Cold Vapor Atomic Fluorescence Research Articles

Evaluation and risk assessment of heavy metals in King tuber mushroom in the contest of COVID-19 pandemic lockdown in Sokoto state, Nigeria

The aim of this study was to evaluate the degree of contamination and intake rates, as well as the risk of Lithium (Li), Arsenic (As), Cadmium (Cd), Mercury (Hg), and Lead (Pb) contained in wild species of King Tuber Mushroom (P. tuber-regium) collected pre-, post- and during the COVID-19 lockdown which is widely consumed in northwestern Nigeria; and to also assess their potential to accumulate some heavy metals, which comprises the linked consumer health hazards by assessing the risks to children, adolescents, and adults from cancer-causing and non-cancer-causing substances based on estimated weekly intake (EWI). After mineralization with acid, the concentrations were determined using Optical Emission Spectrometry with Inductively Coupled Plasma (OES-ICP), and Mercury (Hg) using Cold Vapor Atomic Fluorescence Spectrophotometer (CV-AFS). Moreover, the health risk assessment due to the ingestion of these elements through the consumption of P. tuberregium was estimated. The findings showed that concentrations of As, Pb, Cd, Li and Hg varied greatly within between 2018 and 2022, with levels higher in pre- and post- COVID-19, and lower during the COVID-19 lockdown. In descending order, the average content of these substrates and metals, was As > Pb > Cd > Li > Hg. Children, adolescents, and adults all had EWI values below the mushroom's provisional tolerable weekly intake (PTWIs). The consumption of P. tuber-regium harvested from the areas investigated, therefore, poses no toxicological or health risks to the inhabitants.

Health risk assessment for human mercury exposure from Cinnabaris-containing Baizi Yangxin Pills in healthy volunteers Po administration

BackgroundCinnabaris (α-HgS), a mineral traditional Chinese material medica, has been used in combination with other herbs manifesting some definite therapeutic effects for thousands of years. But the currently reported mercury poisoning incidents raised the doubts about the safety of Cinnabaris-containing traditional Chinese medicines (TCMs). Baizi Yangxin Pills (BZYXP) is a Cinnabaris-containing TCM widely used in clinical practice. This study evaluated the health risk of mercury exposure from BZYXP in healthy volunteers based on the total mercury and mercury species analysis of blood and urine after single and multiple doses of BZYXP. MethodsBlood pharmacokinetics and urinary excretion studies of mercury were compared between single (9 g, once daily) and multiple doses (9 g, twice daily, continued for 7 days) of BZYXP. The whole blood and urine samples were collected at the specific points or periods after the administration of BZYXP. The total mercury and mercury species in blood and urine samples were determined by cold vapor-atomic fluorescence spectrometry (CV-AFS) and HPLC-CV-AFS, respectively. ResultsThe mercury was excreted slowly and accumulated obviously after continuous exposure of BZYXP. Moreover, the well-known neurotoxin methylmercury (MeHg) was detected in blood samples after 7 days’ administration of BZYXP. In the urine samples, only Hg(II) was detected. Therefore, long-term use of BZYXP will cause mercury poisoning due to mercury's high accumulative properties and MeHg formation. ConclusionCinnabaris-containing TCMs such as BZYXP should be restricted to cases in which alternatives are available, and the blood mercury species profile should be monitored during the long-term clinical medication.

