Water-soluble Chemical Species Research Articles

Chemical Characteristics of Atmospheric Aerosol at Alaknanda Valley (Srinagar) in the Central Himalaya Region, India

Measurements of fine (PM2.5) and inhalable (PM10) particles were collected at the Alaknanda Valley in the heart of Garhwal region during December 2015–December 2016. Collected samples of PMs were analyzed for major chemical species as anions (F−, Cl−, SO42−, NO2− and NO3−) and cations (Na+, NH4+, K+, Ca2+ and Mg2+) by ion chromatography. During the study period, the concentrations of PM2.5 and PM10 were 78.7 ± 25.1 and 111.8 ± 23.4 μg m−3, respectively. The measured chemical species were found a large variability in different seasons due to the impact of emissions and meteorological parameters. The measured water-soluble (WS) chemical species of PM2.5 and PM10 were 43% (33.7 μg m−3) and 57% (64.2 μg m−3), respectively, with the highest concentrations during the winter season followed by summer, monsoon and post-monsoon seasons. A significant positive correlation was observed between NH4+ and other species (Cl−, SO42− and NO3−) in both PM2.5 and PM10, which indicates its presence in the atmosphere as ammonium salts. As a result, NH4+ play a crucial role in neutralization of acidic species in the winter season; however, the contrary feature was observed in the summer season where Ca2+ was responsible for the main neutralizing species, mainly transported from the inland region during the summer. Principal component analysis shows that secondary aerosol, biomass burning, and soil-driven dust were the possible sources of the measured species over the station. Further, air mass back trajectory analyses indicate that the highest mass concentrations of PMs and WS chemical species were in the post-monsoon season when the air masses pass from eastern Pakistan and western part of India over receptor site. In the winter season, the concentrations of PMs and WS species were highest (second) when the air masses transported from a long distance up to Southern Afghanistan covering with Pakistan and western part of India. In overall, the study suggests the long-range transport of pollutants plays a crucial role in the enhancement of PMs over Alaknanda valley region.

Influence of haze pollution on water-soluble chemical species in PM2.5 and size-resolved particles at an urban site during fall

To investigate the influence of haze on the chemical composition and formation processes of ambient aerosol particles, PM2.5 and size-segregated aerosol particles were collected daily during fall at an urban site of Gwangju, Korea. During the study period, the total concentration of secondary ionic species (SIS) contributed an average of 43.9% to the PM2.5, whereas the contribution of SIS to the PM2.5 during the haze period was 62.3%. The NO3− and SO42− concentrations in PM2.5 during the haze period were highly elevated, being 13.4 and 5.0 times higher than those during non-haze period, respectively. The PM, NO3−, SO42−, oxalate, water-soluble organic carbon (WSOC), and humic-like substances (HULIS) had tri-modal size distributions peaks at 0.32, 1.0, and 5.2μm during the non-haze and haze periods. However, during the non-haze period they exhibited dominant size distributions at the condensation mode peaking at 0.32μm, while on October 21 when the heaviest haze event occurred, they had predominant droplet mode size distributions peaking at 1.00μm. Moreover, strong correlations of WSOC and HULIS with SO42−, oxalate, and K+ at particle sizes of <1.8μm indicate that secondary processes and emissions from biomass burning could be responsible for WSOC and HULIS formations. It was found that the factors affecting haze formation could be the local stable synoptic conditions, including the weak surface winds and high surface pressures, the long-range transportation of haze from eastern China and upwind regions of the Korean peninsula, as well as the locally emitted and produced aerosol particles.

Atmospheric significance of aeolian salts in the sandy deserts of northwestern China

Abstract. Large sandy deserts in the middle latitudes of northwestern China were investigated for soluble salt variations in modern and ancient aeolian sediments, aiming to explore the environmental significance of “aeolian salts”. Results revealed that aeolian salt variations have a clear relationship with the changing meridional and zonal gradients of the desert locations and the aeolian differentiation effect, but are weakly linked to local geological conditions. Atmospheric depositions of water-soluble chemical species are an important process/source contributing to aeolian salt. Sequential variations of soluble salts in sedimentary profiles interbedded with aeolian and non-aeolian deposits and their palaeoenvironmental implications in the hinterland areas of these deserts were further evaluated, based on the constraints of OSL dating and radiocarbon dating data. The results indicate that inorganic salts may be a latent geoproxy in revealing regional palaeoclimatic changes in desert areas for sediments deposited under a single depositional environment, but the interpretation should be more cautious for sediments deposited under diverse depositional conditions. This study presents evidence of the atmospheric origin of aeolian salt in sandy deserts, with limited climatic significance in palaeoenvironmental reconstruction.

Vapor-Deposited Pt and Pd-Pt Catalysts for Solid Acid Fuel Cells: Short Range Structure and Interactions with the CsH2PO4 Electrolyte

State-of-the-art cathodes for solid acid fuel cells (SAFCs) based on the crystalline electrolyte CsH2PO4 (CDP) are comprised of a proton-conducting CDP network coated by a vapor-deposited nanostructured catalyst. Pd-rich (85 at%Pd) Pt-Pd oxygen reduction catalysts vapor-deposited on CDP display both extraordinary activity for oxygen reduction and poor stability in cathodes for SAFCs operating at 250 °C. Similar catalysts with lower Pd content (57 at%Pd) are less active and more stable. Using X-ray absorption spectroscopy (XAS), we find that these catalysts are structurally similar and that structural variations are insufficient to explain the observed differences in activity. XAS and solid-state and solution nuclear magnetic resonance (NMR) also show that additional water-soluble chemical species are present in the Pd-rich electrode after fuel cell operation. We attribute the presence of these species to the reactivity of the Pd-rich catalyst with CsH2PO4 and suggest that these products are the cause of the observed deactivation.

