Unprocessed petroleum hydrocarbons often contain high concentrations of mercury (Hg), which can severely damage the metal components of a processing plant and pose a health risk to the workers and the natural environment. Although Hg removal units can significantly reduce the Hg concentration in the export products, they are often installed in the final stage of the processing plant, thus failing to protect the production facilities. In this study, Hg distribution within a natural gas processing plant was studied to identify the most effective place for a Hg removal unit. Additionally, the impact of sampling container materials and their acidification was evaluated, and Hg species in the condensate were quantified. Total Hg concentration was significantly higher in all samples stored in glass in comparison to that with plastic containers. However, the acidification effect of the containers was more pronounced for Hg in nonpolar solutions. Interestingly, the assessment of Hg distribution within the gas plant showed that the export gas is being enriched in Hg, whose concentration rose from 1.25 to 4.11 μg/Sm3 during the processing steps. The second stage separator was identified as the source of excess Hg, which partitioned from the liquid phase of condensate to the gas phase as a result of reduced operational pressure and temperature. The dominant Hg species found in the analyzed gas condensates were elemental Hg (Hg0) and inorganic Hg with the methylmercury fraction comprising up to 18%. However, it was also found that the % fraction of individual Hg species varied along the plant units most likely as a result of Hg0 migration to the export gas. Therefore, to protect all treatment facilities from Hg contamination, the Hg removal unit should be installed after the second stage compressor.

•MeHg and total Hg were measured in 87 rice and rice products from European markets.•9 baby rice products among 19 samples were validated by two orthogonal methods.•MeHg in precooked baby rice shows a higher proportion of MeHg versus total Hg.•European rice shows significantly higher variability than rice from other origins.•A significant number of rice samples was above 10% of the PTWI.Rice is known to accumulate methylmercury (MeHg) in the rice grains. MeHg as a neurotoxin impacts on the human central nervous systems and especially on the developing brain. In this exploratory study, 87 commercial rice products sold in Europe, including nine baby-rice products, were analyzed for total Hg and MeHg content. MeHg concentration in all rice products investigated range from 0.11 to 6.45 μg kg−1 with an average value of 1.91 ± 1.07 μg kg−1 and baby-rice is not significantly different from other rice products. Total Hg ranges from 0.53 to 11.1 μg kg−1 with an average of 3.04 ± 2.07 μg kg−1. MeHg concentrations in all rice products studied in this work would not exceed the provisional tolerable weekly intake (PTWI). 30% of all commercial market rice products exceeded 10% of the PTWI calculated for toddlers or 13% of products for adults with rice based diet.Graphical abstract

•High levels of Hg found in freshwater sediment from the Union Canal, Scotland, UK.•Lower mercury concentrations in sediment from the Forth & Clyde Canal, Scotland, UK.•Low methylmercury concentrations found in sediments from both canals.•Significant inverse relationship between total Hg and %MeHg concentrations.•Ethylmercury detected in sediment from the Union Canal.Mercury concentrations were investigated in freshwater sediment from two canals in Scotland, UK. High concentrations found in the Union Canal (35.3–1200 mg kg−1) likely originate from historical munitions manufacture, with lower levels in the Forth & Clyde Canal (0.591–9.14 mg kg−1). Concentrations of methylmercury (MeHg) were low – from 6.02 to 18.6 μg kg−1 (0.001–0.023% of total Hg) in the Union Canal and from 3.44 to 14.1 μg kg−1 (0.11–0.58% of total Hg) in the Forth & Clyde Canal – and there was a significant inverse relationship between total Hg concentration and %MeHg. Total Hg concentration was significantly negatively correlated with pH and positively correlated with Fe content (in the Union Canal only) but not with organic matter, S content or the proportion of clay present. The MeHg concentration was not correlated with any of the above sediment parameters. Ethylmercury was detected in the most highly contaminated sediments from the Union Canal.Download high-res image (294KB)Download full-size image

Particulate HgS is generally thought to be the most abundant Hg species in stored petroleum hydrocarbons stocked on-shore. It is also assumed that due to its high stability constant, HgS is chemically inert. However, results from the current study would suggest otherwise. First, a comparison study of the analytical performance of ICP-MS and CV-AFS with respect to matrix effects showed no significant difference in the measured Hg concentrations in studied samples when CV-AFS is used in the alkali mode. Subsequently, the suitability of three quantification methods during Hg speciation was investigated. Both external calibration and standard addition methods proved troublesome with the former showing matrix dependence and the latter being hindered by the formation of an emulsion during the derivatization step. Results from species-specific isotope dilution (SS-ID-GC-ICP-MS), on the other hand, obtained at different equilibration times, showed a random variation in the calculated Hg2+ concentration (RSD 32%), suggesting that factors independent of equilibration time cause the observed variation. Further sedimentation of Hg particulate by means of ultracentrifugation improved the precision of SS-ID-GC-ICP-MS by 10-fold. These results would suggest that Hg particles in petroleum products are reactive at low temperature during Grignard alkylation.

