Pallavi Saxena

Status of Air Pollutants after Implementation of CNG in Delhi

Air pollution kills more than 5.9 million people annually, with more than 90 per cent of these deaths in capital city of India, Delhi. For improving the status of air pollution in Delhi, various policies and laws have been implemented. But even after the implementation of CNG, there was no significant change of pollutants (NOx, O 3 , SPM, RSPM & CO) except SO 2 . The objective of our study is whether CNG conversion has impinged on the primary pollutant and tropospheric ozone pollution profile and for the improvement in the quality of air in post CNG period. To carry out the analysis, daily ambient air quality secondary data (Jan 2002-Dec 2009; Source-CPCB) of all the above discussed pollutants were used. For generating own data, NOX and O3 monitoring were carried out at four different sites viz. Site I (Yamuna Biodiversity Park, away from traffic intersection), Site II (Traffic intersection at outside YBP, outer ring road, Gandhi vihar), Site III (Aravalli Biodiversity Park, away from traffic intersection) and Site IV (traffic intersection at outside ABP, ring road, Vasant vihar) during monsoon season (Aug-Sept, 2009). The concentration of ozone was higher at sites which are at traffic intersection (Site II & IV) than those which are away from traffic intersection (Site I & III). The results however, do not indicate an all round improvement in ambient air quality of Delhi. Hence, our short term study suggests that after the implementation of CNG in Delhi there is no remarkable improvement in the status of the pollutants and moreover, the sites which are near to traffic intersection possess high concentration of pollutants than the sites which are away from traffic intersection.

Biochemical Effects of Air Pollutants on Plants

Urbanization and industrialization processes contribute significant amount of various air pollutants such as SO2, NO2, CO, particulate matter, etc. These pollutants affect plant health and emit various forms of SO2, NOx, and O3 which may act in combination of a variety of ways: additive, synergistic, and antagonistic. These pollutants can have a deleterious effect on a variety of biochemical and physiological processes and on the structural organization within the cells. Certain plant species are very sensitive to these pollutants resulting in well visible and measurable symptoms. Morphological damage is generally visible through lesions on the leaves, flowers, and fruits while biochemical and physiological changes which are invisible can be measured and quantified. In this chapter, biochemical effects on plants have been described. These symptoms can be used as indicators of air pollution stress for its early diagnosis and can be used as markers for a particular physiological disorder.

Plant Responses to Air Pollution

Poor air quality is known to have deleterious effects on the environment and human health. A variety of air pollutants are identifi ed at unprecedented levels. Particulate matter and oxides of sulfur and nitrogen are common pollutants of the atmosphere. The emissions of these criteria pollutants have been studied widely. An overview of their global and regional emissions is helpful in assessing the status of contributions from various sectors and effi cacy of control strategies over the years in both developed and developing nations of the world. Particulate matter levels in developed regions have been observed to have decreased substantially toward the end of the twentieth century, contrary to the trend of emissions in developing countries. Transportation and power generation sectors are key sources of PM emissions. Oxides of sulfur have been observed to have peaked in the 1970s and subsequently decreased thereafter on a global scale; however, the developing economies have registered a rise in emissions. Similar trend has been observed for oxides of nitrogen with decline of emissions from developed regions of the world and subsequent increase from developing countries in the earlier part of the twenty-fi rst century. Timely intervention of suitable strategies to combat emissions in developing regions is crucial to nullify the increasing trend of emissions. The present chapter provides an overview of three criteria air pollutants – particulate matter, oxides of sulfur, and oxides of nitrogen with respect to their changing global and regional emission scenario in the past decades and sector-wise contributions.

