Ozone Uptake Rate Research Articles

Study on Transpiration Water Consumption and Photosynthetic Characteristics of Landscape Tree Species under Ozone Stress

Using Pinus bungeana, Platycladus orientalis, Koelreuteria paniculata and Ginkgo biloba as research objects, three open-top chambers with different ozone-concentration gradients were set up (NF, NF40 and NF80) based on trunk sap-flow technology to study the difference in ozone absorption by trees under different ozone concentrations. The results showed that the monthly and diurnal variations of sap-flow density of different tree species decreased with the increase in ozone concentration, and the increase in ozone concentration reduced the water consumption, ozone uptake rate (FO3), net photosynthetic rate (Pn) and water-use efficiency (WUE) of different tree species. The sap-flow density, water consumption, FO3 and WUE of Koelreuteria paniculata and Ginkgo biloba were higher than those of Pinus bungeana and Platycladus orientalis under different ozone concentrations. The sap-flow density, water consumption, FO3 and WUE of Koelreuteria paniculata and Ginkgo biloba decreased significantly at the ozone concentrations of NF40 and NF80; compared with the ozone concentration of NF, the sap flow density of Koelreuteria paniculata and Ginkgo biloba decreased by 1.04 and 1.03 times as much as that of Pinus bungeana and Platycladus orientalis, respectively; the water consumption of Koelreuteria paniculata and Ginkgo biloba decreased by 1.82 and 1.56 times that of Pinus bungeana and Platycladus orientalis, respectively; the decline rate of FO3 in Koelreuteria paniculata and Ginkgo biloba was 1.30 and 1.04 times that of Pinus bungeana and Platycladus orientalis, respectively; and the decline rate of WUE of Koelreuteria paniculata and Ginkgo biloba was 1.52 and 1.64 times that of Pinus bungeana and Platycladus orientalis, respectively. Pinus bungeana and Platycladus orientalis have stronger tolerance to ozone, while Koelreuteria paniculata and Ginkgo biloba were weak. A variety of conifers can be planted in areas with serious ozone pollution.

Response of Ginkgo biloba growth and physiological traits to ozone stress

Ginkgo biloba , the main greening tree species in Beijing, was used to study the effects of elevated ozone (O 3 ) concentrations on physiology and ecology using an open-top air chamber (OTC). We set three O 3 concentration gradients (NF: normal atmospheric O 3 concentration; NF40: normal atmospheric O 3 concentration plus 40 nmol/mol; NF80: normal atmospheric O 3 concentration plus 80 nmol/mol). Based on the theoretical basis of the coupling of O 3 and transpiration through stomata, the O 3 uptake from the leaf surface of G. biloba was studied under artificial control. The results showed that with the O 3 concentration increased, the leaves of G. biloba were damaged, stomatal density, stomatal aperture, stomatal size, net photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content decreased, while intercellular CO 2 concentrations and relative conductivity increased. The monthly and daily variations in the liquid flow density of G. biloba decreased with the increase in O 3 concentration. Similarly, water consumption and the ozone uptake rate ( F O3) of G. biloba decreased with the increase in O 3 concentration: Water consumption by the entire tree under the NF40 and NF80 ozone concentrations decreased compared to NF, the rates of decline were 68.77% and 78.38%, respectively. The rates of F O3 decrease were 15.48% and 31.04%, respectively.

Multiphase Kinetic Multilayer Model Interfaces for Simulating Surface and Bulk Chemistry for Environmental and Atmospheric Chemistry Teaching

This paper presents MATLAB user interfaces for two multiphase kinetic models: the kinetic double-layer model of aerosol surface chemistry and gas–particle interactions (K2-SURF) and the kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB). Each interface has simple and user-friendly features that allow undergraduate and graduate students in physical, environmental, and atmospheric chemistry classes to learn about multiphase chemistry modeling without prior computer programming or modeling experience. It is easy to input parameters, and the simulation results are promptly displayed in the interface; thus, these model interfaces are particularly suitable for in-classroom and homework teaching applications. The model input parameters include surface and bulk reaction rate coefficients, surface accommodation coefficient, and gas and bulk diffusivities, while model outputs include gas uptake coefficient and surface and bulk concentrations. Students can use the K2-SURF interface to simulate surface processes and the KM-SUB interface to simulate surface and bulk processes. Example simulations were performed for each interface to present atmospherically relevant applications and to demonstrate its versatility for exploring model sensitivity on various kinetic parameters. The K2-SURF interface was used to show how the rate of ozone uptake by an organic surface and temporal evolution of surface concentrations are affected by the surface accommodation coefficient, desorption lifetime, and surface reaction rate coefficient. Additionally, the KM-SUB interface was applied to demonstrate how bulk diffusivities impact the degradation kinetics of oleic acid particles, so that students can learn how the phase state (liquid vs semisolid vs glassy solid) impacts multiphase chemical kinetics. The developed K2-SURF and KM-SUB interfaces are effective tools for modeling surface and bulk reactions in college-level educational settings, helping students to obtain a deeper understanding of the complex behaviors of heterogeneous and multiphase systems.

