Relações patofisiológicas entre estresse oxidativo e arteriosclerose

Oxidative stress is the result of an imbalance between oxidant and antioxidant species, with predominance of oxidative species with harmful action of reactive oxygen species (ROS) and reactive nitrogen species (RNS) on cells. Changes in the levels of nitric oxide (NO•) can be the cause and/ or a result of various pathophysiological processes. The main objective of this review is to address the relationship between oxidative stress and atherosclerosis in order to better understand the main features of this disease.

Da escassez ao estresse do planeta: um século de mudanças no ciclo do nitrogênio

Heavy metals and pesticides are usually associated with the main problems humankind has created in the natural environment. However, compounds with characteristics of essential macronutrients are causing serious environmental changes that could intensify, compromising the diversity of life on the planet. This is the case of nitrogen compounds, produced by industrial processes for use in intensive agriculture in addition to those unwittingly produced from human activities, available in excess in the environment. These compounds warrant greater attention from researchers in various fields of knowledge and public agencies for environmental control, toward minimizing their availability in the environment, thereby returning conditions closer to the natural environmental balance of the planet.

Jätteenpolton typenoksidipäästöjen vähentäminen

Työn tavoitteena oli selvittää jätteenpolton typenoksidipäästöjen puhdistusmahdollisuuksia. Työssä käydään läpi typen oksidien muodostuminen poltossa ja typen oksidien poistomenetelmät. Poistomenetelmiä käsiteltäessä painotus on arinapoltossa ja erityisesti selektiivisessä ei-katalyyttimenetelmässä (SNCR). Työn kokeellinen osa tehtiin Ekokem Oy Ab:n jätevoimalassa Riihimäellä. Kokeellisessa osassa selvitettiin ensin ammoniakkiveden massavirran, SNCR-laitteiston veden massavirran ja räjähdysnuohouksen vaikutusta typenoksidipitoisuuteen. Samalla selvitettiin muita typenoksidipitoisuuteen vaikuttavia tekijöitä sekä SNCR-laitteiston puhdistustehokkuus. Sen jälkeen selvitettiin parhaita toiminta-arvoja öljyisen veden massavirralle, SNCR-laitteiston massavirralle ja primääri- ja sekundääri-ilman suhteelle typenoksidipitoisuuden, ammoniakki-slip:n, ilokaasupitoisuuden, ammoniakkiveden kulutuksen ja höyryn tuotannon kannalta. Tulokseksi saatiin, että ammoniakkiveden massavirran lisääminen pienentää typenoksidipitoisuutta, mutta voi aiheuttaa ammoniakkipäästön. Paras SNCR-laitteiston veden massavirta on suurin tutkittu, 800 kg/h, jolloin typenoksidipitoisuus sekä typenoksidipitoisuuden hetkittäinen vaihtelu, ammoniakkiveden kulutus ja ammoniakkipäästö ovat pienimmät. Samalla tosin höyryn virtaama pienenee. SNCR-laitteiston puhdistustehokkuudeksi saatiin 60 %. Räjähdysnuohouksella ei ole havaittavaa, eikä öljyisen veden massavirralla merkittävää vaikutusta typenoksidipitoisuuteen. Ammoniakkiveden kulutuksen kannalta paras öljyisen veden määrä on 600 kg/h, kun taas ammoniakki-slip:n kannalta paras öljyisen veden määrä on 950 kg/h. Primääri-ilman osuuden pienentäminen pienentää ammoniakki-slip:iä ja ammoniakkiveden kulutusta.

