130 research outputs found
Measurement of particulate matter: recommendations for the VERA test protocol on air cleaning technologies
Negligible influence of livestock contaminants and sampling system on ammonia measurements with cavity ring-down spectroscopy
Emission of ammonia (NH3) is a ubiquitous problem
due to the adverse effects of NH3 on the environment and human
health. The agricultural sector accounts for nearly all NH3
emissions in Europe. Hence, technologies for the abatement of NH3
emissions from this sector have been in strong demand in recent years. In
order to document emissions and evaluate abatement technologies, there is
a strong need for reliable NH3 measurement methods. Photoacoustic
spectroscopy (PAS) is often used to measure NH3 concentrations, but
recent research shows interference from compounds typically present in
livestock production and during agricultural activities. In this work, the
performance of cavity ring-down spectroscopy (CRDS) from Picarro, as an
alternative to PAS, has been tested with respect to method validation under
laboratory and field conditions. Potential interferences of 10 volatile
organic compounds (VOCs) on CRDS NH3 measurement were tested with
simultaneous VOC analysis performed by proton-transfer-reaction mass
spectrometry (PTR-MS). Both laboratory and field calibrations show excellent
linearity over a large dynamic range of NH3 concentrations. The
analyzer shows a small humidity effect of up to a few ppb in the extreme
case of a nearly water-saturated air stream. Apart from the negligible
humidity dependency, no interferences of the tested VOCs were observed.
Overall, the CRDS system performs satisfactory and is well suited for
measurements of NH3 emissions from livestock production.</p
‘This restless enemy of all fertility’: exploring paradigms of coastal dune management in Western Europe over the last 700 years
Drifting sand has inundated settlements and damaged agricultural land along the coasts of Western Europe for the last 700 years. The need to control sand migration has been an important driver of the management of coastal sand dunes and here we analyse original archival materials to provide new insights into historically changing coastal dune management practices. Records of coastal sand movement in Denmark, The Netherlands, Britain, Ireland and France were reviewed and three distinct management approaches were identified. The ways in which these approaches have played out in space and time were examined with particular reference to records from landed estates in Britain and Ireland. We demonstrate how historical evidence can be used to inform contemporary debates on dune management strategy and practice. We propose a new place-based approach to the future management of coastal dunes that can incorporate both expert and locally produced ‘knowledges’ and that is underpinned by an understanding of how both natural forces and human interventions have shaped these dune landscapes over time
Heated indoor swimming pools, infants, and the pathogenesis of adolescent idiopathic scoliosis: a neurogenic hypothesis
<p>Abstract</p> <p>Background</p> <p>In a case-control study a statistically significant association was recorded between the introduction of infants to heated indoor swimming pools and the development of adolescent idiopathic scoliosis (AIS). In this paper, a neurogenic hypothesis is formulated to explain how toxins produced by chlorine in such pools may act deleteriously on the infant's immature central nervous system, comprising brain and spinal cord, to produce the deformity of AIS.</p> <p>Presentation of the hypothesis</p> <p>Through vulnerability of the developing central nervous system to circulating toxins, and because of delayed epigenetic effects, the trunk deformity of AIS does not become evident until adolescence. In mature healthy swimmers using such pools, the circulating neurotoxins detected are chloroform, bromodichloromethane, dibromochloromethane, and bromoform. Cyanogen chloride and dichloroacetonitrile have also been detected.</p> <p>Testing the hypothesis</p> <p>In infants, the putative portals of entry to the blood could be dermal, oral, or respiratory; and entry of such circulating small molecules to the brain are via the blood-brain barrier, blood-cerebrospinal fluid barrier, and circumventricular organs. Barrier mechanisms of the developing brain differ from those of adult brain and have been linked to brain development. During the first 6 months of life cerebrospinal fluid contains higher concentrations of specific proteins relative to plasma, attributed to mechanisms continued from fetal brain development rather than immaturity.</p> <p>Implications of the hypothesis</p> <p>The hypothesis can be tested. If confirmed, there is potential to prevent some children from developing AIS.</p
Methane Clumped Isotopes: Progress and Potential for a New Isotopic Tracer
The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding petroleum systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. In general, clumped isotope measurements indicate plausible formation temperatures for abiotic, thermogenic, and microbial methane in many geological environments, which is encouraging for the further development of this measurement as a geothermometer, and as a tracer for the source of natural gas reservoirs and emissions. We also highlight, however, instances where clumped isotope derived temperatures are higher than expected, and discuss possible factors that could distort equilibrium formation temperature signals. In microbial methane from freshwater ecosystems, in particular, clumped isotope values appear to be controlled by kinetic effects, and may ultimately be useful to study methanogen metabolism
Role of Water Molecule in the Gas-Phase Formation Process of Nitrated Polycyclic Aromatic Hydrocarbons in the Atmosphere: A Computational Study
Modified analysis method for particulate PAH, S-PAC and oxygenated PAH by capillary GC-ion trap MS
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