Detection of dimethyl methylphosphonate (DMMP) with an interband cascade laser sensor.

We demonstrate the sensitive detection of dimethyl methylphosphonate (DMMP, a hydrogen-bond (HB) basic phosphonate ester) using additional optical loss induced in an interband cascade laser with top optical cladding layer replaced by an exposed sensing window coated by a HB acidic sorbent layer. Thin coatings of the sorbents HCSFA2 and oapBPAF were deposited on the sensing window to allow reversible capture and concentration of DMMP for optical interrogation. Analyte levels down to 0.1 mg/m3 (∼20 ppb) were tested and successfully detected by monitoring the laser's threshold or its output power at a fixed bias as a function of DMMP delivery concentration.

Re-constructing nutritional history of Serengeti wildebeest from stable isotopes in tail hair: seasonal starvation patterns in an obligate grazer.

RATIONALE: Nutritional bottlenecks often limit the abundance of animal populations and alter individual behaviours; however, establishing animal condition over extended periods of time using non-invasive techniques has been a major limitation in population ecology. We test if the sequential measurement of δ(15) N values in a continually growing tissue, such as hair, can be used as a natural bio-logger akin to tree rings or ice cores to provide insights into nutritional stress. METHODS: Nitrogen stable isotope ratios were measured by continuous-flow isotope-ratio mass spectrometry (IRMS) from 20 sequential segments along the tail hairs of 15 migratory wildebeest. Generalized Linear Models were used to test for variation between concurrent segments of hair from the same individual, and to compare the δ(15) N values of starved and non-starved animals. Correlations between δ(15) N values in the hair and periods of above-average energy demand during the annual cycle were tested using Generalized Additive Mixed Models. RESULTS: The time series of nitrogen isotope ratios in the tail hair are comparable between strands from the same individual. The most likely explanation for the pattern of (15) N enrichment between individuals is determined by life phase, and especially the energetic demands associated with reproduction. The mean δ(15) N value of starved animals was greater than that of non-starved animals, suggesting that higher δ(15) N values correlate with periods of nutritional stress. CONCLUSIONS: High δ(15) N values in the tail hair of wildebeest are correlated with periods of negative energy balance, suggesting they may be used as a reliable indicator of the animal's nutritional history. This technique might be applicable to other obligate grazers. Most importantly, the sequential isotopic analysis of hair offers a continuous record of the chronic condition of wildebeest (effectively converting point data into time series) and allows researchers to establish the animal's nutritional diary.

Micromechanical photothermal spectroscopy of trace gases using functionalized polymers.

We demonstrate a novel method to spectroscopically detect and identify trace gases. Micromechanical photothermal spectroscopy (MPS) with functionalized sorbent materials provides trace gas spectra in an optical interaction length of only a few micrometers. We use microcavity interferometry to read out displacements as low as 25 fm/√Hz, heating as low as 200 pW/√Hz, and analyte concentrations as low as 65 parts-per-billion for the nerve agent simulant DMMP. MPS integrated with functional materials represents an important new tool in chip-scale optical sensing.

Palaeoenvironmental modelling of δ(13) C and δ(15) N values in the North Atlantic Islands: understanding past marine resource use.

RATIONALE: Carbon (δ(13) C) and nitrogen (δ(15) N) analysis has been extensively used to investigate the importance of marine foods in the diet of archaeological populations in the North Atlantic Islands; however, few faunal studies exist to aid the interpretation of results. Palaeoenvironmental modelling of δ(13) C and δ(15) N values is crucial in determining whether changes in the stable isotope values are a result of dietary change, rather than temporal or geographical fluctuations in carbon and nitrogen. Investigating faunal dietary behaviour can provide an insight into past foddering and land management strategies. METHODS: Detailed sampling of wild and domestic species for bulk collagen analysis was undertaken in order to characterise geographical variations in δ(13) C and δ(15) N values in the Outer Hebrides and Orkney. Samples from the Neolithic to the Norse period were analysed to assess temporal and geographical variations in δ(13) C and δ(15) N values, in addition to determining the contribution of marine foods to the diet of local fauna. RESULTS: A δ(15) N shift of 1‰ was observed between the Outer Hebrides and Orkney in the Neolithic and Iron Age. A geographical variation in δ(13) C values was observed in the Norse period between Orkney and the Outer Hebrides. Temporal fluctuations in δ(13) C and δ(15) N values demonstrate variations in foddering practices of sheep in the Outer Hebrides. Pig specimens from the Outer Hebrides demonstrated evidence of marine food consumption in the Iron Age. CONCLUSIONS: Faunal dietary behaviour can act as a vital indicator of the importance of marine resources in the past. Characterisation of faunal δ(13) C and δ(15) N values geographically and temporally is crucial in our interpretation of human dietary behaviour.

Variation in blood mercury concentrations in brown skuas (Stercorarius antarcticus) is related to trophic ecology but not breeding success or adult body condition.