Kuivajätehuollon hiilijalanjälki ja kustannukset sekä kuljetusten kilpailutus – Etelä-Karjalan aluekeräyspisteverkoston päivitys

Tutkimuksen tavoitteena oli yhtenäistää Etelä-Karjalan alueen erilaisia tapoja toimia alueke-räyksen suhteen. Aluekeräyksellä tarkoitetaan jätteiden keräystä pisteiltä, joihin kotitaloudet, jotka eivät kuulu kiinteistökohtaiseen keräykseen, voivat tuoda syntypaikkalajitellun kuiva- eli sekajätteensä. Tavoitteena oli myös saada tietoa siitä, minkälaiset ovat eri kuivajätehuoltovaihtoehtojen ilmastonmuutos- ja kustannusvaikutukset. Lisäksi tavoitteena oli selvittää, miten ympäristönäkökohdat voidaan ottaa huomioon kuljetuskilpailutuksissa. Tutkimuksessa kerättiin tietoa internetistä, opinnäytetöistä ja tieteellisistä artikkeleista sekä yritysten edustajilta. Kasvihuonekaasupäästöjen laskennassa hyödynnettiin GaBi 6.0 -elinkaariarviointiohjelmaa. Tutkimuksen perusteella aluekeräyspisteet kannattaa sijoittaa reiteille, joita asukkaat käyttävät vähintään kerran viikossa ja mitkä ovat optimaalisesti myös kuljetusurakoitsijan kannalta. Taajama-alueelle ei nähty suositeltavaksi sijoittaa aluekeräyspisteitä. Suositeltavina astioina aluekeräyspisteille nähtiin syväkeräyssäiliöt, joiden tyhjennys onnistuu samalla keräyskalustolla kuin kiinteistöjen jäteastioiden, kun ajoneuvo on varustettu puominosturilla. Suositeltavaksi nähtiin myös harventaa jäteastioiden talvityhjennystiheyksiä, jos tyhjennystiheys on vakio ympäri vuoden, sillä pääosa aluekeräyspisteiden käyttäjistä on loma-asukkaita. Tyhjennystiheyksien harvennuksella olisi mahdollista saavuttaa kustannussäästöjä. Tutkimuksessa laskettiin kuivajätteen elinkaarenaikaisia kasvihuonekaasupäästöjä kuivajätteen keräyksestä loppusijoitukseen ja energiahyötykäyttöön. Energiahyötykäyttökohteiksi valittiin Riihimäen, Kotkan sekä Leppävirran (suunnitteilla) jätteenpolttolaitokset. Tulosten pohjalta kuivajätteen energiahyötykäyttö oli loppusijoitusta selkeästi parempi vaihtoehto. Kuivajätteen keräys- ja kuljetuspäästöjen vaikutus oli pieni. Kuivajätteen kuljetusmatkan pituus jätteenpolttolaitokselle ei ole siis ratkaisevassa roolissa kokonaiskasvihuonekaasupäästöjä tarkasteltaessa. Etäisyyttä suurempi vaikutus onkin kuivajätteen koostumuksella, polttolaitosten vuosihyötysuhteilla ja korvattavilla polttoaineilla. Jatkossa suositellaan selvittämään vielä vaihtoehtoisia käsittelytapoja kuivajätteen sisältämälle sekamuovijakeelle, jonka poltosta aiheutuu merkittävä osuus (noin 74 %) kuivajätteen polton kasvihuonekaasupäästöistä. Ajankohtaisia kuljetuskilpailutuksia varten tarkasteltiin vielä tarkemmin keräys- ja kuljetuspäästöjä. Tulosten pohjalta havaittiin, että keräys- ja kuljetuspäästöjä on mahdollista vähentää reilusti (46–74 %) siirtymällä dieselistä biopolttoaineiden käyttöön. Tuloksiin vaikuttaa kuitenkin merkittävästi, minkälaisista raaka-aineista biopolttoaineet on valmistettu. Kuivajätteen keräyspäästöjä on mahdollista pienentää myös päivittämällä aluekeräyspisteverkostoa. Tutkimuksessa tarkasteltiin kustannuksia aluekeräyspisteiden astioiden uusinnasta tai korjauksesta kuivajätteen loppusijoitukseen tai energiahyötykäyttöön asti. Merkittävimmät kustannukset aiheutuivat kuivajätteen loppusijoituksesta, energiahyötykäytöstä sekä keräyksestä. Kustannusten näkökulmasta keräyksen rooli oli siis suurempi. Työn lopussa annettiin vielä vinkkejä, joiden avulla jätehuoltoyritykset voivat tehdä jätekuljetushankintoja ympäristönäkökohdat huomioiden. Usein selkein tapa huomioida ympäristönäkökohdat kuljetuskilpailutuksissa on asettaa riittävän tiukkoja pakollisia vaatimuksia, jolloin voi valita hinnaltaan halvimman vaihtoehdon. Kuljetuspalvelun hankinnassa tulee huomioida ainakin energiankulutus, hiilidioksidi-, typenoksidi-, hiilivety- ja hiukkaspäästöt. Lainsäädäntö ei määrää vähimmäistasoja, vaan hankintaa tehdessä kannattaa kartoittaa markkinatilanne, jotta vaatimukset osaa asettaa oikealle tasolle. Markkinoille kannattaa myös tiedottaa tulevaisuuden tarpeista ja suunnitelmista. Suuria hankintakokonaisuuksia suositellaan pilkottavan pienempiin osiin, jotta pienet ja keskisuuret yritykset pystyvät myös osallistumaan tarjouskilpailuihin. Kannustus innovaatioiden huomioimiseen hankinnoissa on lisääntynyt myös jätehuollon alalla. Selvitettyjen kasvihuonekaasupäästöjen perusteella oli merkille pantavaa, miten suuri vaikutus polttolaitoksen valinnalla oli kasvihuonekaasupäästöihin. Oleellista onkin huomioida ympäristönäkökohdat myös energiahyötykäyttökohdetta valittaessa.

