Abstract Soil methanol (CH3OH) exchange is often considered as several orders of magnitude smaller than plant methanol exchange. However, for some ecosystems, it is significant in regard with plant exchange and worth thus better consideration. Our study sought to gain a better understanding of soil exchange. Methanol flux was measured at the ecosystem scale on a bare agricultural soil over two contrasted periods using the disjunct eddy covariance by mass scanning technique. A proton-transfer-reaction mass spectrometer was used for the methanol ambient mixing ratio measurements. Bi-directional exchange dynamics were observed. Methanol emission occurred under dry and warm conditions and correlated best with soil surface temperature, whereas methanol uptake occurred under wet and mild conditions and correlated well with the methanol ambient concentration. After having tested a physical adsorption-desorption model and by confronting our data with the literature, we propose that the exchange was ruled by both a physical adsorption/desorption mechanism and by a methanol source, which still needs to be identified. The soil emission decreased when the vegetation developed. The reasons for the decrease still need to be determined. Overall, the dynamics observed at our site were similar to those reported by other studies for both cropland and forest ecosystems. The mechanism proposed in our work can thus be possibly applied to other sites or ecosystems. In addition, the methanol exchange rate was in the upper range of the exchange rates reported by other soil studies, suggesting that cropland soils are more important methanol exchangers than those in other ecosystems and should therefore be further investigated.

中文翻译：

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温带农田土壤与大气之间的甲醇交换动态

摘要 土壤甲醇（CH3OH）交换通常被认为比植物甲醇交换小几个数量级。然而，对于某些生态系统，它在植物交换方面具有重要意义，因此值得更好地考虑。我们的研究旨在更好地了解土壤交换。通过质量扫描技术使用分离涡流协方差在两个对比时期内在裸露农业土壤的生态系统尺度上测量甲醇通量。质子转移反应质谱仪用于甲醇环境混合比测量。观察到双向交换动态。甲醇排放发生在干燥和温暖的条件下，与土壤表面温度相关性最好，而甲醇吸收发生在潮湿和温和的条件下，并且与甲醇环境浓度密切相关。在测试了物理吸附-解吸模型并将我们的数据与文献对照后，我们提出交换受物理吸附/解吸机制和甲醇源的支配，这仍然需要确定。随着植被的发育，土壤排放量减少。减少的原因仍有待确定。总体而言，在我们的站点观察到的动态与其他研究报告的农田和森林生态系统的动态相似。因此，我们工作中提出的机制可能适用于其他地点或生态系统。此外，甲醇汇率在其他土壤研究报告的汇率范围内，