These 16 plant species were collected from the selected zones of the study area in 3 different seasons summer, monsoon and winter to evaluate the tolerance levels of the plant species to the air pollutants. Fully mature leaves were collected in morning hours from the selected trees, almost at the same height. For the evaluation of Air Pollution Tolerance Index (APTI), the fresh leaf samples were analyzed for leaf extract pH, leaf Relative Water Content, Total Chlorophyll Content and Ascorbic Acid by using standard procedures.
2.2 The experimental methods are
Relative water content
Total chlorophyll content
The leaf fresh weight was taken immediately upon getting to the laboratory. Samples were preserved in a refrigerator for other analyses.
2.2.1. Leaf extracts pH: 5 g of the fresh leaves were homogenized in 50 ml deionized water. This was then filtered and the pH of leaf extract determined after calibrating pH meter with buffer solution of pH 4 and pH 9.
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2.2.2. Relative leaf water content (RWC): Following the method described by Singh (1977), leaf RWC was determined and calculated with the formula:
RWC = [(FW -DW) / (TW -DW)] - 100
FW = Fresh weight, DW = dry weight, and TW = turbid weight.
Fresh weight was obtained by weighing the fresh leaves. The leaves were then immersed in water over night, blotted dry and then weighed to get the turgid weight. Next, the leaves were dried overnight in an oven at 70°C and reweighed to obtain the dry weight.
2.2.3. Total chlorophyll content (TCH): This was done according to the method described by Arnon (1949). 0.10 g of fresh leaves were blended and then extracted with 10 ml of 80% acetone and left for 15 min. The liquid portion was decanted into another text-tube and centrifuged at 2,500 rpm for 3 min. The supernatant was then collected and the absorbance was then taken at 645 nm and 663 nm using a spectrophotometer. Calculations were made using the formula below:
Chl a (mg/g) = [(12.7XDX663) - (2.69-DX645)] -ml acetone/mg leaf tissue
Chl b (mg/g) = [(22.9-DX645) - (4.68-DX663)] - ml acetone/mg leaf tissue
TCh (mg/g) = Chl a + Chl b,
Dx = Absorbance of the extract at the wavelength Xnm,
2.2.4. Ascorbic acid: The ascorbic acid content of leaf tissue was estimated by the method given by Sadasivam (2007). Fresh leave tissues of 2.5 g were homogenized in a pre-chilled mortar and pestle with 10 ml of 4% oxalic acid solution. The homogenate was centrifuged at 1800 rpm for 25 min. 10 ml of supernatant was titrated with DCPIP dye till pink color persists. The amount of ascorbic acid in the sample was calculated using the following formula:
Mg of Ascorbic acid in g sample = 0.5/V1 - V2/V - 100/W -100
Where, V = volume of leaf extract taken for titration, V1 = ml of dye used for standard ascorbic acid titration, V2 = ml of dye used for titration and W = weight of leaf material
2.3. Air Pollution Tolerance Index: The APTI was calculated by calculating the Ascorbic acid, Total Chlorophyll, pH and Relative Water Contents in leaves (Singh and Rao,1983).
The APTI was calculated by using the formula:
APTI = [A (T+P) + R]/10
Where, A = Ascorbic acid (mg/g dry wt.), P = pH of leaf extract, T = Total Chlorophyll content (mg/g dry wt.) and R = Relative Water Content of leaf tissue (%)
Ambient Ozone Monitoring:
The purpose of this study was to investigate ambient Ozone concentrations during summer, monsoon and winter seasons in the selected zones of the study area. This study further examined the influence of outdoor temperature on activity patterns and humidity on ambient Ozone exposure levels with Ozone ambient air monitor and controller.
Ozone Ambient air monitor and Controller: Model no-OZ-AIR SM 50
If we use the monitor for the first time or it has not been used for a long time, then it should be energized for more than 24 hours before it come into normal use. If we have placed in the direction of the outlet of the ozone monitor or in places where wind pass through, then the measurement of the ozone monitor will be incorrect.
