Anwendung eines neuen Feldanalysenverfahrens zur Untersuchung der Stabilität von Arsen und seinen anorganischen Spezies in aquatischen Systemen

Using of a New Field Analysis Method to Investigate the Stability of Arsenic and its Inorganic Species in Aquatic Systems The stability of arsenic species in aquatic systems is limited by the possibilities of chemical and biochemical reactions. Redox reactions and bioalkylation lead to changes of the species ratios. In this work, the stability of As(III) and As(V) was examined at storage of distilled, de-ionized, and drinking water at different conditions (refrigerator/room temperature; daylight/darkness) and additions (sulfuric acid; ascorbic acid). The determination of these species was carried out by a modified spectrophotometric method, suitable for laboratory analysis as well as for field analysis. The results show that chemical oxidation and biochemical reduction can occur. Sulfuric acid is favourable for the stabilization of total arsenic and of the inorganic species.     

Use of the Anion‐Exchange Resin Amberlite IRA‐93 for the Separation of Arsenite and Arsenate in Aqueous Samples

The method described uses the separation of As(III) and As(V) species in aqueous samples by means of the anion‐exchange resin Amberlite IRA‐93. The samples were acidified using acetic acid and passed through a glass column filled with pre‐treated Amberlite IRA‐93 resin. As(III) was poorly adsorbed on the anionic exchanger material, whereas As(V) was retained. The arsenic concentration was measured in the column effluent by graphite furnace AAS (GF‐AAS). The retained As(V) was eluted from the column using 1 M NaOH. Prior to the determination of the As(V) concentration in the NaOH eluate, the eluate was passed through a glass column filled with a cation‐exchange resin (Amberlite 200) to remove sodium ions and minimize the Na⁺ interference with the AAS determination. After calibration the method was applied to the separation of As(III) and As(V) species in two aqueous extracts of arsenic contaminated soils. The results were compared with those obtained from an on‐line separation and determination of As(III) and As(V) in the aqueous soil extracts using a state of the art HPLC‐ICP‐MS system.     

Abschätzung und Beeinflussbarkeit der Arsenmobilität in kontaminierten Böden

Assessment and Modification of Arsenic Mobility in Contaminated Soil Arsenic concentration in the seepage of contaminated soils of an old tannery site is assessed using batch and column experiments. The effect of reducing conditions, pH, and ionic strength is also investigated. The iron oxide rich subsoil (C‐horizon) is the main source of groundwater pollution with arsenic. In this horizon, mobilization can increase as a result of reducing conditions upon periodical water saturation. Therefore, the potentially mobile arsenic is determined by a reductive dissolution of the poorly crystalline iron oxide fraction using 0.1 M ascorbic acid. Arsenic concentration can be reduced from 100 μg/L to below 20 μg/L by an increase of ionic strength (e.g. by a 0.01 M CaCl₂ solution). Arsenic contaminated soils should be limed regularly in order to maintain the highest possible calcium concentration in the soil solution.     

Zielvorgaben für Pflanzenschutzmittelwirkstoffe und andere Schadstoffe in Oberflächengewässern

Quality Targets for Pesticides and Other Pollutants in Surface Waters Surface waters are not only adversely affected by industrial and municipal wastewaters but also by diffuse sources. For the control of the ecological water quality, so‐called quality targets are set. The quality targets are threshold concentrations for hazardous substances related to the protected goods like water ecosystems, drinking water supply, sediments, or fishing. In this paper, quality targets for the protection of aquatic life in surface waters were derived on the basis of a concept developed by the International Commission for the Protection of the Rhine (Internationale Kommission zum Schutze des Rheins – IKSR). The quality targets for the selected hazardous substances, which mainly belong to the chemical class of pesticides, were calculated using ecotoxicological results for species of bacteria, algae, fish, and small crustaceans, as the four trophic standards of the water ecosystem. In cooperation with the Federal Environmental Agency (Umweltbundesamt – UBA) the effect data were taken from ecotoxicological data bases. According to the concept of the IKSR, the lowest test result for the most sensitive species was multiplied by an assessment factor. This proceeding concerns the difficulty in describing the complex interactions in water ecosystems with toxicity data of single laboratory experiments for a few organisms. For seven pesticides quality targets below 0.1 μg/L were proposed. These results show that the ecotoxicologically based quality targets might be even lower than the limit values for pesticides in drinking water of 0.1 μg/L. But for most of the substances the determined values are significantly higher. The great concentration range of quality targets demonstrates distinctly that one standard concentration for all pesticides could not be given with regard to the different effects on aquatic organisms.