Water-soluble Organic Matter Research Articles

Geogenic CO2 affects stabilization of soil organic matter

SummaryThe soil on mofette sites is affected by ascending geogenic carbon dioxide (CO2), which partially fills the soil atmosphere. We hypothesized that geogenic CO2 affects the stabilization of soil organic matter (SOM) at lower partial pressures than had been discussed previously for mofette sites. We studied loamy Ah horizons (n = 22; pH 3.4–4) of the soil along a transect on a grassland mofette site in the northwest Czech Republic with CO2 partial pressures (p(CO2)) of up to 0.52. The samples were fractionated by particle size, density and solubility (water‐soluble organic matter (WSOM)), and analysed quantitatively for organic carbon (C) and total nitrogen (N) and qualitatively (13C‐NMR spectroscopy). Soil OM with a narrower C:N ratio accumulated in the clay fraction, but at p(CO2) less than approximately 0.1 the proportion of SOM in the clay fraction relative to total SOM tended to decrease with increasing p(CO2), whereas that of particulate organic matter (POM) fractions increased with increasing p(CO2). We attribute the distribution of SOM among the mineral soil and POM to decreased interactions with minerals of the clay fraction. The formation of iron (Fe) hydroxides, which potentially sorb SOM, was not affected negatively by CO2. The potential reactivity of Fe hydroxides was even positively affected by increased p(CO2). Export of dissolved SOM into the subsoil might increase at mofette sites because of the large amounts of WSOM and decreasing interactions with minerals of the clay fraction. Therefore, our results show negative effects of CO2 on SOM stabilization even at moderate p(CO2).

Tuning Biochar Properties via Partial Gasification: Facilitating Inorganic Nutrients Recycling and Altering Organic Matter Leaching

This study reports a systematic study on the potential of employing partial gasification at low conversions for tuning biochar for better properties and facilitating the recycling of inorganic nutrient species. The raw biochars were prepared from mallee wood and leaf at fast pyrolysis at 500 °C (a temperature pertinent to bio-oil production) and subsequent tuning via partial steam gasification at 725 °C and low conversions (5 and 10% on a carbon basis). The favorable structure tuning is achieved at the expense of 8–23% carbon, which would otherwise be available for sequestration during biochar application in soil. The development of the pore structure and transformation of the chemical forms of inorganic nutrient species as a result of partial gasification increase the leachability of the inorganic nutrient species in biochars via both water and Mehlich I solution. In addition, <1.5% of the organic matter in raw and tuned biochar is water-soluble. The leaching of water-soluble organic matter from the tune...

Investigating the water-soluble organic functionality of urban aerosols using two-dimensional correlation of solid-state 13C NMR and FTIR spectral data

Two-dimensional (2D) correlation spectroscopy, applied to one-dimensional solid-state cross polarization magic angle spinning (CP-MAS) 13C nuclear magnetic resonance (NMR), Fourier transform infrared coupled to attenuated total reflectance (FTIR-ATR), and the combination of CP-MAS 13C NMR and FTIR-ATR data, has been used to glean new structural information on the most hydrophobic water-soluble organic matter (WSOM) from fine urban air particles collected during different seasons. CP-MAS 13C NMR analysis confirmed that unsubstituted saturated aliphatics, aromatics, oxygenated aliphatics, and carboxylic acids accounted for most (84–92%) of the characterized carbon functional groups. Applying 2D correlation spectroscopy to CP-MAS 13C NMR and FTIR-ATR spectra indicates an increase in the contribution of hydroxyl and carboxylic groups to the aliphatic component with increasing air temperature, suggesting the photo-chemical origin of these WSOM structures. Urban samples from colder periods are clearly impacted by biomass combustion sources, although the presence of aged and processed organic aerosols cannot be ruled out. Using 2D FTIR-13C NMR hetero-spectral correlation spectroscopy, it has been demonstrated that the studied WSOM samples consists of at least two different classes of compounds: (i) an aliphatic component rich in both carboxylic and hydroxyl functional groups, and (ii) lignin-derived structures.

