The earth's environment is constantly changing. The scientific evidence indicates that these changes are result of a complex interplay among several natural and human-related systems. Therefore, in recent times, concern has grown about global change—which is related to natural and anthropogenic alteration of the Earth's environment. Among them, the important issues of concern are global greenhouse warming, urban and regional atmospheric pollution, regional increases in tropospheric ozone, the decrease in stratospheric ozone in general and the ozone hole over Antarctica in particular, acid rain, and so on. In Antarctica, contamination sources are distant, and the air is very well mixed, extremely clean, and far removed from spatial and seasonal changes. It is truly the background air of the planet compared to measurements made elsewhere around the globe. Antarctica holds the most efficiently coupled radiation-ice-air-ocean interactive system, which sustains primitive life forms over the continent. In this coupled system, atmosphere plays a vital role in the transfer of thermal energy and the momentum from one system to another, resulting in sustaining the Antarctic continent and its environment over the past millions of years. However, despite its sustenance, the Antarctic environment is influenced by global changes, which need to be evaluated to study the future of Earth's environment. Therefore, special conditions prevailing over Antarctica make it an ideal site for the monitoring of various atmospheric parameters. National Physical Laboratory (NPL), New Delhi, has been participating in the Indian Antarctic Expeditions right from its inception in 1981 and is carrying out scientific investigations related to the Antarctic atmospheric environment. The major experiments set up by NPL over the years at Maitri include VLF; riometer; microbarograph; weather station to monitor meteorological parameters; 28-meter-high tower to install sensors for meteorological parameter measurement at different heights; collection of air samples for gaseous concentration; high-volume air sampler; SODAR for planetary boundary layer studies; laser heterodyne and mm wave radio spectrometer to get ozone profiles; liquid nitrogen plant to produce liquid nitrogen needed for the laser heterodyne system; sun photometer; UV biometer; MICROTOP to estimate column ozone, water vapor, aerosol optical depth, and so on; gas chromatogram for regular monitoring of greenhouse gases such as CO2, CH4, and so on; and NDIR CO analyzer for around-the-clock monitoring of CO. In the present chapter, the salient features of various experiments conducted by NPL and results obtained are discussed in detail.

Simultaneous measurements of aerosol black carbon (BC) mass concentration using an Aethalometer Model AE-42 and mixing layer height (MLH) using a monostatic sonic detection and ranging (SODAR) system were carried out from January 2006 to January 2007 at the mega-city Delhi. The BC concentration generally had a typical diurnal variation with morning and late-afternoon/night peaks. The average BC concentration during the whole period of observation was fairly high at 14.75 mu g m(-3). The BC concentration nearly doubled during cloudy-sky conditions compared to that during clear-sky conditions. The seasonal variation showed a maximum average concentration during the winter (25.5 mu g m(-3)) and a minimum during the monsoon season (7.7 mu g m(-3)), with post-and pre-monsoon values at 13.7 and 9.4 mu g m(-3), respectively. The average BC concentrations were strongly affected by the ventilation coefficient, a product of average wind speed (WS) and average MLH, and were found to be strongly anticorrelated. A simple model of BC concentration along with the MLH and WS was applied to estimate the average BC emission, which was found to vary in the range 11 000-17 000 kg of BC per day. The maximum emission during the day averaged every hour for different months lay in the range 1000-2100 kg h(-1). The mean monthly emission varied in the range 0.35-0.52 Gg per month, giving rise to an annual estimated emission of 4.86 Gg in the year 2006 over Delhi.

