*<IP_ADDRESS>. Auto-combustion synthesis*

A redox-based combustion synthetic approach was applied to oxide thin films using acetylacetone or urea as a fuel and metal nitrates as oxidizers [55]. The self-energy-generating combustion chemistry provides a localized energy supply, eliminating the need for high, externally applied processing temperatures. Furthermore, the atomically local oxidizer supply can efficiently remove organic impurities without coke formation in combustion reactions with balanced redox chemistry. The semiconducting In2 O3 annealed at temperature as low as 200°C yielded TFTs with *μ* approaching 1.0 and 13.0 cm2 V−1 s−1 on SiO2 and Al2 O3 gate dielectrics, respectively.


*Edited by Andrew P. Bunger, John McLennan and Rob Jeffrey*

This book comprises the proceedings for the International Conference for Effective and Sustainable Hydraulic Fracturing (HF2013) which was held 20-22 May 2013 in Brisbane, Australia. The conference goal was to advance hydraulic fracturing technology that is effective in its purpose and sustainable in its impacts on communities and environments by bringing together hydraulic fracturing experts not only from the petroleum industry, but also from other application areas of hydraulic fracturing such as mining and geothermal energy production. Topics include hydraulic fracturing of naturally fractured formations, well completions and fracture initiation, induced seismicity, experimental investigations, and coupled modelling. Beyond this mix of traditional hydraulic fracturing research topics, this book includes papers on applications in mining and also on regulations, risk, and communities.

ISBN 978-953-51-1137-5

Effective and Sustainable Hydraulic Fracturing

Photo by sasacvetkovic33 / iStock


1. Introduction

Paddy cultivation plays a significant and vital role on rice production. Most of the global population depends on the 480 million tons of rice produced each year as the basis for their lives. While about 90% of the world's 160 million hectares of paddy fields are in Asian countries, mainly in monsoon regions, paddies are also seen in North America and Africa, even in dry regions where irrigation has reclaimed dry land for paddy fields.

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Rice, as one of the main staple for human being, is cultivated in various regions of the world from the wettest areas in the world to the driest deserts, with various conditions of natural environment including climate, topography, and soil conditions. For example, rice is grown in the area with more than 5000 mm of rain for one growing season, and with less, almost zero, of rainfall. The growing season average temperature of rice producing areas varies from more than 30C to less than 15C. Rice cultivation is observed in a higher mountain region with more than 2500 m above the sea level, as well as in ocean coast even in sea level region [1].

Oxford Living Dictionary as "A field where rice is grown" [8], and of Merriam-Webster as "wet land in which rice is grown" [9], while it also show the meaning as "Rice before threshing or in

Paddy Fields as Artificial and Temporal Wetland http://dx.doi.org/10.5772/intechopen.80581 145

Since rice is usually grown in level basin flooded with water throughout most of the growing season, "paddy field" generally means "a field flooded with water for growing rice," and the definitions of "paddy field" in most of the current dictionaries include words of "rice" and

In Japan, the English words "paddy field" is translated to the Japanese word "suiden," while there this word "suiden" is used for flooded farm land, which distinguishes "flooded field" from "upland field" or "hatake" in Japanese. The upland field is not flooded and cultivated for normal crops like vegetables and flowers. Accordingly, in Japan, it is expressed that some aquatic crops like lotus and tatami are cultivated in "paddy fields." This Japanese case is recognized as an exceptional case. In this chapter, "paddy field" is to be used basically as "a

As mentioned below, actually, in considerable area in the world, rice is produced in fields without flooding. Then, some parts of paddy fields of the world are not identified as the

Generally, rice is a major food crop for the people in the world. Especially in the Asia region, rice is a staple food for about 2.4 billion people, and there the 90% of the world's rice is

As summarized above, rice production and paddy fields are developed in a wide range of environments even in the arid region of the world and during the dry season. The paddy fields

The paddy fields or the environments of the rice production are classified usually based on the hydrological characteristics, since they are most essential condition to the production scheme. The most popular classification includes: (1) irrigated lowland, (2) rain-fed lowland, (3) flood

The first category "irrigated" paddy fields distributed in lowland are the area, where rice is grown in fields surrounded by ridges. Its water condition is managed by farmers, generally maintaining water depth as 5–10 cm. It covers about 90 million ha, as almost half of the world

The second category "rain-fed lowland" or "lowland rain-fed" is a field, where rice is also grown in fields with bunds, while they are flooded with rainwater for some period of a growing season. It covers about 50 million ha. There, water is flooded naturally by rain water, not fully controlled by the man-made irrigation system. These two types of paddy fields are usually predominantly puddled, and after it, rice seedlings are transplanted. These two types of paddy fields produce 75 and 19% of the world's rice production, as almost 95% of rice is

in dry areas sometime show very high and stable yields with much solar radiation.

paddy area. The major portion of this irrigated area is in the Asian region.

the husk."

"water" or "flood," as introduced above.

field planted with rice."

"wetland" with water submergence.

produced and consumed [10].

prone, and (4) upland [1].

2.2. Outline of paddy field in the world

Most of the fields, where rice is produced, are flooded, or submerged by water, naturally or artificially during rice production period. To keep paddy fields submerged artificially, some infrastructures like reservoirs or ponds, intake and diversion works and canals are constructed. The infrastructures, after construction, are operated and maintained generally by local society, usually with some supports of the government. Rice is produced mostly in the fields with artificial water management with irrigation and drainage system, than in naturally flooded fields.

The stable water supply and continuous ponding in the fields are the base for much rice production. On the other hand, as mentioned above, they need hydraulic structures and the appropriate operation and management of the structures. The artificial ponding with stable and much water supply mostly results in better rice growth, while it might change the local environment both positively and negatively. In the case that the impacts of ponding and irrigation on the environment are positive, they are to be recognized as their "multi-functions." Recently, much water use for rice cultivation and necessity of water saving in paddy irrigation have been discussed often, and simultaneously the role of flooding in paddy fields has been highlighted in terms of environmental conservation (for example, see [2–4]).

On the other hand, since rice production area has been reducing in some developed countries and regions with long history of rice cultivation, like Japan, Taiwan, and Korea, the role of rice fields and their flooding is to be reevaluated. In this chapter, the irrigated fields for rice are recognized as artificial and temporal wetland and reviewed comprehensively, focusing mainly on their role for local hydrological environment.


