Quantitative and qualitative impacts of nitric acid digestion on microplastic identification via FTIR and Raman spectroscopy, implications for environmental samples.

Quantification and characterization of microplastics, synthetic polymers less than 5 mm in diameter, requires extraction methods that can reduce non-plastic debris without loss or alteration of the polymers. Nitric acid has been used to extract plastic particles from zooplankton and other biota because it completely digests tissue and exoskeletons, thus reducing interferences. While the impact of acid digestion protocols on several polymers has been demonstrated, advice for quantifying microplastic and interpreting their spectra following nitric acid digestion is lacking. Fourier transform infrared (FTIR) and/or Raman spectroscopy was performed on plastics from > 50 common consumer products (including a variety of textiles) pre- and post-nitric acid treatment. The percent match and assigned polymer were tabulated to compare the accuracy of spectral identification before and after nitric acid digestion via two open spectral analysis software. Nylon-66, polyoxymethylene, polyurethane, polyisoprene, nitrile rubber, and polymethyl methacrylate had ≥ 90% mass loss in nitric acid. Other less-impacted polymers changed color, morphology, and/or size following digestion. Thus, using nitric acid digestion for microplastic extraction can impact our understanding of the particle sizes and morphologies ingested in situ. Spectral analysis results were compiled to understand how often (1) the best-hit matches were correct (30-60% of spectra), (2) the best-hit matches exceeding the (arbitrary) threshold of 65% match were correct (53-78% of spectra), and (3) the best-hit matches for anthropogenic polymers were incorrectly identified as natural polymers (12-15% of spectra). Based on these results, advice is provided on how nitric acid digestion can impact microplastics as well as spectral interpretation.

Coupling of nitric acid digestion and anion-exchange resin separation for the determination of methylmercury isotopic composition within organisms.

Isotope ratios of methylmercury (MeHg) within organisms can be used to identify sources of MeHg that have accumulated in food webs, but these isotopic compositions are masked in organisms at lower trophic levels by the presence of inorganic mercury (iHg). To facilitate measurement of MeHg isotope ratios in organisms, we developed a method of extracting and isolating MeHg from fish and aquatic invertebrates for compound-specific isotopic analysis involving nitric acid digestion, batch anion-exchange resin separation, and pre-concentration by purge and trap. Recovery of MeHg was quantified after each step in the procedure, and the average cumulative recovery of MeHg was 93.4 ± 2.9% (1 SD, n = 28) for biological reference materials and natural biota samples and 96.9 ± 1.8% (1 SD, n = 5) for aqueous MeHgCl standards. The amount of iHg impurities was also quantified after each step, and the average MeHg purity was 97.8 ± 4.3% (1 SD, n = 28) across all reference materials and natural biota samples after the final separation step. Measured MeHg isotopic compositions of reference materials agreed with literature values obtained using other MeHg separation techniques, and MeHg isotope ratios of aqueous standards, reference materials, and natural biota samples were reproducible. On average, the reproducibility associated with reference material process replicates (2 SD) was 0.10‰ for δ202MeHg and 0.04‰ for Δ199MeHg. This new method provides a streamlined, reliable technique that utilizes a single sample aliquot for MeHg concentration and isotopic analysis. This promotes a tight coupling between MeHg concentration, %MeHg, and Hg isotopic composition, which may be especially beneficial for studying complex food webs with multiple isotopically distinct sources of iHg and/or MeHg.

[The use of ion chromatography for the determination of volatile inorganic acids in workplace air]. / Zastosowanie chromatografii jonowej do oznaczania lotnych kwasów nieorganicznych w powietrzu na stanowiskach pracy.

