Water-soluble Organic Fraction Research Articles

Chemical Characterization and Source Apportionment of PM10 Using Receptor Models over the Himalayan Region of India

This study presents the source apportionment of coarse-mode particulate matter (PM10) extracted by 3 receptor models (PCA/APCS, UNMIX, and PMF) at semi-urban sites of the Indian Himalayan region (IHR) during August 2018–December 2019. In this study, water-soluble inorganic ionic species (WSIIS), water-soluble organic carbon (WSOC), carbon fractions (organic carbon (OC) and elemental carbon (EC)), and trace elements of PM10 were analyzed over the IHR. Nainital (62 ± 39 µg m−3) had the highest annual average mass concentration of PM10 (average ± standard deviation at 1 σ), followed by Mohal Kullu (58 ± 32 µg m−3) and Darjeeling (54 ± 18 µg m−3). The annual total ∑WSIIS concentration order was as follows: Darjeeling (14.02 ± 10.01 µg m−3) > Mohal-Kullu (13.75 ± 10.21 µg m−3) > Nainital (10.20 ± 6.30 µg m−3), contributing to 15–30% of the PM10 mass. The dominant secondary ions (NH4+, SO42−, and NO3−) suggest that the study sites were strongly influenced by anthropogenic sources from regional and long-range transport. Principal component analysis (PCA) with an absolute principal component score (APCS), UNMIX, and Positive Matrix Factorization (PMF) were used for source identification of PM10 at the study sites of the IHR. All three models showed relatively similar results of source profiles for all study sites except their source number and percentage contribution. Overall, soil dust (SD), secondary aerosols (SAs), combustion (biomass burning (BB) + fossil fuel combustion (FFC): BB+FFC), and vehicular emissions (VEs) are the major sources of PM10 identified by these models at all study sites. Air mass backward trajectories illustrated that PM10, mainly attributed to dust-related aerosols, was transported from the Thar Desert, Indo-Gangetic Plain (IGP), and northwestern region of India (i.e., Punjab and Haryana) and Afghanistan to the IHR. Transported agricultural or residual burning plumes from the IGP and nearby areas significantly contribute to the concentration of carbonaceous aerosols (CAs) at study sites.

Assessing the impacts of CPM emitted from stationary sources on PM2.5 source appointment of Wuhan, China

The condensable particulate matter (CPM) emissions from stationary sources have attracted widespread attentions due to its negative environmental impacts. In this study, we collected some CPM samples from fourteen different stationary sources in Wuhan based on the US EPA Method 202 for investigating emission factors (EFs) and source profiles of the CPM, as well as its impact on source apportionment of PM2.5 (particulate matter with aerodynamic diameters ≤ 2.5 µm). The CPM mass concentrations and chemical components including water-soluble ions, elements and organic fractions in the CPM were explicitly analyzed. Our results revealed that the emission level of CPM was 0.8 to 14 times that of filterable particulate matter (FPM). The EF of CPM from coal-fired power plant was 168.91 g/t of coal, that was about 1–28 times higher than other stationary sources tested in this study. Alkanes (4 %–35 %), esters (9 %–46 %), and water-soluble ions (24 %–64 %) were dominant chemical species in the CPM, which significantly differed from that of the FPM. As such, we built a new emission inventory that included CPM and applied it to the chemical mass balance (CMB) model for source apportionment of PM2.5. The results showed that the contribution of stationary sources to PM2.5 increased from 17 % to 23 %, while the contribution of vehicle sources to PM2.5 decreased from 16 % to 11 % when considering the impact of CPM. In addition, isotope values of δ13C and δ15N in the CPM were measured to apportion the sources of carbon and nitrogen in aerosols. We found that the contributions of vehicle sources to carbon and nitrogen components in PM2.5 decreased by 3 % to 5 %, contribution of coal combustion sources increased by 6 % to 8 %, when considering the impact of CPM. Therefore, it is necessary to update emission inventory by including the CPM in further research for a greater accuracy of the source apportionment of PM2.5. This study has important implications for achieving improved air quality management via emission mitigation of CPM from stationary sources at the local, regional, and national scales.

