Figure 2. Organic carbon (OC) content (%) in PM10 and OC enrichment ratio (ER) as a function of OC content in the soil. AG: agricultural soils for grain production; AFG: agricultural soils for forage and grain production; RRI: rural roads inside farm fields; RRO: rural roads outside farm fields. **Statistically significant (p<0.01)

The OC ER was positive in all rural soils studied (Fig. 2). Other studies also found positive OC ER in the PM10 and in the fine fractions transported by the wind (Iturri et al., 2017; Mendez et al., 2017; Webb et al., 2012). The OC ER was associated to the OC in the soil, and it was described by a negative potential function (Fig. 2). Soils with low OC contents (rural roads) showed high ERs and soils with high OC contents (agricultural soils) showed low ERs. OC content in soils of rural roads was low (Fig. 1) and most of the OC was associated to the PM10 (Fig. 2). The low OC content in soils of rural roads can be attributed to the absence of a continuous supply of labile OC (due to lack of vegetation) and high rates of wind erosion (Ramirez Haberkon et al., 2021). In rural roads, OC tends to accumulate in PM10, which represents the stable fraction of OC that is protected chemically and physically (Hassink, 1997). The stable fraction of OC is less sensitive to soil management and wind erosion (Webb et al., 2012). Vegetal coverage in agricultural soils played a crucial role in preventing the loss of labile OC through wind erosion, while also facilitating the accumulation of labile OC in the soil.

Our study revealed important findings regarding the OC content in PM10 emitted by agricultural soils and rural roads. This study provides the first report on the OC content in the PM10 emitted by rural roads in the region. The OC content in the PM10 was consistently higher than that in the soil across all soils analyzed, indicating an enrichment of OC in the PM10. This finding aligns with previous studies demonstrating the accumulation of OC in fine particles.

This study reveals an association between organic carbon (OC) content in PM10 and OC content in the soil. An association between OC ER and OC content in the soil was also found. Both associations indicate that OC accumulates in PM10 until it reaches a maximum (Saturation), which was found to be 3.5% for the analyzed soils. These findings enhance our understanding of the dynamics of OC in PM10 and its association with the OC content in the soil. Our study highlights the importance of considering the OC content in the PM10 emitted by rural soils for quantifying OC losses from the soil and OC discharges into the atmosphere through dust emissions. Further investigations should examine the OC content in PM10 emitted by rural soils across diverse soil textures and geographical regions.