BACKGROUND: The presence of inorganic acids in the air poses a threat to the health of workers. Volatile inorganic acids, e.g., hydrochloric acid, hydrobromic acid and nitric acid, may cause respiratory, eye and skin irritation. The presented method uses ion chromatography to determine the concentrations of hydrochloric, hydrobromic and nitric acids in air samples. MATERIAL AND METHODS: The method is based on the collection of airborne volatile acids on impregnated quartz fiber filter, extraction of acids with deionized water, and analysis by ion chromatography with conductivity suppression. The separation was performed on the Dionex IonPac™ AS22 (4 × 250 mm) column for trace anion analysis. The carbonate/bicarbonate eluent was maintained at an isocratic flow rate of 1.2 ml/min. The calibration standard solutions have been covering the range of 0.2-5 mg/l of chloride, bromide and nitrate. RESULTS: The specified chromatographic conditions enable selective measurement of chloride, bromide and nitrate anions. The obtained mass concentration of each anion, having factored in the sample dilution, the conversion factor (to convert anion concentration to acid) and the volume of the air sample, allows the calculation of acid concentrations in the analyzed air. CONCLUSIONS: This method makes it possible to determine the concentration of hydrochloric acid, hydrobromic acid and nitric acid in the workplace air within the concentration range corresponding to 0.1-2 times the exposure limit value in Poland. The method meets the criteria for the performance of procedures for the measurement of chemical agents, listed in PN-EN 482. This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering. Med Pr. 2022;73(4):337-47.

PM2.5 in Carlsbad Caverns National Park: Composition, sources, and visibility impacts.

Carlsbad Caverns National Park in southeastern New Mexico is adjacent to the Permian Basin, one of the most productive oil and gas regions in the country. The 2019 Carlsbad Caverns Air Quality Study (CarCavAQS) was designed to examine the influence of regional sources, including urban emissions, oil and gas development, wildfires, and soil dust on air quality in the park. Field measurements of aerosols, trace gases, and deposition were conducted from 25 July through 5 September 2019. Here, we focus on observations of fine particles and key trace gas precursors to understand the important contributing species and their sources and associated impacts on haze. Key gases measured included aerosol precursors, nitric acid and ammonia, and oil and gas tracer, methane. High-time resolution (6-min) PM2.5 mass ranged up to 31.8 µg m-3, with an average of 7.67 µg m-3. The main inorganic ion contributors were sulfate (avg 1.3 µg m-3), ammonium (0.30 µg m-3), calcium (Ca2+) (0.22 µg m-3), nitrate (0.16 µg m-3), and sodium (0.057 µg m-3). The WSOC concentration averaged 1.2 µg C m-3. Sharp spikes were observed in Ca2+, consistent with local dust generation and transport. Ion balance analysis and abundant nitric acid suggest PM2.5 nitrate often reflected reaction between nitric acid and sea salt, forming sodium nitrate, and between nitric acid and soil dust containing calcium carbonate, forming calcium nitrate. Sulfate and soil dust are the major contributors to modeled light extinction in the 24-hr average daily IMPROVE observations. Higher time resolution data revealed a maximum 1-hr extinction value of 90 Mm-1 (excluding coarse aerosol) and included periods of significant light extinction from BC as well as sulfate and soil dust. Residence time analysis indicated enrichment of sulfate, BC, and methane during periods of transport from the southeast, the direction of greatest abundance of oil and gas development.Implications: Rapid development of U.S. oil and gas resources raises concerns about potential impacts on air quality in National Parks. Measurements in Carlsbad Caverns National Park provide new insight into impacts of unconventional oil and gas development and other sources on visual air quality in the park. Major contributors to visibility impairment include sulfate, soil dust (often reacted with nitric acid), and black carbon. The worst periods of visibility and highest concentrations of many aerosol components were observed during transport from the southeast, a region of dense Permian Basin oil and gas development.

Development of an eco-friendly sample preparation protocol for metal determination in food samples: an oxygen pressurized single reaction chamber using diluted nitric acid.

Many efforts have been recently made to improve the digestion efficiency by using powerful equipment or by using an auxiliary reagent. In this work, an alternative method is reported, which explores a digestion system based on a single reaction chamber (SRC) technology pressurized with O2 for reducing the amount of acid, without impairing the digestion efficiency. Before digestion, the system was pressurized with compressed air (20 bar, 20% O2) while the temperature was evaluated from 180 up to 270 °C. The procedure was also carried out under O2 pressure (20 bar). For each temperature several acid concentrations were evaluated (0.1 to 3 mol L-1 HNO3), being possible to correlate the effectiveness of each acid concentration with temperature. The proposed method was applied to the simultaneous digestion of several organic matrices with variable content of fat, protein, and carbohydrate (whole milk powder, bovine liver, parsley, and linseed). The residual carbon content was lower than 4% (C lower than 200 mg L-1 in digests), showing the high digestion efficiency of the proposed approach. Up to 250 mg of all food matrices were digested using a sub-stoichiometric amount of HNO3 (1 mol L-1 solution), which was only achieved due to the use of O2 as an auxiliary reagent. Barium, Ca, Cu, Fe, K, Mg, Mn, Na, Sr, and Zn were determined by ICP-OES, and the accuracy was better than 95% for standard reference materials of corn bran, whole milk powder, and bovine liver. It is an important feature, being in agreement with green chemistry recommendations because very low amounts of reagents are required for sample digestion, as well as low amounts of residues are generated.

