The Rossby Centre Regional Atmospheric Climate Model part II: application to the Arctic climate

The Rossby Centre regional climate model (RCA2) has been integrated over the Arctic Ocean as part of the international ARCMIP project. Results have been compared to observations derived from the SHEBA data set. The standard RCA2 model overpredicts cloud cover and downwelling longwave radiation, during the Arctic winter. This error was improved by introducing a new cloud parameterization, which significantly improves the annual cycle of cloud cover. Compensating biases between clear sky downwelling longwave radiation and longwave radiation emitted from cloud base were identified. Modifications have been introduced to the model radiation scheme that more accurately treat solar radiation interaction with ice crystals. This leads to a more realistic representation of cloud-solar radiation interaction. The clear sky portion of the model radiation code transmits too much solar radiation through the atmosphere, producing a positive bias at the top of the frequent boundary layer clouds. A realistic treatment of the temporally evolving albedo, of both sea-ice and snow, appears crucial for an accurate simulation of the net surface energy budget. Likewise, inclusion of a prognostic snow-surface temperature seems necessary, to accurately simulate near-surface thermodynamic processes in the Arctic.     

Influence of kinetic sorption and diffusion on pesticide movement through aggregated soils

Laboratory studies were carried out to investigate solute leaching at different times from application in relation to temperature and initial soil moisture. Aggregates of a heavy clay soil were treated with a non-interactive solute (bromide) and the herbicides chlorotoluron, isoproturon and triasulfuron. The soil was incubated at 90% field capacity and either 5 or 15 degrees C. The influence of application to initially dry and initially wet aggregates on the behaviour of isoproturon was also investigated. At intervals, samples were either leached in small columns, centrifuged to characterise the fraction of chemical available in pore water under natural moisture conditions or extracted with organic solvents to assess total residues in soil. Bromide concentrations in leachate and in pore water extracted by centrifugation were constant with time. In contrast, availability for leaching and concentration in pore water of the herbicides decreased with increasing time from application in soil incubated at 15 degrees C. The effect of residence time was much smaller at 5 than at 15 degrees C. At the higher temperature, pesticide concentrations in leachate and pore water declined faster than would be expected from degradation alone, probably due to slow diffusion of the pesticides into soil aggregates where they are less available for leaching and/or slow sorption-desorption. The faster decline in availability for leaching at 15 than at 5 degrees C was attributed to faster degradation of the readily available fraction. There was no significant influence of initial soil moisture on either the leaching behaviour of isoproturon or its availability in soil water.     

PCB and PAH releases from power stations and waste incineration processes in the UK

This study focused on emissions of polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) from incineration and power generation processes. Increased concern over human exposure to both classes of compounds has meant that environmental regulators need to assess the contribution made by emissions from regulated processes to human exposure. In the first part of an assessment in the UK we reviewed literature data on emissions of PCB, focusing on the dioxin-like PCB assigned toxic equivalency factors by the World Health Organization, and PAH. The literature study was supplemented by a series of plant tests to gather initial real plant data. Literature data were limited and the lack of standard protocols for measurement and reporting of both PCB and PAH meant that few data sets were comparable. Levels of dioxin-like PCB reported in the literature and measured in UK plant tests showed that well-controlled modem combustion plants with comprehensive pollution controls gave low emissions, typically about 5-10% of the toxic equivalent of the emissions of polychlorinated dibenzodioxins and dibenzofurans at the same plants and below the widely used standard of 0.1 ng TEQ/N m3.     

Comparative toxicity of a zinc salt, zinc powder and zinc oxide to Eisenia fetida, Enchytraeus albidus and Folsomia candida

The pore water zinc concentration and the calcium chloride extracted zinc fraction are higher in the soils spiked with a zinc salt (ZnCl2) compared to soils spiked with zinc oxide or zinc powder. Based on total zinc concentrations in the soil, the acute toxicity of zinc salt to the compost worm Eisenia fetida, the potworm Enchytraeus albidus and the springtail Folsomia candida was lower compared to zinc oxide and zinc powder. However, when expressed on the basis of pore water concentrations or calcium chloride extracted fractions, acute toxicity was higher for zinc salt, which indicated that dermal uptake via the pore water is not the only route of uptake. Chronic toxicity of zinc salt, zinc oxide and zinc powder was similar when based on total concentrations in the soil which again indicates that the pore water route of uptake is not the only route of exposure but that oral uptake is also important.     