Bionanomaterial composed of Bradyrhizobium japonicum and graphene oxide for determination of mercury in water and fruit juice samples

In the present work, the synthesis of a novel hybrid bionanomaterial formed by the bacteria Bradyrhizobium japonicum (BJ) and the graphene oxide (GO) nanomaterial implemented in the miniaturized dispersive microsolid phase extraction technique (D-μ-SPE) was reported for the first time for the preconcentration and determination of Hg in water and fruit juice samples after a multivariate optimization. Selective Hg extraction was achieved by forming a complex with ammonium pyrrolidinedithiocarbamate (APDC) reagent and a multivariate study was performed to optimize the experimental conditions. The optimal Hg extraction conditions for 25 mL of sample were 3 mg of BJ@GO, NaNO3 at 1% (w/v), 6 min of vortex agitation and 9 min of centrifugation. For back extraction, 500 µL of 14 mol L−1 HNO3, 6 min of vortex agitation and 6 min of centrifugation were used followed by detection by cold vapor atomic fluorescence spectrophotometry (CV-AFS). Under optimized experimental conditions, an extraction efficiency of 98%, a detection limit of 0.08 µg L−1, a relative standard deviation of 3.5% (at 1 µg L−1 of Hg, n = 10), and a linear range of 0.26 - 4.0 µg L−1 were obtained. In addition, the sustainability of the method developed through the use of the Analytical GREEnness calculator (AGREE) software was evaluated, obtaining a greenness degree of 0.59. This work reports the first application of BJ@GO along with the D-μ-SPE technique for trace Hg determination water and fruit juice samples. In this way, this research work allows the exact and precise determination of low Hg concentrations in water and juice samples, which allows the evaluation of the contamination degree by this toxic metal in beverages widely consumed by the population.

Mercury content and elemental composition of fruticose lichens from Nahuel Huapi National park (Patagonia, Argentina): Time trends in transplanted and in situ grown thalli

Lichens have a unique structure involving the symbiosis of fungus and algae and can grow on almost any type of substrate. They absorb gases, water, nutrients and pollutants through their cortex, and thus are good indicators of environmental processes, enabling the biomonitoring of environmental pollutants. These organisms are widely distributed; however, as certain species do not occur in some areas, transplants are commonly used to monitor air pollution. In this study, transplants of the fruticose species Protousnea magellanica were set up at the EMMA Station (Global Mercury Observation System, GMOS) located at a suburban site of San Carlos de Bariloche city within Nahuel Huapi National Park (North Patagonia, Argentina). The transplants were used to assess the uptake of certain elements, particularly the accumulation of mercury. Periodic samplings of the transplanted species P. magellanica and the naturally occurring Usnea pusilla were performed concurrently at the experimental site over 483 days of experimental exposure. The elemental composition and concentration of the thalli of these species were determined by Neutron Activation Analysis in a nuclear reactor. Atmospheric mercury concentration (Gaseous Elemental Mercury, GEM) was monitored at the EMMA Station by an automated cold vapor atomic fluorescence system (Tekran 2537B). Mercury concentrations in the lichens were at least three orders of magnitude higher than atmospheric mercury levels (0.80–0.94 ng/m3, ppt), highlighting the accumulation capacity of these organisms. Concentrations found in P. magellanica thalli (0.080–0.327 μg/g dry weight, ppm) lay within the range of values reported previously in lichens from the Nahuel Huapi National Park with low anthropogenic impact. During experimental exposure both lichen species displayed the same trend in Hg content. Total Hg increased from T0 to T1 (day 25) and then decreased up to approximately T4 (day 385). In U. pusilla, the positive relationship between Hg content and lithophilic elements such as La, suggested preferential Hg uptake from airborne particles (deposited dust).

Local and landscape factors influencing mercury distribution in water, bottom sediment, and biota from lakes of the Araguaia River floodplain, Central Brazil