[Atmospheric Nitrogen Dioxide, Nitric Acid, Nitrate Nitrogen Concentrations, and Wet and Dry Deposition Rates in a Double Rice Region in Subtropical China].

Nitrogen dioxide (NO2) and nitric acid (HNO3) are nitrogen-containing acidic gases in the atmosphere, and they are important precursors of nitrate in aerosol and rainwater. The emission intensity of atmospheric nitrogen oxides is high in the subtropical region of China, but the concentrations and deposition rates of atmospheric nitrogen dioxide, nitric acid, particulate nitrate-nitrogen (NO3--Np), and rainwater nitrate-nitrogen (NO3--Nr) in a double rice region in subtropical China are still unclear,. In this study, the atmosphere concentrations of NO2-N, HNO3-N, NO3--Np in PM10, and NO3--Nr and related meteorological parameters were simultaneously monitored in a typical double rice region within a subtropical hilly region of China, with the aim of determining the characteristics and influencing factors of NO2-N, HNO3-N, NO3--Np, and NO3--Nr concentrations and quantifying the wet and dry deposition rates. The results showed that the annual mean concentrations of NO2-N, HNO3-N, NO3--Np, and NO3--Nr were 4.2 µg·m-3, 0.7 µg·m-3, 4.0 µg·m-3, and 1.0 mg·L-1, respectively, and the deposition rates were 1.5, 3.2, 2.3, and 6.1 kg·hm-2, respectively. The NO2-N concentrations were negatively correlated with air temperatures, and the HNO3-N concentrations were negatively correlated with wind speeds. TheNO3--Np concentrations were negatively correlated with air temperatures, positively correlated with NO2-N concentrations, but not significantly correlated with HNO3-N concentrations, thus indicating that NO2-N concentrations were an important limiting factor forNO3--Np pollution in this study area. The NO3--Nr concentrations were negatively correlated with rainfall, as well as the concentrations of HNO3-N and NO3--Np. The annual total dry and wet depositions of the atmospheric NO2-N, HNO3-N, NO3--Np, and NO3--Nr were 13.0 kg·hm-2, which indicates that these compounds are important sources of nitrogen in paddy fields and may have significant impacts on paddy fields and surrounding ecosystems.

Carbazole and fluorene polyaniline derivatives: Synthesis, properties and application as multiple stimuli-responsive fluorescent chemosensor.

Development of conjugated polymers with fluorescence sensing characteristics has received close attention from researchers in fields of environmental protection, biosensing and toxins detection on food. In this paper, novel polyaniline derivatives of poly(9-methyl-9H-carbazol-3-amine) and poly(9,9-dihexyl-9H-fluoren-2-amine) are prepared by facile chemical polymerization. Then they are characterized with NMR (Nuclear Magnetic Resonance), GPC (Gel Permeation Chromatography), XRD (X-Ray Diffraction), FT-IR (Fourier Transform Infrared spectroscopy), FL (Fluorescence spectrometry) and UV-vis (Ultraviolet-visible spectroscopy) characterizations and further applied to the fluorescence detection of different acids and amines. Moreover, the obtained poly(9-methyl-9H-carbazol-3-amine) displays excellent fluorescence properties in the detection for both acids and amines. Besides, this poly(9-methyl-9H-carbazol-3-amine) can not only be used for fluorescence detection in solution, but also can be prepared into solid state and applied in the gas phase fluorescence detection. This work has greatly expanded the scope of application to these polyaniline derivatives materials, opening a new path for the researches on multi-functional chemosensor.

Zinc and iron complexes of oleanolic acid, (OA) attenuate allergic airway inflammation in rats.