Treatment Technologies for Organics and Silica Removal in Steam-Assisted Gravity Drainage Produced Water: A Comprehensive Review

Produced water from steam-assisted gravity drainage (SAGD) operations is a complex mixture of inorganic and organic constituents. Silica, carbonate and bicarbonate, and hardness are three inorganic constituents of interest, whereas the organic contaminants are composed of free and emulsified oil (F&EO) and water-soluble organic (WSO) fractions. Although the current warm lime softening (WLS) and hot lime softening (HLS) in SAGD operations are able to remove particles, silica, and organics, improving the removal efficiency of organics and silica still faces technical and operational challenges given their complex chemistry in produced water. Much effort has been put toward developing effective and cost-efficient treatment processes to handle organics and silica. In this work, we have systematically reviewed the properties of silica and the characteristics of dissolved organics in SAGD produced water, as well as the working principle and removal mechanisms of several techniques, including membrane technology, adsorption, coagulation–flocculation, and hybrid processes. Different analytical techniques for characterizing dissolved organics have been assessed, and the dominant and representative organic species in produced water have been identified. The advantages and limitations, impact factors, application performance, and effectiveness of each technology have been discussed in terms of the removal efficiency for silica and organics. Some remaining challenges and perspectives for future research are also presented. This work provides an improved understanding of the characteristics of silica and organics in SAGD produced water, as well as different treatment technologies, with useful implications for developing effective, feasible, and cost-efficient treatment processes with the objective of enhancing the removal of silica and organics from produced water, thereby leading to economic and environmental performance improvements.

Assessing the Biological Value of Soluble Organic Fractions from Tomato Pomace Digestates

Anaerobic digestion is proposed for sustainable exploitation of the huge amounts of residues produced yearly by tomato processing. The aim of this study was to analyze the biological effects of water-soluble organic fractions of tomato pomace digestates applied on soil and plant, at a laboratory scale. Digestates are derived from a short-term dark fermentation batch experiment of tomato pomace and buffalo slurry at three decreasing ratios (12:1, 8:1, and 6:1, respectively Set 1, Set 2, and Set 3). Bioassays on soil and plant were carried out after addition of different amounts of dissolved organic carbon (DOC) extracted from the three sets: microbial pool content, respiration activity, root development, and cell division were considered. Digestate from Set 1 showed the highest content of volatile fatty acids (about 80 mg UL−1), suggesting an efficient fermentation process which led to lower water solubility of organic substrates. The highest carbon mineralization rate in soil (4.29%) occurred with DOC additions from Set 1 (p 0.05) was detected in the micronuclei assay. Soluble organic forms of these digestates are a nutrient source for soil microorganism metabolism and at low doses show a hormonal-like action, without toxicological or genotoxicity effects on soil biota and root cell.

Year-round measurements of size-segregated low molecular weight organic acids in Arctic aerosol

Organic acids in aerosols Earth's atmosphere are ubiquitous and they have been extensively studied across urban, rural and polar environments. However, little is known about their properties, transport, source and seasonal variations in the Svalbard Archipelago. Here, we present the annual trend of organic acids in the aerosol collected at Ny-Ålesund and consider their size-distributions to infer their possible sources and relative contributions. A series of carboxylic acids were detected with a predominance of C2-oxalic acid. Pinic acid and cis-pinonic acid were studied in order to better understand the oxidative and gas-to-particle processes occurred in the Arctic atmosphere. Since the water-soluble organic fraction is mainly composed by organic acids and ions, we investigated how the seasonal variation leads to different atmospheric transport mechanisms, focusing on the chemical variations between the polar night and boreal summer. Using major ions, levoglucosan and MSA, the Positive Matrix Factorization (PMF) identified five different possible sources: a) sea spray; b) marine primary production; c) biomass burning; d) sea ice related process and e) secondary products.

