# Aggregate and Particle Size Distribution of the Soil Sediment
## 5 Conclusions  
During our research, it was found that the method that uses the rainfall simulators where the eroded sediment is collected and then analyzed by laser diffraction to obtain the particle size distribution data is a suitable method to evaluate the impact of the external factors to the particle size distribution of the eroded soil sediment.  
The main advantages of the laser diffractometer Mastersizer 3000 compared to the hydrometer and the PARIO are the very short evaluating time of 15 min per sample, the small amount of required sample at 1 g, and its ability to comfortably and relevantly analyze soil samples both with and without soil aggregates.  
When the soil is fully saturated and the erosion fills are made, the samples contained coarser particles than the samples eroded during the sheet flow. Also, in general, the eroded particles had become finer throughout the experiments.  
Generally, when the erosion processes were intensive (steep slope or long duration of the raining), the eroded sediment contained coarser particles and lower amounts of the aggregates.  
For further research, it would be interesting to study aggregates content on more samples obtained from plots with different soil types or with different rainfall intensities, and also to analyze PSD results in the context of volume of the surface runoff and the formation of the rills.  
Conceptualization, R.K. and P.K.; Data curation, M.N. and P.K.; Formal analysis, R.K.; Investigation, R.K.; Methodology, R.K., M.N. and P.K.; Software, M.N.; Supervision, P.K.; Writing--original draft, R.K.; Writing--review & editing, M.N. and P.K. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the TH02030428--\"Design of technical measures for slopes stabilization and soil erosion prevention\". And by the international CTU grant SGS20/156/OHK1/3T/11.  
The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of CTU in Prague.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The data that support the findings of this study are available on request from the corresponding author.  
The authors declare no conflict of interest and the funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.  
Figure A1: LD method. Boxplot representation of PSD of all 156 collected samples with and without soil aggregates.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**D1**} & **W1** & **D2** & **W2** \\ \hline \(<\)2 \(\mu\)m & 12.8 & 12.8 & 13.0 & 14.3 \\ \(<\)10 \(\mu\)m & 27.2 & 28.2 & 28.4 & 29.8 \\ \(<\)50 \(\mu\)m & 40.8 & 39.6 & 38.5 & 43.3 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Aggregate representation percentage in the sediment depending on initial condition, slope, 22\({}^{\circ}\) [%].  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**with Aggregates**} & \multicolumn{3}{c}{**without Aggregates**} \\  & & **D1** & **W1** & **D2** & **W2** & **D1** & **W1** & **D2** & **W2** \\ \hline \multirow{3}{*}{Median \(\pm\) SD} & \(<\)2 \(\mu\)m & 4.8 \(\pm\) 1.6 & 3.6 \(\pm\) 1.8 & 4.9 \(\pm\) 2.1 & 3.6 \(\pm\) 1.4 & 20.1 \(\pm\) 4.3 & 16.6 \(\pm\) 5.6 & 17.5 \(\pm\) 4.6 & 16.4 \(\pm\) 5.2 \\ \cline{2-8}  & \(<\)10 \(\mu\)m & 21.9 \(\pm\) 3.3 & 20.0 \(\pm\) 4.6 & 22.1 \(\pm\) 4.9 & 20.2 \(\pm\) 3.8 & 52.0 \(\pm\) 3.0 & 48.4 \(\pm\) 4.3 & 48.9 \(\pm\) 3.3 & 48.0 \(\pm\) 3.7 \\ \cline{2-8}  & \(<\)50 \(\mu\)m & 50.0 \(\pm\) 4.9 & 50.6 \(\pm\) 8.7 & 51.8 \(\pm\) 6.4 & 50.0 \(\pm\) 5.5 & 91.5 \(\pm\) 1.4 & 90.6 \(\pm\) 1.8 & 90.8 \(\pm\) 1.2 & 90.5 \(\pm\) 1.8 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Statistical analysis of influence of initial conditions to the particle size distribution (obtained by LD) [%] (average of all three slopes).