Total SO2 Concentrations Research Articles

Comprehensive Classification and Regression Modeling of Wine Samples Using 1H NMR Spectra.

Recently, 1H NMR (nuclear magnetic resonance) spectroscopy was presented as a viable option for the quality assurance of foods and beverages, such as wine products. Here, a complex chemometric analysis of red and white wine samples was carried out based on their 1H NMR spectra. Extreme gradient boosting (XGBoost) machine learning algorithm was applied for the wine variety classification with an iterative double cross-validation loop, developed during the present work. In the case of red wines, Cabernet Franc, Merlot and Blue Frankish samples were successfully classified. Three very common white wine varieties were selected and classified: Chardonnay, Sauvignon Blanc and Riesling. The models were robust and were validated against overfitting with iterative randomization tests. Moreover, four novel partial least-squares (PLS) regression models were constructed to predict the major quantitative parameters of the wines: density, total alcohol, total sugar and total SO2 concentrations. All the models performed successfully, with R2 values above 0.80 in almost every case, providing additional information about the wine samples for the quality control of the products. 1H NMR spectra combined with chemometric modeling can be a good and reliable candidate for the replacement of the time-consuming traditional standards, not just in wine analysis, but also in other aspects of food science.

Effect of Different Reducing Agents on Aromatic Compounds, Antioxidant and Chromatic Properties of Sauvignon Blanc Wine.

Sulfur dioxide (SO2) is widely the most used enological additive with reductive, antiseptic and dissolving properties. According to increasing health concerns and the gradual decrease in total SO2 concentrations allowed in wine, alternative and supplementary agents for preservation are being investigated. For this reason, the current study was focused on the impact of different commercial reductive agents on white wine antioxidant activity and chemical composition. The effect of additives that combine sulfites, ascorbic acid and enological tannins were compared against standard 5% sulfurous acid (H2SO3) during the pre-fermentative treatments of Sauvignon Blanc must (Vitis vinifera L.). The basic parameters of quality, free amino-nitrogen and total polyphenoliccompounds in must were analyzed. Gas chromatography and spectrophotometric methods were used to investigate the overall volatile composition, antioxidant and chromatic parameters in wines. The obtained results undoubtedly pointed out the positive effect of sulfuric acid on the fermentation dynamics. Furthermore, application of combined reducing additives with potassium metabisulfite, L-ascorbic acid, gallotannins and ellagitannins, resulted in a higher antioxidant capacity and increased concentration of aromatic compounds and their odor activity values in Sauvignon Blanc wine.

Acetaldehyde kinetics of enological yeast during alcoholic fermentation in grape must.

Acetaldehyde strongly binds to the wine preservative SO2 and, on average, causes 50-70mgl-1 of bound SO2 in red and white wines, respectively. Therefore, a reduction of bound and total SO2 concentrations necessitates knowledge of the factors that affect final acetaldehyde concentrations in wines. This study provides a comprehensive analysis of the acetaldehyde production and degradation kinetics of 26 yeast strains of oenological relevance during alcoholic fermentation in must under controlled anaerobic conditions. Saccharomyces cerevisiae and non-Saccharomyces strains displayed similar metabolic kinetics where acetaldehyde reached an initial peak value at the beginning of fermentations followed by partial reutilization. Quantitatively, the range of values obtained for non-Saccharomyces strains greatly exceeded the variability among the S.cerevisiae strains tested. Non-Saccharomyces strains of the species C. vini, H. anomala, H. uvarum, and M. pulcherrima led to low acetaldehyde residues (<10mgl-1), while C.stellata, Z. bailii, and, especially, a S. pombe strain led to large residues (24-48mgl-1). Acetaldehyde residues in S.cerevisiae cultures were intermediate and less dispersed (14-34mgl-1). Addition of SO2 to Chardonnay must triggered significant increases in acetaldehyde formation and residual acetaldehyde. On average, 0.33mg of residual acetaldehyde remained per mg of SO2 added to must, corresponding to an increase of 0.47mg of bound SO2 per mg of SO2 added. This research demonstrates that certain non-Saccharomyces strains display acetaldehyde kinetics that would be suitable to reduce residual acetaldehyde, and hence, bound-SO2 levels in grape wines. The acetaldehyde formation potential may be included as strain selection argument in view of reducing preservative SO2 concentrations.

