1.College of Tropical Crops, Hainan University;2.State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Changshu National Agro-Ecosystem Observation and Research Station
The National Natural Science Foundation of China
【Objective】Atmospheric ammonia (NH3) is an important precursor for the formation of PM2.5. Hence, identification and quantification of the sources of atmospheric NH3 are important for NH3 emission abatement and air pollution control. Farmland NH3 volatilization is one of the important sources of atmospheric NH3. The technology of natural abundance of nitrogen isotopes (δ15N) has been used to trace NH3 sources in recent years. Despite these advances, studies on the dynamic change of δ15N values from the whole process of NH3 volatilization from farmland soils are lacking. Moreover, NH3 volatilization from farmland soils is affected by different factors such as soil properties, pH, which can directly or indirectly influence the δ15N values of volatilized NH3 and may lead to uncertainties in sources traceability. Upland soil NH3 volatilization dominates total farmland NH3 volatilization in China. We selected four types of upland soil from different regions in China to study the δ15N values of NH3 volatilization from the whole volatilization process to clarify the changes of δ15N-NH3 values and their impacting factors.【Method】Urea was applied to four types of soils from Liaoning, Hebei, Henan and Tibet, and NH3 volatilization was studied in a 15-day indoor culture experiment by the sponge absorption method under controllable conditions. The δ15N value during the whole process of NH3 volatilization was measured by the chemical transformation method.【Result】Results showed that the values of δ15N during NH3 volatilization from Beipiao soil from Liaoning Province ranged from -26.14‰ to -5.57‰, with an average of -21.74±1.89‰. The variation range of δ15N values of Xinxiang soil (from Henan province) was from -31.92‰ to -26.31‰, with an average value of -29.31±1.72‰ while that of Tangshan soil (from Hebei province) and Linzhi soil (from Tibet) ranged from -24.41‰ to -3.11‰ with an average of 19.82±2.04‰, and from -29.17‰ to -2.20‰ with an average of -23.25±2.16‰, respectively. Overall, the δ15N values of the NH3 volatilization process in upland soils from different regions are different. During the whole process of soil NH3 volatilization, the δ15N-NH3 values of Xinxiang continued to increase, and the δ15N-NH3 values of Beipiao, Tangshan and Linzhi first decreased and then increased. Soil properties and NH3 volatilization rate are the main factors affecting the δ15N value.【Conclusion】Our results showed that soil pH, NH3 volatilization rate and cumulative NH3 loss were significantly negatively correlated with the δ15N-NH3 values. In addition, isotope fractionation also impacts the δ15N-NH3 values. The results of this study can provide better support for the quantitative traceability of atmospheric NH3.
LI Miao, TI Chaopu, PENG Lingyun, TAO Limin, BAI Xiao, LI Chenglin, MENG Lei, YAN Xiaoyuan. Changes of δ15N Values during Ammonia Volatilization from Different Upland Soils in China[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202110190563,[In Press]