Oleanolic acid (OA) is a hydroxyl pentacyclic triterpene acid (HTAs) used in various ailments. Inflammatory diseases may be profoundly influenced by iron (Fe) and zinc (Zn) status. We studied the anti-asthmatic effects of two metal complexes (Fe and Zn) of OA in the ovalbumin (OVA)-induced rat model. Delayed type hypersensitivity (DTH) was measured. Total and differential leucocyte count was done in blood as well as bronchoalveolar lavage fluid (BALF). The mRNA expression levels of pro-inflammatory cytokines were measured in lung tissue by reverse transcription polymerase chain reaction. The levels of cyclooxygenase-2 (COX-2), immunoglobulin E (IgE) and 5-lipoxygenase (5-LOX) were estimated by enzyme linked immunosorbent assay. Splenocyte proliferation was performed through BrdU uptake method and nitric oxide levels were measured by colorimetric assay kit. The acute toxicity study was also done for the complexes. The asthmatic group developed allergic airway inflammation shown by increased DTH and inflammatory markers in blood and BALF. OA + Fe and OA + Zn displayed significant decrease in DTH, NO, expression of IL-4, 5, 13, 17, toll-like receptor-2, nuclear factor-kappa B and tumor necrosis factor-α; serum IgE, COX-2, and 5-LOX. The metal complexes also attenuated OVA-stimulated splenocyte proliferation. While no hepatotoxic or nephrotoxic potential was shown by OA + Fe and OA + Zn. Our findings indicate that both OA + Fe and OA + Zn possess significant anti-asthmatic effect which may be ascribed to its immunomodulatory and anti-inflammatory features.

Background element content in the lichen Pseudevernia furfuracea: a comparative analysis of digestion methods.

In bioaccumulation studies, the interpretation of pollutant contents in the target biomonitor has to be performed by assessing a deviation from an unaltered reference condition. A common strategy consists in the comparison with background element content (BEC) values, often built up by uncritically merging methodologically heterogeneous data. In this respect, the acid digestion of samples was identified as a major step affecting BEC data. Here, the analytical outcomes of two acid mixtures were compared on a set of matched paired samples of the lichen Pseudevernia furfuracea, a widely used biomonitor for which BEC values based on partial digestion were previously provided. The standard reference material BCR 482 (P. furfuracea) was used to validate analytical procedures consisting of either a HF total mineralization or an aqua regia partial one, both associated to ICP-MS multi-element analysis. In particular, the performance of the procedures was evaluated by comparing analytical results of field samples with the accuracy obtained on BCR aliquots (measured-to-expected percentage ratio). The total digestion showed a better performance for Al, As, Ba, Ca, Cd, Cu, Fe, Mn, Ni, Se, Sn, and Zn, whereas the opposite was found for Cr, Co, P, and S. Moreover, new BEC values were provided for P. furfuracea using a consolidated statistical approach, after a total sample digestion with hydrofluoric acid. The multivariate investigation of the background variability of 43 elements in 57 remote Italian sites led to the identification of geographically homogeneous areas for which BEC values are provided for use as reference in biomonitoring applications.

Nitrogen concentration in moss compared with N load in precipitation and with total N deposition in Switzerland.

Intensification of farming and an increase in motorised traffic have led to elevated nitrogen (N) emissions and thus to eutrophication of the environment, which threatens the nutrient balance in ecosystems. Earlier studies have demonstrated the suitability of mosses as biomonitors for measuring N deposition by comparing the N concentration in moss with that in precipitation. In our study however, we extended the comparison to the dry deposition of gases (nitrogen dioxide, nitric acid, ammonia) and aerosols (nitrate, ammonium), which, together with the N in precipitation, represent the main contributions to total N deposition. The aim of including several N compounds was to see whether the correlation with the N concentration in moss could be improved. We determined total N input from the atmosphere to the ecosystem at 24 sites in Switzerland and compared this value to the N concentration in two moss species collected <1000 m from these sites. Including the gases and aerosols improved the correlation between the N concentration in moss and N deposition. Ammonia was found to be the most important of the additionally included compounds at these sites. Especially at sites with a relatively high ammonia concentration in the air, the inclusion of ammonia improved the correlation of the comparison. We also demonstrate that the particular moss species tested had no influence on the correlation between N in moss and total N deposition. Our data supports the suitability of mosses as biomonitors for estimating N input into ecosystems.

Day-night variability of water-soluble ions in PM10 samples collected at a traffic site in southeastern Spain.