The effect of environmentally differentiated port fees to shipping companies’ environmental investments

The pressure has grown to develop cost-effective emission reduction strategies in the Baltic Sea. The forthcoming stringent regulations of the International Maritime Organization for reducing harmful emissions of shipping in the Baltic Sea are causing increasing expenses for the operators. A market-based attitude towards pricing of economic incentives could be seen as a new approach for a successful application for the additional emission reduction of nitrogen oxides (NOx). In this study the aim is to understand the phenomenon of environmentally differentiated port fees and its effects on shipping companies’ emission reduction investments. The goal is to examine empirically the real-life effects of the possible environmental differentiated port fee system and the effect of environmentally differentiated port fees on NOx reduction investments in the Baltic Sea. The research approach of this study is nomothetical. In this study research questions are answered by analyzing the broad database of the Baltic Sea fleet. Also the framework of theory is confirmed and plays an important role in analyzing the research problem. Existing investment costs of NOx emission reduction technology to ship owners are estimated and compared to investment costs with granted discounts added to the cash flows. The statistical analysis in this study is descriptive. The major statistic examination of this study is the calculation of the net present values of investments with different port fee scenarios. This is done to investigate if the NOx technology investments could be economically reasonable. Based on calculations it is clear that the effect of environmentally differentiated port fees is not adequate to compensate the total investment costs for NOx reduction. If the investment decision is made only with profitability considerations, sources will prefer to emission abatement as long as incomes from the given subsidy exceeds their abatement costs. Despite of the results, evidence was found that shipping companies are nevertheless willing to invest on voluntary emission abatement technology. In that case, investment decision could be made with criteria of, for example, sustainable strategy or brand image. Combined fairway and port fee system or governmental regulations and recommendation could also function as additional incentives to compensate the investment costs. Also, the results imply that the use of NPV is not necessarily the best method to evaluate environmental investments. If the calculations would be done with more environmental methods the results would probably be different.