**Conflict of interest**

*Teacher Education in the 21st Century - Emerging Skills for a Changing World*

to compile as part of the four-month course. A text analysis carried out using a content analysis software tool showed that the concept of Green Pedagogy was a minor rather than a major theme for the ProfESus participants [27]. This indicated that there was more work to be done in conveying the practice of Green Pedagogy more efficiently in English and that a four-month course is insufficient on its own to effect sustainable change in didactics and education. A continuous peer-reflection process might help to implement Green Pedagogy enduringly into a wider field of

Green Pedagogy is useful amidst the plethora of materials emerging from the UN Sustainability Goals initiative to help teachers include more sustainable approaches insofar as it gives clear guidelines at the lesson planning level. This pedagogical approach can be used at all levels of schooling and beyond in higher education. The 6-step process is also useful as a way of approaching consultancy briefs where the aim is to include a sustainability perspective. The second main advantage of implementing Green Pedagogy is that it can be used to lead educators to target both vocational (or subject-specific) competencies and sustainability competencies simultaneously. This means that academic or vocational skills are acquired through a sustainability perspective and that sustainability does not need to appear as a distinct topic in the school timetable since it can be infused across large parts of the existing curriculum. The Green Pedagogy guidelines can be justified by reference to established theoretical frameworks such as conceptual change. Learners can be overwhelmed by the intractable problems of the world and Green Pedagogy offers a way of countering this. An important aspect of Green Pedagogy is to allow learners to uncover their own values as a result of what they have been exposed to through the Green Pedagogy approach rather than imposing teacher values on learners. The approach encourages learners to widen their consideration of the range of relevant stakeholders affected by the problem as a way of highlighting the sustainability aspect of any problem. Thus, a systematic implementation of Green Pedagogy across an educational institution will lead to its learners understanding much more about, for example, the institution's suppliers, its treatment of waste and its local impact after first examining the chosen problem in a national or global context. The stakeholder understanding will also include the learners' own context at home and include the effect of the actions of family members. An important part of Green Pedagogy is to end learning activities with an actionable vision that learners can act upon rather than leaving the classroom feeling that all is hopeless. It is easily combined with other recommended sustainability education approaches and provides a useful checklist to ensure efficacy. Thus, Green Pedagogy is a useful addition to the sustainability education lexicon if some of the German origins are thoroughly explained, to ensure that Green Pedagogy transitions effectively from the Germanspeaking sphere to the English context. It is a pedagogy that can support transformative learning through the exploration and clarification of learners' own values.

**228**

**Acknowledgements**

by-sa/3.0>, via Wikimedia Commons

European Union.

The ProfESus project was part-funded by an Erasmus+ grant by the

**Figure 1**. KTucker, CC BY-SA 3.0 <https://creativecommons.org/licenses/

learning.

**14. Conclusions**

The authors declare no conflict of interest.


**4. Background aerosol optical and physical properties over Thar desert**

## **4.1. Aerosol optical depth**

The seasonal variation of AOD spectrum at the hilltop station over western India is shown in Figure 4. Vertical lines represent ±1*σ* variation about the mean AOD. The solid lines are the OPAC model fitted AOD spectrum and the shaded regions indicate the variation of simulated AOD within that season. At all wavelengths, AODs are maximum during premonsoon followed by postmonsoon and monsoon and are minimum during winter. At 0.5 *μ*m, the AODs are 0.20±0.08, 0.18±0.04, 0.10±0.02, and 0.08±0.03 during premonsoon, postmonsoon, monsoon and winter, respectively. The reasons could be as follows. Firstly, there is a large variation of boundary layer height. In an earlier research work carried out over a tropical Indian station, Gadanki (13.5*o*N, 79.2*o*E), Krishnan & Kunhikrishnan [37] studied the annual boundary layer height variation and observed a minimum during winter and maximum during premonsoon. In the present study, during winter the boundary layer height is lower than the observation altitude and hence the observation site is in the free troposphere region. As a result, AOD is minimum during this season. During premonsoon the observation site is within the boundary layer and hence AOD increases. In addition, there is significant amount of dust transported from arid region which results in maximum AOD. On the other hand, during monsoon though the boundary layer height is significantly high, AOD is low due to wash out of aerosols from the atmosphere by the heavy monsoonal rain events. Monsoon rain has a major role to wash out the aerosol loading from the atmosphere causing significant decrease of AOD. A case study over tropical Indian station reported about 64% decrease of AOD due to heavy rain [69]. In the present study, there is no significant decrease of AOD during monsoon. This is because of the presence of a very stable aerosol layer of about 1.5

**Figure 3.** Picture of land surface over western India during premonsoon (top) and potmonsoon (middle) seasons, obtained from MODIS-Terra satellite. Dark black, gray and green colors represent oceanic surface, arid bare land, forest regions, respectively. (Bottom) Monthly variation of surface reflectance at 1.64 *μ*m wavelength during 2007 and the vertical bars represents ±1*σ* deviation about the monthly mean. Note that the surface reflectance increases by 70% over study area during premonsoon.

Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 91

90 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 11 Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 91

10 Will-be-set-by-IN-TECH

during postmonsoon due to green vegetation born during monsoon rain. As a result, surface

In the present study, MODIS derived surface reflectance data over Mt. Abu is used in the estimations of radiative forcing. It is obtained from Nadir BRDF-Adjusted Reflectance 16-Day L3 Global 0.5 km SIN Grid product which is derived at the mean solar zenith angle of Terra overpasses for every successive 16-day period, calculating surface reflectance as if every pixel in the grid was viewed from nadir direction. Surface reflectance data available in seven wavelength bands of MODIS centered around 0.47, 0.56, 0.65, 0.86, 1.24, 1.64 and 2.13 *μ*m are used to reproduce the spectral dependence of surface reflectances for the entire SW range using a combination of three different surface types, namely, vegetation, sand and water. The monthly variation of surface reflectance at 1.64 *μ*m during 2007 is shown in Figure 3c. Vertical lines in this Figure represent ±1*σ* variation about the monthly mean values. Average surface reflectance is found to be high at about 0.35 during premonsoon (Apr-May) and low at about 0.20 during postmonsoon (Sep-Nov) and winter (Dec-Feb). Space-borne observations show that the land over western India increases its brightness by about 75% during premonsoon season. This could be due to bare surface and deposited dust that is transported from arid region. Model simulations to fit the surface reflectance combining the three surfaces suggest that during premonsoon sand surface contributes a maximum of about 70% and during postmonsoon and winter it contributes a minimum of about 20% while vegetation surface contributes 15% and 60%, respectively. These varying land properties are also considered in

**4. Background aerosol optical and physical properties over Thar desert**

The seasonal variation of AOD spectrum at the hilltop station over western India is shown in Figure 4. Vertical lines represent ±1*σ* variation about the mean AOD. The solid lines are the OPAC model fitted AOD spectrum and the shaded regions indicate the variation of simulated AOD within that season. At all wavelengths, AODs are maximum during premonsoon followed by postmonsoon and monsoon and are minimum during winter. At 0.5 *μ*m, the AODs are 0.20±0.08, 0.18±0.04, 0.10±0.02, and 0.08±0.03 during premonsoon, postmonsoon, monsoon and winter, respectively. The reasons could be as follows. Firstly, there is a large variation of boundary layer height. In an earlier research work carried out over a tropical Indian station, Gadanki (13.5*o*N, 79.2*o*E), Krishnan & Kunhikrishnan [37] studied the annual boundary layer height variation and observed a minimum during winter and maximum during premonsoon. In the present study, during winter the boundary layer height is lower than the observation altitude and hence the observation site is in the free troposphere region. As a result, AOD is minimum during this season. During premonsoon the observation site is within the boundary layer and hence AOD increases. In addition, there is significant amount of dust transported from arid region which results in maximum AOD. On the other hand, during monsoon though the boundary layer height is significantly high, AOD is low due to wash out of aerosols from the atmosphere by the heavy monsoonal rain events. Monsoon rain has a major role to wash out the aerosol loading from the atmosphere causing significant decrease of AOD. A case study over tropical Indian station reported about 64% decrease of AOD due to heavy rain [69]. In the present study, there is no significant decrease of AOD during monsoon. This is because of the presence of a very stable aerosol layer of about 1.5

reflectance is maximum during premonsoon and minimum during postmonsoon.

the radiative forcing calculations.