Mercury (Hg) is a chemical element widely present in the Earth's crust. However, its high toxicity and ability to accumulate in organisms and biomagnify through food chains characterize it as a global pollutant of primary control. We assessed total mercury concentrations ([THg]) in abiotic and biotic compartments from 98 floodplain lakes associated with the Araguaia River and six tributaries (Midwest Brazil). [THg] quantification in water was performed by cold vapor atomic fluorescence spectroscopy. [THg] in bottom sediment was assessed using cold vapor generation atomic absorption spectrophotometry, while [THg] in macrophyte, periphyton, and plankton were quantified by thermal decomposition atomic absorption spectrometry. Hotspots of [THg] in water, bottom sediment, and macrophytes were determined in areas impacted by pasture and urban areas. In contrast, hotspots of [THg] in periphyton and forest fires were determined in preserved areas downstream. [THg] in plankton did not show a clear spatial distribution pattern. The mean bioaccumulation factor order was plankton (2.3 ± 1.8) > periphyton (1.3 ± 0.9) > macrophytes (0.7 ± 0.4) (KW = 55.09, p < 0.0001). Higher [THg] in water and bottom sediment were associated with high pH (R2adj = 0.118, p = 0.004) and organic matter (R2adj = 0.244, p < 0.0001). [THg] in macrophytes were positively influenced by [THg] in water (R2adj = 0.063, p = 0.024) and sediment (R2adj = 0.105, p = 0.007). [THg] in periphyton are positively related to forest fires (R2adj = 0.156, p = 0.009) and [THg] in macrophytes (R2adj = 0.061, p = 0.03) and negatively related to lake depth (R2adj = 0.045, p = 0.02). The transfer of Hg from water and sediment to the biota is limited. However, the progressive increase of the bioaccumulation factor between macrophyte, periphyton, and plankton may indicate Hg biomagnification along the food chain of the Araguaia River floodplain.

Optimisation of distillation as an isolation method for the determination of low methylmercury concentrations in urine samples

Methylmercury (MeHg) speciation in urine requires a robust, reproducible and sensitive technique that enables reliable measurements in limited sample volumes. Conventional MeHg extraction by acid digestion allows for processing of only small amounts of urine digest, making accurate MeHg determination in low-concentration samples virtually impossible. Distillation has been proven as an efficient isolation method with very low detection limits for measuring MeHg in water samples; therefore, in this study, it was optimised for urine samples. Combined with aqueous phase ethylation, purging with nitrogen, preconcentration on Tenax trap, isothermal gas chromatography and cold vapour atomic fluorescence detection, distillation achieved high and repeatable urine spike recoveries of 94% ± 7%. Larger measured aliquot volume led to a significantly lower limit of detection (LOD) for distillation compared with acid digestion (1.1 versus 5.5 pg g−1 urine). Thirty-two general population urine samples were analysed using both methods, and the results were compared. Distillation led to better separation of MeHg from inorganic Hg and the matrix. Good correlation was observed between the results obtained by the two methods for samples with MeHg concentrations above 10 pg g−1 urine (slope = 0.9492, R2 = 0.9879). For samples below this MeHg concentration, distillation was superior, enabling the measurement of MeHg in 9 out of 12 urine samples that were below the LOD of acid digestion. Distillation had significantly lower measurement uncertainty, particularly in the low-concentration samples, where the expanded combined standard uncertainty of the acid digestion method reached as high as 43.2% (k = 2), predominantly owing to poor sample repeatability.

The transformation of soil Hg oxidation states controls elemental Hg release in the greenhouse with applying organic fertilizer

The foliage vegetables cultivated in greenhouse of Hg-contaminated regions suffer from severe Hg contamination issues because of soil elemental Hg (Hg(0)) release. Application of organic fertilizer (OF) is the indispensable part of farming, but its influences on soil Hg(0) release are unclear. A new method of thermal desorption coupled with cold vapor atomic fluorescence spectrometry was developed to measure transformations of Hg oxidation states to elucidate the impact mechanism of OF on Hg(0) release process. Our results showed that the soil Hg(0) concentrations can directly determine its release fluxes. The application of OF causes that oxidizing reactions of Hg(0)/Hg(I) and Hg(I)/Hg(II) are excited; then soil Hg(0) concentrations decreases. Besides, the elevated soil organic matter by amending OF can complex with Hg(II), resulting in that the reductions of Hg(II) to Hg(I) and Hg(0) are inhibited. Additionally, the OF can directly adsorb soil Hg(0), decreasing the removability of Hg(0). Subsequently, the application of OF can significantly inhibit soil Hg(0) release, resulting in a pronounced decrease in interior atmospheric Hg(0) concentrations. Our results provide a novel perspective for enriching the fate of soil Hg that transformation of soil Hg oxidation states plays a crucial role in affecting soil Hg(0) release process.

