I am in Wellfleet, on Cape Cod, visiting family, who somehow don't seem to appreciate my preoccupation with the collapsing ecosystem. I found this paper (which starts on p. 189 of Production Practices and Quality Assessment of Food Crops, Volume I, published in 2004, so remember the background levels in the tropospheric atmosphere have been inexorably rising) in which two Spanish researchers review the literature about ozone impacts on vegetation.
Ozone (O3) is regarded as one of the most damaging air pollutants to which plants are exposed (Thompson, 1992). Over large rural areas of industrialized countries, its average monthly concentration increased during the last century to between 20 and 80 ppb (Lucas et al., 1993; Heath, 1994a). During episodes of severe air pollution, concentrations as high as 400 to 500 ppb have been monitored (Seinfeld, 1989). Ozone is a secondary pollutant resulting from photochemical reactions (mainly volatile organic compounds and nitrogen oxides). Under favourable meteorological conditions, ozone may accumulate in the troposphere and reach a level that causes significant decrease in growth and yield of ozone-sensitive species in many parts of the world. The problem of phytotoxicity is well established in Europe (Jäger et al., 1992) and North America (Heck et al., 1988). More recently, high concentrations of ozone have also been measured (Wahid et al., 1995).
Ozone enters the leaves through the stomata and diffuses within the apoplast. In this microenvironment it is intensively reactive and produces high levels of toxic compounds such as hydroxyl and superoxide radicals, hydrogen peroxide and other reactive oxygen species (Heath and Taylor, 1997; Pell et al., 1997). These active oxygen species react with proteins, lipids, and plasma membrane. Antioxidative defence activity systems may prevent this damage. Impact on plant crop yield ranges from minimal visible symptoms to substantial inhibition of productivity, including reduced photosynthetic capacity, enhanced rate of maintained respiration, and increased retention of fixed carbon in source leaves (Lefohn, 1992; Alscher and Wellburn, 1994). These plant responses can affect the plants’ abilities to respond to further stress attacks. The action of ambient O3 on the plant defence system enhances attack by pathogens but may lead to induce resistance (Sandermann et al., 1998). In addition, the impact of O3 is profoundly influenced by other environmental factors.
Agricultural yield loss in the USA is approximately 1 to 2 billion dollars each year (US EPA, 1998). In addition to this considerable yield reduction, damaging of forest ecosystems and a reduction of lung functions in healthy people and people with an impaired respiratory system have been demonstrated. Despite the economic significance of these effects on crops, the mechanisms of the action of O3 are still poorly understood.
Visual injury to crop plants caused by O3 can range from severe necrosis and death of much or all the exposed tissue, to mild chlorosis (Heagle et al., 1973; Deveaou et al., 1987; Heagle et al., 1987; Mulchi et al.; 1988, Heggestad, 1997). Acute injury usually involves necrosis, varying from general large die-back areas, to small areas, stipples or flecks; such injuries occurring as a result of fumigation with high doses of O3. Chronic injury results from exposures to sub-acute dosage. Chlorosis and death of isolated cells are generally observed in these conditions.
14. INDICATORS OF OZONE STRESS
Initial studies on the effect of O3 on crop species were centred on the reduction of agronomical yield. Later on, in order to understand the action mechanism of O3 this interest area of agronomical yield has been displaced by other injury effects such us physiological responses. The physiological changes observed in the presence of O3 polluted air are reduced net photosynthesis, increased respiration rate, membrane lipid peroxidation, enhanced rate of senescence, reduced transpiration, and inhibition of translocation to roots (Cooley and Manning, 1987; Darrall, 1989; Heath, 1994b; Dizengemel and Pertins, 1994; Mudd, 1996; Taylor and Ferris, 1996; Sandermannn, 1996; Langebartels et al., 1997; Heath and Taylor, 1997; Pell et al., 1997; Schraudner et al., 1997). The most important of these techniques are spectral reflectance, fluorescence and videography.
