Margarete Mages

First results on the water chemistry, algae and trophic status of an Andean acidic lake system of volcanic origin in Patagonia (Lake Caviahue)

The acidic caldera lake Caviahue (Patagonia, Argentina) and its main tributaries were studied on two dates during September 1998. The main results are: The acidity of the Lake Caviahue (pH: 2.56, acidity: >5 mmol H+ l−1) is controlled by the extremely acidic Upper Rio Agrio (pH: 1.78, acidity: >20 mmol H+ l−1). The high sulphate contents of both the river and the lake can be attributed to sulphuric acid generated by the uptake of sulphurous gases in the crater lake of Copahue Volcano at approximately 2800 m a.s.l. The high concentrations of both Fe and trace metals (e.g. Cr, Ni, Zn) in Lake Caviahue originate from sulphur–acid interactions with the predominantly volcanic geology of the catchment area. The P-rich andesitic geology influences both the Upper and Lower Rio Agrio and Lake Caviahue. Both were found to have high phosphorus concentrations (300–500 μg P l−1) indicative of a high potential for eutrophication. The plankton community consisted of bacterioplankton, phytoplankton and rotifers. The phytoplankton was dominated by one green alga, Keratococcus raphidioides (>90% of total abundance) followed by a green sphaerical and Chlamydomonas sp. The total phytoplankton density was about 15 000 cells ml−1 in the upper 10 m of the water column. Rotifers were represented by one bdelloid species and their abundance was highly variable (360–4040 ind l−1) in the water columm. In the Upper and Lower Rio Agrio, the epilithic community was dominated by one chloroccocal species and two species of Ulothricales. According to trophic categories based on phytoplankton density and TP concentration, Lake Caviahue can be classified as mesotrophic/eutrophic. However, chlorophyll a concentrations observed were not in agreement with this state.

Determination of heavy metals in biofilms from the River Elbe by total-reflection X-ray fluorescence spectrometry

Abstract Heavy metal contents of aquatic biofilms isolated from stones collected from, and ceramic plates exposed in, the River Elbe were determined by total-reflection X-ray fluorescence spectrometry (TXRF). The fractions of several elements (K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Pb) referred to the dry mass are 100 to 60 000-fold higher in the biofilm matrix compared with the bulk water phase. Biofilms grown on the exposed plates have a mass fraction of the determined elements higher by a factor of 2–3 compared with the biofilms derived from stones. These differences may be attributed to the different ages of the biofilms.

The use of a portable total reflection X-ray fluorescence spectrometer for field investigation ☆

b ´ Abstract A newly developed, portable total reflection X-ray fluorescence (TXRF) spectrometer was tested during a field campaign on Chilean lakes and a German river in January 2002. The field measurements were compared with laboratory measurements carried out on a stationary instrument in the German laboratory. For method validation certified reference material (NIST SRM 1640 Trace elements in natural water) and water samples from different freshwater sources were analyzed with both techniques and evaluated statistically. Based on these preliminary results, it could be concluded that the portable TXRF is a useful technique for the quantitative elemental screening of freshwater samples during field campaigns. Future tests with biological samples (e.g. biofilms and zooplankton), and suspended matter will provide information about the suitability of the portable TXRF for these materials. 2003 Elsevier B.V. All rights reserved.

Cold plasma ashing improves the trace element detection of single Daphnia specimens by total reflection X-ray fluorescence spectrometry ☆

The recently developed dry method for the element determination of single freshwater microcrustacean specimens (Daphnia) using total reflection X-ray fluorescence (TXRF) spectrometry showed that inhomogeneities of the biological material on the glass carriers resulted in some cases in high background and hampered the detection of certain trace elements (e.g. Cr, Ni). The aim of this study was to test how inhomogeneities of the biological material can be reduced using cold plasma ashing (CPA) techniques. For that, single specimens of the microcrustacean Daphnia pulex prepared according to the dry method were measured by TXRF before and after CPA. To determine the efficiency of the removal of organic matrix, the background and signal-to-background relationship of 28 samples were analyzed. The results showed (1) a highly significant reduction of the background by CPA fluctuating between 26 and 46% (all elements) and (2) a significant increase of the signal-to-background relationship by the factor 1.5–2.5 (all elements) and a much better detection of Cr, Pb, As and Se. The element concentrations (with exception of Cr, Ni and Pb) after ashing were in the same range or slightly higher than that before ashing. No significant differences between the two treatments were observed for Mn, As, Pb, Se (November), Sr (November), Cr (March) and Pb (March). The element concentration of P, K, Ca, Cu, Zn, Cr (November), Fe and Rb were significantly higher after ashing. In general, they increased by 1.5–13.6% and were highest for Rb (March) and P (November). In contrast, the element concentration of Ni and Cr (only March) decreased significantly after ashing (Ni: 91.6–92.1%, Cr: 91.3%). We recommend the use of CPA for biological material in the microgram-range as a routine method for TXRF analysis, especially when trace elements in minute concentrations are of interest.