Accumulation and distribution of mercury in agricultural soils, food crops and associated health risks: A case study of Shenda gold mine-Geita Tanzania

Contamination of the environment and foodstuff by potentially harmful elements (PHEs) has become a serious concern due to the associated health risks to the population. In the present study total mercury (Hg) levels in soil and food crops from farms around Shenda gold mine in Geita Tanzania was determined by Cold Vapor Atomic Fluorescence Spectrometry (CVAFS). Generally, it was found that there was significant different of Hg content in soil and food crops (P < 0.05) among studied sites. The total Hg concentrations determined were in the ranges of; soils (0.003-0.1220 mg/kg), rice (0.0752-0.1587 mg/kg) and vegetables (0.0556-0.3439 mg/kg) all measurement were based on dry weight basis (dw). Total Hg levels in soil were compared with the maximum allowable concentration (MAC) set by Tanzania Bureau of Standards (TBS) and United Kingdom (UK). All studied soil samples were within acceptable range (2 mg/kg) set by TBS and UK (1 mg/kg). Total Hg contents in food crop samples were compared with Chinese MAC of Hg (0. 01 and 0.02 mg/kg for leafy vegetables and grains respectively in a fresh weight basis). It was observed that Hg contents in potato leaves, pumpkin leaves and Chinese cabbage were within the MAC while Hg levels in cassava leaves and rice grains exceeded the MAC. In addition, Hg associated health risks to consumers of contaminated foods for residents around Shenda gold mine were estimated. The estimated weekly intake (EWI) of Hg due to consumption of rice grain was above the provisional tolerable weekly intake (PTWI) set by FAO/WHO (1.6 mg/kg bw/week) while the EWI due to consumption of leafy vegetables were below the PTWI. Target hazard quotient (THQ) was < 1 due to consumption of vegetables while THQ value for rice was >1, indicating a potential non-carcinogenic risk to adult population from the consumption of rice grain from the study area. Therefore, people living near Shenda goldmine might be potential victim of Hg accumulation in soil and food crops, thus necessary management options have to be in place.

Total mercury and fatty acids content in selected fish marketed in Quito - Ecuador. A benefit-risk assessment.

Total mercury and fatty acids contents were determined in muscles of croaker, snapper, dolphinfish, blue marlin, and shark, from different markets in the Metropolitan District of Quito, Ecuador. Fifty-five samples were collected and analyzed for total mercury using cold vapor atomic fluorescence spectrometry, and the fatty acids were analyzed using gas chromatography equipped with a flame ionization detector. The lowest total mercury levels were found in snapper [0.041µg·g-1 wet weight (ww)] while blue marlin showed the highest (5.883µg·g-1 ww). EPA +DHA ranged from 1.0mg·g-1 in snapper to 2.4mg·g-1 in shark. A high omega-3/omega-6 ratio was found for all fish types; however, the HQEFA for the benefit-risk ratio was above 1, suggesting an evident risk to human health. Based on our results, consumption of croaker and dolphinfish is recommended up to one serving per week, considering the importance of EFAs intake and avoiding fish with elevated MeHg content. Therefore, Ecuadorian authorities could enhance public standards for seafood safety and develop consumer advice for pregnant women and young children to determine good fish choices or those to avoid.

