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Abstract: Dissociative electron attachment (DEA) cross sections for NH3 and CH4 are measured in a crossed beam apparatus with special care to eliminate discrimination due to kinetic energy and angular distribution of the fragment ions. The cross sections are put on absolute scale using the relative flow technique. The absolute cross sections for the formation of H− and NH2 − from ammonia and H− and CH2 − from methane are compared with available data from literature. It is seen that the present results are considerably different from what has been reported before. We also compare the cross sections of the H− channel from these molecules along with that from H2O to those from organic molecules containing alkyl, amino and hydroxyl groups to examine the extent to which the recently observed functional group dependence in the DEA contributes. [Copyright &y& Elsevier]

Numerous strategies for mitigating ammonia volatilization (AV) from agricultural land have been investigated with limited evaluation of their efficacy and response to differing field conditions across China. Therefore, this meta-analysis seeks to draw conclusions about AV in China, and assess the effect of crop type (wheat, maize, and rice as staple crops), climatic conditions, and soil properties on AV and variations in responses that can guide selection of appropriate strategies under different conditions. Novel analysis indicates nitrogen (NH 3 –N) losses of 7.62 Tg due to AV from these three crops in China. AV is 12.8 and 18.0% (95% CI) higher from maize than from wheat and rice, respectively, without N application under warm and sub-humid conditions (MM), and 13.8 and 2.8% higher under hot and humid conditions (HH). AV increases notably under HH as compared with cold and sub-arid conditions (LL) by 11.5% and 28.4% under the control treatment and application of 150 kg N ha−1, respectively in rice fields while it is most substantially under maize (52.5%) with application of 150 kg N ha−1. The ratio of change in AV between soil grades 3 and 1 (potential AV >1.0 and < 0 cmol kg−1) is significantly greater for wheat and rice (2.5%) than for maize (1.9%). The strategy of reducing N rate is more effective for maize and rice than wheat, where applying N at a rate of 150–220 kg N ha−1 to them has similar effects to applying 300 kg N ha−1 to wheat. For wheat and maize, urea should be partially substituted with organic amendments, while improved urea is the preferable N source for rice. Subsurface application has competitive efficacy, especially for maize, and higher N rates. Applying inhibitors achieves the highest AV reduction, especially with rice under various conditions, creating more actively options for future research to increase applicability. Image 1 • About 7.62 Tg N–NH 3 from main staple crops in China was indicated using CMA outputs. • Higher AV from maize fields than wheat and rice by (95% CI = 12.8 and 18%) even without N applications. • AV under maize and rice is higher under warm-humid conditions than cold-dry but wheat showed reverse response. • Improved urea and inhibitor usage is optimum strategy in reducing AV especially under rice. • Organic amendments, mulching and subsurface application are efficient strategies in reducing AV for wheat and maize. [ABSTRACT FROM AUTHOR]