Timing of eclosion in marine insects on Mediterranean shores – studies on Clunio mediterraneus, C. ponticus and Thalassomyia frauenfeldi (Diptera: Chironomidae)

In three Clunio stocks, two from the Mediterranean Sea (Banyuls, Rovinj) and one from the Black Sea (Sosopol), an identical circasemilunar eclosion pattern in combination with a circadian eclosion time of day was evoked in breeding experiments under an artificial moonlight cycle (four nights of 0.3 lux every 30 d, 12 h light:12 h dark). The eclosion peaks occurred on days with artificial moonlight and approximately 2 weeks later, and with regard to the time of day between mid-night and lights-on. In spite of the weak tidal amplitudes on Mediterranean shores, extreme low water levels occur when a nocturnal low-water time coincides on days around full and new moon (spring-tide situation) with winds from land to sea. Field observations at Banyuls and Rovinj agree with the experimental results. In contrast to Clunio spp. adults (life span only a few hours), Thalassomyia frauenfeldi adults (life span up to several days in the laboratory) demonstrated an unsynchronized eclosion pattern in the experiments (no lunar concentration, wide diurnal eclosion gate). Although inhabiting the same intertidal area, T. frauenfeldi walking on exposed intertidal substrates can delay egg-deposition for days and can probably wait for favorable low water levels. The taxonomical status of European Clunio populations is reviewed; minute morphological distinctions are presented for C. mediterraneus in the otherwise morphologically uniform, but ecophysiologically differentiated genus. Received: 15 May 1997 / Accepted: 16 June 1997     

Field test of volatilization models

Four volatilization models were tested against field data from the Manchester Ship Canal and the River Main. The equations byMacKay andYeun, using Schmidt number and wind speed for the calculation of volatilization rate, were found to give the best results for the slowly flowing Ship Canal. Models using flow velocity grossly underestimated the real values for this waterway but were found to be superior for the faster flowing River Main. The results of this work indicate that volatilization models should be carefully chosen for a particular environmental situation. Additionally, the importance of the validation of such models against field data is emphasised.     

Land Use-related Chemical Composition of Street Sediments in Beijing

BACKGROUND: More than 10 million people are currently living in Beijing. This city faces severe anthropogenic air pollution caused by an intense vehicle increase (11% per year in China), coal combusting power plants, heavy industry, huge numbers of household and restaurant cookers, and domestic heating stoves. Additionally, each year dust storms are carrying particulate matter from the deserts of Gobi and Takla Makan towards Beijing, especially in spring. Other geogenic sources of particulate matter which contribute to the air pollution are bare soils, coal heaps and construction sites occurring in and around Beijing. Streets function as receptor surfaces for atmospheric dusts. Thus, street sediments consist of particles of different chemical compositions from many different sources, such as traffic, road side soils and industry. METHODS: Distributions and concentrations of various chemical elements in street sediments were investigated along a rural-urban transect in Beijing, China. Chemical elements were determined with X-ray fluorescence analysis. Factor analysis was used to extract most important element sources contributing to particulate pollution along a main arterial route of the Chinese capital. RESULTS AND DISCUSSION: The statistical evaluation of the data by factor analysis identifies three main anthropogenic sources responsible for the contamination of Beijing street sediments. The first source is a steel factory in the western part of Beijing. From this source, Mn, Fe, and Ti were emitted into the atmosphere through chimneys and by wind from coal heaps used as the primary energy source for the factory. The second source is a combination of traffic, domestic heating and some small factories in the center of Beijing discharging Cu, Pb, Zn and Sn. Calcium and Cr characterize a third anthropogenic element source of construction materials such as concrete and mortar. Beside the anthropogenic contamination, some elements like Y, Zr, Nb, Ce, and Rb are mainly derived from natural soils and from the deserts. This is supported by mineral phase analysis, which showed a clear imprint of material in road dusts coming from the West-China deserts. CONCLUSIONS: Our results clearly show that the chemical composition of urban road dusts can be used to identify distinct sources responsible for their contamination. The study demonstrates that the chemistry of road dusts is an important monitor to assess the contamination in the urban environment. Chemical composition of street sediments in Beijing comprises the information of different sources of atmospheric particles. RECOMMENDATIONS AND OUTLOOK: This study is only a small contribution to the understanding of substance fluxes related to Beijing's dust. More effort is required to assess Beijing's dust fluxes, since the dust harms the living quality of the inhabitants. Especially the measurable superimposing of long scale transported dust from dry regions with the anthropogenic polluted urban dust makes investigations of Beijing's dust scientifically valuable.     