The present work reports diurnal and nocturnal concentrations of water-soluble ions associated to PM10 samples collected during the warm and cold seasons in the urban center of Elche (Southeastern Spain). Statistical differences between daytime and nighttime levels of PM10 were only observed during winter. The lower concentrations during the night were most likely the result of a reduction in traffic-induced road dust resuspension, since nocturnal concentrations of calcium also exhibited a significant decrease compared to daytime levels. During the warm season, nitrate was the only component that showed a statistically significant increase from day to night. The lower nocturnal temperatures that prevent the thermal decomposition of ammonium nitrate and the formation of nitric acid favored by the higher relative humidity at night are the most probable reasons for this variation. The close relationship between nitrate formation and relative humidity during nighttime was supported by the results of the correlation analysis. The reaction of sulfuric and nitric acids with CaCO3 occurred to a greater extent during daytime in summer.

Ground-level air pollution changes during a boreal wildland mega-fire.

The 2011 Richardson wildland mega-fire in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada had large effects on air quality. At a receptor site in the center of the AOSR ambient PM2.5, O3, NO, NO2, SO2, NH3, HONO, HNO3, NH4+ and NO3- were measured during the April-August 2011 period. Concentrations of NH3, HNO3, NO2, SO2 and O3 were also monitored across the AOSR with passive samplers, providing monthly summer and bi-monthly winter average values in 2010, 2011 and 2012. During the fire, hourly PM2.5 concentrations >450µgm-3 were measured at the AMS 1 receptor site. The 24-h National Ambient Air Quality Standard (NAAQS) of 35µgm-3 and the Canada Wide Standard (CWS) of 30µgm-3 were exceeded on 13days in May and 7days in June. During the fire emission periods, sharp increases in NH3, HONO, HNO3, NH4+, NO3- and total inorganic reactive N concentrations occurred, all closely correlated with the PM2.5 changes. There were large differences in the relative contribution of various N compounds to total inorganic N between the no-fire emission and fire emission periods. While in the absence of fires NO and NO2 dominated, their relative contribution during the fires was ~2 fold smaller, mainly due to increased NH3, NH4+ and NO3-. Concentrations of HONO and HNO3 also greatly increased during the fires, but their contribution to the total inorganic N pool was relatively small. Elevated NH3 and HNO3 concentrations affected large areas of northern Alberta during the Richardson Fire. While NH3 and HNO3 concentrations were not at levels considered toxic to plants, these gases contributed significantly to atmospheric N deposition. Generally, no significant changes in O3 and SO2 concentrations were detected and their ambient concentrations were below levels harmful to human health or sensitive vegetation.

Increasing importance of deposition of reduced nitrogen in the United States.

Rapid development of agriculture and fossil fuel combustion greatly increased US reactive nitrogen emissions to the atmosphere in the second half of the 20th century, resulting in excess nitrogen deposition to natural ecosystems. Recent efforts to lower nitrogen oxides emissions have substantially decreased nitrate wet deposition. Levels of wet ammonium deposition, by contrast, have increased in many regions. Together these changes have altered the balance between oxidized and reduced nitrogen deposition. Across most of the United States, wet deposition has transitioned from being nitrate-dominated in the 1980s to ammonium-dominated in recent years. Ammonia has historically not been routinely measured because there are no specific regulatory requirements for its measurement. Recent expansion in ammonia observations, however, along with ongoing measurements of nitric acid and fine particle ammonium and nitrate, permit new insight into the balance of oxidized and reduced nitrogen in the total (wet + dry) US nitrogen deposition budget. Observations from 37 sites reveal that reduced nitrogen contributes, on average, ∼65% of the total inorganic nitrogen deposition budget. Dry deposition of ammonia plays an especially key role in nitrogen deposition, contributing from 19% to 65% in different regions. Future progress toward reducing US nitrogen deposition will be increasingly difficult without a reduction in ammonia emissions.

Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase.

Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O3) and in liquid phase using nitric acid (HNO3). The activated carbon samples were characterized using N2 adsorption-desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m(2)/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich-Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO3), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.

Atmospheric pollutants in peri-urban forests of Quercus ilex: evidence of pollution abatement and threats for vegetation.