Recent studies of methylmercury (MeHg) in rice have shown that rice grown on mercury contaminated soil contributes to the human MeHg intake similar to a fish diet. Trace levels of MeHg in biological samples are often determined via a complex multi-stage process following EPA method 1630. We developed a simple and cost effective method suited for food quality monitoring based on a simple sample preparation procedure and the subsequent analysis of the sample with online preconcentration via solid phase extraction high performance liquid chromatography cold vapor atomic fluorescence spectrometry (SPE-HPLC-CV-AFS). The reliability of this method for MeHg in rice and rice products in the low ppb range was investigated for 4 different rice product samples. At present, no CRM for MeHg in rice or rice products is available. Therefore we cross-validated our method against standard addition and species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICPMS), which showed no significant difference versus the external calibration with SPE-HPLC-CV-AFS. Potential species interconversion during sample preparation and measurement was ruled out by using a spike of isotopically enriched inorganic mercury. The SPE-HPLC-CV-AFS developed in our work has proven to be a robust, fast, cost efficient, competitive and reliable method for MeHg speciation in rice and rice products with a limit of detection of 0.12 µg kg−1 and a reproducibility comparable to the SS-ID-GC-ICPMS method which is sufficient for the determination of MeHg in the four market rice samples. The concentrations of MeHg ranged from 1.6 to 2.7 µg kg−1.

•We demonstrate that a novel mixture of thiourea-thiolsilica shows an excellent trapping of MeHg between a broad pH range 1–6.•We develop the method so that it can potentially be automated for inorganic and methyl-mercury.•The method is matrix independent with highly accurate results for MeHg in hair CRM extracts and spiked water samples•The limit of detection is around 40 pg/L when just 200 mL sample is used, without any intensive preparationUltra-traces of methylmercury at the sub-ppt level can be magnified in the foodweb and is of concern. In environmental monitoring a routine robust analytical method is needed to determine methylmercury in water. The development of an analytical method for ultra-trace speciation analysis of methylmercury (MeHg) in water samples is described. The approach is based on HPLC-CV-AFS with on-line preconcentration of water samples up to 200 mL, resulting in a detection limit of 40 pg/L (ppq) for MeHg, expressed as Hg. The unit consists of an optimized preconcentration column filled with a sulfur-based sorption material, on which mercury species are preconcentrated and subsequently eluted, separated and detected via HPLC-CV-AFS (high performance liquid chromatography–cold vapor atomic fluorescence spectrometry). During the method development a type of adsorbate material, the pH dependence, the sample load rate and the carry-over were investigated using breakthrough experiments. The method shows broad pH stability in the range of pH 0 to 7, without the need for buffer addition and shows limited matrix effects so that MeHg is quantitatively recovered from sewage, river and seawater directly in the acidified samples without sample preparation.

Organotin compounds are used as pesticides and fungicides as well as additives in plastics. This study identifies the de novo generation of novel volatile organotins in municipal waste deposits and their release via landfill gas. Besides tetramethyltin (Me4Sn), a strong neurotoxin, and 5 previously reported organotins, 13 novel ethylated, propylated, and butylated tetraalkyltin compounds were identified. A concentration of 2−4 μg of Sn m−3 landfill gas was estimated for two landfill sites in Scotland. The atmospheric stability of Me4Sn and methylated tin hydrides was determined empirically in a static atmosphere in the dark and under UV light to simulate night- and daytime conditions. Theoretical calculations were carried out to help predict the experimentally obtained stabilities and to estimate the relative stabilities of other alkylated species. Assuming first-order kinetics, the atmospheric half-life for Me3SnH was found to be 33 ± 16 and 1311 ± 111 h during day- and nighttime conditions, respectively. Polyalkylation and larger alkyl substitutes tend to reduce the atmospheric stability. These results show that substantial concentrations of neurotoxic organotin compounds can be released from landfill sites and are sufficiently stable in the atmosphere to travel over large distances in night- and daytime conditions to populated areas.

Arsenic (As) occurs in a variety of different chemical forms, among them volatile (gaseous) species, usually referred to as arsine and methylarsines. Here we demonstrate that arsine and methylarsines are stable in air in concentrations at the μg/L gas level. We determined half-lives of approximately 8 h under daytime conditions (UV light) for all methylated arsines, while the same species were found to be considerably more stable in night-time (dark) conditions. Arsine (AsH3) showed under both day and night-time conditions, considerably higher stabilities than methylated arsines. We show here that volatile As species seem stable enough to travel considerable distances in the atmosphere from a point source before converting into nonvolatile, oxidized compounds. Also, the degradation pathway leading to the conversion to nonvolatile compounds was investigated using computational chemistry. Arsine and methylarsines' reactions with the hydroxyl radical (•OH) as well as As−C and As−H bonds strengths in the species studied were modeled. Results showed that conversion could not be explained by H abstraction, nor by OH addition. Moreover, it was found that As−C and As−H bonds strengths are not the determining factor responsible for the decrease in stability with ascending methylation of the different volatile arsine species, as previously suggested.