Total mercury determination in bivalves Anadara tuberculosa sold in open markets from Quito, Ecuador

This study aimed to quantify the amount of total mercury in bivalves Anadara tuberculosa supplied from Esmeraldas Province and sold in markets in the Metropolitan District of Quito, Ecuador. The determined total mercury concentration was compared to the permissible limits established by the European Commission and World Health Organization-Food and Agriculture Organization and health risk subsequently assessed. Sampling was conducted in five open markets and involved collecting fifteen specimens from each market. Total mercury was measured through cold vapor atomic fluorescence spectrophotometry. Results showed that samples did not exceed the total mercury threshold value (0.5 mg kg−1). However, samples of Anadara tuberculosa from the Ofelia market, which receives fresh products from Eloy Alfaro canton, contained the highest mean levels of mercury contamination, 0.055 mg kg−1. This result could be associated to the influence of illegal mining activity in this area. In addition, methylmercury potential non-carcinogenic risk for consumers exceeded the threshold limit (>1) established by the US Environmental Protection Agency. The daily consumption rate (Rclim) was determined to be 26.61–38.50 g for a child weight of 14.5 kg, and 128.44–185.84 g for an adult weight of 70 kg. Thus, consuming a higher amount of Anadara tuberculosa could negatively affect human health.

Functionalized graphene quantum dots obtained from graphene foams used for highly selective detection of Hg2+ in real samples

Here we report the use of graphene quantum dots (GQDs), obtained from 3D graphene foam, functionalized with 8-hydroxyquinoline (8-HQ) for the sensitive and selective detection of Hg2+ via front-face fluorescence. The great surface area and active groups within the GQDs permitted the functionalization with 8-HQ to increase their selectivity toward the analyte of interest. The fluorescence probe follows the Stern-Volmer model, yielding a direct relationship between the degree of quenching and the concentration of the analyte. Diverse parameters, including the pH and the use of masking agents, were optimized in order to improve the selectivity toward Hg2+ down to a limit of detection of 2.4 nmol L−1. It is hereby demonstrated that the functionalized GQDs work perfectly fine under adverse conditions such as acidic pH and in the presence of a large number of cationic and anionic interferences for the detection of Hg2+ in real samples. Parallel measurements using cold vapor atomic fluorescence spectrometry also demonstrated an excellent correlation with the front-face fluorescence method applied here for real samples including tap, river, underground, and dam waters.

Description of a Dimethylmercury Automatic Analyzer for the High-Resolution Measurement of Dissolved Gaseous Mercury Species in Surface Ocean Waters.

Our understanding of the significance of dimethylmercury (DMHg) to the mercury (Hg) global ocean biogeochemical cycle is unclear because of the lack of detailed DMHg measurements in the water column. To our knowledge, 30 years of published studies have generated no more than 200 DMHg data points in the ocean surface waters and marine boundary layer (MBL). To improve the precision and reduce the uncertainty in determining DMHg in surface seawater, we developed a simple and robust DMHg automatic analyzer (DAA). This DAA system couples the main sampling and analytic steps, including a continuous flow chamber, with dual Carbotrap preconcentration, a gas chromatographic column, a cold vapor atomic fluorescence spectrometry, and a data logger for signal integration. We compared the operation, performance, and reproducibility between our DAA and the traditional manual analytic method. Its advantages include the ease of operation, the high time resolution and precision (30 min sampling and <5% relative variation), and long-term stability (2 weeks). The DAA can determine DMHg in both the MBL and surface seawater. The estimated detection limits for DMHg with the DAA in the atmosphere and in surface seawater are 10 pg/m3 and 0.2 fM, respectively. The successful DAA field measurement in coastal waters indicates that it can help detect the low DMHg concentration in surface seawater, and the time series DMHg data helped our understanding of the DMHg behavior (sources and sinks) and its flux into the MBL. The comparison of DMHg concentration in various oceans also suggests that the coastal region had the lowest averaged DMHg, up to an order of magnitude lower than other ecosystems.

