Adjusted blank correction method for UV–vis spectroscopic analysis of PTIO-coated filters used in nitrogen oxide passive samplers

Passive sampling devices are popular in applications which do not require the monitoring of hourly concentrations. Nitrogen oxides are often collected using filters coated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). The filter extract can then be analyzed using flow injection analysis ion chromatography fitted with a copper/cadmium reduction column or UV–vis spectroscopy. When the latter is used to measure low concentrations of nitrogen oxides, absorbance by PTIO at the analytical wavelength of 545 nm contributes significantly. PTIO concentration on the filter also shows variation with filter storage and exposure time not accounted for in a single point blank subtraction at the analytical wavelength. A method is presented that uses a scaling factor to account for variations in concentration of PTIO on the field blank and provides a more accurate method for determining and correcting for the PTIO contribution to absorption when measuring ambient nitrogen oxide concentrations.     

The food-print of Paris: long-term reconstruction of the nitrogen flows imported into the city from its rural hinterland

Between the tenth and twentieth century the population of Paris city increased from a few thousand to near 10 million inhabitants. In response to the growing urban demand during this period, the agrarian systems of the surrounding rural areas tremendously increased their potential for commercial export of agricultural products, made possible by a surplus of agricultural production over local consumption by humans and livestock in these areas. Expressed in terms of nitrogen, the potential for export increased from about 60 kg N/km2/year of rural territory in the Middle Ages, to more than 5,000 kg N/km2/year from modern agriculture. As a result of the balance between urban population growth and rural productivity, the rural area required to supply Paris (i.e. its food-print) did not change substantially for several centuries, remaining at the size of the Seine watershed surrounding the city (around 60,000 km2). The theoretical estimate of the size of the supplying hinterland at the end of the eighteenth century is confirmed by the figures deduced from the analysis of the historical city toll data (octroi). During the second half of the twentieth century, the ‘food-print’ of Paris reduced in size, owing to an unprecedented increase in the potential for commercial export associated with modern agricultural systems based on chemical N fertilization. We argue that analysing the capacity of territories to satisfy the demand for nitrogen-containing food products of local or distant urban population and markets might provide new and useful insights when assessing world food resource allocation in the context of increasing population and urbanization.     

The influence of radiopharmaceutical isotope production on the global radioxenon background

Radioxenon isotopes play a major role in confirming whether or not an underground explosion was nuclear in nature. It is then of key importance to understand the sources of environmental radioxenon to be able to distinguish them from those of a nuclear explosion.     

TBT contamination of remote marine environments: ship groundings and ice-breakers as sources of organotins in the Great Barrier Reef and Antarctica

Remote marine environments such as many parts of the Great Barrier Reef (GBR) and the Antarctic are often assumed to be among the most pristine natural habitats. While distance protects them from many sources of pollution, recent studies have revealed extremely high concentrations of organotins in areas associated with shipping activities. Sediments at sites of ship groundings on the GBR have been found to contain up to 340,000 microg Sn kg(-1). Very high concentrations (up to 2290 microg Sn kg(-1)) have been detected in nearshore Antarctic sediments adjacent to channels cut through sea ice by ice-breaking vessels. In both cases, the bulk of the contamination is associated with flakes of antifouling paint abraded from vessel hulls, resulting in patchy but locally intense contamination of sediments. These particulates are likely to continue releasing organotins, rendering grounding sites and ice-breaking routes point-sources of contamination of surrounding environments. While the areas exposed to biologically-harmful concentrations of leached chemicals are likely to be limited in extent (1000-10,000 m(2)), deposition of antifouling paints constitutes a persistent ecological risk in otherwise pristine marine environments of high conservation value. The risk of contamination of GBR and Antarctic sediments by organotins needs to be considered against an important alternative risk: that less effective antifouling of ships hulls may increase the frequency of successful invasions by non-indigenous species. Additional options to minimise ecological risk include accident prevention and reducing organotin contamination from grounding sites through removal or treatment of contaminated sediments, as has been done at some sites in the GBR.     

De-novo formation of dioxins and furans and the memory effect in waste incineration flue gases

The formation of dioxin (polychlorinated-rho-dibenzodioxins - PCDD) and furan (polychlorinated dibenzofurans - PCDF) in waste incineration flyash in relation to temperature has been investigated in a bench scale reactor. The PCDD/PCDF released into the exhaust gases of the reactor and trapped in a condensation and vapour phase adsorption system were also determined. The concentrations of PCDD/PCDF in the flyash were analysed in detail for all congeners and isomers including the mono-, di- and tri-PCDD/PCDF. De-novo synthesis of PCDD/PCDF was clearly seen in the flyash with large changes in concentrations of PCDD/PCDF with only small changes in temperature. Exhaust gas PCDD/PCDF were detected at all temperatures, with the maximum emission occurring at a flyash temperature of 350 degrees C, where the equivalent of over 42 times the total dioxin/furan concentration of the original flyash was lost to the vapour phase per unit mass of initial flyash. Although the desorbed species were mainly the lower mono- to tri-congener group of dioxins and furans, the desorbed dioxin/furans had a considerable toxic equivalent value.     

Nanotechnology, risk and the environment: a review

Nanotechnologies are already interacting with the environment. Scientists and engineers are manipulating matter at the nanoscale, and these nanoscale processes and products are being used by industry in commercially available products. These products are either applied directly to the environment or end up in the environment through indirect pathways. This review examines the state of current environmental risk assessment of nanotechnologies. Nanotechnology is described generally, then both the possible benefits of nanotechnology and the risks are reviewed in a traditional way. Subsequently, a philosophical criticism of the traditional way of looking at risks is offered.