Tertiary treatability of molasses secondary effluents for color and organics: performance and limits of ozonation and adsorption

Molasses wastewaters (MWWs) such as baker’s yeast and distilleries effluents are usually pretreated by anaerobic, followed by aerobic biodegradation. This removes almost all the BOD, enough for meeting the current discharge standards in many low- and middle-income countries. However, as shown in the present work, the biotreated effluent still contains high levels of recalcitrant COD, color (melanoidins) and inorganic salts that end up in rivers (approx. 1000 mg/L COD, 2850 Pt–Co color units, 5000 mg/L TDS and 5400 μS/cm conductivity). To address this global problematics, and given the lack of proven cost-effective advanced treatment trains for MWW, this study assessed the performance and limits of ozonation and activated carbon (AC) adsorption (contrasting with O3 applications on raw MWW). The applied versus the reacted O3 doses were quantified, allowing also to estimate the ozone uptake rate as a new tool for characterizing the reactivity of the wastewaters. The effects of the treatments on different key parameters were studied: COD, color, aromaticity (UV254 nm), toxicity (Microtox) and biodegradability (by respirometry). O3 reduced the color (> 95%), but causing low COD mineralization (< 35%) and biodegradability enhancement (only 8% more). Meanwhile, adsorption was efficient on both COD and color (97–91%), but needing high AC dosage. In consequence, a more sustainable treatment train was suggested, i.e., upgrading the activated sludge with aerobic granular sludge technology and transforming the granules into AC.

鼎湖山南亚热带天然针阔叶混交林臭氧吸收特征

PDF HTML阅读 XML下载 导出引用 引用提醒 鼎湖山南亚热带天然针阔叶混交林臭氧吸收特征 DOI: 10.5846/stxb201709201687 作者: 作者单位: 华南植物园,华南植物园 作者简介: 通讯作者: 中图分类号: 基金项目: 广东省自然科学基金（2014A030313746）；国家自然科学基金项目（31670453） Ozone uptake by the dominant canopy tree species in a natural mixed conifer-broadleaf forest in Dinghushan, Guangdong Province, south China Author: Affiliation: South China Botanical Garden,South China Botanical Garden Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:针阔叶混交林是我国南亚热带针叶林向地带性常绿阔叶林演替的中间林分类型，为我国南亚地区主要森林类型，发挥着重要的生态系统服务功能。基于树干液流技术和对臭氧浓度的连续监测，评价该森林类型的臭氧吸收特征和能力有着重要的环境生态学意义。对鼎湖山天然针阔叶混交林优势种马尾松（Pinus manssoniana）、锥栗（Castanopsis chinensis）、木荷（Schima superba）和华润楠（Machilus chinensis）在自然环境条件下的臭氧吸收能力进行了分析研究。结果表明：在日尺度上，4个优势树种的冠层气孔对臭氧导度（GO3）和臭氧吸收通量（FO3）均呈单峰型曲线，其最大值的时间在干季（10月至竖年3月）比湿季（4月至9月）滞后；季节尺度上，臭氧浓度在湿季达到最大值48.94 nL/L，湿季GO3、FO3和年臭氧吸收累积量（accumulative stomatal O3 flux，AFst）均显著高于干季（P < 0.01），华润楠的臭氧吸收能力最强，在干季和湿季可分别达1.11 nmol m-2 s-1和1.71 nmol m-2 s-1。随着水汽压亏缺（VPD）增大，优势种GO3降低。光合有效辐射（PAR）超过1500 umol m-2 s-1时，优势树种GO3和FO3呈下降趋势。针阔叶混交林的年臭氧吸收累积量超过了保护森林树木所采用的临界阈值，可认为鼎湖山针阔叶混交林受臭氧危害的潜在风险较高。 Abstract:We determined ozone (O3) uptake rates of the dominant tree species (Pinus manssoniana, Castanopsis chinensis, Schima superba, and Machilus chinensis) in a natural mixed conifer-broadleaf forest based on sap flow measurements and environmental monitoring. On a diurnal scale, the ozone uptake flux (FO3) by the dominant tree species had a unimodal pattern, and that the maximum flux appeared earlier in the wet season (April-September) than in the dry season (October-March). Compared to the wet season, the time of the maximum flux in the dry season was delayed. Seasonally, the maximum O3 concentration occurred in the wet season (48.94 nL/L). Canopy stomatal conductance for O3 (GO3), FO3, and annual accumulative stomatal O3 uptake (AFst) in the wet season were significantly higher than in the dry season (P < 0.01). Machilus chinensis had the highest O3 uptake capacity among the four species considered. The maximum FO3 was 1.11 nmol m-2 s-1 in the dry season and 1.71 nmol m-2 s-1 in the wet season. GO3 decreased with increasing vapour pressure deficit (VPD) in all the studied species. At photosynthetically active radiation (PAR) > 1500 umol m-2 s-1, GO3 and FO3 for all species declined at higher PAR. Annual AFst exceeded the threshold that could be tolerated by forest trees, suggesting a potential O3 risk for mixed conifer-broadleaf forest in Dinghushan. 参考文献 相似文献 引证文献