Mercury in Dried Market Fish of Hong Kong and San Francisco: Human Health Implications

Asian, Asian Pacific Islanders, and Asian American residents of San Francisco have higher exposure to mercury and the associated health risks associated with methylmercury toxicity from fish consumption than other demographics across the United States. Due to their higher annual fish consumption, Hong Kong Chinese residents have elevated risks to methylmercury exposure. Objectives: We investigate samples of dried market fish from San Francisco and from Hong Kong as potential sources of mercury contamination in fish commonly consumed by Asian and Asian American residents. Methods: We analyze 81 samples of dried market fish from San Francisco and Hong Kong for mercury concentration using Inductively Coupled Plasma Emission Spectrograph and Processing Cold Vapor Atomic Fluorescence Spectrometry. We binned into market categories, trophic level, and habitat type for statistical analysis. Results: No significant difference was observed in the mercury levels of samples between San Francisco and Hong Kong (p-value = 0.47). Dried samples did show higher rates of mercury than wet samples reported by the FDA. Data from dried market fish samples also show evidence of bioaccumulation: the concentration of toxins in higher trophic levels of fish (p-value &lt; 0.01). Eliminating apex predators, nearly all samples of fish from both locations and from lower trophic levels had levels below the lowest health advisory thresholds of 0.5 ppm methylmercury by weight. Discussion: Dried fish samples from markets in San Francisco and Hong Kong showed mercury levels with the potential to exceed guidelines set by the EPA and the EFSA, but consumption rates are lacking to know if this threshold is actually being exceeded by consumers. We make recommendations regarding the health risks of dried market fish and of consuming or avoiding fish from certain trophic groups.

Composition of trace residues from the contents of 11th-12th century sphero-conical vessels from Jerusalem.

The residues from the internal surface of four archaeological ceramic sherds, excavated from the Armenian Gardens, Jerusalem were analysed to characterise the contents of the original vessel. The sherds derive from four small, thick-walled, sphero-conical vessels recovered from a destruction layer, dating between the 11th and 12th century, Jerusalem. The residue has been analysed using light microscopy, biochemical characterisation, gas chromatography mass spectroscopy, inductively coupled plasma atomic emission spectroscopy and cold vapour atomic fluorescence spectrometry. This analysis established the presence of various compounds including fatty acids and notable levels of mercury, sulphur, aluminium, potassium, magnesium, nitrates and phosphorous. The contents and probable functions of the four vessels were characterised from the residues on these sherds as different from each other, reflecting their different decoration, manufacture and ceramic typologies. One of these vessels contains residue that indicate the vessel held oils. The residue of the second vessel is consistent with either scented materials or medicinal contents, while a third probably contained medicinal material. The unique fourth sherd is from a stoneware sphero-conical vessel with very thick walls, no decoration and the residue supports the possibility it was used for the storage of chemicals or may have held the chemical ingredients for an explosive device, consistent with a medieval grenade. This residue analysis of Mamluk sphero-conical vessels provides insight into luxury items, medicines, technology and trade in medieval Jerusalem.

Mercury speciation in estuarine water using dithiol-based magnetic solid-phase extraction and cold vapor atomic fluorescence spectrometry

In this work, a method for mercury speciation using magnetic nanoparticles (MNPs) coated with dithiol and detection by cold vapor atomic fluorescence spectrometry (CV AFS) was developed. The magnetic Fe3O4 nanoparticles were coated with Al2O3 and sodium dodecyl sulfate (SDS) and functionalized with 1,3,4-thiadiazole-2,5-dithiol (TDT). The resulting functionalized MNPs (FMNPs, Fe3O4@Al2O3-TDT) were dispersed in the water samples, and the sorption performance with different mercury species was investigated. Once retained on the surface of Fe3O4@ Al2O3-TDT MNPs, the mercury species were magnetically separated from the sample and eluted with HCl. The organic mercury species were oxidized employing KBr-KBrO3 (100 and 17 mM, respectively) in an acid medium (HCl 1.0 M), and the results were expressed considering the total inorganic mercury concentration. It was successfully applied in mercury speciation analysis in the estuarine water, followed by CV AFS determination. In the proposed method under optimal conditions (pH 6), inorganic mercury was quantified in a linear range from 10 to 2000 ng L−1, with a limit of detection of 0.55 ng L−1, relative standard deviation (RSD) < 1.62%, and an enrichment factor of twelve. The recoveries in spiked estuarine water samples ranged from 94 to 106% for Hg(II), 85–91% for MeHg, 83–94% for EtHg, and 84–95% (PhHg) using two levels of concentration (100 and 500 ng L−1). The method is accurate, precise, and efficiently applied in mercury species determination in a complex matrix without laborious and time-consuming sample preparation.