Nuclear Magnetic Resonance Aerosolomics: A Tool for Analysis of Polar Compounds in Atmospheric Aerosols.

Nuclear magnetic resonance aerosolomics was proposed as a new approach to the analysis of the water-soluble organic compound fraction in aerosol particulate matter. The identification of individual compounds is based on a comparison of precise chemical shifts in the 1H NMR spectrum with the signals in the standards library. For this purpose, Chenomx metabolomics software and a comprehensive spectra library of 150 compounds known from chemistry of aerosols were used. This approach enabled the identification of 60 compounds in real aerosol samples collected at a suburban site in Prague. Using the metabolomic spectra library, three new compounds were identified in aerosols for the first time, and an association of four other compounds to the atmospheric particulate matter was confirmed. The obtained concentration profiles of all identified chemical individuals were subsequently subjected to advanced statistical analysis. NMR aerosolomics clearly differentiates between summer and winter aerosol samples via multivariate statistical analysis and revealed some interesting trends in composition, according to aerosol particle size. Furthermore, the univariate statistical analysis was applied to highlight compounds responsible for the group separation, and possible sources of these compounds were suggested.

Biomass burning organic aerosols significantly influence the light absorption properties of polarity-dependent organic compounds in the Pearl River Delta Region, China

Atmospheric brown carbon (BrC) is an important constituent of light-absorbing organic aerosols with many unclear issues. Here, the light-absorption properties of BrC with different polarity characteristics at a regional site of Pearl River Delta Region during 2016–2017, influenced by sources and molecular compositions, were revealed using radiocarbon analysis and Fourier transform ion cyclotron resonance mass spectrometry. Humic-like substance (HULIS), middle polar (MP), and low polar (LP) carbon fractions constitute 46 ± 17%, 30 ± 7%, and 7 ± 3% of total absorption coefficient from bulk extracts, respectively. Our results show that the absorption proportions of HULIS and MP to the total BrC absorption are higher than their mass proportions to organic carbon mass, indicating that HULIS and MP are the main light-absorbing components in water-soluble and water-insoluble organic carbon fractions, respectively. With decreases in non-fossil HULIS, MP, and LP carbon fractions (66 ± 2%, 52 ± 2%, and 36 ± 3%, respectively), the abundances of unsaturated compounds and mass absorption efficiency at 365 nm of three fractions decreased synchronously. Increases in both non-fossil carbon and levoglucosan in winter imply that the enhanced light-absorption could be attributed to elevated levels of biomass burning organic aerosols (BBOA), which increases the number of light-absorbing nitrogen-containing compounds. Moreover, the major type of potential BrC in HULIS and MP carbon fractions are oxidized BBOA, but the potential BrC chromophores in LP are mainly associated with primary BBOA. This study reveals that biomass burning has adverse effects on radiative forcing and air quality, and probably indicates the significant influences of atmospheric oxidation reactions on the forms of chromophores.

Molecular composition and photochemical evolution of water-soluble organic carbon (WSOC) extracted from field biomass burning aerosols using high-resolution mass spectrometry