Temporal distribution, influencing factors and pollution sources of urban ambient air quality in Nanchong, China

The PM10, SO₂ and NO₂ mass concentrations were obtained over five years from monitoring stations across Nanchong, a southwest city in China. Changes in urban air quality over time, as well as the factors influencing that change, were evaluated based on air pollutant concentrations, the Air Pollution Index (API), and the Comprehensive Pollution Index (P). The results showed that the total annual mean PM10, SO₂ and NO₂ concentrations over the five years studied were 61.1±1.1, 45.0±3.9 and 34.9±4.9 μg·m-3, respectively. The annual mean concentrations displayed a generally decreasing trend; lower than the annual mean second-level air quality limit. Meanwhile, the annual mean API values were in a small range of 52-53, the air quality levels were gradeⅡ, and P values were 1.06-1.21 less than the slight level (P ≤ 1.31). Total monthly mean PM10, SO₂, NO₂ concentrations, and API and P values were consistently higher in winter and spring than during autumn and summer. The results of a correlation analysis showed that temperature and pressure were the major meteorological factors influencing pollution levels. Pollution sources included industrial coal and straw burning, automobiles exhaust and road dust, fireworks, and dust storms.

Effect of headspace volume, ascorbic acid and sulphur dioxide on oxidative status and sensory profile of Riesling wine

White wine spoilage due to oxidation is a major concern during post-fermentation treatments and bottling. In this study, we explored the effects of different oxygen and free SO2 levels and ascorbic acid addition on the development of white wine. Riesling wine was bottled in 500-mL bottles under screw caps with four different headspace volumes (0, 10, 20 and 30 mL), two levels of free SO2 (45 and 70 mg/L) and with and without ascorbic acid (250 mg/L) addition giving 16 wines for analysis. Cold stored (at 5 °C) control was used as reference for data analysis and sensory evaluation. Dissolved oxygen and the oxygen in headspace were measured in the resulting 17 wines. Free and total SO2 concentrations, ascorbic acid concentration, colour, redox potential and antioxidative capacity were measured regularly in wine samples. After 6 months of storage, the wines were evaluated using descriptive sensory analysis. Both sensory and analytical results showed significant differences among the wines. Intensive wine exposure to oxygen (headspace volume) affected colour, free and total SO2 rate, and the overall sensory quality of wine. Ascorbic acid addition had positive effect on the sensory evaluation of wines and on SO2 levels, whereas combined with large headspace volumes, provoked intensive browning in wine samples.

Ozone Monitoring Instrument Observations of Interannual Increases in SO2 Emissions from Indian Coal-Fired Power Plants during 2005–2012

Due to the rapid growth of electricity demand and the absence of regulations, sulfur dioxide (SO2) emissions from coal-fired power plants in India have increased notably in the past decade. In this study, we present the first interannual comparison of SO2 emissions and the satellite SO2 observations from the Ozone Monitoring Instrument (OMI) for Indian coal-fired power plants during the OMI era of 2005-2012. A detailed unit-based inventory is developed for the Indian coal-fired power sector, and results show that its SO2 emissions increased dramatically by 71% during 2005-2012. Using the oversampling technique, yearly high-resolution OMI maps for the whole domain of India are created, and they reveal a continuous increase in SO2 columns over India. Power plant regions with annual SO2 emissions greater than 50 Gg year(-1) produce statistically significant OMI signals, and a high correlation (R = 0.93) is found between SO2 emissions and OMI-observed SO2 burdens. Contrary to the decreasing trend of national mean SO2 concentrations reported by the Indian Government, both the total OMI-observed SO2 and annual average SO2 concentrations in coal-fired power plant regions increased by >60% during 2005-2012, implying the air quality monitoring network needs to be optimized to reflect the true SO2 situation in India.

Spatial-temporal variations in regional ambient sulfur dioxide concentration and source-contribution analysis: A dispersion modeling approach