Simple Acid Digestion Procedure for the Determination of Total Mercury in Plankton by Cold Vapor Atomic Fluorescence Spectroscopy.

Plankton, at the bottom of the food web, play a central role in the entry of mercury into the aquatic biota. To investigate their role in mercury uptake, reliable analytical procedures for Hg analysis are highly sought. Wet digestion procedures for determining total mercury in different biological matrices have been established since years, however only few studies focused on planktonic samples. In the present work, a simple and cost-effective wet digestion method was developed for the determination of total mercury in samples of small plankton material using a cold vapor atomic fluorescence spectroscopy (CVAFS). The optimization of the digestion method was achieved by using glass vessels with Teflon caps, low amount of acids (3 mL w/w 65% HNO3 or 3 mL 50% v/v HNO3), a constant temperature of 85 °C, the presence and absence of pre-ultrasound treatment, and a continuous digestion period (12 h). Certified reference materials IAEA-450 (unicellular alga Scenedesmus obliquus) and BRC-414 (plankton matrix) were used to optimize and validate the digestion method. The recovery efficiency of the proposed method for IAEA-450 and BCR-414 (3.1 mg and 21.5 mg) ranged between 94.1 ± 7.6% and 97.2 ± 4.6%. The method displayed a good recovery efficiency and precision for plankton matrices of low size. Thus, allowing better digestion of planktonic samples for mercury analysis using CVAFS techniques.

Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils.

We examined the composition and spatial correlation of sulfur and mercury pools in peatland soil profiles by measuring sulfur speciation by 1s X-ray absorption near-edge structure spectrocopy and mercury concentrations by cold vapor atomic fluorescence spectroscopy. Also investigated were the methylation/demethylation rate constants and the presence of hgcAB genes with depth. Methylmercury (MeHg) concentration and organic disulfide were spatially correlated and had a significant positive correlation (p < 0.05). This finding is consistent with these species being products of dissimilatory sulfate reduction. Conversely, a significant negative correlation between organic monosulfides and MeHg was observed, which is consistent with a reduction in Hg(II) bioavailability via complexation reactions. Finally, a significant positive correlation between ester sulfate and instantaneous methylation rate constants was observed, which is consistent with ester sulfate being a substrate for mercury methylation via dissimilatory sulfate reduction. Our findings point to the importance of organic sulfur species in mercury methylation processes, as substrates and products, as well as potential inhibitors of Hg(II) bioavailability. For a peatland system with sub-μmol L-1 porewater concentrations of sulfate and hydrogen sulfide, our findings indicate that the solid-phase sulfur pools, which have a much larger sulfur concentration range, may be accessible to microbial activity or exchanging with the porewater.

Field determination of inorganic mercury in seawaters by a portable dual-channel and purge-and-trap system with atomic fluorescence spectrometry