Abstract. Photochemistry plays an important role in the evolution of atmospheric water-soluble organic carbon (WSOC), which dissolves into clouds, fogs, and aerosol liquid water. In this study, we tentatively examined the molecular composition and evolution of a WSOC mixture extracted from field-collected wheat straw burning aerosol (WSBA) samples upon photolysis, using direct infusion electrospray ionisation (ESI) coupled to high-resolution mass spectrometry (HRMS) and liquid chromatography (LC) coupled with HRMS. For comparison, two typical phenolic compounds (i.e. phenol and guaiacol) emitted from lignin pyrolysis in combination with hydrogen peroxide (H2O2) as a typical OH radical precursor were simultaneously exposed to simulated sunlight irradiation. Their photochemical products such as phenolic dimers (e.g. m∕z 185.0608 for phenol dimer and m∕z 245.0823 for guaiacol dimer) or their isomers, were also observed in field-collected WSBA samples, suggesting that the aqueous-phase reactions might contribute to the formation of emitted biomass burning aerosols. The aqueous photochemistry of both the phenols (photooxidation) and WSBA extracts (direct photolysis) could produce a series of highly oxygenated compounds, which in turn increases the oxidation degree of organic composition and acidity of the bulk solution. In particular, the LC/ESI-HRMS technique revealed significant photochemical evolution of the WSOC composition in WSBA samples, e.g. the photodegradation of low oxygenated species and the formation of highly oxygenated products. We also tentatively compared the mass spectra of photolytic time-profile WSBA extracts with each other for a more comprehensive description of the photolytic evolution. The calculated average oxygen-to-carbon ratio (O∕C) of oxygenated compounds in bulk extract increases from 0.38±0.02 to 0.44±0.02 (mean ± standard deviation), while the intensity (S∕N)-weighted average O∕C (O∕Cw) increases from 0.45±0.03 to 0.53±0.06 as the time of irradiation extends from 0 to 12 h. These findings indicate that the water-soluble organic fraction of combustion-derived aerosols has the potential to form more oxidised organic matter, contributing to the highly oxygenated nature of atmospheric organic aerosols.

Modelling the hygroscopic growth factors of aerosol material containing a large water-soluble organic fraction, collected at the Storm Peak Laboratory

The compositions of six aggregated aerosol samples from the Storm Peak Laboratory site have been comprehensively analysed (Hallar et al., 2013), focusing particularly on the large water-extractable organic fraction which consists of both high molecular weight organic compounds and a range of acids and sugar-alcohols. The contribution of the soluble organic fraction of atmospheric aerosols to their hygroscopicity is hard to quantify, largely because of the lack of a detailed knowledge of both composition and the thermodynamic properties of the functionally complex compounds and structures the fraction contains. In this work we: (i) develop a means of predicting the relative solubility of the compounds in the water-extractable organic material from the Storm Peak site, based upon what is known about their chemical composition; (ii) derive the probable soluble organic fraction from comparisons of model predictions with the measured hygroscopicity; (iii) test a model of the water uptake of the total aerosol (inorganic plus total water-extractable organic compounds). Using a novel UNIFAC-based method, different assignments of functional groups to the high molecular weight water soluble organic compounds (WSOC) were explored, together with their effects on calculated hygroscopic growth factors, constrained by the known molecular formulae and the double bond equivalents associated with each molecule. The possible group compositions were compared with the results of ultrahigh resolution mass spectrometry measurements of the organic material, which suggest large numbers of alcohol (–OH) and acid (–COOH) groups. A hygroscopicity index (HI) was developed. The measured hygroscopic growth is found to be consistent with a dissolution of the WSOC material that varies approximately linearly with RH, such that the dissolved fraction is about 0.45–0.85 at 90% relative humidity when ordering by HI, depending on the assumptions made. This relationship, if it also applies to other types of organic aerosol material, provides a simple approach to calculating both water uptake and CCN activity (and the κ parameter for hygroscopic growth). The hygroscopicity of the total aerosol was modelled using a modified Zdanovskii-Stokes-Robinson approach as the sum of that of the three analysed fractions: inorganic ions (predicted), individual organic acids and “sugar alcohols” (predicted), and the high molecular weight WSOC fraction (measured). The calculated growth factors broadly agree with the measurements, and validate the approach taken. The insights into the dissolution of the organic material seem likely to apply to other largely biogenic secondary organic aerosols from similar remote locations.