The aerosol optical depth (AOD), Angstrom coefficients (alpha and beta), and the second-order Angstrom exponent (alpha') obtained by Microtops-II sun photometer have been analyzed in the spectral range 0.34-0.87 mu m over the urban polluted city of Delhi, India for the period 2007-2008, aiming at investigating the physical and optical properties of aerosols. The average values of AOD at 500 nm, alpha and beta (in the range 340-870 nm) are found to be 0.78 +/- 0.32, 0.78 +/- 0.28, and 0.45 +/- 0.21, respectively, for the entire period of observations. The AOD data show significant curvature in the ln tau versus ln lambda relationship suggesting different dominant aerosol types depending on season. In order to analyze further the curvature effect and the relative dominance of aerosol size, alpha has been calculated in three wavelength bands, i.e., shorter (0.34-0.50 mu m), longer (0.675-0.87 mu m), and broad (0.34-0.87 mu m) during four seasons, summer (April-June), monsoon (July-September), winter (October-January), and spring (February-March) accompanied with calculations of alpha', which quantifies the deviation of logarithmic behavior of AOD with ln lambda. The alpha' values are found to be positive and higher in the months of October-December and mostly negative in February and March, while close to zero values of alpha' are found in April-August. These results indicate that winter season exhibits dominance of fine-mode aerosols while summer relatively higher concentration of coarse-mode particles. On the other hand, monsoon and spring seasons revealed the presence of mixed type, both fine-and coarse-mode aerosols over Delhi.

Simultaneous measurements of aerosol absorption and scattering coefficients for the PM2.5 aerosols particles were done at Delhi during April 2008-March 2009 to estimate the aerosol single scattering albedo (SSA) and the Angstrom absorption exponents at the surface. The annual average SSA at 0.55 mu m was found to be 0.70 +/- 0.07 with only slight variations during the four seasons, summer (0.63 +/- 0.06), monsoon (0.69 +/- 0.07), winter (0.74 +/- 0.03) and spring (0.72 +/- 0.04). However, large variations in average absorption and scattering coefficients were seen during these four seasons. The average absorption coefficients during summer, monsoon, winter and spring were found to be 62.47 +/- 21.27, 50.95 +/- 43.61, 189.65 +/- 85.94 and 90.65 +/- 33.06 Mm(-1) respectively. The corresponding scattering coefficients were 110.46 +/- 36.15, 95.34 +/- 49.46, 565.59 +/- 274.59 and 236.56 +/- 96.25 Mm(-1). The Angstrom absorption exponent (alpha(sigma(abs))) remained close to unity throughout the year averaging at 1.02 +/- 0.08, 1.02 +/- 0.10, 1.04 +/- 0.11, and 1.03 +/- 0.05 during summer, monsoon, winter and spring seasons respectively, strongly indicating that the absorption at Delhi aerosol is mainly due to the abundance of black carbon of fossil fuel origin. (C) 2010 Elsevier Ltd. All rights reserved.

The direct aerosol radiative forcing (DARF) has been estimated for the clear-sky conditions over Delhi from January 2006 to January 2007 using Santa Barbara DISORT Atmospheric Radiative Transfer model (SBDART) in the wavelength range 300–3000 nanometer. The single scattering albedo (SSA) and the asymmetry parameter used in this model were estimated using the Optical Properties of Aerosol and Cloud (OPAC) model. The annual average AOD observed at 500 nm was ~0.86±0.42 with an average Angstrom exponent ~0.68±0.35. The average monthly AOD throughout the year over Delhi was found to be in the range 0.56 to 1.22 with the Angstrom exponent in the range 0.38 to 0.96. A high monthly average BC concentration in the range 4–15 μg m−3 led to monthly average SSA in the range 0.90±0.4 to 0.74±0.3 during the year. Consequently, the monthly average clear-sky DARF at the surface was found to vary in the range −46±8 W m−2 to −110±20 W m−2, at TOA in the range −1.4±0.4 to 21±2 W m−2, whereas in the atmosphere it was in the range 46±9 W m−2 to 115±19 W m−2 throughout the year. As the dust concentration in the atmosphere was highest (May–June) the SSA showed an increase with wavelength however when dust concentration was low the SSA decreased with the wavelength.

