Microplastics are released from agricultural soils to the atmosphere by wind erosion&amp;#160;

Sajjad Abbasi,Coen Ritsema,Patryk Oleszczuk,Mahrooz Rezaei,Haniye Pourmahmood,Andrew Turner

doi:10.5194/egusphere-egu23-14969

Abstract

&lt;p&gt;Agricultural soils are a secondary source of airborne microplastics (MP) through wind-driven erosion, especially in arid and semi-arid regions. However, this transport pathway has thus far received little scientific attention. In this study, we measured microplastics in both soil and wind-eroded sediment using a portable wind tunnel in two vegetable-growing fields of Fars province, Iran that have been subject to different agricultural practices: plastic mulch (Field 1) and irrigation with wastewater (Field 2).&lt;/p&gt;&lt;p&gt;Microplastic concentration in soil ranged from 0.04 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; to 0.83 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; in Field 1 and from 0.20 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; to about 1.1 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; in Field 2. Fibres represented the dominant shape of MPs, but spherules, presumably from wastewater, also made a significant contribution to MPs in Field 2. Analysis of samples by Raman spectroscopy and scanning electron microscopy (SEM) revealed that polyethylene terephthalate (PET) and nylon were the most abundant polymers and that MPs exhibited varying degrees of weathering. Concentrations of MPs in this study are within the range reported previously for agricultural soils.&lt;/p&gt;&lt;p&gt;Results of the wind tunnel revealed threshold velocities for wind erosion of 7 and 12 m s&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; and MP erosion rates of 0.4 and 1.1 MP m&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;2&lt;/sup&gt; s&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; for Fields 1 and 2, respectively. MP concentrations in wind-eroded sediment were considerably higher than the agricultural soil samples and were significantly higher (&lt;em&gt;p &lt; &lt;/em&gt;0.05) in Field 2 (mean and median of 45.26 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; and 42.89 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;, respectively) than in Field 1 (mean and median of 9.08 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; and 11.35 MP g&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;, respectively). This revealed enrichment of MP in wind-eroded sediment compared to the original soil. Erosion rates are significantly higher than published depositional rates of MPs and suggest that agricultural soils act as both a temporary sink and dynamic secondary source of MPs that should be considered in atmospheric transport models and risk assessments.&lt;/p&gt;

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