Chemical composition and size distribution of summertime PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; at a high altitude remote location in the northeast of the Qinghai–Xizang (Tibet) Plateau: insights into aerosol sources and processing in free troposphere

Abstract. Aerosol filter samples were collected at a high-elevation mountain observatory (4180 m a.s.l.) in the northeastern part of the Qinghai–Xizang (Tibet) Plateau (QXP) during summer 2012 using a low-volume sampler and a micro-orifice uniform deposit impactor (MOUDI). These samples were analyzed for water-soluble inorganic ions (WSIs), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and total organic nitrogen (TON) to elucidate the size-resolved chemical composition of free tropospheric aerosols in the QXP region. The average mass concentration of the sum of the analyzed species in PM2.5 (particle matter) (WSIs + OC + EC + TON) was 3.74 μg sm−3, 36% of which was sulfate, 18% OC, 17 % nitrate, 10% ammonium, 6.6% calcium, 6.4% TON, 2.6% EC, 1.5 % sodium, 0.9% chloride, 0.5% magnesium, and 0.3% potassium. The size distributions of sulfate and ammonium peaked in the accumulation mode (0.32–0.56 μm), whereas the size distributions of both nitrate and calcium peaked in the range of 1.8–3.2 μm, suggesting the formation of nitrate on mineral dust. OC, EC and TON were also predominantly found in the accumulation mode. The bulk chemical composition and the average oxidation degree of water-soluble organic matter (WSOM) were assessed using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). WSOM was found to be highly oxidized in all PM2.5 samples with an average oxygen-to-carbon atomic ratio (O / C) of 1.16 and an organic mass-to-organic carbon ratio (OM / OC) of 2.75. The highly oxidized WSOM was likely related to active cloud processing during upslope air mass transport coupled with strongly oxidizing environments caused by snow/ice photochemistry. High average ratios of OC / EC (7.6) and WSOC / OC (0.79) suggested that organic aerosols were primarily made of secondary species. Secondary organic aerosol (SOA) was estimated on average accounting for 80% (62–96%) of the PM2.5, indicating that SOA is an important component of free tropospheric aerosols over the northern QXP.

Molecular characterization of free tropospheric aerosol collected at the Pico Mountain Observatory: a case study with a long-range transported biomass burning plume

Abstract. Free tropospheric aerosol was sampled at the Pico Mountain Observatory located at 2225 m above mean sea level on Pico Island of the Azores archipelago in the North Atlantic. The observatory is located ~ 3900 km east and downwind of North America, which enables studies of free tropospheric air transported over long distances. Aerosol samples collected on filters from June to October 2012 were analyzed to characterize organic carbon, elemental carbon, and inorganic ions. The average ambient concentration of aerosol was 0.9 ± 0.7 μg m−3. On average, organic aerosol components represent the largest mass fraction of the total measured aerosol (60 ± 51%), followed by sulfate (23 ± 28%), nitrate (13 ± 10%), chloride (2 ± 3%), and elemental carbon (2 ± 2%). Water-soluble organic matter (WSOM) extracted from two aerosol samples (9/24 and 9/25) collected consecutively during a pollution event were analyzed using ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Approximately 4000 molecular formulas were assigned to each of the mass spectra in the range of m/z 100–1000. The majority of the assigned molecular formulas had unsaturated structures with CHO and CHNO elemental compositions. FLEXPART retroplume analyses showed the sampled air masses were very aged (average plume age &gt; 12 days). These aged aerosol WSOM compounds had an average O/C ratio of ~ 0.45, which is relatively low compared to O/C ratios of other aged aerosol. The increase in aerosol loading during the measurement period of 9/24 was linked to biomass burning emissions from North America by FLEXPART retroplume analysis and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts. This was confirmed with biomass burning markers detected in the WSOM and with the morphology and mixing state of particles as determined by scanning electron microscopy. The presence of markers characteristic of aqueous-phase reactions of phenolic species suggests that the aerosol collected at the Pico Mountain Observatory had undergone cloud processing before reaching the site. Finally, the air masses of 9/25 were more aged and influenced by marine emissions, as indicated by the presence of organosulfates and other species characteristic of marine aerosol. The change in the air masses for the two samples was corroborated by the changes in ethane, propane, and ozone, morphology of particles, as well as by the FLEXPART retroplume simulations. This paper presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at a lower free troposphere remote location and provides evidence of low oxygenation after long-range transport. We hypothesize this is a result of the selective removal of highly aged and polar species during long-range transport, because the aerosol underwent a combination of atmospheric processes during transport facilitating aqueous-phase removal (e.g., clouds processing) and fragmentation (e.g., photolysis) of components.