A method for trace element determination of single Daphnia specimens using total reflection X-ray fluorescence spectrometry☆

Abstract Two new preparation techniques for total-reflection X-ray fluorescence (TXRF) element determination of single freshwater crustacean specimens (dry weight: 3–40 μg ind−1) have been developed and tested using Daphnia pulex from a deep, oligotrophic freshwater lake located in southern Chile. Dry method: Specimens were washed with 0.2 μm filtered lake water and frozen in liquid nitrogen. The freeze-dried Daphnia specimens were weighed using an ultra-fine microbalance and placed on quartz glass carriers for TXRF analysis. Wet method: Specimens were washed with 0.2 μm filtered lake water and placed on quartz glass carriers for TXRF analysis and dried in air. The dry weight was determined using the previously established body length–dry weight relationship. Method validation for both the dry and the wet preparation method in combination with TXRF spectrometry for the element determination in small single freshwater crustaceans showed that both methods can be used for routine investigations. There were no significant differences between the dry and the wet methods concerning the elements Ca, K, Fe, Zn, Br, P, Cu, but the determination of Mn, S and Sr revealed significant differences between the two methods. It seems that the dry method yields more precise results, but the wet method is easier to handle in the field when samples cannot be fixed with liquid nitrogen.

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.

Former mining activities influence Uranium concentrations in the Elbe river near Magdeburg

This paper presents data of dissolved and total uranium concentrations after the 2002 flood event, at a flood in spring 2003, and during an extreme low water period 2003 in the river Elbe. In addition, data from several Saale river tributaries are evaluated. The results reveal the remaining pollution potential in the Mansfelder Land catchment that requires the development of remediation strategies.

P-fractions in the sediments of an extremely acidic lake in Patagonia, Argentina

In all oligotrophic and some eutrophie waterbodies, the total flux of phosphorus (P) takes plaee from the water eolumn toward the sediments (HAKANSON & ]ANSSON 1983). Under some eonditions, especially in nutrient-rieh environments, the P releases from sediments (internalload) may exeeed other inputs (GmTERMAN et al. 1983, HAKANSON & ]ANSSON 1983). The opposite meehanism is ealled P fixation eapaeiry by sediments. Both are eontrolled by physieal (e.g. temperature, sedimentation, resuspension, ete.), ehemieal (e.g. pH, redox potential, ete.) and biologieal (e.g. biorurbation, baeterial aetivity, ete.) proeesses (BOSTROM et al.1982). Many studies in relation to the P dynamies in sediments are foeused on fresh waters (BOSTROM et al. 1982, GOLTERMAN et al. 1983, TEMPORETTI & PEDROZO 2000). There are a few studies on aeidie waters speeifieally related to aeidie mining lakes (HUPFER et al. 1998, FRIESE et al. 1998). The aim of this work was to understand the meehanism that eontrols the fixation and/or release ofP in the sediments of a naturally extremely aeidie lake and its availability to the water eolumn, and to eompare these meehanisms with those that oeeur in freshwater sediments (neutral and alkaline).

Akkumulation von Schwermetallen in Biofilmen der Elbe

Biofilme sind komplexe, heterogene Systme aus Zellen und anorganischen Partikeln, die eingebettet in einer organischen polymeren Matrix mikrobiellen Ursprungs an Oberflachen haften (Characklis und Marshall 1990). Sie spielen in naturlichen Gewassersystemen eine bedeutende Rolle beim Abbau oder der Akkumulation von Schadstoffen. Ziel der vorliegenden Untersuchung war es, die Aufnahme bzw. Sorption von ausgewahlten Schwermetallen an aquatischen Biofilmen unter definierten Bedingungen im Labor zu untersuchen.