College of Biology and the Environment, Nanjing Forestry University
The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) （No. 41701264）；Youth Innovation Fund of Nanjing Forestry University (No. CX2017023)
稳定同位素技术是研究土壤元素循环的重要技术手段。本实验研究了同位素标记后的停留时间对水稻地上和地下部分及利用其制备的生物质炭的13C丰度（δ13C）和15N丰度（δ15N）的影响，为深入研究生物质炭对土壤碳、氮过程的影响提供基础。研究以水稻为材料，利用15N-尿素叶面喷施和13C-CO2脉冲标记的方法对水稻进行了15N和13C双标记，15N标记结束后设置4 h、6 h和24 h三个停留时间，将标记后的水稻分为地上和地下部分，分别在300 °C和500 °C下制备成生物质炭，利用同位素质谱仪测定水稻及其生物质炭的δ13C和δ15N。结果表明，随着停留时间的延长，水稻地上部分的δ13C由872‰逐渐降低至578‰，而地下部分的δ13C由226‰逐渐升高至869‰。与δ13C不同，水稻地上部分δ15N呈现先增加后降低的趋势，停留时间6 h时δ15N最大（1764‰），而地下部分的δ15N呈现先降低后增加的趋势。整体而言，与水稻原料相比，生物质炭的δ13C和δ15N分别降低了52.1%和15.9%。而且，生物质炭的δ13C和δ15N均在停留时间为24 h时最高，300 °C生物质炭表现的更加明显。随着停留时间的延长，300 °C生物质炭的热水可提取有机碳的δ13C比残留固体的δ13C降低的比例由4.14%提高到11.0%，而对于500 °C生物质炭则由32.3%降低到18.9%，表明延长停留时间分别降低和提高了300 °C和500 °C生物质炭的13C均匀性。综上所述，本研究发现标记后的停留时间对水稻δ13C和δ15N的影响不同，并且这种影响没有延续至生物质炭，停留时间和制备温度共同影响水稻生物质炭的13C均匀性。
【Objective】To provide a basis for an advanced on the impacts of biochar on soil carbon and nitrogen cycling, the effects of residence time after isotope labeling on the δ13C and δ15N values of rice aboveground and underground tissues and biochars derived from these two tissues were studied. 【Method】Rice plants were labeled with 13C and 15N by pulse labeling of 13C-CO2 and foliar fertilization of 15N-urea, respectively. The residence time of 4 h, 6 h and 24 h was set after 15N isotope labeling. The labeled rice plants were divided into aboveground and underground tissues and four biochars were produced by pyrolyzing these two tissues at 300 ℃ and 500 ℃, respectively. The δ13C and δ15N values of rice tissues and their biochars were determined by isotope mass spectrometry. 【Result】With the increase in residence time, δ13C values of the aboveground tissues of rice plants gradually decreased from 872‰ to 578‰, while the δ13C values of the underground tissues gradually increased from 226‰ to 869‰. Unlike with the δ13C, the δ15N values in the aboveground tissues of rice plants first increased then decreased, and the maximum (1764‰) occurred at the residence time of 6 h, while δ15N values in the underground tissues first decreased and then increased. Overall, compared to rice tissues, the δ13C and δ15N values of the biochars decreased by 52.1% and 15.9%, respectively. Moreover, both the δ13C and δ15N values of the biochars were highest at the residence time of 24 h, especially for the 300 °C biochar. With the increase in residence time, the reduced proportion of the δ13C of hot water extractable dissolved organic carbon when compared with that of the residual solid increased from 4.14% to 11.0% for the 300 °C biochar, while it decreased from 32.3% to 18.9% for the 500 °C biochar. This indicates that increase in the residence time decreased and increased the uniformity of 13C of the 300 °C and 500 °C biochars, respectively. 【Conclusion】Our results demonstrate that the effects of residence time after labelling on δ13C and δ15N values of the rice plants were different, and the biochars did not retain the isotopic signature of the raw rice tissues. Residence time and pyrolysis temperature together affected the uniformity of 13C in rice biochars.
Zhang Fangchao, Lu Weiwei, Zha Quanzhi. Effects of residence time on 13C and 15N abundances of rice and rice derived-biochars after a dual isotope labeling[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202203250133,[In Press]