Supplementary Material

Seasonal characteristics of water-soluble inorganic ions and carbonaceous aerosols in total suspended particulate matter at a rural semi-arid site, Kadapa (India)

G. Reshma Begama, C. Viswanath Vachaspatia, Y. Nazeer Ahammeda,*,

K. Raghavendra Kumarb, R. R. Reddyc, S.K. Sharmad, Mohit Saxenad

T.K. Mandald

aAtmospheric Science Laboratory, Department of Physics, Yogi Vemana University, Kadapa 516 003, Andhra Pradesh, India

bCollaborative Innovation Centre for Forecast and Evaluation of Meteorological Disasters, Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044, Jiangsu, China

cAerosol and Atmospheric Research Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur 515 003, Andhra Pradesh, India

dCSIR-National Physical Laboratory, DR.K S Krishna Road, New Delhi-110 012, India

*Corresponding author

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S1. Calculation of effective cut-off diameter (ECD) for PM2.5 and PM10-2.5

In the present study the mass concentration for each size bin and cumulative mass concentration respective to ECD were calculated for all samples following the procedure given in Das et al. (2006). By plotting the logarithm of ECD against cumulative mass concentration less than stated size (Das et al., 2006) for each data set, the PM2.5 and PM10-2.5 fractions were calculated. As an example, the calculation procedure with value of fine- and coarse-mode fractions obtained from the regression fitting for the month December 2013 (y = 0.280x–5.577: R2 = 0.98) of the corresponding graph has been demonstrated in Fig. S1.

Table S1 Correlation statistics of different size fractions of PM

PM10 / PM2.5 / PM1 / PM10-2.5
TSPM / 0.83 / --- / --- / 0.70
PM10 / --- / 0.72 / 0.64 / 0.78
PM2.5 / --- / --- / 0.90 / ---

S2. PM concentrations at nine selected size bins

Figure S3 (a-j) represents the distribution of PM mass concentrations for different size fraction drawn as a function of wind speed and direction. For the size fractions 9-10 mm, an elevated concentrations has been observed from NW to SE directions except, NE direction and other bin (5.8-9), particle concentration was noted high in the NW, E and SE directions. Furthermore, the particle concentrations were elevated particularly, in the directions SW and SE for the bin size 4.7-5.8 mm and a very narrow data set with low concentration was observed for the size fractions 3.3-4.7 and 2.1-3.3 mm in the direction of SE and SW. In the east and south directions, particle concentrations were highly accumulated in the size fraction of 1.1-2.1 mm. Similarly, for the size fraction of 0.7-1.1 mm, the wind direction was along the south, east and north directions and completely absent in the NW, SW and W directions. For the size fraction (0.4-0.7 mm), the concentration was not significant in any direction; concentration was negligible when the winds were coming from the NE and NW-SW directions. For the last size fraction (0-0.4 mm), PM concentrations were completely absent, if the windblown from S-SW and it was maximum if the winds were from W-SW direction.