An object-oriented software for fate and exposure assessments

The model system CemoS¹ (Chemical Exposure Model System) was developed for the exposure prediction of hazardous chemicals released to the environment. Eight different models were implemented involving chemicals fate simulation in air, water, soil and plants after continuous or single emissions from point and diffuse sources. Scenario studies are supported by a substance and an environmental data base. All input data are checked on their plausibility. Substance and environmental process estimation functions facilitate generic model calculations. CemoS is implemented in a modular structure using object-oriented programming. e-mail: cemos@aphrodite.mathematik.uni-osnabrueck.de     

The effect of temperature on the rate of cyanide metabolism of two woody plants

The response of cyanide metabolism rates of two woody plants to changes in temperature is investigated. Detached leaves (1.0 g fresh weight) from weeping willow (Salix babylonica L.) and Chinese elder (Sambucus chinensis Lindl.) were kept in glass vessels with 100ml of aqueous solution spiked with potassium cyanide for a maximum of 28 h. Ten different temperatures were used ranging from 11 degrees C to 32 degrees C. The disappearance of aqueous cyanide was analyzed spectrophotometrically. The cyanide removal rate of Chinese elder was higher than that of weeping willow at all temperatures. The highest cyanide removal rate for Chinese elder was found at 30 degrees C with a value of 12.6 mg CN kg(-1) h(-1), whereas the highest value of the weeping willow was 9.72 mg CN kg(-1) h(-1) at 32 degrees C. The temperature coefficient values, Q10, which are the ratio of removal rates at a 10 degree difference, were determined for Chinese elder and weeping willow to 1.84 and 2.09, respectively, indicating that the cyanide removal rate of weeping willow was much more susceptible to changes in temperature than that of the Chinese elder. In conclusion, changes in temperature have a substantial influence on the removal rate of cyanide by plants.     

Metabolism of cyanide by Chinese vegetation

Cyanide is a high-volume production chemical and the most commonly used leaching reagent for gold and silver extraction. Its environmental behavior and fate is of significant concern because it is a highly toxic compound. Vascular plants possess an enzyme system that detoxifies cyanide by converting it to the amino acid asparagine. This paper presents an investigation of the potential of Chinese vegetation to degrade cyanide. Detached leaves (1.5 g fresh weight) from 28 species of 23 families were kept in glass vessel with 100 ml of aqueous solution spiked with potassium cyanide at 23.5 degrees C for 28 h. Cyanide concentrations ranged from 0.83 to 1.0 CN mg l(-1). The disappearance of cyanide from the aqueous solution was analyzed spectrophotometrically. The fastest cyanide removal was by Chinese elder, Sambucus chinensis, with a removal capacity of 8.8 mg CN kg(-1) h(-1), followed by upright hedge-parsley (Torilis japonica) with a value of 7.5 mg CN kg(-1) h(-1). The lowest removal capacity had the snow-pine tree (Credrus deodara (Roxb.) Loud). Results from this investigation indicated that a wide range of plant species is able to efficiently metabolize cyanide. Therefore, cyanide elimination with plants seems to be a feasible option for cleaning soils and water contaminated by cyanide from gold and silver mines or from other sources.     

Persistence of methyl <Emphasis Type="Italic">tertiary</Emphasis> butyl ether (MTBE) against metabolism by Danish vegetation

BACKGROUND: Methyl tertiary butyl ether (MTBE) is the second most highly produced industrial chemical in the US and a frequent groundwater pollutant. At the same time, MTBE is quite persistent to biotic and abiotic decomposition. The goal of this study was to find plant species that could degrade MTBE and might be used in phytoremediation. METHODS: Excised roots and leaves (0.3 g) from more than 24 Danish plant species out of 15 families were kept in glass vessels with 25 ml spiked aqueous solution for 2 to 4 days. MTBE concentrations were 1 to 5 mg/L. Samples were taken directly from the solution with a needle and injected to a purge and trap unit. MTBE and the main metabolite, TBA, were measured by GC/FID. RESULTS AND DISCUSSION: Solutions with roots of poplar (Populus robusta) and a willow hybrid (Salix viminalis x schwerinii) produced TBA in trace amounts, probably stemming from bacteria. Significant MTBE reduction (> 10%) was not observed in any of the tests. Leaves from none of the species (trees, grasses and herbs) reduced the concentration of MTBE in the solution and no TBA, nor any other known metabolite of MTBE, was detected. CONCLUSION: It was not possible to find plants capable of efficiently degrading MTBE. This gives rise to the conclusion that plants probably cannot degrade MTBE at all, or only very slowly. RECOMMENDATIONS AND OUTLOOK: For phytoremediation projects, this has, as consequence, that the volatilization by plants (except with genetically engineered plants) is the only relevant removal process for MTBE. For risk assessment of MTBE, degradation by the plant empire is not a relevant sink process.     

Fate of pulp mill effluent compounds in a finnish watercourse

Chloroorganic chemicals emitted from the pulp and paper mill at nekoski in central Finland were monitored for several years. Concentration time series are used for evaluating the environmental fate and the applicability and validity of an exposure models. Fitted elimination rates of 3,4,5-Tri-, 4,5,6-Tri-, Tetrachloroguaiacol and 2,4,6-Trichlorophenol are approx. 0.22 d^-1, or rather the half-lives are approx. 3 days. The elimination is most likely by biodegradation and transport-controlled. For 2,3,6-trichloro-p-cymene, fate simulations indicate significant volatilization and sedimentation. Good agreement is achieved with a one-dimensional steady-state box model, except for concentrations in fish. For a reliable assessment of environmental damage, laboratory experiments, monitoring and simulations need to be in tune.