Maakaasupolttimen säätöjärjestelmän kehittäminen

Jatkuvasti kiristyvät päästörajoitukset pakottavat teollisuuden kehittämään uusia ratkaisuja päästöjen vähentämiseksi. Hiilimonoksidin ja typen oksidien päästörajoitukset ovat erityi-sen tiukat esimerkiksi Kiinassa ja Yhdysvalloissa. Maakaasun ja ilman epätäydellisessä pa-lamisessa muodostuu hiilimonoksidia ja typen oksideja. Käytännön sovelluksissa palaminen on lähes aina epätäydellistä polttoaineen ja ilman epätäydellisen sekoittumisen takia, joten palamisreaktiossa muodostuva savukaasu sisältää edellä mainittuja haitallisia komponentteja lähes poikkeuksetta. Savukaasua voidaan puhdistaa erilaisilla menetelmillä ennen sen pää-tymistä ympäristöön. Tässä diplomityössä esitellään maakaasupoltinjärjestelmän keskeiset komponentit ja aihee-seen liittyvät tarpeelliset käsitteet sekä suunnitellaan polttoaine-ilma-seossuhdesäätö eräälle maakaasupoltinjärjestelmälle. Säädön ensisijaisena tavoitteena on pitää seossuhde mahdolli-simman tarkasti halutussa arvossa savukaasun puhdistuksen kannalta. Lisäksi säädön on tarkoitus taata mahdollisimman hyvä suorituskyky transienttitilanteissa. Järjestelmän eri osien toiminta mallinnetaan ja analysoidaan. Mallinnuksen perusteella suunnitellaan ja simu-loidaan säätöjärjestelmä. Suunniteltu säätöjärjestelmä toteutetaan osaksi polttolaitoksen automaatiojärjestelmää. Mittaustulokset osoittavat, että päästöjen kannalta säätö pitää seossuhteen riittävän tarkasti halutussa arvossa: hiilimonoksidin ja typen oksidien päästöt ovat asetettujen rajojen sisällä. Testiajojen perusteella prosessi on kuitenkin erittäin häiriöinen ja transienttitilanteissa ei saavuteta simulointien mukaista suorituskykyä.

Association between NOx exposure and deaths caused by respiratory diseases in a medium-sized Brazilian city

Exposure to nitrogen oxides (NOx) emitted by burning fossil fuels has been associated with respiratory diseases. We aimed to estimate the effects of NOx exposure on mortality owing to respiratory diseases in residents of Taubaté, São Paulo, Brazil, of all ages and both sexes. This time-series ecological study from August 1, 2011 to July 31, 2012 used information on deaths caused by respiratory diseases obtained from the Health Department of Taubaté. Estimated daily levels of pollutants (NOx, particulate matter, ozone, carbon monoxide) were obtained from the Centro de Previsão de Tempo e Estudos Climáticos Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System. These environmental variables were used to adjust the multipollutant model for apparent temperature. To estimate association between hospitalizations owing to asthma and air pollutants, generalized additive Poisson regression models were developed, with lags as much as 5 days. There were 385 deaths with a daily mean (±SD) of 1.05±1.03 (range: 0-5). Exposure to NOx was significantly associated with mortality owing to respiratory diseases: relative risk (RR)=1.035 (95% confidence interval [CI]: 1.008-1.063) for lag 2, RR=1.064 (95%CI: 1.017-1.112) lag 3, RR=1.055 (95%CI: 1.025-1.085) lag 4, and RR=1.042 (95%CI: 1.010-1.076) lag 5. A 3 µg/m3 reduction in NOx concentration resulted in a decrease of 10-18 percentage points in risk of death caused by respiratory diseases. Even at NOx concentrations below the acceptable standard, there is association with deaths caused by respiratory diseases.

