Wolfgang Ahlf

Chemical mobility and bioavailability of sediment-bound heavy metals influenced by salinity

The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 µm-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.

Recovery of metals from acid waste water by Cyanidium caldarium

SummaryCyanidium caldarium grows in acid water obtained from a bacterial leaching procedure and the alga is capable of precipitating metals from the solution. This study demonstrates that changes in culture and oxidation-reduction conditions may result in a different bioaccumulation of metals.

Comparison of five bioassay techniques for assessing sediment-bound contaminants

Biological response could not be predicted based on chemical concentration of the sediment contaminants. Bioassays integrate the response of test organisms to contaminants and nutrients. Comparative results of five acute bioassays indicated that Neubauer phytoassay was the most sensitive. The microbial biomass and algal growth tests indicated a response to the availability of contaminants and nutrients. These results suggest the usefulness of a diversity of bioassays in toxicity testing of sediment contamination.

Bioassay responses to sediment elutriates and multivariate data analysis for hazard assessment of sediment-bound chemicals

A sediment study, involving both chemical and biological analyses, was carried out in the Hamburg harbour area. A total of 71 stations were sampled during 1988 and the sediments extracted using a 1:4 sediment:water ratio either with or without an addition of a water-soluble detergent to solubilize organic compounds. The resulting extracts were applied in algal and bacterial assays to measure toxicity. A principal components analysis showed that no single bioassay explained all the variation in toxicity among the locations studied. Hierarchical cluster analysis was used to rank sediments into four groups based on their toxicity. The relationship of toxic responses to the chemistry of the sediments was determined using varimax factor analysis. One factor was loaded with algal responses and mercury contents of sediments, another with bacterial responses and Lindane contents of sediments.

Über die Anreicherung von Blei durch Süßwassergrünalgen unter Berücksichtigung verschiedener Außenfaktoren

Summary Accumulation of lead by two species of green algae was analyzed. The species investigated were Fritschiella tuberosa as well as a wild strain and a cell wall-free mutant of Chlamydomonas reinbardii . Lead was determined by means of atomic absorption spectroscopy. Under certain conditions lead accounted for up to 20 % of algal dry weight. Our investigations confirm that 4 factors essentially influence lead accumulation 1. pH-value: The final lead concentration in the algae is greatest at low pH-values in the medium, especially when the lead is complexed by EDTA. 2. Chemical form of lead: Ionic lead is accumulated to a considerable greater degree and much more rapidly than complexed lead. 3. Lead concentration in the medium: When lead is present in the medium in the ionic state, its concentration in the algae increases linearly as a function of concentration in the medium (up to 2.5 ppm). 4. Density of algae in the mediumFor a constant lead concentration in the medium, accumulation will be greater the lower the algal density. The significance of this result, in particular for the field, is discussed. Temperature appears to play an insignificant role.

Effects of Phenanthrene on Lemna minor in a Sediment–Water Systemand the Impacts of UVB

The objective of this study was to evaluate if the Lemna -bioassay is appropriate to test contaminated sediments. A mixture of sand was spiked with phenanthrene to investigate whether sediment-bound pollutants can affect the plants via direct contact of the roots or the underside of the leaves. After 24 h of equilibration for sorption/desorption processes, the test was carried out in the sediment–water mixture, and another test was performed with the aqueous phase which was separated from the sediment. The growth inhibition of Lemna was nearly the same in both tests. Hence it follows that the toxicant is adsorbed from the aqueous phase via the underside of the leaves and sediment bound phenanthrene is not bioavailable. Polycyclic aromatic hydrocarbons are known to show photoinduced toxicity to plants in the presence of UV which is a result of photosensitization reactions in the plant and photomodification to more toxic and better soluble photoproducts. Photoinduced toxicity could be observed in the water phase during UVB treatment, whereas the presence of suspended sediment probably lowered the UV intensity, resulting in a lower growth inhibition.

Direktbestimmung von Cd, Cu und Ni im Elbeästuar mit Hilfe der Zeeman-Atomabsorptionsspektroskopie und Matrixmodifikation

Es werden Verfahren zur Direktbestimmung von Cd, Cu und Ni im Elbeastuar vorgestellt, die auf Zeeman-Untergrundkorrektur und Matrixmodifikation beruhen.

Sediment Toxicity Data

The overall goal of a well-designed and well-implemented sampling and analysis program is to measure accurately what is really the status of the area studied. Environmental decisions are made on the assumption that analytical results are, within known limits of accuracy and precision, representative of site conditions. Many sources of error exist that could affect the analytical results. These sources of error may include sample collection methods, sample handling, preservation, and transport; personnel training; analytical methods; data reporting; and record keeping. Therefore, a quality assurance program has to be designed for each sediment quality evaluation to minimize these sources of error and to control all phases of the monitoring process.