Sludge reduction by ozone: Insights and modeling of the dose-response effects

Applying ozone to the return flow in an activated sludge (AS) process is a way for reducing the residual solids production. To be able to extend the activated sludge models to the ozone-AS process, adequate prediction of the tri-atoms effects on the particulate COD fractions is needed. In this study, the biomass inactivation, COD mineralization, and solids dissolution were quantified in batch tests and dose-response models were developed as a function of the reacted ozone doses (ROD). Three kinds of model-sludge were used. S1 was a lab-cultivated synthetic sludge with two components (heterotrophs XH and XP). S2 was a digestate of S1 almost made by the endogenous residues, XP. S3 was from a municipal activated sludge plant. The specific ozone uptake rate (SO3UR, mgO3/gCOD.h) was determined as a tool for characterizing the reactivity of the sludges. SO3UR increased with the XH fraction and decreased with more XP. Biomass inactivation was exponential (e−β.ROD) as a function of the ROD doses. The percentage of solids reduction was predictable through a linear model (CMiner + Ysol ROD), with a fixed part due to mineralization (CMiner) and a variable part from the solubilization process. The parameters of the models, i.e. the inactivation and the dissolution yields (β, 0.008–0.029 (mgO3/mgCODini)−1 vs Ysol, 0.5–2.8 mg CODsol/mgO3) varied in magnitude, depending on the intensity of the scavenging reactions and potentially the compactness of the flocs for each sludge.

Differential regulation of volatile emission from Eucalyptus globulus leaves upon single and combined ozone and wounding treatments through recovery and relationships with ozone uptake

Both ozone and wounding constitute two key abiotic stress factors, but their interactive effects on plant constitutive and stress-elicited volatile (VOC) emissions are poorly understood. Furthermore, the information on time-dependent modifications in VOC release during recovery from a combined stress is very limited. We studied the modifications in photosynthetic characteristics and constitutive and stress-induced volatile emissions in response to single and combined applications of acute ozone (4, 5, and 6ppm) and wounding treatments through recovery (0.5–75h) in a constitutive isoprene and mono- and sesquiterpene emitter Eucalyptus globulus. Overall, the photosynthetic characteristics were surprisingly resistant to all ozone and wounding treatments. Constitutive isoprene emissions were strongly upregulated by ozone and combined ozone and wounding treatments and remained high through recovery phase, but wounding applied alone reduced isoprene emission. All stress treatments enhanced emissions of lipoxygenase pathway volatiles (LOX), mono- and sesquiterpenes, saturated aldehydes (C7-C10), benzenoids, and geranylgeranyl diphosphate (GGDP) pathway volatiles. Once elicited, GGDP volatile, saturated aldehyde and benzenoid emissions remained high through the recovery period. In contrast, LOX emissions, and total mono- and sesquiterpene emissions decreased through recovery period. However, secondary rises in total sesquiterpene emissions at 75h and in total monoterpenes at 25–50h were observed. Overall, acute ozone and wounding treatments synergistically altered gas exchange characteristics and stress volatile emissions. Through the treatments and recovery period, stomatal ozone uptake rate and volatile emission rates were poorly correlated, reflecting possible ozone-scavenging effect of volatiles and thus, reduction of effective ozone dose and elicitation of induced defense by the acute ozone concentrations applied. These results underscore the important role of interactive stresses on both constitutive and induced volatile emission responses.