In this situation, keep the ozone monitor in normal environment and energized for at least 24 hours, and then calibrate its zero point. Then the monitor is returned to normal use again. When the ozone measurements range overstep the maximum measurement, the ozone sensor must be resumed after a long time rest and then it will return to normal use again.
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Temperature measurement range is 0-500 C; humidity measurement range is 5-99% RH. Ozone measurement range is 10-1000 ppb and setting range is 40-1000 ppb. Its maximum measurement limited is 2000 ppb.
Turn On: Turn on the monitor by press power for 2 seconds. Temperature measurement displays on the right of upper line of LCD, the humidity measurement displays on the left of upper line of LCD. The preheating time of Ozone sensor displays on the below line and the time is set to 300 seconds (default). The preheating time can be changed in parameter setup. After it is counted down to 0, Ozone level will be displayed.
Press switch key to switch setting value between Ozone number is blinking, it indicates that the Ozone value can be set by and key. Increase or decrease 1 ppb each time by pressing and rapid increase or decrease by pressing key continually.
Setting O3 value: Simultaneously depress the switch key more than 5 seconds up to the symbol appearing on the LCD. Then the setting value is locked to avoid wrong operation.
Unlock: Under the locked mode, simultaneously depress up to disappear.
When DIP4 is set to OFF and the differential of Ozone setting also see Parameter Setup. The relay will turn on when O3 setting measurement <O3 setting with ON symbol appearing on the right of LCD. When O3 measurement > O3 setting, the relay will turn off with ON disappearing.
When DIP4 is set to ON:
The relay will turn on then O3 measurement > O3 setting with ON symbol appearing on the right of LCD. When O3 measurement < O3 setting, the relay will turn off with ON disappearing.
The scale bards on the right of LCD indicate the analog output. One scale bar indicated 1 VDC voltage output and five scale bards indicates 5 VDC voltage output.
Calibration of the zero of Ozone: After using the Ozone sensor for more than one year, the sensor needs to be calibrated again. Put the monitor into the space of zero Ozone and preheating it, press switch key for about 20 seconds until X10 symbol appearing on the right of Ozone number, then loosen switch key the monitor starts auto zero calibration. After 210 seconds until X10 symbol disappearing, it indicates the zero has no any calibration, it is still 0.
Cancel the zero calibration: Press switch key for about 20 seconds until X10 symbol appearing and then keep on press switch key for about 20 seconds until X10 symbol disappearing. It indicated the zero has no any calibration, it is still 0.
MOUNTING AND WIRING DIAGRAM:
Cut off power first. Simultaneously depress the 2 Clips on either of the sides of the monitor gently with nails or other unships tools, and then move off the face part.
Mount the monitor on the wall, 1.2 - 1.3 meters above the floor. Do not behind a door, in a corner, near diffuser, in direct sunlight and near any heat or steam sources. Do not mount like monitor in the direction of the outlet of the Ozone generator or in places where wind pass through, because the internal Ozone Sensor can be easily influenced by wind.
Mount the wall plate: Two dimensions available. Place the monitor against the wall at desired location; make sure wires can be drilled through the holes on the wall plate.
Connect wires to terminal strips and make sure wiring connection correct.
Fig-7: Ambient Ozone Monitor
Data from APPCB:
Other precursor gases like Nitrogen oxides, Carbon monoxide, Oxides of Nitrogen and Oxides of Sulphur and materiological data was collected from the Andhra Pradesh Pollution Control Board (APPCB) during 2010 to 2011.
The data generated during the study were subjected to the following statistical analyses such as: standard deviation, co-rrelation, t-test (comparison between groups), regression and regression equations were worked out to develop the relationship between the ozone concentration and yield parameters.
Standard deviation: The standard deviation was calculated according to the belo given formula:
C0-rrelation: C0-rrelation (which measures the closeness of the relationship between the two variables) was determined by positive/negative in the linear relation.
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