Effect of Straw Return on Hydroxyl Radical Formation in Paddy Soil
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Effect of Straw Return on Hydroxyl Radical Formation in Paddy Soil Shaochong Liu1 · Dixiang Wang1 · Changyin Zhu1 · Dongmei Zhou1 Received: 8 June 2020 / Accepted: 13 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Straw return, as an important agricultural management measure, is receiving growing attention. Hydroxyl radical (•OH) can be produced when subsurface soil interacts with oxygen, but the effects of straw incorporation on •OH formation have rarely been evaluated. In this study, we found that straw return had a significant effect on soil properties. Soil pH and redox potential (Eh) decreased while electronic conductivity (EC) showed an increment. Dissolved organic carbon content of soil initially increased and then decreased to the same level as the control by the end of the experiment of 120 days. Moreover, Fe(II) formation was promoted by straw return under anaerobic conditions. •OH was produced in the flooded paddy soil when exposed to oxygen, which correlated well with Fe(II) content. The effect of rape (Brassica campestris L.) straw on •OH formation rate was more evident as compared to wheat (Triticum aestivum L.) straw, suggesting a potentially more profound influence of rape straw return on pollutant transformation in paddy soils. Keywords Straw return · Soil · Hydroxyl radical · Dissolved organic matter · Fe
Introduction China is one of the world’s largest grain producers which produces a large amount of crop straw. The annual yield in 2015 was 1.04 billion tones (Han et al. 2002; Li et al. 2017), accounting for nearly one-third of the global production. Crop straw has a long history of being used as heating sources, fuel, building materials and livestock feed in China (Zhao et al. 2015). Straw burning has been regarded as the easiest and fastest approach to dispose agricultural waste (Yu et al. 2016), especially in the eastern and southern areas in China where over 30% post-harvest crop straw was burnt in fields (Wang and Zhang 2008). However, direct burning of crop straw emits various types of pollutants such as particulate matter, polycyclic aromatic hydrocarbons (PAHs), and many other gaseous pollutants (Li et al. 2007; Lu and Zhang 2010; Subramanian 2014; Zhang et al. 2011), which can cause severe air pollution and do harm to human * Changyin Zhu [email protected] * Dongmei Zhou [email protected] 1
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, People’s Republic of China
health (Chen et al. 2017; Zhou et al. 2017). After decades of research and development, straw utilization techniques are becoming more practical and economical. Recently, straw returning to the field as a green and environmentallyfriendly straw treatment method is encouraged in China. As one of the main carbon sources, crop straw contains abundant organic matters, phosphorous, nitrogen, potassium and many other trace elements, which is considered to be desirable fertilizer for crop growth and thus can
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