Summer air quality over an artificial lake

In the summer of 1998, the air quality (indicators: CO, NO, NO₂, O₃) above the water surface of the Lake Balderey (Essen, Ruhr area, North Rhine-Westphalia, Germany), an artificial lake used for recreation purposes, was measured using the Fourier transform infrared spectroscopy (FTIR) and differential optical absorption spectroscopy (DOAS) remote measurement methods. The lake, with an area of 3 km² was created by damming the Ruhr and is surrounded by higher ground. In calm, bright weather conditions, this location results in a low-exchange situation (formation of temperature inversions, cold air dynamics) with a sustained impact on pollutant concentrations over the lake. The results of trace substance measurements (1/2 h mean values) were compared with values from comparison stations (suburban, high traffic and forest) located outside the area of the lake. In general, it was found that mean CO and NO concentrations over the lake were very low (0.3 ppm and 7.5 ppb, respectively). NO₂ values (15 ppb) were some 3.5 times higher than those recorded at the forest station and O₃ values, at 27 ppb, almost reached the same level as at the forest station (30 ppb). Mass flow densities as a function of wind direction, diurnal courses, differences between weekdays and weekends and comparisons with air quality standards are presented for the lake station.     

Dechlorination and destruction of PCDD,PCDF and PCB on selected fly ash from municipal waste incineration

The potential of fly ash to dechlorinate and destroy PCDD, PCDF and PCB was tested under oxygen deficient conditions in the laboratory. Specifically, two types of fly ash were compared, originating either from a fluidized bed incinerator using Ca(OH)₂ spray (FA1), or a stoker incinerator without Ca(OH)₂ impact (FA2).

Results from the present study indicate that on FA2 type fly ash, the degradation processes of OCDD, OCDF and D₁₀CB occurred primarily via dechlorination/hydrogenation up to temperature settings of 340 °C. In contrast, FA1 type fly ash was found to effect both dechlorination and destruction of these compounds already at temperature settings of 260 °C.

The dechlorination velocity of PCDD and PCDF did not differ significantly. However, the first dechlorination step of OCDF in the 1,9-position occurred faster compared to the first dechlorination step of OCDD.

The isomer pattern resulting from the dechlorination processes was quite similar on both FA1 and FA2, indicating that differences in alkalinity or elemental composition of the two types of fly ashes do not have a significant influence on the position of dechlorination. PCDD and PCDF dechlorination of the 2,3,7,8-positions was not favoured over dechlorination of the 1,4,6,9-positions on either type of fly ash. In contrast, dechlorination of PCB occurred predominantly on the toxicological relevant 3- and 4-positions.

The dechlorination/destruction processes were completed on both types of fly ash at 380 °C within one hour, which correlates well with results obtained from actual plant operation practices.     

Mechanism of the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from chlorophenols in gas phase reactions

The pyrolysis of chlorinated phenates at a temperature of about 280 degrees C results in the formation of definite chlorinated dibenzodioxin (PCDD) congeners [1-3]. It is shown that in gas phase reactions chlorophenols react in the presence of oxygen above 340 degrees C not only to PCDD but also to chlorinated dibenzofurans (PCDF). The mechanism of this reaction of chlorophenols to PCDD and PCDF was elucidated. In a first step phenoxyradicals are formed which are capable of forming PCDDs and PCDFs. This is confirmed by the oxygen dependency of the reaction. In an argon atmosphere no dimerization of chlorophenols could be observed at 420 degrees C. By the identification of intermediates and by analyzing the PCDF isomers formed from individual chlorophenols the reaction pathway is elucidated. As intermediates in the formation of PCDFs polychlorinated dihydroxybiphenyls (DOHB) were identified. These are most likely formed by the dimerization of two phenoxy radicals at the hydrogen substituted carbons in ortho-positions under simultaneous movement of the hydrogen atoms to the phenolic oxygen PCDDs are formed in the gas phase via ortho-phenoxyphenols (POP) analogous to the pyrolysis of phenates, but due to the radical mechanism in the first condensation step to POPs not only a chlorine atom is capable for substitution but also the hydrogen atoms. The formation of the DOHBs and their condensation to PCDFs and hydroxylated PCDFs as well as the ratio of PCDD to PCDF formed show a strong dependency on the reaction temperature, the substitution pattern of the chlorophenols and the oxygen concentration.     

A chromatophore system in the hermatypic,deep-water coral Leptoseris fragilis (Anthozoa: Hexacorallia)

Ultrastructural evidence is presented of a chromatophoresystem in the zooxanthellae containing hermatypic, deep-water coral Leptoseris fragilis (Milne Edwards and Haime). It consists of multilobed cells which mainly occupy the intercellular space of the oral gastrodermis. The cellular processes are filled with electron-dense granules up to 1-m-long and 0.5-m-wide. Within the cytoplasm an elaborate system of microtubules is established. The ramifications of the pigment cells, containing the pigment granules, form a dense and nearly continuous layer close to the overlying zooxanthellae. It is speculated that host pigments may transform the violet portion of the incident light into longer wavelengths, thus increasing the photosynthetic efficiency of the zooxanthellae.     

HERBICIDE CONTAMINATION BY THE 1993 GREAT FLOOD ALONG THE MISSISSIPPI RWER1

ABSTRACT: The Great Flood of 1993 inundated more than 355,000 ha of illinois cropland, creating great concern for the possible contamination of farmland by herbicides. The objective of this study was to assess the herbicide contamination of floodwaters and farmland due to the great flood of 1993. Floodwater samples were collected between August 5 and December 20, 1993, at the Horseshoe Lake State Game Reserve in Alexander County, Illinois, USA. Water and suspended sediment were tested separately for the more commonly used herbicides in Illinois and the midwestern USA: alachior, atrazine, and cyanazine. These herbicides were detected in the floodwater samples, but concentrations were all below the health advisory concentration of 3 μg/L established for drinking water by the United States Environmental Protection Agency. No herbicides were detected in the suspended sediment. After the recession of the flood, soil samples from flooded and non-flooded corn fields were collected for comparison. Soil samples taken from two out of three sampling locations had a 0.4 to 0.8 μg/kg increase in atrazine at the flooded verses the non-flooded sites. Concentrations were 500 to 1,000 times lower than the recommended 1 mg/kg rate at which this herbicides typically applied to soil.