基于树干液流技术的北京市刺槐冠层吸收臭氧特征研究

PDF HTML阅读 XML下载 导出引用 引用提醒 基于树干液流技术的北京市刺槐冠层吸收臭氧特征研究 DOI: 10.5846/stxb201208261205 作者: 作者单位: 北京市农林科学院林业果树研究所,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,北京教学植物园 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41030744，31170424）；城市与区域生态国家重点实验室科研专项资助项目（SKLURE2008-1） Ozone uptake at the canopy level in Robinia pseudoacacia in Beijing based on sap flow measurements Author: Affiliation: Institute of Forestry and Pomology,Beijing Academy of Agriculture and Forestry Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,,Beijing Teaching Botanical Garden Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球范围内加速的城市化导致空气质量严重退化。随着北京市建设范围不断扩大和机动汽车数量迅猛增长，空气污染日益严重。浓度不断增加的近地层臭氧作为影响全球气候变化的重要因素和危害人类健康、动植物生长的二次污染物，受到广泛关注。城市树木能够有效地去除大气污染物，进而提高空气质量。目前已有很多研究关于区域尺度上城市树木吸收臭氧，然而，冠层尺度上城市树木吸收臭氧特征少有研究。因此，基于树干液流技术，结合天气变化和大气臭氧浓度分析，研究夏秋季节北京市典型绿化树种刺槐（Robinia pseudoacacia）整树冠层吸收臭氧特征及环境影响因素。结果表明，在日尺度上，刺槐吸收臭氧速率变化呈单峰曲线，于15：00左右达到峰值；夏季峰值范围较宽，秋季峰值范围较窄；中午前后累积吸收臭氧量增加最明显。在季节尺度上，夏季刺槐吸收臭氧速率高于秋季；夏季累积吸收臭氧量显著增加，秋季略有增加。刺槐吸收臭氧的时间变化规律取决于大气臭氧浓度和冠层对臭氧的导度。臭氧浓度日变化和季节变化明显，导致刺槐吸收臭氧速率时间变化格局与之接近。在一定的臭氧浓度下，刺槐吸收臭氧速率的变化主要由冠层对臭氧的导度调控，进而受水汽压亏缺和总辐射的影响。随着水汽压亏缺降低，刺槐冠层对臭氧的导度明显下降；总辐射大于600 W/m2，冠层对臭氧的导度迅速下降。研究树种刺槐单位冠层投影面积上年吸收臭氧量约为0.16 g/m2，明显低于基于模型得到的结果，表明评估森林受臭氧危害的风险应考虑树种冠层臭氧通量。 Abstract:The accelerating global urbanization caused severe air pollutions. In Beijing, the air pollution has been exacerbated due to the wide-spread construction activities and increasing number of vehicles. The increasing concentration of ozone (O3) in the troposphere has been recognized as a source of air pollution, due to its adverse effects on human health and plant and animal growth, and its contribution to global climate change. O3 is known to impact forest trees in many ways including morphological and histological injuries, decreasing photosynthesis, increasing respiration, and alteration of carbon allocation and water balance. Considerable researches have been conducted to investigate ozone uptake by urban forests at the regional scale. On the other hand, trees are able to improve urban air quality by taking up and removing gaseous pollutants, and the O3 uptake by urban forests at the regional scale has been extensively studied. However, research on O3 uptake by urban trees at the canopy scale is rare. The main objectives of this study are: (1) to quantify the whole-tree O3 uptake by Robinia pseudoacacia, one of urban greening tree species in Beijing; and (2) to examine how O3 flux in R. pseudoacacia trees is regulated by the stomata and environmental conditions. In this study, the whole-tree O3 uptake in R. pseudoacacia trees during spring and summer was estimated based on sap flow measurements and the data of micro-climate and ambient O3 concentration were also collected. The diurnal ozone uptake rate (FO3) by R. pseudoacacia showed a single peak pattern with the maximum rate occurring at around 15:00 pm. The diurnal FO3 showed a narrow peak during summer and a wide peak during autumn. The most obvious increase in accumulated stomatal ozone flux(AFst)occurred around noon time. FO3 showed a seasonal pattern with higher values found in summer than in autumn. The increase in AFst was most obvious in summer than in autumn. The diurnal and seasonal patterns of O3 uptake were related to the temporal variations of ambient air O3 concentrations and canopy conductance (GO3). Ambient air O3 concentration showed a similar diurnal and seasonal pattern to FO3. Under a given ambient air O3 concentrations, the whole-tree FO3 was dependent on canopy conductance, and hereby was further influenced by the vapour pressure deficit (D) and total radiation (Rs). GO3 decreased exponentially with increasing D. High D caused low GO3, and thus low FO3 in spite of relatively high ambient air O3 concentrations. On the contrary, GO3 was high under low D conditions, and thus FO3 was high in spite of relatively low ambient air O3 concentrations. However, FO3 was relatively low under very low D conditions, such as in early mornings, which may be attributed to the weak photosynthesis and small stomatal apertures in the early morning at this time. Moreover, GO3 decreased rapidly with increasing Rs when Rs was higher than 600 W/m2. Similarly, ambient air O3 concentration decreased with increasing Rs when Rs was higher than 800 W/m2. Therefore, FO3 exhibited an asymmetric single-peak pattern: FO3 slightly increased with increasing Rs when Rs was below 800 W/m2, however, it decreased rapidly with increasing Rs when Rs was higher than 800 W/m2. The annual O3 uptake by R. pseudoacacia trees estimated in our study was 0.16 g/m2, which was much lower than the values estimated from the Urban Forest Effects Model. This difference suggests the necessity to consider the O3 uptake flux on canopy level when evaluate the O3 risks on urban trees. 参考文献 相似文献 引证文献