Imaging techniques (reflectance and near infrared imaging) are used for earlier detection of plant stress induced by tropospheric O3 (Chaerle and van der Straeten, 2000). Stress induced physiological damage in plants is manifested in altered reflectance spectrum. Several spectral indices have been proposed as stress indi- cators (Hunt et al., 1987). Leaf spectral reflectance as a rapid method for detecting O3 stress has been used for crop species (Runeckles and Resh, 1975; Schutt et al., 1984; Carter et al., 1992; Williams and Ashenden, 1992). A decreased infrared reflectance is detectable for clover leaves after O3 treatment, although no visible foliar damage symptoms could be observed (Kraft et al., 1996). Ozone-treated leaves showed lower water content, photosynthetic pigments, and PSII activity (Rudorff et al., 1996).
Measurement of chlorophyll a fluorescence is a technique for measuring incipient O3 effect in the field (Schreiber et al., 1998 and references therein). This
technique is rapid, non-invasive, and non-destructive and requires relatively inex- pensive instrumentation. The utility of fluorescence measurements in the field as an indicator of plant responses to environmental conditions is well established (Bolhar-Nordenkampf et al., 1989). Fluorescence measurements are mainly used to determine activities of photosynthetic apparatus, such as the fluxes of absorbed photons, trapped energy or transported electron. Therefore, fluorescence measurements can be used before any changes in the visual appearance of leaves have occurred or even when no changes in their chemical composition can be detected. The ratio of variable fluorescence to maximal fluorescence is used to estimate maximum quantum yield of PSII. This parameter, also called photochemical efficiency estimates any disturbance in electron transfer between PSII and PSI. Ambient O3 exposure causes a decrease in the photochemical efficiency (Guidi et al., 1997). Photochemical and non-photochemical quenching coefficients are also utilized to detect the primary acceptor of PSII oxidation and heat emission (Reiling and Davison, 1994). Both parameters are modified by the presence of O3.
Fluorescence imaging is a newly developed tool (Lichtenthaler and Miehé, 1997; Oxborough and Baker, 1997). It is used to identify the primary site of damage and to characterize some features of O3 damage when leaves are exposed to O3. High resolution image of bean leaves exposed to O3 fumigation showed localized decreases in PSII. Photochemical efficiencies were accompanied by an increase in minimal fluorescence level, which is indicative of PSII inactivation (Leipner et al., 2001).
It is expected that the application of chlorophyll fluorescence and chlorophyll fluorescence imaging will be very successful in detecting the incipient effects of O3 stress.
In addition to crop yield loss, damage of forest ecosystems and a reduction of lung function in healthy people and people with an impaired respiratory system have been demonstrated (Schmieden and Wild, 1995; Sandermann et al., 1997, 1998; US EPA, 1998). Because of these serious environmental problems as a result of the presence of O3 in the lowest layer of the atmosphere many efforts have been made to reduce the level of O3. National and international limits for ambient O3 exist, but are usually exceeded in North America and Western Europe. Despite massive and costly efforts, countries in Europe and North America still experi- ence a severe problem (Photochemical Oxidants Review Group, 1990; National Research Council, 1991). Ground-level O3 is the most difficult to control of the air pollutants (US EPA, 1998). This difficulty is mainly due to two facts: (a) O3 is not emitted directly into the atmosphere by specific sources. Ozone-forming volatile organic compounds include gasoline vapours, chemical solvents, combustion fuels and consumer products. (b) The O3-precursos can be transported hundreds of km by atmosphere winds. Unfortunately, up to now the control of O3-precursors has not been successful.
16.1. Chemical protective agents
Diverse groups of chemical compounds have been utilized to protect plants against O3 injury. These groups include antioxidants, antitranspirants, growth regulators, fungicides, herbicides, and antisenescence agents (for a recent review see Manning, 1999). Many reports suggest that the chemical agents protect against O3, but more experimental data are necessary to demonstrate the proposed reduction of injury symptoms clearly. The most frequently used are antioxidant ethylene diurea, the systemic fungicide benomyl, and the antioxidant ascorbic acid.
