Heterogeneous iodine-organic chemistry fast-tracks marine new particle formation

The gas-phase formation of new particles less than 1 nm in size and their subsequent growth significantly alters the availability of cloud condensation nuclei (CCN, >30–50 nm), leading to impacts on cloud reflectance and the global radiative budget. However, this growth cannot be accounted for by condensation of typical species driving the initial nucleation. Here, we present evidence that nucleated iodine oxide clusters provide unique sites for the accelerated growth of organic vapors to overcome the coagulation sink. Heterogeneous reactions form low-volatility organic acids and alkylaminium salts in the particle phase, while further oligomerization of small α-dicarbonyls (e.g., glyoxal) drives the particle growth. This identified heterogeneous mechanism explains the occurrence of particle production events at organic vapor concentrations almost an order of magnitude lower than those required for growth via condensation alone. A notable fraction of iodine associated with these growing particles is recycled back into the gas phase, suggesting an effective transport mechanism for iodine to remote regions, acting as a “catalyst” for nucleation and subsequent new particle production in marine air.

Marine aerosol formation contributes significantly to the global radiative budget given the high susceptibility of marine stratiform cloud radiative properties to changes in cloud condensation nuclei (CCN) availability. Atmospheric new-particle-formation is thought to involve nucleation of sulfuric acid with water, ammonia, or amines followed by condensation/growth in the presence of organic vapors (1, 2). Unique in the marine boundary layer (MBL), new particle formation involves sequential addition of HIO₃ or clustering of iodine oxides (I_xO_y) (3, 4). In specific source regions such as coastal zones, seaweed beds, or snowpack/pack-ice, iodine oxide nucleation can be a driving force for nucleation (5–7). Over Arctic waters, nonetheless, one study finds insufficient iodic acid vapors to grow nucleated particles to CCN sizes (8), whereas another study finds that both nucleation and growth are almost exclusively driven by iodic acid (9). Over the open ocean, the supply of iodine oxides has been thought to be limited; however, recent measurements suggest that significant reactive iodine chemistry can occur in these regions (10). Moreover, observational evidence exists for open ocean particle formation and growth, especially when oceanic productivity is high (11, 12). An increase in atmospheric iodine levels in the North Atlantic since the mid-20th century has been shown to be driven by growth of anthropogenic ozone and enhanced subice phytoplankton production (13). While the reported IO concentration (0.4–3.1 ppt) in the remote MBL (10, 14, 15) is likely sufficient for formation of prenucleation clusters (∼1 nm), growth of these initial clusters requires the presence of other condensable vapors (16). Since preexisting aerosol particles act as a strong sink for the nucleated clusters, thus inhibiting atmospheric aerosol and CCN formation (17, 18), this early growth phase is essential for their survival. Whereas sulfuric acid vapor is also involved in nucleation, its level in remote open ocean is generally too low (10⁵ molecules cm⁻³) to support subsequent particle growth, leaving organic vapors as the most plausible alternative for particle growth.In the marine atmosphere, condensing organics must originate from the oxidation of marine volatile organic compounds (VOCs), which predominantly comprise C₁–C₅ VOCs (e.g., isoprene) released from phytoplankton. Principal high volatility oxidation products consist of intermediate oxidized organics (IOOs), such as polyhydric alcohols (e.g., tetrols) or polyfunctional carbonyls (e.g., glyoxal) (19–22). Nonetheless, growth of available prenucleation clusters/nanometer particles requires condensing organic molecules of low effective volatilities (i.e., saturation mass concentration, C* < ∼10⁻³ μg m⁻³); otherwise, preferential condensation of the organic mass to larger-diameter particles would occur (23, 24). Formation of such extremely low-volatility organic compounds (ELVOCs) from gas-phase reaction is well established for monoterpene oxidation products (25, 26).A potential pathway for formation of low-volatility organics could also result from particle-phase chemical reactions induced by iodine oxides in the early stages of marine particle formation. When the underlying chemistry is sufficiently fast, kinetic condensation occurs, resulting in particles with diameters smaller than about 50 nm growing at the same rate (e.g., nm h⁻¹) (24). If, however, particle-phase chemistry is preferentially favored in the smallest particles (i.e., stemming from the higher relative concentration of iodine oxides in freshly formed marine particles), growth of the nucleated particles could proceed more rapidly, as compared to that in which gas-phase chemistry is the source of the low-volatility compounds (23).In this paper, we present experimental results from field measurements as well as laboratory studies of nanometer particle growth and derive a plausible chemical mechanism from the results that can explain the observations of ultrafine particle growth in the marine atmosphere. The results suggest that both iodine and condensed organics contribute to particle growth from a nascent nucleation mode into an ultrafine particle mode. Moreover, laboratory studies of the growth of seed iodine oxide particles (IOP) via heterogeneous reactions with organic vapors suggest a hitherto unrecognized mechanism that fast-tracks the growth of nucleation mode clusters into survivable aerosol particles. In this process, a notable fraction of the iodine associated with these growing particles is recycled back to the gas phase, suggesting a transport mechanism for iodine to remote regions.     