Modification des propriétés optiques de nanofils à base de GaN par plasma N2/O2

Une sonde électrostatique de Langmuir cylindrique a été utilisée pour caractériser une post-décharge d’un plasma d’ondes de surface de N2-O2 par la mesure de la densité des ions et électrons ainsi que la température des électrons dérivée de la fonction de distribution en énergie des électrons (EEDF). Une densité maximale des électrons au centre de la early afterglow de l’ordre de 1013 m-3 a été déterminée, alors que celle-ci a chuté à 1011 m-3 au début de la late afterglow. Tout au long du profil de la post-décharge, une densité des ions supérieure à celle des électrons indique la présence d’un milieu non macroscopiquement neutre. La post-décharge est caractérisée par une EEDF quasi maxwellienne avec une température des électrons de 0.5±0.1 eV, alors qu’elle grimpe à 1.1 ±0.2 eV dans la early afterglow due à la contribution des collisions vibrationnelles-électroniques (V-E) particulièrement importantes. L’ajout d’O2 dans la décharge principale entraîne un rehaussement des espèces chargées et de la température des électrons suivi d’une chute avec l’augmentation de la concentration d’O2. Le changement de la composition électrique de la post-décharge par la création de NO+ au détriment des ions N2+ est à l’origine du phénomène. Le recours à cette post-décharge de N2 pour la modification des propriétés d’émission optique de nanofils purs de GaN et avec des inclusions d’InGaN a été étudié par photoluminescence (PL). Bien que l’émission provenant des nanofils de GaN et de la matrice de GaN recouvrant les inclusions diminue suite à la création de sites de recombinaison non radiatifs, celle provenant des inclusions d’InGaN augmente fortement. Des mesures de PL par excitation indiquent que cet effet n’est pas attribuable à un changement de l’absorption de la surface de GaN. Ceci suggère un recuit dynamique induit par la désexcitation des métastables de N2 suite à leur collision à la surface des nanofils et la possibilité de passiver les défauts de surface tels que des lacunes d’azote par l’action d’atomes de N2 réactifs provenant de la post-décharge. L’incorporation d’O2 induit les mêmes effets en plus d’un décalage vers le rouge de la bande d’émission des inclusions, suggérant l’action des espèces d’O2 au sein même des nanostructures.

Perfil epidemiológico de la prevalencia de hipoacusia en un grupo de empleados que trabaja en el ambiente urbano, 2015

El propósito de este estudio es determinar la relación entre la exposición ocupacional y los niveles de audición en trabajadores urbanos en espacio abierto (aseo urbano en general). Se realizó un estudio de corte transversal con 491 personas que incluyen hombres y mujeres, cuyo ambiente laboral es el espacio abierto de la ciudad. Los datos se obtuvieron durante los exámenes médicos periódicos realizados en el año 2014 a los empleados de una empresa cuya actividad económica es el aseo urbano, que incluye recolección de basuras, cuidado forestal y de prados de uso común, y limpieza del borde de los andenes. Se realizó estadística descriptiva para las características demográficas y razón de disparidad u Odds Ratio (OR) para buscar la relación de antecedentes y hábitos personales con el riesgo de desarrollar pérdida auditiva. De las 491 personas expuestas a niveles altos de ruido ocupacional, 62% presentó pérdida auditiva, de los cuales la mayoría se desempeña como guadañadores y cortadores de césped, y son personas que llevan trabajando entre 1-5 años en la empresa. Se encontró un aumento estadísticamente significativo entre la baja escolaridad y el riesgo de sufrir hipoacusia (p=0.0001) y un efecto protector del uso de motocicleta y audífonos. La enfermedad vascular periférica, la práctica de tejo y la diabetes mostraron una fuerte tendencia a aumentar el riesgo. La pérdida auditiva encontrada en este grupo no se puede relacionar directamente con la exposición ocupacional a ruido, a pesar de ser trabajos que se llevan a cabo en el espacio urbano. Sin embargo, la baja escolaridad favorece la lesión auditiva y puede verse acelerada por enfermedades de alta prevalencia como diabetes y practicas recreacionales locales.

Shifts in rhizosphere microbial communities and enzyme activity of Poa alpina across an alpine chronosequence