**4.1. Aerosol optical depth**

**Figure 3.** Picture of land surface over western India during premonsoon (top) and potmonsoon (middle) seasons, obtained from MODIS-Terra satellite. Dark black, gray and green colors represent oceanic surface, arid bare land, forest regions, respectively. (Bottom) Monthly variation of surface reflectance at 1.64 *μ*m wavelength during 2007 and the vertical bars represents ±1*σ* deviation about the monthly mean. Note that the surface reflectance increases by 70% over study area during premonsoon.

#### 12 Will-be-set-by-IN-TECH 92 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 13

km thickness over the inversion layer during monsoon in the western India, as reported by Ganguly et al. [19].

The spectral dependence of AOD is parameterized through Ångstr*o*¨m exponent (*α*) which is the slope of the logarithm of AOD versus the logarithm of wavelength (in micron) and provides the basic information about the columnar particle size distribution [66]. *α* is higher for relatively higher number of smaller particles and as the number of bigger particles increases *α* decreases. It can even reduce to ∼0 for very large number of coarse-mode soil particles [51, 77, 81, etc]. In the present study, *α* is obtained from Microtops measured AOD for the entire wavelength (0.380 - 1.020 *μ*m) and is given in Figure 4 along with the variation in the parenthesis. It varies from 0.2 to 0.6. During monsoon *α* is minimum at 0.2±0.15 indicating dominance of bigger aerosols. It is due to the presence of bigger water soluble aerosols which increase in size due to accumulation and coagulation processes in high relative humidity conditions. During premonsoon also, when RH is low and the atmosphere is dry and warm, *α* is low at about 0.3±0.25 indicating the dominance of bigger aerosols. These are the soil born dust aerosols produced by the frequently occurring dust storms in the Thar desert and transported to other parts of India [17, 55] including Mt. Abu. *α* is found to be maximum at about 0.6±0.01 during postmonsoon indicating dominance of smaller aerosols. This is probably due to dominance of fine seasalt aerosols transported from Arabian Sea [19, 64] . During winter also *α* is found to be high showing dominance of smaller aerosols which could be due to anthropogenic aerosols coming from burning tree branches and dry leaves by the poor villagers living in the surrounding hill areas to keep themselves warm during cold mornings and evenings.

## **4.2. Aerosol mass concentration**

Aerosol mass concentration measured separately in ten different sizes by Quartz Crystal Microbalance (QCM) cascade impactor has been classified into three different categories, viz., nucleation (radius*<*0.1 *μ*m), accumulation (0.1*μ*m≤radius≥1.0 *μ*m) and coarse (radius*>*1.0 *μ*m) mode particles. Nucleation mode aerosols represent total aerosols collected in stages 9-10, accumulation mode aerosols are the total aerosols in stages 5-8 and coarse mode aerosols are the total aerosols collected in stages 2-4. Aerosols collected in stage 1 are not considered in the calculations because all aerosols whose radius is greater than 12.5 *μ*m are collected in this stage and thus, there is no definite aerosol radius representing this stage.

**Figure 4.** Seasonal variation of observed AOD spectrum at Mt. Abu. Vertical bars represent ±1*σ* variation about the mean. Solid line is the OPAC model derived AOD spectrum and the shaded regions are the variation in the simulated AOD. Ångstr*o*¨m exponent (*α*) is also given along with the standard

enhances the nucleation mode aerosols which explains the maximum mass of 6.4±1.1 *μ*g.m−3 observed during this season. During winter the nucleation mass concentration decreased to 3.2±0.1 *μ*g.m−3 as the boundary layer height decreased and the measurement site was in free troposphere. The nucleation aerosol mass was 2.9±1.8 and 3.6±0.7 *μ*g.m−3 during premonsoon and monsoon, respectively. During premonsoon, the boundary layer height was maximum which gives more room for these fine aerosols to dilute and high temperature with low RH are not favorable for gas-to-particle conversion processes. In addition, strong wind also helps in removing the aerosols from the measurement site during this season and makes mass of the nucleation mode aerosols minimum. Monsoon also experiences high boundary layer height and strong wind condition, however, nucleation mode aerosols are significant compared to premonsoon. This could be due to the transport of seasalt coming from Arabian

Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 93

The seasonal variation observed in the accumulation aerosols is similar to the nucleation aerosols. The accumulation aerosol mass concentration was minimum at 8.4±2.8 *μ*g.m−3 during premonsoon and maximum at 12.6±0.6 *μ*g.m−3 during postmonsoon followed by monsoon (10.0±1.0 *μ*g.m−3) and winter (9.6±1.6 *μ*g.m−3). Accumulation aerosols are mainly produced by the condensation growth and coagulation of nucleation aerosols. During

deviations in parenthesis.

Sea.

Figure 5 shows the seasonal variation of aerosol mass concentration (*μ*g.m−3) of all three modes, viz., nucleation, accumulation and coarse modes at the hill top region, Mt. Abu from January 2006 to December 2007. Total aerosol mass concentration observed was minimum at 16.5±1.5 *μ*g.m−3 during winter and maximum at 25.8±2.7 *μ*g.m−3 during postmonsoon followed by premonsoon (19.9±5.6 *μ*g.m−3) and monsoon (16.7±6.0 *μ*g.m−3). This variation is similar to that observed in columnar AOD at Mt. Abu. The accumulation aerosol mass was contributing maximum to the total aerosol mass during all seasons and the coarse mode aerosol mass was contributing equivalently only during premonsoon. This is due to large transportation of dust aerosols from Thar desert during this season that enhanced the coarse mode aerosol mass.

In general, nucleation aerosols contribute least to the total aerosol mass concentration. This contribution was maximum during postmonsoon when the wind speed was almost calm and RH was relatively high. This atmospheric condition helps in gas-to-particle conversion and 12 Will-be-set-by-IN-TECH

km thickness over the inversion layer during monsoon in the western India, as reported by

The spectral dependence of AOD is parameterized through Ångstr*o*¨m exponent (*α*) which is the slope of the logarithm of AOD versus the logarithm of wavelength (in micron) and provides the basic information about the columnar particle size distribution [66]. *α* is higher for relatively higher number of smaller particles and as the number of bigger particles increases *α* decreases. It can even reduce to ∼0 for very large number of coarse-mode soil particles [51, 77, 81, etc]. In the present study, *α* is obtained from Microtops measured AOD for the entire wavelength (0.380 - 1.020 *μ*m) and is given in Figure 4 along with the variation in the parenthesis. It varies from 0.2 to 0.6. During monsoon *α* is minimum at 0.2±0.15 indicating dominance of bigger aerosols. It is due to the presence of bigger water soluble aerosols which increase in size due to accumulation and coagulation processes in high relative humidity conditions. During premonsoon also, when RH is low and the atmosphere is dry and warm, *α* is low at about 0.3±0.25 indicating the dominance of bigger aerosols. These are the soil born dust aerosols produced by the frequently occurring dust storms in the Thar desert and transported to other parts of India [17, 55] including Mt. Abu. *α* is found to be maximum at about 0.6±0.01 during postmonsoon indicating dominance of smaller aerosols. This is probably due to dominance of fine seasalt aerosols transported from Arabian Sea [19, 64] . During winter also *α* is found to be high showing dominance of smaller aerosols which could be due to anthropogenic aerosols coming from burning tree branches and dry leaves by the poor villagers living in the surrounding hill areas to keep themselves warm during cold

