## 3 Results
The saltation mass in velocity 0.52 m/s was about 60% higher in relation to velocity 0.43 m/s. In measuring the material smaller than 63 \(\upmu\)m in the saltation mass (Table 2), it was found that there is no distinct trend showing the material variability according to the shear velocity. The percentage of matter less than 63 \(\upmu\)m at 0.52 was 17.5% while the percentage at 0.31 was 12.3%. In sample 500-1000 \(\upmu\)m the highest value was recorded in 0.52 m/s (5.5 g) while the saltation started only from 0.39 m/s. In most velocities, no material less than 63 \(\upmu\)m was found in the saltation mass (Table 2). As the velocity increases, the macroaggregates move and break so that only at the last velocity 8.4% of the material in the saltation mass was smaller than 63 \(\upmu\)m (Table 2). The results of the PM10 concentrations that were measured during the experiment are shown in Figure 4. The range of the values differs according to the aggregate size so that the highest PM10 concentration was recorded in the smallest fraction (63-250 \(\upmu\)m) and the lowest one was at the largest fraction (500-1000 \(\upmu\)m). In sample 63-250 \(\upmu\)m, the lowest dust concentration was 0.2 mg/m\({}^{3}\) and the highest concentration was about 170 time more (35.2 mg/m\({}^{3}\)). A moderate increase in concentration occurs when the wind velocity increases accordingly. The concentration peak (26.5 mg/m\({}^{3}\)) was recorded at shear velocity 0.52 m/s with more than 100% increase relative to velocity 0.43. In sample 250-500 \(\upmu\)m, the lowest concentration was 0.1 mg/m\({}^{3}\) and the highest concentration was about 250 time \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**u\({}^{*}\) (m/s)**} & **Sample 63–250 \(\upmu\)m** & **Sample 250–500 \(\upmu\)m** & **Sample 500–1000 \(\upmu\)m** \\ \cline{2-4}  & **\textless{63 }\(\upmu\) (\%)** & **\textless{63 }\(\upmu\) (\%)** & **\textless{63 }\(\upmu\) (\%)** \\ \hline
0.24 & 30.5 & N/A & N/A \\ \hline
0.31 & 30.3 & 12.3 & N/A \\ \hline
0.36 & 24.5 & 24.9 & N/A \\ \hline
0.39 & 16.5 & 13.7 & N/A \\ \hline
0.43 & 20.5 & 18.1 & 6.6 \\ \hline
0.52 & 11.8 & 17.5 & 8.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Percentage of dust-sized aggregates and particle (\(<\)63 \(\upmu\)m) in the saltation mass (Figure 3) under each shear velocity. Figure 3: Saltation mass measured in the reference samples under various shear velocities. The average mass is presented by the solid line inside the minimum/maximum box, and standard deviations are in dashed lines. Note the differences in the value rang of Y axis. more (25.1 mg/m\({}^{3}\)). In 250-500 \(\upmu\)m sample, there was a significant increase in PM10 concentration at 0.43 m/s. This PM10 value was even higher than that of 0.52 m/s although not significant. It is reasonable to assume that a vast amount of dust particles was released at 0.43 m/s, and thus the dust supply from aggregates was more limited under 0.52 m/s. In sample 500-1000 \(\upmu\)m, a distinct PM10 concentration was obtained only from 0.39 m/s, which is the same threshold of saltation (Figure 3). A positive nonlinear correlation was found between the calculated PM10 flux and the saltation flux (Figure 5) for all soil samples (R\({}^{2}\) = 0.86-0.88).