This study quantifies the influence of Poa alpina on the soil microbial community in primary succession of alpine ecosystems, and whether these effects are controlled by the successional stage. Four successional sites representative of four stages of grassland development (initial, 4 years (non-vegetated); pioneer, 20 years; transition, 75 years; mature, 9500 years old) on the Rotmoos glacier foreland, Austria, were sampled. The size, composition and activity of the microbial community in the rhizosphere and bulk soil were characterized using the chloroform-fumigation extraction procedure, phospholipid fatty acid (PLFA) analysis and measurements of the enzymes beta-glucosidase, beta-xylosidase, N-acetyl-beta-glucosaminidase, leucine aminopeptidase, acid phosphatase and sulfatase. The interplay between the host plant and the successional stage was quantified using principal component (PCA) and multidimensional scaling analyses. Correlation analyses were applied to evaluate the relationship between soil factors (C-org, N-t, C/N ratio, pH, ammonium, phosphorus, potassium) and microbial properties in the bulk soil. In the pioneer stage microbial colonization of the rhizosphere of P. alpina was dependent on the reservoir of microbial species in the bulk soil. As a consequence, the rhizosphere and bulk soil were similar in microbial biomass (ninhydrin-reactive nitrogen (NHR-N)), community composition (PLFA), and enzyme activity. In the transition and mature grassland stage, more benign soil conditions stimulated microbial growth (NHR-N, total amount of PLFA, bacterial PLFA, Gram-positive bacteria, Gram-negative bacteria), and microbial diversity (Shannon index H) in the rhizosphere either directly or indirectly through enhanced carbon allocation. In the same period, the rhizosphere microflora shifted from a G(-) to a more G(+), and from a fungal to a more bacteria-dominated community. Rhizosphere beta-xylosidase, N-acetyl-beta-glucosaminidase, and sulfatase activity peaked in the mature grassland soil, whereas rhizosphere leucine aminopeptidase, beta-glucosidase, and phosphatase activity were highest in the transition stage, probably because of enhanced carbon and nutrient allocation into the rhizosphere due to better growth conditions. Soil organic matter appeared to be the most important driver of microbial colonization in the bulk soil. The decrease in soil pH and soil C/N ratio mediated the shifts in the soil microbial community composition (bacPLFA, bacPLFA/fungPLFA, G(-), G(+)/G(-)). The activities of beta-glucosidase, beta-xylosidase and phosphatase were related to soil ammonium and phosphorus, indicating that higher decomposition rates enhanced the nutrient availability in the bulk soil. We conclude that the major determinants of the microllora vary along the successional gradient: in the pioneer stage the rhizosphere microflora was primarily determined by the harsh soil environment; under more favourable environmental conditions, however, the host plant selected for a specific microbial community that was related to the dynamic interplay between soil properties and carbon supply. (C) 2004 Elsevier Ltd. All rights reserved.

Shifts in rhizosphere microbial communities and enzyme activity of Poa alpina across an alpine chronosequence

This study quantifies the influence of Poa alpina on the soil microbial community in primary succession of alpine ecosystems, and whether these effects are controlled by the successional stage. Four successional sites representative of four stages of grassland development (initial, 4 years (non-vegetated); pioneer, 20 years; transition, 75 years; mature, 9500 years old) on the Rotmoos glacier foreland, Austria, were sampled. The size, composition and activity of the microbial community in the rhizosphere and bulk soil were characterized using the chloroform-fumigation extraction procedure, phospholipid fatty acid (PLFA) analysis and measurements of the enzymes beta-glucosidase, beta-xylosidase, N-acetyl-beta-glucosaminidase, leucine aminopeptidase, acid phosphatase and sulfatase. The interplay between the host plant and the successional stage was quantified using principal component (PCA) and multidimensional scaling analyses. Correlation analyses were applied to evaluate the relationship between soil factors (C-org, N-t, C/N ratio, pH, ammonium, phosphorus, potassium) and microbial properties in the bulk soil. In the pioneer stage microbial colonization of the rhizosphere of P. alpina was dependent on the reservoir of microbial species in the bulk soil. As a consequence, the rhizosphere and bulk soil were similar in microbial biomass (ninhydrin-reactive nitrogen (NHR-N)), community composition (PLFA), and enzyme activity. In the transition and mature grassland stage, more benign soil conditions stimulated microbial growth (NHR-N, total amount of PLFA, bacterial PLFA, Gram-positive bacteria, Gram-negative bacteria), and microbial diversity (Shannon index H) in the rhizosphere either directly or indirectly through enhanced carbon allocation. In the same period, the rhizosphere microflora shifted from a G(-) to a more G(+), and from a fungal to a more bacteria-dominated community. Rhizosphere beta-xylosidase, N-acetyl-beta-glucosaminidase, and sulfatase activity peaked in the mature grassland soil, whereas rhizosphere leucine aminopeptidase, beta-glucosidase, and phosphatase activity were highest in the transition stage, probably because of enhanced carbon and nutrient allocation into the rhizosphere due to better growth conditions. Soil organic matter appeared to be the most important driver of microbial colonization in the bulk soil. The decrease in soil pH and soil C/N ratio mediated the shifts in the soil microbial community composition (bacPLFA, bacPLFA/fungPLFA, G(-), G(+)/G(-)). The activities of beta-glucosidase, beta-xylosidase and phosphatase were related to soil ammonium and phosphorus, indicating that higher decomposition rates enhanced the nutrient availability in the bulk soil. We conclude that the major determinants of the microllora vary along the successional gradient: in the pioneer stage the rhizosphere microflora was primarily determined by the harsh soil environment; under more favourable environmental conditions, however, the host plant selected for a specific microbial community that was related to the dynamic interplay between soil properties and carbon supply. (C) 2004 Elsevier Ltd. All rights reserved.