Evaluation of approaches for terrestrial hazard classification

Hazard assessment is an essential element in the evaluation of the potential effects of chemical substances on the environment. To date, most work has focused on hazard assessment schemes for the aquatic environment, but in recent years, a number of proposals have been developed for other environmental compartments. Due to limited datasets, the suitability of the toxicity cut-off values in these schemes has not been fully determined and the practicalities associated with using these approaches have not been fully established. This study, which focused on the soil compartment, was performed to examine cut-off values proposed by two terrestrial hazard assessment schemes and establish the availability of data. Data on earthworms indicated that current proposals for toxicity cut-off values are appropriate. However, analysis of IUCLID (International Uniform ChemicaL Information Database) indicates that even for commonly used high production volume chemicals, insufficient data are available to enable classification. Whilst the necessary data may already be available for selected groups of substances (e.g. pesticides and veterinary medicines), a significant experimental testing programme would therefore be required before a terrestrial classification system could be applied widely. Such data may become available in the future as a result of initiatives such as REACH.     

Tolerance and acclimation to zinc of Ceriodaphnia dubia

Zinc is an essential metal for all living organisms. However, so far, little or no attention has been paid to the consequences of zinc deficiency or acclimation to this metal during culturing and testing on toxicity test results. In this study, the cladoceran Ceriodaphnia dubia was acclimated for 10 generations to four zinc concentrations ranging from 0 to 100 microg Zn/l and changes in zinc tolerance were monitored using acute (48 h) and chronic (9 days) assays. C. dubia deprived of zinc and acclimated to 13 microg Zn/l had a lower fitness in comparison with organisms acclimated to 50 and 100 microg Zn/l. In the two lowest versus the two highest acclimation concentrations the 9dEC50 values (on immobility) were 358-387 microg Zn/l versus 486-489 microg Zn/l; the mean number of young per female was 11-18 versus 25-32; and the time to first brood was 4.7-5.0 days versus 4.0-4.3 days. Moreover, the coefficient of variation of all parameters tested was highest in the two lowest acclimation concentrations. The results indicate that culturing test animals in media lacking trace metals such as zinc could give rise to animals that are unnaturally sensitive to those same metals daring toxicity tests.     

The contribution from shipping emissions to air quality and acid deposition in Europe

A global three-dimensional Lagrangian chemistry-transport model STOCHEM is used to describe the European regional acid deposition and ozone air quality impacts along the Atlantic Ocean seaboard of Europe, from the SO2, NOx, VOCs and CO emissions from international shipping under conditions appropriate to the year 2000. Model-derived total sulfur deposition from international shipping reaches over 200 mg S m(-2) yr(-1) over the southwestern approaches to the British Isles and Brittany. The contribution from international shipping to surface ozone concentrations during the summertime, peaks at about 6 ppb over Ireland, Brittany and Portugal. Shipping emissions act as an external influence on acid deposition and ozone air quality within Europe and may require control actions in the future if strict deposition and air quality targets are to be met.     

Flame retardants, surfactants and organotins in sediment and mysid shrimp of the Scheldt estuary (The Netherlands)