EPA Delays Issuing Final Ozone Standards Until October, Cites Need for More AnalysisBy Andrew ChilderThe Environmental Protection Agency said Aug. 23 that it will delay finalizing its air quality standards for ozone until October so it can continue to analyze information it received during the public comment period. Issuing of the final national ambient air quality standards for ozone had been expected in August. “EPA remains committed to protecting public health from the dangers of ground-level ozone, a key component of smog,” EPA said in its statement. “We are continuing to carefully consider the proposed options and the information we received during the public comment period on the January 2010 proposal. There will be a slight delay in finalizing our decision on any new ozone standards. We expect to finalize the standards towards the end of October 2010. We have spoken with the litigants and have updated the court on our status.” EPA agreed to voluntarily reconsider the ozone air standards, set in 2008, after several states and environmental groups filed lawsuits in the U.S. Court of Appeals for the District of Columbia Circuit challenging the rules as too weak to protect public health ( Mississippi v. EPA, D.C. Cir., No. 08-1200, status report filed 8/20/10). The agency filed a status report in the case Aug. 20, informing the court of the delay. EPA set both the primary and secondary standards for the pollutant at 0.075 part per million in 2008. The primary standard is set to protect public health while the secondary standard is set to protect crops and public welfare. As part of the reconsideration process, EPA has proposed setting the primary ozone standard in a range between 0.060 ppm and 0.070 ppm—the range recommended by the agency's Clean Air Scientific Advisory Committee in 2008. To protect crops and forests, EPA also proposed setting a secondary seasonal standard within a range between 7 ppm-hours and 15 ppm-hours—the weighted, cumulative exposure to ozone during daylight hours over a three-month growing season (75 Fed. Reg. 2938; 199).Environmental Groups ‘Disappointed.'Janice Nolen, assistant vice president for policy and advocacy for the American Lung Association, told BNA she was “extremely disappointed” by the delay. The group was a litigant in the lawsuits challenging the standards as insufficient. “It sounds like a little delay—two months—but it does mean it takes longer to get things like [nonattainment] designations started,” she said. Other environmental advocates said they were also disappointed by the delay but expected EPA to set more protective standards for the pollutant. “We'd like them to make the best possible decision rather than a quick, bad decision,” Clean Air Watch President Frank O'Donnell told BNA.
Industries, Senators Fear Rule's ImpactIndustry groups and some senators have expressed concern about how EPA's revised ozone standards might impact businesses, particularly those with pending operating permit applications. Richard Alonso, an attorney at Bracewell & Giuliani who represents power plants, boiler operators, and the cement industry, told BNA the delay was “good news.” He said industry groups hope EPA will have readied its implementation plan for the revised air standards at the same time it finalizes the rule to avoid any unnecessary delays with permitting. “EPA's position is they plan to apply it to pending permits,” Alonso said. “I hope this is a sign EPA is going develop guidance and implementation issues before actually issuing the rule rather than after issuing the rule.” Seven senators sent a letter to EPA Administrator Lisa Jackson Aug. 6 asking the agency to retain the 2008 air standards for ozone, arguing that setting a more protective standard would require industrial facilities to install expensive pollution controls that could lead to increased energy costs and job losses. The letter also argued EPA had not conducted any additional research into the health effects of ozone pollution since setting the 2008 standards. The letter was signed by Sens. Evan Bayh (D-Ind.), Kit Bond (R-Mo.), Mary Landrieu (D-La.), Dick Lugar (R-Ind.), Claire McCaskill (D-Mo.), David Vitter (R-La.), and George Voinovich (R-Ohio).
EPA Moving Closer to Decision on Limits For Greenhouse Gases in Performance Rules
Performance Standards Cover Specific SectorsThe new source performance standards establish a “floor” for the emissions control requirements in a given sector, while the PSD program could require additional controls beyond that level. In some case, existing sources that are not modified in any way could be required to adhere to the performance standards. Those plants would not be subject to the PSD program. EPA has wide discretion in deciding which source categories to regulate under Section 111. When EPA on Aug. 9 announced revised new source performance standards to control emissions of conventional pollutants from Portland cement manufacturing facilities, it declined to set greenhouse gas emissions limits. But the agency said in the preamble to the final rule that it “is working towards a proposal for GHG standards” for those plants. And the agency is eyeing other sectors as well. EPA is scheduled to propose revisions to new source performance standards for several industrial sectors, including electric power plants, in the next eight months, giving the agency opportunities to propose greenhouse gas emissions standards for these sectors. EPA said in a statement Aug. 26 that it “will begin to assess and potentially develop greenhouse gas emissions performance standards under the Clean Air Act for some of the highest emitting categories of large stationary sources—EGU's [electric generating utilities], refineries, and cement kilns.”
