Browsing by Author "Balakrishnaiah, G."

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Analysis of Diurnal and Seasonal Behavior of Surface Ozone and Its Precursors (NOx) at a Semi-Arid Rural Site in Southern India
(2012-12-01)
Reddy, B. Suresh Kumar
;
Kumar, K. Raghavendra
;
Balakrishnaiah, G.
;
Gopal, K. Rama
;
Reddy, R. R.
Surface measurements of O-3, NO, NO2 and NOx have been made over a semi-arid rural site, Anantapur (14.62 degrees N; 77.65 degrees E; 331 m asl) in southern India, during January-December 2010. The highest monthly mean O-3 concentration was observed in April (56.1 +/- 9.9 ppbv) and the lowest in August (28.5 +/- 7.4), with an annual mean of 40.7 +/- 8.7 ppbv for the observation period. Seasonal variations in O3 concentrations were the highest during the summer (70.2 +/- 6.9 ppbv), and lowest during the monsoon season (20.0 +/- 4.7 ppbv), with an annual mean of 40.7 +/- 8.7 ppbv. In contrast, higher NOx values appeared in the winter (12.8 +/- 0.8 ppbv) followed by the summer season (10.9 +/- 0.7 ppbv), while lower values appeared in the monsoon season (3.7 +/- 0.5 ppbv). The results for O-3, NO and NO2 indicate that the level of oxidant concentration ([OX] = NO2 + O-3) at a given location is the sum of NOx-independent "regional contribution" (background level of O-3) and linearly NOx-dependent "local contribution". The O-3 concentration shows a significant positive correlation with temperature, and a negative correlation with both wind speed and relative humidity. In contrast, NOx have a significant positive correlation with humidity and wind speed, and negative correlation with temperature. The slope between [BC] and [O-3] suggests that every 1 mu g/m(3) increase in black carbon aerosol mass concentration causes a reduction of 4.7 mu g/m(3) in the surface ozone concentration. A comparative study using satellite data shows that annual mean values of tropospheric ozone contributes 12% of total ozone, while near surface ozone contributes 82% of tropospheric ozone. The monthly mean variation of tropospheric ozone is similar to that tropospheric NO2, with a correlation coefficient of +0.80.
Ground-based in situ measurements of near-surface aerosol mass concentration over Anantapur: Heterogeneity in source impacts
(2013-01-01)
Reddy, B. S. K.
;
Kumar, K. R.
;
Balakrishnaiah, G.
;
Gopal, K. R.
;
Reddy, R. R.
Surface measurements of aerosol physical properties were made at Anantapur (14.62A degrees N, 77.65A degrees E, 331 m a.s.l), a semiarid rural site in India, during August 2008-July 2009. Measurements included the segregated sizes of aerosolsas as well as total mass concentration and size distributions of aerosols measured at low relative humidity (RH < 75%) using a Quartz Crystal Microbalance (QCM) in the 25-0.05 mu m aerodynamic diameter range. The hourly average total surface aerosol mass concentration in a day varied from 15 to 70 mu g m(-3), with a mean value of 34.02 +/- 9.05 mu g m(-3) for the entire study period. A clear diurnal pattern appeared in coarse, accumulation and nucleation-mode particle concentrations, with two local maxima occurring in early morning and late evening hours. The concentration of coarse-mode particles was high during the summer season, with a maximum concentration of 11.81 +/- 0.98 mu g m(-3) in the month of April, whereas accumulationmode concentration was observed to be high in the winter period contributed > 68% to the total aerosol mass concentration. Accumulation aerosol mass fraction, A (f) (= M (a)/M (t)) was highest during winter (mean value of A (f) 0.80) and lowest (A (f) 0.64) during the monsoon season. The regression analysis shows that both R (eff) and R (m) are dependent on coarse-mode aerosols. The relationship between the simultaneous measurements of daily mean aerosol optical depth at 500 nm (AOD(500)) and PM2.5 mass concentration ([PM2.5]) shows that surface-level aerosol mass concentration increases with the increase in columnar aerosol optical depth over the observation period.
Potential Source Regions Contributing to Seasonal Variations of Black Carbon Aerosols over Anantapur in Southeast India
(2012-06-01)
Reddy, B. Suresh Kumar
;
Kumar, K. Raghavendra
;
Balakrishnaiah, G.
;
Gopal, K. Rama
;
Reddy, R. R.
Continuous measurements of black carbon (BC) mass concentration performed at Anantapur [14.62 degrees N, 77.65 degrees E, 331 m asl], a suburban location in southeast India, using an Aethalometer from January to December, 2010, are analyzed and discussed here. The annual mean BC mass concentration ([BC]) was 3.03 +/- 0.27 mu g/m(3) for the above study period. The sharp morning (fumigation) peak occurs between 07:00 and 08:00 h almost an hour after the local sunrise while a broad evening (nocturnal) peak is at similar to 21:00 h with a minimum in noon hours (14:00-16:00 h). The seasonal mean values of [BC] are 5.05 +/- 0.51 mu g/m(3) in the winter, 3.77 +/- 1.23, 1.55 +/- 0.51, and 2.33 +/- 0.82 mu g/m(3) in the summer, monsoon and postmonsoon seasons, respectively. High BC values tend to occur when the wind is directed from the 180-225 degrees sector, which may be well defined by the geographical location of the observation site. During the winter, the trajectory air mass pathways originated through north or central India with significant advection of continental aerosols arriving before the measurement region, results in an enhanced [BC]. Whereas in the monsoon season, the pristine marine air mass from the oceanic environment led to decrease in the concentration of BC. Comparison of monthly mean variations in AOD at 500 nm and black carbon aerosols is observed to be positive with poor correlation coefficient of 0.42. The ratio of BC/PM2.5 varied from 1.3% to 7.2% with a mean value of 4.6% at Anantapur during the observation period and this ratio decreased with decreasing Angstrom exponent (alpha).