Targeted high-resolution ion mobility separation coupled to ultrahigh-resolution mass spectrometry of endocrine disruptors in complex mixtures.

Traditional separation and detection of targeted compounds from complex mixtures from environmental matrices requires the use of lengthy prefractionation steps and high-resolution mass analyzers due to the large number of chemical components and their large structural diversity (highly isomeric). In the present work, selected accumulation trapped ion mobility spectrometry (SA-TIMS) is coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for direct separation and characterization of targeted endocrine-disrupting compounds (EDC) from a complex environmental matrix in a single analysis. In particular, targeted identification based on high-resolution mobility (R ∼ 70-120) and ultrahigh-resolution mass measurements (R > 400 000) of seven commonly targeted EDC and their isobars (e.g., bisphenol A, (Z)- and (E)-diethylstilbestrol, hexestrol, estrone, α-estradiol, and 17-ethynylestradiol) is shown from a complex mixture of water-soluble organic matter (e.g., Suwannee River Fulvic Acid Standard II) complemented with reference standard measurements and theoretical calculations (<3% error).

Profiling Water-Soluble Organic Matter from Urban Aerosols Using Comprehensive Two-Dimensional Liquid Chromatography

Comprehensive two-dimensional liquid chromatography (LC×LC) coupled with a diode array detector (DAD) has been used for the first time to investigate chemical heterogeneity and map the hydrophobicity versus molecular weight distribution of the most hydrophobic acid fractions in water-soluble organic matter (WSOM) from fine atmospheric aerosols collected over different seasons at a urban location. The use of LC×LC–DAD, combining the use of two independent separation mechanisms (per aqueous liquid chromatography [PALC] versus size-exclusion chromatography [SEC]), has shown a great potential for unraveling and resolving the heterogeneity of WSOM, further providing a deeper insight into how size-distinguished aerosol WSOM fractions differ in hydrophobicity during different seasonal events. The combination of PALC×SEC–DAD data with an already proposed data treatment procedure revealed that the WSOM samples collected during warm seasons are enriched in aliphatic structures, while those collected during colder s...

Influence of Leaching Solution and Catchment Location on the Fluorescence of Water-Soluble Organic Matter

Organic matter (OM) plays a significant role in biogeochemical processes in soil and water systems. Water-soluble organic matter (WSOM) leached from soil samples is often analyzed as representative of potentially mobile OM. However, there are many WSOM extraction methods in the literature with no clear guidelines for method selection. In this study, four common leaching solutions (0.5 M K2SO4, 0.01 M CaCl2, 2 M KCl, and H2O) were used to extract WSOM from various locations within a forested catchment. Fluorescence spectroscopy was used to analyze the impact of extraction method on WSOM chemistry. While all four methods consistently identified chemical differences between WSOM from a north-facing slope, south-facing slope, and riparian zone, there were clear differences in fluorescence signals between the leaching methods. All three salt solutions contained WSOM with a higher fluorescence index and humification index than WSOM leached with H2O, suggesting the presence of salts releases different fractions of the soil organic matter. A parallel factor analysis (PARAFAC) model developed from the leachates identified a distinctive soil humic fluorophore observed in all samples and fluorescent artifacts present in H2O-leached samples.