High molecular weight humic-like substances in carboneous aerosol of Ulaanbaatar city

Total carbon content of the atmospheric suspended particulate matters consisted of as high as 89-93% organic carbon (OC) in Ulaanbaatar aerosol without showing seasonal variation. However, limited aerosol measurements have been conducted on these OC rich aerosols particularly for high molecular weight constituents. In order to address the gap above, abundance of high molecular weight humic-like substances (HULIS) in total suspended particulates (TSP) from Ulaanbaatar atmospheric aerosol were determined for the first time. HULIS molecular structure was characterised for different seasons using carbon content and UV absorbance measurements coupled with solid phase extraction methods. Although, HULIS contributions to water soluble organic fraction of the winter and summer aerosols were similar HULIS carbon concentration was higher in winter samples (9-37 mg·L-1) than in summer (2-6 mg·L-1). Consequently quantity of aromatic moieties and degree of aromaticity varied between seasons.

Influence of ryegrass on physico-chemical properties of a fragipan soil

Fragipan horizons are naturally occurring impermeable layers found in certain soil types which constrain crop yields. While abundant literature exists regarding the processes of fragipan genesis, there is little recognition given to potential alterations in the pan with surface management, particularly important in light of the fact that these horizons can occur near the surface. We collected soil cores from a Zanesville silt loam (Typic Fragiudalf) and seeded them to annual ryegrass in the greenhouse and determined relevant soil properties after one growing cycle. The presence of ryegrass lowered bulk densities in the Btx1 and Btx2 horizons by 8% and 6% when compared with the counterpart horizons in the control, suggesting an increase in porosity. These findings were paralleled by a 62% and 52% reduction in tensile strength of ryegrass-grown aggregates in these same horizons when compared with control aggregates. These trends are likely due in part to solubilization of cementing agents by ryegrass root exudates. Glycolate, azelaic acid, and diphenolics appeared as components of the water soluble organic fraction (WSOC) pool and the diphenolics were in greater concentrations in ryegrass soil cores. Diphenolic concentrations were associated with elevated water-soluble aluminum and iron levels, suggesting that ryegrass might be solubilizing these cementing agents and affecting bulk density. Biological drilling by ryegrass roots might also be involved to increase porosity in fragipan horizons. Our findings raise questions about the ability of ryegrass to ameliorate impermeable subsurface fragipan horizons and how the improvement in porosity might impact subsequent row crop production.

Chemical composition of fine particles (PM2.5): water-soluble organic fraction and trace metals

The chemical composition of the atmosphere changes rapidly due to the amount of air pollutants released every day. The aim of this research was to make an exploratory study on the chemical composition (metals and water-soluble organic fraction) of fine particulate matter (PM2.5) in a region with tropical climate. Multiple sites, with and without the influence of the construction works for the World Cup and Olympic Games, were selected in Rio de Janeiro State, RJ, Brazil. PM2.5 samples were collected every 6 days from January to December 2011. This is the first PM2.5 data generated by RJ’s monitoring network. The PM2.5 annual average concentrations in Rio de Janeiro ranged from 9 to 32 μg m−3. Metals originated from industrial (Cu, Cd, Pb) and traffic (Cr, Mn, Ni, V, and Zn) emissions, as well as those from natural emissions (Na, K, Ca, Ti, Al, Mg, Fe), were quantified. The concentrations of the metals analyzed ranged from 0.4 to 13,000 ng m−3. The highest concentrations found were related to metals present in the crust, such as Al (1.6 to 6.7 μg m−3). In the places where there was the presence of railroad minerals, Ca and Mg appeared in higher concentrations than in the other sites. Fe and PM2.5 annual and daily average were higher in areas under construction for urban mobility improvements or the Olympic arenas. Even though, the results for Ni, Pb, and Cu were 50% below WHO guidelines. Water-soluble organic carbon (WSOC) concentrations ranged from 0.8 to 4.9 μg m−3. The highest concentrations (2.4 to 4.9 μg m−3) were observed in urban areas with intense light vehicle fleet traffic as well as in areas of large industrial influence near highways with intense circulation of heavy vehicles. This is due to the fact that WSOC is mainly formed by the emissions from combustion processes. Studies are needed in order to assess to which extent the WSOC can increase the bioavailability of these and other metals.

