Abstract. Understanding the vertical electron density profile, which is the altitudinal variation of ionospheric electron density distribution is an important aspect for the ionospheric investigations. In this paper, the bottom-side electron density profiles derived from ground based ionosonde data and the ROCSAT-1 in-situ electron density data were used to determine the estimates of the topside electron density profiles using α-Chapman function over an equatorial station Trivandrum (8.47 • N, 76.91 • E) and a low latitude station Waltair (17.7 • N, 83.3 • E) in the Indian region. The reconstructed electron density profiles are compared with IRI (2007) model derived vertical electron density profiles which resulted in significant deviations between the two different profiles. Both the reconstructed electron density profiles and the IRI model derived profiles are integrated independently to derive the Total Electron Content (TEC) values which are compared with GPS derived TEC values. TEC values derived from the reconstructed electron density profiles give better estimates with the GPS-TEC compared to those of IRI model derived TEC values. Compared to the GPS-TEC, the IRI model is underestimating the TEC values during day-time and is overestimating during night-time at both the stations. The percentage deviations of IRI derived TEC from GPS-TEC are larger compared to those between reconstructed profile derived TEC and GPS-TEC.F2-layer peak electron density, peak height and electron density at ROCSAT altitudes (≈600 km) are used to derive the effective scale heights (H T ) of the topside ionosphere during the period from July 2003 to June 2004. The diurnal and seasonal variations of H T and E × B drift velocities are presented in this paper. The diurnal variation of the effective scale height (H T ) shows peak values around noon hours with higher values during day-time and lower values during Correspondence to: P. V. S. Rama Rao (palurivsrao@gmail.com) night-time both at Trivandrum and Waltair. The E × B drift velocities at both the places also have shown a clear diurnal variation with a negative peak around 04:00 LT and maximum during day-time hours. The higher and lower values of H T seem to be associated with positive and negative phases of the E × B drift velocities, respectively.

A B S T R A C TThe natural polymers used in water and wastewater treatment systems include starches, galactomannans, cellulose derivatives, chitosan, microbial polysaccharides, gelatin, glues, and alginate. These natural coagulants are capable of treating water from high to low turbid water and having removal efficiency of sometimes more than 98% that can be used for drinking purposes. Naturally occurring coagulants are usually presumed safe for human health, while there is a fear that using aluminum salts may induce Alzheimer's disease. These natural coagulants are usually used as coagulant aid in combination with some synthetic coagulants, their effectiveness as the primary coagulant is still in beginnings. The mechanisms of treatment in these coagulants include intermolecular bridging, complexation process, adsorption, and charge neutralization. A review of non-plant-based natural coagulants, coagulating mechanisms, effectiveness, and its applications has been presented.

Abstract. The ionospheric equivalent slab-thickness is an important parameter which measures the skewness of the electron density profile of the ionosphere. In this paper, the diurnal, seasonal, day-to-day and latitudinal variations of ionospheric parameters namely total electron content (TEC), the peak ionization density of F-layer (NmF2), equivalent slab-thickness (τ ) and neutral temperature (T n ) are presented. The simultaneous data of GPS-TEC and NmF2 from Trivandrum (8.47 • N, 76.91 • E), Waltair (17.7 • N, 83.3 • E) and Delhi (28.58 • N, 77.21 • E) are used to compute the slabthickness (τ = TEC/NmF2) of the low sunspot period, [2004][2005]. The day-time TEC values at Waltair are found to be greater than those at Trivandrum, while at Delhi the day-time TEC values are much lower compared to those at Trivandrum and Waltair. The trends of variation in the monthly mean diurnal variation of TEC and NmF2 are similar at Delhi, while they are different at Trivandrum and Waltair during the daytime. The slab-thickness (τ ) has shown a pre-sunrise peak around 05:00 LT at all the three stations, except during the summer months over Delhi. A consistent secondary peak in slab-thickness around noon hours has also been observed at Trivandrum and Waltair. During equinox and winter months a large night-time enhancement in the slab-thickness (comparable to the early morning peak in slab-thickness) is observed at Delhi. The latitudinal variation of slab-thickness has shown a decrease from the equatorial station, Trivandrum to the low-mid latitude station, Delhi. The neutral temperatures (T n ) computed from the slab-thickness (τ ) has shown a sharp increase around 05:00 LT over Trivandrum and Waltair. Whereas at Delhi, a double peaking around 05:00 and 23:00 LT is observed during winter and equinoctial months. The neutral temperatures computed are compare well with those of the MSIS-90 model derived temperatures.

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This paper presents the temporal variation in surface-level ozone (O 3) measured at Gummidipoondi near Chennai, Tamilnadu. The site chosen for the present study has high potential for ozone generation sources, such as vehicular traffic and industrial activities. The site is also located near a hazardous waste management facility. The key sources of nitrogen oxides (NO x), which are considered to be an important precursor of O 3 , include hazardous waste incineration, trucks bringing the hazardous wastes, and vehicles plying on the nearby National Highway 16 (NH 16). The measurements clearly showed diurnal variation, with maximum values observed during the noon hours and minimum values observed when solar radiation was less. The data showed a marked seasonal variation in O 3 , with the highest hourly average O 3 concentration (497.2 µg/m 3) in the summer season. Consequently, in order to identify the long-range transport sources adding to the increased O 3 levels, backward trajectories were computed using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. It was found that the polluted air mass originated from the Southeast Asian region and the Indo-Gangetic Plain. The polluted air mass, which advected large amounts of carbon monoxide (CO) plumes, was analyzed using the Measurement of Pollution in the Troposphere (MOPITT) retrievals. The correlations of O 3 with temperature (r = 0.746; P < 0.01) and solar radiation (r = 0.751; P < 0.01) were strongly positive, and that with NO x was found to be negative. Stronger correlation of O 3 with NO x was observed during pre-monsoon months (r = 0.627; P < 0.01) and following hours of photochemical reactions. There were substantial differences in concentrations between weekdays and weekends, with higher nitric oxide (NO) and nitrogen dioxide (NO 2), but lower O 3 , concentrations on weekdays. A substantial weekday-weekend difference in O 3 , which was higher on weekends, appears to be attributable to lower daytime traffic activity and hence reduced emissions of NO x to a "NO x-saturated" atmosphere. Implications: The assessment of ground-level ozone in an industrial area with hazardous waste management facility is very important, as there is high possibility for more generation of tropospheric ozone. Since the location of the study area is coastal, wind plays a major role in O 3 transportation; hence, the effects of wind speed and wind direction have been studied in different seasons. When compared with the other studies carried out in different places across India, the present study area has recorded much greater O 3 mixing ratio. This study can be useful for setting up control strategies in such industrial areas.