Aerosol mass concentration measured separately in ten different sizes by Quartz Crystal Microbalance (QCM) cascade impactor has been classified into three different categories, viz., nucleation (radius*<*0.1 *μ*m), accumulation (0.1*μ*m≤radius≥1.0 *μ*m) and coarse (radius*>*1.0 *μ*m) mode particles. Nucleation mode aerosols represent total aerosols collected in stages 9-10, accumulation mode aerosols are the total aerosols in stages 5-8 and coarse mode aerosols are the total aerosols collected in stages 2-4. Aerosols collected in stage 1 are not considered in the calculations because all aerosols whose radius is greater than 12.5 *μ*m are collected in this

Figure 5 shows the seasonal variation of aerosol mass concentration (*μ*g.m−3) of all three modes, viz., nucleation, accumulation and coarse modes at the hill top region, Mt. Abu from January 2006 to December 2007. Total aerosol mass concentration observed was minimum at 16.5±1.5 *μ*g.m−3 during winter and maximum at 25.8±2.7 *μ*g.m−3 during postmonsoon followed by premonsoon (19.9±5.6 *μ*g.m−3) and monsoon (16.7±6.0 *μ*g.m−3). This variation is similar to that observed in columnar AOD at Mt. Abu. The accumulation aerosol mass was contributing maximum to the total aerosol mass during all seasons and the coarse mode aerosol mass was contributing equivalently only during premonsoon. This is due to large transportation of dust aerosols from Thar desert during this season that enhanced the coarse

In general, nucleation aerosols contribute least to the total aerosol mass concentration. This contribution was maximum during postmonsoon when the wind speed was almost calm and RH was relatively high. This atmospheric condition helps in gas-to-particle conversion and

stage and thus, there is no definite aerosol radius representing this stage.

Ganguly et al. [19].

mornings and evenings.

mode aerosol mass.

**4.2. Aerosol mass concentration**

**Figure 4.** Seasonal variation of observed AOD spectrum at Mt. Abu. Vertical bars represent ±1*σ* variation about the mean. Solid line is the OPAC model derived AOD spectrum and the shaded regions are the variation in the simulated AOD. Ångstr*o*¨m exponent (*α*) is also given along with the standard deviations in parenthesis.

enhances the nucleation mode aerosols which explains the maximum mass of 6.4±1.1 *μ*g.m−3 observed during this season. During winter the nucleation mass concentration decreased to 3.2±0.1 *μ*g.m−3 as the boundary layer height decreased and the measurement site was in free troposphere. The nucleation aerosol mass was 2.9±1.8 and 3.6±0.7 *μ*g.m−3 during premonsoon and monsoon, respectively. During premonsoon, the boundary layer height was maximum which gives more room for these fine aerosols to dilute and high temperature with low RH are not favorable for gas-to-particle conversion processes. In addition, strong wind also helps in removing the aerosols from the measurement site during this season and makes mass of the nucleation mode aerosols minimum. Monsoon also experiences high boundary layer height and strong wind condition, however, nucleation mode aerosols are significant compared to premonsoon. This could be due to the transport of seasalt coming from Arabian Sea.

The seasonal variation observed in the accumulation aerosols is similar to the nucleation aerosols. The accumulation aerosol mass concentration was minimum at 8.4±2.8 *μ*g.m−3 during premonsoon and maximum at 12.6±0.6 *μ*g.m−3 during postmonsoon followed by monsoon (10.0±1.0 *μ*g.m−3) and winter (9.6±1.6 *μ*g.m−3). Accumulation aerosols are mainly produced by the condensation growth and coagulation of nucleation aerosols. During

the typical aerosol size distributions for the four seasons. The vertical bars represent ±1*σ* variation about the monthly mean number concentration of different sizes of aerosols. In all seasons, the size distribution showed tri-modal distribution and each mode could be fitted

Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 95

exp ⎡ ⎣− log2

where *N* is the number concentration (cm−3), *σm* is the width of the distribution and *rm* is the mode radius for a particular mode. The three modal parameters for all the seasons are given in Table 1. At Mt. Abu the number concentrations (*N*) of nucleation and accumulation modes are lower by an order of magnitude than that at other urban region in western India, Ahmedabad while for coarse mode it is comparable [19]. Since Mt. Abu is far from anthropogenic activity, the anthropogenically influenced modes (nucleation and accumulation) have smaller number concentrations. However, the proximity to Thar desert and similarity of the surface conditions of Mt. Abu make the coarse mode number concentrations comparable. The radii of nucleation mode lie in the range 0.018-0.020 *μ*m and number concentration for this mode is found to be maximum during postmonsoon and minimum during premonsoon and monsoon. Similarly the radii for corresponding accumulation and coarse modes lie in the range of 0.12-0.19 *μ*m

Season *N* r*m σ N* r*m σ N* r*m σ*

Winter 12000 0.019 2.0 18 0.14 2.0 0.02 1.4 1.9 Premonsoon 10000 0.018 1.9 22 0.19 1.8 0.01 2.2 1.8 Monsoon 15000 0.018 1.9 50 0.13 1.9 0.01 1.7 1.8 Postmonsoon 17000 0.020 1.9 60 0.12 1.9 0.08 1.1 1.8 **Table 1.** Average values of size distribution parameters obtained by fitting lognormal curves to the

Accumulation aerosols are mainly produced by the condensation growth and coagulation of nucleation aerosols. During winter accumulation mode aerosols number concentration (*N*) was minimum at 18 cm−3. During premonsoon, the anthropogenic activities were maximum at Mt. Abu which increased *N* of accumulation mode to 22 cm−3. During monsoon, it further increased to 50 cm−3. It is due to the wind coming from Arabian sea (Figure 2) that carried large amount of sea salt and enriched the sea salt aerosols at the hill top region [64]. During high RH conditions these sea salt aerosols belong to the accumulation mode. Later during postmonsoon, wind was south-easterly and the transported sea salt reduced. However, burning of biomass like garbage and fallen leaves increased and hence, BC particle concentration was enhanced. Therefore, high production, shallow boundary layer height and low wind speed made the accumulation mode aerosol number concentration reach a

During premonsoon, there is large transportation of mineral dust aerosols from Thar Desert which enhanced the abundance of coarse mode aerosols at the hill top area. The coarse mode radius was maximum at 2.2 *μ*m. During monsoon, rain washes out these dust aerosols from the atmosphere and reduces their number and mode radius. However, the abundance

� *r rm* �

2

⎤

⎦ (2)

2 (log *σm*)

Nucleation Accumulation Coarse

cm−3 *μ*m *μ*m cm−3 *μ*m *μ*m cm−3 *μ*m *μ*m

using using three lognormal modes of the following form.

*dn* (*r*)

and 1.1-2.1 *μ*m, respectively.

measured aerosol number distribution over Mt. Abu

maximum at 60 cm−3 during this season.

*dr* = *N*

√2*π* log *σm*

**Figure 5.** Seasonal variation of aerosol mass concentrations in nucleation (radius < 0.1 micron), accumulation (0.1≥radius≤1.0 micron) and coarse (radius >1.0 micron) modes. The vertical bars represent ±1*σ* variation about the mean.

premonsoon these processes are slowed down due to low RH and hence the low accumulation aerosol mass. During monsoon seasalt aerosols are transported from the Arabian sea and high RH maintains the accumulation mode aerosols, increasing the mass concentration. During postmonsoon, minimum wind speed results in further increase resulting in the observed maximum. And during winter it is minimum as the the measurement site is in the free troposphere.

