Process of heavy metal transport between soil and the atmosphere: a review

The transport of heavy metals (HMs) (excluding Hg) between soil and the atmosphere significantly influences human production and life. This review systematically summarizes the processes involved in the wind erosion-driven transport of HMs from soil to the atmosphere and the partitioning of atmospheric HMs via atmospheric deposition, drawing on relevant literature analysis and synthesis. The results reveal that both soil and the atmosphere are sinks of HMs, influencing each other significantly. The transport of soil HMs to the atmosphere along with soil fugitive dust by wind force incorporates three pathways: the direct suspension of suspension-size aggregates, the collision and abrasion of creep-size and saltation-size aggregates, and the breakage or decomposition of creep-size aggregates. Conventional farming practices, elevated HM concentrations, and high wind speeds exacerbate soil HM emissions. However, the effects of soil organic matter (SOM) and clay on soil HM emission demonstrate dual characteristics. Atmospheric deposition has emerged as a significant source of soil HMs, with wet deposition predominating, except in arid and semiarid regions. Dry deposition is influenced by meteorological parameters and topographic profiles, whereas preceding weather and precipitation duration are other factors affecting for wet deposition. This process increases the exposure possibility and consequent exposure dosage of HMs to humans and crops, thereby amplifying the potential risks of HMs. Moreover, the capacity of atmospheric HMs for long-range wind-driven dispersal may leave remote and sensitive ecosystems that are increasingly vulnerable. Moreover, it concludes with a synthesis of the current challenges and discusses recommendations for future directions. Therefore, this review will have significant reference and guiding value for research in this field and is intended for researchers engaged in the migration of HMs in soil and atmosphere, the safe utilization of heavy metal contaminated soil, and regional background values of soil HMs.