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Mercury can travel over long distances, and bioaccumulate in the trophic chain thereby posing a threat to not only humans but also animals and plants. Mercury also causes neurological problems such as the Minamata diseases. Pollution and toxicity of mercury have become a global problem that requires immediate attention. In this study, a thermal-desorption technique using a Zeeman direct mercury (Hg) analyser (DMA) was employed for the quantification of Hg in river sediments as well as for Hg thermo-scanning to investigate the behaviour of Hg release from sediments. Thermal speciation was based on comparison of the temperatures at which Hg species in sediments were thermally released to the temperatures at which Hg in known standards were released. Moreover, total Hg concentrations in river sediments were measured using a DMA. The accuracy of the method for total Hg quantification was confirmed by the analysis of several standard reference materials of sediment (SRM2709a, NCS DC 73325, NCS DC 73374, NCS DC 73316 and NCS DC 73322) and quantitative percentage recoveries ranging from 84 to 99% were obtained. The total Hg concentrations in sediments ranged from 7.4 to 35.2 ng/g and 2.1 to 21.2 ng/g in the low and high flow seasons, respectively. Different forms of Hg associated with river sediments were successfully identified by thermo-desorption technique. The concentrations of Hg in the sediment samples were all below 200 ng/g which is the sediment quality guideline set by the United States Environmental Protection Agency (US EPA). Different species of Hg were present in the sediment samples, with humic acid and/or iron oxide being the most predominant forms of Hg associated with the sediments. [ABSTRACT FROM AUTHOR]

Aromatic chlorinated compounds, such as 1,2-dichlorobenzene, are considered as precursors of dioxin formation and their removal from flue gas using adsorption technology could be a solution. Faujasite type zeolites seem to be the most promising adsorbent, as the size of its porosity matches the size of the molecule. Even though the cationic faujasites are hydrophilic, the strength of interaction of chlorinated aromatic compounds adsorbed in porosity are higher than with more silicic faujasite such as FAU-NaY. FAU-NaX commercial beads have been Nd3+ exchanged at different rates. Dichlorobenzene dynamic gas adsorption has been performed via a thermobalance with vapours at concentration of 938 ppm in nitrogen gas flow and the quantities absorbed have been recorded during time. Then, from the coupling of a thermobalance with an in-line mass spectrometer, the desorbed quantities and desorption temperatures have been measured for both water and dichlorobenzene. Total quantities of 1,2-dichlorobenzene adsorbed onto partially exchanged FAU-Nd-NaX zeolites increases with the exchange rate: it has been measured a capacity of 23.3 wt % (relative to activated zeolite) for the most exchanged FAU-Nd-NaX at exchange rate of 53.6 %. For that zeolite, 74.7 % of the 1,2-dichlorobenzene is adsorbed at high-energy bonds with cations, desorbable at temperatures higher than 160 °C. The desorption temperature of dichlorobenzene decreases from 380 to 310 °C for FAU-NaX and the FAU-Nd-NaX at exchange rate of 53.6 % and remains higher than that of water. So that, thermal-desorption remains a separative process between water and chlorinated molecules previously adsorbed on cationic faujasites. [Display omitted] • FAU-NaX beads have been partially exchanged by Nd3+ cations at different rates. • The amounts of 1,2-DCB adsorbed onto the exchanged FAU (X) beads increases with the Nd3+ exchange rate. • The desorption temperature of 1,2-DCB decreases from 380 to 310 °C with the Nd3+ exchange rate from 0 to ca. 54 %. • Different strengths of interaction of 1,2-DCB molecules with the zeolite framework are clearly identified by TG/MS analyses. [ABSTRACT FROM AUTHOR]

High contents of mercury (Hg) have been found in old mining-metallurgy sites occurring a widespread contamination and degradation of the land. The ability to identify the Hg species present in these areas is essential to clarify fate of Hg and its bioavailability and additionally, to be able to parameterize remediation techniques based on thermal desorption in order to carry out a full-scale decontamination of the land. This study has proven the usefulness of a thermal programmed desorption procedure (Hg-TPD) for identifying Hg species in contaminated samples related to mining-metallurgy activities. Hg bound to organic matter (Hg-OM) and to pyrite (Hg-FeS 2 ), HgS red, HgCl 2 , Hg 0 and HgO were identified in most of waste samples. The absence of mobile Hg species in soils and sediments showed both its re-emission to the atmosphere (Hg 0 ) or of its oxidation and lixiviation (HgO and HgCl 2 ) over the years. The results have demonstrated that most of these polluted solids can be remediated by thermal treatment at temperatures ranging between 150 and 600 °C. The study evidence that Hg-TPD is useful either for parameterizing a thermal remediation or for identifying the evolution pathways of Hg species in different environmental compartments and in general, for any environmental remediation treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • More efficient Joule heating production were obtained at higher voltage. • Nearly 100% Benzoic acid (BA) was desorpted from CNTs film at an optimium voltage. • Electrothermal regeneration has extremely lower energy consumption. Thermal-desorption has been considered as an environmentally friendly approach to regenerate the exhausted adsorbents to achieve a sustainable adsorption process. However, the traditional thermal desorption method suffers from the demanding contradiction between the desorption efficiency and energy consumption. Herein, we developed an efficient and economical thermal-desorption strategy based on the Joule heating by employing a three-dimensional carbon nanotubes (CNTs) film as the model adsorbent. The features of CNTs film with negative temperature coefficient endow the impressive heat production for the electrical resistance decreased from 341.0 Ω at 25.7 °C to 36.7 Ω at 76.5 °C. The desorption ratio of target pollutant (i.e., benzoic acid) in the continuous Joule heat induced thermal desorption process could be reached to 93.2% with the energy consumption of 0.25 kW h, which is two orders of magnitude lower than that in the indirect thermal desorption process for one ton of wastewater at the specified scale. This study proposed a green and energy-efficient strategy for thermal regeneration, and provide a method guidance for the development of green regeneration technology. [ABSTRACT FROM AUTHOR]