Contribution of dissolved organic matter to submicron water-soluble organic aerosols in the marine boundary layer over the eastern equatorial Pacific

Abstract. Stable carbon isotopic compositions of water-soluble organic carbon (WSOC) and organic molecular markers were measured to investigate the relative contributions of the sea surface sources to the water-soluble fraction of submicron organic aerosols collected over the eastern equatorial Pacific during the Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOCs (TORERO)/KA-12-01 cruise. On average, the water-soluble organic fraction of the total carbon (TC) mass in submicron aerosols was ∼ 30–35 % in the oceans with the low chlorophyll a (Chl a) concentrations, whereas it was ∼ 60 % in the high-Chl a regions. The average stable carbon isotope ratio of WSOC (δ13CWSOC) was −19.8 ± 2.0 ‰, which was systematically higher than that of TC (δ13CTC) (−21.8 ± 1.4 ‰). We found that in the oceans with both high and low Chl a concentrations the δ13CWSOC was close to the typical values of δ13C for dissolved organic carbon (DOC), ranging from −22 to −20 ‰ in surface seawater of the tropical Pacific Ocean. This suggests an enrichment of marine biological products in WSOC aerosols in the study region regardless of the oceanic area. In particular, enhanced levels of WSOC and biogenic organic marker compounds together with high values of WSOC / TC ( ∼ 60 %) and δ13CWSOC were observed over upwelling areas and phytoplankton blooms, which was attributed to planktonic tissues being more enriched in δ13C. The δ13C analysis estimated that, on average, marine sources contribute ∼ 90 ± 25 % of the aerosol carbon, indicating the predominance of marine-derived carbon in the submicron WSOC. This conclusion is supported by Lagrangian trajectory analysis, which suggests that the majority of the sampling points on the ship had been exposed to marine boundary layer (MBL) air for more than 80 % of the time during the previous 7 days. The combined analysis of the δ13C and monosaccharides, such as glucose and fructose, demonstrated that DOC concentration was closely correlated with the concentration levels of submicron WSOC across the study region regardless of the oceanic area. The result implies that DOC may characterize background organic aerosols in the MBL over the study region.

A sub-decadal trend in diacids in atmospheric aerosols in eastern Asia

Abstract. Change in secondary organic aerosols (SOAs) has been predicted to be highly uncertain in the future atmosphere in Asia. To better quantify the SOA change, we examine the sub-decadal (2001–2008) trend in major surrogate compounds (C2–C10 diacids) of SOA in atmospheric aerosols from Gosan site on Cheju Island, South Korea. The Gosan site is influenced by pollution outflows from eastern Asia. The molecular distributions of diacids were characterized by the predominance of oxalic (C2) acid followed by malonic (C3) and succinic (C4) acids in each year. The seasonal variations in diacids in each year were characterized by the highest concentrations of saturated diacids in spring and unsaturated diacids in winter. The consistent molecular distributions and seasonal variations along with significantly similar air mass transport patterns are indicative of similar pollution sources for diacids in eastern Asia on a sub-decadal scale. However, the intensity of the pollution sources has increased as evidenced by the increases in major diacids at the rate of 3.9–47.4 % per year, particularly in April. The temporal variations in atmospheric tracer compounds (carbon monoxide, levoglucosan, 2-methyltetrols, pinic acid, glyoxylic acid, glyoxal and methylglyoxal) suggest that the increases in diacids are due to enhanced precursor emissions associated with more anthropogenic than biogenic activities followed by the compounds' chemical processing in the atmosphere. The trends in diacids contrast with the reported decreases in sulfate, nitrate and ammonium in recent years in eastern Asia. This study demonstrates that recent pollution control strategies in eastern Asia were not able to decrease organic acidic species in the atmosphere. The increases in water-soluble organic acid fraction could modify the aerosol organic composition and its sensitivity to climate relevant physical properties.