Abstract An understanding of the complexity of spatial-temporal variations in regional air quality and its respective source contributors is one of the priority research areas due to the adverse effects of air pollution on human health and the environment. In this paper, we integrate air dispersion modeling and Geographic Information System (GIS) based spatial analysis methods to characterize regional ambient air quality at a relatively fine geographical scale (1 km × 1 km) while ascertaining source contributors. The temporal variation analysis shows that sulfur dioxide (SO2) pollution in Dallas County, Texas did not consistently increase or decrease from 1996 to 2002. The lowest and highest mean levels of annual SO2 concentrations at all the receptors (n = 2000) were 0.39 μg m−3 and 2.32 μg m−3 in 2001 and 2002, respectively. Meanwhile, analysis results suggest that the annual SO2 concentrations in a small part of Dallas County slightly declined with the highest value of −1.00 μg m−3 over the 1996–2002 period, while most of the county experienced increased SO2 concentration levels from 0.00 to 0.25 μg m−3. In addition, the source apportionment analysis demonstrated that the variations in total annual SO2 concentrations in Dallas County from 1996 to 2002 were significantly different from those by source classification. That is, compared to industrial emission sources, on-road vehicle emission sources caused variations in annual SO2 concentrations with relatively larger extents (power of determinant = 0.42). However, extreme variations in concentrations were due to industrial emission sources (3.45% vs. 0.00%). Based on these observations, it can be concluded that the combination of air dispersion modeling and GIS-based spatial analysis shows promise to overcome the drawbacks of sparse intraurban air quality monitoring in characterizing the spatial-temporal micro-variations in regional ambient air quality and ascertaining roles of source contributors over long-term periods.

Meteorological and Chemical Behavior of Gaseous Sulfur Compounds in and around an Urban Valley

The effects of photochemical oxidation of reduced sulfur compounds (RSCs: H2S, CH3SH, DMS, and DMDS) on SO2 production were evaluated at high (HV) and low ventilation (LV) conditions, based on a CALPUFF dispersion model coupled with photo-chemical oxidation mechanisms for four RSCs. The RSC emission concentrations used in the modeling were measured in and around an urban valley during a field campaign held in October 2008. SO2 production with LV (up to 156 ppb at 0900 LST) was found to be significantly higher than that with HV (up to 30 ppb). SO2 produced by photochemical oxidation of RSCs with LV (78% of total SO2 concentrations) was much higher than that with HV (27%), while the predominant RSC species were similar: DMDS (≥ 60% of the total contributions) with HV and LV when compared to three other RSCs (＜ 20%). The difference in SO2 concentration between HV and LV might be caused by the combined effects of photochemical oxidation of RSCs and ventilation condition.

Dispersion and photochemical oxidation of reduced sulfur compounds in and around a large industrial complex in Korea

In this study, the environmental behavior of reduced sulfur compounds (RSCs: H2S, DMS, CS2, DMDS, and CH3SH) was investigated in an area influenced by strong anthropogenic processes based on a numerical modeling approach. The RSC emission concentrations were measured from multiple locations around the Ban-Wall industrial complex (BWIC) in the city of An San (AS), Korea, during a series of field campaigns held between August 2004 and September 2005. These emissions were then used as input for a CALPUFF dispersion model with the 34 dominant chemical reactions for RSCs. The impact of RSC emission on SO2 concentrations was assessed further in the study areas. The model study indicated the possibility that RSCs emitted in and around the BWIC can exert a direct impact on the ambient SO2 concentration levels in its surrounding areas with the most prominent effect observed during summer. Our prediction indicated that a significant fraction of SO2 was produced photochemically in and around the BWIC during the summer (about 30% of total SO2 concentrations) and fall events (∼20%). These photochemical productions of SO2 were mainly ascribable to H2S (∼60% of total contributions) and DMDS (∼25%) out of all five target RSCs. Meteorological contribution (dispersion) to SO2 concentration level was also highest during summer.

Free Sulfur Dioxide in Beer as the Difference between Total Sulfur Dioxide and Acetaldehyde: A Voltammetric Approach

A method that involved voltammetric determination of the levels of total sulfur dioxide (SO2) and acetaldehyde was developed for the determination of the level of free SO2 in beer. Free SO2 concentration is calculated by the difference between the concentrations of SO2 (total) and acetaldehyde. In fact, it is shown that SO2 reacts almost completely with acetaldehyde, which represents more than 95% of all aldehydes present in beer. In a first step, aldehydes are removed from an alkalinized sample of beer with a stream of nitrogen gas, collected in an appropriate electrolyte trapping solution, derivatized with hydrazine, and determined by voltammetry at a hanging mercury drop electrode. The remaining beer solution is strongly acidified and purged with nitrogen. Total SO2 is collected in an appropriate electrolyte trapping solution and determined by voltammetry. The proposed method has a relative standard deviation of approximately 2.1 and 4.4% for total SO2 and free SO2 concentrations, respectively, normally found in beer. Results are in agreement with those obtained by the para-rosaniline reference method.

A longitudinal study of ambient air pollutants and the lung peak expiratory flow rates among asthmatic children in Hungary.