EPA Seeks More Information on Cement KilnsEPA said in the Portland cement rule, “Portland cement is one of the largest stationary source categories of GHG emissions, ranking as the third highest U.S. source of CO2 emissions.” The agency also cited “cost-effective control strategies for this source category that would provide an appropriate basis” for establishing greenhouse gas emissions limits. These include energy efficiency measures and materials substitution. EPA said it needs additional information on specific facilities before it proposes new standards for greenhouse gas emissions. The agency said it “will be sending out information requests to fill these information gaps so that we are able to propose a standard addressing GHGs in a timeframe that would allow the regulated community to make sound investment decisions in response to these [hazardous air pollutant] and NSPS requirements.” EPA said that it did not include greenhouse gas emissions limits when it proposed the Portland cement rule standards in 2008 because it was evaluating issues related to PSD requirements. By issuing the tailoring rule and several other rules, EPA said, it is addressing the concerns that caused it to not propose limits for greenhouse gas emissions from Portland cement plants.
Utility Proposal Expected in MarchSeveral states and environmental groups sued EPA in 2006 challenging the agency's conclusion at that time that it lacked the authority to set new source performance standards for greenhouse gas emissions from power plants. After the Supreme Court ruled in 2007 that greenhouse gases are air pollutants under the Clean Air Act in the Massachusetts v. EPA decision, EPA agreed to a remand to study the effect of the decision on new source performance standards (New York v. EPA, D.C. Cir., No. 06-1322, 9/24/08). According to information on EPA's Rulemaking Gateway, it has initiated proceedings for proposing revisions to the new source performance standards for electric utility boilers and plans to propose them in March 2011. Bruce Braine, vice president at American Electric Power Co., told BNA that EPA could base performance standards on energy efficiency, or it could base a standard on burning natural gas instead of coal. In the past, EPA has based performance standards on requirements for a specific fuel, Braine said. EPA is scheduled to propose new source performance standards for nitric acid production facilities in November. According to attorney David Bookbinder, formerly with the Sierra Club, nitric acid plants are a source of nitrous oxide, a potent greenhouse gas.
Skepticism Over EPA ActionBookbinder expressed skepticism that EPA will propose new source performance standards for greenhouse gas emissions. Bookbinder said the passages about greenhouse gas emissions in the Portland cement standards looked more like stalling than a promise of prompt action to propose standards. Bookbinder also said he has seen no indication that EPA will propose new source performance standards for utility boilers or for nitric acid plants. With the administration also seeking the dismissal of lawsuits against specific emitters under federal nuisance law, Bookbinder said, “It appears to me that they are going to continue regulating mobile sources, [but] not regulating stationary sources,” except under PSD. In contrast, John Walke, director of clean air programs at the Natural Resources Defense Council, called the Portland cement notice “welcome news,” signaling a willingness to move forward with new source performance standards for greenhouse gas emissions. Walke said he expects EPA to be able to move forward with standards for power plants without new information collection requests to the industry because it already has voluminous information on the facilities and their emissions.
"As the contemporary environmental movement built momentum in the mid-to-late 1960s, undermining the public trust in many a corporation, newly greened corporate images flooded the airwaves, newspapers and magazines. This initial wave of greenwash was labeled by former Madison Avenue advertising executive Jerry Mander and others at the time as 'ecopornography.'"
"It seems as if the warm but wet summer has been a key driver in the development of tree pathogens, with a number of cases making the headlines.
In April, a group of woodland experts expressed their fears for the future of British native oaks in light of the emergence of a disease called Acute Oak Decline, a bacterial infection that, they warned, could be as devastating for the English Landscape as Dutch elm disease in the 1970s."