Possible causes of temporal fluctuations in primary production of the microphytobenthos in the Danish Wadden Sea

The effects of prior exposure to unlabelled naphthalene on the processes of uptake, tissue distribution and elimination of [1-¹⁴C] naphthalene by mussels (Mytilus edulis) were examined. Mussels collected from Whitsand Bay (S. W. England) in October 1980 were either held unexposed or exposed to unlabelled naphthalene (0.5 μg 1^?1) for 4 wk, prior to receiving a 4 h pulse of [1-¹⁴C] naphthalene in the medium (7 μg 1^?1). After 4 h exposure to [1-¹⁴C] naphthalene, the major tissues (digestive gland, gills, kidneys, mantle and remaining tissue) showed exponential depuration curves which could be resolved into two statistically significant components. The kinetics of elimination and the biological half-times of [1-¹⁴C] naphthalene in the tissues were determined. Mussels pre-exposed to unlabelled naphthalene had a significantly higher rate of elimination of [1-¹⁴C] naphthalene from the gills and kidneys. These results indicate that the toxicant, naphthalene, is actively excreted from the body by the gills and kidneys and the process is enhanced by prior exposure to the toxicant.     

Recognition of individual-specific marked parasitized hosts by the solitary parasitoid Epidinocarsis lopezi

Summary In parasitoid wasps, self-superparasitism (oviposition into a host already parasitized by the female herself) often contributes less to the reproductive success of the parasitoid than oviposition into a host previously parasitized by a conspecific (conspecific superparasitism). It could therefore often be profitable for parasitoids to avoid self-superparasitism. This requires a mechanism for either (1) the avoidance of previously searched areas and/or (2) the rejection of hosts containing eggs laid by the searching female. We investigated whether the solitary parasitoid Epidinocarsis lopezi is able to avoid self-superparasitism. We show that visits to previously searched patches were shorter than visits to unsearched patches and conclude that E. lopezi females leave a trail odour on patches they have searched. No differences were found between the time on patches previously searched by the wasp itself and on patches visited by conspecifics. However, E. lopezi superparasitizes fewer hosts previously parasitized by itself than hosts parasitized by a conspecific. Thus, they recognize an individual-specific mark in or on the host. We discuss how patch marking and host marking enable E. lopezi to avoid self-superparasitism.     

Aufnahme von chlorierten Kohlenwasserstoffen durch Pflanzenoberflächen

Spinach plants were contaminated with hexachlorobenzene (HCB) and 2,2′, 5,5′-tetrachlorobiphenyl (PCB) in the vapor phase and by bentonite aerosol. To characterize the deposition of these substances on contaminated plant leaves, different solvents were used (water,n-hexane, and acetone). The solubility of the substances was shown to depend on the mode of application. Release studies indicate that the concentration of the tested chemicals decreases to 5% for HCB and to 27%, respectively 49%, for PCB after a period of 4 days at 23°C for different modes of contamination.     

Methylchloroform: Global distribution,seasonal cycles,and anthropogenic chlorine

It is evident that the global concentrations of methylchloroform (CH₃CCl₃) are increasing although at much lower rates than in the past. The ratio of concentrations in the two hemispheres has varied and is now declining, which reflects the constancy of the industrial emissions over the past 5 years. Observations show that the mid-latitude concentrations in both hemispheres are slightly lower during the summer than at other times, probably reflecting the greater removal of CH₃CCl₃ by OH radicals during summer. Calculations show that the lifetime of CH₃CCl₃ is about 6 (±1.5) years, which is considerably shorter than many previous estimates. It implies that there are probably 8 × 10⁵ molecules of OH/cm₃ of air, although this estimate may be uncertain by ±75%. The shorter lifetime is partly due to a revision of the estimated absolute concentration of CH₃CCl₃ in the atmosphere, which was found to be about 20% less than estimated previously. The relatively short lifetime suggests that in the future CH₃CCl₃ will contribute <15% of the anthropogenic chlorine in the troposphere, which is an approximate measure of its relative contribution to the depletion of the stratospheric ozone layer.     

Effect of fuel properties on mutagenic activity in extracts of heavy-duty diesel exhaust particulate.

The effect of varying fuel properties on the emission of mutagenic materials was studied in diesel exhaust particles from a heavy duty engine run under transient speed and load conditions while using nine fuels varying in aromatics, sulfur and boiling point. Mutagenic activity of the soluble organic fraction (SOF) of the particulate was determined using the Ames Salmonella test system with strain TA98 with and without S9 activation. Increasing mutagenic activity relative to fuel consumed (mutants/lb fuel) or to engine work output (mutants/hp-h) was correlated with increasing fuel aromatics (p less than 0.05), but not with fuel sulfur. Increased fuel sulfur levels were correlated with increased amounts of SOF but with decreasing mutagenic activity of the SOF (mutants/microgram SOF) (p less than 0.05). As a result, mutants/hp-h were essentially the same for high- and low-sulfur fuels with high aromatics. No association was found between the fuels' boiling points and the mutagenic activity of the SOF. Mutagenic activity with S9 was generally lower than without, but the correlations were not changed.     

