Dendrochemical analysis of lead and calcium in southern Appalachian American beech

The health of the northern hardwood forest in the southern Appalachian Mountains of Tennessee, North Carolina, and Virginia has gained attention from the media and environmental stakeholders due to a purported decline in forest health at higher elevations. This project examined lead (Pb) and calcium (Ca) concentrations in growth rings of an important northern hardwood species, American beech (Fagus grandifolia Ehrh.) at Mount Rogers and Whitetop Mountain, Virginia and attempted to examine concentration relationships with stem growth patterns. Dominant and codominant trees were sampled from 16 research plots at two elevations. Tree cores were crossdated, divided into sections of 10-yr periods, and analyzed using atomic absorption spectroscopy. Lead concentrations correlated negatively with ring width. Elevation and aspect were significantly associated with the Pb concentration, while Ca concentrations were only associated with aspect. Tree core samples taken from higher elevation plots contained higher Pb concentrations than samples collected from lower elevation plots, while the northwest and southwest aspects contained significantly higher amounts of Pb and Ca. Both Pb and Ca concentrations increased during the 1860s and again during the mid-1900s.     

Studies into the formation of dioxins in the sintering process used in the iron and steel industry. 1. Characterisation of isomer profiles in particulate and gaseous emissions

Dioxin analyses using a DB5MS chromatography column are presented for samples of dust from an electrostatic precipitator and emissions from the main stack of a UK sinter plant. The analyses have been repeated using the SP2331 column, for which the elution order has been determined for the whole range of tetra to octachlorodibenzo-p-dioxins and dibenzofurans, and which provides a larger degree of separation than the DB5MS column. Polychlorinated dibenzofurans are present in significantly larger amounts in both the dust and stack emissions, and are the main contributors to the I-TEQ. Analysis using the SP2331 column for dioxins show considerable similarity to those of Bacher et al. for soot from a wood-burning fire, but differ markedly from those of Addink et al. for simulation of waste incineration. The similarities to Bacher's results are less for the dibenzofurans. Comparison of absolute concentrations with reported vapour pressures shows the retention of significant dioxin in the dust to involve mechanisms other than pure condensation.     

Why Use One Model? An Approach for Encompassing Model Uncertainty and Improving Best Practice

There has been some discussion within the UK modelling community regarding the preferred choice of dispersion model for assessing the air quality impact of elevated point sources, each of which is reported to perform better than the other in certain circumstances. Coupled to this is the growing acceptance within the modelling community to include some recognition of model uncertainty in its reporting. As computer processing speeds increase further, this paper considers the possibility of using more than one model and highlights some of the advantages in doing so.     

The influence of swimming speed on sustained swimming performance of late-stage reef fish larvae

Replicate clutches of larvae were swum in a swimming flume at 4, 7, 10, 13, and 16 cm s^-1 and the time swum until exhaustion recorded. There was a significant relationship between sustained swimming time and swimming speed for both maximum (R²=0.77; P<0.05) and mean sustained swimming times (R²=0.78; P<0.05), with fish swimming at slower speeds swimming longer and covering greater total distances. The relationship observed agrees with theoretical principles relating increasing swimming speed with increasing drag. We used our data for Amphiprion melanopus, combined with published information, to predict the swimming speeds that other reef fish taxa should be able to maintain for significant lengths of time (12-48 h) using three different models. The results agree well with field estimates (R² values from 0.45 to 0.84), suggesting that there may be underlying factors influencing swimming ability in reef fish larvae that can be used to predict swimming abilities of different taxa. These models suggest that sustained swimming behaviour by reef fish larvae could have a much greater impact on modifying larval dispersal than previously thought.     

Global transport rates of Cs and Pu originating from the Nagasaki A-bomb in 1945 as determined from analysis of Canadian Arctic ice cores

Recent advancements in analytical technology make it possible for artificial radionuclides released from nuclear explosions to be detected in Arctic ice core layers. The fission product, ¹³⁷Cs, and the unexpended fission material, ^239+240Pu, originating from the Nagasaki A-bomb of August 1945, were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition rates were 0·020 mBq cm^-2 for ¹³⁷Cs and 0·0016 mBq cm^-2 for ^239+240Pu, originating from Nagasaki. Assuming the radionuclides, excluding the amount fissioned from the explosion and deposi-ted as local fallout, are deposited evenly throughout the Northern Hemisphere, 67% of the expected amount of ¹³⁷Cs reached the Arctic while 1·1% of ^239+240Pu reached the Arctic. The results suggest that different transport mechanisms exist for various contaminants in the global transport system.