Uptake of sidestream smoke by Syrian golden hamsters

An inhalation bioassay with Syrian golden hamsters is being conducted to evaluate the toxic and carcinogenic potential of cigarette sidestream smoke (SS) relative to mainstream smoke (MS). A Hamburg II smoking machine is used to deliver MS by nose-only exposure to hamsters and a modification allows for the simultaneous collection of SS for whole-body delivery to a different rack of animals. The tolerated dose of SS was determined by varying the air/smoke dilutions drawn through the animal restrainers. Preliminary data indicated that 20% carboxyhemoglobin (COHb) could be obtained in SS-exposed animals without fatality. Optimum exposure levels were determined. Monthly measurements of COHb, nicotine and cotinine indicate that the SS-exposed animals are absorbing slightly higher amounts of these smoke constituents than the MS-exposed hamsters. Tumor incidence and carcinogenicity data are being collected through complete necropsy and histology protocols and uptake data continue to be collected. These studies should help elucidate the carcinogenic potential of SS which has been suggested from its composition and from recent epidemiological data of cancer incidence in non-smokers.     

Beitrag zur carcinogenen Wirkung von Dibenzopyrenen

Zusammenfassung Nach Synthese und/order sorgfältiger Reinigung wurden neun hexacyclische Verbindungen im Pinselungstest im Vergleich zu Benzo(a)-pyren an der Maus auf ihre krebserzeugende und Tumor-Initiatowirkung geprüft. Es ergaben sich folgende Reihen der Aktivitäten: Als Vollcarcinogen sind Benzo(a) pyren (X) stark aktiv; dibenzo(a, h)pyren (IV), Dibenzo(a, l)pyren(I), und Dibenzo(a, i)pyren (V) aktiv; Dibenzo(a, e)pyren (II) und Indeno(1,2,3-cd)pyren (IX) schwach aktiv und Dibenzo(a, l)pyren (III), Dibenzo (cd-jk)pyren (VI), Benzo(ghi)perylen (VII) und Naphtho(2,3-e)pyren (VIII) inaktiv. Im Tumor-Initiatortest, in dem 2,5% Grotonöl als Promotor verwendet wurde, waren stark aktiv die Kohlenwasserstoffe X und IV; aktiv I und V; schwach aktiv II, VIII und IX; inaktiv die Verbindungen III, VI und VII. Die Ergebnisse der biologischen Versuche werden mit Berechnungen und Testen der Aktivitäten dieser polycyclischen Kohlenwasserstoffe verglichen. Da viele dieser Verbindungen in der Umwelt des Menschen vorkommen, sind die Beobachtungen von akademischer wie auch praktischer Bedeutung.