Concentrations and distribution of 3,3'-dichlorobenzidine and its congeners in environmental samples from Lake Macatawa

Release of 3,3'-dichlorobenzidine (DCB), an intermediate in dye manufacturing processes, is of environmental concern due to its carcinogenic nature. An 11-year field study has been conducted to elucidate the fate and behavior of DCB and its congeners in the Lake Macatawa (Holland, MI, USA) sediment-water system. The sediments were variable in composition, ranging from sandy sediments with 1-8.7% total organic carbon (OC) to silty-clay sediments with 7.5-20.6% total OC. The pH ranged from 6.3 to 7.4. The findings from this field study confirmed that DCB and its congener, benzidine, are transported over long distances. The concentration of DCB in the water phase was found to be from non-detectable to approximately 1300 times greater than the water quality criteria established for DCB (0.021 microg/l). Its congener, benzidine, which is substantially more toxic for humans than its parent compound has been found up to approximately 12300 times higher levels than the EPA guidelines suggest (0.000086 microg/l). Both DCB and benzidine were found in the sediment phase. DCB was observed at almost 70 mg/kg in a sample collected in 1993. The concentrations in both phases have declined in recent years. To assess the threat of the released pollutants, it is necessary to understand how pollutants tend to behave in various media. Therefore, it is crucial to identify and quantify all sources of the chemical and its congeners in order to meaningfully predict the fate (and transport) of a hydrophobic organic compound (HOC) in the environment.     

DIOXIN 2004

Ohne Zusammenfassung     

The Water Framework Directive: stakeholder preferences and catchment management strategies--are they reconcilable?

The key objective of the European Water Framework Directive (WFD) is to promote sustainable water use by protecting water resources. Here, we investigate how the economic consequences of a set of water management regulations is received by a group of stakeholders in the R?nne? catchment. We explore three themes from an economic point of view: i) perceived causes of eutrophication, ii) preferences regarding water use, and iii) the extent to which the polluter-pays principle should be applied. There is a common understanding about the intentions in the WFD to enhance cost-effective water use. All stakeholder groups largely share a similar picture of the causes of water quality deterioration. However, there is not one cost-effective and fair solution. Several mixes of remedial measures within the same catchment are possible, depending on the scale of action. Despite potential economic gains from cooperation between sectors, the participants regard the individual polluter-pays principle as the most feasible mode of funding for remedial programs, supported by subsidies. There is little demand for more market institutions (emission fees, tradable emission permits). The stakeholders have a conservative view of water management, i.e. they accept the present combination of regulations and economic incentives, and they are fully aware of the complexity of the issue. In general, the WFD recommendations for the calculation of cost-effective abatement strategies seem to imply an underestimation of the value of external effects in the decision-making process.     

Occurrence of UV filter compounds from sunscreens in surface waters: regional mass balance in two Swiss lakes

Consumer care products often contain UV filters, organic compounds which absorb ultraviolet light. These compounds may enter surface waters directly (when released from the skin during swimming and bathing) or indirectly via wastewater treatment plants (when released during showering or washed from textiles). Predicted and measured UV filter concentrations were compared in a regional mass balance study for two Swiss lakes: Lake Zurich, a typical midland lake which is also an important drinking water resource, and Hüttnersee, a small bathing lake. Both lakes are extensively used for recreational activities and considerable direct input of UV filters is thus expected. This input was estimated from the number of visitors at swimming areas around the lakes and a survey of the usage of sunscreen products among these visitors. Possible additional indirect input via wastewater treatment plants was not considered in this study. The quantitatively most important UV filters, as indicated by the survey data, ethylhexyl methoxycinnamate, octocrylene, 4-methylbenzylidene camphor, butyl methoxydibenzoylmethane, and benzophenone-3, all lipophilic compounds, were selected for analysis by gas chromatography-mass spectrometry. Concentrations of individual UV filters in water from Lake Zurich were low, ranging from <2 ng l(-1) (detection limit) to 29 ng l(-1), and somewhat higher at Hüttnersee, ranging from <2 to 125 ng l(-1), with the highest concentrations found in summer, consistent with direct inputs to the lakes during this time. The concentrations were clearly lower than predicted from input estimates based on the surveys. This may be in part due to (i) an overestimation of these inputs (e.g. less than the 50% wash-off of UV filters assumed to occur during swimming), and (ii) some removal of these compounds from the lakes by degradation and/or sorption/sedimentation. UV filters were also detected in semipermeable membrane devices (SPMDs) deployed at Lake Zurich and Greifensee, another midland lake, at concentrations of 80-950 ng SPMD(-1), confirming the presence of the compounds in surface waters and indicating a certain potential for bioaccumulation. SPMD-derived water concentrations were in the range of 1-10 ng l(-1) and thus corresponded well with those determined in water directly. No UV filters were detected above blank levels in SPMDs deployed at a remote mountain lake used for background measurements.