Triphenyltin (TPhT) is a biocide used worldwide in agriculture, especially in rice crop farming. The distribution and dissipation of TPhT in rice fields, as well as uptake of TPhT and other phenyltin compounds (monophenyltin, MPhT, and diphenyltin, DPhT) is still unknown at present. In this study, speciation analysis of phenyltin compounds was carried out in soil and water from a rice field where TPhT was applied during rice seeding according to legal application rates in Brazil. The results indicate the degradation of biocide and distribution of tin species into soil and water. To evaluate whether TPhT is taken up by plants, rice plants were exposed to three different TPhT application rates in a controlled mesocosm during 7 weeks. After this period, tin speciation was determined in soil, roots, leaves, and grains of rice. Degradation of TPhT was observed in soil, where DPhT and MPhT were detected. MPhT, DPhT, and TPhT were also detected in the roots of plants exposed to all TPhT application rates. Only TPhT was detected in leaves and at relatively low concentration, suggesting selective transport of TPhT in the xylem, in contrast to DPhT and MPhT. Concentration of phenyltin species in rice grains was lower than the limit of detection, suggesting that rice plants do not have the capability to take up TPhT from soil and transport it to the grains.

Class 13 and 14 Iron Age Scottish glass beads are a group of highly decorated beads of British origin or design, dating indicatively to the 1st and 2nd century AD and typically found in Aberdeenshire and Moray district (Guido, 1978, 85–9). Their distinctive stylistic characteristics and geographical segregation renders them ideal for the investigation of whether the glasses employed in their manufacture were imported rather than produced locally, and for the assessment of the technology used in the production of the deep colours. Studies performed in the 1980s on different specimens pertaining to the same Classes (Henderson, 1982) showed compositional characteristics differing from Iron Age southern British beads, suggesting a different source of glass for their manufacture. Here, a set of 19 beads which was never investigated before was analysed for 32 major, minor and trace elements using Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The sample set shows good homogeneity in major and minor element composition, indicating the use of imported natron glass, with standardized composition typical of Roman glass of the period, also reflected in the recipes used for colouration. Evidence for the use of cullet and waste glass was found, which, along with the particularity of the design, suggests a local origin of the beads and possible production by native glassworkers.Highlights► Rare Scottish Iron age glass beads were investigated for their main and trace element compositions. ► Distinct colours show good agreement in trace elements used for colouration. ► Homogeneity in composition points to standard recipes used for glass making. ► Base composition identifies Roman origin of the glass.

Volatile arsenic compounds in natural gas, existing in the form of trimethylarsine (TMAs), have been determined using gas cryo-trapping gas chromatography coupled to inductively coupled plasma-mass spectrometry (CT-GC-ICP-MS). The results from a number of different gas wells revealed a huge concentration spread ranging from below the detection limit of 0.2 up to 1800 µg/m3 TMAs (as As) in the gas. Due to the toxicity and corrosive nature of these arsines, they need near real time monitoring via a method that can easily be implemented on site, i.e. during gas exploitation. Here, we introduce a novel method which utilises silver nitrate impregnated silica gel tubes for quantitative chemotrapping of trimethylarsine (TMAs) from a natural gas matrix. Subsequent elution with hot nitric acid followed by online photo-oxidation hydride generation atomic fluorescence spectrometry (HG-AFS) is used for the determination of TMAs gas standards in nitrogen and natural gas samples, respectively. The chemotrapping method was validated using CT-GC-ICP-MS as a reference method. The recovery of arsenic from nitrogen or natural gas matrix ranged from 85 to 113% for a range of 20 to 2000 ng As. Trapping efficiency was >98%, from the methods LOD of 20 ng to 4.8 µg (absolute amount As) with sample sizes of 0.02 and 2 L gas. Method performance was established by comparing the results obtained for eight natural gas samples containing between 1 and 140 µg As/m3 with those achieved by the reference method (CT-GC-ICP-MS).