ABSTRACT An on-line flow injection mercury analyser (FIMA) for inorganic mercury (Hg) analysis in environmental waters is presented. The FIMA is a portable dual-channel and purge-and-trap system combining aqueous reduction with stannous chloride (SnCl2), two-stage gold (Au) amalgamation, thermal desorption of Hg0 and final detection with cold vapour atomic fluorescence spectrometry (CVAFS). Simultaneous on-line operations of sample loading and analysis make analytical throughput and accuracy improved and contamination eliminated. Results of system optimisation and reliability regarding the determination of inorganic Hg2+ are described. Analytical performances of both channels were the same in terms of data reliability. Low procedural blanks were obtained from laboratory and field trip (≤5 pg, n = 30). Excellent calibrations (r2 > 0.99) with a high precision and good stability (RSD <5%, n = 30) were obtained. Detection limits and reproducibility of the methods have been estimated as ≤0.05 ng L−1 and <5% (0.5 ng L−1, n = 30). The system was finally validated by measurements comparison of the two channels (r2 > 0.98), and analysis of a certified reference material (coastal seawater BCR-579, recoveries 101 ± 4%, n = 10). Overall, a sample throughput of ~10 samples per hour with two-channel detections of FIMA can be achieved. The onboard analysis of inorganic Hg species (e.g. elemental, reactive, and total Hg) in surface seawaters of the East China Sea (ECS) are also successfully achieved. The portable FIMA is fast, easy, and robust for reliable monitoring of Hg in natural seawaters.

An Analytical Method for the Biomonitoring of Mercury in Bees and Beehive Products by Cold Vapor Atomic Fluorescence Spectrometry.

Bees and their products are useful bioindicators of anthropogenic activities and could overcome the deficiencies of air quality networks. Among the environmental contaminants, mercury (Hg) is a toxic metal that can accumulate in living organisms. The first aim of this study was to develop a simple analytical method to determine Hg in small mass samples of bees and beehive products by cold vapor atomic fluorescence spectrometry. The proposed method was optimized for about 0.02 g bee, pollen, propolis, and royal jelly, 0.05 g beeswax and honey, or 0.1 g honeydew with 0.5 mL HCl, 0.2 mL HNO3, and 0.1 mL H2O2 in a water bath (95 °C, 30 min); samples were made up to a final volume of 5 mL deionized water. The method limits sample manipulation and the reagent mixture volume used. Detection limits were lower than 3 µg kg−1 for a sample mass of 0.02 g, and recoveries and precision were within 20% of the expected value and less than 10%, respectively, for many matrices. The second aim of the present study was to evaluate the proposed method’s performances on real samples collected in six areas of the Lazio region in Italy.

Metals and metalloids in green turtle hepatic tissue (Chelonia mydas) from Santos Basin, Brazil

Metal and metalloid concentrations in the liver tissue of green turtles (Chelonia mydas) stranded on the Brazilian coast (n = 506) were studied using inductively coupled plasma mass spectrometry and cold vapor atomic fluorescence spectrometry. The influences of occurrence registers (date and location) and biological characteristics (sex, age, and developmental stage) were assessed, as well as the temporal influences of oil exploration and production activities. The mean concentrations of Cd, Cu, Mn, Zn, and Hg were the highest reported for the liver of C. mydas on the Brazilian coast. The mean element concentrations followed the order: Cu > Zn > Cd > Mn > As > Hg > Mo > Pb > V > Ni > Ba > Cr. Further, significant differences (p < 0.05) were observed for Hg between the sexes (males > females) and for As, Cu, Pb, Mo, and V between young individuals and older individuals (≥11 years), suggesting a relationship between the dietary shift inherent to green turtle development. These results were corroborated by the curved carapace length (CCL) data, wherein individuals residing in coastal areas (CCL > 50 cm) presented higher concentrations of Cu, Pb, Mo, Zn, Ba, and V than those in the oceanic stage (CCL < 30 cm). The opposite pattern was observed for As and Hg. The influences of spatial autocorrelation (Moran Index) at a global scale and oil production activities on the element concentrations were not observed. However, five hotspots of high metal concentrations were identified via a local spatial autocorrelation (local indicator of spatial association), existing predominantly in a region of heavy anthropic activity within the sampling area. Further, baseline element concentrations were established at the 95% confidence level. Overall, the developmental stage, which is related to feeding habits, had an expressive influence on element concentrations.