Ozone dynamics and snow‐atmosphere exchanges during ozone depletion events at Barrow, Alaska

The behavior of lower atmospheric ozone and ozone exchanges at the snow surface were studied using a suite of platforms during the Ocean‐Atmosphere‐Sea Ice‐Snow (OASIS) Spring 2009 experiment at an inland, coastal site east of Barrow, Alaska. A major objective was to investigate if and how much chemistry at the snow surface at the site contributes to springtime ozone depletion events (ODEs). Between March 8 and April 16, seven ODEs, with atmospheric ozone dropping below 1.0 ppbv, were observed. The depth of the ozone‐depleted layer was variable, extending from the surface to ∼200–800 m. ODEs most commonly occurred during low wind speed conditions with flow coming from the Arctic Ocean. Two high‐sensitivity ozone chemiluminescence instruments were used to accurately define the remaining sub‐ppbv ozone levels during ODEs. These measurements showed variable residual ODE ozone levels ranging between 0.010 and 0.100 ppbv. During the most extended ODE, when ozone remained below 1.0 ppbv for over 78 h, these measurements showed a modest ozone recovery or production in the early afternoon hours, resulting in increases in the ozone mixing ratio of 0.100 to 0.800 ppbv. The comparison between high‐sensitivity ozone measurements and BrO measured by longpath differential absorption spectroscopy (DOAS) during ODEs indicated that at low ozone levels formation of BrO is controlled by the amount of available ozone. Measurements of ozone in air drawn from below the snow surface showed depleted ozone in the snowpack, with levels consistently remaining &lt;6 ppbv independent of above‐surface ambient air concentrations. The snowpack was always a sink of ozone. Ozone deposition velocities determined from ozone surface flux measurements by eddy covariance were on the order of 0.01 cm s−1, which is of similar magnitude as ozone uptake rates found over snow at other polar sites that are not subjected to ODEs. The results from these multiple platform measurements unequivocally show that snow‐atmosphere chemical exchanges of ozone at the measurement site do not exhibit a major contribution to ozone removal from the boundary layer and the formation of ODE.

Atmosphere‐ocean ozone fluxes during the TexAQS 2006, STRATUS 2006, GOMECC 2007, GasEx 2008, and AMMA 2008 cruises

A ship‐based eddy covariance ozone flux system was deployed to investigate the magnitude and variability of ozone surface fluxes over the open ocean. The flux experiments were conducted on five cruises on board the NOAA research vesselRonald Brownduring 2006–2008. The cruises covered the Gulf of Mexico, the southern as well as northern Atlantic, the Southern Ocean, and the persistent stratus cloud region off Chile in the eastern Pacific Ocean. These experiments resulted in the first ship‐borne open‐ocean ozone flux measurement records. The median of 10 min oceanic ozone deposition velocity (vd) results from a combined ∼ 1700 h of observations ranged from 0.009 to 0.034 cm s−1. For the Gulf of Mexico cruise (Texas Air Quality Study (TexAQS)) the median vd (interquartile range) was 0.034 (0.009–0.065) cm s−1 (total number of 10 min measurement intervals, Nf = 1953). For the STRATUS cruise off the Chilean coast, the median vd was 0.009 (0.004–0.037) cm s−1 (Nf = 1336). For the cruise from the Gulf of Mexico and up the eastern U.S. coast (Gulf of Mexico and East Coast Carbon cruise (GOMECC)) a combined value of 0.018 (0.006–0.045) cm s−1 (Nf = 1784) was obtained (from 0.019 (−0.014–0.043) cm s−1, Nf = 663 in the Gulf of Mexico, and 0.018 (−0.004–0.045) cm s−1, Nf = 1121 in the North Atlantic region). The Southern Ocean Gas Exchange Experiment (GasEx) and African Monsoon Multidisciplinary Analysis (AMMA), the Southern Ocean and northeastern Atlantic cruises, respectively, resulted in median ozone vd of 0.009 (−0.005–0.026) cm s−1 (Nf = 2745) and 0.020 (−0.003–0.044) cms−1 (Nf = 1147). These directly measured ozone deposition values are at the lower end of previously reported data in the literature (0.01–0.12 cm s−1) for ocean water. Data illustrate a positive correlation (increase) of the oceanic ozone uptake rate with wind speed, albeit the behavior of the relationship appears to differ during these cruises. The encountered wide range of meteorological and ocean biogeochemical conditions is used to investigate fundamental drivers of oceanic O3 deposition and for the evaluation of a recently developed global oceanic O3 deposition modeling system.

Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland

Abstract. A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April–August 2004) of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the gradient method incorporating tower measurements of (a) ozone gradients measured by commercial ultraviolet absorption analyzers, (b) ambient temperature gradients using aspirated thermocouple sensors, and (c) wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measurement height. The developed protocol resulted in an uncertainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of ∼8 × 10−3μg m−2 s−1, respectively ∼0.01 cm s−1 for the ozone deposition velocity for typical environmental conditions encountered at Summit. Uncertainty in the 30-min ozone exchange measurements (evaluated by the Monte Carlo statistical approach) was on the order of 10−2 cm s−1. This uncertainty typically accounted to ~20–100% of the ozone exchange velocities that were determined. These measurements are among the most sensitive ozone deposition determinations reported to date. This flux experiment allowed for measurements of the relatively low ozone uptake rates encountered for polar snow, and thereby the study of their environmental and spring-versus-summer dependencies.

Increased steady state uptake of ozone on soot due to UV/Vis radiation

[1] Oxidative aging of soot particles in the atmosphere may contribute significantly to their climate and human health effects. With their large specific surface area, soot particles are an ideal substrate for heterogeneous reactions. However, these reactions are typically of limited relevance due to deactivation of the surface. Here we show that light in the UV-A and visible (Vis) range significantly enhances the reactivity of soot with ozone. In these laboratory experiments, soot from a propane burner was first “passivated” with ozone (ozone mixing ratio of 300 pbb) for 15 h before ozone uptake was measured in presence of UV radiation. Passivated soot was shown to be reactivated during irradiation with a 4 times higher steady state ozone uptake rate as compared to dark conditions. The uptake increased even by a factor of 15 when humidity (95% relative humidity) was introduced into the system. Possible mechanisms of ozone uptake are discussed. Further analysis using near edge X-ray absorption spectroscopy and contact angle measurements showed a decrease of oxygenated functional groups in the soot upon exposure to ozone and ozone in combination with light.

Secondary pollutants from ozone reactions with ventilation filters and degradation of filter media additives

Prior research suggests that chemical processes taking place on the surface of particle filters employed in buildings may lead to the formation of harmful secondary byproducts. We investigated ozone reactions with fiberglass, polyester, cotton/polyester and polyolefin filter media, as well as hydrolysis of filter media additives. Studies were carried out on unused media, and on filters that were installed for 3 months in buildings at two different locations in the San Francisco Bay Area. Specimens from each filter media were exposed to {approx}150 ppbv ozone in a flow tube under a constant flow of dry or humidified air (50percent RH). Ozone breakthrough was recorded for each sample over periods of {approx}1000 min; the ozone uptake rate was calculated for an initial transient period and for steady-state conditions. While ozone uptake was observed in all cases, we did not observe significant differences in the uptake rate and capacity for the various types of filter media tested. Most experiments were performed at an airflow rate of 1.3 L/min (face velocity = 0.013 m/s), and a few tests were also run at higher rates (8 to 10 L/min). Formaldehyde and acetaldehyde, two oxidation byproducts, were quantified downstream of each sample. Those aldehydes (m/zmore » 31 and 45) and other volatile byproducts (m/z 57, 59, 61 and 101) were also detected in real-time using Proton-Transfer Reaction - Mass Spectrometry (PTR-MS). Low-ppbv byproduct emissions were consistently higher under humidified air than under dry conditions, and were higher when the filters were loaded with particles, as compared with unused filters. No significant differences were observed when ozone reacted over various types of filter media. Fiberglass filters heavily coated with impaction oil (tackifier) showed higher formaldehyde emissions than other samples. Those emissions were particularly high in the case of used filters, and were observed even in the absence of ozone, suggesting that hydrolysis of additives, rather than ozonolysis, is the main formaldehyde source in those filters. Emission rates of formaldehyde and acetaldehyde were not found to be large enough to substantially increase indoor concentrations in typical building scenarios. Nevertheless, ozone reactions on HVAC filters cannot be ignored as a source of low levels of indoor irritants.« less

Atmosphere‐ocean ozone exchange: A global modeling study of biogeochemical, atmospheric, and waterside turbulence dependencies

The significance of the removal of tropospheric ozone by the oceans, covering ∼2/3 of the Earth's surface, has only been addressed in a few studies involving water tank, aircraft, and tower flux measurements. On the basis of results from these few observations of the ozone dry deposition velocity (VdO3), atmospheric chemistry models generally apply an empirical, constant ocean uptake rate of 0.05 cm s−1. This value is substantially smaller than the atmospheric turbulent transport velocity for ozone. On the other hand, the uptake is higher than expected from the solubility of ozone in clean water alone, suggesting that there is an enhancement in oceanic ozone uptake, e.g., through a chemical destruction mechanism. We present an evaluation of a global‐scale analysis with a new mechanistic representation of atmosphere‐ocean ozone exchange. The applied atmosphere chemistry‐climate model includes not only atmospheric but also waterside turbulence and the role of waterside chemical loss processes as a function of oceanic biogeochemistry. The simulations suggest a larger role of biogeochemistry in tropical and subtropical ozone oceanic uptake with a relative small temporal variability, whereas in midlatitude and high‐latitude regions, highly variable ozone uptake rates are expected because of the stronger influence of waterside turbulence. Despite a relatively large range in the explicitly calculated ocean uptake rate, there is a surprisingly small sensitivity of simulated Marine Boundary Layer ozone concentrations compared to the sensitivity for the commonly applied constant ocean uptake approach. This small sensitivity points at compensating effects through inclusion of the process‐based ocean uptake mechanisms to consider variability in oceanic O3 deposition consistent with that in atmospheric and oceanic physical, chemical, and biological processes.

