Polyzyklische aromatische Kohlenwasserstoffe aus diffusen Quellen

Goal and Scope

Polycyclic aromatic hydrocarbons (PAHs) are one group of persistent organic pollutants which are ubiquitous distributed in soils, even in rural areas. After their release into the atmosphere, transportation and deposition, they tend to accumulate in topsoils and sediments. Similar distribution pattern of PAHs in atmospheric deposition, soil samples as well as sediment samples indicate a close relationship between atmospheric input and accumulation of PAHs in the terrestrial environment. The intention of this paper was to estimate the time when precautionary values of the German law of soil protection will be exceeded in rural areas. Furthermore, current soil concentrations will be linked to the historical record of PAHs by means of enrichment factors.

Methods

The historical record of the atmospheric deposition rates of PAHs can be obtained from investigation of sediment cores. Based thereon, enrichment factors of PAHs in the environment were calculated. With these enrichment factors it was possible to estimate the recent PAH concentration in soils in rural areas from currently measured annual deposition rates. Furthermore, concentrations of PAHs in soils and deposition rates can be used to calculate the time when precautionary values will be reached.

Results and Conclusion

PAH deposition rates have been decreasing since about 1960 by a factor of 2–3, but stabilized during the last decade on a level high above pre-industrial time. Thus, further enrichment of PAH in topsoils has to be expected. Actual deposition rates in connection with historical enrichment factors allow to determine the median concentrations of PAHs in rural soils. The time when precautionary values will be reached was calculated to about 300 Years.

Outlook

The database to predict the further development of atmospheric deposition rates is very weak. There was a lack of validated methods concerning direct measurements of atmospheric POP deposition. Meanwhile, a national draft of a standard base on time-integrated passive sampling exists. This method can be implemented to establish a combined soil and deposition-monitoring program in order to assess the risk of further accumulation of POPs in soils.     

Fluctuating asymmetry and nutritional condition of Baltic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) larvae

The level of fluctuating asymmetry (FA), defined as random deviations from perfect bilateral symmetry, is assumed to reflect the developmental instability (DI) of an organism. Because environmental and genetic stress may increase DI, FA has been used to assess the level of stress experienced by, for example, fish. In this study, left–right asymmetry of lapillar otoliths was related to nutritional condition as estimated from RNA/DNA ratios, in order to investigate the utility of FA to detect feeding-related stress in Baltic cod, Gadus morhua L., larvae. Cod larvae in intermediate and good nutritional condition showed similar values of FA, and these were more symmetric than for larvae in poor condition. As increased levels of FA were restricted to larvae in a condition comparable to that of larvae experiencing at least 3 days of starvation in laboratory experiments, it is suggested that FA is an insensitive indicator of short-term feeding success of larval cod. However, FA can be used to reveal severely starved larva populations and probably also populations that have been subjected to prolonged sub-optimal feeding conditions.     

Evaluation of the validity of the US EPA's cancer risk assessment of arsenic for low-level exposures: a likelihood ratio approach

Skin cancers associated with ingesting of arsenic have been documented since the 19th century. A study in the southwestern coastal area of Taiwan where people drank well water containing arsenic is generally recognised as providing the best data available for quantifying the risk, and the US Environmental Protection Agency (EPA) used these data to conduct a risk assessment of arsenic ingestion. However, the lowest exposure category in the Taiwan study included arsenic levels up to 290 µg L^–1, which is nearly six times higher than the current EPA maximum contaminant level (MCL), 50 µg L^–1. Therefore, the EPA risk assessment model extrapolated data on high-level exposures to generate risk estimates for low-level exposures. To evaluate the validity of this model, we conducted a quantitative review of epidemiological studies observing arsenic exposures below 290 µg L^–1. A ratio of the likelihood of the EPA model being inappropriate to that of it being appropriate was calculated for each study population as a measurement of the validity of the EPA model. Although existing human data on low-level exposures are limited, the review suggested that the EPA model is unlikely to be able to predict the risk of skin cancer accurately when the arsenic exposure level is between 170 and 270 µg L^–1.     

Kin recognition by juvenile predatory mites: prior association or phenotype matching?

Kin recognition, the biased treatment of conspecific individuals based on genetic relatedness, is a widespread phenomenon in animals. The most common mechanisms mediating kin recognition are prior association (familiarity) and phenotype matching. Recognition based on prior association allows identifying familiar individuals. Recognition based on phenotype matching is an extension of prior-association-based recognition and allows identifying familiar and unfamiliar individuals due to a shared phenotypic trait. I investigated which of the two mechanisms is used by cannibalistic juvenile predatory mites, Phytoseiulus persimilis. Protonymphs that were associated with either siblings or non-kin discriminated familiar and unfamiliar larvae and preferentially cannibalized the latter irrespective of genetic relatedness. In contrast, despite previous association with either siblings or non-kin, protonymphs did not discriminate unfamiliar sibling and unfamiliar non-kin larvae. Association in the larval stage therefore mediated kin recognition based on familiarity, but not phenotype matching in cannibalistic P. persimilis protonymphs. Furthermore, in the presence of a familiar prey individual, sibling cannibalism occurred significantly sooner than non-kin cannibalism. This quick sibling cannibalism may have been the consequence of preferential association of siblings and/or may indicate the occurrence of an alternative cannibal phenotype. I discuss the adaptive significance of prior-association-based recognition for P. persimilis juveniles and emphasize the ability of P. persimilis to use multiple recognition mechanisms in dependence of the ontogeny and the ecological context.     