Mercury in plants or animal tissue is supposed to occur in the form of complexes formed with biologically relevant thiols (biothiols), rather than as free cation. We describe a technique for the separation and molecular identification of mercury and methylmercury complexes derived from their reactions with cysteine (Cys) and glutathione (GS): Hg(Cys)2, Hg(GS)2, MeHgCys, MeHgGS. Complexes were characterised by electrospray mass spectrometry (MS) equipped with an ion trap and the fragmentation pattern of MeHgCys was explained by using MP2 and B3LYP calculations, showing the importance of mercury–amine interactions in the gas phase. Chromatographic baseline separation was performed within 10 min with formic acid as the mobile phase on a reversed-phase column. Detection was done by online simultaneous coupling of ES-MS and inductively coupled plasma MS. When the mercury complexes were spiked in real samples (plant extracts), no perturbation of the separation and detection conditions was observed, suggesting that this method is capable of detecting mercury biothiol complexes in plants.

Speciation of trialkylated arsenic compunds in natural gas, pressurized and stable condensate samples from the same gas well was performed using (Cryotrapping) Gas Chromatography-Inductively Coupled Plasma Mass Spectrometry. The major species in all phases investigated was found to be trimethylarsine with a highest concentration of 17.8 ng/L (As) in the gas phase and 33.2 μg/L (As) in the stable condensate phase. The highest amount of trimethylarsine (121 μg/L (As)) was found in the pressurized condensate, along with trace amounts of non-identified higher alkylated arsines. Volatile arsenic species in natural gas and its related products cause concern with regards to environment, safety, occupational health and gas processing. Therefore, interest lies in a fast and simple field method for the determination of volatile arsenicals. Here, we use simple liquid and solid sorption techniques, namely absorption in silver nitrate solution and adsorption on silver nitrate impregnated silica gel tubes followed by total arsenic determination as a promising tool for field monitoring of volatile arsenicals in natural gas and gas condensates. Preliminary results obtained for the sorption-based methods show that around 70% of the arsenic is determined with these methods in comparison to volatile arsenic determination using GC-ICP-MS. Furthermore, an inter-laboratory- and inter-method comparison was performed using silver nitrate impregnated silica tubes on 14 different gas samples with concentrations varying from below 1 to 1000 μg As/m3 natural gas. The results obtained from the two laboratories differ in a range of 10 to 60%, but agree within the order of magnitude, which is satisfactory for our purposes.

Recent studies of methylmercury (MeHg) in rice have shown that rice grown on mercury contaminated soil contributes to the human MeHg intake similar to a fish diet. Trace levels of MeHg in biological samples are often determined via a complex multi-stage process following EPA method 1630. We developed a simple and cost effective method suited for food quality monitoring based on a simple sample preparation procedure and the subsequent analysis of the sample with online preconcentration via solid phase extraction high performance liquid chromatography cold vapor atomic fluorescence spectrometry (SPE-HPLC-CV-AFS). The reliability of this method for MeHg in rice and rice products in the low ppb range was investigated for 4 different rice product samples. At present, no CRM for MeHg in rice or rice products is available. Therefore we cross-validated our method against standard addition and species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICPMS), which showed no significant difference versus the external calibration with SPE-HPLC-CV-AFS. Potential species interconversion during sample preparation and measurement was ruled out by using a spike of isotopically enriched inorganic mercury. The SPE-HPLC-CV-AFS developed in our work has proven to be a robust, fast, cost efficient, competitive and reliable method for MeHg speciation in rice and rice products with a limit of detection of 0.12 µg kg−1 and a reproducibility comparable to the SS-ID-GC-ICPMS method which is sufficient for the determination of MeHg in the four market rice samples. The concentrations of MeHg ranged from 1.6 to 2.7 µg kg−1.

Volatile arsenic compounds in natural gas, existing in the form of trimethylarsine (TMAs), have been determined using gas cryo-trapping gas chromatography coupled to inductively coupled plasma-mass spectrometry (CT-GC-ICP-MS). The results from a number of different gas wells revealed a huge concentration spread ranging from below the detection limit of 0.2 up to 1800 µg/m3 TMAs (as As) in the gas. Due to the toxicity and corrosive nature of these arsines, they need near real time monitoring via a method that can easily be implemented on site, i.e. during gas exploitation. Here, we introduce a novel method which utilises silver nitrate impregnated silica gel tubes for quantitative chemotrapping of trimethylarsine (TMAs) from a natural gas matrix. Subsequent elution with hot nitric acid followed by online photo-oxidation hydride generation atomic fluorescence spectrometry (HG-AFS) is used for the determination of TMAs gas standards in nitrogen and natural gas samples, respectively. The chemotrapping method was validated using CT-GC-ICP-MS as a reference method. The recovery of arsenic from nitrogen or natural gas matrix ranged from 85 to 113% for a range of 20 to 2000 ng As. Trapping efficiency was >98%, from the methods LOD of 20 ng to 4.8 µg (absolute amount As) with sample sizes of 0.02 and 2 L gas. Method performance was established by comparing the results obtained for eight natural gas samples containing between 1 and 140 µg As/m3 with those achieved by the reference method (CT-GC-ICP-MS).