Tracer correlations in the northern high latitude lowermost stratosphere: Influence of cross‐tropopause mass exchange

We present an analysis of trace gas correlations in the lowermost stratosphere. In‐situ aircraft measurements of CO, N2O, NOy and O3, obtained during the STREAM 1997 winter campaign, have been used to investigate the role of cross‐tropopause mass exchange on tracer‐tracer relations. At altitudes several kilometers above the local tropopause, undisturbed stratospheric air was found with NOy/NOy * ratios close to unity, NOy/O3 about 0.003–0.006 and CO mixing ratios as low as 20 ppbv (NOy * is a proxy for total reactive nitrogen derived from NOy–N2O relations measured in the stratosphere). Mixing of tropospheric air into the lowermost stratosphere has been identified by enhanced ratios of NOy/NOy * and NOy/O3, and from scatter plots of CO versus O3. The enhanced NOy/O3 ratio in the lowermost stratospheric mixing zone points to a reduced efficiency of O3 formation from aircraft NOx emissions.

Cross-hemispheric transport of Central African biomass burning pollutants: Implications for downwind ozone production

Pollutant plumes with enhanced concentrations of trace gases and aerosols were observed over the southern coast of West Africa during August 2006 as part of the AMMA wet season field campaign. Plumes were observed both in the mid and upper troposphere. In this study we examined the origin of these pollutant plumes, and their potential to photochemically produce ozone (O3) downwind over the Atlantic Ocean. Their possible contribution to the Atlantic O3 maximum is also discussed. Runs using the BOLAM mesoscale model including biomass burning carbon monoxide (CO) tracers were used to confirm an origin from central African biomass burning fires. The plumes measured in the mid troposphere (MT) had significantly higher pollutant concentrations over West Africa compared to the upper tropospheric (UT) plume. The mesoscale model reproduces these differences and the two different pathways for the plumes at different altitudes: transport to the north-east of the fire region, moist convective uplift and transport to West Africa for the upper tropospheric plume versus north-west transport over the Gulf of Guinea for the mid-tropospheric plume. Lower concentrations in the upper troposphere are mainly due to enhanced mixing during upward transport. Model simulations suggest that MT and UT plumes are 16 and 14 days old respectively when measured over West Africa. The ratio of tracer concentrations at 600 hPa and 250 hPa was estimated for 14–15 August in the region of the observed plumes and compares well with the same ratio derived from observed carbon dioxide (CO2) enhancements in both plumes. It is estimated that, for the period 1–15 August, the ratio of Biomass Burning (BB) tracer concentration transported in the UT to the ones transported in the MT is 0.6 over West Africa and the equatorial South Atlantic. Runs using a photochemical trajectory model, CiTTyCAT, initialized with the observations, were used to estimate in-situ net photochemical O3 production rates in these plumes during transport downwind of West Africa. The mid-troposphere plume spreads over altitude between 1.5 and 6 km over the Atlantic Ocean. Even though the plume was old, it was still very photochemically active (mean net O3 production rates over 10 days of 2.6 ppbv/day and up to 7 ppbv/day during the first days) above 3 km especially during the first few days of transport westward. It is also shown that the impact of high aerosol loads in the MT plume on photolysis rates serves to delay the peak in modelled O3 concentrations. These results suggest that a significant fraction of enhanced O3 in mid-troposphere over the Atlantic comes from BB sources during the summer monsoon period. According to simulated occurrence of such transport, BB may be the main source for O3 enhancement in the equatorial south Atlantic MT, at least in August 2006. The upper tropospheric plume was also still photochemically active, although mean net O3 production rates were slower (1.3 ppbv/day). The results suggest that, whilst the transport of BB pollutants to the UT is variable (as shown by the mesoscale model simulations), pollution from biomass burning can make an important contribution to additional photochemical production of O3 in addition to other important sources such as nitrogen oxides (NOx) from lightning.