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Summary Nine synthesized and/or highly purified hexacyclic aromatic hydrocarbons were tested for carcinogenicity and tumor-initiating potency on mouse skin. Their activities were compared with those of benzo(a)pyrene. The following order of activities was found: As complete carcinogen benzo(a)pyrene (X) rates strongly active; dibenzo(e, h)pyren (IV), dibenzo(a, l)pyrene (I) and dibenzo(a, i)pyrene (V) were active; dibenzo(a, e)pyrene (II) and indeno(1,2,3-cd)pyrene (IX) were weakly active and dibenzo(e, l)pyrene (III), dibenzo(cd-jk)pyrene (VI); benzo(ghi)perylene (VII) and naphtho(2,3-e)pyrene (VIII) were inactive. The initiator test for the polycyclic hydrocarbons made use of 2,5% Croton oil as promoter. The initiating activity was found to be strongly active for the polycyclic hydrocarbons X and IX; active for I and V, weakly active for II, VIII and IX and inactive for III, VI and VII. The results of the mouse skin tests are compared with data resulting from theoretical considerations and with predictions of carcinogenicity on the basis of physico-chemical reactions for these polynuclear aromatic hydrocarbons. Since many of these compounds occur in man's environment, these investigations are not only of academic but also of practical importance.

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Herrn Professor Dr. K. H. Bauer zum 75. Geburtstag gewidmet.     

Metastasen und sonstige Fernwirkungen

Ohne Zusammenfassung     

Über Einen Hypophysären Regulations-Mechanismus im Kohlehydratstoff-Wechsel und Seine Störung Beim Diabetes Mellitus

Zusammenfassung Nach Kohlehydratbelastung erscheint im Blute gesunder Versuchspersonen eine Substanz, welche das Leberglykogen der Ratte im Verlauf mehrerer Stunden erheblich herabsetzt. Diese Substanz findet sich weder im Nüchternblut noch im Blut nach Fett- oder Eiweißbelastung. Die leberglykogenvermindernde Substanz des Blutes ist hypophysären Ursprungs. Denn auch im HVL. findet sich eine spezifische Substanz, welche die gleiche Wirkung auf das Leberglykogen der Ratte besitzt, und welche sich in ihren physikalischen und chemischen Eigenschaften, soweit sich feststellen läßt, von der wirksamen Substanz des Blutes nicht unterscheidet. Aus dieser Übereinstimmung wird auf die Identität beider Substanzen geschlossen; diese Annahme wird weiterhin durch Versuche am hypophysenlosen Hund erhärtet, bei dem — im Gegensatz zum Normaltier — die Ausschüttung nach Zuckerbelastung nicht mehr erfolgt. Aus der regulatorischen Ausschüttung des wirksamen Prinzips nach Kohlehydratzufuhr wird geschlossen, daß es sich um einen hypophysären Regulationsmechanismus im Kohlehydratstoffwechsel handelt, der ähnlich gelagert ist wie der von uns früher gefundene hypophysäre Regulationsmechanismus im Fettstoffwechsel. Das wirksame Prinzip wird als das Kohlehydratstoffwechselhormon des HVL. bezeichnet, da es ein neues Vorderlappenhormon darstellt; denn es wurde in darauf gerichteten Untersuchungen festgestellt, daß es mit keinem der bekannten HVL.-Hormone als identisch betrachtet werden kann.Schließlich werden im Hinblick auf die Übereinstimmung gewisser Symptome 8 Diabeteskranke auf das Vorkommen des Kohlehydratstoffwechselhormons und auch des Fettstoffwechselhormons untersucht, und es wird das krankhafte Vorkommen beider hypophysärer Wirkstoffe in hoher Konzentration im Nüchternblut des Diabetikers festgestellt. Damit erscheint der Nachweis einer tiefgreifenden Störung hypophysärer Regulationsmechanismen beim Diabetes mellitus erbracht.Mit Unterstützung durch die Notgemeinschaft der Deutschen Wissenschaft und den Medizinischen Hilfsfonds der Akademie.     

Über Gewinnung einer Direkten Virulenten Reinkultur der Spirochaeta Pallida aus Kaninchensyphilom in Flüssigem Nährboden

Ohne Zusammenfassung