Characterization of Dissolved Organic Matter from Sewage Sludge using 3D-Fluorescence Spectroscopy and Chemometric Tools

The aim of the present article is to show the possibilities of chemometric tools and the parallel factor analysis (PARAFAC) model, as well as to understand the complexities of the fluorescence emission-excitation matrix (EEM) of water-soluble organic matter (WSOM) extracted from sewage sludge samples obtained with different origins and stabilization procedures. The variation in the composition of WSOM in the different sewage sludge samples could be correlated with the conditions of stabilization; therefore, the use of fluorescence spectroscopy to monitor these changes can be a useful tool to optimize the management of this residual flux, avoiding environmental pollution. However, the “contour density” EEM maps obtained with fluorescence present continuous spectra with different peaks, valleys, and shoulders where manual peak picking can be complicated and subjective, especially in complex matrixes such as sewage sludge. With the PARAFAC algorithm, it is possible to resolve the emission and excitation spectra of the different fluorescence components present in the samples and their contribution to the total fluorescence. Also, the contribution (scores) of the different fluorophors can be coupled with another chemometric tool to provide an effective classification method using the stabilization conditions of sewage sludge as main criterion. In this study, a wide survey of sewage sludge samples (287) was characterized by fluorescence emission-excitation matrix. The final molecular composition of the sewage sludge samples was not related to the stabilization (aerobic vs anaerobic) treatments. However, a sewage sludge classification based on a combined spectroscopic-chemometric approach was obtained, which could be used for the optimization of sewage sludge use in agriculture, minimizing the environmental risks.

Molecular characteristics of the water soluble organic matter in size-fractionated aerosols collected over the North Atlantic Ocean

Size-fractionated aerosol impactor samples (n=3) representing North American, North African, and marine air mass influences were collected over the North Atlantic Ocean as part of the 2011 US GEOTRACES cruise (GEOTRACES GA03), and a molecular-level chemical characterization of the water soluble organic matter (WSOM) was obtained using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Remarkable differences were found between the molecular characteristics of WSOM from the fine (<0.49μm) and coarse size fractions demonstrating the importance of collecting size-fractionated aerosols in order to obtain a full molecular characterization of aerosol WSOM. The greatest molecular complexity, as defined by the number of formulas in each fraction, was found in the <0.49μm fraction of North American and North African-influenced aerosols, and in the >7.2μm fraction of marine-influenced aerosols. Principal component analysis (PCA) showed the <0.49μm fraction of the North American-influenced WSOM to be differentiated from all other size fractions by the prevalence of highly oxidized compounds, an indicator of atmospheric aging. The coarse fractions of the North American-influenced sample showed evidence of important contributions from low O/C (<0.2) and condensed aromatic compounds indicative of primary combustion-influenced organic matter (OM). The fine fractions of the marine and North African-influenced samples showed characteristics of a primary marine biological source including peptide-like, phospholipid-like, and carbohydrate-like molecular formulas. The coarse fractions of the marine sample and the 0.49–3.0μm fraction of the North African-influenced sample were defined by molecular formulas at intermediate O/C (0.2 to 0.6) and high H/C (>1.5) ratios including many heteroatom (N, S, P) containing formulas. Condensed aromatic compounds, which originate from anthropogenic sources and can affect the global climate by absorbing solar radiation, as well as compounds that can be attributed to secondary organic aerosols (SOA), were found in all 17 WSOM fractions analyzed. This indicates the ubiquitous nature of these types of compounds across aerosol size fractions and air mass influences, even in aerosols collected over the middle of the ocean. These results provide an indication of size-fractionated aerosol composition, and future molecular characterization work should be paired with physical characteristics to inform size-fractionated and source-resolved models of aerosol OM impacts in the atmosphere.