Peri-urban vegetation is generally accepted as a significant remover of atmospheric pollutants, but it could also be threatened by these compounds, with origin in both urban and non-urban areas. To characterize the seasonal and geographical variation of pollutant concentrations and to improve the empirical understanding of the influence of Mediterranean broadleaf evergreen forests on air quality, four forests of Quercus ilex (three peri-urban and one remote) were monitored in different areas in Spain. Concentrations of nitrogen dioxide (NO2), ammonia (NH3), nitric acid (HNO3) and ozone (O3) were measured during 2 years in open areas and inside the forests and aerosols (PM10) were monitored in open areas during 1 year. Ozone was the only air pollutant expected to have direct phytotoxic effects on vegetation according to current thresholds for the protection of vegetation. The concentrations of N compounds were not high enough to directly affect vegetation but could be contributing through atmospheric N deposition to the eutrophization of these ecosystems. Peri-urban forests of Q. ilex showed a significant below-canopy reduction of gaseous concentrations (particularly NH3, with a mean reduction of 29-38%), which indicated the feasibility of these forests to provide an ecosystem service of air quality improvement. Well-designed monitoring programs are needed to further investigate air quality improvement by peri-urban ecosystems while assessing the threat that air pollution can pose to vegetation.

Oxygen and nitrogen isotopic composition of nitrate in commercial fertilizers, nitric acid, and reagent salts.

Nitrate is a key component of synthetic fertilizers that can be beneficial to crop production in agro-ecosystems, but can also cause damage to natural ecosystems if it is exported in large amounts. Stable isotopes, both oxygen and nitrogen, have been used to trace the sources and fate of nitrate in various ecosystems. However, the oxygen isotope composition of synthetic and organic nitrates is poorly constrained. Here, we present a study on the N and O isotope composition of nitrate-based fertilizers. The δ(15)N values of synthetic and natural nitrates were 0 ± 2 ‰ similar to the air N2 from which they are derived. The δ(18)O values of synthetic nitrates were 23 ± 3 ‰, similar to air O2, and natural nitrate fertilizer δ(18)O values (55 ± 5 ‰) were similar to those observed in atmospheric nitrate. The Δ(17)O values of synthetic fertilizer nitrate were approximately zero following a mass-dependent isotope relationship, while natural nitrate fertilizers had Δ(17)O values of 18 ± 2 ‰ similar to nitrate produced photochemically in the atmosphere. These narrow ranges of values can be used to assess the amount of nitrate arising from fertilizers in mixed systems where more than one nitrate source exists (soil, rivers, and lakes) using simple isotope mixing models.

Total iodine quantification in fluids and tissues from iodine- or iodide-supplemented rats by ion chromatography following microwave-assisted digestion.

BACKGROUND: Iodine is a crucial component of thyroid hormones, and several reports have shown that iodine per se is implicated in the physiopathology of other organs. METHODS: Innovative ion chromatography detection following a four-step temperature ramp microwave digestion in 25-50 mM nitric acid was developed to measure total iodine in biological fluids and tissue samples from female Sprague-Dawley rats supplemented with 0.05% molecular iodine (I2) or 0.05% potassium iodide (I(-)) in drinking water. RESULTS: The reported method allows the measurement of total iodine with a limit of quantification of 13.7 µg L(-1), recoveries of 96.3-100.3%, and intra- and inter-assay variations, of 3.5% and 7.4% respectively. Analysis of biological fluids showed that after 48 hours, iodine-supplemented animals exhibited significantly higher levels of total iodine in both serum and urine compared with those supplemented with iodide. The half-life of iodine in serum and urine measured over the first 48 h showed similar patterns for both the I2 (7.89 and 7.76 hours) and I(-) (8.27 and 8.90 hours) supplements. Differential uptake patterns were observed in tissues after 6 days of supplements, with I(-) preferentially retained by thyroid, lactating mammary gland, and milk, and a slightly but significantly higher capture of I2 in pituitary, ovary, and virgin mammary gland. CONCLUSIONS: We developed a rapid, selective, and accurate digestion method to process fluid and tissue samples that permits reproducible measurements of total iodine by ion chromatography; iodine or iodide supplement show a similar serum and urine half-life, but organ-specific uptake depends on the chemical form of the iodine supplement.

Sensitivity analyses of factors influencing CMAQ performance for fine particulate nitrate.