The coarse mode aerosols show a slightly different seasonal behaviour at Mt. Abu. During premonsoon, they mainly consist of dust aerosols transported from Thar desert and the mass concentration is maximum at 8.6±0.4 *μ*g.m−3. It is minimum at 3.1±0.5 *μ*g.m−3 during monsoon due to wash out of the dust aerosols by heavy rains. During postmonsoon, the coarse aerosol mass concentration was slightly enhanced to 6.8±1.0 *μ*g.m−3 as the accumulation aerosols, which mainly consist of seasalt particles, swell up by absorbing water vapor at high RH conditions and become coarse mode particles. During winter, their mass concentration becomes 3.6±0.6 *μ*g.m−3 when low boundary layer height helps to keep them low at the hill-top region.

### **4.3. Aerosol number concentration**

Aerosol number concentration is also obtained from the observed aerosol mass concentration from QCM observations for the hilltop area using appropriate mass density valid for semi-arid background atmosphere and prevailing relative humidity conditions [13, 26]. Figure 6 shows the typical aerosol size distributions for the four seasons. The vertical bars represent ±1*σ* variation about the monthly mean number concentration of different sizes of aerosols. In all seasons, the size distribution showed tri-modal distribution and each mode could be fitted using using three lognormal modes of the following form.

14 Will-be-set-by-IN-TECH

**Figure 5.** Seasonal variation of aerosol mass concentrations in nucleation (radius < 0.1 micron), accumulation (0.1≥radius≤1.0 micron) and coarse (radius >1.0 micron) modes. The vertical bars

premonsoon these processes are slowed down due to low RH and hence the low accumulation aerosol mass. During monsoon seasalt aerosols are transported from the Arabian sea and high RH maintains the accumulation mode aerosols, increasing the mass concentration. During postmonsoon, minimum wind speed results in further increase resulting in the observed maximum. And during winter it is minimum as the the measurement site is in the free

The coarse mode aerosols show a slightly different seasonal behaviour at Mt. Abu. During premonsoon, they mainly consist of dust aerosols transported from Thar desert and the mass concentration is maximum at 8.6±0.4 *μ*g.m−3. It is minimum at 3.1±0.5 *μ*g.m−3 during monsoon due to wash out of the dust aerosols by heavy rains. During postmonsoon, the coarse aerosol mass concentration was slightly enhanced to 6.8±1.0 *μ*g.m−3 as the accumulation aerosols, which mainly consist of seasalt particles, swell up by absorbing water vapor at high RH conditions and become coarse mode particles. During winter, their mass concentration becomes 3.6±0.6 *μ*g.m−3 when low boundary layer height helps to keep them

Aerosol number concentration is also obtained from the observed aerosol mass concentration from QCM observations for the hilltop area using appropriate mass density valid for semi-arid background atmosphere and prevailing relative humidity conditions [13, 26]. Figure 6 shows

represent ±1*σ* variation about the mean.

troposphere.

low at the hill-top region.

**4.3. Aerosol number concentration**

$$\frac{dn\,(r)}{dr} = \frac{N}{\sqrt{2\pi}\log\sigma\_m} \exp\left[-\frac{\log^2\left(\frac{r}{r\_m}\right)}{2\left(\log\sigma\_m\right)^2}\right] \tag{2}$$

where *N* is the number concentration (cm−3), *σm* is the width of the distribution and *rm* is the mode radius for a particular mode. The three modal parameters for all the seasons are given in Table 1. At Mt. Abu the number concentrations (*N*) of nucleation and accumulation modes are lower by an order of magnitude than that at other urban region in western India, Ahmedabad while for coarse mode it is comparable [19]. Since Mt. Abu is far from anthropogenic activity, the anthropogenically influenced modes (nucleation and accumulation) have smaller number concentrations. However, the proximity to Thar desert and similarity of the surface conditions of Mt. Abu make the coarse mode number concentrations comparable. The radii of nucleation mode lie in the range 0.018-0.020 *μ*m and number concentration for this mode is found to be maximum during postmonsoon and minimum during premonsoon and monsoon. Similarly the radii for corresponding accumulation and coarse modes lie in the range of 0.12-0.19 *μ*m and 1.1-2.1 *μ*m, respectively.

**Table 1.** Average values of size distribution parameters obtained by fitting lognormal curves to the measured aerosol number distribution over Mt. Abu

Accumulation aerosols are mainly produced by the condensation growth and coagulation of nucleation aerosols. During winter accumulation mode aerosols number concentration (*N*) was minimum at 18 cm−3. During premonsoon, the anthropogenic activities were maximum at Mt. Abu which increased *N* of accumulation mode to 22 cm−3. During monsoon, it further increased to 50 cm−3. It is due to the wind coming from Arabian sea (Figure 2) that carried large amount of sea salt and enriched the sea salt aerosols at the hill top region [64]. During high RH conditions these sea salt aerosols belong to the accumulation mode. Later during postmonsoon, wind was south-easterly and the transported sea salt reduced. However, burning of biomass like garbage and fallen leaves increased and hence, BC particle concentration was enhanced. Therefore, high production, shallow boundary layer height and low wind speed made the accumulation mode aerosol number concentration reach a maximum at 60 cm−3 during this season.

During premonsoon, there is large transportation of mineral dust aerosols from Thar Desert which enhanced the abundance of coarse mode aerosols at the hill top area. The coarse mode radius was maximum at 2.2 *μ*m. During monsoon, rain washes out these dust aerosols from the atmosphere and reduces their number and mode radius. However, the abundance

after CO2 and has a larger impact on direct radiative forcing than that of methane. As a result, in populated countries like China and India, the large production of BC aerosols has a large impact on the hydrological cycle and precipitation pattern [46, 61, 71]. In India the fraction of BC production from fossil fuel burning, open burning and biofuel combustion to the global emission is significantly large and hence, it is necessary to estimate radiative impact

Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 97

**Figure 7.** Diurnal variation of BC mass concentration during each month in 2007. White region indicates

In recent years, global climate has received considerable attention due to increase in the percentage contribution of anthropogenic aerosols on the Earth's radiation budget [23]. BC particles exist mainly in the accumulation mode and can be transported over long distances [12] from source regions to far off pristine environment and perturb the climate of the latter, like that of Mt. Abu. The diurnal variation of BC mass concentration during different months over Mt. Abu is shown in Figure 7. Observations were not possible in July and August due to heavy rain. Minimum BC concentration was observed during monsoon (0.428±0.128 *μ*g.m−3) and maximum was observed during premonsoon (0.665±0.478 *μ*g.m−3) followed by winter (0.608±0.246 *μ*g.m−3) and postmonsoon (0.620±0.158 *μ*g.m−3). The annual mean BC mass concentration was 0.580±0.104 *μ*g.m−3. At Mt. Abu the BC concentration is an order of magnitude less than that at any other urban region in India. BC during April is found to be as high as 1.00±0.170 *μ*g.m−3 which is a factor of 2 higher than the previous month. Backtrajectory analysis indicates wind coming from IGP which increases the BC concentration. In another study at a high altitude station, Nainital (29.4*o*N, 79.5*o*E, 1950m

no data during Jul-Aug due to heavy monsoonal rain.

of different kinds of BC not only on global scale but also in the regional scale.