Углеводородный состав водорастворенного органического вещества пластовых вод девона в термоградиентном поле Матросовского месторождения Южно-Татарского свода

Углеводородный состав водорастворенного органического вещества пластовых вод девона в термоградиентном поле Матросовского месторождения Южно-Татарского свода

Aerosol water soluble organic matter characteristics over the North Atlantic Ocean: Implications for iron-binding ligands and iron solubility

Aerosol water soluble organic carbon (WSOC) and iron (Fe) loadings were examined in aerosols collected during the 2011 US GEOTRACES cruise in the North Atlantic Ocean to explore the feasibility of a role for water soluble organic matter (WSOM) organic complexation in determining the higher fractional solubility of Fe (%FeS) observed in North American-influenced relative to North African-influenced aerosols. Proton nuclear magnetic resonance spectroscopy (1H NMR) was employed to characterize the WSOM, and principal component analysis was then applied to differentiate North American-influenced from North African-influenced aerosol WSOM and provide clues to the molecular identities of organic ligands. As has been found in previous studies, North African-influenced samples had orders of magnitude higher total Fe (FeT) loadings (8.9–101nmol Fe m−3 air) and orders of magnitude lower %FeS (0.12–0.29%) than those found in North American-influenced (FeT: 0.03–1.4nmol Fe m−3 air; %FeS: 0.67–3.62%) and Marine (minimal recent continental influence; FeT: 0.02–0.25nmol Fe m−3 air; %FeS: 1.1–10.7%) samples. Aerosol %FeS values were positively correlated with WSOC/FeT ratios with North American combustion-influenced (39–540) and Marine (30–850) aerosol samples having orders of magnitude more moles of WSOC per mole of FeT than North African (0.42–3.8) aerosol samples. The high WSOC/FeT ratios in the North American combustion-influenced samples suggest a realistic role for organic ligands binding with Fe and accounting for some portion of the higher aerosol %FeS also observed for these samples. Principal component analyses of 1H NMR spectra show North American-influenced aerosol WSOM to have higher contributions from hydrogens in aliphatic carbon chains attached to heteroatomic functional groups such as those in nitrate, amine, ether, ester, and carboxylate compounds compared to North African mineral dust-influenced aerosol WSOM. These multifunctional aliphatic WSOM compounds are suggested as candidate Fe binding ligands to be explored with future work.

Effect of the soil treated with biochar on the rye-grass in laboratory experiment

Abstract The application of biochars to improve soils and to mitigate global climate change is a popular research area all over the world, although it is not a new topic. In our study, wood chips char (BC) and animal bone char (ABC) were applied. The pot experiments were conducted under laboratory conditions. 2 grams of rye-grass (Lolium perenne) were seeded into each pot. The following various soil parameters were measured: pH (KCl), AL-P2O5, AL-K2O, total water soluble salt content and organic matter content. The measured parameters from the plant samples were: total-P, total-K and micronutrients. Results show that the negative or positive effect of pyrolysis solids cannot be determined clearly, further experiments are needed.

Highway Proximity and Black Carbon from Cookstoves as a Risk Factor for Higher Blood Pressure in Rural China