Defining hybrid poplar (Populus deltoides × Populus trichocarpa) tolerance to ozone: identifying key parameters

This study examined whether two genotypes of hybrid poplar (Populus deltoides x Populus trichocarpa), previously classified as ozone tolerant and ozone sensitive, had differing physiological and biochemical responses when fumigated with 120 nL L(-1) ozone for 6 h per day for eight consecutive days. Isoprene emission rate, ozone uptake and a number of physiological and biochemical parameters were investigated before, during and after fumigation with ozone. Previous studies have shown that isoprene protects plants against oxidative stress. Therefore, it was hypothesized that these two genotypes would differ in either their basal isoprene emission rates or in the response of isoprene to fumigation by ozone. Our results showed that the basal emission rates of isoprene, physiological responses and ozone uptake rates were all similar. However, significant differences were found in visible damage, carotenoids, hydrogen peroxide (H(2)O(2)), thiobarbituric acid reactions (TBARS) and post-fumigation isoprene emission rates. It is shown that, although the classification of ozone tolerance or sensitivity had been previously clearly and carefully defined using one particular set of parameters, assessment of other key variables does not necessarily lead to the same conclusions. Thus, it may be necessary to reconsider the way in which plants are classified as ozone tolerant or sensitive.

Ozone interactions with human hair: Ozone uptake rates and product formation

In this study, the cumulative ozone uptake, the ozone reaction probability and product yields of volatile aldehydes and ketones were quantified for human scalp hair. Hair was chosen because ozone reacts readily with skin oils and the personal-care products that coat hair. Due to their proximity to the breathing zone, these reactions can influence personal exposure to ozone and its volatile reaction products. Hair samples were collected before and after washing and/or application of personal hair-care products. Samples were exposed to ozone for 24 h in a tubular Teflon reactor; ozone consumption rates and product emission rates were quantified. The mean values of integrated ozone uptake, initial and final follicle reaction probability values for eight washed and unwashed samples were, respectively, 5.1±4.4 μmol O 3 g −1, (13±8)×10 −5, and (1.0±1.3)×10 −5. Unwashed hair taken close to the scalp exhibited the highest integrated ozone uptake and reaction probability, indicating that scalp oils are responsible for much of the ozone reactivity. Otherwise there was no significant difference between washed and unwashed hair. Compounds (geranyl acetone, 6-methyl-5-hepten-2-one, and decanal) associated with ozone reacting with sebum were observed as secondary products more frequently from unwashed hair than for washed hair and the summed yield of aldehydes ranged from 0.00 to 0.86. Based on reaction probabilities, cumulative ozone uptake and typical sebum generation rates, ozone flux to skin and hair is anticipated to be nearly transport limited, reducing personal exposure to ozone and increasing exposure to reaction products.

Effects of ozone impact on the gas exchange and chlorophyll fluorescence of juvenile birch stems ( Betula pendula Roth.)

Effects of ozone impact on gas exchange and chlorophyll fluorescence of juvenile birch ( Betula pendula) stems and leaves were investigated. Significant differences in the response of leaves and stems to ozone were found. In leaves, O 3 exposure led to a significant decline in photosynthetic rates, whereas stems revealed an increased dark respiration and a concomitant increase in corticular photosynthesis. In contrast to birch leaves, corticular photosynthesis appeared to support the carbon balance of stems or even of the whole-tree under O 3 stress. The differences in the ozone-response between leaves and stems were found to be related to ozone uptake rates, and thus to inherent differences in leaf and stem O 3 conductance.