Mercury is a pervasive environmental contaminant that can negatively impact seabirds. Here, we measure total mercury (THg) concentrations in red blood cells (RBCs) from breeding brown skuas (Stercorarius antarcticus) (n = 49) at Esperanza/Hope Bay, Antarctic Peninsula. The aims of this study were to: (i) analyse RBCs THg concentrations in relation to sex, year and stable isotope values of carbon (δ13C) and nitrogen (δ15N); and (ii) examine correlations between THg, body condition and breeding success. RBC THg concentrations were positively correlated with δ15N, which is a proxy of trophic position, and hence likely reflects the biomagnification process. Levels of Hg contamination differed between our study years, which is likely related to changes in diet and distribution. RBC THg concentrations were not related to body condition or breeding success, suggesting that Hg contamination is currently not a major conservation concern for this population.

Photonic microharp chemical sensors.

We describe a new class of micro-opto-mechanical chemical sensors: A photonic microharp chemical sensor is an array of closely spaced microbridges, each differing slightly in length and coated with a different sorbent polymer. They are optically interrogated using microcavity interferometry and photothermal actuation, and are coupled directly to an optical fiber. Simultaneous measurements of the fundamental flexural resonant frequency of each microbridge allow the real-time detection and discrimination of a variety of vapor-phase analytes, including DMMP at concentrations as low as 17 ppb.

Element patterns in albatrosses and petrels: influence of trophic position, foraging range, and prey type.

We investigated the concentrations of 22 essential and non-essential elements among a community of Procellariiformes (and their prey) to identify the extent to which trophic position and foraging range governed element accumulation. Stable isotope analysis (SIA) was used to characterise trophic (delta(15)N) and spatial patterns (delta(13)C) among species. Few consistent patterns were observed in element distributions among species and diet appeared to be highly influential in some instances. Arsenic levels in seabird red blood cells correlated with delta(15)N and delta(13)C, demonstrating the importance of trophic position and foraging range for arsenic distribution. Arsenic concentrations in prey varied significantly across taxa, and in the strength of association with delta(15)N values (trophic level). In most instances, element patterns in Procellariiformes showed the clearest separation among species, indicating that a combination of prey selection and other complex species-specific characteristics (e.g. moult patterns) were generally more important determining factors than trophic level per se.

Urban geochemistry: research strategies to assist risk assessment and remediation of brownfield sites in urban areas.

Urban geochemical maps of Wolverhampton and Nottingham, based on multielement analysis of surface soils, have shown distribution patterns of "total" metals concentrations relating to past and present industrial and domestic land use and transport systems. Several methods have been used to estimate the solubility and potential bioavailability of metals, their mineral forms and potential risks to urban population groups. These include sequential chemical extraction, soil pore water extraction and analysis, mineralogical analysis by scanning electron microscopy, source apportionment by lead isotope analysis and the development of models to predict metal uptake by homegrown vegetables to provide an estimate of risk from metal consumption and exposure. The results from these research strategies have been integrated with a geographical information system (GIS) to provide data for future land-use planning.

Contaminant source apportionment by PIMMS lead isotope analysis and SEM-image analysis.

By combining scanning electron microscopy (SEM) image analysis and laser ablation plasma ionisation multi-collector mass spectrometry (LA-PIMMS), high precision lead isotope analyses can be obtained from individual metal-rich particles. Soils from Wolverhampton and Nottingham were sampled on the basis of high Pb concentrations or brownfield location. Pressed powder pellets of each were rastered by LA-PIMMS to obtain a bulk Pb-isotope signature. The results plot along an apparent mixing line between the major sources of lead contamination in the UK, that is UK ore deposits and alkyl-lead from petrol additives (Australian ore). Two particularly lead-rich soils were chosen to investigate the lead distribution and isotope variability between size and density fractions. The fine-grained and low-density fractions contained most of the lead and have Pb-isotope ratios comparable with the bulk soils. By contrast, the small, lead-enriched denser fractions contained only a minor proportion of the total lead but Pb-isotope signatures indicating relative enrichment in one or other of the end-members from the mixing line. Further characterisation of individual Pb-rich grains is in progress.

Solubility properties in polymers and biological media. II. A new method for the characterisation of the adsorption of gases and vapours on solids.

Henry's constants at zero solute pressure have been determined by the gas chromatographic peak shape method for twenty-two solutes on four adsorbents (Rohm and Haas Ambersorb XE-348F carbonaceous adsorbent at 323 and 373 K, Sutcliffe Speakman 207A and 207C at 323 K, and Calgon Filtrasorb activated carbon at 323 K). The limiting values of log KH have been analysed in terms of solute dipolarity (pi 2*), solute hydrogen-bond acidity (alpha 2), and basicity (beta 2), and a new solute parameter (log L16), the solute Ostwald absorption coefficient on eta-hexadecane. The multiple linear regression equation, SP = SP0 + l.log L16 + s(pi 2* + d delta 2) + a alpha 2 + b beta 2 where in this instance SP = -log KH, can be used to identify the nature of the solute-adsorbent interactions, and to predict further values of log KH. For the solutes and solids we have studied, only the l.log L16 term is statistically significant, and hence--log KH is proportional to l.log L16. It is concluded that interactions between the gaseous solutes (that include alcohols and amines) and the four adsorbents involve just general dispersion forces.