Online hourly determination of 62 VOCs in ambient air: system evaluation and comparison with another two analytical techniques

This paper presents results of the processing and validation of data collected by an automatic gas chromatograph (AGC). This system was used to monitor 62 volatile organic compounds (VOCs) in urban air in the Basque Country, Spain. The nonpolar compounds (C2-C10) identified-paraffins, olefins, aromatics, and chlorinated compounds-accounted for 88% of the mass of total non-methane hydrocarbons (TNMHCs) in ambient air. The evaluation of linearity, precision, detection limits (DLs), and stability of retention times (RTs) indicates that the equipment is suitable for measuring ambient air automatically for prolonged periods (6 months). The calibration of the equipment using response factors calculated on the basis of the effective carbon number (ECN) showed variations of over 10% for acetylene, isoprene, and n-hexane. The results provided by the automatic chromatograph correlated significantly with simultaneous results from other widely used techniques for determining VOCs in ambient air: (1) portable GC, equipped with photoionization detector (PID), and (2) active adsorption on Tenax-TA followed by thermal desorption and chromatographic analysis.     

Evolution and kinetics of volatile organic compounds generated during low-temperature polymer degradation

A method using direct flame ionization detector (FID) measurement was developed to study total volatile organic compound (VOC) emissions during thermal degradation of polymers. This method was used to estimate organic emissions from different polymers, such as low-density polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and commingled postconsumer streams, such as recycled carpet residue and auto shredder residue (ASR). The effects of process parameters, such as temperature, heating rate, and residence time, were also studied. Significant VOC emissions were observed at normal processing temperatures, particularly from recycled polymers. Each polymer showed a distinct evolution pattern during its thermal degradation. The kinetics of VOC emissions were also studied using a nonisothermal technique. The kinetic parameters were in agreement with data from the literature.     

Model selection in demographic time series using VC-bounds

The problem of distinguishing density-independent (DI) from density-dependent (DD) demographic time series is important for understanding the mechanisms that regulate populations of animals and plants. We address this problem in a novel way by means of Statistical Learning Theory (SLT); SLT is built around the idea of VC-dimension, a complexity index for classes of parameterized functions. Though VC-dimensions of nonlinear models are generally unknown, in the linear case VC-dimension actually corresponds to the number of free parameters; this allows one to straightforwardly apply the model selection framework developed within SLT, and called Structural Risk Minimization (SRM). We generate noisy artificial time series, both DI and DD, and use SRM to recognize the model underlying the data, choosing among a suite of both density-dependent and independent demographies. We show that SRM significantly outperforms traditional model selection approaches, such as the Schwartz Information Criterion and Final Prediction Error in recognizing both density-dependence and independence.     

An integrated ecotoxicological approach to assess the effects of pollutants released by unexploded chemical ordnance dumped in the southern Adriatic (Mediterranean Sea)

In order to gain preliminary knowledge about the threat to marine ecosystems due to leakage of chemical warfare agents (CWAs) and other pollutants from rusting bombshells on the seabed, a case study was conducted in a dumping area in the southern Adriatic Sea (depth 200–300 m). Following electroacoustic and magnetometric surveys of the CWA dumping area, an integrated ecotoxicological approach was used. This approach was based on analysis of CWA residues and their metabolites, including arsenic, in sediment and organisms, as well as multimarker methodology including the Health Assessment Index, histological lesion analysis and enzyme assays. Two sentinel species were selected, the blackbelly rosefish [Helicolenus dactylopterus (Delaroche, 1809)] and the European conger (Conger conger L., 1758). Sediment analysis revealed the presence of CWA degradation products, including 1-4-thioxane and 1-4-dithiane. Tissues of fish from the CWA dumping site showed higher levels of arsenic than those from the reference site. Neither CWAs nor their metabolites were detected in fish tissues. Arsenic levels recorded in blackbelly rosefish were well above those reported for other fish species from the southern Adriatic, much higher than the FDA limit for food (2.6 mg kg⁻¹) and close to the LD₅₀ calculated for mammals (20 mg kg⁻¹ body weight). The presence of pollutants in the CWA dumping site was also confirmed by pathological lesions in both species and EROD activity, two to three times higher than in fish from the reference site (16.45±8.08 and 8.05±5.87 pmol min⁻¹ mg protein⁻¹ in blackbelly rosefish and 269±24.92 and 78.71 pmol min⁻¹ mg protein⁻¹ in European conger, respectively). Cholinesterase activity seemed unaffected in muscle of both species, whereas in brain they were one-third of those recorded in fish from the reference site (14.22±10.05 and 72.87 nmol min⁻¹ mg protein⁻¹, respectively). This suggests that acetylcholinesterase is sensitive to CWAs. In conclusion, the agreement of all the chemical and biological parameters investigated suggests that the integrated ecotoxicological approach used is appropriate to reveal the presence and biological effects of CWAs in the marine ecosystem. Physical and Chemical Impacts on Marine Organisms, a Bilateral Seminar in Italy–Japan held in November 2004.     