Abstract: Reference materials for particulate matter (PM) on filter media are not available for the quantification of polycyclic aromatic hydrocarbons (PAHs) in ambient air. This is due to the difficulty of obtaining reference material that has a homogeneous distribution on a filter surface that is large enough for characterization and distribution. High volume sample filters from different locations and seasons were considered to validate the feasibility of the use of quartz filters as reference material for PAH concentrations. A rapid thermal desorption (TD) technique coupled with gas chromatography/mass spectroscopy was applied to characterise the material for the content of fifteen different PAHs. TD technique allowed for rapid and accurate analysis of small sections of filter (5mm diameter), leaving enough material for the production of twenty sub-filter cuts (42mm diameter) that could be used for distribution and control. Stability and homogeneity tests required for material certification were performed as indicated by the ISO guide 34:2009 and ISO 35:2006. The contribution of the heterogeneous distribution of PAHs on the filter surface resulted generally lower than 10% and higher for more volatile PAHs. One year of storage at −18°C indicated no significant variation in PAH concentrations. Nevertheless, a methodology for shipping and storing of the filter material at ambient temperature in especially designed plastic envelopes, was also shown to allow for stabile concentrations within twenty days. The method accuracy was confirmed by the analysis of NIST SRM 1649a (urban dust) and PAH concentrations were validated against the reference values obtained from an inter-laboratory exercise. In the case of benzo[a]pyrene for masses quantified between 100pg and 10ng the TD method provided expanded uncertainties of circa 10%, while the inter-laboratory reference value uncertainties ranged between 15 and 20%. The evaluation of these results supports the use of the presented methodology as a valid approach for the certification of PAH concentrations in PM10 quartz filters. The methodology allows for the production of a certificate of analysis for a single high volume filter, the concentration of which can easily be adjusted by selecting an appropriate sampling location. [Copyright &y& Elsevier]

Urban atmospheric samples were collected in A Coruña (NW Spain) and analysed for volatile organic compounds. One hundred and twenty one hour samples were collected in winter 2000. The ambient air was rich in benzene, toluene, ethyl-benzene and xylenes (BTEX) and especially toluene (mean: 23.6 μg m-3, median: 14.66 μg m-3), but the presence of chlorinated compounds was also notable. High concentrations of 1,4-dichlorobenzene (mean: 11.4 μg m-3, max: 90.4 μg m-3) were recorded. Multivariate analysis of VOC, trace gases (NOx, NO2, NO, SO2 and O3) and meteorological variables (temperature, wind direction and speed, precipitation and radiation) was applied and correlations between VOC were also studied. Principal component analysis and correlation analysis confirm traffic as the main source of VOC in the area, although the importance of evaporative sources is also reflected. Three groups of samples were obtained by cluster analysis; these groups are formed depending on the content of aromatics and ozone and, in many cases, on the sampling hour. [Copyright &y& Elsevier]

• Coupling of ASE and ATD with GC/MSMS for analysis of indoor air and dust. • New vacuum cleaner head for the sampling of dust. • New technic for the assessment of bioaccessibility of dust. • Advantage of the use of SPME for quantification of organic compounds in mimic saliva and gastric liquids. A method coupling automated thermal desorption (ATD) with in-tube derivatization and solid phase micro-extraction (SPME), with on-injector derivatization gas chromatography - tandem mass spectrometry (GC/MSMS) was developed and used for the simultaneous quantification of 100 semivolatile (SVOCs) pollutants (50 pesticides, 16 PAHs, 22 PCBs, 7 phthalates and 5 alkylphenols) in indoor air, indoor dust, and for bioaccessibility evaluation. Chemical compounds in indoor air were sampled on Tenax-TA passive samplers (PAS) exposed for 15 days, while dust was collected on silicon carbide (SiC©) foam using a custom made vacuum cleaner head. After sampling, Tenax tubes from PAS were introduced directly into a thermal desorption tube while dust was extracted using accelerated solvent extractor (ASE). Extract is then used to spike clean Tenax-TA tube that is then treated as a Tenax from PAS. The derivatization agent (M t BSTFA) and a mix of internal standards were added into the tubes before thermal desorption and analysis by GC/MSMS. The SPME technique was applied to extract the 100 SVOCs from the different tested bioaccessibility solutions (saliva, gastric, intestinal). This method permits the determination of 100 pollutants in a single run, including those requiring a derivatization step, with very low quantification and detection limits. Indeed, ATD-GC/MSMS technic presents very low LOD (0.002 to 0.17 ng) and LOQ (0.007 to 0.56 ng) values while SPME-GC/MSMS displays slightly higher LOD (0.044 to 12.3 ng) and LOQ (0.10 to 37.0 ng) ranges. [ABSTRACT FROM AUTHOR]