Inhibition of ABC transport proteins by oil sands process affected water

The ATP-binding cassette (ABC) superfamily of transporter proteins is important for detoxification of xenobiotics. For example, ABC transporters from the multidrug-resistance protein (MRP) subfamily are important for excretion of polycyclic aromatic hydrocarbons (PAHs) and their metabolites. Effects of chemicals in the water soluble organic fraction of relatively fresh oil sands process affected water (OSPW) from Base Mine Lake (BML-OSPW) and aged OSPW from Pond 9 (P9-OSPW) on the activity of MRP transporters were investigated in vivo by use of Japanese medaka at the fry stage of development. Activities of MRPs were monitored by use of the lipophilic dye calcein, which is transported from cells by ABC proteins, including MRPs. To begin to identify chemicals that might inhibit activity of MRPs, BML-OSPW and P9-OSPW were fractionated into acidic, basic, and neutral fractions by use of mixed-mode sorbents. Chemical compositions of fractions were determined by use of ultrahigh resolution orbitrap mass spectrometry in ESI+ and ESI− mode. Greater amounts of calcein were retained in fry exposed to BML-OSPW at concentration equivalents greater than 1× (i.e., full strength). The neutral and basic fractions of BML-OSPW, but not the acidic fraction, caused greater retention of calcein. Exposure to P9-OSPW did not affect the amount of calcein in fry. Neutral and basic fractions of BML-OSPW contained relatively greater amounts of several oxygen-, sulfur, and nitrogen-containing chemical species that might inhibit MRPs, such as O+, SO+, and NO+ chemical species, although secondary fractionation will be required to conclusively identify the most potent inhibitors. Naphthenic acids (O2−), which were dominant in the acidic fraction, did not appear to be the cause of the inhibition. This is the first study to demonstrate that chemicals in the water soluble organic fraction of OSPW inhibit activity of this important class of proteins. However, aging of OSPW attenuates this effect and inhibition of the activity of MRPs by OSPW from Base Mine Lake does not occur at environmentally relevantconcentrations.

ChemInform Abstract: Unraveling the Structural Features of Organic Aerosols by NMR Spectroscopy: A Review

AbstractReview: 54 refs.

Impact of wildfires on size-resolved aerosol composition at a coastal California site

Size-resolved aerosol composition measurements were conducted at a coastal site in central California during the Nucleation in California Experiment (NiCE) between July and August of 2013. The site is just east of ship and marine emission sources and is also influenced by continental pollution and wildfires, such as those near the California–Oregon border which occurred near the end of NiCE. Two micro-orifice uniform deposit impactors (MOUDIs) were used, and water-soluble and elemental compositions were measured. The five most abundant water-soluble species (in decreasing order) were chloride, sodium, non-sea salt (nss) sulfate, ammonium, and nitrate. During wildfire periods, nss K mass concentrations were not enhanced as strongly as other species in the sub-micrometer stages and even decreased in the super-micrometer stages; species other than nss K are more reliable tracers for biomass burning in this region. Chloride levels were reduced in the fire sets likely due to chloride depletion by inorganic and organic acids that exhibited elevated levels in transported plumes. During wildfire periods, the mass size distribution of most dicarboxylic acids changed from unimodal to bimodal with peaks in the 0.32 μm and 1.0–1.8 μm stages. Furthermore, sulfate's peak concentration shifted from the 0.32 μm to 0.56 μm stage, and nitrate also shifted to larger sizes (1.0 μm to 1.8–3.2 μm stages). Mass concentrations of numerous soil tracer species (e.g., Si, Fe) were strongly enhanced in samples influenced by wildfires, especially in the sub-micrometer range. Airborne cloud water data confirm that soil species were associated with fire plumes transported south along the coast. In the absence of biomass burning, cloud condensation nuclei (CCN) composition is dominated by nss sulfate and ammonium, and the water-soluble organic fraction is dominated by methanesulfonate, whereas for the samples influenced by wildfires, ammonium becomes the dominant overall species, and oxalate is the most abundant organic species.

