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Original Articles

Aerosol Inorganic Composition at a Tropical Site: Discrepancies Between Filter-Based Sampling and a Semi-Continuous Method

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Pages 255-269 | Received 30 Apr 2007, Accepted 14 Feb 2008, Published online: 28 Apr 2008

Figures & data

TABLE 1 Overview of aerosol samplers and analytical techniques employed for the measurement of the aerosol species NH4 +, NO3 , Cl, and SO4 2− at FNS during LBA-SMOCC 2002

TABLE 2 Filter blanks of the aerosol species NH4 +, NO3 , Cl, and SO4 2− expressed as average percentage [%] of typically observed concentrations at FNS during LBA-SMOCC 2002

FIG. 1 Box-and-whisker plots showing statistical distributions of concentrations during daytime (D) and nighttime (N) for aerosol ions (a) NH4 +, (b) NO3 , (c) Cl, and (d) SO4 2− measured with the WAD/SJAC, DFP (Teflon filters), SFU (polycarbonate filters), and HiVol sampler (quartz-fiber filters) during the dry (biomass burning) season (12–23 Sep.) at FNS during LBA-SMOCC 2002 (HiVol samples were analyzed for PM2.5 only, elemental S is presented as SO4 2− equivalent assuming that the measured S concentration is entirely attributable to aerosol SO4 2−).

FIG. 1 Box-and-whisker plots showing statistical distributions of concentrations during daytime (D) and nighttime (N) for aerosol ions (a) NH4 +, (b) NO3 −, (c) Cl−, and (d) SO4 2− measured with the WAD/SJAC, DFP (Teflon filters), SFU (polycarbonate filters), and HiVol sampler (quartz-fiber filters) during the dry (biomass burning) season (12–23 Sep.) at FNS during LBA-SMOCC 2002 (HiVol samples were analyzed for PM2.5 only, elemental S is presented as SO4 2− equivalent assuming that the measured S concentration is entirely attributable to aerosol SO4 2−).

TABLE 3 Summary of results (median, 25th percentile and 75th percentile of all samples) for aerosol ions NH4 +, NO3 , Cl, and SO4 2− measured with the WAD/SJAC, DFP, SFU and HiVol sampler during the transition period (07–31 Oct) and the onset of the wet season (01–14 Nov) at FNS during LBA-SMOCC 2002

FIG. 2 Average relative differences (assuming the WAD/SJAC is the reference) between the mean of concentrations determined from integrating samplers (DFP, SFU, and HiVol) and concentrations measured with the WAD/SJAC for the dry season (day- and nighttime), transition period and wet season at FNS during LBA-SMOCC 2002. Error bars indicate standard deviations of differences.

FIG. 2 Average relative differences (assuming the WAD/SJAC is the reference) between the mean of concentrations determined from integrating samplers (DFP, SFU, and HiVol) and concentrations measured with the WAD/SJAC for the dry season (day- and nighttime), transition period and wet season at FNS during LBA-SMOCC 2002. Error bars indicate standard deviations of differences.

TABLE 4 Correlation coefficients (r2) and reduced major axis analysis (RMA) regression results (Y = (A ± σA) + (B ± σB)*X, where σA and σB are the standard errors of intercept A and slope B, respectively) for WAD/SJAC, DFP, SFU, and HiVol samplers. Correlations for the DFP sampler refer only to concentrations determined on the Teflon filters. Results are shown for (a) the late dry (biomass burning) season (day-and nighttime listed separately); (b) the transition period and the onset of the wet season (clean conditions) at FNS during LBA-SMOCC 2002 (fields were left empty if values were smaller than the limit of detection or N < 3)

FIG. 3 Relative difference (%) (assuming the WAD/SJAC is the reference) between the concentrations of aerosol NH4 + and SO4 2− measured with SFU (polycarbonate filters) and WAD/SJAC for four days (D) and nights (N) during the dry (biomass burning) season (left Y-axis) along with the measured relative humidity (RH) (averages for respective sampling interval, right Y-axis) at FNS during LBA-SMOCC 2002.

FIG. 3 Relative difference (%) (assuming the WAD/SJAC is the reference) between the concentrations of aerosol NH4 + and SO4 2− measured with SFU (polycarbonate filters) and WAD/SJAC for four days (D) and nights (N) during the dry (biomass burning) season (left Y-axis) along with the measured relative humidity (RH) (averages for respective sampling interval, right Y-axis) at FNS during LBA-SMOCC 2002.

FIG. 4 Absolute aerosol SO4 2− difference between SFU (IC) and WAD/SJAC versus aerosol NH4 + measured with the SFU sampler at FNS during LBA-SMOCC 2002. SO2 measured with the WAD is plotted as aerosol SO4 2− equivalent possibly formed on the filter. Linear regression was done with data from all seasons (N = 20). Error bars indicate measurement uncertainty.

FIG. 4 Absolute aerosol SO4 2− difference between SFU (IC) and WAD/SJAC versus aerosol NH4 + measured with the SFU sampler at FNS during LBA-SMOCC 2002. SO2 measured with the WAD is plotted as aerosol SO4 2− equivalent possibly formed on the filter. Linear regression was done with data from all seasons (N = 20). Error bars indicate measurement uncertainty.

FIG. 5 Relative difference (%) (assuming the WAD/SJAC is the reference) between the concentrations of aerosol NO3 and Cl measured with HiVol (quartz-fiber filters) and WAD/SJAC for four days (D) and nights (N) during the dry season (left Y-axis) along with gas phase concentrations (HNO3 and HCl) (averages of respective sampling interval; measured with WAD; (right Y-axis)) at FNS during LBA-SMOCC 2002.

FIG. 5 Relative difference (%) (assuming the WAD/SJAC is the reference) between the concentrations of aerosol NO3 − and Cl− measured with HiVol (quartz-fiber filters) and WAD/SJAC for four days (D) and nights (N) during the dry season (left Y-axis) along with gas phase concentrations (HNO3 and HCl) (averages of respective sampling interval; measured with WAD; (right Y-axis)) at FNS during LBA-SMOCC 2002.

FIG. 6 Absolute aerosol SO4 2− difference between SFU (PIXE) and SJAC versus aerosol K measured by PIXE at FNS during LBA-SMOCC 2002. Error bars indicate measurement uncertainty.

FIG. 6 Absolute aerosol SO4 2− difference between SFU (PIXE) and SJAC versus aerosol K measured by PIXE at FNS during LBA-SMOCC 2002. Error bars indicate measurement uncertainty.

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