Cell free culture filtrate of Bacillus licheniformis isolated from rhizosphere soil of a healthy tomato plant was extracted with ethanol, methanol, ethyl acetate, dichloromethane and hexane. After removal of solvents these extracts were tested for antifeedant and insect growth activity against 3rd instars larvae of Helicoverpa armigera. Maximum antifeedant activity was exhibited by ethanol extract (Al50= 0.019%) and minimum by hexane extract (0.088%). The larval mortality ranged from 10.0–70.0% in different extracts. Two polar metabolites separated from ethanol extract showed Al50 of 0.015 and 0.053%.

Bacillus sp. KM5 was isolated from the rhizosphere soii of healthy rice plant. The effect of culture broth on the seed germination, root and shoot length at different concentrations was studied. The culture broth of KM5 increased the root and shoot length of wheat seedling, whereas it did not show any effect in the case of rice seedllngs. It showed a negative effect in the case of chickpea.

Black Carbon (BC) aerosols are the main sunlight-absorbing component of atmospheric aerosols. In this paper we present results of BC aerosols concentration at typical weather conditions over Delhi during June 2005 to June 2006 using an Aethalometer. We studied for foggy, rainy, dusty and very clear days. The BC concentration shows pronounced variations with weather changes. The annual average BC concentration was 16.32 μg/m of which foggy days concentrations were maximum while the clear days were minimum. The average BC concentration during foggy days reaches up to ~50.39 μg/m in comparison to clear days which peaks only upto ~6.8 μg/m, so foggy days values is 7.4 times more. Followed by foggy days, rainy days show the higher BC concentration. The average values are ~6.82 μg/m and 6.9 μg/m for dusty days and dust storm period respectively. The BC concentration shows strong anti-correlation with the mixing layer height measured simultaneously using an acoustic SODAR. Stronger anticorrelation (correlation coefficient –0.618) was found with the ventilation coefficients. The effect of BC aerosols over Radiative forcing has also been estimated using OPAC and SBDART model.

3,7-Dimethyl-2,6-octadien-1-aldoxime-N-O-alkyl ethers have been synthesized, separated into their four isomers viz, 3,7-dimethyl-2(E),6-octadien-1-(E)-aldoxime N-O-alkyl ether, 3,7-dimethyl-2(Z),6-octadien-1-(Z)-aldoxime N-O-alkyl ether, 3,7-dimethyl-2(E),6-octadien-1-(Z)-aldoxime N-O- alkyl ether and 3,7-dimethyl-2(Z),6-octadien-1-(E)-aldoxime N-O- alkyl ether and characterized on the basis of 1H-NMR and mass fragmentation pattern. They have been evaluated for their juvenile hormone mimetic activity against red cotton bug, Dysdercus koenigii. Maximum JH mimetic activity has been shown by 3,7-dimethyl-2,6-octadien-1-aldoxime-N-O-butyl ether (3.1458 μg per insect). Structure activity relationship studies revealed that maximum activity was associated with compounds having four carbons atoms in the oxime ether moiety.

4’-(2,6,6-Trimethyl-2-cyclohexen-1-yl)-3’-buten-2’-ketoxime-N-O-alkyl ethers have been synthesized, separated into their E and Z isomers and characterized on the basis of 1H-NMR spectra. They have been evaluated for their juvenile hormone mimetic activity against red cotton bug, Dysdercus koenigii Fab. Maximum JH mimettc activities have been shown by 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-propyl) ether followed by 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-pentyl) ether, 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-hexayl) ether, 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-heptyl) ether, 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(E)-ketoxime-N-O-octyl) ether, 4’-(2,6,6-trimethyl-2-cyclohexen-1-yl)-3’-buten-2’(Z)-ketoxime-N-O-butyl ether and 4’-(2,6,6-trimethyl -2-cyclohexen-1-yl) -3’-buten-2’(Z)-ketoxime-N-O-pentyl) ether. Structure activity relationship studies revealed that maximum activity was associated with compounds having three or more carbon atoms in the oxime ether moiety. The E-lsomer has been found to be more active than Z-isomer.