Synthesis of nanopesticides by encapsulating pesticide nanoparticles using functionalized carbon nanotubes and application of new nanocomposite for plant disease treatment.

Polymerization of citric acid onto the surface of oxidized multiwall carbon nanotubes led to MWCNT-graft-poly(citric acid) (MWCNT-g-PCA) hybrid materials. Because of the presence of conjugated citric acid branches, synthesized MWCNT-g-PCA hybrid materials were not only soluble in water but also able to trap water-soluble chemical species and metal ions. Trapping of pesticides such as zineb and mancozeb in aqueous solution by MWCNT-g-PCA hybrid materials led to encapsulated pesticide (EP) in the polycitric acid shell. Optimum conditions for encapsulation of zineb and mancozeb in hyperbranched polycitric acid such as pH, time of stirring, and temperature were investigated by the UV-vis spectroscopy method. Encapsulation of pesticides on CNT-g-PCA hybrid material was confirmed via TEM analysis. Experiments indicated that new the CNT-g-PCA-EP hybrid material in comparison with bulk pesticide had a superior toxic influence on Alternaria alternata fungi.

Filterable water-soluble organic nitrogen in fine particles over the southeastern USA during summer

Time integrated high-volume PM2.5 samples were collected separately during day and night from 1 August to 10 September 2008 at a paired urban (Atlanta)-rural (Yorkville) sites as part of the August Mini-Intensive Gas and Aerosol Study (AMIGAS). Selected filters (n = 96, 48 for each site) were analyzed for a suite of water-soluble chemical species, including major inorganic ions, water-soluble organic carbon (WSOC), water-soluble total and inorganic nitrogen (WSTN and WSIN), and levoglucosan. Semi-continuous analyses of PM2.5 mass, soluble ions, WSOC, and gaseous O3, SO2, NO, NO2, NOy, CO, and meteorological parameters were also carried out in parallel. This study focuses on the characteristics of filterable water-soluble organic nitrogen (WSON), estimated by the difference in the measured concentrations of WSTN and WSIN, determined from aqueous filter extracts. At both sites, WSON varied from below the limit of detection (25 ng-N m−3) to ∼600 ng-N m−3 and on average contributed ∼10% to WSTN mass, with the majority of soluble nitrogen being ammonium (∼82%). WSON:WSOC (or N:C) mass ratios ranged between 0 and 27% at both the sites with a median value of ∼5%, similar to what has been reported in another study in the southeastern USA. At both the urban and rural sites median nighttime levels of WSON and N:C were observed to be consistently higher than daytime values. Based on correlation analyses, daytime WSON sources appeared different than nighttime sources, especially at the urban site. Overall, the data suggest the importance of coal-combustion (e.g., link to SO2), vehicle emissions, soil dust and biomass burning as WSON sources, and that nitrogenous organic compounds are likely a fairly small fraction of the secondary organic aerosol for this location during summer.

Dry and wet deposition of water-insoluble dust and water-soluble chemical species during spring 2007 in Tsukuba, Japan

Dry and wet depositions were sampled daily in Tsukuba, Japan, in spring 2007. Temporal variations in the dry and wet deposition fluxes of dust and water-soluble chemical species were controlled largely by air mass origin, the water vapor mixing ratio, and Asian dust events. The contribution of local sources to dry deposition of dust was large when the wind speed was high. Dry deposition fluxes of water-soluble chemical species were larger in humid air masses than in dry air masses. Wet deposition fluxes of dust and water-soluble chemical species indicated that air masses that passed over dust source regions and industrial regions became mixed with the maritime air masses over the coastal site of the Asian continent and western part of the Japanese islands. The total deposition of dust was 4220 mg m −2 month −1, and that of water-soluble chemical species ranged from 10 to 636 mg m −2 month −1. Wet deposition fluxes of the total deposition flux of dust accounted for 72% and those of water-soluble chemical species was for 72–96%. In particular, the largest wet deposition occurred during a single Asian dust event on 3 April. This event accounted for 23% (950 mg m −2 month −1) of the monthly dust deposition flux and for 2–28% (0.43–51 mg m −2 month −1) of the monthly deposition flux of water-soluble chemical species. This result implies that the wet deposition flux associated with even one sporadic Asian dust event can have extensive impacts on both terrestrial and oceanic ecosystems in East Asia.

Production of Eisenia fetida and vermicompost from feed-lot cattle manure

Significant reductions in total mass of feedlot cattle manure were obtained by the intensive activity of earthworms. The process yielded two products: residual vermicompost, and an increase in earthworm biomass. Various modes of manure application were made to a prepared bedding (or support material), the most successful being a surface (vertical) application which resulted in a reduction of 30% of the initial manure (dry) mass and the production of live earthworms to 4.9% of the initial manure mass (dry weight). The increase in earthworm biomass represented extraction of, respectively 7, 18, 7 and 2% of initial total C, N, S and P from the manure. The production of vermicompost from manure resulted in a pH shift toward neutral, a reduction in electrical conductivity, large increases in oxidation potential, and significant reductions in water-soluble chemical species which constitute possible environmental contaminants.