A new method to assess mercury emissions: a study of three coal-fired electric-generating power station configurations

U.S. Environmental Protection Agency (EPA) Method 7473 for the analysis of mercury (Hg) by thermal decomposition, amalgamation, and atomic absorption spectroscopy has proved successful for use in Hg assessment at coal-fired power stations. In an analysis time of approximately 5 min per sample, this instrumental methodology can directly analyze total Hg--with no discrete sample preparation--in the solid matrices associated with a coal-fired power plant, including coal, fly ash, bottom ash, and flue gas desulfurization (FGD) material. This analysis technique was used to investigate Hg capture by coal combustion byproducts (CCBs) in three different coal-fired power plant configurations. Hg capture and associated emissions were estimated by partial mass balance. The station equipped with an FGD system demonstrated 68% capture on FGD material and an emissions estimate of 18% (11 kg/yr) of total Hg input. The power plant equipped with low oxides of nitrogen burners and an electrostatic precipitator (ESP) retained 43% on the fly ash and emitted 57% (51 kg/yr). The station equipped with conventional burners and an ESP retained less than 1% on the fly ash, emitting an estimated 99% (88 kg/yr) of Hg. Estimated Hg emissions demonstrate good agreement with EPA data for the power stations investigated.     

Assessing Changes in Phosphorus Concentrations in Relation to In-Stream Plant Ecology in Lowland Permeable Catchments: Bringing Ecosystem Functioning Into Water Quality Monitoring

Changes in concentrations of soluble reactive phosphorus (SRP), excess partial pressure of carbon dioxide (EpCO₂), and chlorophyll-a were examined for two rivers in the in the upper Thames catchment: the main river Thames at Wallingford and a chalk stream tributary, the River Kennet. Sampling began in the spring of 1997 and has covered extremes in river flow conditions. During the sampling period there was a dramatic reduction in phosphorus (P) inputs from the introduction of effluent P-treatment at sewage treatment works, as a result of the EU Urban Wastewater Treatment Directive. Despite major reductions in baseflow SRP concentrations in the River Kennet, from around 700 μg-P L^-1 to around 100 μg-P L^-1, observations of aquatic plant communities indicate overall degradation in ecological quality since effluent P-treatment was introduced. The degradation was associated with a spring and summer decline in growth of Ranunculus, a macrophyte of high conservation value in chalk streams, particularly from 2000 onwards, linked to shading by epiphytic algae. Although the EpCO₂ records indicate a reduction in primary productivity since effluent P-treatment, the River Kennet may have become more sensitive to epiphyte blooms. Episodes of epiphyte proliferation appear to be linked temporally to small increases in SRP concentrations (typicallyabove a 100 μg-P L^-1 threshold) under summer baseflow conditions. The in-stream system is highly complex and individual processes and causality are difficult to resolve, particularly given changes in river flows linked to background climatic variability and limited availability of biological data. This study demonstrates the need for integrated long-term biological and chemical monitoring of river systems subject to major perturbations to assess timescales required to produce new dynamic equilibria in ecosystem response.     

Growth conditions affect carotenoid-based plumage coloration of great tit nestlings

 Carotenoid-based integument colour in animals has been hypothesised to signal individual phenotypic quality because it reliably reflects either foraging efficiency or health status. We investigated whether carotenoid-derived yellow plumage coloration of fledgling great tits (Parus major) reflects their nestling history. Great tit fledglings reared in a poor year (1998) or in the urban habitat were less yellow than these reared in a good year (1999) or in the forest. The origin of nestlings also affected their coloration since nestlings from a city population did not improve their coloration when transferred to the forest. Brood size manipulation affected fledgling colour, but only in the rural population, where nestlings from reduced broods developed more yellow coloration than nestlings from increased and control broods. Effect of brood size manipulation on fledgling plumage colour was independent of the body mass, indicating that growth environment affects fledgling body mass and plumage colour by different pathways. Received: 20 March 2000 / Accepted in revised form: 4 September 2000     

Biology of the basket star <Emphasis Type="Italic">Gorgonocephalus caputmedusae</Emphasis> (L.)

Ophiurid basket stars belonging to the family Gorgonocephalidae are distributed from the Arctic to the Antarctic and from the shallow subtidal to the deep sea, but their biology remains poorly known. In situ observations at the mouth of the Oslofjord by a remotely operated vehicle showed that Gorgonocephalus caputmedusae had a patchy distribution at 85 to 120 m water depth and frequently occurred in association with the gorgonian Paramuricea placomus and the coral Lophelia pertusa. Morphological and histological studies show that G. caputmedusae is well adapted to capture macroplanktonic prey. Histological examination of the arms revealed the presence of a thick layer of dermal mutable connective tissue which is probably an energy-efficient way to maintain its feeding posture against the current. This layer is connected to the nerve cord suggesting that the passive mechanical properties (stiffness) is controlled by the nervous system. In the distal parts of the arms, each segment has a pair of sticky tube feet and a sophisticated system of spines and hooks, which are connected to muscles and collagenous tendons. In combination, these features were shown, in an experimental flume study, to be used for capturing the locally abundant krill species Meganyctiphanes norvegica. This is the first documentation of G. caputmedusae of this kind.     