Unraveling the structural features of organic aerosols by NMR spectroscopy: a review.

Our limited understanding of the effect of organic aerosols (OAs) on the climate and human health is largely because of the vast array of formation processes and sources that produce a multitude of molecular structures and physical properties. The need to unravel the enormous complexity and heterogeneity of OAs and thus understand their effects on the climate and human health has led to the development of different off-line methods based on the use of advanced analytical techniques. Within this context, nuclear magnetic resonance (NMR) spectroscopy has become essential for acquiring detailed structural characterization of the complex natural organic matter contained in atmospheric aerosols. In this article, we present a critical review on the application of NMR spectroscopy in OAs (primary and secondary) studies, focusing mainly on the water-soluble organic fraction, and how NMR has impacted our knowledge on atmospheric organic matter. A major emphasis is given on the wealth of chemical information that solid-state and multi-dimensional solution-state NMR can provide, including the sources, formation pathways, seasonal, and regional characterization of atmospheric OAs. Finally, major challenges are discussed and recommendations for future research directions are proposed.

Mobility of Zinc in Heavy Metal Contaminated Soil after Compost Amendment and <i>Brassica juncea</i> Harvest

Pot experiments were performed to investigate the effect of compost amendment on the mobility of zinc through analysis of Zn fractions in heavy metal contaminated soil. The results showed that the total Zn concentration decreased 8.11%, 10.15%, 16.15%, 20.05%, 7.28% and 5.02% after the amendment of 0, 20, 40, 60, 80, 100 g/kg compost to soil and Brassica juncea harvest, respectively. Zn was mostly concentrated in the residual fraction and Fe-Mn oxides fraction in soil. The percentage of Zn in water-soluble fraction, organic fraction and residual fraction had no correlation with the amount of compost amendment. The percentage of Zn in the exchangeable fraction decreased and the percentage of Zn in Fe-Mn oxides fractions increased obviously. Furthermore, the mobility factor of Zn decreased significantly from 19.20% without compost amendment to 19.09%, 18.70%, 18.15%, 16.45% and 16.12% after the amendment of 0, 20, 40, 60, 80, 100 g/kg compost to soil, the compost amendment could lowered the mobility and phytotoxicity of zinc through bound to Fe-Mn oxides.

Possible sources of two size-resolved water-soluble organic carbon fractions at a roadway site during fall season

To examine the formation pathways of two size-resolved water-soluble organic carbon (WSOC) fractions, a total of 16 sets of size-segregated aerosol samples were collected using a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI) at a roadway site in Korea from September 29 to October 29, 2010. A XAD7HP (non-ionic aliphatic acrylic polymer) resin column was used to separate the filtered extracts into hydrophilic (WSOCHPI) and hydrophobic (WSOCHPO) WSOC fractions. Also the size distributions of water-soluble inorganic species and oxalate were examined to determine the formation pathways of size-resolved WSOCHPI and WSOCHPO fractions.The size distribution of WSOCHPI showed a dominant mode at 0.55 μm, while the WSOCHPO had dominant modes at both 0.17–0.32 μm and 0.55 μm. On the basis of the size distribution characteristics, it was found that the formation pathways of both WSOCHPI and WSOCHPO were dependent on the particle size; in the condensation mode (0.17–0.32 μm), both the WSOCHPI and WSOCHPO could be produced through atmospheric processes similar to those of SO42− and oxalate, which were derived from the gas-phase oxidations of organic compounds. In the droplet mode (0.55–1.8 μm), the cloud processing of both the organic compounds and biomass burning emissions could be a major pathway for the WSOCHPI formation. However, the droplet mode WSOCHPO was likely produced through cloud processing and heterogeneous reactions or aerosol-phase reactions. In the coarse mode (>3.1 μm), the WSOCHPI formation was more likely associated with soil-related particles (Ca(NO3)2 and CaSO4) than with sea-salt particles (NaNO3 and Na2SO4).