Highway Proximity and Black Carbon from Cookstoves as a Risk Factor for Higher Blood Pressure in Rural ChinaAbstract Number:2455 Jill Baumgartner*, YuanXun Zhang, James Schauer, Yuqin Wang, Wei Huang, and Majid Ezzati Jill Baumgartner* McGill University, Canada, E-mail Address: [email protected] Search for more papers by this author , YuanXun Zhang University of the Chinese Academy of Sciences, China, E-mail Address: [email protected] Search for more papers by this author , James Schauer University of Wisconsin, United States, E-mail Address: [email protected] Search for more papers by this author , Yuqin Wang University of the Chinese Academy of Sciences, China, E-mail Address: wangyuqin[email protected] Search for more papers by this author , Wei Huang University of the Chinese Academy of Sciences, China, E-mail Address: [email protected] Search for more papers by this author , and Majid Ezzati Imperial College London, United Kingdom, E-mail Address: [email protected] Search for more papers by this author AbstractAir pollution in Asia poses large health risks and is a major contributor to climate change. The composition of air pollution from different sources affects its impact on climate and possibly human health. We enrolled 280 Chinese women >25 years old cooking with wood chimney stoves, and measured their blood pressure, distance to major traffic routes, and 24-hr personal exposure to PM2.5, black carbon (BC), water soluble organic matter (WSOM; organic aerosol from biomass burning) and hopanes (motor vehicle emissions) in winter and summer. We used mixed-effects models to estimate associations between air pollutants and blood pressure. Women’s mean 24-hr PM2.5 exposure was 88 µg/m3 (range: 9-634); their WSOM exposure was considerably higher than BC (mean: 34 vs. 5 µg/m3). A 1-ln(µg/m3) increase in BC had the strongest association with systolic blood pressure (4.3 mmHg; p<0.001), followed by PM2.5 mass and WSOM (Fig. 1), with similar effects for diastolic blood pressure. The effect of BC on blood pressure was nearly three times larger in women living near the highway (systolic: 6.2 mmHg, 95% CI: 3.6, 8.9 vs. 2.6 mmHg, 95% CI: 0.1, 5.2), though BC exposures were similar. Mean hopane exposure was higher among women in the village closest (70 m) to the highway compared with women in the village farthest (550 m) from the highway (4.6 vs. 1.1 ng/m3; p<0.001). We found that exposure to BC from combustion emissions is more strongly associated with blood pressure than PM2.5 or WSOM, and that BC’s health effect is larger among women co-exposed to wood smoke and motor vehicles.

Fog occurrence and chemical composition in the Po valley over the last twenty years

Frequency of fog events together with fog water chemical composition, pH, conductivity and liquid water content have systematically been measured from the end of the 1980's at the field station of San Pietro Capofiume, in the eastern Po Valley, Northern Italy. In agreement with what has been observed in other regions in Europe, fog frequency (visibility < 1 km) has decreased over the last three decades. Ionic strength and conductivity of fog samples also decreased over the period indicating a reduction of the ionic load of the droplets. Specifically, the three major inorganic ions (NH4+, SO42−, NO3−), accounting for 86% of the total fog water ionic strength, show a decreasing trend in concentration over the period, which can be linked to the decreasing trend of NH3, SO2 and NOx emissions registered in northern Italy over the same period. Sulphate exhibits the highest relative decrease (76%). Seasonal volume-weighted means of pH show an increasing trend over the observed period. The available data of total water-soluble organic matter concentrations indicate that organic compounds represent a considerable fraction (25% on average) of the total solute mass of fog water. Fog water samples often contain suspended insoluble particles, which were collected by filtering fog water through quartz fibre filters. EC-OC analysis performed on the filters collected over a four-year period, show that the sum of elemental carbon (EC) and water-insoluble organic mass accounts on average for 46%–56% of the total suspended material mass. Insoluble carbonaceous material is composed mainly of organic matter, with EC accounting on average only for 19% of the insoluble carbon.