Antenatal corticosteroids and outcomes in gastroschisis: A multicenter retrospective cohort study

Objective

In gastroschisis, there is evidence to suggest that gut dysfunction develops secondary to bowel inflammation; we aimed to evaluate the effect of maternal antenatal corticosteroids administered for obstetric reasons on time to full enteral feeds in a multicenter cohort study of gastroschisis infants.

Methods

A three center, retrospective cohort study (1992-2013) with linked fetal/neonatal gastroschisis data was conducted. The primary outcome measure was time to full enteral feeds (a surrogate measure for bowel function) and secondary outcome measure was length of hospital stay. Analysis included Mann-Whitney and Cox regression.

Results

Of 500 patients included in the study, 69 (GA at birth 34 [25-38] weeks) received antenatal corticosteroids and 431 (GA at birth 37 [31-41] weeks) did not. Antenatal corticosteroids had no effect on the rate of reaching full feeds (Hazard ratio HR 1.0 [95% CI: 0.8-1.4]). However, complex gastroschisis (HR 0.3 [95% CI: 0.2-0.4]) was associated with an increased time to reach full feeds and later GA at birth (HR 1.1 per week increase in GA [95% CI: 1.1-1.2]) was associated with a decreased time to reach full feeds.

Conclusion

Maternal antenatal corticosteroids use, under current antenatal steroid protocols, in gastroschisis is not associated with an improvement in neonatal outcomes such as time to full enteral feeds or length of hospital stay.     

The ecological niche of Daphnia magna characterized using population growth rate

The concept of an organism's niche is central to ecological theory, but an operational definition is needed that allows both its experimental delineation and interpretation of field distributions of the species. Here we use population growth rate (hereafter, pgr) to define the niche as the set of points in niche space where pgr > 0. If there are just two axes to the niche space, their relationship to pgr can be pictured as a contour map in which pgr varies along the axes in the same way that the height of land above sea level varies with latitude and longitude. In laboratory experiments we measured the pgr of Daphnia magna over a grid of values of pH and Ca2+, and so defined its "laboratory niche" in pH-Ca2+ space. The position of the laboratory niche boundary suggests that population persistence is only possible above 0.5 mg Ca2+/L and between pH 5.75 and pH 9, though more Ca2+ is needed at lower pH values. To see how well the measured niche predicts the field distribution of D. magna, we examined relevant field data from 422 sites in England and Wales. Of the 58 colonized water bodies, 56 lay within the laboratory niche. Very few of the sites near the niche boundary were colonized, probably because pgr there is so low that populations are vulnerable to extinction by other factors. Our study shows how the niche can be quantified and used to predict field distributions successfully.     

Ecological differences and coexistence in a guild of microparasites: Bartonella in wild rodents

The study of ecological differences among coexisting microparasites has been largely neglected, but it addresses important and unusual issues because there is no clear distinction in such cases between conventional (resource) and apparent competition. Here patterns in the population dynamics are examined for four species of Bartonella (bacterial parasites) coexisting in two wild rodent hosts, bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus). Using generalized linear modeling and mixed effects models, we examine, for these four species, seasonal patterns and dependencies on host density (both direct and delayed) and, having accounted for these, any differences in prevalence between the two hosts. Whereas previous studies had failed to uncover species differences, here all four were different. Two, B. doshiae and B. taylorii, were more prevalent in wood mice, and one, B. birtlesii, was more prevalent in bank voles. B. birtlesii, B. grahamii, and B. taylorii peaked in prevalence in the fall, whereas B. doshiae peaked in spring. For B. birtlesii in bank voles, density dependence was direct, but for B. taylorii in wood mice density dependence was delayed. B. birtlesii prevalence in wood mice was related to bank vole density. The implications of these differences for species coexistence are discussed.     

Consequences of resource competition for sex allocation and discriminative behaviors in a hyperparasitoid wasp

Population-wide mating patterns can select for equal parental investment in both sexes, but limiting resources, such as mates or developmental substrates, can increase competition leading to biased sex ratios in favor of either sex. Such competition for resources typically occurs in spatially structured populations, where dispersal is limited. In this laboratory study, we investigate if and how resource competition affects sex allocation, discriminative behaviors and competitive interactions of the wingless hyperparasitoid Gelis acororum, which exploits patchily distributed hosts. We show that G. acororum sex ratios are male-biased and that this is not a consequence of constrained reproduction by virgin females. Our results suggest that this pattern of reproductive investment, which is only rarely observed in parasitoids, is a consequence of resource limitation, in terms of hosts rather than mates. Further, G. acororum appears not to respond to intrinsic host quality or to prior oviposition in its host. When competing inter-specifically for host resources, G. acororum outcompetes its congener Gelis agilis, but does so mainly when ovipositing on the host first. Overall, our results suggest that host resource limitation could be an important environmental factor shaping sex allocation in G. acororum, with competition taking place both intra- and inter-specifically.