Sensitivity of 21st century stratospheric ozone to greenhouse gas scenarios

To understand how greenhouse gas (GHG) emissions may affect future stratospheric ozone, 21st century projections from four chemistry-climate models are examined for their dependence on six different GHG scenarios. Compared to higher GHG emissions, lower emissions result in smaller increases in tropical upwelling with resultant smaller reductions in ozone in the tropical lower stratosphere and less severe stratospheric cooling with resultant smaller increases in upper stratospheric ozone globally. Increases in reactive nitrogen and hydrogen that lead to additional chemical ozone destruction mainly play a role in scenarios with higher GHG emissions. Differences among the six GHG scenarios are found to be largest over northern midlatitudes (∼20 DU by 2100) and in the Arctic (∼40 DU by 2100) with divergence mainly in the second half of the 21st century. The uncertainty in the return of stratospheric column ozone to 1980 values arising from different GHG scenarios is comparable to or less than the uncertainty that arises from model differences in the larger set of 17 CCMVal-2 SRES A1B simulations. The results suggest that effects of GHG emissions on future stratospheric ozone should be considered in climate change mitigation policy and ozone projections should be assessed under more than a single GHG scenario.

Free radicals, metals and antioxidants in oxidative stress-induced cancer

Oxygen-free radicals, more generally known as reactive oxygen species (ROS) along with reactive nitrogen species (RNS) are well recognised for playing a dual role as both deleterious and beneficial species. The "two-faced" character of ROS is substantiated by growing body of evidence that ROS within cells act as secondary messengers in intracellular signalling cascades, which induce and maintain the oncogenic phenotype of cancer cells, however, ROS can also induce cellular senescence and apoptosis and can therefore function as anti-tumourigenic species. The cumulative production of ROS/RNS through either endogenous or exogenous insults is termed oxidative stress and is common for many types of cancer cell that are linked with altered redox regulation of cellular signalling pathways. Oxidative stress induces a cellular redox imbalance which has been found to be present in various cancer cells compared with normal cells; the redox imbalance thus may be related to oncogenic stimulation. DNA mutation is a critical step in carcinogenesis and elevated levels of oxidative DNA lesions (8-OH-G) have been noted in various tumours, strongly implicating such damage in the etiology of cancer. It appears that the DNA damage is predominantly linked with the initiation process. This review examines the evidence for involvement of the oxidative stress in the carcinogenesis process. Attention is focused on structural, chemical and biochemical aspects of free radicals, the endogenous and exogenous sources of their generation, the metal (iron, copper, chromium, cobalt, vanadium, cadmium, arsenic, nickel)-mediated formation of free radicals (e.g. Fenton chemistry), the DNA damage (both mitochondrial and nuclear), the damage to lipids and proteins by free radicals, the phenomenon of oxidative stress, cancer and the redox environment of a cell, the mechanisms of carcinogenesis and the role of signalling cascades by ROS; in particular. ROS activation of AP-1 (activator protein) and NF-kappa B (nuclear factor kappa B) signal transduction pathways, which, in turn lead to the transcription of genes involved in cell growth regulatory pathways. The role of enzymatic (superoxide dismutase (Cu. Zn-SOD. Mn-SOD), catalase, glutathione peroxidase) and non-enzymatic antioxidants (Vitamin C, Vitamin E, carotenoids, thiol antioxidants (glutathione, thioredoxin and lipoic acid), flavonoids, selenium and others) in the process of careinogenesis as well as the antioxidant interactions with various regulatory factors, including Ref-1, NF-kappa B, AP-1 are also reviewed. 2006 Elsevier Ireland Ltd. All rights reserved.