Judging Survey Quality: Local Variances

The present study was undertaken to explore possibilities to judge survey quality on basis of a limited and restricted number of a-priori observations. Here, quality is defined as the ratio between survey and local variance (signal-to-noiseratio). The results indicate that the presented surveys do not permit such judgement. Furthermore, the discussion alsosuggests that the 5-fold local sampling strategies do not merit any sound judgement in about 10% of all cases.The results further imply that surveys will benefit from procedures, controls and approaches in sampling and sample handling, to assess both average, variance and the nature of the distribution of elemental concentrations in local sites. This reasoning is compatible with the idea of the site as a basic homogeneous survey unit, which is implicitly and conceptually underlying any survey performed.     

Ammonia Monitoring in Switzerland with Passive Samplers: Patterns, Determinants and Comparison with Modelled Concentrations

Gaseous ammonia (NH3) is an important form of N deposition to ecosystems, but it is not being routinely monitored in Switzerland. Therefore, a study was conducted to estimate annual means and seasonal patterns of NH3 concentrations for different site types in Switzerland, and to compare annual measured and modelled NH3 concentrations. NH3 concentrations were measured using the 'Zürcher' passive sampler, a Palmes type sampler with an acidic solution as absorbent. Twenty-four sampling sites were run for one year, and 17 for two years. The samplers were changed fortnightly or monthly. Spatial emission patterns were mapped by combining information on (1) the location of emission sources, (2) national statistics on NH3-emitting activities and (3) activity-specific emission factors. The spatial resolution was one hectare. The mean annual NH3 concentration in the ambient air of the 41 sites was 2.5+/-0.3 microg m(-3) (mean+/-standard error). It ranged from 0.4 to 7.5 microg m(-3). The site type and the season were the most important factors explaining the variation in the seasonal mean concentration. NH3 concentrations were highest in intensively used agricultural areas and in cities, and lowest in Alpine sites remote from emission sources. At 39 out of 41 sites, the NH3 concentrations were higher in summer (3.1+/-0.3 microg m(-3)) than in winter (2.0+/-0.3 microg m(-3)). Modelled NH3 concentrations did not systematically deviate from measured concentrations (r2 = 0.69). With the combined monitoring and modelling approach, it is now possible to obtain a reasonable and consolidated picture of the overall NH3 situation in Switzerland.     

Determination of VOCs in yellow eel from various inland water bodies in Flanders (Belgium)

Twenty freshwater eels caught in Flanders (Belgium) were analysed by GC-MS for a total of 52 VOCs. The most prominent VOCs are the BTEX and a number of chlorinated compounds such as chloroform and tetrachloroethene. The observed concentrations which, typically, were in the low ng/g wet weight range, could be linked to the major emission sources and the present study gives new evidence that combustion of fossil fuels is a major source of BTEX in the environment. The concentration levels in eels seem to be a reflection of the actual concentrations in their environment. For eels from the same location similar patterns and concentrations were observed, and the concentrations agree with what can be expected from those of the water column. Generally speaking, the observed concentrations do not seem to pose a threat for organisms. More definite statements will, however, require a larger dataset. The study suggests that the yellow eel can possibly be used as a biomonitor or sentinel organism for VOCs.     

Relations between sulphate,ammonia, nitrate,acidity and trace element concentrations in tree bark in The Netherlands

Bark flakes were sampled in a biomonitoring survey throughout The Netherlands. Tree species used were oak (65 samples) and non-oak (58 samples) (poplar, elm, willow). Bark elemental analysis was carried out for As, Br, Ca, Cd, Ce, Co, Cr, Cs, Fe, Hg, K, La, Na, Ni, Pb, Rb, Sb, Sc, Se, Sm, Th, and Zn. Furthermore, bark acidity, SO₄, NH₄ and NO₃ were determined. Further variables introduced into the data-set were DIST (closest distance to sea water) and the dummy variably OAK (tree species).Straightforward multivariate correlation analysis was performed to check the effects on bark metal retention of the non-metal pollutants SO₄, NH₄ and NO₃, and of bark acidity. The OAK variable served to identify species-specific metal and non-metal pollutant behaviour. The DIST variable was used to visualize geography(source)-related variations in bark metal and non-metal pollutant concentrations, and to account for the non-random distribution of OAK and non-OAK tree species.The results indicate that the non-oak and oak bark samples may be combined to form 123 samples containing data-set for As, Br, Cd, Ce, Co, Fe, La, Na, Sc, Sm, Th, Zn, NH₄, NO₄, SO₄ and acidity, but not for Rb, Cs, Se, K, Ni, Pb and Sb (species-specific) and for Ca and Hg (H⁺-dependent). In the presented data-set, bark sulphate, ammonia and nitrate could not be shown to significantly affect bark metal retention.     

The evolution of leks through female choice: differential clustering and space utilization in six sympatric manakins

Summary The degree to which lekking and non-lekking male manakins select display sites in order to maximise proximity to females was examined by contrasting movements of females with male dispersion. Data on female visiting patterns, male courtship disruption, and mating skew were also collected over three successive breeding seasons. For the five lek-breeding species, female home-ranges were 3–7 times larger than those of adult males. Female movements were concentrated around leks, fruiting places and stream bathing sites. None of the females monitored by radio-tracking expanded her normal range in order to visit males on leks. On the contrary, feeding bouts of females frequently preceded a visit to potential mates at neighboring leks. Despite small sample sizes, significant correlations were found between female home-range size and male clustering (distances between neighboring leks and distances between neighboring males), as predicted by the female choice model and the hotspot model. Adult and immature male home-range sizes were not significantly correlated with male dispersion or female ranges. On the other hand, males and females of the only non-lekking species exhibited similar use of space and home-range size. Male settlement at sites with high levels of female traffic showed that the hotspot model is adequate to explain differences in male dispersion among sympatric lekking species. Comparisons with other studies suggest that apparent female choice could be overidden by past and present male-male interactions or female mate-comparison tactics. In fact, both the hotspot model and the attractiveness hypothesis appear to shape male dispersion on leks: males appear to settle under hotspot conditions with despotic rules generated through bias in female choice or male-male interference. It is proposed that the evolution of leks is ecologically motivated by the spatio-temporal distribution of trophic resources, initially leading to a dispersed male-advertisement polygyny. Following this, a foraging ecology that promotes high mobility by females and the magnetic effect of mating skew in particular males may have favored clustering on exploded leks. Later, the development of male-male interference and the increasing female home-range size could have led to the evolution of classical leks.     

The metabolism of 4,4′-dichlorobiphenyl in rats and frogs

The metabolism of 4,4′-dichlorobiphenyl in the rat has been investigated in detail and four monohydroxy-, four dihydroxy- and two trihydroxy metabolites were detected. The structures of the metabolites - except for the trihydroxy compounds - were ascertained by GC-MS studies and by comparison with synthetic compounds. Metabolism experiments in frog resulted in the isolation and characterisation of four metabolites. The structure of the major metabolites in both the rat and the frog are consistent with epoxidation of the biphenyl nucleus followed by epoxide ring opening accompanied by a 1,2-chlorine shift (NIH-shift). The formation of one minor rat metabolite, 4-chloro-3t́-biphenylol can only be explained by reductive dechlorination.     

2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.     

NaU2Cl6, a reduced metallic chloride of uranium

This work has been supported by a NATO Research Grant and by the Fonds der Chemischen Industrie.     

Early prenatal diagnosis of genetic microcephaly

We report a new case of prenatal diagnosis of recessive microcephaly by ultrasound examination allowing termination of pregnancy at 25 weeks gestation.