Characteristics of trace gases (O3, CO, CO2, CH4 and N2O) and aerosols (particle size of 2.5 micron) were studied over the Arabian Sea, equatorial Indian Ocean and southwest part of the Bay of Bengal during the monsoon transition period (October–November, 2004). Flow of pollutants is expected from south and southeast Asia during the monsoonal transition period due to the patterns of wind flow which are different from the monsoon period. This is the first detailed report on aerosols and trace gases during the sampled period as the earlier Bay of Bengal Experiment (BOBMEX), Arabian Sea Monsoon Experiment (ARMEX) and Indian Ocean Experiments (INDOEX) were during monsoon seasons. The significant observations during the transition period include: (i) low ozone concentration of the order of 5 ppbv around the equator, (ii) high concentrations of CO2, CH4 and N2O and (iii) variations in PM2.5 of 5–20μg/m3.

The effect of solar ultraviolet radiation on human skin is a matter of human concern and wide interest in scientific community during last few decades. National Physical Laboratory (NPL, New Delhi, India) initiated the solar UV-B radiation (280320nm) intensities studies all over the Indian mainland and over Antarctica since 1980s. For Delhi site, continuous measurement of the UV-B has been done for the last 20 years along with sporadic field campaigns at various mainland, islands and oceanic sites. The atmospheric aerosol optical depth in visible and near infrared regions has also been done along with UV-B observations for many locations. One such campaign has been done at Port Blair Port Blair (Andaman Islands, 11.67 N, 92.72 E, 78m amsl) during March 2002. The present work emphasizes the results of this field campaign as a relatively cleaner site and its comparison with urban polluted location – Delhi (28.4 N, 77.1 E, 216m amsl). The observations at both sites were taken under clear sky conditions and the column atmospheric ozone values were almost similar. The UV-B measurements were carried out by Erythemal Probe (International Light Inc., USA) having interference filter of wavelength band 290-301 nm (maximum sensitivity/transmission at 297.5 nm). The aerosol optical depth (AOD) was derived from the solar radiation intensity measurements by grating based, solid-state spectroradiometer operating in the wavelength range 350-1100 nm, (International Light Inc., USA). Satellite based measurements were also seen for AOD. Results show an average global radiation intensity for the campaign period as∼5.5x10−6 W/cm2,∼9.0x10−6 W/cm, ∼1.25x10−6 W/cmand ∼1.5x10−5 W/cm−2 at χ = 60, 50, 40 and 30 , respectively, while these intensities were found to be ∼3.0x10−6 W/cm, ∼5.0x10−6 W/cm, ∼9.0x10−6 W/cm and ∼1.0x10−5 W/cm−2 at Delhi. The observed AOD at these sites during campaign periods were found to be ∼0.3-0.4 at Port Blair and ∼0.5–0.6 at Delhi at 500 nm wavelength on an average. The ratio global/direct radiation varied ∼2.0–3.5 at Port Blair for χ =30 , and between 2.0-4.0 at Delhi, however, at χ = 60 , these values were ∼2.5-7.0 at Port Blair and ∼4.5-19.5 at Delhi. On an average, the global UV-B radiation intensities were found to be ∼65% less at Delhi than at Port Blair. It is clearly found that the increase in UV-B radiation forcing is influenced by increase in AOD.

Toxins namely gliotoxin, dimethyl gliotoxin, viridin and viridiol were isolated from chloroform extract of 15 days old culture filtrate of a strain of Trichoderma virens (ITC-4777) grown in potato dextrose broth. Their structures were confirmed by 1H-NMR, and mass spectroscopy. Gliotoxin was found to be active against Rhizoctonia bataticola (ED50 0.03 µg ml-1), Macrophomina phaseolina (ED50 1.76 µg ml”1), Pythium deharyanum (ED50 29.38 µg ml1), Pythium aphanidermatum (ED50 12.02 µg ml-1), Sclerotium rolfsii (ED50 2.11 µg ml-1), Rhizoctonia solani (ED50 3.18 µg ml−1). Decrease in production of gliotoxin was observed with increase in days of incubation of culture of T. virens. Maximum production of gliotoxin was observed in the 7 day old culture filtrate.