UNLABELLED: Improvement of air quality models is required so that they can be utilized to design effective control strategies for fine particulate matter (PM2.5). The Community Multiscale Air Quality modeling system was applied to the Greater Tokyo Area of Japan in winter 2010 and summer 2011. The model results were compared with observed concentrations of PM2.5 sulfate (SO4(2-)), nitrate (NO3(-)) and ammonium, and gaseous nitric acid (HNO3) and ammonia (NH3). The model approximately reproduced PM2.5 SO4(2-) concentration, but clearly overestimated PM2.5 NO3(-) concentration, which was attributed to overestimation of production of ammonium nitrate (NH4NO3). This study conducted sensitivity analyses of factors associated with the model performance for PM2.5 NO3(-) concentration, including temperature and relative humidity, emission of nitrogen oxides, seasonal variation of NH3 emission, HNO3 and NH3 dry deposition velocities, and heterogeneous reaction probability of dinitrogen pentoxide. Change in NH3 emission directly affected NH3 concentration, and substantially affected NH4NO3 concentration. Higher dry deposition velocities of HNO3 and NH3 led to substantial reductions of concentrations of the gaseous species and NH4NO3. Because uncertainties in NH3 emission and dry deposition processes are probably large, these processes may be key factors for improvement of the model performance for PM2.5 NO3(-). IMPLICATIONS: The Community Multiscale Air Quality modeling system clearly overestimated the concentration of fine particulate nitrate in the Greater Tokyo Area of Japan, which was attributed to overestimation of production of ammonium nitrate. Sensitivity analyses were conducted for factors associated with the model performance for nitrate. Ammonia emission and dry deposition of nitric acid and ammonia may be key factors for improvement of the model performance.

Nitric acid recycling and copper nitrate recovery from effluent.

The recycling of nitric acid and copper nitrate contained in an industrial effluent was studied. The experiments conducted on such a medium showed that the presence of copper nitrate significantly improves nitric acid-water separation during distillation in an azeotropic medium. At the temperature of the azeotrope, however, this metal salt starts to precipitate, making the medium pasty, thus inhibiting the nitric acid extraction process. The optimisation of parameters such as column efficiency and adding water to the boiler at the azeotrope temperature are recommended in this protocol in order to collect the various components while avoiding the formation of by-products: NOx compounds. Thus, the absence of column, along with the addition of a small volume of water at a temperature of 118 °C, significantly increases the yield, allowing 94 % nitric acid to be recovered at the end of the process, along with the residual copper nitrate. The resulting distillate, however, is sufficiently dilute to not be used as is. Rectification is required to obtain concentrated nitric acid at 15 mol·l(-1), along with a weakly acidic distillate from the distillation front. This latter is quenched using potassium hydroxide and is used as a fertiliser solution for horticulture or sheltered market gardening. This process thus allows complete recycling of all the medium's components, including that of the distillate resulting from the nitric acid rectification operation.

An online monitoring system for atmospheric nitrous acid (HONO) based on stripping coil and ion chromatography.

A new instrument for measuring atmospheric nitrous acid (HONO) was developed, consisting of a double-wall glass stripping coil sampler coupled with ion chromatography (SC-IC). SC-IC is featured by small size (50 x 35 x 25 cm) and modular construction, including three independent parts: the sampling unit, the transfer and supporting unit, and the detection unit. High collection efficiency (> 99%) was achieved with 25 micromol/L Na2CO3 as absorption solution even in the presence of highly acidic compounds. This instrument has a detection limit of 8 pptv at 15 min time resolution, with a measurement uncertainty of 7%. Potential interferences from NO(x), NO2+SO2, NO2+VOCs, HONO+O3, HNO3, peroxyacetyl nitrite (PAN) and particle nitrite were quantified in laboratory studies and were found to be insignificant under typical atmospheric conditions. Within the framework of the 3C-STAR project, inter-comparison between the SC-IC and LOPAP (long path liquid absorption photometer) was conducted at a rural site in the Pearl River Delta. Good agreement was achieved between the two instruments over three weeks. Both instruments determined a clear diurnal profile of ambient HONO concentrations from 0.1 to 2.5 ppbv. However, deviations were found for low ambient HONO concentrations (i.e. < 0.3 ppbv), which cannot be explained by previous investigated interference species. To accurately determine the HONO budget under illuminated conditions, more intercomparison of HONO measurement techniques is still needed in future studies, especially at low HONO concentrations.