Sediment and mysids from the Scheldt estuary, one of the largest and most polluted estuaries in Western Europe, were analyzed for a number of contaminants that have been shown to possess endocrine-disrupting activity, i.e. organotins, polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), nonylphenol ethoxylates (NPE) and transformation products, nonylphenol (NP) and nonylphenol ether carboxylates (NPEC). In addition, in vitro estrogenic and androgenic potencies of water and sediment extracts were determined. Total organotin concentrations ranged from 84 to 348 ng/g dw in sediment and 1110 to 1370 ng/g dw in mysid. Total PBDE (excluding BDE-209) concentrations ranged from 14 to 22 ng/g dw in sediment and from 1765 to 2962 ng/g lipid in mysid. High concentrations of BDE-209 (240-1650 ng/g dw) were detected in sediment and mysid (269-600 ng/g lipid). Total HBCD concentrations in sediment and mysid were 14-71 ng/g dw and 562-727 ng/g lipid, respectively. Total NPE concentrations in sediment were 1422 ng/g dw, 1222 ng/g dw for NP and 80 ng/g dw for NPEC and ranged from 430 to 1119 ng/g dw for total NPE and from 206 to 435 ng/g dw for NP in mysid. Significant estrogenic potency, as analyzed using the yeast estrogen assay, was detected in sediment and water samples from the Scheldt estuary, but no androgenic activity was found. This study is the first to report high levels of endocrine disruptors in estuarine mysids.     

High genetic diversities and complex genetic structure in an Indo-Pacific tropical reef fish (Chlorurus sordidus): evidence of an unstable evolutionary past?

Historical sea level fluctuations have influenced the genetic structure and evolutionary history of marine species and examining widespread species across their species ranges may elucidate some of these effects. Chlorurus sordidus is a common and widespread parrotfish found on coral reefs throughout the Indo-central Pacific. We used phylogenetic, phylogeographic, and cladistic analyses to examine the genetic composition and population structure of this species across most of its latitudinal range limits. We sequenced 354 bp of the mitochondrial control region I in 185 individuals from nine populations. Populations of C. sordidus displayed high levels of genetic diversity, similar to those recorded for widespread pelagic fish species, but much greater nucleotide diversity values than those previously recorded for other demersal reef fishes. Both phylogenetic and phylogeographic analyses detected strong genetic subdivision at the largest spatial scale (i.e. among oceans). The Pacific Ocean was characterised by weak population genetic structure. Separation of the Hawaiian location from other Pacific and West Indian Ocean sites was evident in phylogenetic analyses, but not from analysis of molecular variance. NCA and isolation-by-distance tests suggested that the genetic structure of this species was the result of multiple contemporary and historical processes, including long-distance colonisation and range expansion arising from fluctuating sea levels, limited current gene flow, and isolation by distance. This pattern is to be expected when historically fragmented populations come into secondary contact. We suggest the patterns of population genetic structure recorded in C. sordidus are caused by large local population sizes, high gene flow, and a recent history of repeated fragmentation and remixing of populations resulting from fluctuating sea levels.Communicated by M.S. Johnson, Crawley     

Extra-pair paternity in tree swallows: why do females mate with more than one male?

Recent studies of monogamous tree swallows (Tachycineta bicolor) suggest that females may receive some type of genetic benefit from extra-pair fertilizations. In this study we attempted to determine what type of genetic benefits might be gained by females. We compared numerous morphological and behavioral traits (Table 1) of every male nesting on one grid of nest-boxes (n = 23) to determine what male traits were correlated with male success at gaining extra-pair fertilizations. DNA fingerprinting revealed an increase in the level of extra-pair paternity from the previous year (50% of broods contained extra-pair young in 1990 vs. 87% of broods in 1991), but no significant correlates of paternity. We found six extra-pair fathers at seven nests (20 nests had extra-pair young). The traits of these extra-pair males did not differ from those of the males they cuckolded. We discuss several reasons for this lack of difference, but argue that our results are not inconsistent with females choosing extra-pair males to enhance the genotypic quality of their offspring. Despite a complete search of the nest-box grid for extra-pair fathers, we were able to explain the paternity of just 21% (13/63) of all extra-pair young. This suggests that extra-pair fathers were either residents off our study grid or non-territorial floaters. Tree swallows are quite mobile and spend only part of the day at their nest prior to laying. In addition, we rarely see swallows visiting other grids of nest-boxes. Therefore, we suggest that most extra-pair copulations occur at some unknown location, possibly at a feeding or roosting area where females may be able to choose from many more potential extra-pair fathers than at their nest-site.