## 4 Discussion
### Field Trials  
Field experiments are subject to interferences that need to be considered when interpreting and comparing the effectiveness of dust suppressants. The test site is located close to an open-pit mine and to other sources of PM (e.g., unpaved roads), which could have led to dust deposition between measurements. However, it can be expected that such an additional dust input would have impacted all soil plots in a similar manner. Observed physical impairments of soil plot surfaces caused by wildlife may also be a potential source of error (Figure 7b). Disturbances affect the erodibility of soil surfaces and thus the generation of dust emissions [36; 37]. Consequently, results should be interpreted cautiously as to which amendments were most effective in suppressing dust emissions. Conducted field trials demonstrate that investigated food processing by-products can significantly reduce wind erosion and dust emissions (PM\({}_{2.5}\), PM\({}_{10}\), and TSP) from coarse mine soils (Figure 6). The observed decrease in dust emissions is likely attributed to carbohydrates and proteins contained in the tested amendments, which agglomerate soil particles through adhesive and cohesion forces. The aforementioned carbohydrates and proteins likely bind to soil particles upon evaporation of applied solutions. The resulting improvement in inter-particle bonding enhances the soil's mechanical properties, creating a surface with a higher erosion threshold [16]. Field trial data also demonstrate that dust emissions from soil plots treated with food processing by-products progressively increased with time. Such a decrease in dust suppression effectiveness probably resulted from reactions at the soil surface, which weakened the bonding between soil particles and thus reduced the resistance to wind erosion. It is assumed that rainfall during the study period (Table A1, Appendix A) resulted in the leaching of the amendments from the soils since they are water-soluble. However, visual inspections of the treated soil plots show intact surfaces unlike that of the untreated soil (Figure 7). Hence, natural rainfall did not impact on the integrity of treated soil surfaces, allowing amendments to bind surficial soil particles and prevent their erosion. By contrast to the treated soil plots, dust emissions from the untreated mine soil and mine soil treated only with water constantly decreased with time (Figure 6). These trends can be explained by the observed changes in surface textures (Figure 7a,b) and the experimental setup. Near-surface wind velocity is crucial for the dynamics of wind erosion [38]. Soil particles are detached and transported when the aerodynamic drag and lift forces exceed the gravitational and inter-particle forces [39]. Moreover, dust particles are entrained by the impact of saltating sand grains [29]. During the study period, erosion of the control group plots formed conical-shaped depressions and changes in horizontal soil thickness (Figure 7a). In parallel, the position and orientation of the electric blower did not change. Hence, it is assumed that the wind velocity at the soil surface decreased over time, which reduced the forces available to erode soil and consequently dust emissions from water-treated and untreated soil plots. At the end of the field trial (i.e., after 28 days), the lowest dust concentrations in air were measured for all soil plots, including the control group. From the meteorological data (Table A1, Appendix A), it can be concluded that previous rainfall (i.e., 27.7 L/m\({}^{2}\) between days 25-27) significantly increased the moisture content of the soil. Soil moisture directly contributes to soil cohesion and substantially affects the resistance to wind erosion [21]. It is generally recognized that an increase in inter-particle forces is induced by the absorbed water film and capillary forces [26]. However, [PERSON] et al.