We conducted this study in Budapest, Hungary, to better characterize the effects of exposure to ambient air pollutants on the lung function of asthmatic children. The 60 study participants were 9-14 years old, had physician-diagnosed asthma, and were symptomatic during the previous year. Their ambient air pollutant exposures to total suspended particulates (TSP) and sulphur dioxide (SO2) were estimated from measurements made at the air monitor nearest their residence. We used analysis of variance and a fixed-effects model to assess the impact of the pollutants upon their morning and evening peak expiratory flow rates (PEFR) from 13 September to 5 December 1993. Total suspended particulates and SO2 concentrations exceeded World Health Organization guideline limits on several days. Pollutant concentrations and PEFR increased during the study period. After adjusting for temperature, humidity, weekend/weekday, and the time trend, we found no consistent association between air pollutant concentrations and PEFR. Fall to winter seasonal changes had a large influence on PEFR and may have overshadowed the effects of the air pollutants during the study period. Seasonal influences should be carefully considered when planning future studies.

Biogenic sulfur emissions and aerosols over the tropical South Atlantic: 2. One‐dimensional simulation of sulfur chemistry in the marine boundary layer

Based on experimental data collected during cruise 15/3 of R/V Meteor in the tropical South Atlantic (19°S), the marine sulfur cycle has been simulated with a one‐dimensional coupled meteorological‐chemical model. The potential of sea‐spray aerosols to act as a sink for SO2 produced from dimethylsulfide (DMS) oxidation has been examined by using a simple humidity and height dependent parameterization for sea salt aerosol distribution. Simulations show significant reduction of total SO2 concentrations to 27–82% of the values found in the absence of this heterogenous process. The sulfur species concentrations calculated using a zero‐dimensional box model agree with excess sulfate measurements in aerosol samples. The DMS, SO2, H2SO4 (sulfates formed by SO2 oxidation in the gas phase), and XSO4 (sulfates formed by SO2 oxidation in sea‐spray aerosols) vertical profiles, their diurnal cycles, and turbulent fluxes have been calculated with a one‐dimensional model, based solely on shipboard chemical measurements and meteorological radiosonde soundings. Sensitivity analysis of the sea salt aerosol parameterization shows strong dependence on the assumed aerosol distribution, thus calling for a more comprehensive approach using a coupled aerosol‐meteorological model.

Sulphonation of Eastern Black Spruce Chips, Part II

Abstract Eastern black spruce, Picea mariana, chips have been treated to high yields, at temperatures from 120° to 150°C, with sodium bisulphite solutions of pH 4 and total SO2 concentrations from 0.23 to 1.92 mol L−1. The rate of sulphonation depends on the concentration of sites available for sulphonation and total SO2 concentration to the power of 0.4; it increases by approximately 70 percent for each 10°C temperature rise. It is postulated that sulphonation at pH 4 occurs by two mechanisms, one which is dependent on total SO2 concentration and involves a quinonemethide intermediate and one which is independent of total SO2 concentration and involves a carbonium ion intermediate. The rates of yield loss and lignin loss are dependent only on temperature and approximately double for each 10°C temperature increase. High total SO2 concentrations are necessary for efficient production of high strength ultra-high yield pulps from black spruce chips when treated with sodium bisulphite solutions.

Factors Affecting Sulphonation of Eastern Black Spruce Wood Chips

Abstract Eastern black spruce, Picea mariana, chips have been treated to high yields, at temperatures from 72° to 150°C with sulphite solutions of pH 7 and total SO2 concentrations from 0.1 to 1.0 mol L-1. The rate of sulphonation of black spruce chips is directly proportional to the product of concentration of sites available for sulphonation and the total SO2 concentration. The energy of activation for sulphonation is 62.6 ± 2.3 kJ mol-1. The rate of lignin dissolution at pH 7 is dependent only upon the temperature. High total SO2 concentrations are necessary for the efficient production of high strength ultra-high yields pulps. It is postulated that sulphonation at pH 7 is governed by a rate limited addition of bisulphite to quinone methide intermediates formed from phenolic lignin units.

Factors Affecting Death of Yeast by Sulfur Dioxide

The interrelated factors that influence the effectiveness of SO2 as a preservative against yeast were studied and the correct quantitative relationships of SO2 molecular species determined. Widely differing pK values for SO2 were found in the literature, compared with experimental data, and one set of values was selected. Undissociated H2SO3 is the only effective form of SO2 against yeast and can be calculated from measurement of free SO2 and pH, and the correct dissociation constants. Duration of contact, pH, concentration of SO2 and yeast, and binding of SO2 all influence the preservative action of SO2. Lower total SO2 concentrations can be used for food preservation by optimum control of these factors.