**Figure 6.** Seasonal variation of aerosol number distribution. Vertical bars represent ±1*σ* variation about the mean. The solid lines are the best-fitted curves representing nucleation, accumulation and coarse modes.

of coarse aerosols is found to be maximum with minimum mode radius of about 1.1 *μ*m during postmonsoon which indicates the transfer of aerosols from accumulation mode due to hygroscopic and coagulation growth of particles at high RH conditions.

### **4.4. Black carbon mass concentration**

Black carbon (BC) produced due to incomplete combustion of carbon-based fuels [3, 31, 53, 86, etc] is the most efficient light absorbing aerosol component in the atmosphere. BC has major contribution to alter the radiative balance by absorbing the solar radiation in the visible spectrum. As a result, it cools the surface and warms the atmosphere [24, 38]. A recent study of BC contribution to radiative forcing by Jacobson [31] showed that BC has a great contribution towards global warming and is the second most important component of global warming after CO2 and has a larger impact on direct radiative forcing than that of methane. As a result, in populated countries like China and India, the large production of BC aerosols has a large impact on the hydrological cycle and precipitation pattern [46, 61, 71]. In India the fraction of BC production from fossil fuel burning, open burning and biofuel combustion to the global emission is significantly large and hence, it is necessary to estimate radiative impact of different kinds of BC not only on global scale but also in the regional scale.

16 Will-be-set-by-IN-TECH

**Figure 6.** Seasonal variation of aerosol number distribution. Vertical bars represent ±1*σ* variation about the mean. The solid lines are the best-fitted curves representing nucleation, accumulation and coarse

of coarse aerosols is found to be maximum with minimum mode radius of about 1.1 *μ*m during postmonsoon which indicates the transfer of aerosols from accumulation mode due

Black carbon (BC) produced due to incomplete combustion of carbon-based fuels [3, 31, 53, 86, etc] is the most efficient light absorbing aerosol component in the atmosphere. BC has major contribution to alter the radiative balance by absorbing the solar radiation in the visible spectrum. As a result, it cools the surface and warms the atmosphere [24, 38]. A recent study of BC contribution to radiative forcing by Jacobson [31] showed that BC has a great contribution towards global warming and is the second most important component of global warming

to hygroscopic and coagulation growth of particles at high RH conditions.

**4.4. Black carbon mass concentration**

modes.

**Figure 7.** Diurnal variation of BC mass concentration during each month in 2007. White region indicates no data during Jul-Aug due to heavy monsoonal rain.

In recent years, global climate has received considerable attention due to increase in the percentage contribution of anthropogenic aerosols on the Earth's radiation budget [23]. BC particles exist mainly in the accumulation mode and can be transported over long distances [12] from source regions to far off pristine environment and perturb the climate of the latter, like that of Mt. Abu. The diurnal variation of BC mass concentration during different months over Mt. Abu is shown in Figure 7. Observations were not possible in July and August due to heavy rain. Minimum BC concentration was observed during monsoon (0.428±0.128 *μ*g.m−3) and maximum was observed during premonsoon (0.665±0.478 *μ*g.m−3) followed by winter (0.608±0.246 *μ*g.m−3) and postmonsoon (0.620±0.158 *μ*g.m−3). The annual mean BC mass concentration was 0.580±0.104 *μ*g.m−3. At Mt. Abu the BC concentration is an order of magnitude less than that at any other urban region in India. BC during April is found to be as high as 1.00±0.170 *μ*g.m−3 which is a factor of 2 higher than the previous month. Backtrajectory analysis indicates wind coming from IGP which increases the BC concentration. In another study at a high altitude station, Nainital (29.4*o*N, 79.5*o*E, 1950m asl), in central Himalayas, mean BC was observed to be 1.36±0.99 *μ*g.m−3 during December 2004 [55]. This shows that Mt. Abu is less affected by anthropogenic activities.

of seasalt aerosols from Arabian Sea. During Oct-Feb, high values of *α* are found indicating enhancement of anthropogenic aerosols. Ground-based observations show high abundance of BC on the hill-top region during winter. All these observations suggest that dust is dominating during premonsoon, anthropogenic aerosols during winter and natural seasalt are present in

Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 99

**Figure 8.** Space-borne daily observations of AOD, Ångstr*o*¨m exponent, small mode fraction (SMF) obtained from MODIS onboard Terra and Aqua satellites and aerosol index obtained from OMI onboard

Seasonal variation of aerosol vertical profiles over the study region is obtained from CALIPSO observations. Figure 9 shows the seasonal variation of aerosol extinction coefficient (km−1). The horizontal dotted line at 1.7 km represents the height of Mt. Abu. The extinction coefficient is directly proportional to the total aerosol loading. It is clearly seen from the figure that aerosol loading over Mt. Abu is minimum during winter and higher during other seasons. There is a peak found near 2.2 km altitude during monsoon which becomes weak during postmonsoon. Ganguly et al. [19] reported that this peak is due to seasalt aerosols transported from Arabian sea and chemical analysis also supports this result showing significantly high amount of seasalt present over Mt. Abu during monsoon [64]. During premonsoon, there is a peak at 4.2 km which is due to the transported dust layer. MODIS and

OMI observations also indicate significant amount of dust present in the atmosphere.

Near surface region also shows high extinction coefficient values. This could be due to locally produced anthropogenic aerosols. In the present study, the properties of aerosols at the

the atmosphere during monsoon season.

Aura satellite during 2006 and 2007.

**5.2. Aerosol vertical profile**

The diurnal variation of BC mass concentration does not show any significant morning and nocturnal peaks like other urban regions. However, increased BC was observed during the noon hours except during November and December. The reason for such an increase is during the day time the thermal convection becomes stronger and as a result, the pollutants at the foothill area rise up to the hilltop region and enhance the BC concentration. This day time enhancement was prominent during winter and postmonsoon because during these seasons there is a large difference between the day and night time temperatures. During November and December the night time BC concentration was larger by a factor of two. During these months the nearby villagers burn wood and fallen leaves to keep themselves warm thereby increasing the BC mass concentration. During January this nocturnal enhancement was not observed. The reason is that the boundary layer height is less than the station altitude and the night time BC that is produced cannot reach the hill top region due to weak thermal convection. During this period hill top region becomes pollutant free region.

## **5. Satellite observed aerosol properties over Mt. Abu region**

## **5.1. Aerosol optical and physical properties**

In the current satellite era, large databases are available to study aerosol properties from space, both in the regional and the global scale, that are essentially demanding. For the present study, Terra and a series of satellite sensors flying on the A-train platform provide the required data. MODIS on board Terra and Aqua provide aerosol parameters in the morning and afternoon. OMI on board Aura satellite provides AI. The joint information of AOD, Ångstr*o*¨m exponent (*α*) and small mode fraction (SMF) retrieved from MODIS and AI retrieved from OMI can be utilized to estimate the optical properties of aerosols with their size and type. In addition, the aerosol vertical distribution obtained from CALIPSO fulfills the requirement for the regional climate change study. In the present study, AOD, *α*, SMF and AI obtained from above multi-satellite observations are considered to distinguish the dominant natural and anthropogenic aerosols during different seasons. Figure 8 shows the multi-satellite observed AOD, *α*, SMF and AI over the study area during 2006–2007. Open circles represent the parameters obtained from MODIS-Aqua and filled circles are MODIS-Terra observations. AI gives information about the dust aerosols while SMF provides information about the anthropogenic and natural aerosols. Low SMF with low *α* indicates the presence of natural aerosols and the reverse represents the dominance of anthropogenic aerosols. AI has large values during Mar-Jul, whereas, *α* and SMF have low values. These combined observations suggest the abundance of coarse dust aerosols during these periods. OMI captures many dust storms over Thar Desert during premonsoon season in the AI images and enhancement of AI is due to transport of the dust plume from the desert region. During Aug-Feb, SMF is found to be high and AI is found to be very low indicating less abundance of dust aerosols in the atmosphere. In addition, *α* is also found to be very low during Aug-Sep but AOD is significantly high. Earlier studies from chemical composition of aerosol samples collected at Mt. Abu reported the enhancement of seasalt aerosols transported from Arabian sea during these periods and ground-based lidar observations at Ahmedabad, located 300 km to the south of Mt. Abu, reported the existence of a layer of seasalt aerosol in between 2–4 km [19, 64]. It can thus be inferred that the increase of monsoonal AOD is due to transport of seasalt aerosols from Arabian Sea. During Oct-Feb, high values of *α* are found indicating enhancement of anthropogenic aerosols. Ground-based observations show high abundance of BC on the hill-top region during winter. All these observations suggest that dust is dominating during premonsoon, anthropogenic aerosols during winter and natural seasalt are present in the atmosphere during monsoon season.