Effects of fly ash, Pseudomonas striata and Rhizobium on the reproduction of nematode Meloidogyne incognita and on the growth and transpiration of pea

Glasshouse experiments were conducted twice to assess the ash amendments (0, 20, and 40% with soil), a phosphate solubilizing microorganism Pseudomonas striata and a root-nodule bacterium Rhizobium sp on the reproduction of root-knot nematode Meloidogyne incognita and on the growth and transpiration of pea. Amendments of fly ash with soil had no effect on transpiration. However, M. incognita reduced the rate of transpiration from 1st week onward after inoculation while inoculation of Rhizobium sp and P. striata increased transpiration from 1st week onward after their inoculation both in nematode inoculated and uninoculated plants. Increase in transpiration was greater when both organisms were inoculated together. Addition of 20 and 40% fly ash with soil was beneficial for plant growth both in nematode inoculated and uninoculated plants. Inoculation of above organisms also increases plant growth of nematode inoculated and uninoculated plants in different fly ash soil mixture but increase in growth was greater when both organisms were inoculated together. Use of 20% fly ash increased galling and nematode multiplication over plants grown in without fly ash while 40% fly ash had adverse effect on galling and nematode multiplication. Rhizobium sp had greater adverse effect on galling and nematode multiplication than P. striata. Use of both organisms together had greater adverse effect on galling and nematode multiplication than caused by either of them alone. Highest reduction in galling and nematode multiplication was observed when both organisms were used in 40% fly ash amended soil. However, highest transpiration was observed in plants without nematodes and inoculated with both organisms together both in with or without fly ash amended soil.     

Limited evidence for increased cold-tolerance of invasive versus native <Emphasis Type="Italic">Caulerpa taxifolia</Emphasis>

Growth characteristics of native and invasive Caulerpa taxifolia from coastal eastern Australia were compared in warm (22–25°C) and cool (15–18°C) water in two laboratory experiments. Measurements of biomass, stolon length, mean frond length and numbers of fronds and stolon meristems, demonstrated that the growth of native and invasive C. taxifolia in warm water was up to ten times greater than in cool water. Growth rates differed substantially among locations over 9 weeks, but for most variables, the growth of native C. taxifolia was greater than the growth of invasive C. taxifolia in warm water. In cool water, there was little difference in growth of invasive versus native C. taxifolia. The morphology of C. taxifolia changed considerably in response to temperature, such that native and invasive samples that were morphologically distinct at the start of the experiment became indistinguishable after 69 days in warm water. We concluded there was little evidence that the C. taxifolia which recently invaded temperate estuaries in New South Wales could spread faster in cool water than could native C. taxifolia from Queensland. Native tropical C. taxifolia appears tolerant of a wide range of environmental conditions and seems capable of surviving and becoming invasive in temperate estuaries.     

Ecological impacts on the limpet Lottia gigantea populations: human pressure over a broad scale on island and mainland intertidal zones

Here long-term monitoring data taken at 33 sites in southern and central California coast and islands were used to evaluate the size structure of the large intertidal limpet, Lottia gigantea in restricted-access and in easily accessible intertidal zones that encompass a wide range of ecological variables. Using multi-dimensional analysis of population size structures, we found that sites on islands and strictly protected mainland sites have significantly larger median limpet sizes and a greater range of limpet sizes than unprotected mainland sites, while no pattern occurs in latitudinal or regional comparison of sites. Although intertidal predators such as oystercatchers were not the primary focus of the monitoring efforts, extensive natural history notes taken during sampling visits support the argument that predation was not a primary cause for the size structure differences. Finally, substratum differences were determined not to have biased the observation of larger limpets in protected sites. In regard to human interactions with limpets, we conclude that the degree of enforcement against poaching is the better predictor of limpet size structure than proximity to population centers or visitation to intertidal sites.     

Geophagy in the tropics: an appraisal of three geophagical materials

Geophagy, the deliberate consumption of soil, is a common practice amongst the world's poorer or more tribally oriented people of the tropics. An appraisal of three geophagical samples suggests that Fe is a mineral nutrient which can be supplied to humans in significant amounts via ingested soil. Geophagy provides a direct link between the geochemistry of soils and human health, but as yet this association has only a limited awareness amongst research workers.     

Conservation Implications of the Natural Loss of Lineages in Wild Mammals and Birds

Because populations in zoological parks and nature reserves often are derived from only a few individuals, conservationists have attempted to minimize founder effects by equalizing family group sizes and increasing the reproductive contributions of all individuals. Although such programs reduce potential losses of genetic diversity, information is rarely available about the actual persistence of family groups or genetic lineages in natural populations. In the absence of such data, it can be difficult to weigh the importance of human intervention in the conservation of small populations. Separate long-term studies of two mammals, the North American bison (Bison bison) and the white-nosed coati (Nasua narica), and a bird, the Acorn Woodpecker (Melanerpes formicivorus), demonstrate differential extinction of genetic lineages. Irrespective of the mechanisms affecting population structure, which may range from stochastic environmental events to such behavioral phenomena as poor intrasexual competitive abilities, our results show that lineages can be lost at rapid rates from natural populations. A survey of comparable studies from the literature indicates that the loss of matrilines over the course of the study varies from 3% to 87% in wild mammals and from 30% to 80% in birds, with several small mammals losing approximately 20% of matrilines per year of study. These lineage extinctions were not an artifact of the length of the study or the generation time of the species. Such rapid losses of lineages in less than 20-year periods in natural populations suggest that efforts to maintain maximal genetic diversity within populations may not always reflect processes that occur in the wild. Conservation biologists need to give further thought to the extent to which parity among genetic lines should be a primary goal of management of captive and small wild populations.