Distinguishing molecular characteristics of aerosol water soluble organic matter from the 2011 trans-North Atlantic US GEOTRACES cruise

Abstract. The molecular characteristics of aerosol organic matter (OM) determines to a large extent its impacts on the atmospheric radiative budget and ecosystem function in terrestrial and aquatic environments, yet the OM molecular details of aerosols from different sources are not well established. Aerosol particulate samples with North American-influenced, North African-influenced, and marine (minimal recent continental influence) air mass back trajectories were collected as part of the 2011 trans-North Atlantic US GEOTRACES cruise and analyzed for their water soluble OM (WSOM) molecular characteristics using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Principal component analysis (PCA) separated the samples into five groups defined by distinct molecular formula characteristics. An abundance of nitrogen containing compounds with molecular formulas consistent with amino acid derivatives defined the two samples comprising the primary marine group (henceforth referred to as Primary Marine), which suggest a primary marine biological source to their WSOM in spite of their North American-influenced air mass trajectories. A second group of samples (aged marine, henceforth referred to as Aged Marine) with marine air mass trajectories was characterized by an abundance of low O / C (0.15–0.45) sulfur containing compounds consistent with organosulfate compounds formed via secondary aging reactions in the atmosphere. Several samples having North American-influenced air mass trajectories formed another group again characterized by organosulfate and nitrooxyorganosulfate type compounds with higher O / C ratios (0.5–1.0) than the Aged Marine samples reflecting the combustion influence from the North American continent. All the samples with North African-influenced air mass trajectories were grouped together in the PCA and were characterized by a lack of heteroatom (N, S, P) containing molecular formulas covering a wide O / C range (0.15–0.90) reflecting the desert source of this WSOM. The two marine groups showed molecular formulas that, on average, had higher H / C ratios and lower O / C ratios and modified aromaticity indices than the two continentally influenced groups, which suggests that these properties are characteristic of marine vs. continental aerosol WSOM. The final sample group, the mixed source samples (henceforth referred to as Mixed Source), showed intermediate molecular characteristics, which suggests no dominant continental or marine source. The source-specific OM details described here will aid efforts to link aerosol OM source with molecular characteristics and impacts in the environment.

Insights into the composition and sources of rural, urban and roadside carbonaceous PM₁₀.

Insights into the nature and sources of the urban and roadside increments in carbonaceous PM10 are gained from bulk chemical analyses on daily filter samples collected at a roadside, urban background and rural site in Edinburgh, UK (not all sampling contemporaneous). The concentrations of PM10 water-soluble organic matter (WSOM) at the three sites were similar, and (where measured concurrently) strongly correlated, indicating a uniform background source, in contrast to the black carbon component (quantified by filter optical reflectance) whose average concentrations at urban background and roadside were, respectively, about 3 and 7 times greater than at the rural site, indicating local urban sources. BC was not a major component of PM10 but was a major component of the urban and roadside PM10 increments (∼50% and ∼60% respectively). The roadside WSOM had greater hydrophobicity than the urban background WSOM. UV-vis spectra indicated increased prevalence of unsaturated bonds and conjugation in urban background WSOM in winter compared with summer. This is consistent with both summertime photochemical production of particle OM and maritime primary aliphatic WSOM. Raman microscopy of a small subset of samples indicated carbon functionality ranged between diesel-like material and more complex humic-like material. Results overall indicate the presence of a background functionalized carbonaceous material, with local BC sources superimposed.

Hydrophilic and hydrophobic fractions of water-soluble organic matter in digestates obtained from different organic wastes

Up to now, it is unknown how anaerobic digestion of biowastes affects the chemical composition of water-soluble organic matter (WSOM) in the digestate and, thus, the potential distribution and mobility of hydrophobic organic contaminants. The aim of the present work was to estimate the proportions of hydrophilic (HI) and hydrophobic (HO) fractions of WSOM in anaerobic digestates obtained from different mixtures of biomass. The overall goal was correlating proportions of HI and HO fractions to the different chemical characteristics of the biowastes subjected to anaerobic digestion. More than 70% of WSOM was with the HI fractions of digestates derived from 1:1 mixtures of the organic part of municipal solid wastes and sewage sludge. Larger HO fractions were observed for digestates derived from energy crop plus smaller contributions of poultry manure, stomach residue, and apple residues, likely due to the concentration of fibers during the digestion. Ratios between HO fractions in digestates and in their corresponding ingestates were used as indicators of the transformation of WSOM during the process.

