Quality of Surface Waters (Chemistry) 1991
Pollutant Impacts in Sediments and Eels: Methodology
Sampling and Analysis
The heavy metals copper, zinc, lead, cadmium, nickel and chromium were determined in sediment samples. Average values of the single tests are depicted in each water section. There were 1 to 10 measuring sites in each water section.
The quality of water sections was evaluated according to data derived by calculating average values from individual bore sample measurement values, and a further condensation for the average values of all bore-samples measurements in water sections. Samples taken by the frozen-core bore method were weighted for average values on the basis of the respective thickness of the accumulation zone.
Samples in the water sections of the Spree and Dahme were taken by mud-claw. Because sediments in these flowing water sections are considerably less thick than those of Havel waters, it can be assumed that the sampled 40 cm of sediments correspond to the accumulation horizon and that measured values are relatively comparable, in spite of the different sampling processes.
Values determined for DDT, Lindane and PCB in sediments are based on data from 1989, 1990, or 1991. An average value was taken when long-term measurements of water sections were available.
The depiction of DDT and PCB impacts in eels was derived from measurements made from 1989 to 1992. The most current year of sampling in individual water sections was used as a reference.
The PCB concentrations listed are based on values determined as PCB6. In order to quantify the total PCB concentrations, six PCBs (IUPAC Nos. 28, 52, 101, 138, 153 and 180) of the 209 known PCBs were used as a standard substance, PCB6. The total PCB amount corresponds, according to the experience of the Federal States’ Working Group for Waste (LAGA), five times the PCB6 amount. This formula is also used here as total PCBs.
A total of 461 sediment samples and 578 eel samples were evaluated in order to categorize 65 measured sections into quality classes. The only quality sections depicted are those for which 3 individual measurement values per water section were available. The number of individual tests per section was between 3 and 21 sediment samples and between 3 and 69 eel samples. The only exception is the measurement site section of the Teltow canal/Dahme tributary. Here only one measurement value was used as a basis for evaluation. The depicted DDT and PCB impacts of sediments in this water section match the results of earlier investigations.
The results of the heavy metal, pesticide and PCB measurements were also divided into 7 quality classes; as the chemical-physical and biological parameters had been.
General impact criteria for the evaluation of heavy metals in sediments are not available up to now. The evaluation made here employs the “argillaceous rock standard” – supplemented by measurements made in the Berlin area of the original geological material – as reference standard for the geo-accumulation index (Igeo-Klasseneinteilung according to Müller 1979).
This index is a scale for the size of current loads in relation to heavy metal concentration in the original geologic material. The evaluation of anthropogeneous heavy metal inputs proceeds from a geochemical “background level” which should take into consideration the natural heavy metal concentrations in sediments. A range of values was given for geochemical backgrounds of individual heavy metals in the Berlin area (Pachur and Ahrens 1991), since the large range of individual results made the fixation of an exactly defined value more difficult.
The “argillaceous rock standard”, as order of magnitude for natural impact levels, fixed the following as background values in mg/kg dry substance (ds): copper, 45; zinc, 95; lead, 20; cadmium, 0.3; nickel, 68; and chromium, 90. These values are within the determined range for original impacts in the Berlin area, except for chromium and nickel. Chromium was assigned a background impact of 45 mg/kg because of conditions in the Berlin area, and nickel was assigned 20 mg/kg.
The geo-accumulation index employed for the evaluation of heavy metal impacts in sediments is based on these background values. In order to avoid overly evaluating natural ranges and the very low anthropogenic inputs, background concentrations were multiplied by a factor of 1.5, to define the upper limit of the lowest impact class. The doubling of this value form the upper limit of the next higher class, and so forth. It is an exponential evaluation.
The evaluation of PCB in sediments is based on statements of the Office of Fisheries. High PCB impacts in fish were found in investigations of the Office of Fisheries beginning at sediment values of 450 mg/kg dry substance. This value was then set as the upper limit of class 2 to 3. Because limit and index values for DDT and Lindane were not available, the classification from the Environmental Atlas of 1985 was used. This means – departing from the method used for other substances – that the class category does not allow any conclusions about the absolute impact degree of sediments. The DDT and Lindane values here are to be interpreted relative to each other.
The classification of contaminant loads of PCB in eels is oriented to the regulation regarding the highest permissible amounts of pollutants in foodstuffs (SHmV of 23 March 1988). No highest permissible foodstuff level for total-PCBs in eels is given. A total-PCB-value of 7.0 mg/kg fresh weight (fw) was assigned on the basis of highest tested values for single examples of the PCB group. This value connects to the high end of quality class 2-3. The DDT classification is based on the Plant Pesticide Maximum Level Regulation (PHmV of 16 October 1989). Under the present classification, the maximum allowable limit of DDT (3.5 mg/kg fw) for eels prescribed therein is the same as the higher value for quality class 2-3.