The oleic acid-ozone heterogeneous reaction system: products, kinetics, secondary chemistry, and atmospheric implications of a model system – a review

Abstract. The heterogeneous processing of organic aerosols by trace oxidants has many implications to atmospheric chemistry and climate regulation. This review covers a model heterogeneous reaction system (HRS): the oleic acid-ozone HRS and other reaction systems featuring fatty acids, and their derivatives. The analysis of the commonly observed aldehyde and organic acid products of ozonolysis (azelaic acid, nonanoic acid, 9-oxononanoic acid, nonanal) is described. The relative product yields are noted and explained by the observation of secondary chemical reactions. The secondary reaction products arising from reactive Criegee intermediates are mainly peroxidic, notably secondary ozonides and α-acyloxyalkyl hydroperoxide oligomers and polymers, and their formation is in accord with solution and liquid-phase ozonolysis. These highly oxygenated products are of low volatility and hydrophilic which may enhance the ability of particles to act as cloud condensation nuclei (CCN). The kinetic description of this HRS is critically reviewed. Most kinetic studies suggest this oxidative processing is either a near surface reaction that is limited by the diffusion of ozone or a surface based reaction. Internally mixed particles and coatings represent the next stage in the progression towards more realistic proxies of tropospheric organic aerosols and a description of the products and the kinetics resulting from the ozonolysis of these proxies, which are based on fatty acids or their derivatives, is presented. Finally, the main atmospheric implications of oxidative processing of particulate containing fatty acids are presented. These implications include the extended lifetime of unsaturated species in the troposphere facilitated by the presence of solids, semi-solids or viscous phases, and an enhanced rate of ozone uptake by particulate unsaturates compared to corresponding gas-phase organics. Ozonolysis of oleic acid enhances its CCN activity, which implies that oxidatively processed particulate may contribute to indirect forcing of radiation.

Toward an ozone standard to protect vegetation based on effective dose: a review of deposition resistances and a possible metric

Present air quality standards to protect vegetation from ozone are based on measured concentrations (i.e., exposure) rather than on plant uptake rates (or dose). Some familiar cumulative exposure-based indices include SUM06, AOT40, and W126. However, plant injury is more closely related to dose, or more appropriately to effective dose, than to exposure. This study develops and applies a simple model for estimating effective ozone dose that combines the plant canopy's rate of stomatal ozone uptake with the plant's defense to ozone uptake. Here the plant defense is explicitly parameterized as a function of gross photosynthesis and the model is applied using eddy covariance (ozone and CO2) flux data obtained at a vineyard site in the San Joaquin Valley during the California Ozone Deposition Experiment (CODE91). With the ultimate intention of applying these concepts using prognostic models and remotely sensed data, the pathways for ozone deposition are parameterized (as much as possible) in terms of canopy LAI and the surface friction velocity. Results indicate that (1) the daily maximum potential for plant injury (based on effective dose) tends to coincide with the daily peak in ozone mixing ratio (ppbV), (2) potentially there are some significant differences between ozone metrics based on dose (no plant defense) and effective dose, and (3) nocturnal conductance can contribute significantly to the potential for plant ozone injury.

Relationships between ozone exposure and yield loss in European wheat and potato—a comparison of concentration- and flux-based exposure indices

Abstract Data from open-top chamber experiments with field grown crops, performed in Sweden, Finland, Belgium, Italy and Germany, were combined to derive relationships between yield and ozone exposure for wheat (Triticum aestivum L.) and potato (Solanum tuberosum L.). Three different exposure indices were compared: AOT40 (accumulated exposure over a threshold ozone concentration of 40 nmol mol−1), CUOt (cumulative stomatal uptake of ozone, using a constant ozone uptake rate threshold of t nmol m−2 s−1) and mAOTc0 (conductance modified AOT using a threshold concentration for ozone of c0 nmol mol−1). The latter is essentially a combination of AOT and CUO. Ozone uptake was estimated using a Jarvis-type multiplicative model for stomatal conductance. In terms of correlation between relative yield (RY) and ozone exposure, CUO5, the CUO index with an ozone uptake rate threshold of 5 nmol m−2 s−1, performed best for both wheat and potato, resulting in r2 values of 0.77 and 0.64, respectively. CUO5 performed considerably better in terms of the correlation between RY and ozone exposure, than AOT40 for wheat, while mAOT10, the best performing mAOT index in this case, was intermediate in performance for this crop. For potato, the differences between the different ozone exposure indices AOT40, CUO5 and mAOT20 (the mAOT index performing best for potato) in the correlation between RY and ozone exposure were relatively small. To test the assumption that the non-stomatal deposition of ozone was negligible for the uppermost, sunlit leaves, measurements of ozone uptake in relation to leaf conductance for water vapor of wheat leaves in a cuvette system were used. The non-stomatal deposition of ozone to the leaves turned out to be comparatively small. Based on the non-stomatal conductance (gns=15 mmol m−2 s−1) estimated for the wheat leaves in the cuvette system, it was concluded that the consequence of omitting the non-stomatal conductance is small. In conclusion the study indicated that the ozone uptake based approach showed a high degree of fitting along a north-south European transect of pedoclimatic conditions, and represents a better and more relevant approach to the quantification of ozone effects on crops growth than the use of ozone exposure indices purely based on ozone concentrations.