Extending the analytical window for water-soluble organic matter in sediments by aqueous Soxhlet extraction

Dissolved organic matter (DOM) in marine sediments is a complex mixture of thousands of individual constituents that participate in biogeochemical reactions and serve as substrates for benthic microbes. Knowledge of the molecular composition of DOM is a prerequisite for a comprehensive understanding of the biogeochemical processes in sediments. In this study, interstitial water DOM was extracted with Rhizon samplers from a sediment core from the Black Sea and compared to the corresponding water-extractable organic matter fraction (<0.4μm) obtained by Soxhlet extraction, which mobilizes labile particulate organic matter and DOM. After solid phase extraction (SPE) of DOM, samples were analyzed for the molecular composition by Fourier Transform Ion-Cyclotron Resonance Mass Spectrometry (FT-ICR MS) with electrospray ionization in negative ion mode. The average SPE extraction yield of the dissolved organic carbon (DOC) in interstitial water was 63%, whereas less than 30% of the DOC in Soxhlet-extracted organic matter was recovered. Nevertheless, Soxhlet extraction yielded up to 4.35% of the total sedimentary organic carbon, which is more than 30-times the organic carbon content of the interstitial water. While interstitial water DOM consisted primarily of carbon-, hydrogen- and oxygen-bearing compounds, Soxhlet extracts yielded more complex FT-ICR mass spectra with more peaks and higher abundances of nitrogen- and sulfur-bearing compounds. The molecular composition of both sample types was affected by the geochemical conditions in the sediment; elevated concentrations of HS- promoted the early diagenetic sulfurization of organic matter. The Soxhlet extracts from shallow sediment contained specific three- and four-nitrogen-bearing molecular formulas that were also detected in bacterial cell extracts and presumably represent proteinaceous molecules. These compounds decreased with increasing sediment depth while one- and two-nitrogen-bearing molecules increased, resulting in a higher similarity of both sample types in the deep sediment. In summary, Soxhlet extraction of sediments accessed a larger and more complex pool of organic matter than present in interstitial water DOM.

Chemical characterization and source apportionment of indoor and outdoor fine particulate matter (PM2.5) in retirement communities of the Los Angeles Basin

Concurrent indoor and outdoor measurements of fine particulate matter (PM2.5) were conducted at three retirement homes in the Los Angeles Basin during two separate phases (cold and warm) between 2005 and 2006. Indoor-to-outdoor relationships of PM2.5 chemical constituents were determined and sources of indoor and outdoor PM2.5 were evaluated using a molecular marker-based chemical mass balance (MM-CMB) model. Indoor levels of elemental carbon (EC) along with metals and trace elements were found to be significantly affected by outdoor sources. EC, in particular, displayed very high indoor-to-outdoor (I/O) mass ratios accompanied by strong I/O correlations, illustrating the significant impact of outdoor sources on indoor levels of EC. Similarly, indoor levels of polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes were strongly correlated with their outdoor components and displayed I/O ratios close to unity. On the other hand, concentrations of n-alkanes and organic acids inside the retirement communities were dominated by indoor sources (e.g. food cooking and consumer products), as indicated by their I/O ratios, which exceeded unity. Source apportionment results revealed that vehicular emissions were the major contributor to both indoor and outdoor PM2.5, accounting for 39 and 46% of total mass, respectively. Moreover, the contribution of vehicular sources to indoor levels was generally comparable to its corresponding outdoor estimate. Other water-insoluble organic matter (other WIOM), which accounts for emissions from uncharacterized primary biogenic sources, displayed a wider range of contributions, varying from 2 to 73% of PM2.5, across all sites and phases of the study. Lastly, higher indoor than outdoor contribution of other water-soluble organic matter (other WSOM) was evident at some of the sites, suggesting the production of secondary aerosols as well as direct emissions from primary sources (including cleaning or other consumer products) at the indoor environments.