Plasma sex steroid and vitellogenin profiles during gonad development in wild Mediterranean amberjack (<Emphasis Type="Italic">Seriola dumerilii</Emphasis>)

Mediterranean amberjacks, Seriola dumerilii Risso, were caught off the Pelagie Islands, in the south Mediterranean Sea, between May 1997 and June 1999. Fish blood was sampled, and gonads were collected at 10-day intervals throughout the spawning period and at monthly intervals during the resting period. Concentrations of plasma estradiol-17ß (E₂), testosterone (T), 17,20ß-dihydroxy-4-pregnen-3-one (DHP) and vitellogenin (Vtg) in females; and plasma T and 11-ketoT (11-KT) in males were correlated with changes in gonadal development. The first females that had already ovulated (F5) were found in late May. Most mature females (F4) were caught in June. Post-spawned females (F6) were found from late July until September. Estradiol-17ß was at baseline levels (<0.02 ng ml^–1) during autumn/winter and rapidly peaked (6.29±0.68 ng ml^–1) from May to early July. Plasma T levels showed a similar profile and were positively correlated to E₂ (r²=0.668) during the spawning period. Continuously elevated levels of E₂ and T were observed during the spawning season in vitellogenic females (stages F3, F4 and F5). Resting females were found during the autumn/winter months. Vitellogenin levels increased during May and peaked in June, reverting to undetectable levels in August, in parallel with sex steroid changes. Plasma DHP levels peaked in June (283.45±97.3 pg ml^–1), falling to basal values (<5 pg ml^–1) in August. DHP levels were higher in mature females (F4) than in maturing (F3) and in partially ovulated (F5) females. DHP values increased during germinal vesicle migration, peaked during germinal vesicle breakdown and decreased again during complete oocyte hydration. In males, changes in T and 11-KT plasma levels were related to testis development. The highest levels of T (5.76±2.64 ng ml^–1) were measured during spermatogenesis and highest 11-KT (5.28±3.6 ng ml^–1) in males with milt, from May to June. This study provides information, for the first time, on the relation between plasma sex steroid profiles and gonad development in wild Mediterranean amberjack, a useful benchmark for broodstock monitoring under controlled conditions.Communicated by R. Cattaneo-Vietti, Genova     

Integrating pattern-based modelling and political ecology in land-use change research: the case of Mexican dry tropics

ABSTRACT

Agricultural and extractive frontiers experiment rapid landscape transformation. Land-Use Sciences and Political Ecology are complementary approaches for analysing how landscape transformations are related to biophysical conditions, and socioeconomic, cultural and political processes developed at global, national and local scales. This study examines such relationships in a long-standing agrarian and resource frontier in southern Mexico for the 1986–2015 period. We combine insights from: (1) a quantitative land use/land cover change pattern-based model, involving a weights of evidence and cellular automata simulations, and (2) a qualitative content analysis of literature and of local actors’ perspectives. Two grand frontier processes have developed in this region: NAFTA-related agrarian transition toward intensification and the establishment of wind farms. Both were triggered by global forces and new forms of land and resources use, but mediated by national-to-local ecological, socioeconomic and political processes, producing particular landscape transformations.     

Monitoring trace metals in urban aerosols from Buenos Aires city. Determination by plasma-based techniques

A study was undertaken, within the framework of a 3 years national project, to assess the content of 13 elements in airborne particulate matter collected in representative zones of the metropolitan area of Buenos Aires. The sampling strategy followed consisted in collecting simultaneously 67 samples of PM10 particulate matter in 9 sampling sites covering an area of about 30 km2 during one week. The collection was performed on ash-free fibre-glass filters using high volume samplers. A combination of aqua regia and perchloric acid was used for leaching metals from filters. Key elements, namely Al, Ca, Cu, Fe, Mn, Mo, Ni, Pb, S, Sb, Sn, Zn and Zr, were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) at micro g g(-1) and ng g(-1) levels. Analyte concentration varied from 130 ng g(-1)(Mo) to over 30%(Ca). Multivariate statistical analysis was performed on the data set including the measured elemental compositions for the monitored period. The atmospheric concentration found for Pb confirms the decreasing levels of this element since the introduction of unleaded gasoline in 1995: 88 ng m(-3)(2001) < 220 ng m(-3)(1997) < 3900 ng m(-3)(1994). The average S concentration above 3 microg m(-3) is somehow unexpectedly high for Buenos Aires since the relatively low S content of liquid fuels and the massive usage of natural gas imply low emissions of this element from combustion activities. To the best of our knowledge, S concentrations are reported for the first time for this city.