophication factor for the trophic level of Lake Arendsee. However, the annual external load is approximately 10 % of the phosphorus poolsize in the lake water, and even less when considering the amount lodged in the bottom sediments.

Uncertainties in dissolved organic carbon load estimation in a small stream

Abstract Dissolved organic carbon (DOC) transported by rivers represents an important link between carbon pools of terrestrial and oceanic ecosystems. However, it is unclear how frequent DOC must be sampled to obtain reasonable load estimates. Here, we used continuous records of the specific UV absorption coefficient (SAC) and discharge from a headwater stream at the Ore Mountains (Germany) to calculate load errors depending on DOC sampling frequency. SAC was used as a proxy for DOC. The results show that the load was underestimated by 13-19% with monthly, 10-13% with bi-weekly and 7-9% with weekly DOC samplings, respectively. We conclude that collecting additional data from high discharge events decrease the error significantly.

Relationship between the elemental composition of stream biofilms and water chemistry-a catchment approach.

As benthic biofilms mediate essential functions in stream ecosystems (e.g., carbon flux, storage of nutrients and other substances), the element-specific regulation of the biofilm composition is of great interest. We tested whether (1) the elemental composition of biofilms is related to that of the water column and (2) there are different accumulation patterns from the dissolved phase (adsorption) and the particulate phase (incorporation of suspended matter). We analysed biomass parameters, nutrients and metals in biofilms and surface waters at 28 sites within a stream network (Bode catchment, Germany). Algal biomass in biofilms was dominated by diatoms. The P/C ratio in biofilms was positively related to total phosphorus of surface water (and to the proportion of agricultural area in the catchment) indicating phosphorus limitation of biofilms, whereas the N/C ratio was not related to nitrate levels of surface water, and neither the P/C nor the N/C ratio to the concentration of dissolved organic carbon (DOC) of surface water. Biofilms were enriched in metals compared to their concentrations in water. The metals in biofilms were positively related to the concentration of dissolved metals in surface water for iron and strontium (but not for manganese, copper, zinc, arsenic or lead) and to the concentrations of particle-associated metals of surface waters for strontium and lead. Manganese and arsenic were the metals with a negative effect on the biomasses of biofilm diatoms and cyanobacteria. Overall, we observed element-specific accumulation patterns in biofilms with selected elements being related to the water column while others were probably subject to biofilm-internal processes.

MeCa, a toolbox for the calculation of metabolism in heterogeneous streams

Summary The estimation of stream metabolism represents a useful technique for characterising the ecological status of natural lotic systems. The existing tools for investigating metabolism in situ demand expert knowledge, provide only a few options, ignore possible groundwater effects and often rely on modelled input data, such as gas exchange, that could be subject to error. We have developed MeCa, a user-friendly MATLAB toolbox that contains different options – including the groundwater correction – for the calculation of metabolism. A detailed explanation of all the calculation steps and the various calculation options is given in the Appendix S1. The functions of MeCa can be tested using the test data set provided. We conducted sensitivity tests to assess the effect of certain parameters (reaeration, travel time, groundwater oxygen concentration, mean depth and width) and other measurements (oxygen, temperature, pressure) on the metabolism estimation. Uncertainties in the parameters have a greater effect than those that apply to the measurements. The parameters reaeration coefficient and mean depth are the most sensitive input data. Results from sensitivity analyses show the complexity of metabolism studies in streams and the importance of direct calculations. MeCa includes all relevant calculation options, and thus makes a contribution towards the standardisation of metabolism studies.

Entwicklung eines Schadstoffausbreitungsmodells zur stoffbezogenen Risikoanalyse und-bewertung extremer Hochwasserereignisse am Beispiel des Landkreises und der Stadt Bitterfeld

(wolf.vontuempling@ufz.de)Das Hochwasser im Einzugsgebiet der Mulde vom August 2002 hat gezeigt, dass neben der zerstorenden Wirkung des Wassers auchGefahrdungen fur Mensch und Umwelt durch die mobilisierten, transportierten und abgelagerten Schadstoffe entstanden sind, beisp ielsweisedurch Schwermetalle, Arsen, PAK und HCH. Das Risikomanagement zukunftiger extremer Hochwasserereignisse erfordert daher neben derquantitativen Hydrologie auch die Schadstoffausbreitung fur dieses Einzugsgebiet zu berucksichtigen.