The impact of gasoline emission on plants – a review

ABSTRACT This review presents the status of knowledge about gasoline exhaust pollution and its impact biochemical and physiological characteristics of plants. Parameters on such as leaf conductance, membrane permeability, ascorbic acid, chlorophyll and relative water content have been used as indicators to assess the impact of gasoline exhaust pollution on plant health. Tolerant plants such as Mangifera indica Linn. are reported showing an insignificant decrease in the percentage of chlorophyll content (3.6%) and a significant increase in the percentage of ascorbic acid (84.6%) and sensitive plants such as Cassia fistula are reported showing a significant decrease in the percentage of chlorophyll (66.4%) as well as ascorbic acid (32.9%). In the case of ornamental plants, Dracaena deremensis has been reported to show an insignificant decrease in the chlorophyll content but a significant increase in the ascorbic acid, pH and relative water content, which were found to be in tolerant category, while Dianthus caryophyllus showed sensitive characteristics. Such plants can be used as sinks and bioindicators for gasoline exhaust pollution. Though several studies reported biochemical impacts of individual or combined exhaust gases on plant species, the cumulative effect of gasoline exhaust on plant species has not been studied extensively, especially in the developing countries.

Establishing Correlation Between Abiotic Stress and Isoprene Emission of Selected Plant Species

The atmospheric hydrocarbon budget influenced by a vast range of volatile organic compounds (VOCs) is both anthropogenic and biogenic in origin. Evolution of plant VOCs is a complex process affected by interactions of plants with biotic and abiotic factors in constantly changing environment but their functional role is still a matter of speculation. Isoprene (2-methyl 1,3-butadiene), a five-carbon hydrocarbon, is emitted from the leaves of many plant species. In the present study, isoprene emission potential of two urban plant species (Dalbergia sissoo and Nerium oleander) were measured using branch enclosure method at different selected sites on the basis of proximity to traffic density. In order to find out the dependence of isoprene emission with abiotic factors (temperature and photosynthetic active radiation PAR), regression analysis has been performed. In the case of Dalbergia sp. high temperature and PAR promote high isoprene emission during summer months. Thus, positive linear relationship gives the best fit between temperature, PAR, and isoprene emission rate during summer season as compared to other seasons, whereas in the case of Nerium sp., no such appropriate relationship was obtained. The study concludes that Dalbergia sissoo comes under high isoprene emission category, while Nerium oleander comes under BDL (below detection limit) variety. For any greenbelt development program, it is very important to select the type of plant species to be planted. The present small study reflects that Nerium oleander should be planted in the outskirts of selected areas and that planting of Dalbergia sissoo should be done on low scale so that the air remains clean and indirect production of tropospheric ozone, aerosol production will be minimized.

Ranking of BTEX with Respect to Ozone Formation by Development of Ozone Reactivity Scale

The high concentration of ground-level ozone is a serious problem in many areas. Ozone formation is non-linear process and is produced from the photochemical interactions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) in the troposphere. Generally, MIR (Maximum Incremental Reactivity) scale is one of the popular ones in the assessment of ozone formation potential of various VOC compounds. In this study, we have taken this scale into consideration for analysing the ranking of benzene, toluene, ethylbenzene and xylene (BTEX) at selected sites which are divided on the basis of near to traffic intersection and less vegetation (Site I) and away from traffic intersection with dense vegetation (Site II) during winter season (Nov’10–Feb’11). The results showed that the average concentration of ozone was found to be higher at Site I than Site II. As per MIR scale, irrespective of site and month, xylenes (m-/p-xylene plus o-xylene) are the most dominant contributor to ozone formation amongst BTEX. Toluene is the second largest contributor to ozone formation. Amongst all, ozone formation potential of benzene is least but it is the most hazardous and carcinogenic species amongst BTEX. Thus, this scale is very useful for examining the relative importance of VOC compounds for their role in photochemical smog formation including production of ozone.

Role of Global Warming and Plant Signaling in BVOC Emissions

Plants emit a substantial amount of biogenic volatile organic compounds (BVOCs) into the atmosphere having significant effects on atmospheric chemistry, physics, and the organisms. In this chapter, important facts about BVOCs’ production mechanism, storage, and emissions due to various abiotic and biotic factors have been discussed. The role of BVOCs in defense system through plant signaling has also been discussed. The chapter continues with the discussions about the importance of BVOCs in the formation of tropospheric ozone and secondary organic aerosols and ultimately strengthens our understanding about global change research.