**Figure 8.** Space-borne daily observations of AOD, Ångstr*o*¨m exponent, small mode fraction (SMF) obtained from MODIS onboard Terra and Aqua satellites and aerosol index obtained from OMI onboard Aura satellite during 2006 and 2007.

## **5.2. Aerosol vertical profile**

18 Will-be-set-by-IN-TECH

asl), in central Himalayas, mean BC was observed to be 1.36±0.99 *μ*g.m−3 during December

The diurnal variation of BC mass concentration does not show any significant morning and nocturnal peaks like other urban regions. However, increased BC was observed during the noon hours except during November and December. The reason for such an increase is during the day time the thermal convection becomes stronger and as a result, the pollutants at the foothill area rise up to the hilltop region and enhance the BC concentration. This day time enhancement was prominent during winter and postmonsoon because during these seasons there is a large difference between the day and night time temperatures. During November and December the night time BC concentration was larger by a factor of two. During these months the nearby villagers burn wood and fallen leaves to keep themselves warm thereby increasing the BC mass concentration. During January this nocturnal enhancement was not observed. The reason is that the boundary layer height is less than the station altitude and the night time BC that is produced cannot reach the hill top region due to weak thermal

In the current satellite era, large databases are available to study aerosol properties from space, both in the regional and the global scale, that are essentially demanding. For the present study, Terra and a series of satellite sensors flying on the A-train platform provide the required data. MODIS on board Terra and Aqua provide aerosol parameters in the morning and afternoon. OMI on board Aura satellite provides AI. The joint information of AOD, Ångstr*o*¨m exponent (*α*) and small mode fraction (SMF) retrieved from MODIS and AI retrieved from OMI can be utilized to estimate the optical properties of aerosols with their size and type. In addition, the aerosol vertical distribution obtained from CALIPSO fulfills the requirement for the regional climate change study. In the present study, AOD, *α*, SMF and AI obtained from above multi-satellite observations are considered to distinguish the dominant natural and anthropogenic aerosols during different seasons. Figure 8 shows the multi-satellite observed AOD, *α*, SMF and AI over the study area during 2006–2007. Open circles represent the parameters obtained from MODIS-Aqua and filled circles are MODIS-Terra observations. AI gives information about the dust aerosols while SMF provides information about the anthropogenic and natural aerosols. Low SMF with low *α* indicates the presence of natural aerosols and the reverse represents the dominance of anthropogenic aerosols. AI has large values during Mar-Jul, whereas, *α* and SMF have low values. These combined observations suggest the abundance of coarse dust aerosols during these periods. OMI captures many dust storms over Thar Desert during premonsoon season in the AI images and enhancement of AI is due to transport of the dust plume from the desert region. During Aug-Feb, SMF is found to be high and AI is found to be very low indicating less abundance of dust aerosols in the atmosphere. In addition, *α* is also found to be very low during Aug-Sep but AOD is significantly high. Earlier studies from chemical composition of aerosol samples collected at Mt. Abu reported the enhancement of seasalt aerosols transported from Arabian sea during these periods and ground-based lidar observations at Ahmedabad, located 300 km to the south of Mt. Abu, reported the existence of a layer of seasalt aerosol in between 2–4 km [19, 64]. It can thus be inferred that the increase of monsoonal AOD is due to transport

2004 [55]. This shows that Mt. Abu is less affected by anthropogenic activities.

convection. During this period hill top region becomes pollutant free region.

**5. Satellite observed aerosol properties over Mt. Abu region**

**5.1. Aerosol optical and physical properties**

Seasonal variation of aerosol vertical profiles over the study region is obtained from CALIPSO observations. Figure 9 shows the seasonal variation of aerosol extinction coefficient (km−1). The horizontal dotted line at 1.7 km represents the height of Mt. Abu. The extinction coefficient is directly proportional to the total aerosol loading. It is clearly seen from the figure that aerosol loading over Mt. Abu is minimum during winter and higher during other seasons. There is a peak found near 2.2 km altitude during monsoon which becomes weak during postmonsoon. Ganguly et al. [19] reported that this peak is due to seasalt aerosols transported from Arabian sea and chemical analysis also supports this result showing significantly high amount of seasalt present over Mt. Abu during monsoon [64]. During premonsoon, there is a peak at 4.2 km which is due to the transported dust layer. MODIS and OMI observations also indicate significant amount of dust present in the atmosphere.

Near surface region also shows high extinction coefficient values. This could be due to locally produced anthropogenic aerosols. In the present study, the properties of aerosols at the

are coming from factories and vehicular emissions. However, there is significant contribution from marine sources as di-methyl sulphate. On the other hand, BC is mainly anthropogenic, but it becomes natural when produced during natural forest fires. In the present study, dust and seasalt are considered as natural aerosols and BC, sulphate and nitrates as anthropogenic aerosols. BC is obtained from ground-based measurements using Aethalometer. Other aerosols like dust, sulphate and nitrates are obtained from the chemical analysis of aerosols samples collected over this hill-top region [39, 40]. These chemical compositions are used as input to the OPAC model to obtained aerosol optical properties and compared with measured values. OPAC model is also used to distinguish the natural and anthropogenic aerosols by separating the natural and anthropogenic components. A scatter plot of monthly averaged AODs obtained from Microtops observations and OPAC model is shown in Figure 10. The solid line represents the 1:1 line. Model derived and observed AODs are linearly varying with a slope of 0.90 and very close to the 1:1 line which indicates that the model derived AOD are very close to the observed values. However, the model is underestimating the AOD by about 10%. This is due to the cut-off radius of aerosols at 7.5 micron considered by the model, but in reality, aerosols are larger, especially over semi-arid regions, though their residence period is

Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 101

only for a few hours and their contribution towards optical depth is small.

**6.2. Source identification of natural and anthropogenic aerosols**

region during premonsoon increasing natural dust aerosols.

**7.1. Seasonal variation of aerosol radiative forcing**

**7. Natural vs anthropogenic background aerosol radiative forcing**

Aerosol radiative forcing is estmated using SBDART model considering aerosol optical properties obtained from OPAC, aerosol vertical profile from CALIPSO and MODIS surface reflectance. Aerosol radiative forcings in different seasons are given in table 2. Aerosol radiative forcing is found to vary from -3.2 to +0.2 Wm−2 at TOA and from 6.1 to 23.6 Wm−2 within the atmosphere. Aerosol radiative forcing at TOA is found to be maximum of about 0.2±2.5 Wm−2 during premonsoon, followed by -1.3±0.5, -2.7±1.6, and -3.1±1.3 Wm−2 during monsoon, winter and postmonsoon, respectively. Forcing within the atmosphere is maximum of about 23.6±5.5 Wm−2 during premonsoon, followed by 12.5±3.9, 7.4±1.8, and 6.1±1.8 Wm−2 during monsoon, postmonsoon and winter, respectively. Annual mean aerosol forcing at Mt. Abu is found to be 8.7±3.4 Wm−2 which is lower than other urban

Seven days air parcel back trajectories are considered to identify the possible source regions of the natural and anthropogenic aerosols at Mt. Abu. The back-trajectories during premonsoon and winter are shown in Figure 11(a) and (b), respectively. Air parcels are mainly coming from IGP during winter and the heights of the trajectories are within 2 km. Ground based observations show that BC values at Mt. Abu are higher during winter and it is also clearly seen that there is long-range transportation of anthropogenic aerosols like BC from IGP within the boundary layer height. On the other side, air parcels are direction during premonsoon season. The heights are also greater than 3 km. Earlier chemical analyses report that dust concentration during this season is maximum of about 80% (in mass) of the total aerosols [39]. Therefore, one can easily conclude by these trajectories that the source of these dust aerosols is the nearby desert region. The back-trajectory analysis indicates that there is significant contribution of IGP during winter enhancing anthropogenic aerosols and that by nearby arid

**Figure 9.** Seasonal variation of vertical distribution of aerosol extinction coefficient obtained from CALIPSO observations. The horizontal dashed line at 1.7 km is the altitude of Mt. Abu.

hill-top region are considered and defined as the 'background aerosols'. The vertical profile of aerosols indicate that these background aerosols are less influenced from these locally produced anthropogenic aerosols. Therefore, the aerosol properties observed over Mt. Abu are assumed to represent those of the background aerosols over semi-arid region of western India.

## **6. Natural and anthropogenic background aerosol properties**

## **6.1. Estimation of natural and anthropogenic aerosols**

The estimation of natural and anthropogenic aerosols over this background site is a challenging task because many aerosol compositions have both origins. For example, sulphates are mainly considered as anthropogenic components over urban regions as they 100 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 21 Natural vs Anthropogenic Background Aerosol Contribution to the Radiation Budget over Indian Thar Desert 101

> are coming from factories and vehicular emissions. However, there is significant contribution from marine sources as di-methyl sulphate. On the other hand, BC is mainly anthropogenic, but it becomes natural when produced during natural forest fires. In the present study, dust and seasalt are considered as natural aerosols and BC, sulphate and nitrates as anthropogenic aerosols. BC is obtained from ground-based measurements using Aethalometer. Other aerosols like dust, sulphate and nitrates are obtained from the chemical analysis of aerosols samples collected over this hill-top region [39, 40]. These chemical compositions are used as input to the OPAC model to obtained aerosol optical properties and compared with measured values. OPAC model is also used to distinguish the natural and anthropogenic aerosols by separating the natural and anthropogenic components. A scatter plot of monthly averaged AODs obtained from Microtops observations and OPAC model is shown in Figure 10. The solid line represents the 1:1 line. Model derived and observed AODs are linearly varying with a slope of 0.90 and very close to the 1:1 line which indicates that the model derived AOD are very close to the observed values. However, the model is underestimating the AOD by about 10%. This is due to the cut-off radius of aerosols at 7.5 micron considered by the model, but in reality, aerosols are larger, especially over semi-arid regions, though their residence period is only for a few hours and their contribution towards optical depth is small.


**5. Conclusions**

There is a major difference between microalgae and cyanobacteria in terms of their cell structure and this work has presented unmistakable evidence that microalgae have a nucleus and chloroplast, and their makeup includes their full identity in a two-stranded DNA. On the other hand, cyanobacteria are identified by one-stranded DNA and do not have a nucleus and neither a chloroplast. However, Microalgae and cyanobacteria do photosynthesize to produce their food.

It is seen from research as discussed in this chapter that value products aimed to meet pharmaceutical and food needs are obtainable by continuous availability of nutrients to the microalgae in the culture media. It is also seen that to accumulate lipid in the order of triglycerides for biodiesel production, microalgae must experience nutrients deficiency in the culture media at the stationary stage of growth.

The hydrodynamics of the microalgal culture broth depends on the choice of bioreactor for a particular cultivation activity and contributes to the algal growth factor.

The versatility of the microalgal biomass is expressed in the diversity of metabolites produced by manipulation of the growth factors in favor of the desired product. Also, the choice of the strain will drive towards the targeted product.

#### **Acknowledgements**

The authors appreciate the Institute for Water and Wastewater Technology (IWWT), Durban University of Technology, Durban for providing the platform for scientific investigations.


**11. Significance of the study**

Students have to be prepared to solve the problems and skillfully to do their work towards fulfilling the 21st century requirement. Learners need to develop their own competencies to face any kind of difficult situations and they have to show their ability in all aspects how they are unique and competent from others. Developing competencies possible through meaningful learning application in every curriculum transaction. In this perspective undergraduate student-teachers have been trained through emotive cognition intervention programme on enhancing meaningful learning among future teachers. Cultivating meaningful learning create clear knowledge, skills and appropriate behavior modification to the learner. Meaningful learning develop proper understanding, experience and thinking ability among student-teachers. Understanding these concepts can help teacher educators to design a meaningful


**5.1 The relationship between melatonin and blood pressure**

It has been reported in previous studies that blood pressure and catecholamine levels are related to circadian rhythm. Blood serum melatonin levels of patients with hypertension were found to be low [46]. In addition, melatonin administration has been found to decrease blood pressure in hypertensive and normotensive patients [47, 48]. Yıldız and Akdemir investigated the endogenous role of melatonin on arterial elasticity and blood pressure for arterial expandability as assessed by aortic pulse wave velocity [49]. Melatonin reduces vascular pressure through its receptor on the arterial wall or by modulation of autonomic activity [50]. It has been reported that the vasodilator effect of melatonin can be achieved by inhibiting the methylation of endothelial nitric oxide synthase [51]. In some studies, melatonin has been reported to cause vasoconstriction by inducing norepinephrine signaling as a result of melatonin binding to MT1 receptors on smooth muscle cells [52].

Doolen et al. demonstrated a vasodilator effect on rat caudal arteries by administering 4-phenyl-2-acetamidotetralin, a selective MT2 agonist [53]. According to our current knowledge, MT1 receptor activation causes vasoconstriction, while MT2 receptor activation causes vasodilation [53]. Differential responses of the vascular bed to melatonin uptake are associated with different distribution of melatonin receptors.


2.4.1. Transmission Electron Microscope (TEM)

TEM images were performed with a transmission electron microscope LEO 912AB OMEGA, Zeiss (Oberkochen, Germany) at an acceleration voltage of 100 kV. Cu-carrying chitosan composites for measurements were previously suspended in deionized water (resisting 18 MΩ) and sonicated in an ultrasonic bath for 15 min at RT. Then, a small drop of the suspension was dripped onto a copper grid (200 mesh) previously coated with formvar film. Then, the samples were dried at RT for 15 min and placed under the microscope.